Subject: Re: [Roll] [roll] security-framework #77 (closed): Comments during Security FW Last Call

From: "roll issue tracker" <[email-masked]>
Date: Tue, 12 Oct 2010 12:22:45 -0000

#77: Comments during Security FW Last Call

Changes (by jpv@…):

  * status:  new => closed
  * resolution:  => fixed

Old description:

> Hi,
>
> Please find below some detailed comments - Overall well-written document.
> In addition to the comments in-line (search for JP>), I would welcome a
> few
> diagrams especially when you describe the different types of attacks.
> Furthermore,
> as you will see in the comments, be careful not to make the assumption of
> wireles
> links (there are many LLNs with wireless links of course) but this is not
> the only
> type of links. Same comment for the node type (they are not all battery
> operated).
> Thanks ! I will open a ticket capturing all of the comments below.
>
>  JP>
>
> Starting with ID nits:
>
> Checking references for intended status: Informational
> ----------------------------------------------------------------------------
>
>   == Outdated reference: draft-ietf-roll-building-routing-reqs has been
>      published as RFC 5867
>
>   == Outdated reference: draft-ietf-roll-home-routing-reqs has been
> published
>      as RFC 5826
>
>   == Outdated reference: A later version (-11) exists of
>      draft-ietf-roll-rpl-07
>
> Networking Working Group                                    T. Tsao, Ed.
> Internet-Draft                                         R. Alexander, Ed.
> Intended status: Informational                               Eka Systems
> Expires: October 1, 2010                                  M. Dohler, Ed.
>                                                                     CTTC
>                                                             V. Daza, Ed.
>                                                           A. Lozano, Ed.
>                                                 Universitat Pompeu Fabra
>                                                           March 30, 2010
>

>    A Security Framework for Routing over Low Power and Lossy Networks
>                  draft-ietf-roll-security-framework-00
>
> Abstract
>
>    This document presents a security framework for routing over low
>    power and lossy networks.
> JP> Add acronym (LLN)
> The development builds upon previous work
>    on routing security and adapts the assessments to the issues and
>    constraints specific to low power and lossy networks.  A systematic
>    approach is used in defining and evaluating the security threats and
>    identifying applicable countermeasures.  These assessments provide
>    the basis of the security recommendations for incorporation into low
>    power, lossy network routing protocols.  As an illustration, this
>    framework is applied to RPL.
> JP> Expand acronym when first used (LLN here).
>
> Requirements Language
>
>    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
>    "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
>    "OPTIONAL" in this document are to be interpreted as described in RFC
>    2119 [RFC2119].
>
> Status of this Memo
>
>    This Internet-Draft is submitted to IETF in full conformance with the
>    provisions of BCP 78 and BCP 79.
>
>    Internet-Drafts are working documents of the Internet Engineering
>    Task Force (IETF), its areas, and its working groups.  Note that
>    other groups may also distribute working documents as Internet-
>    Drafts.
>
>    Internet-Drafts are draft documents valid for a maximum of six months
>    and may be updated, replaced, or obsoleted by other documents at any
>    time.  It is inappropriate to use Internet-Drafts as reference
>    material or to cite them other than as "work in progress."
>

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>    The list of current Internet-Drafts can be accessed at
>    http://www.ietf.org/ietf/1id-abstracts.txt.
>
>    The list of Internet-Draft Shadow Directories can be accessed at
>    http://www.ietf.org/shadow.html.
>
>    This Internet-Draft will expire on October 1, 2010.
>
> Copyright Notice
>
>    Copyright (c) 2010 IETF Trust and the persons identified as the
>    document authors.  All rights reserved.
>
>    This document is subject to BCP 78 and the IETF Trust's Legal
>    Provisions Relating to IETF Documents
>    (http://trustee.ietf.org/license-info) in effect on the date of
>    publication of this document.  Please review these documents
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>    to this document.  Code Components extracted from this document must
>    include Simplified BSD License text as described in Section 4.e of
>    the Trust Legal Provisions and are provided without warranty as
>    described in the BSD License.
>

>
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> Table of Contents
>
>    1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
>    2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
>    3.  Considerations on ROLL Security  . . . . . . . . . . . . . . .  5
>      3.1.  Routing Assets and Points of Access  . . . . . . . . . . .  6
>      3.2.  The CIA Security Reference Model . . . . . . . . . . . . .  8
>      3.3.  Issues Specific to or Amplified in LLNs  . . . . . . . . .  9
>      3.4.  ROLL Security Objectives . . . . . . . . . . . . . . . . . 11
>    4.  Threats and Attacks  . . . . . . . . . . . . . . . . . . . . . 12
>      4.1.  Threats and Attacks on Confidentiality . . . . . . . . . . 12
>        4.1.1.  Routing Exchange Exposure  . . . . . . . . . . . . . . 12
>        4.1.2.  Routing Information (Routes and Network Topology)
>                Exposure . . . . . . . . . . . . . . . . . . . . . . . 13
>      4.2.  Threats and Attacks on Integrity . . . . . . . . . . . . . 13
>        4.2.1.  Routing Information Manipulation . . . . . . . . . . . 14
>        4.2.2.  Node Identity Misappropriation . . . . . . . . . . . . 14
>      4.3.  Threats and Attacks on Availability  . . . . . . . . . . . 15
>        4.3.1.  Routing Exchange Interference or Disruption  . . . . . 15
>        4.3.2.  Network Traffic Forwarding Disruption  . . . . . . . . 15
>        4.3.3.  Communications Resource Disruption . . . . . . . . . . 15
>        4.3.4.  Node Resource Exhaustion . . . . . . . . . . . . . . . 16
>    5.  Countermeasures  . . . . . . . . . . . . . . . . . . . . . . . 16
>      5.1.  Confidentiality Attack Countermeasures . . . . . . . . . . 17
>        5.1.1.  Countering Deliberate Exposure Attacks . . . . . . . . 17
>        5.1.2.  Countering Sniffing Attacks  . . . . . . . . . . . . . 17
>        5.1.3.  Countering Traffic Analysis  . . . . . . . . . . . . . 19
>        5.1.4.  Countering Physical Device Compromise  . . . . . . . . 19
>        5.1.5.  Countering Remote Device Access Attacks  . . . . . . . 21
>      5.2.  Integrity Attack Countermeasures . . . . . . . . . . . . . 21
>        5.2.1.  Countering Tampering Attacks . . . . . . . . . . . . . 22
>        5.2.2.  Countering Overclaiming and Misclaiming Attacks  . . . 22
>        5.2.3.  Countering Identity (including Sybil) Attacks  . . . . 22
>        5.2.4.  Countering Routing Information Replay Attacks  . . . . 23
>        5.2.5.  Countering Byzantine Routing Information Attacks . . . 23
>      5.3.  Availability Attack Countermeasures  . . . . . . . . . . . 24
>        5.3.1.  Countering HELLO Flood Attacks and ACK Spoofing
>                Attacks  . . . . . . . . . . . . . . . . . . . . . . . 24
>        5.3.2.  Countering Overload Attacks  . . . . . . . . . . . . . 26
>        5.3.3.  Countering Selective Forwarding Attacks  . . . . . . . 27
>        5.3.4.  Countering Sinkhole Attacks  . . . . . . . . . . . . . 27
>        5.3.5.  Countering Wormhole Attacks  . . . . . . . . . . . . . 28
>    6.  ROLL Security Features . . . . . . . . . . . . . . . . . . . . 28
>      6.1.  Confidentiality Features . . . . . . . . . . . . . . . . . 29
>      6.2.  Integrity Features . . . . . . . . . . . . . . . . . . . . 30
>      6.3.  Availability Features  . . . . . . . . . . . . . . . . . . 31
>      6.4.  Additional Related Features  . . . . . . . . . . . . . . . 31
>      6.5.  Consideration on Matching Application Domain Needs . . . . 31
>

>
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>        6.5.1.  Security Architecture  . . . . . . . . . . . . . . . . 32
>        6.5.2.  Mechanisms and Operations  . . . . . . . . . . . . . . 34
>    7.  Application of ROLL Security Framework to RPL  . . . . . . . . 36
>    8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 38
>    9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 38
>    10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 38
>    11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
>      11.1. Normative References . . . . . . . . . . . . . . . . . . . 38
>      11.2. Informative References . . . . . . . . . . . . . . . . . . 39
>    Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40
>

>
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> 1.  Terminology
>
>    This document conforms to the terminology defined in
>    [I-D.ietf-roll-terminology].
>
> JP> There are other terms used in the document that could be added here
> (see below).
>

>
> 2.  Introduction
>
>    In recent times, networked wireless devices have found an increasing
>    number of applications in various fields.  Yet, for reasons ranging
>    from operational application to economics, these wireless devices
> JP> This does not apply only to wireless links (e.g. PLC)
> are
>    often supplied with minimum physical resources, e.g., limited power
>    reserve, slow speed or low capability computation, or small memory
>    size.  As a consequence, the resulting networks are more prone to
>    loss of traffic and other vulnerabilities.  The proliferation of
>    these low power and lossy networks (LLNs), however, are drawing
>    efforts to examine and address their potential networking challenges.
>
>    This document presents a framework for securing routing over low
>    power and lossy networks (ROLL)
> JP> s/ROLL/LLN
>  through an analysis that starts from
>    the routing basics.  The objective is two-fold.  First, the framework
>    will be used to identify pertinent security issues.  Second, it will
>    facilitate both the assessment of a protocol's security threats and
>    the identification of the necessary features for development of
>    secure protocols for ROLL.
> JP> s/ROLL/The ROLL Working Group.
>
>    The approach adopted in this effort proceeds in four steps, to
>    examine ROLL security issues, to analyze threats and attacks, to
>    consider the countermeasures, and then to make recommendations for
>    securing ROLL.
> JP> Could you just replace "ROLL" by the "the routing protocol developed
> by the ROLL Working Group" or Define ROLL as Routing Over Low power
> and Lossy networks.
>   The basis is found on identifying the assets and
>    points of access of routing and evaluating their security needs based
>    on the Confidentiality, Integrity, and Availability (CIA) model in
>    the context of LLN.  The utility of this framework is demonstrated
>    with an application to RPL [I-D.ietf-roll-rpl].
>

> 3.  Considerations on ROLL Security
>
>    This section sets the stage for the development of the framework by
>    applying the systematic approach proposed in [Myagmar2005] to the
>    routing security problem, while also drawing references from other
>    reviews and assessments found in the literature, particularly,
>    [RFC4593] and [Karlof2003].  The subsequent subsections begin with a
>    focus on the elements of a generic routing process that is used to
>    establish routing assets and points of access of the routing
>    functionality.  Next, the CIA security model is briefly described.
>    Then, consideration is given to issues specific to or amplified in
>    LLNs.  This section concludes with the formulation of a set of
>

>
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>    security objectives for ROLL.
>
> 3.1.  Routing Assets and Points of Access
>
>    An asset implies important system component (including information,
>    process, or physical resource), the access to, corruption or loss of
>    which adversely affects the system.  In network routing, assets lie
>    in the routing information, routing process, and node's physical
>    resources.  That is, the access to, corruption, or loss of these
>    elements adversely affects system routing.  In network routing, a
>    point of access refers to the point of entry facilitating
>    communication with or other interaction with a system component in
>    order to use system resources to either manipulate information or
>    gain knowledge of the information contained within the system.
>    Security of the routing protocol must be focused on the assets of the
>    routing nodes and the points of access of the information exchanges
>    and information storage that may permit routing compromise.  The
>    identification of routing assets and points of access hence provides
>    a basis for the identification of associated threats and attacks.
>
>    This subsection identifies assets and points of access of a generic
>    routing process with a level-0
> JP> Explain what you mean by "level-0"
> data flow diagram.  The use of the
>    data flow diagram allows for a clear, concise model of the routing
>    functionality; it also has the benefit of showing the manner in which
>    nodes participate in the routing process, thus providing context when
>    later threats and attacks are considered.  The goal of the model is
>    to be as detailed as possible so that corresponding components and
>    mechanisms in an individual routing protocol can be readily
>    identified, but also to be as general as possible to maximize the
>    relevancy of this effort for the various existing and future
>    protocols.  Nevertheless, there may be discrepancies, likely in the
>    form of additional elements, when the model is applied to some
>    protocols.  For such cases, the analysis approach laid out in this
>    document should still provide a valid and illustrative path for their
>    security assessment.
>
>    Figure 1 shows that nodes participating in the routing process
>    transmit messages to determine their neighbors (neighbor discovery).
>    Using the neighboring relationships, routing protocols may exchange
>    network topology (including link-specific information) to generate
>    routes or may exchange routes directly as part of a routing exchange;
>    nodes which do not directly participate in the process with a given
>    node will get the route/topology information relayed from others.
> JP> You can remove the previous sentence (no need to make assumption in
> in a framework on the mode of operation of the routing protocol).
> It
>    is likely that a node will store some or all of the routes and
>    topology information according to tradeoffs of node resources and
>    latency associated with the particular routing protocol.
> JP> Why tradeoff with latency ?
> The nodes
>    use the derived routes for making forwarding decisions.
>

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>                ...................................................
>                :                                                 :
>                :                            _________________    :
>    |Node_i|<------->(Neighbor Discovery)--->Neighbor Topology    :
>                :                            -------+---------    :
>                :                                   |             :
>    |Node_j|<------->(Route/Topology       +--------+             :
>                :     Exchange)            |                      :
>                :           |              V            ______    :
>                :           +---->(Route Generation)--->Routes    :
>                :                                       ---+--    :
>                :                                          |      :
>                : Routing on a Node Node_k                 |      :
>                ...................................................
>                                                           |
>    |Forwarding                                            |
>     On Node_l|<-------------------------------------------+
>

>    Notation:
>
>    (Proc)     A process Proc
>
>    ________
>    DataBase   A data storage DataBase
>    --------
>
>    |Node_n|   An external entity Node_n
>
>    ------->   Data flow
>

>          Figure 1: Data Flow Diagram of a Generic Routing Process
>
>    It is seen from Figure 1 that
>
>    o  Assets include
>
>       *  routing and/or topology information;
>
>       *  communication channel resources (bandwidth);
>
>       *  node resources (computing capacity, memory, and remaining
>          energy);
>
>       *  node identifiers (including node identity and ascribed
>          attributes such as relative or absolute node location).
>

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>    o  Points of access include
>
>       *  neighbor discovery;
>
>       *  route/topology exchange;
>
>       *  node physical interfaces (including access to data storage).
>
>    A focus on the above list of assets and points of access enables a
>    more directed assessment of routing security.  Indeed, the intention
>    is to be comprehensive; nonetheless, the discussions to follow on
>    physical related issues are not related to routing protocol design
>    but provided for reference since they do have direct consequences on
>    the security of routing.
>
> 3.2.  The CIA Security Reference Model
>
>    At the conceptual level, security within an information system in
>    general and applied to ROLL in particular is concerned with the
>    primary issues of confidentiality, integrity, and availability.  In
>    the context of ROLL:
>
>    Confidentiality
>          Confidentiality involves the protection of routing information
>          as well as routing neighbor maintenance exchanges so that only
>          authorized and intended network entities may view or access it.
> JP> By "neighbor" just mention that we're referring to routing neighbor
> in the
> context on this document.
>          Because of the wireless,
> JP> Not always wireless ! Just make sure to make it clear even if the
> comment
> below applies to wireless links.
> and sometimes ad hoc, nature of the
>          network, confidentiality also extends to the neighbor state and
>          database information within the routing device since the
>          deployment of the network creates the potential for
>          unauthorized access to the physical devices themselves.
>
>    Integrity
>          Integrity, as a security principle, entails the protection of
>          routing information and routing neighbor maintenance exchanges,
>          as well as derived information maintained in the database, from
>          misuse or unauthorized and improper modification.  In addition,
>          integrity also requires
> JP> Is it really integrity that requires authenticity ?
> the authenticity of claimed identity in
>          the origin and destination of a message, access and removal of
>          data, execution of the routing process, and use of computing
>          and energy resources.
>
>    Availability
>          Availability ensures that routing information exchanges and
>          forwarding services need to be available when they are required
>          for the functioning of the serving network.  Availability will
>          apply to maintaining efficient and correct operation of routing
>          and neighbor discovery exchanges (including needed information)
>

>
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>          and forwarding services so as not to impair or limit the
>          network's central traffic flow function.
>
>    It is noted that, besides those captured in the CIA model, non-
>    repudiation is a security interest under certain circumstances.  With
>    respect to routing, non-repudiation will involve providing some
>    ability to allow traceability or network management review of
>    participants of the routing process including the ability to
>    determine the events and actions leading to a particular routing
>    state.  Non-repudiation implies after the fact and thus relies on the
>    logging or other capture of on-going routing exchanges.  Given the
>    limited resources of a node and potentially the communication
>    channel, and considering the operating mode associated with LLNs,
>    routing transaction logging or auditing process communication
>    overhead will not be practical; as such, non-repudiation is not
>    further considered as a relevant ROLL security issue.
> JP> May be one sentence to define "non-repudiation" would be helpful
>

> 3.3.  Issues Specific to or Amplified in LLNs
>
>    The work [RFC5548] and [RFC5673], as well as two other ongoing
>    efforts, [I-D.ietf-roll-home-routing-reqs] and
>    [I-D.ietf-roll-building-routing-reqs],
> JP> Update the draft-ietf references. They are all RFC (5826 and 5867
> respectively).
> have identified ROLL
> JP> "ROLL specific" -> "routing requirement specific to LLNs"
> specific
>    requirements and constraints for the urban, industrial, home
>    automation, and building automation application domains,
>    respectively.  The following is a list of observations and evaluation
>    of their impact on routing security considerations.
>
>    Limited energy reserve
> JP> s/reserve/resources/
> , memory, and processing resources
> JP> s/processing resources/processing nodes resources/
>
>          As a consequence of these constraints, there is an even more
>          critical need than usual for a careful trade study on which and
>          what level of security services are to be afforded during the
>          system design process.  In addition, the choices of security
>          mechanisms are more stringent.  Synchronization of security
>          states with sleepy nodes is yet another issues.
> JP>s/issues/issue
>

>    Large scale of rolled out network
> JP> You can mention "from a few dozens to several (hundreds) of thousands
> of nodes"
>          The possibly numerous nodes to be deployed, as well as the
>          general level of expertise of the installers, make manual on-
>          site configuration unlikely.  Prolonged rollout and delayed
>          addition of nodes, which may be from old inventory, over the
>          lifetime of the network, also complicate the operations of key
>          management.
>
>    Autonomous operations
>          Self-forming and self-organizing are commonly prescribed
>          requirements of ROLL
> JP> s/ROLL/LLNs
> .  In other words, a ROLL protocol
> JP> A Routing protocol designed for LLNs
> needs to
>          contain elements of ad hoc networking and cannot
> JP> (in most cases)
> rely on manual
>          configuration for initialization or local filtering rules.
>

>
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>          Network topology/ownership changes, partitioning or merging, as
>          well as node replacement, can all contribute to key management
>          issues.
>
>    Highly directional traffic
>          Some types of LLNs see a high percentage of their total traffic
>          traverse between the nodes and the gateways
> JP> Use "LBR" as defined in http://datatracker.ietf.org/doc/draft-ietf-
> roll-terminology/ instead
> of gateway
> where the LLNs
>          connect to wired networks.
> JP> s/wired networks/to non LLN network (since wired links may be present
> in LLNs)
> The special routing status of and
>          the greater volume of traffic near the gateways/sinks
> JP> Same comment use only the LBR terminology throughout the document.
> have
>          routing security consequences.
> JP> You can mention that when P2MP and MP2P traffic represents a majority
> of the traffic
> routing attacks consisting of advertising low route cost may cause
> serious damages.
>

>    Unattended locations and limited physical security
>          Many applications have the nodes deployed in unattended or
>          remote locations; furthermore, the nodes themselves are often
>          built with minimal physical protection.  These constraints
>          lower the barrier of accessing the data or security material
>          stored on the nodes through physical means.
>
>    Support for mobility
>          On the one hand, only a number of applications require the
>          support of mobile nodes, e.g., a home LLN that includes nodes
>          on wearable health care devices or an industry LLN that
>          includes nodes on cranes and vehicles.  On the other hand, if a
>          routing protocol is indeed used in such applications, it will
>          clearly need to have corresponding security mechanisms.
>
>    Support for multicast and anycast
>          Support for multicast and anycast is called out chiefly for
>          large-scale networks.  As these are relatively new routing
>          technologies,
> JP> Heu ... Multicast is not really new
> there has been an ongoing effort devoted to their
>          security mechanisms, e.g., from the IETF Multicast Security
>          working group.  However, inclusion of such mechanisms in a
>          routing protocol, and consequently their security analysis, are
>          still areas not fully developed or their impact entirely
>          understood, whether in a more traditional wired or wireless
>          network, or LLN.
>
>    The above list considers how a LLN's physical constraints, size,
>    operations, and varieties of application areas may impact security.
>    It is noted here also that LLNs commonly have the majority, if not
>    all, of their nodes equipped to route.
> JP> I would suppress the previous sentence, since in this document we are
> only considering nodes acting as routers.
> One of the consequences is
>    that the distinction between the link and network layers become
>    artificial in some respects.  Similarly, the distinction between a
>    host and a router is blurred, especially when the set of applications
>    running on a node is small.
> JP> Same thing for the previous sentence, which may be misleading.
> The continued evolution of ROLL and its
>    security functionality requirements need close attention.
> JP> s/ROLL/routing protocol designed by the ROLL WG
>

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> 3.4.  ROLL Security Objectives
>
>    This subsection applies the CIA model to the routing assets and
>    access points, taking into account the LLN issues, to develop a set
>    of ROLL security objectives.
>
>    Since the fundament function of a routing protocol is to build routes
>    for forwarding packets, it is essential to ensure that
>
>    o  routing/topology information is not tampered during transfer and
>       in storage;
>
>    o  routing/topology information is not misappropriated;
>
>    o  routing/topology information is available when needed.
>
>    In conjunction, it is necessary to be assured of
>
>    o  the authenticity and legitimacy of the participants of the
> JP> routing neighbor
>       neighbor discovery process;
>
>    o  the routing/topology information received was faithfully generated
>       according to the protocol design.
>
>    However, when trust cannot be fully vested through authentication of
>    the principals alone, i.e., concerns of insider attack, assurance of
>    the truthfulness and timeliness of the received routing/topology
>    information is necessary.  With regard to confidentiality, protecting
>    the routing/topology information from eavesdropping or unauthorized
>    exposure is in itself less pertinent in general to the routing
>    function.
>
>    One of the main problems of synchronizing security states of sleepy
>    nodes, as listed in the last subsection, lies in difficulties in
>    authentication; these nodes may not have received in time the most
>    recent update of security material.  Similarly, the issues of minimal
>    manual configuration, prolonged rollout and delayed addition of
>    nodes, and network topology changes also complicate key management.
>    Hence, ROLL
> JP> Change ROLL for routing in LLN
>
> needs to bootstrap the authentication process and allow
>    for flexible expiration scheme of authentication credentials.
>
>    The vulnerability brought forth by some special-function nodes, e.g.,
>    gateways/sinks
> JP> Change for LBR
> requires the assurance, particularly,
>
>    o  of the availability of communication channels and node resources;
>
> JP> but how to ensure and the unavailable of the channels is due to a
> security
> attack as opposed to simply being not operational?
>    o  that the neighbor discovery process operates without undermining
>       routing availability.
>

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>    There are other factors which are not part of a ROLL protocol but
>    directly affecting its function.  These factors include weaker
>    barrier of accessing the data or security material stored on the
>    nodes through physical means; therefore, the internal and external
>    interfaces of a node need to be adequate for guarding the integrity,
>    and possibly the confidentiality, of stored information, as well as
>    the integrity of routing and route generation processes.
>
>    Each individual system's use and environment will dictate how the
>    above objectives are applied, including the choices of security
>    services as well as the strengths of the mechanisms that must be
>    implemented.  The next two sections give a closer look at how the
>    ROLL security objectives may be compromised and countered,
>    respectively.
>

> 4.  Threats and Attacks
>
>    This section outlines general categories of threats under the CIA
>    model and highlights the specific attacks in each of these categories
>    for ROLL.  As defined in [RFC4949], a threat is "a potential for
>    violation of security, which exists when there is a circumstance,
>    capability, action, or event that could breach security and cause
>    harm."  An attack is "an assault on system security that derives from
>    an intelligent threat, i.e., an intelligent act that is a deliberate
>    attempt (especially in the sense of a method or technique) to evade
>    security services and violate the security policy of a system."
>
>    The subsequent subsections consider the threats and their realizing
>    attacks that can cause security breaches under the CIA model to the
>    assets identified in Section 3.1.  The analysis steps through the
>    security concerns of each routing asset and looks at the attacks that
>    can exploit points of access.  The manifestation of the attacks is
>    assumed to be from either inside or outside attackers, whose
>    capabilities may be limited to node-equivalent or more sophisticated
>    computing platforms.
>
> 4.1.  Threats and Attacks on Confidentiality
>
>    The assessment in Section 3.2 indicates that information assets are
>    exposed to confidentiality threats from all points of access.
>
> 4.1.1.  Routing Exchange Exposure
>
>    Routing exchanges include both routing information as well as
>    information associated with the establishment and maintenance of
>    neighbor state information.
>

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>    The exposure of routing information exchanged will allow unauthorized
>    sources to gain access to the content of the exchanges between
>    communicating nodes.  The exposure of neighbor state information will
>    allow unauthorized sources to gain knowledge of communication links
>    between routing nodes that are necessary to maintain routing
>    information exchanges.
>
>    The forms of attack that allow unauthorized access or exposure of
>    routing exchange information, as reported in the literature, include
>
>    o  Deliberate exposure;
>
>    o  Sniffing;
>
>    o  Traffic analysis.
>
> 4.1.2.  Routing Information (Routes and Network Topology) Exposure
>
>    Routes and neighbor topology information are the products of the
>    routing process that are stored within the node device databases.
>
>    The exposure of this information will allow unauthorized sources to
>    gain direct access to the configuration and connectivity of the
>    network thereby exposing routing to targeted attacks on key nodes or
>    links.  Since routes and neighbor topology information is stored
>    within the node device, threats or attacks on the confidentiality of
>    the information will apply to the physical device including specified
>    and unspecified internal and external interfaces.
>
>    The forms of attack that allow unauthorized access or exposure of the
>    routing information (other than occurring through explicit node
>    exchanges) will include
>
>    o  Physical device compromise;
>
>    o  Remote device access attacks (including those occurring through
>       remote network management or software/field upgrade interfaces).
>
>    More detailed descriptions of the exposure attacks on routing
>    exchange and information will be given in Section 5 together with the
>    corresponding countermeasures.
>
> 4.2.  Threats and Attacks on Integrity
>
>    The assessment in Section 3.2 indicates that information and identity
>    assets are exposed to integrity threats from all points of access.
>

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> 4.2.1.  Routing Information Manipulation
>
>    Manipulation of routing information will allow unauthorized sources
>    to influence the operation and convergence of the routing protocols
>    and ultimately impact the forwarding decisions made in the network.
>    Manipulation of neighbor state (topology)
> JP> topology and reachability information
> information will allow
>    unauthorized sources to influence the nodes with which routing
>    information is exchanged and updated.  The consequence of
>    manipulating routing exchanges can thus lead to sub-optimality and
>    fragmentation or partitioning of the network by restricting the
>    universe of routers with which associations can be established and
>    maintained.
>
> JP> Can also lead to attract traffic, black-holes, ...
>    The forms of attack that allow manipulation to compromise the content
>    and validity of routing information include
>
>    o  Falsification, including overclaiming and misclaiming;
>
>    o  Routing information replay;
>
>    o  Byzantine (internal) attacks that permit corruption of routing
>       information in the node even where the node continues to be a
>       validated entity within the network;
>
>    o  Physical device compromise.
>
> 4.2.2.  Node Identity Misappropriation
>
>    Falsification or misappropriation of node identity between routing
>    participants opens the door for other attacks; it can also cause
>    incorrect routing relationships to form and/or topologies to emerge.
>    Routing attacks may also be mounted through less sophisticated node
>    identity misappropriation in which the valid information broadcast or
>    exchanged by a node is replayed without modification.  The receipt of
>    seemingly valid information that is however no longer current can
>    result in routing disruption, and instability (including failure to
>    converge).  Without measures to authenticate the routing participants
>    and to ensure the freshness and validity of the received information
>    the protocol operation can be compromised.  The forms of attack that
>    misuse node identity include
>
>    o  Identity (including Sybil) attacks;
>
>    o  Routing information replay.
>

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> 4.3.  Threats and Attacks on Availability
>
>    The assessment in Section 3.2 indicates that the process and
>    resources assets are exposed to availability threats; attacks of this
>    category may exploit directly or indirectly information exchange or
>    forwarding.
>
> 4.3.1.  Routing Exchange Interference or Disruption
>
>    Interference or disruption of routing information exchanges will
>    allow unauthorized sources to influence the operation and convergence
>    of the routing protocols by impeding the regularity of routing
>    information exchange.
>
>    The forms of attack that allow interference or disruption of routing
>    exchange include
>
>    o  Routing information replay;
>
>    o  HELLO flood attacks and ACK spoofing;
>
>    o  Overload attacks.
>
> 4.3.2.  Network Traffic Forwarding Disruption
>
>    The disruption of the network traffic forwarding capability of the
>    network will undermine the central function of network routers and
>    the ability to handle user traffic.  This threat and the associated
>    attacks affect the availability of the network because of the
>    potential to impair the primary capability of the network.
>
>    The forms of attack that allows disruption of network traffic
>    forwarding include
>
>    o  Selective forwarding attacks;
>
>    o  Sinkhole attacks;
>
>    o  Wormhole attacks.
> JP> Can you add reference to sinkhole and wormhole attacks?
> 4.3.3.  Communications Resource Disruption
>
>    Attacks mounted against the communication channel resource assets
>    needed by the routing protocol can be used as a means of disrupting
>    its operation.  However, while various forms of Denial of Service
>    (DoS) attacks on the underlying transport subsystem will affect
>    routing protocol exchanges and operation (for example physical layer
>    RF jamming in a wireless network or link layer attacks), these
>

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>    attacks cannot be countered by the routing protocol.  As such, the
>    threats to the underlying transport network that supports routing is
>    considered beyond the scope of the current document.  Nonetheless,
>    attacks on the subsystem will affect routing operation and so must be
>    directly addressed within the underlying subsystem and its
>    implemented protocol layers.
>
> 4.3.4.  Node Resource Exhaustion
>
>    A potential security threat to routing can arise from attempts to
>    exhaust the node resource asset by initiating exchanges that can lead
>    to the undue utilization of exhaustion of processing, memory or
>    energy resources.  The establishment and maintenance of routing
>    neighbors opens the routing process to engagement and potential
>    acceptance of multiple neighboring peers.  Association information
>    must be stored for each peer entity and for the wireless network
>    operation provisions made to periodically update and reassess the
>    associations.  An introduced proliferation of apparent routing peers
>    can therefore have a negative impact on node resources.
>
>    Node resources may also be unduly consumed by the attackers
>    attempting uncontrolled topology peering or routing exchanges,
>    routing replays, or the generating of other data traffic floods.
>    Beyond the disruption of communications channel resources, these
>    threats may be able to exhaust node resources only where the
>    engagements are able to proceed with the peer routing entities.
>    Routing operation and network forwarding functions can thus be
>    adversely impacted by node resources exhaustion that stems from
>    attacks that include
>
>    o  Identity (including Sybil) attacks;
>
>    o  Routing information replay attacks;
>
>    o  HELLO flood attacks and ACK spoofing;
>
>    o  Overload attacks.
>

> 5.  Countermeasures
>
>    By recognizing the characteristics of LLNs that may impact routing
>    and identifying potential countermeasures, this framework provides
>    the basis for developing capabilities within ROLL protocols to deter
>    the identified attacks and mitigate the threats.  The following
>    subsections consider such countermeasures by grouping the attacks
>    according to the classification of the CIA model so that associations
>    with the necessary security services are more readily visible.
>

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>    However, the considerations here are more systematic than confined to
>    means available only within routing; the next section will then
>    distill and make recommendations appropriate for a secured ROLL
>    protocol.
>
> 5.1.  Confidentiality Attack Countermeasures
>
>    Attacks on confidentiality may be mounted at the level of the routing
>    information assets, at the points of access associated with routing
>    exchanges between nodes, or through device interface access.  To gain
>    access to routing/topology information, the attacker may rely on a
>    compromised node that deliberately exposes the information during the
>    routing exchange process, may rely on passive sniffing or analysis of
>    routing traffic, or may attempt access through a component or device
>    interface of a tampered routing node.
>
> 5.1.1.  Countering Deliberate Exposure Attacks
>
>    A deliberate exposure attack is one in which an entity that is party
>    to the routing process or topology exchange allows the routing/
>    topology information or generated route information to be exposed to
>    an unauthorized entity during the exchange.
>
>    A prerequisite to countering this type of confidentiality attacks
>    associated with the routing/topology exchange is to ensure that the
>    communicating nodes are authenticated prior to data encryption
>    applied in the routing exchange.  Authentication ensures that the
>    nodes are who they claim to be even though it does not provide an
>    indication of whether the node has been compromised.
>
>    To prevent deliberate exposure, the process that communicating nodes
>    use for establishing communication session keys must be symmetric at
>    each node so that neither node can independently weaken the
>    confidentiality of the exchange without the knowledge of its
>    communicating peer.  A deliberate exposure attack will therefore
>    require more overt and independent action on the part of the
>    offending node.
>
>    Note that the same measures which apply to securing routing/topology
>    exchanges between operational nodes must also extend to field tools
>    and other devices used in a deployed network where such devices can
>    be configured to participate in routing exchanges.
>
> 5.1.2.  Countering Sniffing Attacks
>
>    A sniffing attack seeks to breach routing confidentiality through
>    passive, direct analysis and processing of the information exchanges
>    between nodes.  A sniffing attack in an LLN that is not based on a
>

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>    physical device compromise will rely on the attacker attempting to
>    directly derive information from the over-the-air routing/topology
>    communication exchange (neighbor discovery exchanges may of necessity
>    be conducted in the clear thus limiting the extent to which the
>    information can be kept confidential).
>
>    Sniffing attacks can be directly countered through the use of data
>    encryption for all routing exchanges.  Only when a validated and
>    authenticated node association is completed will routing exchange be
>    allowed to proceed using established session confidentiality keys and
>    an agreed confidentiality algorithm.
> JP> Id security is "turned on". Could you specify that the routing
> protocol
> will include security features according to this framework but some
> scenario
> may not require their use, should they be provide by other means or not
> needed in a specific environment.
> The level of security applied
>    in providing confidentiality will determine the minimum requirement
>    for an attacker mounting this passive security attack.  Because of
>    the resource constraints of LLN devices, symmetric (private) key
>    session security will provide the best tradeoff in terms of node and
>    channel resource overhead and the level of security achieved.  This
>    will of course not preclude the use of asymmetric (public) key
>    encryption during the session key establishment phase.
>
>    As with the key establishment process, data encryption must include
>    an authentication prerequisite to ensure that each node is
>    implementing a level of security that prevents deliberate or
>    inadvertent exposure.  The authenticated key establishment will
>    ensure that confidentiality is not compromised by providing the
>    information to an unauthorized entity (see also [Huang2003]).
>
>    Based on the current state of the art, a minimum 128-bit key length
>    should be applied where robust confidentiality is demanded for
>    routing protection.  This session key shall be applied in conjunction
>    with an encryption algorithm that has been publicly vetted and where
>    applicable approved for the level of security desired.  Algorithms
>    such as AES (adopted by the U.S. government) or Kasumi-Misty (adopted
>    by the 3GPP 3rd generation wireless mobile consortium)
> JP> Could you please ad references ?
>  are examples
>    of symmetric-key algorithms capable of ensuring robust
>    confidentiality for routing exchanges.  The key length, algorithm and
>    mode of operation will be selected as part of the overall security
>    tradeoff that also achieves a balance with the level of
>    confidentiality afforded by the physical device in protecting the
>    routing assets (see Section 5.1.4 below).
>
>    As with any encryption algorithm, the use of ciphering
>    synchronization parameters and limitations to the usage duration of
>    established keys should be part of the security specification to
>    reduce the potential for brute force analysis.
>

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> 5.1.3.  Countering Traffic Analysis
>
>    Traffic analysis provides an indirect means of subverting
>    confidentiality and gaining access to routing information by allowing
>    an attacker to indirectly map the connectivity or flow patterns
>    (including link-load)
> JP> Aren't you making the assumption that LLNs only comprise radio
> link layers ? ** Please make sure that throughout the document you
> are not making any assumption on the link layer (see other comments
> above along the same lines).
> of the network from which other attacks can be
>    mounted.  The traffic analysis attack on a LLN may be passive and
>    relying on the ability to read the immutable source/destination
>    routing information that must remain unencrypted to permit network
>    routing.  Alternatively, attacks can be active through the injection
>    of unauthorized discovery traffic into the network.  By implementing
>    authentication measures between communicating nodes, active traffic
>    analysis attacks can be prevented within the LLN thereby reducing
>    confidentiality vulnerabilities to those associated with passive
>    analysis.
>
>    One way in which passive traffic analysis attacks can be muted is
>    through the support of load balancing that allows traffic to a given
>    destination to be sent along diverse routing paths.  Where the
>    routing protocol supports load balancing along multiple links at each
>    node, the number of routing permutations in a wide area network
>    surges thus increasing the cost of traffic analysis.  Network
>    analysis through this passive attack will require a wider array of
>    analysis points and additional processing on the part of the
>    attacker.  In LLNs, the diverse radio connectivity and dynamic links
>    (including potential frequency hopping) will help to further mitigate
>    traffic analysis attacks when load balancing is implemented.
> JP> Please indicate that this is trued if the link layer is wireless.
>
>    The only means of fully countering a traffic analysis attack is
>    through the use of tunneling (encapsulation) where encryption is
>    applied across the entirety of the original packet source/destination
>    addresses.  With tunneling there is a further requirement that the
>    encapsulating intermediate nodes apply an additional layer of routing
>    so that traffic arrives at the destination through dynamic routes.
>    For LLNs, memory and processing constraints as well as the
>    limitations of the communication channel will preclude both the
>    additional routing traffic overhead
> JP> But tunneling may be used and is actually used in several cases
> (e.g. this is the situation for example with RPL when an additional
> header
> used for example for loop detection is added to the HbP header for
> traffic
> from outside of the LLN to a node inside the LLN).
> and the node implementation
>    required for tunneling countermeasures to traffic analysis.
>
> 5.1.4.  Countering Physical Device Compromise
>
>    Given the distributed nature of LLNs, confidentiality of routing
>    assets and points of access will rely heavily on the security of the
>    routing devices.  One means of precluding attacks on the physical
>    device is to prevent physical access to the node through other
>    external security means.  However, given the environment in which
>    LLNs operate, preventing unauthorized access to the physical device
>    cannot be assured.
> JP> "in some cases" - for example in a Smart Grid environment the
> substation
> has secured access.
> Countermeasures must therefore be employed at the
>

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>    device and component level so that routing/topology or neighbor
>    information and stored route information cannot be accessed even if
>    physical access to the node is obtained.
>
>    With the physical device in the possession of an attacker,
>    unauthorized information access can be attempted by probing internal
>    interfaces or device components.  Device security must therefore move
>    to preventing the reading of device processor code or memory
>    locations without the appropriate security keys and in preventing the
>    access to any information exchanges occurring between individual
>    components.  Information access will then be restricted to external
>    interfaces in which confidentiality, integrity and authentication
>    measures can be applied.
> JP> True but you may want to mention that this is not 'routing security'
> specific.
>    To prevent component information access, deployed routing devices
>    must ensure that their implementation avoids address or data buses
>    being connected to external general purpose input/output (GPIO) pins.
>    Beyond this measure, an important component interface to be protected
>    against attack is the Joint Test Action Group (JTAG) interface used
>    for component and populated circuit board testing after manufacture.
>    To provide security on the routing devices, components should be
>    employed that allow fuses on the JTAG interfaces to be blown to
>    disable access.  This will raise the bar on unauthorized component
>    information access within a captured device.
>
>    At the device level a key component information exchange is between
>    the microprocessor and it associated external memory.  While
>    encryption can be implemented to secure data bus exchanges, the use
>    of integrated physical packaging which avoids inter-component
>    exchanges (other than secure external device exchanges) will increase
>    routing security against a physical device interface attack.  With an
>    integrated package and disabled internal component interfaces, the
>    level of physical device security can be controlled by managing the
>    degree to which the device packaging is protected against expert
>    physical decomposition and analysis.
>
>    The device package should be hardened such that attempts to remove
>    the integrated components will result in damage to access interfaces,
>    ports or pins that prevent retrieval of code or stored information.
>    The degree of VLSI or PCB
> JP> Could you please expand acronyms when first used ?
> package security through manufacture can be
>    selected as a tradeoff or desired security consistent with the level
>    of security achieved by measures applied for other routing assets and
>    points of access.  With package hardening and restricted component
>    access countermeasures, the security level will be raised to that
>    provided by measures employed at the external communications
>    interfaces.
>
>    Another area of node interface vulnerability is that associated with
>

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>    interfaces provided for remote software or firmware upgrades.  This
>    may impact both routing information and routing/topology exchange
>    security where it leads to unauthorized upgrade or change to the
>    routing protocol running on a given node as this type of attack can
>    allow for the execution of compromised or intentionally malicious
>    routing code on multiple nodes.  Countermeasures to this device
>    interface confidentiality attack needs to be addressed in the larger
>    context of node remote access security.  This will ensure not only
>    the authenticity of the provided code (including routing protocol)
>    but that the process is initiated by an authorized (authenticated)
>    entity.
>
>    The above identified countermeasures against attacks on routing
>    information confidentiality through internal device interface
>    compromise must be part of the larger LLN system security as they
>    cannot be addressed within the routing protocol itself.  Similarly,
>    the use of field tools or other devices that allow explicit access to
>    node information must implement security mechanisms to ensure that
>    routing information can be protected against unauthorized access.
>    These protections will also be external to the routing protocol and
>    hence not part of ROLL.
>
> 5.1.5.  Countering Remote Device Access Attacks
>
>    Where LLN nodes are deployed in the field, measures are introduced to
>    allow for remote retrieval of routing data and for software or field
>    upgrades.  These paths create the potential for a device to be
>    remotely accessed across the network or through a provided field
>    tool.  In the case of network management a node can be directly
>    requested to provide routing tables and neighbor information.
>
>    To ensure confidentiality of the node routing information against
>    attacks through remote access, any device local or remote requesting
>    routing information must be authenticated to ensure authorized
>    access.  Since remote access is not invoked as part of a routing
>    protocol security of routing information stored on the node against
>    remote access will not be addressable as part of the routing
>    protocol.
>
> 5.2.  Integrity Attack Countermeasures
>
>    Integrity attack countermeasures address routing information
>    manipulation, as well as node identity and routing information
>    misuse.  Manipulation can occur in the form of falsification attack
>    and physical compromise.  To be effective, the following development
>    considers the two aspects of falsification, namely, the tampering
>    actions and the overclaiming and misclaiming content.  The countering
>    of physical compromise was considered in the previous section and is
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>    not repeated here.  With regard to misuse, there are two types of
>    attacks to be deterred, identity attacks and replay attacks.
>
> 5.2.1.  Countering Tampering Attacks
>
>    Tampering may occur in the form of altering the message being
>    transferred or the data stored.  Therefore, it is necessary to ensure
>    that only authorized nodes can change the portion of the information
>    that is allowed to be mutable, while the integrity of the rest of the
>    information is protected, e.g., through well-studied cryptographic
>    mechanisms.
>
>    Tampering may also occur in the form of insertion or deletion of
>    messages during protocol changes.  Therefore, the protocol needs to
>    ensure the integrity of the sequence of the exchange sequence.
>
>    The countermeasure to tampering needs to
>
>    o  implement access control on storage;
>
>    o  provide data integrity service to transferred messages and stored
>       data;
>
>    o  include sequence number under integrity protection.
>
> 5.2.2.  Countering Overclaiming and Misclaiming Attacks
>
>    Both overclaiming and misclaiming aim to introduce false routes or
>    topology that would not be generated by the network otherwise, while
>    there is not necessarily tampering.  The requisite for a counter is
>    the capability to determine unreasonable routes or topology.
>
>    The counter to overclaiming and misclaiming may employ
>
>    o  comparison with historical routing/topology data;
>
>    o  designs which restrict realizable network topologies.
>
> 5.2.3.  Countering Identity (including Sybil) Attacks
>
>    Identity attacks, sometimes simply called spoofing, seek to gain or
>    damage assets whose access is controlled through identity.  In
>    routing, an identity attacker can illegitimately participate in
>    routing exchanges, distribute false routing information, or cause an
>    invalid outcome of a routing process.
>
>    A perpetrator of Sybil attacks assumes multiple identities.  The
>    result is not only an amplification of the damage to routing, but
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>    extension to new areas, e.g., where geographic distribution is
>    explicit or implicit an asset to an application running on the LLN.
>
> JP> You could mentioned that this is a particular concern in LLN where
> the traffic
> flow is mostly P2MP and MP2P.
>    The counter of identity attacks need to ensure the authenticity and
>    liveliness of the parties of a message exchange; the measure may use
>    shared key or public key based authentication scheme.  On the one
>    hand, the large-scale nature of the LLNs makes the network-wide
>    shared key scheme undesirable from a security perspective; on the
>    other hand, public-key based approaches generally require more
>    computational resources.
> JP> Could elaborate a little bit more on the CPU impact when using
> public-key?
> Each system will need to make trade-off
>    decisions based on its security requirements.
>
> 5.2.4.  Countering Routing Information Replay Attacks
>
>    In routing, message replay can result in false topology and/or
>    routes.  The counter of replay attacks need to ensure the freshness
>    of the message.  On the one hand, there are a number of mechanisms
>    commonly used for countering replay.
> JP> Want to add some references?
> On the other hand, the choice
>    should take into account how a particular mechanism is made available
>    in a LLN.  For example, many LLNs have a central source of time and
>    have it distributed by relaying, such that secured time distribution
>    becomes a prerequisite of using timestamping to counter replay.
> JP> Which means to support clocks, ...
>
> 5.2.5.  Countering Byzantine Routing Information Attacks
>
>    Where a node is captured or compromized but continues to operate for
>    a period with valid network security credentials, the potential
>    exists for routing information to be manipulated.  This compromise of
>    the routing information could thus exist in spite of security
>    countermeasures that operate between the peer routing devices.
>
>    Consistent with the end-to-end principle of communications, such an
>    attack can only be fully addressed through measures operating
>    directly between the routing entities themselves or by means of
>    external entities able to access and independently analyze the
>    routing information.  Verification of the authenticity and liveliness
>    of the routing principals can therefore only provide a limited
>    counter against internal (Byzantine) node attacks.
> JP> Agree but this is not particularly tied to the end-to-end principle.
>
>    For link state routing protocols where information is flooded
> JP> add "with area (OSPF) or levels (ISIS)
>    countermeasures can be directly applied by the routing entities
>    through the processing and comparison of link state information
>    received from different peers.  By comparing the link information
>    from multiple sources decisions can be made by a routing node or
>    external entity with regard to routing information validity.
>
>    For distance vector protocols where information is aggregated at each
>    routing node it is not possible for nodes to directly detect
>

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>    Byzantine information manipulation attacks from the routing
>    information exchange.  In such cases, the routing protocol must
>    include and support indirect communications exchanges between non-
>    adjacent routing peers to provide a secondary channel for performing
>    routing information validation.  S-RIP [Wan2004] is an example of the
>    implementation of this type of dedicated routing protocol security
>    where the correctness of aggregate distance vector information can
>    only be validated by initiating confirmation exchanges directly
>    between nodes that are not routing neighbors.
>
>    Alternatively, an entity external to the routing protocol would be
>    required to collect and audit routing information exchanges to detect
>    the Byzantine attack.  In the context of the current security
>    framework, any protection against Byzantine routing information
>    attacks will need to be directly included within the mechanisms of
>    the ROLL routing protocol.  This can be implemented where such an
>    attack is considered relevant even within the physical device
>    protections discussed in Section 5.1.4
>
> 5.3.  Availability Attack Countermeasures
>
>    As alluded to before, availability requires that routing information
>    exchanges and forwarding mechanisms be available when needed so as to
>    guarantee a proper functioning of the network.  This may, e.g.,
>    include the correct operation of routing information and neighbor
>    state information exchanges, among others.  We will highlight the key
>    features of the security threats along with typical countermeasures
>    to prevent or at least mitigate them.  We will also note that an
>    availability attack may be facilitated by an identity attack as well
>    as a replay attack, as was addressed in Section 5.2.3 and
>    Section 5.2.4, respectively.
>
> 5.3.1.  Countering HELLO Flood Attacks and ACK Spoofing Attacks
>
>    HELLO Flood [Karlof2003],[I-D.suhopark-hello-wsn] and ACK Spoofing
>    attacks are different but highly related forms of attacking a LLN.
>    They essentially lead nodes to believe that suitable routes are
>    available even though they are not and hence constitute a serious
>    availability attack.
>
>    The origin of facilitating a HELLO flood attack lies in the fact that
>    many wireless routing protocols
> JP> Please do not use the terms "wireless routing protocols" since by
> definition of a layered architecture, the routing protocol is not tied to
> a particular link layer. Furthermore this also applies to routing
> protocols
> used in non wireless environments.
> require nodes to send HELLO packets
>    either upon joining or in regular intervals so as to announce or
>    confirm their existence to the network.  Those nodes that receive the
>    HELLO packet assume
> JP> If they receive the packet they *are* in the radio range (again the
> link
> may not be wireless).
> that they are within radio range of the
>    transmitter by means of a bidirectional communication link.
>
>    With this in mind, a malicious node can send or replay HELLO packets
>

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>    using a higher transmission power.  That creates the false illusion
>    of being a neighbor to an increased number of nodes in the network,
>    thereby effectively increasing its unidirectional neighborhood
>    cardinality.  The high quality of the falsely advertised link may
>    coerce nodes to route data via the malicious node.  However, those
>    affected nodes, for which the malicious node is out of radio range,
>    never succeed in their delivery and the packets are effectively
>    dropped.
> JP> Mention "if the link layer is wireless". Not that in PLC, this can
> happen too.
> The symptoms are hence similar to those of a sinkhole,
>    wormhole and selective forwarding attack.
>
>    A malicious HELLO flood attack clearly distorts the network topology.
>    It thus affects protocols building and maintaining the network
>    topology as well as routing protocols as such, since the attack is
>    primarily targeted on protocols that require sharing of information
>    for topology maintenance or flow control.
>
>    To counter HELLO flood attacks, several mutually non-exclusive
>    methods are feasible:
>
>    o  restricting neighborhood cardinality;
>
>    o  facilitating multipath routing;
>
>    o  verifying bidirectionality.
>
>    Restricting the neighborhood cardinality prevents malicious nodes
>    from having an extended set of neighbors beyond some tolerated
>    threshold and thereby preventing topologies to be built where
>    malicious nodes have an extended neighborhood set.
> JP> But thai may artificially reduce the number of "valid" neighbors too.
> Furthermore, as
>    shown in [I-D.suhopark-hello-wsn], if the routing protocol supports
>    multiple paths from a sensing node towards several gateways then
>    HELLO flood attacks can also be diminished; however, the energy-
>    efficiency of such approach is clearly sub-optimal.  Finally,
>    verifying that the link is truly bidirectional by means of, e.g., an
>    ACK handshake and appropriate security measures ensures that a
>    communication link is only established if not only the affected node
>    is within range of the malicious node but also vice versa.  Whilst
>    this does not really eliminate the problem of HELLO flooding, it
>    greatly reduces the number of affected nodes and the probability of
>    such an attack succeeding.
> JP> Even if there is bi-directinality, the attacked node may thus send
> traffic
> to the attackers that claims to have "good" routes though.
>    As for the latter, the adversary may spoof the ACK messages to
>    convince the affected node that the link is truly bidirectional and
>    thereupon drop, tunnel or selectively forward messages.  Such ACK
>    spoofing attack is possible if the malicious node has a receiver
>    which is significantly more sensitive than that of a normal node,
>    thereby effectively extending its range.  Since an ACK spoofing
>    attack facilitates a HELLO flood attack, similar countermeasure are
>

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>    applicable here.  Viable counter and security measures for both
>    attacks have been exposed in [I-D.suhopark-hello-wsn].
>
> 5.3.2.  Countering Overload Attacks
>
>    Overload attacks are a form of DoS attack in that a malicious node
>    overloads the network with irrelevant traffic, thereby draining the
>    nodes' energy budget quicker.
> JP> Energy indeed (a real issue if node are battery operated or using
> energy scavengers) but also inject loads and creates congestions.
> It thus significantly shortens the
>    network lifetime
> JP> If the LLNs is made of battery-operated nodes.
> and hence constitutes another serious availability
>    attack.
>
>    With energy being one of the most precious assets of LLNs, targeting
>    its availability is a fairly obvious attack.  Another way of
>    depleting the energy of a LLN node is to have the malicious node
>    overload the network with irrelevant traffic.  This impacts
>    availability since certain routes get congested which
>
>    o  renders them useless for affected nodes and data can hence not be
>       delivered;
>
>    o  makes routes longer as shortest path algorithms work with the
>       congested network;
> JP> Not sure what you meant above
>    o  depletes nodes quicker and thus shortens the network's
>       availability at large.
> JP> Again if nodes are battery operated.
>
>    Overload attacks can be countered by deploying a series of mutually
>    non-exclusive security measures:
>
>    o  introduce quotas on the traffic rate each node is allowed to send;
> JP> Also referred to as "traffic shaping" but only possible in some
> networks.
>    o  isolate nodes which send traffic above a certain threshold;
> JP> If "Valid" nodes that may attract lots of traffic do no exist in the
> network.
>    o  allow only trusted data to be received and forwarded.
>
>    As for the first one, a simple approach to minimize the harmful
>    impact of an overload attack is to introduce traffic quotas.  This
>    prevents a malicious node from injecting a large amount of traffic
>    into the network, even though it does not prevent said node from
>    injecting irrelevant traffic at all.  Another method is to isolate
> JP> If you have a wireless link, how do you "isolate" the node ? It can
> still sends traffic (at least with some MACs).
>    nodes from the network once it has been detected that more traffic is
>    injected into the network than allowed by a prior set or dynamically
>    adjusted threshold.  Finally, if communication is sufficiently
>    secured, only trusted nodes can receive and forward traffic which
>    also lowers the risk of an overload attack.
>

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> 5.3.3.  Countering Selective Forwarding Attacks
>
>    Selective forwarding attacks are another form of DoS attack which
>    impacts the routing path availability.
>
>    An insider malicious node basically blends neatly in with the network
>    but then may decide to forward and/or manipulate certain packets.  If
>    all packets are dropped, then this attacker is also often referred to
>    as a "black hole".  Such a form of attack is particularly dangerous
>    if coupled with sinkhole attacks since inherently a large amount of
>    traffic is attracted to the malicious node and thereby causing
>    significant damage.  An outside malicious node would selectively jam
>    overheard data flows, where the thus caused collisions
> JP> Again is the MAC is a shared media.
> incur
>    selective forwarding.
>
>    Selective Forwarding attacks can be countered by deploying a series
>    of mutually non-exclusive security measures:
>
>    o  multipath routing of the same message over disjoint paths;
>
>    o  dynamically select the next hop from a set of candidates.
>
>    The first measure basically guarantees that if a message gets lost on
>    a particular routing path due to a malicious selective forwarding
>    attack, there will be another route which successfully delivers the
>    data.  Such method is inherently suboptimal from an energy
>    consumption point of view.  The second method basically involves a
>    constantly changing routing topology in that next-hop routers are
>    chosen from a dynamic set in the hope that the number of malicious
>    nodes in this set is negligible.
> JP> If the routing protocol allows for disjoint routing paths, this is
> even more
> attractive.
> 5.3.4.  Countering Sinkhole Attacks
>
>    In sinkhole attacks, the malicious node manages to attract a lot of
>    traffic mainly by advertising the availability of high-quality links
>    even though there are none.  It hence constitutes a serious attack on
>    availability.
>
>    The malicious node creates a sinkhole by attracting a large amount
>    of, if not all, traffic from surrounding neighbors by advertising in
>    and outwards links of superior quality.  Affected nodes hence eagerly
>    route their traffic via the malicious node which, if coupled with
>    other attacks such as selective forwarding, may lead to serious
>    availability and security breaches.  Such an attack can only be
>    executed by an inside malicious node and is generally very difficult
>    to detect.  An ongoing attack has a profound impact on the network
>    topology and essentially becomes a problem of flow control.
>

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>    Sinkhole attacks can be countered by deploying a series of mutually
>    non-exclusive security measures:
>
>    o  use geographical insights for flow control;
>
>    o  isolate nodes which receive traffic above a certain threshold;
>
>    o  dynamically pick up next hop from set of candidates;
>
>    o  allow only trusted data to be received and forwarded.
>
>    Whilst most of these countermeasures have been discussed before, the
>    use of geographical information deserves further attention.
>    Essentially, if geographic positions of nodes are available, then the
>    network can assure that data is actually routed towards the sink(s)
>    and not elsewhere.
> JP> Yes but it may be wise to route all traffic via a node that is not
> closer to
> the sink but supports interesting capabilities such as aggregation.
> On the other hand, geographic position is a
>    sensitive information that may have security and/or privacy
>    consequences.
>
> 5.3.5.  Countering Wormhole Attacks
>
>    In wormhole attacks at least two malicious nodes shortcut or divert
>    the usual routing path by means of a low-latency out-of-band channel.
>    This changes the availability of certain routing paths and hence
>    constitutes a serious security breach.
>
>    Essentially, two malicious insider nodes use another, more powerful,
>    radio
> JP> Once again, if the link in use is wireless.
> to communicate with each other and thereby distort the would-
>    be-agreed routing path.  This distortion could involve shortcutting
>    and hence paralyzing a large part of the network; it could also
>    involve tunneling the information to another region of the network
>    where there are, e.g., more malicious nodes available to aid the
>    intrusion or where messages are replayed, etc.  In conjunction with
>    selective forwarding, wormhole attacks can create race conditions
>    which impact topology maintenance, routing protocols as well as any
>    security suits built on "time of check" and "time of use".
>
>    Wormhole attacks are very difficult to detect in general but can be
>    mitigated using similar strategies as already outlined above in the
>    context of sinkhole attacks.
>

> 6.  ROLL Security Features
>
>    The assessments and analysis in Section 4 examined all areas of
>    threats and attacks that could impact routing, and the
>    countermeasures presented in Section 5 were reached without confining
>    the consideration to means only available to routing.  This section
>

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>    puts the results into perspective and provides a framework for
>    addressing the derived set of security objectives that must be met by
>    the ROLL protocol.
> JP> s/ROLL protocol/Routing protocol specified by the ROLL Working Group.
> It bears emphasizing that the target here is a
>    generic ROLL protocol and the normative keywords are mainly to convey
>    the relative level of urgency of the features specified.
>
>    The first part of this section, Section 6.1 to Section 6.3, is a
>    prescription of ROLL security features of measures that can be
>    addressed as part of the routing protocol itself.  As routing is one
>    component of a LLN system, the actual strength of the security
>    services afforded to it should be made to conform to each system's
>    security policy; how a design may address the needs of the urban,
>    industrial, home automation, and building automation application
>    domains also needs to be considered.  The second part of this
>    section, Section 6.4 and Section 6.5, discusses system security
>    aspects that may impact routing but that also require considerations
>    beyond the routing protocol, as well as potential approaches.
>
> 6.1.  Confidentiality Features
>
>    With regard to confidentiality, protecting the routing/topology
>    information from eavesdropping or unauthorized exposure is not
>    directly essential to maintaining the routing function.  Breaches of
>    confidentiality may lead to other attacks or the focusing of an
>    attacker's resources (see Section 4.1) but does not of itself
>    directly undermine the operation of the routing function.  However,
>    to protect against, and improve vulnerability against other more
>    direct attacks, routing information confidentiality should be
>    protected.  Thus, a secured ROLL protocol
>
>    o  SHOULD provide payload encryption;
>
>    o  MAY provide tunneling;
>
>    o  MAY provide load balancing;
> JP> You can add a note and point to the requirement RFCs, where this is
> listed as a requirement.
>    o  SHOULD provide privacy, e.g., when geographic information is used.
>
>    Where confidentiality is incorporated into the routing exchanges,
>    encryption algorithms and key lengths need to be specified in
>    accordance of the level of protection dictated by the routing
>    protocol and the associated application domain transport network.  In
>    terms of the life time of the keys, the opportunity to periodically
>    change the encryption key increases the offered level of security for
>    any given implementation.  However, where strong cryptography is
>    employed, physical, procedural, and logical data access protection
>    considerations may have more significant impact on cryptoperiod
>    selection than algorithm and key size factors.  Nevertheless, in
>

