Google Inc.

Mountain View California 94043 United States of America psuthar@google.com

Cisco Systems Inc.

Naperville Illinois 60540 United States of America mistolic@cisco.com

Cisco Systems Inc.

San Jose California 95134 United States of America anjangam@cisco.com

Huawei Technologies

Riesstrasse 25 Munich 80992 Germany dirk.trossen@huawei.com

F5 Networks

3545 North First Street San Jose California 95134 United States of America r.ravindran@f5.com

Information-Centric Networking LTE ICN ICN-4G ICNoIP IPoICN HybridICN Dual Transport A 4G mobile network uses IP-based transport for the control plane to establish the data session at the user plane for the actual data delivery. In the existing architecture, IP-based unicast is used for the delivery of multimedia content to a mobile terminal, where each user is receiving a separate stream from the server. From a bandwidth and routing perspective, this approach is inefficient. Evolved multimedia broadcast and multicast service (eMBMS) provides capabilities for delivering contents to multiple users simultaneously, but its deployment is very limited or at an experimental stage due to numerous challenges. The focus of this document is to list the options for using Information-Centric Networking (ICN) in 4G mobile networks and elaborate the experimental setups for its further evaluation. The experimental setups discussed provide guidance for using ICN either natively or with an existing mobility protocol stack. With further investigations based on the listed experiments, ICN with its inherent capabilities such as network-layer multicast, anchorless mobility, security, and optimized data delivery using local caching at the edge may provide a viable alternative to IP transport in 4G mobile networks.

Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Research Task Force (IRTF). The IRTF publishes the results of Internet-related research and development activities. These results might not be suitable for deployment. This RFC represents the consensus of the Information-Centric Networking Research Group of the Internet Research Task Force (IRTF). Documents approved for publication by the IRSG are not candidates for any level of Internet Standard; see 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.

Table of Contents

• .  Introduction
• .  3GPP Terminology and Concepts
• .  4G Mobile Network Architecture
  • .  Network Overview
  • .  Mobile Network Quality of Service
  • .  Data Transport Using IP
  • .  Virtualized Mobile Networks
• .  Data Transport Using ICN
• .  Experimental Scenarios for ICN Deployment
  • .  General Considerations
  • .  Scenarios of ICN Integration
  • .  Integration of ICN in 4G Control Plane
  • .  Integration of ICN in 4G User Plane
    • .  Dual Transport (IP/ICN) Mode in Mobile Terminal
    • .  Using ICN in Mobile Terminal
    • .  Using ICN in eNodeB
    • .  Using ICN in Packet Core Gateways (SGW/PGW)
  • .  An Experimental Test Setup
• .  Expected Outcomes from Experimentation
  • .  Feeding into ICN Research
  • .  Use of Results Beyond Research
• .  IANA Considerations
• .  Security and Privacy Considerations
  • .  Security Considerations
  • .  Privacy Considerations
• .  Summary
• . References
  • .  Normative References
  • .  Informative References
• Acknowledgements
• Authors' Addresses

Introduction 4G mobile technology is built as an all-IP network using routing protocols (OSPF, IS-IS, BGP, etc.) to establish network routes. The stickiness of an IP address to a device is the key to getting connected to a mobile network. The same IP address is maintained through the session until the device gets detached or moves to another network. Key protocols used in 4G networks are the General Packet Radio Service Tunneling Protocol (GTP), DIAMETER, and other protocols that are built on top of IP. One of the biggest challenges with IP-based routing in 4G is that it is not optimized for data transport. As an alternative to IP routing, this document presents and lists the possible options for integration of Information-Centric Networking (ICN) in 3GPP 4G mobile networks, offering an opportunity to leverage inherent ICN capabilities such as in-network caching, multicast, anchorless mobility management, and authentication. This document also discusses how those options affect mobile providers and end users. The goal of the proposed experiments is to present possibilities to create simulated environments for evaluation of the benefits of ICN protocol deployment in a 4G mobile network in different scenarios that have been analyzed in this document. The consensus of the Information-Centric Networking Research Group (ICNRG) is to publish this document in order to facilitate experiments to show deployment options and qualitative and quantitative benefits of ICN protocol deployment in 4G mobile networks.

3GPP Terminology and Concepts

Access Point Name:

The Access Point Name (APN) is a Fully Qualified Domain Name (FQDN) and resolves to a set of gateways in an operator's network. An APN identifies the packet data network (PDN) with which a mobile data user wants to communicate. In addition to identifying a PDN, an APN may also be used to define the type of service, QoS, and other logical entities inside a Gateway General Packet Radio Service Support Node (GGSN) or a Packet Data Network Gateway (PGW).

Control Plane:

The control plane carries signaling traffic and is responsible for routing between the eNodeB and the Mobile Management Entity (MME), the MME and the Home Subscriber Server (HSS), the MME and the Mobile Gateways (SGW/PGW), etc. Control plane signaling is required to authenticate and authorize the mobile terminal and establish a mobility session with Mobile Gateways (SGW/PGW). Control plane functions also include system configuration and management.

Dual Address PDN/PDP Type:

The dual address Packet Data Network / Packet Data Protocol (PDN/PDP) Type (IPv4v6) is used in 3GPP context, in many cases as a synonym for dual stack, i.e., a connection type capable of serving IPv4 and IPv6 simultaneously.

eNodeB:

The eNodeB is a base station entity that supports the Long Term Evolution (LTE) air interface.

Evolved Packet Core:

The Evolved Packet Core (EPC) is an evolution of the 3GPP GPRS system characterized by a higher-data-rate, lower-latency, packet-optimized system. The EPC comprises some subcomponents of the EPS core such as MME, Mobile Gateways (SGW/PGW), and HSS.

Evolved Packet System:

The Evolved Packet System (EPS) is an evolution of the 3GPP GPRS system characterized by a higher-data-rate, lower-latency, packet-optimized system that supports multiple Radio Access Technologies (RATs). The EPS comprises the EPC together with Evolved Universal Terrestrial Radio Access (E-UTRA) and the Evolved Universal Terrestrial Radio Access Network (E-UTRAN).

Evolved UTRAN:

The Evolved UTRAN (E-UTRAN) is a communications network sometimes referred to as 4G, and it consists of an eNodeB (4G base stations). The E-UTRAN allows connectivity between the User Equipment and the core network.

Gateway GPRS Support Node:

The Gateway GPRS Support Node (GGSN) is a gateway function in the GPRS and 3G network that provides connectivity to the Internet or other PDNs. The host attaches to a GGSN identified by an APN that is assigned to it by an operator. The GGSN also serves as the topological anchor for addresses/prefixes assigned to the User Equipment.

General Packet Radio Service:

The General Packet Radio Service (GPRS) is a packet-oriented mobile data service available to users of the 2G and 3G cellular communication systems (the GSM) specified by 3GPP.

GPRS Tunneling Protocol:

The GPRS Tunneling Protocol (GTP) is a tunneling protocol defined by 3GPP. It is a network-based mobility protocol that works similarly to Proxy Mobile IPv6 (PMIPv6). However, GTP also provides functionality beyond mobility, such as in-band signaling related to QoS and charging, among others.

Home Subscriber Server:

The Home Subscriber Server (HSS) is a database for a given subscriber and was introduced in 3GPP Release 5. It is the entity containing subscription-related information to support the network entities that handle calls/sessions.

Mobile Terminal/User Equipment:

The terms User Equipment (UE), Mobile Station (MS), Mobile Node (MN), and mobile refer to the devices that are hosts with the ability to obtain Internet connectivity via a 3GPP network. An MS comprises the Terminal Equipment (TE) and an MT. The terms MT, MS, MN, and mobile are used interchangeably within this document.

Mobility Management Entity:

The Mobility Management Entity (MME) is a network element responsible for control plane functionalities, including authentication, authorization, bearer management, Layer 2 mobility, and so on. The MME is essentially the control plane part of the SGSN in the GPRS. The user-plane traffic bypasses the MME.

Packet Data Network:

The Packet Data Network (PDN) is a packet-based network that either belongs to the operator or is an external network such as the Internet or a corporate intranet. The user eventually accesses services in one or more PDNs. The operator's packet core networks are separated from packet data networks by either GGSNs or PGWs.

Packet Data Network Gateway:

The Packet Data Network Gateway (PGW) is a gateway function in the EPS, which provides connectivity to the Internet or other PDNs. The host attaches to a PGW identified by an APN that is assigned to it by an operator. The PGW also serves as the topological anchor for addresses/prefixes assigned to the User Equipment.

