BGP - Link State (BGP-LS) Extensions for Seamless Bidirectional Forwarding Detection (S-BFD)HuaweiHuawei Bld.No.156 Beiqing Rd.Beijing100095Chinalizhenbin@huawei.comHuaweiHuawei Bld.No.156 Beiqing Rd.Beijing100095Chinazhuangshunwan@huawei.comArrcus, Inc.Indiaketant.ietf@gmail.comGoogle, Inc.aldrin.ietf@gmail.comMicrosoftjefftant.ietf@gmail.comEricssongregimirsky@gmail.com
rtg
idrBGP-LSBFDIS-ISOSPFOSPFv3Seamless Bidirectional Forwarding Detection (S-BFD) defines a
simplified mechanism to use Bidirectional Forwarding Detection (BFD)
with large portions of negotiation aspects eliminated, thus providing
benefits such as quick provisioning as well as improved control and
flexibility to network nodes initiating the path monitoring. The
link-state routing protocols (IS-IS and OSPF) have been extended to
advertise the S-BFD Discriminators.This document defines extensions to the BGP - Link State (BGP-LS) address family
to carry the S-BFD Discriminators' information via BGP.Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
.
Copyright Notice
Copyright (c) 2022 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
() in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Revised BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Revised BSD License.
Table of Contents
. Introduction
. Terminology
. Requirements Language
. BGP-LS Extensions for S-BFD Discriminators
. IANA Considerations
. Manageability Considerations
. Security Considerations
. References
. Normative References
. Informative References
Acknowledgements
Authors' Addresses
IntroductionSeamless Bidirectional Forwarding Detection (S-BFD) defines a simplified mechanism to use Bidirectional
Forwarding Detection (BFD) with large portions
of negotiation aspects eliminated, thus providing benefits such as quick
provisioning as well as improved control and flexibility to network
nodes initiating the path monitoring.For the monitoring of a service path end to end via S-BFD, the headend
node (i.e., Initiator) needs to know the S-BFD Discriminator of the
destination/tail-end node (i.e., Responder) of that service. The
link-state routing protocols (IS-IS and OSPF
) have been extended to advertise the S-BFD
Discriminators. With this, an Initiator can learn the S-BFD
Discriminator for all Responders within its IGP area/level or
optionally within the domain. With networks being divided into multiple
IGP domains for scaling and operational considerations, the service
endpoints that require end-to-end S-BFD monitoring often span across IGP
domains.BGP - Link State (BGP-LS) enables the
collection and distribution of IGP link-state topology information via
BGP sessions across IGP areas/levels and domains. The S-BFD
Discriminator(s) of a node can thus be distributed along with the
topology information via BGP-LS across IGP domains and even across
multiple Autonomous Systems (ASes) within an administrative domain.This document defines extensions to BGP-LS for carrying the S-BFD
Discriminators' information.TerminologyThis memo makes use of the terms defined in .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 BCP 14
when, and only when, they appear in all capitals, as shown here.
BGP-LS Extensions for S-BFD DiscriminatorsBGP-LS specifies the Node Network Layer
Reachability Information (NLRI) for the advertisement of nodes and their
attributes using the BGP-LS Attribute. The S-BFD Discriminators of a
node are considered a node-level attribute and are advertised as such.This document defines a new BGP-LS Attribute TLV called "S-BFD
Discriminators TLV", and its format is as follows:S-BFD Discriminators TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator 2 (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator n (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type:
1032
Length:
variable. It MUST be a minimum of 4 octets, and it increments
by 4 octets for each additional discriminator.
Discriminator n:
4 octets each, carrying an S-BFD local discriminator value of the node. At
least one discriminator MUST be included in the TLV.
The S-BFD Discriminators TLV can be added to the BGP-LS Attribute
associated with the Node NLRI that originates the corresponding
underlying IGP TLV/sub-TLV as described below. This information is
derived from the protocol-specific advertisements as follows:
IS-IS, as defined by the S-BFD Discriminators sub-TLV in .