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>    general, shorter cryptoperiods, during which a single key is applied,
>    will enhance security.
>
>    Given the mandatory protocol requirement to implement routing node
>    authentication as part of routing integrity (see Section 6.2), key
>    exchanges may be coordinated as part of the integrity verification
>    process.  This provides an opportunity to increase the frequency of
>    key exchange and shorten the cryptoperiod as a compliment to the key
>    length and encryption algorithm required for a given application
>    domain.  For LLNs, the coordination of confidentiality key management
>    with the implementation of node device authentication can thus reduce
>    the overhead associated with supporting data confidentiality.  A new
>    ciphering key may therefore be concurrently generated or updated in
>    conjunction with the mandatory authentication exchange occurring with
>    each routing peer association.
>
> 6.2.  Integrity Features
>
>    The integrity of routing information provides the basis for ensuring
>    that the function of the routing protocol is achieved and maintained.
>    To protect integrity, a secured ROLL protocol
>
>    o  MUST verify message integrity;
>
>    o  MUST verify the authenticity and liveliness of both principals of
>       a connection;
>
>    o  MUST verify message sequence.
>
>    Depending on the nature of the routing protocol, e.g., distance
>    vector or link state, additional measures may be necessary when the
>    validity of the routing information is of concern.  Specifically,
>    verification of routing peer authenticity and liveliness can be used
>    to build a "chain of trust" along the path the routing information
>    flows, such that network-wide information is validated through the
>    concatenation of trust established at each individual routing peer
>    exchange.  This is particularly important in the case of distance
>    vector-based routing protocols, where information is updated at
>    intermediate nodes, In such cases, there are no direct means within
>    routing for a receiver to verify the validity of the routing
>    information beyond the current exchange; as such, nodes would need to
>    be able to communicate and request information from non-adjacent
>    peers (see [Wan2004]) to provide information integrity assurances.
>    With link state-based protocols, on the other hand, routing
>    information can be signed at the source thus providing a means for
>    validating information that originates beyond a routing peer.
>    Therefore, where necessary, a secured ROLL protocol
> JP> You can remove the "o" below since there is no other ones.
>

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>    o  MAY use security auditing mechanisms that are external to routing
>       to verify the validity of the routing information content
>       exchanged among routing peers.
>
> 6.3.  Availability Features
>
>    Availability of routing information is linked to system and network
>    availability which in the case of LLNs require a broader security
>    view beyond the requirements of the routing entities (see
>    Section 6.5).  Where availability of the network is compromised,
>    routing information availability will be accordingly affected.
>    However, to specifically assist in protecting routing availability
>
>    o  MAY restrict neighborhood cardinality;
>
>    o  MAY use multiple paths;
>
>    o  MAY use multiple destinations;
>
>    o  MAY choose randomly if multiple paths are available;
>
>    o  MAY set quotas to limit transmit or receive volume;
>
>    o  MAY use geographic insights for flow control.
>
> 6.4.  Additional Related Features
>
>    If a LLN employs multicast and/or anycast, it MUST secure these
>    protocols
> JP> "protocols" ?
> with the services listed in this sections.  Furthermore,
>    the nodes MUST provide adequate physical tamper resistance to ensure
>    the integrity of stored routing information.
>
>    The functioning of the security services requires keys and
>    credentials.  Therefore, even though not directly a ROLL security
>    requirement, a LLN must include a process for key and credential
>    distribution; a LLN is encouraged to have procedures for their
>    revocation and replacement.
>
> 6.5.  Consideration on Matching Application Domain Needs
>
>    As routing is one component of a LLN system, the actual strength of
>    the security services afforded to it should be made to conform to
>    each system's security policy; how a design may address the needs of
>    the urban, industrial, home automation, and building automation
>    application domains is considered as part of the security
>    architecture in Section 6.5.1.
>
>    The development so far takes into account collectively the impacts of
>

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>    the issues gathered from [RFC5548], [RFC5673],
>    [I-D.ietf-roll-home-routing-reqs], and
>    [I-D.ietf-roll-building-routing-reqs].
> JP> Update the reference (all RFcs now).
> The following two subsections
>    first consider from an architectural perspective how the security
>    design of a ROLL protocol may be made to adapt to the four
>    application domains, and then examine mechanism and protocol
>    operations issues.
>
> 6.5.1.  Security Architecture
>
>    The first challenge for a ROLL protocol security design is to have an
>    architecture that can adequately address a set of very diversified
>    needs.  It is mainly a consequence of the fact that there are both
>    common and non-overlapping requirements from the four application
>    domains, while, conceivably, each individual application will present
>    yet its own unique constraints.
>
>    For a ROLL protocol, the security requirements defined in Section 6.1
>    to Section 6.4 can be addressed at two levels: 1) through measures
>    implemented directly within the routing protocol itself and initiated
>    and controlled by the routing protocol entities; or 2) through
>    measures invoked on behalf of the routing protocol entities but
>    implemented within the transport network
> JP> Be accurate when you used "transport network": you mean "link layer"
> ?
> over which the protocol
>    exchanges occur.
>
>    Where security is directly implemented as part of the routing
>    protocol the security requirements configured by the user (system
>    administrator) will operate independent of the underlying transport
>    network
> JP>s/transport network/link layer
> .  OSPFv2 [RFC2328] is an example of such an approach in which
>    security parameters are exchanged and assessed within the routing
>    protocol messages.  In this case, the mechanism may be, e.g., a
>    header containing security material of configurable security
>    primitives in the fashion of OSPFv2 or RIPv2 [RFC2453].  Where IPsec
>    [RFC4301] is employed to secure the network, the included protocol-
>    specific (OSPF or RIP) security elements are in addition to and
>    independent of those at the network layer.  In the case of LLNs or
>    other networks where system security mandates protective mechanisms
>    at other lower layers of the transport network,
> JP> "lower layers of the transport network" is ambiguous.
> security measures
>    implemented as part of the routing protocol will be redundant to
>    security measures implemented elsewhere as part of the transport
>    network.
> JP> Please replace "transport network" with appropriate terminology where
> needed.
> Thanks.
>    Security mechanisms built into the routing protocol can ensure that
>    all desired countermeasures can be directly addressed by the protocol
>    all the way to the endpoint of the routing exchange.  In particular,
>    routing protocol Byzantine attacks by a compromised node that retains
>    valid network security credentials can only be detected at the level
>    of the information exchanged within the routing protocol.  Such
>

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>    attacks aimed the manipulation of the routing information can only be
>    fully addressed through measures operating directly between the
>    routing entities themselves or external entities able to access and
>    analyze the routing information (see discussion in Section 5.2.5).
>
>    On the other hand, it is more desirable from a LLN device perspective
>    that the ROLL protocol is integrated into the framework of an overall
>    system architecture where the security facility may be shared by
>    different applications and/or across layers for efficiency, and where
>    security policy and configurations can be consistently specified.
>    See, for example, considerations made in RIPng [RFC2080] or the
>    approach presented in [Messerges2003].
>
>    Where the routing protocol is able to rely on security measures
>    configured with the transport network
> JP> Same comment. What do you mean by "transport network"?
> , greater system efficiency can
>    be realized by avoiding potentially redundant security.  Relying on
>    an open trust model [Messerges2003], the security requirements of the
>    routing protocol can be more flexibly met at different layers of the
>    transport network; measures that must be applied to protect the
>    communications network are concurrently able to provide the needed
>    routing protocol protection.
>
>    In addition, in the context of the different application domains, it
>    allows the level of security applied for routing to be consistent
>    with that needed for protecting the network itself.  For example,
>    where AES-128
> JP> Expand terms when first used + add reference
>  is deemed the appropriate standard for network
>    confidentiality of data exchanges at the link layer, that level of
>    security is automatically afforded to routing protocol exchanges.
>    Similarly, where SHA-1
> JP> Same comment
> is stipulated as the standard required for
>    authenticating routing protocol peers, the use of SHA-1 at the
>    network layer between communicating routing devices automatically
>    meets the routing protocol security requirement within the context of
>    open trust across layers within the device.
>
>    A ROLL protocol MUST be made flexible by a design that offers the
>    configuration facility so that the user (network administrator) can
>    choose the security settings that match the application's needs.
>    Furthermore, in the case of LLNs that flexibility should extend to
>    allowing the routing protocol security requirements to be met by
>    measures applied at different protocol layers, provided the
>    identified requirements are collectively met.
>
>    Since Byzantine attacks that can affect the validity of the
>    information content exchanged between routing entities can only be
>    directly countered at the routing protocol level, the ROLL protocol
>    may support mechanisms for verifying routing data validity that
>    extends beyond the chain of trust created through device
>    authentication.  This protocol-specific security mechanism should be
>

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>    made optional within the protocol allowing it to be invoked according
>    to the given routing protocol and application domain and as selected
>    by the system user.  All other ROLL security mechanisms needed to
>    meet the above identified routing security requirements should be
>    flexibly implemented within the transport network (at the IP network
>    layer or higher or lower protocol layers(s)) according to the
>    particular application domain and user network configuration.
>
>    Based on device capabilities and the spectrum of operating
>    environments it would be difficult for a single fixed security design
>    to be applied to address the diversified needs of the four ROLL
>    application domains
> JP> Please list them again (urban, industrial, home/building) + indicate
> that this is also
> true for other application domains.
> without forcing a very low common denominator set
>    of requirements.  On the other hand, providing four individual domain
>    designs that attempt to a priori match each individual domain is also
>    very likely to provide a suitable answer given the degree of network
>    variability even within a given domain.
> JP> The type of link layers in use within each domain also influences the
> overall security.
> Instead, the framework
>    implementation approach recommended for optional, routing protocol-
>    specific measures together with flexible transport network mechanisms
>    can be the most effective.  This approach allows countermeasures
>    against internal attacks to be applied in environments where
>    applicable threats exist.  At the same time, it allows routing
>    protocol security to be configured through measures implemented
>    within the transport network that is commensurate and consistent with
>    the level and strength applied in the particular application domain
>    networks.
>
> 6.5.2.  Mechanisms and Operations
>
>    With an architecture allowing different configurations to meet the
>    application domain needs, the task is then to find suitable
>    mechanisms.  For example, one of the main problems of synchronizing
>    security states of sleepy nodes, as listed in the last subsection,
>    lies in difficulties in authentication; these nodes may not have
>    received in time the most recent update of security material.
>    Similarly, the issues of minimal manual configuration, prolonged
>    rollout and delayed addition of nodes, and network topology changes
>    also complicate security management.  In such case the ROLL protocol
>    may need to bootstrap the authentication process and allow for
>    flexible expiration scheme of authentication credentials.  This
>    exemplifies the need for the coordination and interoperation between
>    the requirements of the ROLL routing protocol and that of the system
>    security elements.
>
>    Similarly, the vulnerability brought forth by some special-function
>    nodes, e.g., gateways/sinks requires the assurance, particularly, of
>    the availability of communication channels and node resources, or
>    that the neighbor discovery process operates without undermining
>    routing availability.
>

>
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>

>    There and other factors which are not part of a ROLL routing protocol
>    can still affect its operation.  This includes elements such as
>    weaker barrier to accessing the data or security material stored on
>    the nodes through physical means; therefore, the internal and
>    external interfaces of a node need to be adequate for guarding the
>    integrity, and possibly the confidentiality, of stored information,
>    as well as the integrity of routing and route generation processes.
>
>    Figure 2 provides an overview of the larger context of system
>    security and the relationship between ROLL requirements and measures
>    and those that relate to the LLN system.
>

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>

>                            Security Services for
>                              ROLL-Addressable
>                            Security Requirements
>                                 |        |
>                             +---+        +---+
>                 Node_i      |                |      Node_j
>                        _____v___          ___v_____
>      Specify Security /         \        /         \ Specify Security
>      Requirements     | Routing |        | Routing |     Requirements
>             +---------| Protocol|        | Protocol|---------+
>             |         | Entity  |        | Entity  |         |
>             |         \_________/        \_________/         |
>             |               |                |               |
>             |ROLL-Specified |                | ROLL-Specified|
>            ---Interface     |                |     Interface---
>             |     ......................................     |
>             |     :         |                |         :     |
>             |     :   +-----+----+      +----+-----+   :     |
>             |     :   |Transport/|      |Transport/|   :     |
>         ____v___  : +>|Network   |      |Network   |<+ :  ___v____
>        /        \ : | +-----+----+      +----+-----+ | : /        \
>        |        |-:-+       |                |       +-:-|        |
>        |Security| :   +-----+----+      +----+-----+   : |Security|
>     +->|Services|-:-->|   Link   |      |   Link   |<--:-|Services|<-+
>     |  |Entity  | :   +-----+----+      +----+-----+   : |Entity  |  |
>     |  |        |-:-+       |                |       +-:-|        |  |
>     |  \________/ : | +-----+----+      +----+-----+ | : \________/  |
>     |             : +>| Physical |      | Physical |<+ :             |
>    Application    :   +-----+----+      +----+-----+   :    Application
>    Domain User    :         |                |         :    Domain User
>    Configuration  :         |__Comm. Channel_|         :  Configuration
>                   :                                    :
>                   ...Transport Network..................
>

>                     Figure 2: LLN Device Security Model
> JP> Great figure. Just clarify "transport/network"
>

>
> 7.  Application of ROLL Security Framework to RPL
> JP> Expand acronym when first used (RPL)
>

>    This section applies the assessments given in Section 6 to RPL
> JP> Ad reference (draft-ietf-roll-rpl)
>  as an
>    illustration of the application of the LLN security framework.
>
>    Specializing the approach used in Section 3.1, Figure 3 gives a
>    level-1 data flow diagram representation of RPL to show the routing
>    "assets" and "points of access" that may be vulnerable and need to be
>    protected.
>

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>                     ............................................
>                     :                                          :
>       |Link-Local   :                                          :
>        Multicast    :                                          :
>        or Node_i|<----->(DIO/DIS/DAO)<--------------+          :
>                     :          ^                    |          :
>                     :          |              ______V______    :
>                     :          |              Candidate        :
>                     :          V              Neighbor List    :
>                     : (RPL Control incl.      ------+------    :
>                     :  Trickle Timer,               |          :
>                     :  Loop Avoidance)              V          :
>                     :          ^            (Route Generation) :
>                     :          |                    |          :
>                     :          |              ______V______    :
>                     :          +------+       Routing Table    :
>                     :                 |       ------+------    :
>                     :                 |             |          :
>                     : RPL on Node_j   |             |          :
>                     ..................|.............|...........
>                                       |             |
>       |Forwarding                     V             |
>        To/From Node_k|<-------->(Read/Write         |
>                                  Flow Label)<-------+
>

>                     Figure 3: Data Flow Diagram of RPL
>
>    From Figure 3, it is seen that threats to the proper operation of RPL
>    are realized through attacks on its DIO, DIS, and DAO messages, as
>    well as on the information the protocol places on the IPv6 Flow
>    Labels.
> JP> Please update since information is now carried in the Hop-by-hop
> header
> with the RPL option (draft in 6man).
>  As set forth in Section 6.1 to Section 6.4, the base
>    security requirements concern message integrity, authenticity and
>    liveliness of the principals of a connection, and protection against
>    message replay; message encryption may be desirable.  The security
>    objectives for RPL are therefore to ensure that
>
>    1.  participants of the DIO, DIS, and DAO message exchanges are
>        authentic;
>
>    2.  the received DIO, DIS, and DAO messages are not modified during
>        transportation;
>
>    3.  the received DIO, DIS, and DAO messages are not retransmissions
>        of previous messages;
>
>    4.  the content of the DIO, DIS, and DAO messages may be made legible
>        to only authorized entities.
>

>
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>    In meeting the above objectives, RPL also needs to provide tunable
>    mechanisms both to allow matching the security afforded to the
>    application domain requirements and to enable efficient use of system
>    resources, as discussed in Section 6.5.1 and Section 6.5.2.
>
>    The functions of the different RPL messages and information placed
>    within the user data plane Flow Labels
> JP> s/"user data plane"/"user data plane (RPL option TLV carried in the
> IPv6 Hop-by-hop header)
> are factors that can be taken
>    into account when deciding the optional security features and levels
>    of strength to be afforded.  For example, the DIO messages build
>    routes to roots while the DAO messages support the building of
>    downward routes to leaf nodes.  Consequently, there may be
>    application environments in which the directions of the routes have
>    different importance and thus warrant the use of different security
>    features and/or strength.  In other words, it may be desirable to
>    have an RPL security design that extends the tunability of the
>    security features and strengths to message types.  The use of a per-
>    message security specification will allow flexibility in permitting
>    application-domain security choices as well as overall tunability.
>

> 8.  IANA Considerations
>
>    This memo includes no request to IANA.
>

> 9.  Security Considerations
>
>    The framework presented in this document provides security analysis
>    and design guidelines with a scope limited to ROLL.  Security
>    services are identified as requirements for securing ROLL.  The
>    results are applied to RPL, with consequent recommendations.
>

> 10.  Acknowledgments
>
>    The authors would like to acknowledge the review and comments from
>    Rene Struik.
>

> 11.  References
>
> 11.1.  Normative References
>
>    [RFC2080]  Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
>               January 1997.
>
>    [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
>               Requirement Levels", BCP 14, RFC 2119, March 1997.
>

>
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>

>    [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
>
>    [RFC2453]  Malkin, G., "RIP Version 2", STD 56, RFC 2453,
>               November 1998.
>
>    [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
>               Internet Protocol", RFC 4301, December 2005.
>
> 11.2.  Informative References
>
>    [Huang2003]
>               Huang, Q., Cukier, J., Kobayashi, H., Liu, B., and J.
>               Zhang, "Fast Authenticated Key Establishment Protocols for
>               Self-Organizing Sensor Networks", in Proceedings of the
>               2nd ACM International Conference on Wireless Sensor
>               Networks and Applications, San Diego, CA, USA, pp. 141-
>               150, Sept. 19 2003.
>
>    [I-D.ietf-roll-building-routing-reqs]
>               Martocci, J., Riou, N., Mil, P., and W. Vermeylen,
>               "Building Automation Routing Requirements in Low Power and
>               Lossy Networks", draft-ietf-roll-building-routing-reqs-09
>               (work in progress), January 2010.
>
>    [I-D.ietf-roll-home-routing-reqs]
>               Brandt, A. and J. Buron, "Home Automation Routing
>               Requirements in Low Power and Lossy Networks",
>               draft-ietf-roll-home-routing-reqs-11 (work in progress),
>               January 2010.
>
> JP> Update the two references above.
>    [I-D.ietf-roll-rpl]
>               Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing
>               Protocol for Low power and Lossy Networks",
>               draft-ietf-roll-rpl-07 (work in progress), March 2010.
>
>    [I-D.ietf-roll-terminology]
>               Vasseur, J., "Terminology in Low power And Lossy
>               Networks", draft-ietf-roll-terminology-03 (work in
>               progress), March 2010.
>
>    [I-D.suhopark-hello-wsn]
>               Park, S., "Routing Security in Sensor Network: HELLO Flood
>               Attack and Defense", draft-suhopark-hello-wsn-00 (work in
>               progress), December 2005.
>
>    [Karlof2003]
>               Karlof, C. and D. Wagner, "Secure routing in wireless
>               sensor networks: attacks and countermeasures", Elsevier
>

>
> Tsao, et al.             Expires October 1, 2010               [Page 39]
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>

>               AdHoc Networks Journal, Special Issue on Sensor Network
>               Applications and Protocols, 1(2):293-315, September 2003.
>
>    [Messerges2003]
>               Messerges, T., Cukier, J., Kevenaar, T., Puhl, L., Struik,
>               R., and E. Callaway, "Low-Power Security for Wireless
>               Sensor Networks", in Proceedings of the 1st ACM Workshop
>               on Security of Ad Hoc and Sensor Networks, Fairfax, VA,
>               USA, pp. 1-11, Oct. 31 2003.
>
>    [Myagmar2005]
>               Myagmar, S., Lee, AJ., and W. Yurcik, "Threat Modeling as
>               a Basis for Security Requirements", in Proceedings of the
>               Symposium on Requirements Engineering for Information
>               Security (SREIS'05), Paris, France, pp. 94-102, Aug
>               29, 2005.
>
>    [RFC4593]  Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to
>               Routing Protocols", RFC 4593, October 2006.
>
>    [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
>               RFC 4949, August 2007.
>
>    [RFC5548]  Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
>               "Routing Requirements for Urban Low-Power and Lossy
>               Networks", RFC 5548, May 2009.
>
>    [RFC5673]  Pister, K., Thubert, P., Dwars, S., and T. Phinney,
>               "Industrial Routing Requirements in Low-Power and Lossy
>               Networks", RFC 5673, October 2009.
>
>    [Wan2004]  Wan, T., Kranakis, E., and PC. van Oorschot, "S-RIP: A
>               Secure Distance Vector Routing Protocol", in Proceedings
>               of the 2nd International Conference on Applied
>               Cryptography and Network Security, Yellow Mountain, China,
>               pp. 103-119, Jun. 8-11 2004.
>

> Authors' Addresses
>
>    Tzeta Tsao (editor)
>    Eka Systems
>    20201 Century Blvd. Suite 250
>    Germantown, Maryland  20874
>    USA
>
>    Email: [email-masked]
>

> Tsao, et al.             Expires October 1, 2010               [Page 40]
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>

>    Roger K. Alexander (editor)
>    Eka Systems
>    20201 Century Blvd. Suite 250
>    Germantown, Maryland  20874
>    USA
>
>    Email: [email-masked]
>

>    Mischa Dohler (editor)
>    CTTC
>    Parc Mediterrani de la Tecnologia, Av. Canal Olimpic S/N
>    Castelldefels, Barcelona  08860
>    Spain
>
>    Email: [email-masked]
>

>    Vanesa Daza (editor)
>    Universitat Pompeu Fabra
>    P/ Circumval.lacio 8, Oficina 308
>    Barcelona  08003
>    Spain
>
>    Email: [email-masked]
>

>    Angel Lozano (editor)
>    Universitat Pompeu Fabra
>    P/ Circumval.lacio 8, Oficina 309
>    Barcelona  08003
>    Spain
>
>    Email: [email-masked]
>
> JP> Are you all editors ? if so, remove the term "Editors"
>

> Tsao, et al.             Expires October 1, 2010               [Page 41]

New description:

 Hi,

 Please find below some detailed comments - Overall well-written document.
 In addition to the comments in-line (search for JP>), I would welcome a
 few
 diagrams especially when you describe the different types of attacks.
 Furthermore,
 as you will see in the comments, be careful not to make the assumption of
 wireles
 links (there are many LLNs with wireless links of course) but this is not
 the only
 type of links. Same comment for the node type (they are not all battery
 operated).
 Thanks ! I will open a ticket capturing all of the comments below.

  JP>

 Starting with ID nits:

 Checking references for intended status: Informational
 ----------------------------------------------------------------------------

   == Outdated reference: draft-ietf-roll-building-routing-reqs has been
      published as RFC 5867

   == Outdated reference: draft-ietf-roll-home-routing-reqs has been
 published
      as RFC 5826

   == Outdated reference: A later version (-11) exists of
      draft-ietf-roll-rpl-07

 Networking Working Group                                    T. Tsao, Ed.
 Internet-Draft                                         R. Alexander, Ed.
 Intended status: Informational                               Eka Systems
 Expires: October 1, 2010                                  M. Dohler, Ed.
                                                                     CTTC
                                                             V. Daza, Ed.
                                                           A. Lozano, Ed.
                                                 Universitat Pompeu Fabra
                                                           March 30, 2010

    A Security Framework for Routing over Low Power and Lossy Networks
                  draft-ietf-roll-security-framework-00

 Abstract

    This document presents a security framework for routing over low
    power and lossy networks.
 JP> Add acronym (LLN)
 The development builds upon previous work
    on routing security and adapts the assessments to the issues and
    constraints specific to low power and lossy networks.  A systematic
    approach is used in defining and evaluating the security threats and
    identifying applicable countermeasures.  These assessments provide
    the basis of the security recommendations for incorporation into low
    power, lossy network routing protocols.  As an illustration, this
    framework is applied to RPL.
 JP> Expand acronym when first used (LLN here).

 Requirements Language

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
    "OPTIONAL" in this document are to be interpreted as described in RFC
    2119 [RFC2119].

 Status of this Memo

    This Internet-Draft is submitted to IETF in full conformance with the
    provisions of BCP 78 and BCP 79.

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
    other groups may also distribute working documents as Internet-
    Drafts.

    Internet-Drafts are draft documents valid for a maximum of six months
    and may be updated, replaced, or obsoleted by other documents at any
    time.  It is inappropriate to use Internet-Drafts as reference
    material or to cite them other than as "work in progress."

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    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt.

    The list of Internet-Draft Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.

    This Internet-Draft will expire on October 1, 2010.

 Copyright Notice

    Copyright (c) 2010 IETF Trust and the persons identified as the
    document authors.  All rights reserved.

    This document is subject to BCP 78 and the IETF Trust's Legal
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    (http://trustee.ietf.org/license-info) in effect on the date of
    publication of this document.  Please review these documents
    carefully, as they describe your rights and restrictions with respect
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    the Trust Legal Provisions and are provided without warranty as
    described in the BSD License.

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 Table of Contents

    1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
    2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
    3.  Considerations on ROLL Security  . . . . . . . . . . . . . . .  5
      3.1.  Routing Assets and Points of Access  . . . . . . . . . . .  6
      3.2.  The CIA Security Reference Model . . . . . . . . . . . . .  8
      3.3.  Issues Specific to or Amplified in LLNs  . . . . . . . . .  9
      3.4.  ROLL Security Objectives . . . . . . . . . . . . . . . . . 11
    4.  Threats and Attacks  . . . . . . . . . . . . . . . . . . . . . 12
      4.1.  Threats and Attacks on Confidentiality . . . . . . . . . . 12
        4.1.1.  Routing Exchange Exposure  . . . . . . . . . . . . . . 12
        4.1.2.  Routing Information (Routes and Network Topology)
                Exposure . . . . . . . . . . . . . . . . . . . . . . . 13
      4.2.  Threats and Attacks on Integrity . . . . . . . . . . . . . 13
        4.2.1.  Routing Information Manipulation . . . . . . . . . . . 14
        4.2.2.  Node Identity Misappropriation . . . . . . . . . . . . 14
      4.3.  Threats and Attacks on Availability  . . . . . . . . . . . 15
        4.3.1.  Routing Exchange Interference or Disruption  . . . . . 15
        4.3.2.  Network Traffic Forwarding Disruption  . . . . . . . . 15
        4.3.3.  Communications Resource Disruption . . . . . . . . . . 15
        4.3.4.  Node Resource Exhaustion . . . . . . . . . . . . . . . 16
    5.  Countermeasures  . . . . . . . . . . . . . . . . . . . . . . . 16
      5.1.  Confidentiality Attack Countermeasures . . . . . . . . . . 17
        5.1.1.  Countering Deliberate Exposure Attacks . . . . . . . . 17
        5.1.2.  Countering Sniffing Attacks  . . . . . . . . . . . . . 17
        5.1.3.  Countering Traffic Analysis  . . . . . . . . . . . . . 19
        5.1.4.  Countering Physical Device Compromise  . . . . . . . . 19
        5.1.5.  Countering Remote Device Access Attacks  . . . . . . . 21
      5.2.  Integrity Attack Countermeasures . . . . . . . . . . . . . 21
        5.2.1.  Countering Tampering Attacks . . . . . . . . . . . . . 22
        5.2.2.  Countering Overclaiming and Misclaiming Attacks  . . . 22
        5.2.3.  Countering Identity (including Sybil) Attacks  . . . . 22
        5.2.4.  Countering Routing Information Replay Attacks  . . . . 23
        5.2.5.  Countering Byzantine Routing Information Attacks . . . 23
      5.3.  Availability Attack Countermeasures  . . . . . . . . . . . 24
        5.3.1.  Countering HELLO Flood Attacks and ACK Spoofing
                Attacks  . . . . . . . . . . . . . . . . . . . . . . . 24
        5.3.2.  Countering Overload Attacks  . . . . . . . . . . . . . 26
        5.3.3.  Countering Selective Forwarding Attacks  . . . . . . . 27
        5.3.4.  Countering Sinkhole Attacks  . . . . . . . . . . . . . 27
        5.3.5.  Countering Wormhole Attacks  . . . . . . . . . . . . . 28
    6.  ROLL Security Features . . . . . . . . . . . . . . . . . . . . 28
      6.1.  Confidentiality Features . . . . . . . . . . . . . . . . . 29
      6.2.  Integrity Features . . . . . . . . . . . . . . . . . . . . 30
      6.3.  Availability Features  . . . . . . . . . . . . . . . . . . 31
      6.4.  Additional Related Features  . . . . . . . . . . . . . . . 31
      6.5.  Consideration on Matching Application Domain Needs . . . . 31

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        6.5.1.  Security Architecture  . . . . . . . . . . . . . . . . 32
        6.5.2.  Mechanisms and Operations  . . . . . . . . . . . . . . 34
    7.  Application of ROLL Security Framework to RPL  . . . . . . . . 36
    8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 38
    9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 38
    10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 38
    11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
      11.1. Normative References . . . . . . . . . . . . . . . . . . . 38
      11.2. Informative References . . . . . . . . . . . . . . . . . . 39
    Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40

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 1.  Terminology

    This document conforms to the terminology defined in
    [I-D.ietf-roll-terminology].

 JP> There are other terms used in the document that could be added here
 (see below).

 2.  Introduction

    In recent times, networked wireless devices have found an increasing
    number of applications in various fields.  Yet, for reasons ranging
    from operational application to economics, these wireless devices
 JP> This does not apply only to wireless links (e.g. PLC)
 are
    often supplied with minimum physical resources, e.g., limited power
    reserve, slow speed or low capability computation, or small memory
    size.  As a consequence, the resulting networks are more prone to
    loss of traffic and other vulnerabilities.  The proliferation of
    these low power and lossy networks (LLNs), however, are drawing
    efforts to examine and address their potential networking challenges.

    This document presents a framework for securing routing over low
    power and lossy networks (ROLL)
 JP> s/ROLL/LLN
  through an analysis that starts from
    the routing basics.  The objective is two-fold.  First, the framework
    will be used to identify pertinent security issues.  Second, it will
    facilitate both the assessment of a protocol's security threats and
    the identification of the necessary features for development of
    secure protocols for ROLL.
 JP> s/ROLL/The ROLL Working Group.

    The approach adopted in this effort proceeds in four steps, to
    examine ROLL security issues, to analyze threats and attacks, to
    consider the countermeasures, and then to make recommendations for
    securing ROLL.
 JP> Could you just replace "ROLL" by the "the routing protocol developed
 by the ROLL Working Group" or Define ROLL as Routing Over Low power
 and Lossy networks.
   The basis is found on identifying the assets and
    points of access of routing and evaluating their security needs based
    on the Confidentiality, Integrity, and Availability (CIA) model in
    the context of LLN.  The utility of this framework is demonstrated
    with an application to RPL [I-D.ietf-roll-rpl].

 3.  Considerations on ROLL Security

    This section sets the stage for the development of the framework by
    applying the systematic approach proposed in [Myagmar2005] to the
    routing security problem, while also drawing references from other
    reviews and assessments found in the literature, particularly,
    [RFC4593] and [Karlof2003].  The subsequent subsections begin with a
    focus on the elements of a generic routing process that is used to
    establish routing assets and points of access of the routing
    functionality.  Next, the CIA security model is briefly described.
    Then, consideration is given to issues specific to or amplified in
    LLNs.  This section concludes with the formulation of a set of

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    security objectives for ROLL.

 3.1.  Routing Assets and Points of Access

    An asset implies important system component (including information,
    process, or physical resource), the access to, corruption or loss of
    which adversely affects the system.  In network routing, assets lie
    in the routing information, routing process, and node's physical
    resources.  That is, the access to, corruption, or loss of these
    elements adversely affects system routing.  In network routing, a
    point of access refers to the point of entry facilitating
    communication with or other interaction with a system component in
    order to use system resources to either manipulate information or
    gain knowledge of the information contained within the system.
    Security of the routing protocol must be focused on the assets of the
    routing nodes and the points of access of the information exchanges
    and information storage that may permit routing compromise.  The
    identification of routing assets and points of access hence provides
    a basis for the identification of associated threats and attacks.

    This subsection identifies assets and points of access of a generic
    routing process with a level-0
 JP> Explain what you mean by "level-0"
 data flow diagram.  The use of the
    data flow diagram allows for a clear, concise model of the routing
    functionality; it also has the benefit of showing the manner in which
    nodes participate in the routing process, thus providing context when
    later threats and attacks are considered.  The goal of the model is
    to be as detailed as possible so that corresponding components and
    mechanisms in an individual routing protocol can be readily
    identified, but also to be as general as possible to maximize the
    relevancy of this effort for the various existing and future
    protocols.  Nevertheless, there may be discrepancies, likely in the
    form of additional elements, when the model is applied to some
    protocols.  For such cases, the analysis approach laid out in this
    document should still provide a valid and illustrative path for their
    security assessment.

    Figure 1 shows that nodes participating in the routing process
    transmit messages to determine their neighbors (neighbor discovery).
    Using the neighboring relationships, routing protocols may exchange
    network topology (including link-specific information) to generate
    routes or may exchange routes directly as part of a routing exchange;
    nodes which do not directly participate in the process with a given
    node will get the route/topology information relayed from others.
 JP> You can remove the previous sentence (no need to make assumption in
 in a framework on the mode of operation of the routing protocol).
 It
    is likely that a node will store some or all of the routes and
    topology information according to tradeoffs of node resources and
    latency associated with the particular routing protocol.
 JP> Why tradeoff with latency ?
 The nodes
    use the derived routes for making forwarding decisions.

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                ...................................................
                :                                                 :
                :                            _________________    :
    |Node_i|<------->(Neighbor Discovery)--->Neighbor Topology    :
                :                            -------+---------    :
                :                                   |             :
    |Node_j|<------->(Route/Topology       +--------+             :
                :     Exchange)            |                      :
                :           |              V            ______    :
                :           +---->(Route Generation)--->Routes    :
                :                                       ---+--    :
                :                                          |      :
                : Routing on a Node Node_k                 |      :
                ...................................................
                                                           |
    |Forwarding                                            |
     On Node_l|<-------------------------------------------+

    Notation:

    (Proc)     A process Proc

    ________
    DataBase   A data storage DataBase
    --------

    |Node_n|   An external entity Node_n

    ------->   Data flow

          Figure 1: Data Flow Diagram of a Generic Routing Process

    It is seen from Figure 1 that

    o  Assets include

       *  routing and/or topology information;

       *  communication channel resources (bandwidth);

       *  node resources (computing capacity, memory, and remaining
          energy);

       *  node identifiers (including node identity and ascribed
          attributes such as relative or absolute node location).

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    o  Points of access include

       *  neighbor discovery;

       *  route/topology exchange;

       *  node physical interfaces (including access to data storage).

    A focus on the above list of assets and points of access enables a
    more directed assessment of routing security.  Indeed, the intention
    is to be comprehensive; nonetheless, the discussions to follow on
    physical related issues are not related to routing protocol design
    but provided for reference since they do have direct consequences on
    the security of routing.

 3.2.  The CIA Security Reference Model

    At the conceptual level, security within an information system in
    general and applied to ROLL in particular is concerned with the
    primary issues of confidentiality, integrity, and availability.  In
    the context of ROLL:

    Confidentiality
          Confidentiality involves the protection of routing information
          as well as routing neighbor maintenance exchanges so that only
          authorized and intended network entities may view or access it.
 JP> By "neighbor" just mention that we're referring to routing neighbor in
 the
 context on this document.
          Because of the wireless,
 JP> Not always wireless ! Just make sure to make it clear even if the
 comment
 below applies to wireless links.
 and sometimes ad hoc, nature of the
          network, confidentiality also extends to the neighbor state and
          database information within the routing device since the
          deployment of the network creates the potential for
          unauthorized access to the physical devices themselves.

    Integrity
          Integrity, as a security principle, entails the protection of
          routing information and routing neighbor maintenance exchanges,
          as well as derived information maintained in the database, from
          misuse or unauthorized and improper modification.  In addition,
          integrity also requires
 JP> Is it really integrity that requires authenticity ?
 the authenticity of claimed identity in
          the origin and destination of a message, access and removal of
          data, execution of the routing process, and use of computing
          and energy resources.

    Availability
          Availability ensures that routing information exchanges and
          forwarding services need to be available when they are required
          for the functioning of the serving network.  Availability will
          apply to maintaining efficient and correct operation of routing
          and neighbor discovery exchanges (including needed information)

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          and forwarding services so as not to impair or limit the
          network's central traffic flow function.

    It is noted that, besides those captured in the CIA model, non-
    repudiation is a security interest under certain circumstances.  With
    respect to routing, non-repudiation will involve providing some
    ability to allow traceability or network management review of
    participants of the routing process including the ability to
    determine the events and actions leading to a particular routing
    state.  Non-repudiation implies after the fact and thus relies on the
    logging or other capture of on-going routing exchanges.  Given the
    limited resources of a node and potentially the communication
    channel, and considering the operating mode associated with LLNs,
    routing transaction logging or auditing process communication
    overhead will not be practical; as such, non-repudiation is not
    further considered as a relevant ROLL security issue.
 JP> May be one sentence to define "non-repudiation" would be helpful

 3.3.  Issues Specific to or Amplified in LLNs

    The work [RFC5548] and [RFC5673], as well as two other ongoing
    efforts, [I-D.ietf-roll-home-routing-reqs] and
    [I-D.ietf-roll-building-routing-reqs],
 JP> Update the draft-ietf references. They are all RFC (5826 and 5867
 respectively).
 have identified ROLL
 JP> "ROLL specific" -> "routing requirement specific to LLNs"
 specific
    requirements and constraints for the urban, industrial, home
    automation, and building automation application domains,
    respectively.  The following is a list of observations and evaluation
    of their impact on routing security considerations.

    Limited energy reserve
 JP> s/reserve/resources/
 , memory, and processing resources
 JP> s/processing resources/processing nodes resources/

          As a consequence of these constraints, there is an even more
          critical need than usual for a careful trade study on which and
          what level of security services are to be afforded during the
          system design process.  In addition, the choices of security
          mechanisms are more stringent.  Synchronization of security
          states with sleepy nodes is yet another issues.
 JP>s/issues/issue

    Large scale of rolled out network
 JP> You can mention "from a few dozens to several (hundreds) of thousands
 of nodes"
          The possibly numerous nodes to be deployed, as well as the
          general level of expertise of the installers, make manual on-
          site configuration unlikely.  Prolonged rollout and delayed
          addition of nodes, which may be from old inventory, over the
          lifetime of the network, also complicate the operations of key
          management.

    Autonomous operations
          Self-forming and self-organizing are commonly prescribed
          requirements of ROLL
 JP> s/ROLL/LLNs
 .  In other words, a ROLL protocol
 JP> A Routing protocol designed for LLNs
 needs to
          contain elements of ad hoc networking and cannot
 JP> (in most cases)
 rely on manual
          configuration for initialization or local filtering rules.

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          Network topology/ownership changes, partitioning or merging, as
          well as node replacement, can all contribute to key management
          issues.

