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Versions: 00 01 02 03 04 05 06 draft-ietf-v6ops-3gpp-eps

Individual Submission                                   J. Korhonen, Ed.
Internet-Draft                                               J. Soininen
Intended status: Informational                    Nokia Siemens Networks
Expires: November 28, 2010                                      B. Patil
                                                           T. Savolainen
                                                                G. Bajko
                                                            K. