V6OPS Working Group                                             D. Binet
Internet-Draft                                              M. Boucadair
Intended status: Informational                            France Telecom
Expires: July 16, August 5, 2015                                        A. Vizdal
                                                     Deutsche Telekom AG
                                                                 G. Chen
                                                            China Mobile
                                                              N. Heatley
                                                             R. Chandler
                                                         eircom | meteor
                                                        January 12,
                                                        February 1, 2015

 An Internet Protocol Version 6 (IPv6) Profile for 3GPP Mobile Devices


   This document defines a profile that is a superset of that of the
   connection to IPv6 cellular networks defined in the IPv6 for Third
   Generation Partnership Project (3GPP) Cellular Hosts document.  This
   document identifies features to deliver IPv4 connectivity service
   over defines an IPv6-only transport as well as the required features IPv6 profile that a number of operators recommend
   in order to connect 3GPP mobile devices to an IPv6-only or dual-stack
   wireless network (including 3GPP cellular network and IEEE 802.11

   Both hosts and devices with capability to share their WAN (Wide Area
   Network) connectivity are in scope.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on July 16, August 5, 2015.

Copyright Notice

   Copyright (c) 2015 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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Connectivity Recommendations  . . . . . . . . . . . . . . . .   5
     2.1.  WLAN Connectivity Recommendations . . . . . . . . . . . .   7   8
   3.  Advanced Recommendations  . . . . . . . . . . . . . . . . . .   8
   4.  Recommendations for Cellular Devices with LAN Capabilities  .  10
   5.  APIs & Applications Recommendations . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13  14
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  15

1.  Introduction

   IPv6 deployment in 3GPP mobile networks is the only perennial
   solution to the exhaustion of IPv4 addresses in those networks.
   Several mobile operators have already deployed IPv6 [RFC2460] or are
   in the pre-deployment phase.  One of the major hurdles encountered as perceived
   by some mobile operators is the availability of non-broken IPv6
   implementation in mobile devices.

   [RFC7066] lists a set of features to be supported by cellular hosts
   to connect to 3GPP mobile networks.  In the light of recent IPv6
   production deployments, additional features to facilitate IPv6-only
   deployments while accessing IPv4-only service are to be considered.

   This document defines an IPv6 profile for mobile devices listing
   specifications produced by various Standards Developing Organizations
   (in particular 3GPP and IETF).  The objectives of this effort are:

   1.  List in one single document a comprehensive list of IPv6 features
       for a mobile device, including both IPv6-only and dual-stack
       mobile deployment contexts.  These features cover various network
       types such as GPRS (General Packet Radio Service), EPC (Evolved
       Packet Core) or IEEE 802.11 network.

   2.  Help Operators with the detailed device requirement list
       preparation (to be exchanged with device suppliers).  This is
       also a contribution to harmonize Operators' requirements towards
       device vendors.

   3.  Vendors to be aware of a set of features to allow for IPv6
       connectivity and IPv4 service continuity (over an IPv6-only

   The recommendations do not include 3GPP release details.  For more
   information on the 3GPP releases detail, the reader may refer to
   Section 6.2 of [RFC6459].

   Some of the features listed in this profile document require to
   activate dedicated functions at the network side.  It is out of scope
   of this document to list these network-side functions.

   A detailed overview of IPv6 support in 3GPP architectures is provided
   in [RFC6459].

1.1.  Terminology

   This document makes use of the terms defined in [RFC6459].  In
   addition, the following terms are used:

   o  "3GPP cellular host" (or cellular host for short) denotes a 3GPP
      device which can be connected to 3GPP mobile networks or IEEE
      802.11 networks.

   o  "3GPP cellular device" (or cellular device for short) refers to a
      cellular host which supports the capability to share its WAN (Wide
      Area Network) connectivity.

   o  "Cellular host" and "mobile host" are used interchangeably.

   o  "Cellular device" and "mobile device" are used interchangeably.

   PREFIX64 denotes an IPv6 prefix used to build IPv4-converted IPv6
   addresses [RFC6052].