    Highly directional traffic
          Some types of LLNs see a high percentage of their total traffic
          traverse between the nodes and the gateways
 JP> Use "LBR" as defined in http://datatracker.ietf.org/doc/draft-ietf-
 roll-terminology/ instead
 of gateway
 where the LLNs
          connect to wired networks.
 JP> s/wired networks/to non LLN network (since wired links may be present
 in LLNs)
 The special routing status of and
          the greater volume of traffic near the gateways/sinks
 JP> Same comment use only the LBR terminology throughout the document.
 have
          routing security consequences.
 JP> You can mention that when P2MP and MP2P traffic represents a majority
 of the traffic
 routing attacks consisting of advertising low route cost may cause serious
 damages.

    Unattended locations and limited physical security
          Many applications have the nodes deployed in unattended or
          remote locations; furthermore, the nodes themselves are often
          built with minimal physical protection.  These constraints
          lower the barrier of accessing the data or security material
          stored on the nodes through physical means.

    Support for mobility
          On the one hand, only a number of applications require the
          support of mobile nodes, e.g., a home LLN that includes nodes
          on wearable health care devices or an industry LLN that
          includes nodes on cranes and vehicles.  On the other hand, if a
          routing protocol is indeed used in such applications, it will
          clearly need to have corresponding security mechanisms.

    Support for multicast and anycast
          Support for multicast and anycast is called out chiefly for
          large-scale networks.  As these are relatively new routing
          technologies,
 JP> Heu ... Multicast is not really new
 there has been an ongoing effort devoted to their
          security mechanisms, e.g., from the IETF Multicast Security
          working group.  However, inclusion of such mechanisms in a
          routing protocol, and consequently their security analysis, are
          still areas not fully developed or their impact entirely
          understood, whether in a more traditional wired or wireless
          network, or LLN.

    The above list considers how a LLN's physical constraints, size,
    operations, and varieties of application areas may impact security.
    It is noted here also that LLNs commonly have the majority, if not
    all, of their nodes equipped to route.
 JP> I would suppress the previous sentence, since in this document we are
 only considering nodes acting as routers.
 One of the consequences is
    that the distinction between the link and network layers become
    artificial in some respects.  Similarly, the distinction between a
    host and a router is blurred, especially when the set of applications
    running on a node is small.
 JP> Same thing for the previous sentence, which may be misleading.
 The continued evolution of ROLL and its
    security functionality requirements need close attention.
 JP> s/ROLL/routing protocol designed by the ROLL WG

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 3.4.  ROLL Security Objectives

    This subsection applies the CIA model to the routing assets and
    access points, taking into account the LLN issues, to develop a set
    of ROLL security objectives.

    Since the fundament function of a routing protocol is to build routes
    for forwarding packets, it is essential to ensure that

    o  routing/topology information is not tampered during transfer and
       in storage;

    o  routing/topology information is not misappropriated;

    o  routing/topology information is available when needed.

    In conjunction, it is necessary to be assured of

    o  the authenticity and legitimacy of the participants of the
 JP> routing neighbor
       neighbor discovery process;

    o  the routing/topology information received was faithfully generated
       according to the protocol design.

    However, when trust cannot be fully vested through authentication of
    the principals alone, i.e., concerns of insider attack, assurance of
    the truthfulness and timeliness of the received routing/topology
    information is necessary.  With regard to confidentiality, protecting
    the routing/topology information from eavesdropping or unauthorized
    exposure is in itself less pertinent in general to the routing
    function.

    One of the main problems of synchronizing security states of sleepy
    nodes, as listed in the last subsection, lies in difficulties in
    authentication; these nodes may not have received in time the most
    recent update of security material.  Similarly, the issues of minimal
    manual configuration, prolonged rollout and delayed addition of
    nodes, and network topology changes also complicate key management.
    Hence, ROLL
 JP> Change ROLL for routing in LLN

 needs to bootstrap the authentication process and allow
    for flexible expiration scheme of authentication credentials.

    The vulnerability brought forth by some special-function nodes, e.g.,
    gateways/sinks
 JP> Change for LBR
 requires the assurance, particularly,

    o  of the availability of communication channels and node resources;

 JP> but how to ensure and the unavailable of the channels is due to a
 security
 attack as opposed to simply being not operational?
    o  that the neighbor discovery process operates without undermining
       routing availability.

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    There are other factors which are not part of a ROLL protocol but
    directly affecting its function.  These factors include weaker
    barrier of accessing the data or security material stored on the
    nodes through physical means; therefore, the internal and external
    interfaces of a node need to be adequate for guarding the integrity,
    and possibly the confidentiality, of stored information, as well as
    the integrity of routing and route generation processes.

    Each individual system's use and environment will dictate how the
    above objectives are applied, including the choices of security
    services as well as the strengths of the mechanisms that must be
    implemented.  The next two sections give a closer look at how the
    ROLL security objectives may be compromised and countered,
    respectively.

 4.  Threats and Attacks

    This section outlines general categories of threats under the CIA
    model and highlights the specific attacks in each of these categories
    for ROLL.  As defined in [RFC4949], a threat is "a potential for
    violation of security, which exists when there is a circumstance,
    capability, action, or event that could breach security and cause
    harm."  An attack is "an assault on system security that derives from
    an intelligent threat, i.e., an intelligent act that is a deliberate
    attempt (especially in the sense of a method or technique) to evade
    security services and violate the security policy of a system."

    The subsequent subsections consider the threats and their realizing
    attacks that can cause security breaches under the CIA model to the
    assets identified in Section 3.1.  The analysis steps through the
    security concerns of each routing asset and looks at the attacks that
    can exploit points of access.  The manifestation of the attacks is
    assumed to be from either inside or outside attackers, whose
    capabilities may be limited to node-equivalent or more sophisticated
    computing platforms.

 4.1.  Threats and Attacks on Confidentiality

    The assessment in Section 3.2 indicates that information assets are
    exposed to confidentiality threats from all points of access.

 4.1.1.  Routing Exchange Exposure

    Routing exchanges include both routing information as well as
    information associated with the establishment and maintenance of
    neighbor state information.

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    The exposure of routing information exchanged will allow unauthorized
    sources to gain access to the content of the exchanges between
    communicating nodes.  The exposure of neighbor state information will
    allow unauthorized sources to gain knowledge of communication links
    between routing nodes that are necessary to maintain routing
    information exchanges.

    The forms of attack that allow unauthorized access or exposure of
    routing exchange information, as reported in the literature, include

    o  Deliberate exposure;

    o  Sniffing;

    o  Traffic analysis.

 4.1.2.  Routing Information (Routes and Network Topology) Exposure

    Routes and neighbor topology information are the products of the
    routing process that are stored within the node device databases.

    The exposure of this information will allow unauthorized sources to
    gain direct access to the configuration and connectivity of the
    network thereby exposing routing to targeted attacks on key nodes or
    links.  Since routes and neighbor topology information is stored
    within the node device, threats or attacks on the confidentiality of
    the information will apply to the physical device including specified
    and unspecified internal and external interfaces.

    The forms of attack that allow unauthorized access or exposure of the
    routing information (other than occurring through explicit node
    exchanges) will include

    o  Physical device compromise;

    o  Remote device access attacks (including those occurring through
       remote network management or software/field upgrade interfaces).

    More detailed descriptions of the exposure attacks on routing
    exchange and information will be given in Section 5 together with the
    corresponding countermeasures.

 4.2.  Threats and Attacks on Integrity

    The assessment in Section 3.2 indicates that information and identity
    assets are exposed to integrity threats from all points of access.

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 4.2.1.  Routing Information Manipulation

    Manipulation of routing information will allow unauthorized sources
    to influence the operation and convergence of the routing protocols
    and ultimately impact the forwarding decisions made in the network.
    Manipulation of neighbor state (topology)
 JP> topology and reachability information
 information will allow
    unauthorized sources to influence the nodes with which routing
    information is exchanged and updated.  The consequence of
    manipulating routing exchanges can thus lead to sub-optimality and
    fragmentation or partitioning of the network by restricting the
    universe of routers with which associations can be established and
    maintained.

 JP> Can also lead to attract traffic, black-holes, ...
    The forms of attack that allow manipulation to compromise the content
    and validity of routing information include

    o  Falsification, including overclaiming and misclaiming;

    o  Routing information replay;

    o  Byzantine (internal) attacks that permit corruption of routing
       information in the node even where the node continues to be a
       validated entity within the network;

    o  Physical device compromise.

 4.2.2.  Node Identity Misappropriation

    Falsification or misappropriation of node identity between routing
    participants opens the door for other attacks; it can also cause
    incorrect routing relationships to form and/or topologies to emerge.
    Routing attacks may also be mounted through less sophisticated node
    identity misappropriation in which the valid information broadcast or
    exchanged by a node is replayed without modification.  The receipt of
    seemingly valid information that is however no longer current can
    result in routing disruption, and instability (including failure to
    converge).  Without measures to authenticate the routing participants
    and to ensure the freshness and validity of the received information
    the protocol operation can be compromised.  The forms of attack that
    misuse node identity include

    o  Identity (including Sybil) attacks;

    o  Routing information replay.

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 4.3.  Threats and Attacks on Availability

    The assessment in Section 3.2 indicates that the process and
    resources assets are exposed to availability threats; attacks of this
    category may exploit directly or indirectly information exchange or
    forwarding.

 4.3.1.  Routing Exchange Interference or Disruption

    Interference or disruption of routing information exchanges will
    allow unauthorized sources to influence the operation and convergence
    of the routing protocols by impeding the regularity of routing
    information exchange.

    The forms of attack that allow interference or disruption of routing
    exchange include

    o  Routing information replay;

    o  HELLO flood attacks and ACK spoofing;

    o  Overload attacks.

 4.3.2.  Network Traffic Forwarding Disruption

    The disruption of the network traffic forwarding capability of the
    network will undermine the central function of network routers and
    the ability to handle user traffic.  This threat and the associated
    attacks affect the availability of the network because of the
    potential to impair the primary capability of the network.

    The forms of attack that allows disruption of network traffic
    forwarding include

    o  Selective forwarding attacks;

    o  Sinkhole attacks;

    o  Wormhole attacks.
 JP> Can you add reference to sinkhole and wormhole attacks?
 4.3.3.  Communications Resource Disruption

    Attacks mounted against the communication channel resource assets
    needed by the routing protocol can be used as a means of disrupting
    its operation.  However, while various forms of Denial of Service
    (DoS) attacks on the underlying transport subsystem will affect
    routing protocol exchanges and operation (for example physical layer
    RF jamming in a wireless network or link layer attacks), these

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    attacks cannot be countered by the routing protocol.  As such, the
    threats to the underlying transport network that supports routing is
    considered beyond the scope of the current document.  Nonetheless,
    attacks on the subsystem will affect routing operation and so must be
    directly addressed within the underlying subsystem and its
    implemented protocol layers.

 4.3.4.  Node Resource Exhaustion

    A potential security threat to routing can arise from attempts to
    exhaust the node resource asset by initiating exchanges that can lead
    to the undue utilization of exhaustion of processing, memory or
    energy resources.  The establishment and maintenance of routing
    neighbors opens the routing process to engagement and potential
    acceptance of multiple neighboring peers.  Association information
    must be stored for each peer entity and for the wireless network
    operation provisions made to periodically update and reassess the
    associations.  An introduced proliferation of apparent routing peers
    can therefore have a negative impact on node resources.

    Node resources may also be unduly consumed by the attackers
    attempting uncontrolled topology peering or routing exchanges,
    routing replays, or the generating of other data traffic floods.
    Beyond the disruption of communications channel resources, these
    threats may be able to exhaust node resources only where the
    engagements are able to proceed with the peer routing entities.
    Routing operation and network forwarding functions can thus be
    adversely impacted by node resources exhaustion that stems from
    attacks that include

    o  Identity (including Sybil) attacks;

    o  Routing information replay attacks;

    o  HELLO flood attacks and ACK spoofing;

    o  Overload attacks.

 5.  Countermeasures

    By recognizing the characteristics of LLNs that may impact routing
    and identifying potential countermeasures, this framework provides
    the basis for developing capabilities within ROLL protocols to deter
    the identified attacks and mitigate the threats.  The following
    subsections consider such countermeasures by grouping the attacks
    according to the classification of the CIA model so that associations
    with the necessary security services are more readily visible.

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    However, the considerations here are more systematic than confined to
    means available only within routing; the next section will then
    distill and make recommendations appropriate for a secured ROLL
    protocol.

 5.1.  Confidentiality Attack Countermeasures

    Attacks on confidentiality may be mounted at the level of the routing
    information assets, at the points of access associated with routing
    exchanges between nodes, or through device interface access.  To gain
    access to routing/topology information, the attacker may rely on a
    compromised node that deliberately exposes the information during the
    routing exchange process, may rely on passive sniffing or analysis of
    routing traffic, or may attempt access through a component or device
    interface of a tampered routing node.

 5.1.1.  Countering Deliberate Exposure Attacks

    A deliberate exposure attack is one in which an entity that is party
    to the routing process or topology exchange allows the routing/
    topology information or generated route information to be exposed to
    an unauthorized entity during the exchange.

    A prerequisite to countering this type of confidentiality attacks
    associated with the routing/topology exchange is to ensure that the
    communicating nodes are authenticated prior to data encryption
    applied in the routing exchange.  Authentication ensures that the
    nodes are who they claim to be even though it does not provide an
    indication of whether the node has been compromised.

    To prevent deliberate exposure, the process that communicating nodes
    use for establishing communication session keys must be symmetric at
    each node so that neither node can independently weaken the
    confidentiality of the exchange without the knowledge of its
    communicating peer.  A deliberate exposure attack will therefore
    require more overt and independent action on the part of the
    offending node.

    Note that the same measures which apply to securing routing/topology
    exchanges between operational nodes must also extend to field tools
    and other devices used in a deployed network where such devices can
    be configured to participate in routing exchanges.

 5.1.2.  Countering Sniffing Attacks

    A sniffing attack seeks to breach routing confidentiality through
    passive, direct analysis and processing of the information exchanges
    between nodes.  A sniffing attack in an LLN that is not based on a

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    physical device compromise will rely on the attacker attempting to
    directly derive information from the over-the-air routing/topology
    communication exchange (neighbor discovery exchanges may of necessity
    be conducted in the clear thus limiting the extent to which the
    information can be kept confidential).

    Sniffing attacks can be directly countered through the use of data
    encryption for all routing exchanges.  Only when a validated and
    authenticated node association is completed will routing exchange be
    allowed to proceed using established session confidentiality keys and
    an agreed confidentiality algorithm.
 JP> Id security is "turned on". Could you specify that the routing
 protocol
 will include security features according to this framework but some
 scenario
 may not require their use, should they be provide by other means or not
 needed in a specific environment.
 The level of security applied
    in providing confidentiality will determine the minimum requirement
    for an attacker mounting this passive security attack.  Because of
    the resource constraints of LLN devices, symmetric (private) key
    session security will provide the best tradeoff in terms of node and
    channel resource overhead and the level of security achieved.  This
    will of course not preclude the use of asymmetric (public) key
    encryption during the session key establishment phase.

    As with the key establishment process, data encryption must include
    an authentication prerequisite to ensure that each node is
    implementing a level of security that prevents deliberate or
    inadvertent exposure.  The authenticated key establishment will
    ensure that confidentiality is not compromised by providing the
    information to an unauthorized entity (see also [Huang2003]).

    Based on the current state of the art, a minimum 128-bit key length
    should be applied where robust confidentiality is demanded for
    routing protection.  This session key shall be applied in conjunction
    with an encryption algorithm that has been publicly vetted and where
    applicable approved for the level of security desired.  Algorithms
    such as AES (adopted by the U.S. government) or Kasumi-Misty (adopted
    by the 3GPP 3rd generation wireless mobile consortium)
 JP> Could you please ad references ?
  are examples
    of symmetric-key algorithms capable of ensuring robust
    confidentiality for routing exchanges.  The key length, algorithm and
    mode of operation will be selected as part of the overall security
    tradeoff that also achieves a balance with the level of
    confidentiality afforded by the physical device in protecting the
    routing assets (see Section 5.1.4 below).

    As with any encryption algorithm, the use of ciphering
    synchronization parameters and limitations to the usage duration of
    established keys should be part of the security specification to
    reduce the potential for brute force analysis.

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 5.1.3.  Countering Traffic Analysis

    Traffic analysis provides an indirect means of subverting
    confidentiality and gaining access to routing information by allowing
    an attacker to indirectly map the connectivity or flow patterns
    (including link-load)
 JP> Aren't you making the assumption that LLNs only comprise radio
 link layers ? ** Please make sure that throughout the document you
 are not making any assumption on the link layer (see other comments
 above along the same lines).
 of the network from which other attacks can be
    mounted.  The traffic analysis attack on a LLN may be passive and
    relying on the ability to read the immutable source/destination
    routing information that must remain unencrypted to permit network
    routing.  Alternatively, attacks can be active through the injection
    of unauthorized discovery traffic into the network.  By implementing
    authentication measures between communicating nodes, active traffic
    analysis attacks can be prevented within the LLN thereby reducing
    confidentiality vulnerabilities to those associated with passive
    analysis.

    One way in which passive traffic analysis attacks can be muted is
    through the support of load balancing that allows traffic to a given
    destination to be sent along diverse routing paths.  Where the
    routing protocol supports load balancing along multiple links at each
    node, the number of routing permutations in a wide area network
    surges thus increasing the cost of traffic analysis.  Network
    analysis through this passive attack will require a wider array of
    analysis points and additional processing on the part of the
    attacker.  In LLNs, the diverse radio connectivity and dynamic links
    (including potential frequency hopping) will help to further mitigate
    traffic analysis attacks when load balancing is implemented.
 JP> Please indicate that this is trued if the link layer is wireless.

    The only means of fully countering a traffic analysis attack is
    through the use of tunneling (encapsulation) where encryption is
    applied across the entirety of the original packet source/destination
    addresses.  With tunneling there is a further requirement that the
    encapsulating intermediate nodes apply an additional layer of routing
    so that traffic arrives at the destination through dynamic routes.
    For LLNs, memory and processing constraints as well as the
    limitations of the communication channel will preclude both the
    additional routing traffic overhead
 JP> But tunneling may be used and is actually used in several cases
 (e.g. this is the situation for example with RPL when an additional header
 used for example for loop detection is added to the HbP header for traffic
 from outside of the LLN to a node inside the LLN).
 and the node implementation
    required for tunneling countermeasures to traffic analysis.

 5.1.4.  Countering Physical Device Compromise

    Given the distributed nature of LLNs, confidentiality of routing
    assets and points of access will rely heavily on the security of the
    routing devices.  One means of precluding attacks on the physical
    device is to prevent physical access to the node through other
    external security means.  However, given the environment in which
    LLNs operate, preventing unauthorized access to the physical device
    cannot be assured.
 JP> "in some cases" - for example in a Smart Grid environment the
 substation
 has secured access.
 Countermeasures must therefore be employed at the

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    device and component level so that routing/topology or neighbor
    information and stored route information cannot be accessed even if
    physical access to the node is obtained.

    With the physical device in the possession of an attacker,
    unauthorized information access can be attempted by probing internal
    interfaces or device components.  Device security must therefore move
    to preventing the reading of device processor code or memory
    locations without the appropriate security keys and in preventing the
    access to any information exchanges occurring between individual
    components.  Information access will then be restricted to external
    interfaces in which confidentiality, integrity and authentication
    measures can be applied.
 JP> True but you may want to mention that this is not 'routing security'
 specific.
    To prevent component information access, deployed routing devices
    must ensure that their implementation avoids address or data buses
    being connected to external general purpose input/output (GPIO) pins.
    Beyond this measure, an important component interface to be protected
    against attack is the Joint Test Action Group (JTAG) interface used
    for component and populated circuit board testing after manufacture.
    To provide security on the routing devices, components should be
    employed that allow fuses on the JTAG interfaces to be blown to
    disable access.  This will raise the bar on unauthorized component
    information access within a captured device.

    At the device level a key component information exchange is between
    the microprocessor and it associated external memory.  While
    encryption can be implemented to secure data bus exchanges, the use
    of integrated physical packaging which avoids inter-component
    exchanges (other than secure external device exchanges) will increase
    routing security against a physical device interface attack.  With an
    integrated package and disabled internal component interfaces, the
    level of physical device security can be controlled by managing the
    degree to which the device packaging is protected against expert
    physical decomposition and analysis.