Packet Data Protocol Context:

A Packet Data Protocol (PDP) context is the equivalent of a virtual connection between the mobile terminal (MT) and a PDN using a specific gateway.

Packet Data Protocol Type:

A Packet Data Protocol Type (PDP Type) identifies the used/allowed protocols within the PDP context. Examples are IPv4, IPv6, and IPv4v6 (dual stack).

Policy and Charging Control:

The Policy and Charging Control (PCC) framework is used for QoS policy and charging control. It has two main functions: flow-based charging (including online credit control) and policy control (for example, gating control, QoS control, and QoS signaling). It is optional to 3GPP EPS but needed if dynamic policy and charging control by means of PCC rules based on user and services are desired.

Public Land Mobile Network:

The Public Land Mobile Network (PLMN) is a network operated by a single administration. A PLMN (and therefore also an operator) is identified by the Mobile Country Code (MCC) and the Mobile Network Code (MNC). Each (telecommunications) operator providing mobile services has its own PLMN.

Serving Gateway:

The Serving Gateway (SGW) is a gateway function in the EPS, which terminates the interface towards the E-UTRAN. The SGW is the Mobility Anchor point for Layer 2 mobility (inter-eNodeB handovers). For each mobile terminal connected with the EPS, there is only one SGW at any given point in time. The SGW is essentially the user-plane part of the GPRS's SGSN.

Serving GPRS Support Node:

The Serving GPRS Support Node (SGSN) is a network element located between the Radio Access Network (RAN) and the gateway (GGSN). A per-MT point-to-point (P2P) tunnel between the GGSN and SGSN transports the packets between the mobile terminal and the gateway.

User Plane:

The user plane refers to data traffic and the required bearers for the data traffic. In practice, IP is the only data traffic protocol used in the user plane.

4G Mobile Network Architecture This section provides a high-level overview of typical 4G mobile network architecture and the key functions related to the possibility of its use with ICN technology.

Network Overview 4G mobile networks are designed to use IP transport for communication among different elements such as the eNodeB, MME, SGW, PGW, HSS, Policy and Charging Rule Function (PCRF), etc. . For backward compatibility with 3G, it has support for legacy circuit switch features such as voice and SMS through transitional CS fallback and flexible IP Multimedia Subsystems (IMS) deployment. For each mobile device attached to the radio (eNodeB), there is a separate overlay tunnel (GTP) between the eNodeB and Mobile Gateways (i.e., SGW/PGW). When any mobile terminal is powered up, it attaches to a mobile network based on its configuration and subscription. After a successful attachment procedure, the mobile terminal registers with the mobile core network using IPv4 and/or IPv6 addresses based on request and capabilities offered by Mobile Gateways. The GTP tunnel is used to carry user traffic between gateways and mobile terminals, therefore using the unicast delivery for any data transfer. It is also important to understand the overhead of GTP and IPsec protocols. All mobile backhaul traffic is encapsulated using a GTP tunnel, which has overhead of 8 bytes on top of IP and UDP . Additionally, if IPsec is used for security (which is often required if the Service Provider is using a shared backhaul), it adds overhead based on the IPsec tunneling model (tunnel or transport) as well as the encryption and authentication header algorithm used. If we consider an Advanced Encryption Standard (AES) encryption as an example, the overhead can be significant , particularly for smaller payloads.

4G Mobile Network Overview +-------+ Diameter +-------+ | HSS |------------| SPR | +-------+ +-------+ | | +------+ +------+ S4 | +-------+ | 3G |---| SGSN |----------------|------+ +------| PCRF | ^ |NodeB | | |---------+ +---+ | | +-------+ +-+ | +------+ +------+ S3 | | S6a | |Gxc | | | | +-------+ | | |Gx +-+ | +------------------| MME |------+ | | | MT v | S1MME +-------+ S11 | | | | +----+-+ +-------+ +-------+ |4G/LTE|------------------------------| SGW |-----| PGW | |eNodeB| S1U +-------+ +--| | +------+ | +-------+ +---------------------+ | | S1U GTP Tunnel traffic | +-------+ | | S2a GRE Tunnel traffic |S2A | ePDG |-------+ | S2b GRE Tunnel traffic | +-------+ S2B |SGi SGi IP traffic | | | +---------+ +---------+ +-----+ | Trusted | |Untrusted| | CDN | |non-3GPP | |non-3GPP | +-----+ +---------+ +---------+ | | +-+ +-+ | | | | +-+ +-+ MT MT

If we consider the combined impact of GTP, IPsec, and unicast traffic, the data delivery is not efficient because of overhead. The IETF has developed various header compression algorithms to reduce the overhead associated with IP packets. Some techniques are RObust Header Compression (ROHC) and Enhanced Compression RTP (ECRTP) so that the impact of overhead created by GTP, IPsec, etc., is reduced to some extent . For commercial mobile networks, 3GPP has adopted different mechanisms for header compression to achieve efficiency in data delivery ; those solutions can be adapted to other data protocols too such as ICN .

Mobile Network Quality of Service During the mobile terminal attachment procedure, a default bearer is created for each mobile terminal and it is assigned to the default Access Point Name (APN), which provides the default transport. For any QoS-aware application, one or more new dedicated bearers are established between an eNodeB and a Mobile Gateway. A dedicated bearer can be requested by either a mobile terminal or a Mobile Gateway based on the direction of the first data flow. There are many bearers (logical paths) established between an eNodeB and a Mobile Gateway for each mobile terminal catering to a different data flow simultaneously. While all traffic within a certain bearer receives the same treatment, QoS parameters supporting these requirements can be very granular in different bearers. These values vary for the control, management, and user traffic, and can be very different depending on application key parameters such as latency, jitter (important for voice and other real-time applications), packet loss, and queuing mechanism (strict priority, low latency, fair, and so on). Implementation of QoS for mobile networks is done at two stages: 1) content prioritization/marking and transport marking and 2) congestion management. From the transport perspective, QoS is defined at Layer 2 as Class of Service (CoS) and at Layer 3 as Differentiated Services (DS). The mapping of the Differentiated Services Code Point (DSCP) to CoS takes place at Layer 2/3 switching and routing elements. 3GPP has a specified QoS Class Identifier (QCI), which represents different types of content and equivalent mappings to the DSCP at the transport layer . However, this requires manual configuration at different elements and is therefore prone to possible misconfigurations. In summary, QoS configuration in mobile networks for user-plane traffic requires synchronization of parameters among different platforms. Normally, QoS in IP is implemented using DiffServ, which uses hop-by-hop QoS configuration at each router. Any inconsistency in IP QoS configuration at routers in the forwarding path can result in a poor subscriber experience (e.g., a packet classified as high priority can go to a lower-priority queue). By deploying ICN, we intend to enhance the subscriber experience using policy-based configuration, which can be associated with the named contents at the ICN forwarder. Further investigation is underway to understand how QoS in ICN can be implemented with reference to the ICN QoS guidelines to meet the QoS requirements .

Data Transport Using IP The data delivered to mobile devices is sent in unicast semantic inside the GTP tunnel from an eNodeB to a PDN gateway (PGW) as described in 3GPP specifications . While the technology exists to address the issue of possible multicast delivery, there are many difficulties related to multicast protocol implementations on the RAN side of the network. By using eMBMS , multicast routing can be enabled in mobile backhaul between an eNodeB and Mobile Gateways (SGW/PGW); however, for radio interface it requires broadcast, which implies that we need a dedicated radio channel. Implementation of eMBMS in RAN is still lagging behind due to complexities related to client mobility, handovers, and the fact that the potential gain to Service Providers may not justify the investment, which explains the prevalence of unicast delivery in mobile networks. Techniques to handle multicast (such as LTE-B or eMBMS) have been designed to handle pre-planned content delivery, such as live content, which contrasts user behavior today, largely based on a content (or video) on-demand model. To ease the burden on the bandwidth of the Service Gateway interface (SGi), caching is introduced in a similar manner as with many enterprises. In mobile networks, whenever possible, cached data is delivered. Caching servers are placed at a centralized location, typically in the Service Provider's Data Center, or in some cases lightly distributed in packet core locations with the PGW nodes close to the Internet and IP services access (SGi). This is a very inefficient concept because traffic must traverse the entire backhaul path for the data to be delivered to the end user. Other issues, such as out-of-order delivery, contribute to this complexity and inefficiency, which needs to be addressed at the application level.

Virtualized Mobile Networks The Mobile Gateways deployed in a major Service Provider network are based on either dedicated hardware or commercial off-the-shelf (COTS) x86 technology. With the adoption of Mobile Virtual Network Operators (MVNOs), public safety networks, and enterprise mobility networks, elastic mobile core architecture is needed. By deploying the mobile packet core on a COTS platform, using a Network Function Virtualization Infrastructure (NFVI) framework and end-to-end orchestration, new deployments can be simplified to provide optimized total cost of ownership (TCO). While virtualization is growing, and many mobile providers use a hybrid architecture that consists of dedicated and virtualized infrastructures, the control and data planes are still the same. There is also work underway to separate the control and user plane for the network to scale better. Virtualized mobile networks and network slicing with control and user-plane separation provide a mechanism to evolve the GTP-based architecture towards an OpenFlow with signaling based on Software-Defined Networking (SDN) for 4G and proposed 5G core. Some early architecture work for 5G mobile technologies provides a mechanism for control and user-plane separation and simplifies the mobility call flow by introducing OpenFlow-based signaling . This has been considered by 3GPP and is also described in .

Data Transport Using ICN For mobile devices, the edge connectivity is between a mobile terminal and a router or mobile edge computing (MEC) element. Edge computing has the capability of processing client requests and segregating control and user traffic at the edge of radio rather than sending all requests to the Mobile Gateway.

ICN Architecture +----------+ | Content +----------------------------------------+ | Publisher| | +---+---+--+ | | | +--+ +--+ +--+ | | +--->|R1|------------>|R2|---------->|R4| | | +--+ +--+ +--+ | | | Cached | | v content | | +--+ at R3 | | +========|R3|---+ | | # +--+ | | | # | | | v v | | +-+ +-+ | +---------------| |-------------| |-------------+ +-+ +-+ Consumer-1 Consumer-2 Mobile Terminal Mobile Terminal ===> Content flow from cache ---> Content flow from publisher

Edge computing transforms a Radio Access Network into an intelligent service edge capable of delivering services directly from the edge of the network while providing the best possible performance to the client. Edge computing can be an ideal candidate for implementing ICN forwarders in addition to its usual function of managing mobile termination. In addition to edge computing, other transport elements, such as routers, can work as ICN forwarders. Data transport using ICN is different than IP-based transport as it introduces uniquely named-data as a core design principle. Communication in ICN takes place between the content provider (producer) and the end user (consumer), as described in . Every node in a physical path between a client and a content provider is called the ICN forwarder or router. It can route the request intelligently and cache content so it can be delivered locally for subsequent requests from any other client. For mobile networks, transport between a client and a content provider consists of a radio network + mobile backhaul and IP core transport + Mobile Gateways + Internet + Content Delivery Network (CDN). To understand the suitability of ICN for mobile networks, we will discuss the ICN framework by describing its protocol architecture and different types of messages; this will be helpful when considering how to use ICN in mobile networks to deliver content more efficiently. ICN uses two types of packets called "interest packet" and "data packet" as described in .

ICN Interest, Data Packet, and Forwarder +------------------------------------+ Interest | +------+ +------+ +------+ | +-----+ +-+ ---->| CS |---->| PIT |---->| FIB |--------->| CDN | | | | +------+ +------+ +------+ | +-----+ +-+ | | Add | Drop | | Forward MT <--------+ Intf v Nack v | Data | | +------------------------------------+ +------------------------------------+ +-+ | Forward +------+ | +-----+ | | <-------------------------------------| PIT |<---------| CDN | +-+ | | Cache +--+---+ | Data +-----+ MT | +--v---+ | | | | CS | v | | +------+ Discard | +------------------------------------+

In a 4G network, when a mobile device wants to receive certain content, it will send an Interest message to the closest eNodeB. Interest packets follow the TLV format and contain mandatory fields such as the name of the content and content-matching restrictions (KeyIdRestr and ContentObjectHashRestr) expressed as a tuple . The content-matching tuple uniquely identifies the matching data packet for the given Interest packet. Another attribute called "HopLimit" is used to detect looping Interest messages. An ICN router will receive an Interest packet and lookup if a request for such content has arrived earlier from another client. If so, it may be served from the local cache; otherwise, the request is forwarded to the next-hop ICN router. Each ICN router maintains three data structures: Pending Interest Table (PIT), Forwarding Information Base (FIB), and Content Store (CS). The Interest packet travels hop by hop towards the content provider. Once the Interest packet reaches the content provider, it will return a data packet containing information such as content name, signature, and the actual data. The data packet travels in reverse direction following the same path taken by the Interest packet, maintaining routing symmetry. Details about algorithms used in PIT, FIB, CS, and security trust models are described in various resources ; here, we have explained the concept and its applicability to the 4G network.

Experimental Scenarios for ICN Deployment In 4G mobile networks, both user and control plane traffic have to be transported from the edge to the mobile packet core via IP transport. The evolution of the existing mobile packet core using Control and User Plane Separation (CUPS) enables flexible networking and operations by distributed deployment and the independent scaling of control plane and user-plane functions while not affecting the functionality of existing nodes subject to this split. In this section, we analyze the potential impact of ICN on control and user-plane traffic for centralized and disaggregated CUPS-based mobile network architecture. We list various experimental options and opportunities to study the feasibility of the deployment of ICN in 4G networks. The proposed experiments would help the network and original equipment manufacturer (OEM) designers to understand various issues, optimizations, and advantages of the deployment of ICN in 4G networks.

General Considerations In the CUPS architecture, there is an opportunity to shorten the path for user-plane traffic by deploying offload nodes closer to the edge . With this major architecture change, a User Plane Function (UPF) node is placed close to the edge so traffic no longer needs to traverse the entire backhaul path to reach the EPC. In many cases, where feasible, the UPF can be collocated with the eNodeB, which is also a business decision based on user demand. Placing a Publisher close to the offload site, or at the offload site, provides for a significant improvement in user experience, especially with latency-sensitive applications. This capability allows for the introduction of ICN and amplifies its advantages.

Scenarios of ICN Integration The integration of ICN provides an opportunity to further optimize the existing data transport in 4G mobile networks. The various opportunities from the coexistence of ICN and IP transport in the mobile network are somewhat analogous to the deployment scenarios when IPv6 was introduced to interoperate with IPv4 except, with ICN, the whole IP stack can be replaced. We have reviewed and analyzed the impact of ICN on control plane signaling and user-plane data delivery. In general, ICN can be used natively by replacing IP transport (IPv4 and IPv6) or as an overlay protocol. describes a proposal to modify the existing transport protocol stack to support ICN in a 4G mobile network.

IP/ICN Convergence Scenarios +----------------+ +-----------------+ | ICN App (new) | |IP App (existing)| +---------+------+ +-------+---------+ | | +---------+----------------+---------+ | Transport Convergence Layer (new) | +------+---------------------+-------+ | | +------+------+ +------+-------+ |ICN function | | IP function | | (New) | | (Existing) | +------+------+ +------+-------+ | | (```). (```). ( ICN '`. ( IP '`. ( Cloud ) ( Cloud ) ` __..'+' ` __..'+'

As shown in , for applications (running either in the mobile terminal or in the content provider system) to use the ICN transport option, we propose a new transport convergence layer (TCL). The TCL helps determine the type of transport (such as ICN or IP) as well as the type of radio interface (LTE, Wi-Fi, or both) used to send and receive traffic based on preference (e.g., content location, content type, content publisher, congestion, cost, or QoS). It helps configure and determine the type of connection (native IP or ICN) or the overlay mode (ICNoIP or IPoICN) between application and the protocol stack (IP or ICN). Combined with the existing IP function, the ICN function provides support for native ICN and/or the dual transport (ICN/IP) functionality. See for elaborate descriptions of these functional layers. The TCL can use several mechanisms for transport selection. It can use a per-application configuration through a management interface, possibly a user-facing setting realized through a user interface, like those used to select cellular over Wi-Fi. In another option, it might use a software API, which an adapted IP application could use to specify the type of transport option (such as ICN) to take advantage of its benefits. Another potential application of TCL is in an implementation of network slicing with a local slice management capability or through an interface to an external slice manager via an API . This solution can enable network slicing for IP and ICN transport selection from the mobile terminal itself. The TCL could apply slice settings to direct certain applications traffic over one slice and others over another slice, determined by some form of a 'slicing policy'. The slicing policy can be obtained externally from the slice manager or configured locally on the mobile terminal. From the perspective of applications either on the mobile terminal or at a content provider, the following options are possible for potential use of ICN natively and/or with IP.

IP over IP (IPoIP):

In this scenario, the mobile terminal applications are tightly integrated with the existing IP transport infrastructure. The TCL has no additional function because packets are forwarded directly using an IP protocol stack, which sends packets over the IP transport.

ICN over ICN (ICNoICN):

Similar to case 1, ICN applications tightly integrate with the ICN transport infrastructure. The TCL has no additional responsibility because packets are forwarded directly using the native ICN protocol stack, which sends packets over the ICN transport.

ICN over IP (ICNoIP):

In this scenario, the underlying IP transport infrastructure is not impacted (that is, ICN is implemented as an IP overlay between mobile terminal and content provider). IP routing is used from the Radio Access Network (eNodeB) to the mobile backhaul, the IP core, and the Mobile Gateway (SGW/PGW). The mobile terminal attaches to the Mobile Gateway (SGW/PGW) using an IP address. Also, the data transport between Mobile Gateway (SGW/PGW) and content publisher uses IP. The content provider can serve content using either IP or ICN, based on the mobile terminal request. One of the approaches to implement ICN in mobile backhaul networks is described in . It implements a General Tunneling Protocol - User Plane (GTP-U) extension header option to encapsulate ICN payload in a GTP tunnel. However, as this design runs ICN as an IP overlay, the mobile backhaul can be deployed using native IP. The proposal describes a mechanism where the GTP-U tunnel can be terminated by hairpinning the packet before it reaches the SGW if an ICN-enabled node is deployed in the mobile backhaul (that is, between eNodeB and SGW). This could be useful when an ICN data packet is stored in the ICN node (such as repositories and caches) in the tunnel path so that the ICN node can reply without going all the way through the mobile core. While a GTP-U extension header is used to carry mobile-terminal-specific ICN payload, they are not visible to the transport, including the SGW. On the other hand, the PGW can use the mobile terminal-specific ICN header extension and ICN payload to set up an uplink transport towards a content provider in the Internet. In addition, the design assumes a proxy function at the edge to perform ICN data retrieval on behalf of a non-ICN end device.

IP over ICN (IPoICN):

provides an architectural framework for running IP as an overlay over the ICN protocol. Implementing IP services over ICN provides an opportunity to leverage the benefits of ICN in the transport infrastructure while there is no impact on end devices (MT and access network) as they continue to use IP. IPoICN, however, will require an interworking function (IWF) (and Border Gateway) to translate various transport primitives. The IWF function will provide a mechanism for protocol translation between IPoICN and the native IP. After reviewing , we understand and interpret that ICN is implemented in the transport natively; however, IP is implemented in MT, the eNodeB, and the Mobile Gateway (SGW/PGW), which is also called a network attach point (NAP). For this, said NAP receives an incoming IP or HTTP packet (the latter through TCP connection termination) and publishes the packet under a suitable ICN name (i.e., the hash over the destination IP address for an IP packet or the hash over the FQDN of the HTTP request for an HTTP packet) to the ICN network. In the HTTP case, the NAP maintains a pending request mapping table to map returning responses to the terminated TCP connection.

Hybrid ICN (hICN):

An alternative approach to implement ICN over IP is provided in Hybrid ICN . It describes a novel approach to integrate ICN into IPv6 without creating overlays with a new packet format as an encapsulation. hICN addresses the content by encoding a location-independent name in an IPv6 address. It uses two name components, name prefix and name suffix, that identify the source of data and the data segment within the scope of the name prefix, respectively. At the application layer, hICN maps the name into an IPv6 prefix and, thus, uses IP as transport. As long as the name prefixes, which are routable IP prefixes, point towards a mobile GW (PGW or local breakout, such as CUPS), there are potentially no updates required to any of the mobile core gateways (for example, SGW/PGW). The IPv6 backhaul routes the packets within the mobile core. hICN can run in the mobile terminal, the eNodeB, the mobile backhaul, or the mobile core. Finally, as hICN itself uses IPv6, it cannot be considered as an alternative transport layer.

Integration of ICN in 4G Control Plane In this section, we analyze signaling messages that are required for different procedures, such as attach, handover, tracking area update, and so on. The goal of this analysis is to see if there are any benefits to replacing IP-based protocols with ICN for 4G signaling in the current architecture. It is important to understand the concept of point of attachment (POA). When a mobile terminal connects to a network, it has the following POAs:

1. eNodeB managing location or physical POA
2. Authentication and Authorization (MME, HSS) managing identity or authentication POA
3. Mobile Gateways (SGW/PGW) managing logical or session management POA

In the current architecture, IP transport is used for all messages associated with the control plane for mobility and session management. IP is embedded very deeply into these messages utilizing TLV syntax for carrying additional attributes such as a Layer 3 transport. The physical POA in the eNodeB handles both mobility and session management for any mobile terminal attached to a 4G network. The number of mobility management messages between different nodes in a 4G network per the signaling procedure is shown in . Normally, two types of mobile terminals attach to the 4G network: SIM based (which needs a 3GPP mobility protocol for authentication) or non-SIM based (which connects to Wi-Fi networks). Both device types require authentication. For non-SIM based devices, Authentication, Authorization, and Accounting (AAA) is used for authentication. We do not propose to change mobile terminal authentication or mobility management messaging for user data transport using ICN. A separate study would be required to analyze the impact of ICN on mobility management messages, structures, and flows. We are merely analyzing the viability of implementing ICN as a transport for control plane messages. It is important to note that if MME and HSS do not support ICN transport, they still need to support a mobile terminal capable of dual transport or native ICN. When a mobile terminal initiates an attach request using the identity as ICN, MME must be able to parse that message and create a session. MME forwards mobile terminal authentication to HSS, so HSS must be able to authenticate an ICN-capable mobile terminal and authorize Create Session . Signaling Messages in 4G Gateways

4G Signaling Procedures	MME	HSS	SGW	PGW	PCRF
Attach	10	2	3	2	1
Additional default bearer	4	0	3	2	1
Dedicated bearer	2	0	2	2	0
Idle-to-connect	3	0	1	0	0
Connect-to-Idle	3	0	1	0	0
X2 handover	2	0	1	0	0
S1 handover	8	0	3	0	0
Tracking area update	2	2	0	0	0
Total	34	2	14	6	3

Anchorless mobility provides a fully decentralized solution that is control plane agnostic to handle producer mobility in ICN. Mobility management at the Layer 3 makes its access agnostic and transparent to the end device or the application. The solution discusses handling mobility without having to depend on core network functions (e.g., MME); however, a location update to the core network may still be required to support legal compliance requirements such as lawful intercept and emergency services. These aspects are open for further study. One of the advantages of ICN is in the caching and reusing of the content, which does not apply to the transactional signaling exchange. After analyzing 4G signaling call flows and message interdependencies (see ), our recommendation is that it is not beneficial to use ICN for control plane and mobility management functions. Among the features of ICN design, Interest aggregation and content caching are not applicable to control plane signaling messages. Control plane messages are originated and consumed by the applications, and they cannot be shared.

Integration of ICN in 4G User Plane We will consider when discussing different mechanisms to integrate ICN in mobile networks. In , we discussed generic experimental setups of ICN integration. In this section, we discuss the specific options of possible use of native ICN in the 4G user plane. The following options are considered:

1. Using Dual transport (IP/ICN) mode in mobile terminal
2. Using ICN in mobile terminal
3. Using ICN in eNodeB
4. Using ICN in Mobile Gateways (SGW/PGW)

Dual Transport (IP/ICN) Mode in Mobile Terminal The control and user-plane communications in 4G mobile networks are specified in 3GPP documents and . It is important to understand that a mobile terminal can be either consumer (receiving content) or publisher (pushing content for other clients). The protocol stack inside the mobile terminal (MT) is complex because it must support multiple radio connectivity access to eNodeB(s). provides a high-level description of a protocol stack, where IP is used at two layers: (1) user-plane communication and (2) UDP encapsulation. User-plane communication takes place between the Packet Data Convergence Protocol (PDCP) and Application layer, whereas UDP encapsulation is at the GTP protocol stack. The protocol interactions and impact of supporting the tunneling of an ICN packet into IP or supporting ICN natively are described in Figures and , respectively.