1.2.  Scope

   A 3GPP mobile network can be used to connect various user equipments
   such as a mobile telephone, a CPE (Customer Premises Equipment) or a
   machine-to-machine (M2M) device.  Because of this diversity of
   terminals, it is necessary to define a set of IPv6 functionalities
   valid for any node directly connecting to a 3GPP mobile network.
   This document describes these functionalities.

   This document is structured to provide the generic IPv6
   recommendations which are valid for all nodes, whatever their
   function (e.g., host or CPE) or service (e.g., Session Initiation
   Protocol (SIP, [RFC3261])) capability.  The document also contains
   sections covering specific functionalities for devices providing some
   LAN functions (e.g., mobile CPE or broadband dongles).

   The recommendations listed below are valid for both 3GPP GPRS and
   3GPP EPS (Evolved Packet System) access.  For EPS, PDN-Connection
   term is used instead of PDP-Context.

   This document identifies also some WLAN-related IPv6 recommendations.
   Other non-3GPP accesses [TS.23402] are out of scope of this document.

   This profile is a superset of that of the IPv6 profile for 3GPP
   Cellular Hosts [RFC7066], which is in turn a superset of IPv6 Node
   Requirements [RFC6434].  It targets cellular nodes, including GPRS,
   EPC (Evolved Packet Core) and IEEE 802.11 networks, that require
   features to ensure IPv4 service delivery over an IPv6-only transport
   in addition to the base IPv6 service.  Moreover, this profile covers
   cellular CPEs that are used in various deployments to offer fixed-
   like services.  Recommendations inspired from real deployment
   experiences (e.g., roaming) are included in this profile.  Also, this
   profile sketches recommendations for the sake of deterministic
   behaviors of cellular devices when the same configuration information
   is received over several channels.

   For conflicting recommendations in [RFC7066] and [RFC6434] (e.g.,
   Neighbor Discovery Protocol), this profile adheres to [RFC7066].
   Indeed, the support of Neighbor Discovery Protocol is mandatory in
   3GPP cellular environment as it is the only way to convey IPv6 prefix
   towards the 3GPP cellular device.  In particular, MTU (Maximum
   Transmission Unit) communication via Router Advertisement must be
   supported since many 3GPP networks do not have a standard MTU

   This profile uses a stronger language for the support of Prefix
   Delegation compared to [RFC7066].  The main motivation is that
   cellular networks are more and more perceived as an alternative to
   fixed networks for home IP-based services delivery; especially with
   the advent of smartphones and 3GPP data dongles.  There is a need for
   an efficient mechanism to assign shorter prefix than /64 to cellular
   hosts so that each LAN segment can get its own /64 prefix and multi-
   link subnet issues to be avoided.  The support of this functionality
   in both cellular and fixed networks is key for fixed-mobile

   This document is not a standard, and conformance with it is not
   required in order to claim conformance with IETF standards for IPv6.
   The support of the full set of features may not be required in some
   deployment contexts.  The authors believe that the support of a
   subset of the features included in this protocol may lead to degraded
   level of service in some deployment contexts.

2.  Connectivity Recommendations

   This section identifies the main connectivity recommendations to be
   followed by a cellular host to attach to a network using IPv6.  Both
   dual-stack and IPv6-only deployment models are considered.  IPv4
   service continuity features are listed in this section because these
   are critical for Operators with an IPv6-only deployment model.

   C_REC#1:  In order to allow each operator to select their own
             strategy regarding IPv6 introduction, the cellular host
             must support both IPv6 and IPv4v6 PDP-Contexts [TS.23060].
             Both IPv6 and IPv4v6 PDP-Contexts must be supported.  IPv4,
             IPv6 or IPv4v6 PDP-Context request acceptance depends on
             the cellular network configuration.

   C_REC#2:  The cellular host must comply with the behavior defined in
             [TS.23060] [TS.23401] [TS.24008] for requesting a PDP-
             Context type.  In particular, the cellular host must
             request by default an IPv6 PDP-Context if the cellular host
             is IPv6-only and requesting an IPv4v6 PDP-Context if the
             cellular host is dual-stack or when the cellular host is
             not aware of connectivity types requested by devices
             connected to it (e.g., cellular host with LAN capabilities
             as discussed in Section 4):

             *  If the requested IPv4v6 PDP-Context is not supported by
                the network, but IPv4 and IPv6 PDP types are allowed,
                then the cellular host will be configured with an IPv4
                address or an IPv6 prefix by the network.  It must
                initiate another PDP-Context activation in addition to
                the one already activated for a given APN (Access Point

             *  If the requested PDP type and subscription data allows
                only one IP address family (IPv4 or IPv6), the cellular
                host must not request a second PDP-Context to the same
                APN for the other IP address family.

             The text above focuses on the specification part which
             explains the behavior for requesting IPv6-related PDP-
             Context(s).  Understanding this behavior is important to
             avoid having broken IPv6 implementations in cellular

   C_REC#3:  The cellular host must support the PCO (Protocol
             Configuration Options) [TS.24008] to retrieve the IPv6
             address(es) of the Recursive DNS server(s).

                In-band signaling is a convenient method to inform the
                cellular host about various services, including DNS
                server information.  It does not require any specific
                protocol to be supported and it is already deployed in
                IPv4 cellular networks to convey such DNS information.

   C_REC#4:  The cellular host must support IPv6 aware Traffic Flow
             Templates (TFT) [TS.24008].

                Traffic Flow Templates are employing a packet filter to
                couple an IP traffic with a PDP-Context.  Thus a
                dedicated PDP-Context and radio resources can be
                provided by the cellular network for certain IP traffic.

   C_REC#5:  If the cellular host receives the DNS information in
             several channels for the same interface, the following
             preference order must be followed:

                1.  PCO

                2.  RA

                3.  DHCPv6

   C_REC#6:  The cellular host must be able to be configured to limit
             PDP type(s) for a given APN.  The default mode is to allow
             all supported PDP types.  Note, C_REC#2 discusses the
             default behavior for requesting PDP-Context type(s).

                This feature is useful to drive the behavior of the UE
                to be aligned with: (1) service-specific constraints
                such as the use of IPv6-only for VoLTE (Voice over LTE),
                (2) network conditions with regards to the support of
                specific PDP types (e.g., IPv4v6 PDP-Context is not
                supported), (3) IPv4 sunset objectives, (4) subscription
                data, etc.

   C_REC#7:  Because of potential operational deficiencies to be
             experienced in some roaming situations, the cellular host
             must be able to be configured with a home IP profile and a
             roaming IP profile.  The aim of the roaming profile is to
             limit the PDP type(s) requested by the cellular host when
             out of the home network.  Note that distinct PDP type(s)
             and APN(s) can be configured for home and roaming cases.

   C_REC#8:  In order to ensure IPv4 service continuity in an IPv6-only
             deployment context, the cellular host should support a
             method to locally construct IPv4-embedded IPv6 addresses
             [RFC6052].  A method to learn PREFIX64 should be supported
             by the cellular host.

                This solves the issue when applications use IPv4
                referrals on IPv6-only access networks.

                In PCP-based environments, cellular hosts should follow
                [RFC7225] to learn the IPv6 Prefix used by an upstream
                PCP-controlled NAT64 device.  If PCP is not enabled, the
                cellular host should implement the method specified in
                [RFC7050] to retrieve the PREFIX64.

   C_REC#9:  In order to ensure IPv4 service continuity in an IPv6-only
             deployment context, the cellular host should implement the
             Customer Side Translator (CLAT, [RFC6877]) function which
             is compliant with [RFC6052][RFC6145][RFC6146].

                CLAT function in the cellular host allows for IPv4-only
                application and IPv4-referals to work on an IPv6-only
                connectivity.  CLAT function requires a NAT64 capability
                [RFC6146] in the core network.