    The device package should be hardened such that attempts to remove
    the integrated components will result in damage to access interfaces,
    ports or pins that prevent retrieval of code or stored information.
    The degree of VLSI or PCB
 JP> Could you please expand acronyms when first used ?
 package security through manufacture can be
    selected as a tradeoff or desired security consistent with the level
    of security achieved by measures applied for other routing assets and
    points of access.  With package hardening and restricted component
    access countermeasures, the security level will be raised to that
    provided by measures employed at the external communications
    interfaces.

    Another area of node interface vulnerability is that associated with

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    interfaces provided for remote software or firmware upgrades.  This
    may impact both routing information and routing/topology exchange
    security where it leads to unauthorized upgrade or change to the
    routing protocol running on a given node as this type of attack can
    allow for the execution of compromised or intentionally malicious
    routing code on multiple nodes.  Countermeasures to this device
    interface confidentiality attack needs to be addressed in the larger
    context of node remote access security.  This will ensure not only
    the authenticity of the provided code (including routing protocol)
    but that the process is initiated by an authorized (authenticated)
    entity.

    The above identified countermeasures against attacks on routing
    information confidentiality through internal device interface
    compromise must be part of the larger LLN system security as they
    cannot be addressed within the routing protocol itself.  Similarly,
    the use of field tools or other devices that allow explicit access to
    node information must implement security mechanisms to ensure that
    routing information can be protected against unauthorized access.
    These protections will also be external to the routing protocol and
    hence not part of ROLL.

 5.1.5.  Countering Remote Device Access Attacks

    Where LLN nodes are deployed in the field, measures are introduced to
    allow for remote retrieval of routing data and for software or field
    upgrades.  These paths create the potential for a device to be
    remotely accessed across the network or through a provided field
    tool.  In the case of network management a node can be directly
    requested to provide routing tables and neighbor information.

    To ensure confidentiality of the node routing information against
    attacks through remote access, any device local or remote requesting
    routing information must be authenticated to ensure authorized
    access.  Since remote access is not invoked as part of a routing
    protocol security of routing information stored on the node against
    remote access will not be addressable as part of the routing
    protocol.

 5.2.  Integrity Attack Countermeasures

    Integrity attack countermeasures address routing information
    manipulation, as well as node identity and routing information
    misuse.  Manipulation can occur in the form of falsification attack
    and physical compromise.  To be effective, the following development
    considers the two aspects of falsification, namely, the tampering
    actions and the overclaiming and misclaiming content.  The countering
    of physical compromise was considered in the previous section and is

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    not repeated here.  With regard to misuse, there are two types of
    attacks to be deterred, identity attacks and replay attacks.

 5.2.1.  Countering Tampering Attacks

    Tampering may occur in the form of altering the message being
    transferred or the data stored.  Therefore, it is necessary to ensure
    that only authorized nodes can change the portion of the information
    that is allowed to be mutable, while the integrity of the rest of the
    information is protected, e.g., through well-studied cryptographic
    mechanisms.

    Tampering may also occur in the form of insertion or deletion of
    messages during protocol changes.  Therefore, the protocol needs to
    ensure the integrity of the sequence of the exchange sequence.

    The countermeasure to tampering needs to

    o  implement access control on storage;

    o  provide data integrity service to transferred messages and stored
       data;

    o  include sequence number under integrity protection.

 5.2.2.  Countering Overclaiming and Misclaiming Attacks

    Both overclaiming and misclaiming aim to introduce false routes or
    topology that would not be generated by the network otherwise, while
    there is not necessarily tampering.  The requisite for a counter is
    the capability to determine unreasonable routes or topology.

    The counter to overclaiming and misclaiming may employ

    o  comparison with historical routing/topology data;

    o  designs which restrict realizable network topologies.

 5.2.3.  Countering Identity (including Sybil) Attacks

    Identity attacks, sometimes simply called spoofing, seek to gain or
    damage assets whose access is controlled through identity.  In
    routing, an identity attacker can illegitimately participate in
    routing exchanges, distribute false routing information, or cause an
    invalid outcome of a routing process.

    A perpetrator of Sybil attacks assumes multiple identities.  The
    result is not only an amplification of the damage to routing, but

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    extension to new areas, e.g., where geographic distribution is
    explicit or implicit an asset to an application running on the LLN.

 JP> You could mentioned that this is a particular concern in LLN where the
 traffic
 flow is mostly P2MP and MP2P.
    The counter of identity attacks need to ensure the authenticity and
    liveliness of the parties of a message exchange; the measure may use
    shared key or public key based authentication scheme.  On the one
    hand, the large-scale nature of the LLNs makes the network-wide
    shared key scheme undesirable from a security perspective; on the
    other hand, public-key based approaches generally require more
    computational resources.
 JP> Could elaborate a little bit more on the CPU impact when using
 public-key?
 Each system will need to make trade-off
    decisions based on its security requirements.

 5.2.4.  Countering Routing Information Replay Attacks

    In routing, message replay can result in false topology and/or
    routes.  The counter of replay attacks need to ensure the freshness
    of the message.  On the one hand, there are a number of mechanisms
    commonly used for countering replay.
 JP> Want to add some references?
 On the other hand, the choice
    should take into account how a particular mechanism is made available
    in a LLN.  For example, many LLNs have a central source of time and
    have it distributed by relaying, such that secured time distribution
    becomes a prerequisite of using timestamping to counter replay.
 JP> Which means to support clocks, ...

 5.2.5.  Countering Byzantine Routing Information Attacks

    Where a node is captured or compromized but continues to operate for
    a period with valid network security credentials, the potential
    exists for routing information to be manipulated.  This compromise of
    the routing information could thus exist in spite of security
    countermeasures that operate between the peer routing devices.

    Consistent with the end-to-end principle of communications, such an
    attack can only be fully addressed through measures operating
    directly between the routing entities themselves or by means of
    external entities able to access and independently analyze the
    routing information.  Verification of the authenticity and liveliness
    of the routing principals can therefore only provide a limited
    counter against internal (Byzantine) node attacks.
 JP> Agree but this is not particularly tied to the end-to-end principle.

    For link state routing protocols where information is flooded
 JP> add "with area (OSPF) or levels (ISIS)
    countermeasures can be directly applied by the routing entities
    through the processing and comparison of link state information
    received from different peers.  By comparing the link information
    from multiple sources decisions can be made by a routing node or
    external entity with regard to routing information validity.

    For distance vector protocols where information is aggregated at each
    routing node it is not possible for nodes to directly detect

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    Byzantine information manipulation attacks from the routing
    information exchange.  In such cases, the routing protocol must
    include and support indirect communications exchanges between non-
    adjacent routing peers to provide a secondary channel for performing
    routing information validation.  S-RIP [Wan2004] is an example of the
    implementation of this type of dedicated routing protocol security
    where the correctness of aggregate distance vector information can
    only be validated by initiating confirmation exchanges directly
    between nodes that are not routing neighbors.

    Alternatively, an entity external to the routing protocol would be
    required to collect and audit routing information exchanges to detect
    the Byzantine attack.  In the context of the current security
    framework, any protection against Byzantine routing information
    attacks will need to be directly included within the mechanisms of
    the ROLL routing protocol.  This can be implemented where such an
    attack is considered relevant even within the physical device
    protections discussed in Section 5.1.4

 5.3.  Availability Attack Countermeasures

    As alluded to before, availability requires that routing information
    exchanges and forwarding mechanisms be available when needed so as to
    guarantee a proper functioning of the network.  This may, e.g.,
    include the correct operation of routing information and neighbor
    state information exchanges, among others.  We will highlight the key
    features of the security threats along with typical countermeasures
    to prevent or at least mitigate them.  We will also note that an
    availability attack may be facilitated by an identity attack as well
    as a replay attack, as was addressed in Section 5.2.3 and
    Section 5.2.4, respectively.

 5.3.1.  Countering HELLO Flood Attacks and ACK Spoofing Attacks

    HELLO Flood [Karlof2003],[I-D.suhopark-hello-wsn] and ACK Spoofing
    attacks are different but highly related forms of attacking a LLN.
    They essentially lead nodes to believe that suitable routes are
    available even though they are not and hence constitute a serious
    availability attack.

    The origin of facilitating a HELLO flood attack lies in the fact that
    many wireless routing protocols
 JP> Please do not use the terms "wireless routing protocols" since by
 definition of a layered architecture, the routing protocol is not tied to
 a particular link layer. Furthermore this also applies to routing
 protocols
 used in non wireless environments.
 require nodes to send HELLO packets
    either upon joining or in regular intervals so as to announce or
    confirm their existence to the network.  Those nodes that receive the
    HELLO packet assume
 JP> If they receive the packet they *are* in the radio range (again the
 link
 may not be wireless).
 that they are within radio range of the
    transmitter by means of a bidirectional communication link.

    With this in mind, a malicious node can send or replay HELLO packets

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    using a higher transmission power.  That creates the false illusion
    of being a neighbor to an increased number of nodes in the network,
    thereby effectively increasing its unidirectional neighborhood
    cardinality.  The high quality of the falsely advertised link may
    coerce nodes to route data via the malicious node.  However, those
    affected nodes, for which the malicious node is out of radio range,
    never succeed in their delivery and the packets are effectively
    dropped.
 JP> Mention "if the link layer is wireless". Not that in PLC, this can
 happen too.
 The symptoms are hence similar to those of a sinkhole,
    wormhole and selective forwarding attack.

    A malicious HELLO flood attack clearly distorts the network topology.
    It thus affects protocols building and maintaining the network
    topology as well as routing protocols as such, since the attack is
    primarily targeted on protocols that require sharing of information
    for topology maintenance or flow control.

    To counter HELLO flood attacks, several mutually non-exclusive
    methods are feasible:

    o  restricting neighborhood cardinality;

    o  facilitating multipath routing;

    o  verifying bidirectionality.

    Restricting the neighborhood cardinality prevents malicious nodes
    from having an extended set of neighbors beyond some tolerated
    threshold and thereby preventing topologies to be built where
    malicious nodes have an extended neighborhood set.
 JP> But thai may artificially reduce the number of "valid" neighbors too.
 Furthermore, as
    shown in [I-D.suhopark-hello-wsn], if the routing protocol supports
    multiple paths from a sensing node towards several gateways then
    HELLO flood attacks can also be diminished; however, the energy-
    efficiency of such approach is clearly sub-optimal.  Finally,
    verifying that the link is truly bidirectional by means of, e.g., an
    ACK handshake and appropriate security measures ensures that a
    communication link is only established if not only the affected node
    is within range of the malicious node but also vice versa.  Whilst
    this does not really eliminate the problem of HELLO flooding, it
    greatly reduces the number of affected nodes and the probability of
    such an attack succeeding.
 JP> Even if there is bi-directinality, the attacked node may thus send
 traffic
 to the attackers that claims to have "good" routes though.
    As for the latter, the adversary may spoof the ACK messages to
    convince the affected node that the link is truly bidirectional and
    thereupon drop, tunnel or selectively forward messages.  Such ACK
    spoofing attack is possible if the malicious node has a receiver
    which is significantly more sensitive than that of a normal node,
    thereby effectively extending its range.  Since an ACK spoofing
    attack facilitates a HELLO flood attack, similar countermeasure are

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    applicable here.  Viable counter and security measures for both
    attacks have been exposed in [I-D.suhopark-hello-wsn].

 5.3.2.  Countering Overload Attacks

    Overload attacks are a form of DoS attack in that a malicious node
    overloads the network with irrelevant traffic, thereby draining the
    nodes' energy budget quicker.
 JP> Energy indeed (a real issue if node are battery operated or using
 energy scavengers) but also inject loads and creates congestions.
 It thus significantly shortens the
    network lifetime
 JP> If the LLNs is made of battery-operated nodes.
 and hence constitutes another serious availability
    attack.

    With energy being one of the most precious assets of LLNs, targeting
    its availability is a fairly obvious attack.  Another way of
    depleting the energy of a LLN node is to have the malicious node
    overload the network with irrelevant traffic.  This impacts
    availability since certain routes get congested which

    o  renders them useless for affected nodes and data can hence not be
       delivered;

    o  makes routes longer as shortest path algorithms work with the
       congested network;
 JP> Not sure what you meant above
    o  depletes nodes quicker and thus shortens the network's
       availability at large.
 JP> Again if nodes are battery operated.

    Overload attacks can be countered by deploying a series of mutually
    non-exclusive security measures:

    o  introduce quotas on the traffic rate each node is allowed to send;
 JP> Also referred to as "traffic shaping" but only possible in some
 networks.
    o  isolate nodes which send traffic above a certain threshold;
 JP> If "Valid" nodes that may attract lots of traffic do no exist in the
 network.
    o  allow only trusted data to be received and forwarded.

    As for the first one, a simple approach to minimize the harmful
    impact of an overload attack is to introduce traffic quotas.  This
    prevents a malicious node from injecting a large amount of traffic
    into the network, even though it does not prevent said node from
    injecting irrelevant traffic at all.  Another method is to isolate
 JP> If you have a wireless link, how do you "isolate" the node ? It can
 still sends traffic (at least with some MACs).
    nodes from the network once it has been detected that more traffic is
    injected into the network than allowed by a prior set or dynamically
    adjusted threshold.  Finally, if communication is sufficiently
    secured, only trusted nodes can receive and forward traffic which
    also lowers the risk of an overload attack.

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 5.3.3.  Countering Selective Forwarding Attacks

    Selective forwarding attacks are another form of DoS attack which
    impacts the routing path availability.

    An insider malicious node basically blends neatly in with the network
    but then may decide to forward and/or manipulate certain packets.  If
    all packets are dropped, then this attacker is also often referred to
    as a "black hole".  Such a form of attack is particularly dangerous
    if coupled with sinkhole attacks since inherently a large amount of
    traffic is attracted to the malicious node and thereby causing
    significant damage.  An outside malicious node would selectively jam
    overheard data flows, where the thus caused collisions
 JP> Again is the MAC is a shared media.
 incur
    selective forwarding.

    Selective Forwarding attacks can be countered by deploying a series
    of mutually non-exclusive security measures:

    o  multipath routing of the same message over disjoint paths;

    o  dynamically select the next hop from a set of candidates.

    The first measure basically guarantees that if a message gets lost on
    a particular routing path due to a malicious selective forwarding
    attack, there will be another route which successfully delivers the
    data.  Such method is inherently suboptimal from an energy
    consumption point of view.  The second method basically involves a
    constantly changing routing topology in that next-hop routers are
    chosen from a dynamic set in the hope that the number of malicious
    nodes in this set is negligible.
 JP> If the routing protocol allows for disjoint routing paths, this is
 even more
 attractive.
 5.3.4.  Countering Sinkhole Attacks

    In sinkhole attacks, the malicious node manages to attract a lot of
    traffic mainly by advertising the availability of high-quality links
    even though there are none.  It hence constitutes a serious attack on
    availability.

    The malicious node creates a sinkhole by attracting a large amount
    of, if not all, traffic from surrounding neighbors by advertising in
    and outwards links of superior quality.  Affected nodes hence eagerly
    route their traffic via the malicious node which, if coupled with
    other attacks such as selective forwarding, may lead to serious
    availability and security breaches.  Such an attack can only be
    executed by an inside malicious node and is generally very difficult
    to detect.  An ongoing attack has a profound impact on the network
    topology and essentially becomes a problem of flow control.

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    Sinkhole attacks can be countered by deploying a series of mutually
    non-exclusive security measures:

    o  use geographical insights for flow control;

    o  isolate nodes which receive traffic above a certain threshold;

    o  dynamically pick up next hop from set of candidates;

    o  allow only trusted data to be received and forwarded.

    Whilst most of these countermeasures have been discussed before, the
    use of geographical information deserves further attention.
    Essentially, if geographic positions of nodes are available, then the
    network can assure that data is actually routed towards the sink(s)
    and not elsewhere.
 JP> Yes but it may be wise to route all traffic via a node that is not
 closer to
 the sink but supports interesting capabilities such as aggregation.
 On the other hand, geographic position is a
    sensitive information that may have security and/or privacy
    consequences.

 5.3.5.  Countering Wormhole Attacks

    In wormhole attacks at least two malicious nodes shortcut or divert
    the usual routing path by means of a low-latency out-of-band channel.
    This changes the availability of certain routing paths and hence
    constitutes a serious security breach.

    Essentially, two malicious insider nodes use another, more powerful,
    radio
 JP> Once again, if the link in use is wireless.
 to communicate with each other and thereby distort the would-
    be-agreed routing path.  This distortion could involve shortcutting
    and hence paralyzing a large part of the network; it could also
    involve tunneling the information to another region of the network
    where there are, e.g., more malicious nodes available to aid the
    intrusion or where messages are replayed, etc.  In conjunction with
    selective forwarding, wormhole attacks can create race conditions
    which impact topology maintenance, routing protocols as well as any
    security suits built on "time of check" and "time of use".

    Wormhole attacks are very difficult to detect in general but can be
    mitigated using similar strategies as already outlined above in the
    context of sinkhole attacks.

 6.  ROLL Security Features

    The assessments and analysis in Section 4 examined all areas of
    threats and attacks that could impact routing, and the
    countermeasures presented in Section 5 were reached without confining
    the consideration to means only available to routing.  This section

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    puts the results into perspective and provides a framework for
    addressing the derived set of security objectives that must be met by
    the ROLL protocol.
 JP> s/ROLL protocol/Routing protocol specified by the ROLL Working Group.
 It bears emphasizing that the target here is a
    generic ROLL protocol and the normative keywords are mainly to convey
    the relative level of urgency of the features specified.

    The first part of this section, Section 6.1 to Section 6.3, is a
    prescription of ROLL security features of measures that can be
    addressed as part of the routing protocol itself.  As routing is one
    component of a LLN system, the actual strength of the security
    services afforded to it should be made to conform to each system's
    security policy; how a design may address the needs of the urban,
    industrial, home automation, and building automation application
    domains also needs to be considered.  The second part of this
    section, Section 6.4 and Section 6.5, discusses system security
    aspects that may impact routing but that also require considerations
    beyond the routing protocol, as well as potential approaches.

 6.1.  Confidentiality Features

    With regard to confidentiality, protecting the routing/topology
    information from eavesdropping or unauthorized exposure is not
    directly essential to maintaining the routing function.  Breaches of
    confidentiality may lead to other attacks or the focusing of an
    attacker's resources (see Section 4.1) but does not of itself
    directly undermine the operation of the routing function.  However,
    to protect against, and improve vulnerability against other more
    direct attacks, routing information confidentiality should be
    protected.  Thus, a secured ROLL protocol

    o  SHOULD provide payload encryption;

    o  MAY provide tunneling;

    o  MAY provide load balancing;
 JP> You can add a note and point to the requirement RFCs, where this is
 listed as a requirement.
    o  SHOULD provide privacy, e.g., when geographic information is used.

    Where confidentiality is incorporated into the routing exchanges,
    encryption algorithms and key lengths need to be specified in
    accordance of the level of protection dictated by the routing
    protocol and the associated application domain transport network.  In
    terms of the life time of the keys, the opportunity to periodically
    change the encryption key increases the offered level of security for
    any given implementation.  However, where strong cryptography is
    employed, physical, procedural, and logical data access protection
    considerations may have more significant impact on cryptoperiod
    selection than algorithm and key size factors.  Nevertheless, in

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    general, shorter cryptoperiods, during which a single key is applied,
    will enhance security.

    Given the mandatory protocol requirement to implement routing node
    authentication as part of routing integrity (see Section 6.2), key
    exchanges may be coordinated as part of the integrity verification
    process.  This provides an opportunity to increase the frequency of
    key exchange and shorten the cryptoperiod as a compliment to the key
    length and encryption algorithm required for a given application
    domain.  For LLNs, the coordination of confidentiality key management
    with the implementation of node device authentication can thus reduce
    the overhead associated with supporting data confidentiality.  A new
    ciphering key may therefore be concurrently generated or updated in
    conjunction with the mandatory authentication exchange occurring with
    each routing peer association.

 6.2.  Integrity Features

    The integrity of routing information provides the basis for ensuring
    that the function of the routing protocol is achieved and maintained.
    To protect integrity, a secured ROLL protocol

    o  MUST verify message integrity;

    o  MUST verify the authenticity and liveliness of both principals of
       a connection;

    o  MUST verify message sequence.