Dual Transport (IP/ICN) Mode in a Mobile Terminal +--------+ +--------+ | App | | CDN | +--------+ +--------+ |Transp. | | | | |Transp. | |Converg.|.|..............|...............|............|.|Converge| +--------+ | | | +--------+ | +--------+ | |.|..............|...............|.| |.|.| | | ICN/IP | | | | | ICN/IP | | | ICN/IP| | | | | | | | | | | +--------+ | +----+-----+ | +-----+-----+ | +-----+--+ | +--------+ | |.|.| | |.|.| | |.|.| | | | | | | PDCP | | |PDCP|GTP-U| | |GTP-U|GTP-U| | |GTP-U| | | | L2 | +--------+ | +----------+ | +-----------+ | +-----+ | | | | | RLC |.|.|RLC | UDP |.|.| UDP | UDP |.|.|UDP |L2|.|.| | +--------+ | +----------+ | +-----------+ | +-----+ | | | | | MAC |.|.| MAC| L2 |.|.| L2 | L2 |.|.| L2 | | | | | +--------+ | +----------+ | +-----------+ | +--------+ | +--------+ | L1 |.|.| L1 | L1 |.|.| L1 | L1 |.|.| L1 |L1|.|.| L1 | +--------+ | +----+-----+ | +-----+-----+ | +-----+--+ | +--------+ MT | BS (eNodeB) | SGW | PGW | Uu S1U S5/S8 SGi

The protocols and software stack used inside 4G-capable mobile terminals support both 3G and 4G software interworking and handover. 3GPP Rel.13 specifications and onward describe the use of IP and non-IP protocols to establish logical/session connectivity. We can leverage the non-IP protocol-based mechanism to deploy an ICN protocol stack in the mobile terminal as well as in an eNodeB and Mobile Gateways (SGW/PGW). The following paragraphs describe per-layer considerations of supporting the tunneling of ICN packets into IP or supporting ICN natively.

1. An existing application layer can be modified to provide options for a new ICN-based application and existing IP-based applications. The mobile terminal can continue to support existing IP-based applications or can develop new applications to support native ICN, ICNoIP, or IPoICN-based transport. The application layer can be provided with an option of selecting either ICN or IP transport, as well as radio interface, to send and receive data traffic. Our proposal is to provide an Application Programming Interface (API) to the application developers so they can choose either ICN or IP transport for exchanging the traffic with the network. As mentioned in , the TCL function handles the interaction of applications with multiple transport options.
2. The transport convergence layer helps determine the type of transport (such as ICN, hICN, or IP) and type of radio interface (LTE, Wi-Fi, or both) used to send and receive traffic. The application layer can make the decision to select a specific transport based on preference such as content location, content type, content publisher, congestion, cost, QoS, and so on. There can be an API to exchange parameters required for transport selection. Southbound interactions of the TCL will be either to IP or to ICN at the network layer. When selecting the IPoICN mode, the TCL is responsible for receiving an incoming IP or HTTP packet and publishing the packet to the ICN network under a suitable ICN name (that is, the hash over the destination IP address for an IP packet or the hash over the FQDN of the HTTP request for an HTTP packet). In the HTTP case, the TCL can maintain a pending request mapping table to map, returning responses to the originating HTTP request. The common API will provide a "connection" abstraction for this HTTP mode of operation, returning the response over said connection abstraction (akin to the TCP socket interface) while implementing a reliable transport connection semantic over the ICN from the mobile terminal to the receiving mobile terminal or the PGW. If the HTTP protocol stack remains unchanged, therefore utilizing the TCP protocol for transfer, the TCL operates in local TCP termination mode, retrieving the HTTP packet through said local termination.

   Dual Stack ICN Protocol Interactions +----------------+ +-----------------+ | ICN App (new) | |IP App (existing)| +---------+------+ +-------+---------+ | | +---------+----------------+---------+ | Transport Convergence Layer (new) | +------+---------------------+-------+ | | +------+------+ +------+-------+ |ICN function | | IP function | | (New) | | (Existing) | +------+------+ +------+-------+ | | +------+---------------------+-------+ | PDCP (updated to support ICN) | +-----------------+------------------+ | +-----------------+------------------+ | RLC (Existing) | +-----------------+------------------+ | +-----------------+------------------+ | MAC Layer (Existing) | +-----------------+------------------+ | +-----------------+------------------+ | Physical L1 (Existing) | +------------------------------------+

3. The ICN function (forwarder) is proposed to run in parallel to the existing IP layer. The ICN forwarder forwards the ICN packets such as an Interest packet to an eNodeB or a response "data packet" from an eNodeB to the application.
4. For the dual-transport scenario, when a mobile terminal is not supporting ICN as transport, the TCL can use the IP underlay to tunnel the ICN packets. The ICN function can use the IP interface to send Interest and Data packets for fetching or sending data, respectively. This interface can use the ICN overlay over IP.
5. To support ICN at the network layer in the mobile terminal, the PDCP layer should be aware of ICN capabilities and parameters. PDCP is located in the Radio Protocol Stack in the LTE Air interface, between the IP (Network layer) and Radio Link Control Layer (RLC). PDCP performs the following functions :
   1. Data transport by listening to the upper layer, formatting, and pushing down to the RLC
   2. Header compression and decompression using ROHC
   3. Security protections such as ciphering, deciphering, and integrity protection
   4. Radio layer messages associated with sequencing, packet drop detection and retransmission, and so on.
6. No changes are required for the lower layer such as RLC, Media Access Control (MAC), and Physical (L1) as they are not IP aware.

One key point to understand in this scenario is that ICN is deployed as an overlay on top of IP.

Using ICN in Mobile Terminal We can implement ICN natively in the mobile terminal by modifying the PDCP layer in 3GPP protocols. provides a high-level protocol stack description where ICN can be used at the following different layers:

1. User-plane communication
2. Transport layer

ICN transport would be a substitute for the GTP protocol. The removal of the GTP protocol stack is a significant change in the mobile architecture and requires a thorough study mainly because it is used not just for routing but for mobility management functions such as billing, mediation, and policy enforcement. The implementation of ICN natively in the mobile terminal leads to a changed communication model between the mobile terminal and eNodeB. Also, we can avoid tunneling the user-plane traffic from an eNodeB to the mobile packet core (SGW/PGW) through a GTP tunnel. For native ICN use, an application can be configured to use an ICN forwarder, and it does not need the TCL layer. Also, to support ICN at the network layer, the existing PDCP layer may need to be changed to be aware of ICN capabilities and parameters. The native implementation can provide new opportunities to develop new use cases leveraging ICN capabilities such as seamless mobility, mobile terminal to mobile terminal content delivery using a radio network without traversing the Mobile Gateways, and more.

Using Native ICN in Mobile Terminal +--------+ +--------+ | App | | CDN | +--------+ +--------+ |Transp. | | | | | |Transp. | |Converge|.|..............|..............|..............|.|Converge| +--------+ | | | | +--------+ | |.|..............|..............|..............|.| | | ICN/IP | | | | | | | | | | | | | | | +--------+ | +----+-----+ | +----------+ | +----------+ | | ICN/IP | | |.|.| | | | | | | | | | | | | PDCP | | |PDCP| ICN |.|.| ICN |.|.| ICN |.|.| | +--------+ | +----+ | | | | | | | | | | | RLC |.|.|RLC | | | | | | | | | | | +--------+ | +----------+ | +----------+ | +----------+ | +--------+ | MAC |.|.| MAC| L2 |.|.| L2 |.|.| L2 |.|.| L2 | +--------+ | +----------+ | +----------+ | +----------+ | +--------+ | L1 |.|.| L1 | L1 |.|.| L1 |.|.| L1 |.|.| L1 | +--------+ | +----+-----+ | +----------+ | +----------+ | +--------+ MT | BS(eNodeB) | SGW | PGW | Uu S1u S5/S8 SGi

Using ICN in eNodeB The eNodeB is a physical point of attachment for the mobile terminal where radio protocols are converted into IP transport protocols for dual transport/overlay and native ICN, respectively (see Figures and ). When a mobile terminal performs an attach procedure, it will be assigned an identity as either IP or dual transport (IP and ICN) or ICN endpoint. A mobile terminal can initiate data traffic using any of the following options:

1. Native IP (IPv4 or IPv6)
2. Native ICN
3. Dual transport IP (IPv4/IPv6) and ICN

The mobile terminal encapsulates a user data transport request into the PDCP layer and sends the information on the air interface to the eNodeB, which in turn receives the information and, using PDCP , de-encapsulates the air-interface messages and converts them to forward-to-core Mobile Gateways (SGW/PGW). As shown in , to support ICN natively in an eNodeB, it is proposed to provide TCL capabilities in an eNodeB (similar to as provided in MT), which provides the following functions:

1. It decides the forwarding strategy for a user data request coming from the mobile terminal. The strategy can decide based on preference indicated by the application, such as congestion, cost, QoS, and so on.
2. It uses an eNodeB to provide an open API to external management systems in order to provide eNodeB the capability to program the forwarding strategies.