                The IPv4 Service Continuity Prefix used by CLAT is
                defined in [RFC7335].

2.1.  WLAN Connectivity Recommendations

   It is increasingly common for cellular hosts have a WLAN interface in
   addition to their cellular interface.  These hosts are likely to be
   connected to private or public hotspots.  Below are listed some
   generic recommendations:

   W_REC#1:  IPv6 must be supported on the WLAN interface.  In
             particular, WLAN interface must behave properly when only
             an IPv6 connectivity is provided.

                Some tests revealed that IPv4 configuration is required
                to enable IPv6-only connectivity.  Indeed, some cellular
                handsets can access a WLAN IPv6-only network by
                configuring first a static IPv4 address.  Once the
                device is connected to the network and the wlan0
                interface got an IPv6 global address, the IPv4 address
                can be deleted from the configuration.  This avoids the
                device to ask automatically for a DHCPv4 server, and
                allows to connect to IPv6-only networks.  Failing to
                configure an IPv4 address on the interface must not
                prohibit using IPv6 on the same interface.

   W_REC#2:  If the device receives the DNS information in several
             channels for the same interface, the following preference
             order must be followed:

                1.  RA

                2.  DHCPv6

3.  Advanced Recommendations

   This section identifies a set of advanced recommendations to fulfill
   requirements of critical services such as VoLTE.

   A_REC#1:  The cellular host must support ROHC RTP Profile (0x0001)
             and ROHC UDP Profile (0x0002) for IPv6 ([RFC5795]).  Other
             ROHC profiles may be supported.

                Bandwidth in cellular networks must be optimized as much
                as possible.  ROHC provides a solution to reduce
                bandwidth consumption and to reduce the impact of having
                bigger packet headers in IPv6 compared to IPv4.

                "RTP/UDP/IP" ROHC profile (0x0001) to compress RTP
                packets and "UDP/IP" ROHC profile (0x0002) to compress
                RTCP packets are required for Voice over LTE (VoLTE) by
                IR.92.4.0 section 4.1 [IR92].  Note, [IR92] indicates
                also the host must be able to apply the compression to
                packets that are carried over the radio bearer dedicated
                for the voice media.

   A_REC#2:  The cellular host should support PCP [RFC6887].

                The support of PCP is seen as a driver to save battery
                consumption exacerbated by keepalive messages.  PCP also
                gives the possibility of enabling incoming connections
                to the cellular device.  Indeed, because several
                stateful devices may be deployed in wireless networks
                (e.g., NAT and/or Firewalls), PCP can be used by the
                cellular host to control network-based NAT and Firewall
                functions which will reduce per-application signaling
                and save battery consumption.

                According to [Power], the consumption of a cellular
                device with a keep-alive interval equal to 20 seconds
                (that is the default value in [RFC3948] for example) is
                29 mA (2G)/34 mA (3G).  This consumption is reduced to
                16 mA (2G)/24 mA (3G) when the interval is increased to
                40 seconds, to 9.1 mA (2G)/16 mA (3G) if the interval is
                equal to 150 seconds, and to 7.3 mA (2G)/14 mA (3G) if
                the interval is equal to 180 seconds.  When no keep-
                alive is issued, the consumption would be 5.2 mA
                (2G)/6.1 mA (3G).  The impact of keepalive messages
                would be more severe if multiple applications are
                issuing those messages (e.g., SIP, IPsec, etc.).

   A_REC#3:  In order for host-based validation of DNS Security
             Extensions (DNSSEC) to continue to function in an IPv6-only
             with NAT64 deployment context, the cellular host should
             embed a DNS64 function ([RFC6147]).

                This is called "DNS64 in stub-resolver mode" in

                As discussed in Section 5.5 of [RFC6147], a security-
                aware and validating host has to perform the DNS64
                function locally.

                Because synthetic AAAA records cannot be successfully
                validated in a host, learning the PREFIX64 used to
                construct IPv4-converted IPv6 addresses allows the use
                of DNSSEC [RFC4033] [RFC4034], [RFC4035].  Means to
                configure or discover a PREFIX64 are required on the
                cellular device as discussed in C_REC#8.

                [RFC7051] discusses why a security-aware and validating
                host has to perform the DNS64 function locally and why
                it has to be able to learn the proper PREFIX64(s).

   A_REC#4:  When the cellular host is dual-stack connected (i.e.,
             configured with an IPv4 address and IPv6 prefix), it should
             support means to prefer native IPv6 connection over
             connection established through translation devices (e.g.,
             NAT44 and NAT64).

                When both IPv4 and IPv6 DNS servers are configured, a
                dual-stack host must contact first its IPv6 DNS server.

                Cellular hosts should follow the procedure specified in
                [RFC6724] for source address selection.

   A_REC#5:  The cellular host should support Happy Eyeballs procedure
             defined in [RFC6555].

4.  Recommendations for Cellular Devices with LAN Capabilities

   This section focuses on cellular devices (e.g., CPE, smartphones, or
   dongles with tethering features) which provide IP connectivity to
   other devices connected to them.  In such case, all connected devices
   are sharing the same 2G, 3G or LTE connection.  In addition to the
   generic recommendations listed in Section 2, these cellular devices
   have to meet the recommendations listed below.

   L_REC#1:  The cellular device must support Prefix Delegation
             capabilities [RFC3633] and must support Prefix Exclude
             Option for DHCPv6-based Prefix Delegation as defined in
             [RFC6603].  Particularly, it must behave as a Requesting

                Cellular networks are more and more perceived as an
                alternative to fixed networks for home IP-based services
                delivery; especially with the advent of smartphones and
                3GPP data dongles.  There is a need for an efficient
                mechanism to assign shorter prefix than /64 to cellular
                hosts so that each LAN segment can get its own /64
                prefix and multi-link subnet issues to be avoided.

                In case a prefix is delegated to a cellular host using
                DHCPv6, the cellular device will be configured with two

                   (1) one for 3GPP link allocated using SLAAC mechanism
                   (2) another one delegated for LANs acquired during
                   Prefix Delegation operation.

                Note that the 3GPP network architecture requires both
                the WAN (Wide Area Network) and the delegated prefix to
                be aggregatable, so the subscriber can be identified
                using a single prefix.

                Without the Prefix Exclude Option, the delegating router
                (GGSN/PGW) will have to ensure [RFC3633] compliancy
                (e.g., halving the delegated prefix and assigning the
                WAN prefix out of the 1st half and the prefix to be
                delegated to the terminal from the 2nd half).

                Because Prefix Delegation capabilities may not be
                available in some attached networks, L_REC#3 is strongly
                recommended to accommodate early deployments.

   L_REC#2:  The cellular CPE must be compliant with the requirements
             specified in [RFC6204]. [RFC7084].

                There are several deployments, particularly in emerging
                countries, that relies on mobile networks to provide
                broadband services (e.g., customers are provided with
                mobile CPEs).

                Note, even if RFC7084 obsoletes [RFC6204], this profile does not require RFC7084 because IPv4 service
                continuity techniques used listed in [RFC7084] because those
                are specific to fixed networks.  IPv4 service continuity
                techniques specific to the mobile networks are not the same as included
                in fixed networks. this profile.

   L_REC#3:  For deployments requiring to share the same /64 prefix, the
             cellular device should support [RFC7278] to enable sharing
             a /64 prefix between the 3GPP interface towards the GGSN/
             PGW (WAN interface) and the LAN interfaces.

                Prefix Delegation (refer to L_REC#1) is the target
                solution for distributing prefixes in the LAN side but,
                because the device may attach to earlier 3GPP release
                networks, a mean to share a /64 prefix is also
                recommended [RFC7278].

                [RFC7278] must be invoked only if Prefix Delegation is
                not in use.

   L_REC#4:  In order to ensure IPv4 service continuity in an IPv6-only
             deployment context, the cellular device should support the
             Customer Side Translator (CLAT) [RFC6877].

                Various IP devices are likely to be connected to
                cellular device, acting as a CPE.  Some of these devices
                can be dual-stack, others are IPv6-only or IPv4-only.
                IPv6-only connectivity for cellular device does not
                allow IPv4-only sessions to be established for hosts
                connected on the LAN segment of cellular devices.

                In order to allow IPv4 sessions establishment initiated
                from devices located on LAN segment side and target IPv4
                nodes, a solution consists in integrating the CLAT
                function in the cellular device.  As elaborated in
                Section 2, the CLAT function allows also IPv4
                applications to continue running over an IPv6-only host.

                The IPv4 Service Continuity Prefix used by CLAT is
                defined in [RFC7335].

   L_REC#5:  If a RA MTU is advertised from the 3GPP network, the
             cellular device should relay that upstream MTU information
             to the downstream attached LAN devices in RA.

                Receiving and relaying RA MTU values facilitates a more
                harmonious functioning of the mobile core network where
                end nodes transmit packets that do not exceed the MTU
                size of the mobile network's GTP tunnels.

                [TS.23060] indicates providing a link MTU value of 1358
                octets to the 3GPP cellular device will prevent the IP
                layer fragmentation within the transport network between
                the cellular device and the GGSN/PGW.

5.  APIs & Applications Recommendations

   The use of address family dependent APIs (Application Programming
   Interfaces) or hard-coded IPv4 address literals may lead to broken
   applications when IPv6 connectivity is in use.  This section
   identifies a set of recommendations aiming to minimize broken
   applications when the cellular device is attached to an IPv6 network.

   APP_REC#1:  Name resolution libraries must support both IPv4 and

                  In particular, the cellular host must support

   APP_REC#2:  Applications provided by the mobile device vendor must be
               independent of the underlying IP address family.

                  This means applications must be IP version agnostic.

   APP_REC#3:  Applications provided by the mobile device vendor that
               use Uniform Resource Identifiers (URIs) must follow
               [RFC3986] and its updates.  For example, SIP applications
               must follow the correction defined in [RFC5954].

6.  Security Considerations

   The security considerations identified in [RFC7066] and [RFC6459] are
   to be taken into account.

   Security-related considerations that apply when

   In the case of cellular device
   provides devices that provide LAN features are specified features, compliance
   with L_REC#2 entails compliance with [RFC7084], which in turn
   recommends compliance with Recommended Simple Security Capabilities
   in Customer Premises Equipment (CPE) for Providing Residential IPv6
   Internet Service [RFC6092].  Therefore, the security considerations
   in Section 6 of [RFC6092] are relevant.  In particular, it bears
   repeating here that the true impact of stateful filtering may be a
   reduction in security, and that IETF make no statement, expressed or
   implied, as to whether using the capabilities described in any of
   these documents ultimately improves security for any individual users
   or for the Internet community as a whole.

   The cellular host must be able to generate IPv6 addresses which
   preserve privacy.  The activation of privacy extension (e.g., using
   [RFC7217]) makes it more difficult to track a host over time when
   compared to using a permanent Interface Identifier.  Tracking a host
   is still possible based on the first 64 bits of the IPv6 address.
   Means to prevent against such tracking issues may be enabled in the
   network side.  Note, privacy extensions are required by regulatory
   bodies in some countries.

   Host-based validation of DNSSEC is discussed in A_REC#3 (see
   Section 3).

7.  IANA Considerations

   This document does not require any action from IANA.

8.  Acknowledgements

   Many thanks to C.  Byrne, H.  Soliman, H.  Singh, L.  Colliti, T.
   Lemon, B.  Sarikaya, M.  Mawatari, M.  Abrahamsson, P.  Vickers, V.

   Kuarsingh, E.  Kline, S.  Josefsson, A.  Baryun, J.  Woodyatt, and T.
   Kossut, and B.  Stark for the discussion in the v6ops mailing list.

   Thanks to A.  Farrel, B.  Haberman and K.  Moriarty for the comments
   during the IESG review.