OSPFv2/OSPFv3, as defined by the S-BFD Discriminator TLV in .
IANA ConsiderationsIANA has permanently allocated the following code point
in the "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor,
and Attribute TLVs" registry. The column "IS-IS TLV/Sub-TLV" defined in
the registry does not require any value and should be left empty.
S-BFD Discriminators TLV Code Point Allocation
TLV Code Point
Description
Reference
1032
S-BFD Discriminators
This document
Manageability ConsiderationsThe new protocol extensions introduced in this document augment the
existing IGP topology information that was distributed via BGP-LS . Procedures and protocol extensions defined in this
document do not affect BGP protocol operations and management other
than as discussed in "Manageability Considerations" (Section ) of . Specifically, the malformed NLRIs attribute tests in
"Fault Management" (Section ) of now encompass
the new TLV for the BGP-LS NLRI in this document.Security ConsiderationsThe new protocol extensions introduced in this document augment the
existing IGP topology information that can be distributed via BGP-LS
. Procedures and protocol extensions defined in
this document do not affect the BGP security model other than as
discussed in "Security Considerations" (Section ) of , i.e., the aspects related to limiting
the nodes and consumers with which the topology information is shared
via BGP-LS to trusted entities within an administrative domain.The TLV introduced in this document is used to propagate IGP-defined
information (see and ). The
TLV represents information used to set up S-BFD sessions. The IGP
instances originating this information are assumed to support any
required security and authentication mechanisms (as described in and ).Advertising the S-BFD Discriminators via BGP-LS makes it possible for
attackers to initiate S-BFD sessions using the advertised information.
The vulnerabilities this poses and how to mitigate them are discussed in
.ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGPIn a number of environments, a component external to a network is called upon to perform computations based on the network topology and current state of the connections within the network, including Traffic Engineering (TE) information. This is information typically distributed by IGP routing protocols within the network.This document describes a mechanism by which link-state and TE information can be collected from networks and shared with external components using the BGP routing protocol. This is achieved using a new BGP Network Layer Reachability Information (NLRI) encoding format. The mechanism is applicable to physical and virtual IGP links. The mechanism described is subject to policy control.Applications of this technique include Application-Layer Traffic Optimization (ALTO) servers and Path Computation Elements (PCEs).Seamless Bidirectional Forwarding Detection (S-BFD)This document defines Seamless Bidirectional Forwarding Detection (S-BFD), a simplified mechanism for using BFD with a large proportion of negotiation aspects eliminated, thus providing benefits such as quick provisioning, as well as improved control and flexibility for network nodes initiating path monitoring.This document updates RFC 5880.Advertising Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators in IS-ISThis document defines a means of advertising one or more Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators using the IS-IS Router CAPABILITY TLV.OSPF Extensions to Advertise Seamless Bidirectional Forwarding Detection (S-BFD) Target DiscriminatorsThis document defines a new OSPF Router Information (RI) TLV that allows OSPF routers to flood the Seamless Bidirectional Forwarding Detection (S-BFD) Discriminator values associated with a target network identifier. This mechanism is applicable to both OSPFv2 and OSPFv3.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Informative ReferencesBidirectional Forwarding Detection (BFD)This document describes a protocol intended to detect faults in the bidirectional path between two forwarding engines, including interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency. It operates independently of media, data protocols, and routing protocols. [STANDARDS-TRACK]AcknowledgementsThe authors would like to thank for his
contributions to this work. The authors would also like to thank
and for their reviews as well as
for his shepherd review and for his AD review of this document.Authors' AddressesHuaweiHuawei Bld.No.156 Beiqing Rd.Beijing100095Chinalizhenbin@huawei.comHuaweiHuawei Bld.No.156 Beiqing Rd.Beijing100095Chinazhuangshunwan@huawei.comArrcus, Inc.Indiaketant.ietf@gmail.comGoogle, Inc.aldrin.ietf@gmail.comMicrosoftjefftant.ietf@gmail.comEricssongregimirsky@gmail.com