   Integration of Native ICN in eNodeB +---------------+ | | MT request | | ICN +---------+ +---->| content using |--+--- transport -->| | | |ICN protocol | | | | | +---------------+ | | | | | | | | +---------------+ | | | +-+ | | MT request | | IP |To mobile| | |-+---->| content using |--+--- transport -->| GW | +-+ | | IP protocol | | |(SGW/PGW)| MT | +---------------+ | | | | | | | | +---------------+ | | | | | MT request | | Dual stack | | +---->| content using |--+--- IP+ICN -->| | |IP/ICN protocol| | transport +---------+ +---------------+ | eNodeB S1u

3. The eNodeB can be upgraded to support three different types of transport: IP, ICN, and dual transport IP+ICN towards Mobile Gateways, as depicted in . It is also proposed to deploy IP and/or ICN forwarding capabilities into an eNodeB for efficient transfer of data between the eNodeB and Mobile Gateways. The following are choices for forwarding a data request towards Mobile Gateways:
   1. Assuming the eNodeB is IP enabled and the MT requests an IP transfer, the eNodeB forwards data over IP.
   2. Assuming the eNodeB is ICN enabled and the MT requests an ICN transfer, the eNodeB forwards data over ICN.
   3. Assuming the eNodeB is IP enabled and the MT requests an ICN transfer, the eNodeB overlays ICN on IP and forwards user-plane traffic over IP.
   4. Assuming the eNodeB is ICN enabled and the MT requests an IP transfer, the eNodeB overlays IP on ICN and forwards user-plane traffic over ICN .

Using ICN in Packet Core Gateways (SGW/PGW) Mobile Gateways (a.k.a. Evolved Packet Core (EPC)) include SGW and PGW, which perform session management for MT from the initial attach to disconnection. When MT is powered on, it performs Network-Access-Stratum (NAS) signaling and attaches to PGW after successful authentication. PGW is an anchoring point for MT and is responsible for service creations, authorization, maintenance, and so on. The entire functionality is managed using an IP address(es) for MT. To implement ICN in EPC, the following functions are proposed:

1. Insert ICN attributes in the session management layer for additional functionality with IP stack. The session management layer is used for performing attach procedures and assigning logical identity to users. After successful authentication by HSS, MME sends a Create Session Request (CSR) to SGW and SGW to PGW.
2. When MME sends a Create Session Request message (Step 12 in ) to SGW or PGW, it includes a Protocol Configuration Option (PCO) Information Element (IE) containing MT capabilities. We can use PCO IE to carry ICN-related capabilities information from MT to PGW. This information is received from MT during the initial attach request in MME. Details of available TLV, which can be used for ICN, are given in subsequent sections. MT can support native IP, ICN+IP, or native ICN. IP is referred to as both IPv4 and IPv6 protocols.
3. For ICN+IP-capable MT, PGW assigns the MT both an IP address and ICN identity. MT selects either of the identities during the initial attach procedures and registers with the network for session management. For ICN-capable MT, it will provide only ICN attachment. For native IP-capable MT, there is no change.
4. To support ICN-capable attach procedures and use ICN for user-plane traffic, PGW needs to have full ICN protocol stack functionalities. Typical ICN capabilities include functions such as CS, PIT, FIB capabilities, and so on. If MT requests ICN in PCO IE, then PGW registers MT with ICN names. For ICN forwarding, PGW caches content locally using CS functionality.
5. PCO IE as described in (see Figure 10.5.136 on page 656 and Table 10.5.154 on page 659) provides details for different fields.
   1. Octet 3 (configuration protocols define PDN types), which contains details about IPv4, IPv6, both IPv4 and IPv6, or ICN.
   2. Any combination of Octet 4 to Z can be used to provide additional information related to ICN capability. It is most important that PCO IE parameters are matched between MT and Mobile Gateways (SGW/PGW) so they can be interpreted properly and the MT can attach successfully.
6. The ICN functionalities in SGW and PGW should be matched with MT and the eNodeB because they will exchange ICN protocols and parameters.
7. Mobile Gateways (SGW/PGW) will also need ICN forwarding and caching capability. This is especially important if CUPS is implemented. User Plane Function (UPF), comprising the SGW and PGW user plane, will be located at the edge of the network and close to the end user. ICN-enabled gateway means that this UPF would serve as a forwarder and should be capable of caching, as is the case with any other ICN-enabled node.
8. The transport between PGW and CDN provider can be either IP or ICN. When MT is attached to PGW with ICN identity and communicates with an ICN-enabled CDN provider, it will use ICN primitives to fetch the data. On the other hand, for an MT attached with an ICN identity, if PGW must communicate with an IP-enabled CDN provider, it will have to use an ICN-IP interworking gateway to perform conversion between ICN and IP primitives for data retrieval. In the case of CUPS implementation with an offload close to the edge, this interworking gateway can be collocated with the UPF at the offload site to maximize the path optimization. Further study is required to understand how this ICN-to-IP (and vice versa) interworking gateway would function.

An Experimental Test Setup This section proposes an experimental lab setup and discusses the open issues and questions that use of the ICN protocol is intended to address. To further test the modifications proposed in different scenarios, a simple lab can be set up, as shown in .

Native ICN Deployment Lab Setup +------------------------------------------+ | +-----+ +------+ (```). +------+ | (````). +-----+ | | SUB |-->| EMU |--(x-haul'.-->| EPC |--->( PDN ).-->| CDN | | +-----+ +------+ `__..'' +------+ | `__...' +-----+ +------------------------------------------+ 4G Mobile Network Functions

The following test scenarios can be set up with deployment based on Virtual Machine (VM):

1. SUB: An ICN-simulated client (using ndnSIM) - a client application on a workstation requesting content.
2. EMU: Test unit emulating an eNodeB. This is a test node allowing for UE attachment and routing traffic subsequently from the Subscriber to the Publisher.
3. EPC: Evolved Packet Core in a single instance (such as Open5GCore ).
4. CDN: Content delivery by a Publisher server.

For the purpose of this testing, ICN-emulating code can be inserted in the test code in EMU to emulate an ICN-capable eNodeB. An example of the code to be used is NS3 in its LTE model. The effect of such traffic on EPC and CDN can be observed and documented. In a subsequent phase, EPC code supporting ICN can be tested when available. Another option is to simulate the UE/eNodeB and EPC functions using NS3's LTE and EPC models, respectively. The LTE model includes the LTE Radio Protocol stack, which resides entirely within the UE and the eNodeB nodes. This capability provides the simulation of UE and eNodeB deployment use cases. Similarly, the EPC model includes core network interfaces, protocols, and entities, which reside within the Mobile Gateways (SGW/PGW), and MME nodes and partially within the eNodeB nodes. Even with its current limitations (such as IPv4 only, lack of integration with ndnSIM, and no support for UE idle state), LTE simulation may be a very useful tool. In any case, both control and user-plane traffic should be tested independently according to the deployment model discussed in .

Expected Outcomes from Experimentation The experimentation explained in can be categorized in three broader scopes as follows. Note that further research and study is required to fully understand and document the impact.

Architecture scope:

to study the aspect of use of ICN at the user plane to reduce the complexities in current transport protocols while also evaluating its use in the control plane.

Performance scope:

to evaluate the gains through multicast, caching, and other ICN features.

Deployment scope:

to check the viability of ICN inclusion in the 3GPP protocol stack and in real-world deployments.