   Special thanks to T.  Savolainen, J.  Korhonen, J.  Jaeggli, and F.
   Baker for their detailed reviews and comments.

9.  References

9.1.  Normative References

   [IR92]     GSMA, "IR.92.V4.0 - IMS Profile for Voice and SMS", March
              2011, <http://www.gsma.com/newsroom/

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IP Version 6", RFC 3596,
              October 2003.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC5795]  Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust
              Header Compression (ROHC) Framework", RFC 5795, March

   [RFC5954]  Gurbani, V., Carpenter, B., and B. Tate, "Essential
              Correction for IPv6 ABNF and URI Comparison in RFC 3261",
              RFC 5954, August 2010.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6603]  Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
              "Prefix Exclude Option for DHCPv6-based Prefix
              Delegation", RFC 6603, May 2012.

   [RFC7066]  Korhonen, J., Arkko, J., Savolainen, T., and S. Krishnan,
              "IPv6 for Third Generation Partnership Project (3GPP)
              Cellular Hosts", RFC 7066, November 2013.

              3GPP, "General Packet Radio Service (GPRS); Service
              description; Stage 2", September 2011,

              3GPP, "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", September 2011,

              3GPP, "Mobile radio interface Layer 3 specification; Core
              network protocols; Stage 3", June 2011,

9.2.  Informative References

   [Power]    Haverinen, H., Siren, J., and P. Eronen, "Energy
              Consumption of Always-On Applications in WCDMA Networks",
              April 2007, <http://ieeexplore.ieee.org/xpl/

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3948]  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
              Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
              3948, January 2005.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements", RFC
              4033, March 2005.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, March 2005.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

   [RFC6092]  Woodyatt, J., "Recommended Simple Security Capabilities in
              Customer Premises Equipment (CPE) for Providing
              Residential IPv6 Internet Service", RFC 6092, January

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              April 2011.

   [RFC6204]  Singh, H., Beebee, W., Donley, C., Stark, B., and O.
              Troan, "Basic Requirements for IPv6 Customer Edge
              Routers", RFC 6204, April 2011.

   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
              Requirements", RFC 6434, December 2011.

   [RFC6459]  Korhonen, J., Soininen, J., Patil, B., Savolainen, T.,
              Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, January 2012.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, April 2012.

   [RFC6724]  Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, September 2012.

   [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
              Combination of Stateful and Stateless Translation", RFC
              6877, April 2013.

   [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)", RFC 6887, April

   [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              the IPv6 Prefix Used for IPv6 Address Synthesis", RFC
              7050, November 2013.

   [RFC7051]  Korhonen, J. and T. Savolainen, "Analysis of Solution
              Proposals for Hosts to Learn NAT64 Prefix", RFC 7051,
              November 2013.

   [RFC7084]  Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
              Requirements for IPv6 Customer Edge Routers", RFC 7084,
              November 2013.

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217, April 2014.

   [RFC7225]  Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
              Port Control Protocol (PCP)", RFC 7225, May 2014.

   [RFC7278]  Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6
              /64 Prefix from a Third Generation Partnership Project
              (3GPP) Mobile Interface to a LAN Link", RFC 7278, June

   [RFC7335]  Byrne, C., "IPv4 Service Continuity Prefix", RFC 7335,
              August 2014.

              3GPP, "Architecture enhancements for non-3GPP accesses",
              September 2011,

Authors' Addresses

   David Binet
   France Telecom

   EMail: david.binet@orange.com

   Mohamed Boucadair
   France Telecom
   Rennes  35000

   EMail: mohamed.boucadair@orange.com

   Ales Vizdal
   Deutsche Telekom AG

   EMail: ales.vizdal@t-mobile.cz
   Gang Chen
   China Mobile

   EMail: phdgang@gmail.com

   Nick Heatley
   The Point, 37 North Wharf Road,
   London  W2 1AG

   EMail: nick.heatley@ee.co.uk

   Ross Chandler
   eircom | meteor
   St. John's Road
   Dublin 8

   EMail: ross@eircom.net