    Depending on the nature of the routing protocol, e.g., distance
    vector or link state, additional measures may be necessary when the
    validity of the routing information is of concern.  Specifically,
    verification of routing peer authenticity and liveliness can be used
    to build a "chain of trust" along the path the routing information
    flows, such that network-wide information is validated through the
    concatenation of trust established at each individual routing peer
    exchange.  This is particularly important in the case of distance
    vector-based routing protocols, where information is updated at
    intermediate nodes, In such cases, there are no direct means within
    routing for a receiver to verify the validity of the routing
    information beyond the current exchange; as such, nodes would need to
    be able to communicate and request information from non-adjacent
    peers (see [Wan2004]) to provide information integrity assurances.
    With link state-based protocols, on the other hand, routing
    information can be signed at the source thus providing a means for
    validating information that originates beyond a routing peer.
    Therefore, where necessary, a secured ROLL protocol
 JP> You can remove the "o" below since there is no other ones.

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    o  MAY use security auditing mechanisms that are external to routing
       to verify the validity of the routing information content
       exchanged among routing peers.

 6.3.  Availability Features

    Availability of routing information is linked to system and network
    availability which in the case of LLNs require a broader security
    view beyond the requirements of the routing entities (see
    Section 6.5).  Where availability of the network is compromised,
    routing information availability will be accordingly affected.
    However, to specifically assist in protecting routing availability

    o  MAY restrict neighborhood cardinality;

    o  MAY use multiple paths;

    o  MAY use multiple destinations;

    o  MAY choose randomly if multiple paths are available;

    o  MAY set quotas to limit transmit or receive volume;

    o  MAY use geographic insights for flow control.

 6.4.  Additional Related Features

    If a LLN employs multicast and/or anycast, it MUST secure these
    protocols
 JP> "protocols" ?
 with the services listed in this sections.  Furthermore,
    the nodes MUST provide adequate physical tamper resistance to ensure
    the integrity of stored routing information.

    The functioning of the security services requires keys and
    credentials.  Therefore, even though not directly a ROLL security
    requirement, a LLN must include a process for key and credential
    distribution; a LLN is encouraged to have procedures for their
    revocation and replacement.

 6.5.  Consideration on Matching Application Domain Needs

    As routing is one component of a LLN system, the actual strength of
    the security services afforded to it should be made to conform to
    each system's security policy; how a design may address the needs of
    the urban, industrial, home automation, and building automation
    application domains is considered as part of the security
    architecture in Section 6.5.1.

    The development so far takes into account collectively the impacts of

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    the issues gathered from [RFC5548], [RFC5673],
    [I-D.ietf-roll-home-routing-reqs], and
    [I-D.ietf-roll-building-routing-reqs].
 JP> Update the reference (all RFcs now).
 The following two subsections
    first consider from an architectural perspective how the security
    design of a ROLL protocol may be made to adapt to the four
    application domains, and then examine mechanism and protocol
    operations issues.

 6.5.1.  Security Architecture

    The first challenge for a ROLL protocol security design is to have an
    architecture that can adequately address a set of very diversified
    needs.  It is mainly a consequence of the fact that there are both
    common and non-overlapping requirements from the four application
    domains, while, conceivably, each individual application will present
    yet its own unique constraints.

    For a ROLL protocol, the security requirements defined in Section 6.1
    to Section 6.4 can be addressed at two levels: 1) through measures
    implemented directly within the routing protocol itself and initiated
    and controlled by the routing protocol entities; or 2) through
    measures invoked on behalf of the routing protocol entities but
    implemented within the transport network
 JP> Be accurate when you used "transport network": you mean "link layer" ?
 over which the protocol
    exchanges occur.

    Where security is directly implemented as part of the routing
    protocol the security requirements configured by the user (system
    administrator) will operate independent of the underlying transport
    network
 JP>s/transport network/link layer
 .  OSPFv2 [RFC2328] is an example of such an approach in which
    security parameters are exchanged and assessed within the routing
    protocol messages.  In this case, the mechanism may be, e.g., a
    header containing security material of configurable security
    primitives in the fashion of OSPFv2 or RIPv2 [RFC2453].  Where IPsec
    [RFC4301] is employed to secure the network, the included protocol-
    specific (OSPF or RIP) security elements are in addition to and
    independent of those at the network layer.  In the case of LLNs or
    other networks where system security mandates protective mechanisms
    at other lower layers of the transport network,
 JP> "lower layers of the transport network" is ambiguous.
 security measures
    implemented as part of the routing protocol will be redundant to
    security measures implemented elsewhere as part of the transport
    network.
 JP> Please replace "transport network" with appropriate terminology where
 needed.
 Thanks.
    Security mechanisms built into the routing protocol can ensure that
    all desired countermeasures can be directly addressed by the protocol
    all the way to the endpoint of the routing exchange.  In particular,
    routing protocol Byzantine attacks by a compromised node that retains
    valid network security credentials can only be detected at the level
    of the information exchanged within the routing protocol.  Such

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    attacks aimed the manipulation of the routing information can only be
    fully addressed through measures operating directly between the
    routing entities themselves or external entities able to access and
    analyze the routing information (see discussion in Section 5.2.5).

    On the other hand, it is more desirable from a LLN device perspective
    that the ROLL protocol is integrated into the framework of an overall
    system architecture where the security facility may be shared by
    different applications and/or across layers for efficiency, and where
    security policy and configurations can be consistently specified.
    See, for example, considerations made in RIPng [RFC2080] or the
    approach presented in [Messerges2003].

    Where the routing protocol is able to rely on security measures
    configured with the transport network
 JP> Same comment. What do you mean by "transport network"?
 , greater system efficiency can
    be realized by avoiding potentially redundant security.  Relying on
    an open trust model [Messerges2003], the security requirements of the
    routing protocol can be more flexibly met at different layers of the
    transport network; measures that must be applied to protect the
    communications network are concurrently able to provide the needed
    routing protocol protection.

    In addition, in the context of the different application domains, it
    allows the level of security applied for routing to be consistent
    with that needed for protecting the network itself.  For example,
    where AES-128
 JP> Expand terms when first used + add reference
  is deemed the appropriate standard for network
    confidentiality of data exchanges at the link layer, that level of
    security is automatically afforded to routing protocol exchanges.
    Similarly, where SHA-1
 JP> Same comment
 is stipulated as the standard required for
    authenticating routing protocol peers, the use of SHA-1 at the
    network layer between communicating routing devices automatically
    meets the routing protocol security requirement within the context of
    open trust across layers within the device.

    A ROLL protocol MUST be made flexible by a design that offers the
    configuration facility so that the user (network administrator) can
    choose the security settings that match the application's needs.
    Furthermore, in the case of LLNs that flexibility should extend to
    allowing the routing protocol security requirements to be met by
    measures applied at different protocol layers, provided the
    identified requirements are collectively met.

    Since Byzantine attacks that can affect the validity of the
    information content exchanged between routing entities can only be
    directly countered at the routing protocol level, the ROLL protocol
    may support mechanisms for verifying routing data validity that
    extends beyond the chain of trust created through device
    authentication.  This protocol-specific security mechanism should be

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    made optional within the protocol allowing it to be invoked according
    to the given routing protocol and application domain and as selected
    by the system user.  All other ROLL security mechanisms needed to
    meet the above identified routing security requirements should be
    flexibly implemented within the transport network (at the IP network
    layer or higher or lower protocol layers(s)) according to the
    particular application domain and user network configuration.

    Based on device capabilities and the spectrum of operating
    environments it would be difficult for a single fixed security design
    to be applied to address the diversified needs of the four ROLL
    application domains
 JP> Please list them again (urban, industrial, home/building) + indicate
 that this is also
 true for other application domains.
 without forcing a very low common denominator set
    of requirements.  On the other hand, providing four individual domain
    designs that attempt to a priori match each individual domain is also
    very likely to provide a suitable answer given the degree of network
    variability even within a given domain.
 JP> The type of link layers in use within each domain also influences the
 overall security.
 Instead, the framework
    implementation approach recommended for optional, routing protocol-
    specific measures together with flexible transport network mechanisms
    can be the most effective.  This approach allows countermeasures
    against internal attacks to be applied in environments where
    applicable threats exist.  At the same time, it allows routing
    protocol security to be configured through measures implemented
    within the transport network that is commensurate and consistent with
    the level and strength applied in the particular application domain
    networks.

 6.5.2.  Mechanisms and Operations

    With an architecture allowing different configurations to meet the
    application domain needs, the task is then to find suitable
    mechanisms.  For example, one of the main problems of synchronizing
    security states of sleepy nodes, as listed in the last subsection,
    lies in difficulties in authentication; these nodes may not have
    received in time the most recent update of security material.
    Similarly, the issues of minimal manual configuration, prolonged
    rollout and delayed addition of nodes, and network topology changes
    also complicate security management.  In such case the ROLL protocol
    may need to bootstrap the authentication process and allow for
    flexible expiration scheme of authentication credentials.  This
    exemplifies the need for the coordination and interoperation between
    the requirements of the ROLL routing protocol and that of the system
    security elements.

    Similarly, the vulnerability brought forth by some special-function
    nodes, e.g., gateways/sinks requires the assurance, particularly, of
    the availability of communication channels and node resources, or
    that the neighbor discovery process operates without undermining
    routing availability.

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    There and other factors which are not part of a ROLL routing protocol
    can still affect its operation.  This includes elements such as
    weaker barrier to accessing the data or security material stored on
    the nodes through physical means; therefore, the internal and
    external interfaces of a node need to be adequate for guarding the
    integrity, and possibly the confidentiality, of stored information,
    as well as the integrity of routing and route generation processes.

    Figure 2 provides an overview of the larger context of system
    security and the relationship between ROLL requirements and measures
    and those that relate to the LLN system.

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                            Security Services for
                              ROLL-Addressable
                            Security Requirements
                                 |        |
                             +---+        +---+
                 Node_i      |                |      Node_j
                        _____v___          ___v_____
      Specify Security /         \        /         \ Specify Security
      Requirements     | Routing |        | Routing |     Requirements
             +---------| Protocol|        | Protocol|---------+
             |         | Entity  |        | Entity  |         |
             |         \_________/        \_________/         |
             |               |                |               |
             |ROLL-Specified |                | ROLL-Specified|
            ---Interface     |                |     Interface---
             |     ......................................     |
             |     :         |                |         :     |
             |     :   +-----+----+      +----+-----+   :     |
             |     :   |Transport/|      |Transport/|   :     |
         ____v___  : +>|Network   |      |Network   |<+ :  ___v____
        /        \ : | +-----+----+      +----+-----+ | : /        \
        |        |-:-+       |                |       +-:-|        |
        |Security| :   +-----+----+      +----+-----+   : |Security|
     +->|Services|-:-->|   Link   |      |   Link   |<--:-|Services|<-+
     |  |Entity  | :   +-----+----+      +----+-----+   : |Entity  |  |
     |  |        |-:-+       |                |       +-:-|        |  |
     |  \________/ : | +-----+----+      +----+-----+ | : \________/  |
     |             : +>| Physical |      | Physical |<+ :             |
    Application    :   +-----+----+      +----+-----+   :    Application
    Domain User    :         |                |         :    Domain User
    Configuration  :         |__Comm. Channel_|         :  Configuration
                   :                                    :
                   ...Transport Network..................

                     Figure 2: LLN Device Security Model
 JP> Great figure. Just clarify "transport/network"

 7.  Application of ROLL Security Framework to RPL
 JP> Expand acronym when first used (RPL)

    This section applies the assessments given in Section 6 to RPL
 JP> Ad reference (draft-ietf-roll-rpl)
  as an
    illustration of the application of the LLN security framework.

    Specializing the approach used in Section 3.1, Figure 3 gives a
    level-1 data flow diagram representation of RPL to show the routing
    "assets" and "points of access" that may be vulnerable and need to be
    protected.

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                     ............................................
                     :                                          :
       |Link-Local   :                                          :
        Multicast    :                                          :
        or Node_i|<----->(DIO/DIS/DAO)<--------------+          :
                     :          ^                    |          :
                     :          |              ______V______    :
                     :          |              Candidate        :
                     :          V              Neighbor List    :
                     : (RPL Control incl.      ------+------    :
                     :  Trickle Timer,               |          :
                     :  Loop Avoidance)              V          :
                     :          ^            (Route Generation) :
                     :          |                    |          :
                     :          |              ______V______    :
                     :          +------+       Routing Table    :
                     :                 |       ------+------    :
                     :                 |             |          :
                     : RPL on Node_j   |             |          :
                     ..................|.............|...........
                                       |             |
       |Forwarding                     V             |
        To/From Node_k|<-------->(Read/Write         |
                                  Flow Label)<-------+

                     Figure 3: Data Flow Diagram of RPL

    From Figure 3, it is seen that threats to the proper operation of RPL
    are realized through attacks on its DIO, DIS, and DAO messages, as
    well as on the information the protocol places on the IPv6 Flow
    Labels.
 JP> Please update since information is now carried in the Hop-by-hop
 header
 with the RPL option (draft in 6man).
  As set forth in Section 6.1 to Section 6.4, the base
    security requirements concern message integrity, authenticity and
    liveliness of the principals of a connection, and protection against
    message replay; message encryption may be desirable.  The security
    objectives for RPL are therefore to ensure that

    1.  participants of the DIO, DIS, and DAO message exchanges are
        authentic;

    2.  the received DIO, DIS, and DAO messages are not modified during
        transportation;

    3.  the received DIO, DIS, and DAO messages are not retransmissions
        of previous messages;

    4.  the content of the DIO, DIS, and DAO messages may be made legible
        to only authorized entities.

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    In meeting the above objectives, RPL also needs to provide tunable
    mechanisms both to allow matching the security afforded to the
    application domain requirements and to enable efficient use of system
    resources, as discussed in Section 6.5.1 and Section 6.5.2.

    The functions of the different RPL messages and information placed
    within the user data plane Flow Labels
 JP> s/"user data plane"/"user data plane (RPL option TLV carried in the
 IPv6 Hop-by-hop header)
 are factors that can be taken
    into account when deciding the optional security features and levels
    of strength to be afforded.  For example, the DIO messages build
    routes to roots while the DAO messages support the building of
    downward routes to leaf nodes.  Consequently, there may be
    application environments in which the directions of the routes have
    different importance and thus warrant the use of different security
    features and/or strength.  In other words, it may be desirable to
    have an RPL security design that extends the tunability of the
    security features and strengths to message types.  The use of a per-
    message security specification will allow flexibility in permitting
    application-domain security choices as well as overall tunability.

 8.  IANA Considerations

    This memo includes no request to IANA.

 9.  Security Considerations

    The framework presented in this document provides security analysis
    and design guidelines with a scope limited to ROLL.  Security
    services are identified as requirements for securing ROLL.  The
    results are applied to RPL, with consequent recommendations.

 10.  Acknowledgments

    The authors would like to acknowledge the review and comments from
    Rene Struik.

 11.  References

 11.1.  Normative References

    [RFC2080]  Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
               January 1997.

    [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

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    [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

    [RFC2453]  Malkin, G., "RIP Version 2", STD 56, RFC 2453,
               November 1998.

    [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
               Internet Protocol", RFC 4301, December 2005.

 11.2.  Informative References

    [Huang2003]
               Huang, Q., Cukier, J., Kobayashi, H., Liu, B., and J.
               Zhang, "Fast Authenticated Key Establishment Protocols for
               Self-Organizing Sensor Networks", in Proceedings of the
               2nd ACM International Conference on Wireless Sensor
               Networks and Applications, San Diego, CA, USA, pp. 141-
               150, Sept. 19 2003.

    [I-D.ietf-roll-building-routing-reqs]
               Martocci, J., Riou, N., Mil, P., and W. Vermeylen,
               "Building Automation Routing Requirements in Low Power and
               Lossy Networks", draft-ietf-roll-building-routing-reqs-09
               (work in progress), January 2010.

    [I-D.ietf-roll-home-routing-reqs]
               Brandt, A. and J. Buron, "Home Automation Routing
               Requirements in Low Power and Lossy Networks",
               draft-ietf-roll-home-routing-reqs-11 (work in progress),
               January 2010.

 JP> Update the two references above.
    [I-D.ietf-roll-rpl]
               Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing
               Protocol for Low power and Lossy Networks",
               draft-ietf-roll-rpl-07 (work in progress), March 2010.

    [I-D.ietf-roll-terminology]
               Vasseur, J., "Terminology in Low power And Lossy
               Networks", draft-ietf-roll-terminology-03 (work in
               progress), March 2010.

    [I-D.suhopark-hello-wsn]
               Park, S., "Routing Security in Sensor Network: HELLO Flood
               Attack and Defense", draft-suhopark-hello-wsn-00 (work in
               progress), December 2005.

    [Karlof2003]
               Karlof, C. and D. Wagner, "Secure routing in wireless
               sensor networks: attacks and countermeasures", Elsevier

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               AdHoc Networks Journal, Special Issue on Sensor Network
               Applications and Protocols, 1(2):293-315, September 2003.

    [Messerges2003]
               Messerges, T., Cukier, J., Kevenaar, T., Puhl, L., Struik,
               R., and E. Callaway, "Low-Power Security for Wireless
               Sensor Networks", in Proceedings of the 1st ACM Workshop
               on Security of Ad Hoc and Sensor Networks, Fairfax, VA,
               USA, pp. 1-11, Oct. 31 2003.

    [Myagmar2005]
               Myagmar, S., Lee, AJ., and W. Yurcik, "Threat Modeling as
               a Basis for Security Requirements", in Proceedings of the
               Symposium on Requirements Engineering for Information
               Security (SREIS'05), Paris, France, pp. 94-102, Aug
               29, 2005.

    [RFC4593]  Barbir, A., Murphy, S., and Y. Yang, "Generic Threats to
               Routing Protocols", RFC 4593, October 2006.

    [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
               RFC 4949, August 2007.

    [RFC5548]  Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
               "Routing Requirements for Urban Low-Power and Lossy
               Networks", RFC 5548, May 2009.

    [RFC5673]  Pister, K., Thubert, P., Dwars, S., and T. Phinney,
               "Industrial Routing Requirements in Low-Power and Lossy
               Networks", RFC 5673, October 2009.

    [Wan2004]  Wan, T., Kranakis, E., and PC. van Oorschot, "S-RIP: A
               Secure Distance Vector Routing Protocol", in Proceedings
               of the 2nd International Conference on Applied
               Cryptography and Network Security, Yellow Mountain, China,
               pp. 103-119, Jun. 8-11 2004.

 Authors' Addresses

    Tzeta Tsao (editor)
    Eka Systems
    20201 Century Blvd. Suite 250
    Germantown, Maryland  20874
    USA

    Email: [email-masked]

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    Roger K. Alexander (editor)
    Eka Systems
    20201 Century Blvd. Suite 250
    Germantown, Maryland  20874
    USA

    Email: [email-masked]

    Mischa Dohler (editor)
    CTTC
    Parc Mediterrani de la Tecnologia, Av. Canal Olimpic S/N
    Castelldefels, Barcelona  08860
    Spain

    Email: [email-masked]

    Vanesa Daza (editor)
    Universitat Pompeu Fabra
    P/ Circumval.lacio 8, Oficina 308
    Barcelona  08003
    Spain

    Email: [email-masked]

    Angel Lozano (editor)
    Universitat Pompeu Fabra
    P/ Circumval.lacio 8, Oficina 309
    Barcelona  08003
    Spain

    Email: [email-masked]

 JP> Are you all editors ? if so, remove the term "Editors"

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--

Comment:

 Dear authors,

 Thanks (ticket#77).  Thanks for having addressed my comments. Ticket can
 be closed.

 JP.

-- 
--------------------------------+-------------------------------------------
 Reporter:  jpv@…               |        Owner:  tzeta.tsao@…                                            
     Type:  defect              |       Status:  closed                                                  
 Priority:  major               |    Milestone:                                                          
Component:  security-framework  |      Version:                                                          
 Severity:  In WG Last Call     |   Resolution:  fixed                                                   
 Keywords:                      |  
--------------------------------+-------------------------------------------

Ticket URL: <https://svn.tools.ietf.org/wg/roll/trac/ticket/77#comment:1>
roll <http://tools.ietf.org/wg/roll/>