Feeding into ICN Research Specifically, we have identified the following open questions, from the architectural and performance perspective, that the proposed experiments with ICN implementation scenarios in 4G mobile networks could address in further research:

1. Efficiency gains in terms of the amount of traffic in multicast scenarios (i.e., quantify the possible gains along different use cases) and latency for cached content, mainly in the CDN use case.
2. How the new transport would coexist or replace the legacy transport protocols (e.g., IPv4, IPv6, MPLS, RSVP, etc.) and related services (e.g., bandwidth management, QoS handling, etc.).
3. To what extent the simplification in the IP-based transport protocols will be achieved. The multiple overlays (e.g., the MPLS, VPN, Virtual Private LAN Service (VPLS), Ethernet VPN, etc.) of services in the current IP-based transport adds to the complexity on top of basic IP transport. This makes the troubleshooting extremely challenging.
4. How the new transport can become service aware such that it brings in more simplicity in the system.
5. Confirm how (in)adequate ICN implementation would be in the control plane (which this document discourages). Given that the 5G system, as specified in (Appendix G.4), encourages the use of name-based routing in the (5G) control plane for realizing the 5G-specific service-based architecture for control plane services (so-called network function service), it would be worthwhile to investigate whether the 4G control plane would benefit similarly from such use or whether specific 4G architectural constraints would prevent ICN from providing any notable benefit.

Use of Results Beyond Research With the experiments and their outcomes outlined in this document, we believe that this technology is ready for a wider use and adoption, providing additional insights. Specifically, we expect to study the following:

1. Viability of ICN inclusion in the 3GPP protocol stack, i.e., investigating how realistic it would be to modify the stack, considering the scenarios explained in , and completing the user session without feature degradation.
2. Viability of utilizing solutions in greenfield deployments, i.e., deploying the ICN-based extensions and solutions proposed in this document in greenfield 4G deployments in order to assess real-world benefits when doing so.

IANA Considerations This document has no IANA actions.

Security and Privacy Considerations This section will cover some security and privacy considerations in mobile and 4G networks because of the introduction of ICN.

Security Considerations To ensure only authenticated mobile terminals are connected to the network, 4G mobile networks implement various security mechanisms. From the perspective of using ICN in the user plane, the following security aspects need to be taken care of:

1. MT authentication and authorization
2. Radio or air interface security
3. Denial-of-service attacks on the Mobile Gateway; services are either by the MT or by external entities in the Internet
4. Content poisoning in either transport or servers
5. Content cache pollution attacks
6. Secure naming, routing, and forwarding
7. Application security

Security over the LTE air interface is provided through cryptographic techniques. When MT is powered up, it performs a key exchange between the MT's Universal Mobile Telecommunications System Subscriber Identity Module (USIM) and HSS/Authentication Center using NAS messages, including ciphering and integrity protections between MT and MME. Details for secure MT authentication, key exchange, ciphering, and integrity protection messages are given in the 3GPP call flow . With ICN, we are modifying the protocol stack for the user plane and not the control plane. The NAS signaling is exchanged between MT and Mobile Gateways, e.g., MME, using the control plane; therefore, there is no adverse impact of ICN on MT. 4G uses IP transport in its mobile backhaul (between an eNodeB and the core network). In case of provider-owned backhaul, the Service Provider may require implementing a security mechanism in the backhaul network. The native IP transport continues to leverage security mechanisms such as Internet Key Exchange (IKE) and the IP Security (IPsec) protocol. More details of mobile backhaul security are provided in 3GPP network security specifications and . When a mobile backhaul is upgraded to support dual transport (IP+ICN) or native ICN, it is required to implement security techniques that are deployed in the mobile backhaul. When ICN forwarding is enabled on mobile transport routers, we need to deploy security practices based on and . 4G Mobile Gateways (SGW/PGW) perform some key functions such as content-based online/offline billing and accounting, deep packet inspection (DPI), and lawful interception (LI). When ICN is deployed in the user plane, we need to integrate ICN security for sessions between MT and the gateway. If we encrypt user-plane payload metadata, then it might be difficult to perform routing based on contents and it may not work because we need decryption keys at every forwarder to route the content. The content itself can be encrypted between publisher and consumer to ensure privacy. Only the user with the right decryption key shall be able to access the content. We need further research for ICN impact on LI, online/offline charging, and accounting.

Privacy Considerations In 4G networks, there are two main privacy issues :

1. User Identity Privacy Issues. The main privacy issue within 4G is the exposure of the International Mobile Subscriber Identity (IMSI). The IMSI can be intercepted by adversaries. Such attacks are commonly referred to as "IMSI catching".
2. Location Privacy Issues. IMSI catching is closely related to the issue of location privacy. Knowing the IMSI of a user allows the attacker to track the user's movements and create a profile about the user and thus breach the user's location privacy.

In any network, caching implies a trade-off between network efficiency and privacy. The activity of users is exposed to the scrutiny of cache owners with whom they may not have any relationship. By monitoring the cache transactions, an attacker could obtain significant information related to the objects accessed, topology, and timing of the requests . Privacy concerns are amplified by the introduction of new network functions such as information lookup and network storage, and different forms of communication . Privacy risks in ICN can be broadly divided in the following categories :

1. Timing attack
2. Communication monitoring attack
3. Censorship and anonymity attack
4. Protocol attack
5. Naming-signature privacy

The introduction of TCL effectively enables ICN at the application and/or transport layer depending on the scenario described in . Enabling ICN in 4G networks is expected to increase efficiency by taking advantage of ICN's inherent characteristics. This approach would potentially leave some of the above-mentioned privacy concerns open as a consequence of using ICN transport and ICN inherent privacy vulnerabilities.

1. IPoIP () would not be affected as TCL has no role in it, and ICN does not apply.
2. The ICNoICN scenario () has increased risk of a privacy attack, and that risk is applicable to the ICN protocol in general rather than specifically to the 4G implementation. Since this scenario describes communication over ICN transport, every forwarder in the path could be a potential risk for a privacy attack.
3. The ICNoIP scenario () uses IP for transport, so the only additional ICN-related potential privacy risk areas are the endpoints (consumer and publisher) where, at the application layer, content is being served.
4. The IPoICN scenario () could have potentially increased risk due to possible vulnerability of the forwarders in the path of ICN transport.

Privacy issues already identified in 4G remain a concern if ICN is introduced in any of the scenarios described earlier and compounds to the new ICN-related privacy issues. Many research papers have been published that propose solutions to the privacy issues listed above. For LTE-specific privacy issues, some of the proposed solutions are IMSI encryption by an MT; mutual authentication; concealing the real IMSI within a random bit stream of certain size where only the subscriber and HSS could extract the respective IMSI; IMSI replacement with a changing pseudonym that only the HSS server can map to the UE's IMSI; and others. Similarly, some of the proposed ICN-specific privacy concerns mitigation methods, applicable where ICN transport is introduced as specified earlier in this section, include the following :

• Delay for the first, or first k, interests on edge routers (timing attack)
• Creating a secure tunnel or clients flagging the requests as non-cacheable for privacy (communication monitoring attack)
• Encoding interest by mixing the content and cover file or using a hierarchical DNS-based brokering model (censorship and anonymity attack)
• Use of rate-limiting requests for a specific namespace (protocol attack)
• Cryptographic content hash-based naming or digital identity in an overlay network (naming-signature privacy)

Further research in this area is needed. Detailed discussion of privacy is beyond the scope of this document.

Summary In this document, we have discussed 4G networks and the experimental setups to study the advantages of the potential use of ICN for efficient delivery of contents to mobile terminals. We have discussed different options to try and test ICN and dependencies such as ICN functionalities and changes required in different 4G network elements. In order to further explore potential use of ICN, one can devise an experimental setup consisting of 4G network elements and deploy ICN data transport in the user plane. Different options can be overlay, dual transport (IP + ICN), hICN, or natively (by integrating ICN with CDN, eNodeB, SGW, PGW, and a transport network). Note that, for the scenarios discussed above, additional study is required for lawful interception, billing/mediation, network slicing, and provisioning APIs. Edge Computing provides capabilities to deploy functionalities such as CDN caching and mobile user plane functions (UPFs) . Recent research for delivering real-time video content using ICN has also been proven to be efficient and can be used towards realizing the benefits of using ICN in an eNodeB, edge computing, Mobile Gateways (SGW/PGW), and CDN. The key aspect for ICN is in its seamless integration in 4G and 5G networks with tangible benefits so we can optimize content delivery using a simple and scalable architecture. The authors will continue to explore how ICN forwarding in edge computing could be used for efficient data delivery from the mobile edge. Based on our study of control plane signaling, it is not beneficial to deploy ICN with existing protocols unless further changes are introduced in the control protocol stack itself. As a starting step towards use of ICN in the user plane, it is proposed to incorporate protocol changes in MT, an eNodeB, and SGW/PGW for data transport. ICN has inherent capabilities for mobility and content caching, which can improve the efficiency of data transport for unicast and multicast delivery. The authors welcome contributions and suggestions, including those related to further validations of the principles by implementing prototypes and/or proof of concepts in the lab and in the production environment.

References Normative References 3GPP 3GPP 3GPP 3GPP 3GPP Informative References ACM-ICN '15: Proceedings of the 2nd ACM Conference on Information-Centric Networking, pp. 189-190 MILCOM 2006 - 2006 IEEE Military Communications conference, pp. 1-6 FD.io IEEE Network, Vol. 29, Issue 3, pp. 68-74 IEEE Network, Vol. 34, Issue 3, pp. 270-276 3GPP, The Mobile Broadband Standard ACM-ICN '14: Proceedings of the 1st ACM Conference on Information-Centric Networking, pp. 5-6 Work in Progress Cisco Press Networking Technology series Work in Progress Corning Incorporated Cisco Systems Huawei Technologies Duesseldorf GmbH InterDigital Inc. CableLabs Work in Progress 2014 IEEE Global Communications Conference, pp. 1861-1866 2015 European Conference on Networks and Communications (EuCNC), pp. 413-417 The 21st IEEE International Workshop on Local and Metropolitan Area Networks, Beijing, pp. 1-6 ETSI ETSI GS MEC 003 Version 1.1.1 IEEE International Conference on Multimedia and Expo Workshops (ICMEW), Turin, Italy, pp. 1-6 International Journal of Computer Network and Information Security(IJCNIS), Vol. 9, Issue 1, pp. 54-63 IEICE Transactions on Communications, Vol. E99.B, Issue 5, pp. 974-991 Next Generation Mobile Networks LTE-Advanced Transport Provisioning Version 0.0.14 ns-3 ns-3 IEEE Communications Surveys and Tutorials Vol. 17, Issue 2, pp.580-603 Proceedings of the 2009 IEEE International Conference on Communications ICC'09, pp. 575-579 Open5GCore Work in Progress This document describes service classes configured with Diffserv and recommends how they can be used and how to construct them using Differentiated Services Code Points (DSCPs), traffic conditioners, Per-Hop Behaviors (PHBs), and Active Queue Management (AQM) mechanisms. There is no intrinsic requirement that particular DSCPs, traffic conditioners, PHBs, and AQM be used for a certain service class, but as a policy and for interoperability it is useful to apply them consistently. This memo provides information for the Internet community. The use of cellular broadband for accessing the Internet and other data services via smartphones, tablets, and notebook/netbook computers has increased rapidly as a result of high-speed packet data networks such as HSPA, HSPA+, and now Long-Term Evolution (LTE) being deployed. Operators that have deployed networks based on 3rd Generation Partnership Project (3GPP) network architectures are facing IPv4 address shortages at the Internet registries and are feeling pressure to migrate to IPv6. This document describes the support for IPv6 in 3GPP network architectures. This document is not an Internet Standards Track specification; it is published for informational purposes. This document aims at establishing a common understanding about a set of scenarios that can be used as a base for the evaluation of different information-centric networking (ICN) approaches so that they can be tested and compared against each other while showcasing their own advantages. Towards this end, we review the ICN literature and document scenarios which have been considered in previous performance evaluation studies. We discuss a variety of aspects that an ICN solution can address. This includes general aspects, such as, network efficiency, reduced complexity, increased scalability and reliability, mobility support, multicast and caching performance, real-time communication efficiency, energy consumption frugality, and disruption and delay tolerance. We detail ICN-specific aspects as well, such as information security and trust, persistence, availability, provenance, and location independence. This document is a product of the IRTF Information-Centric Networking Research Group (ICNRG). This memo describes research challenges for Information-Centric Networking (ICN), an approach to evolve the Internet infrastructure to directly support information distribution by introducing uniquely named data as a core Internet principle. Data becomes independent from location, application, storage, and means of transportation, enabling or enhancing a number of desirable features, such as security, user mobility, multicast, and in-network caching. Mechanisms for realizing these benefits is the subject of ongoing research in the IRTF and elsewhere. This document describes current research challenges in ICN, including naming, security, routing, system scalability, mobility management, wireless networking, transport services, in-network caching, and network management. This document is a product of the IRTF Information-Centric Networking Research Group (ICNRG). This document presents a number of considerations regarding evaluating Information-Centric Networking (ICN) and sheds some light on the impact of ICN on network security. It also surveys the evaluation tools currently available to researchers in the ICN area and provides suggestions regarding methodology and metrics. This document describes the core concepts of the Content-Centric Networking (CCNx) architecture and presents a network protocol based on two messages: Interests and Content Objects. It specifies the set of mandatory and optional fields within those messages and describes their behavior and interpretation. This architecture and protocol specification is independent of a specific wire encoding. The protocol also uses a control message called an Interest Return, whereby one system can return an Interest message to the previous hop due to an error condition. This indicates to the previous hop that the current system will not respond to the Interest. This document is a product of the Information-Centric Networking Research Group (ICNRG). The document received wide review among ICNRG participants. Two full implementations are in active use and have informed the technical maturity of the protocol specification. Content-Centric Networking (CCNx) is a network protocol that uses a hierarchical name to forward requests and to match responses to requests. This document specifies the encoding of CCNx messages in a TLV packet format, including the TLV types used by each message element and the encoding of each value. The semantics of CCNx messages follow the encoding-independent CCNx Semantics specification. This document is a product of the Information Centric Networking research group (ICNRG). The document received wide review among ICNRG participants and has two full implementations currently in active use, which have informed the technical maturity of the protocol specification. This is a position paper. It documents the author's personal views on how Quality of Service (QoS) capabilities ought to be accommodated in Information-Centric Networking (ICN) protocols like Content-Centric Networking (CCNx) or Named Data Networking (NDN), which employ flow-balanced Interest/Data exchanges and hop-by-hop forwarding state as their fundamental machinery. It argues that such protocols demand a substantially different approach to QoS from that taken in TCP/IP and proposes specific design patterns to achieve both classification and differentiated QoS treatment on both a flow and aggregate basis. It also considers the effect of caches in addition to memory, CPU, and link bandwidth as resources that should be subject to explicitly unfair resource allocation. The proposed methods are intended to operate purely at the network layer, providing the primitives needed to achieve transport- and higher-layer QoS objectives. It explicitly excludes any discussion of Quality of Experience (QoE), which can only be assessed and controlled at the application layer or above. This document is not a product of the IRTF Information-Centric Networking Research Group (ICNRG) but has been through formal Last Call and has the support of the participants in the research group for publication as an individual submission. This document defines a convergence layer for Content-Centric Networking (CCNx) and Named Data Networking (NDN) over IEEE 802.15.4 Low-Power Wireless Personal Area Networks (LoWPANs). A new frame format is specified to adapt CCNx and NDN packets to the small MTU size of IEEE 802.15.4. For that, syntactic and semantic changes to the TLV-based header formats are described. To support compatibility with other LoWPAN technologies that may coexist on a wireless medium, the dispatching scheme provided by IPv6 over LoWPAN (6LoWPAN) is extended to include new dispatch types for CCNx and NDN. Additionally, the fragmentation component of the 6LoWPAN dispatching framework is applied to Information-Centric Network (ICN) chunks. In its second part, the document defines stateless and stateful compression schemes to improve efficiency on constrained links. Stateless compression reduces TLV expressions to static header fields for common use cases. Stateful compression schemes elide states local to the LoWPAN and replace names in Data packets by short local identifiers. This document is a product of the IRTF Information-Centric Networking Research Group (ICNRG). 2016 International Conference on Military Communications and Information Systems (ICMCIS), pp. 1-7 ICNRG, Buenos Aires, IETF 95 IEEE Communications Surveys and Tutorials, Vol. 20, Issue 1, pp. 566-600 3GPP 3GPP 3GPP 3GPP 3GPP 3GPP 3GPP 3GPP

Acknowledgements We thank all contributors, reviewers, and the chairs for their valuable time in providing comments and feedback that helped improve this document. We especially want to mention the following members of the IRTF Information-Centric Networking Research Group (ICNRG), listed in alphabetical order: , , , , , , , and . The IRSG review was provided by .

Authors' Addresses Google Inc.

Mountain View California 94043 United States of America psuthar@google.com

Cisco Systems Inc.

Naperville Illinois 60540 United States of America mistolic@cisco.com

Cisco Systems Inc.

San Jose California 95134 United States of America anjangam@cisco.com

Huawei Technologies

Riesstrasse 25 Munich 80992 Germany dirk.trossen@huawei.com

F5 Networks

3545 North First Street San Jose California 95134 United States of America r.ravindran@f5.com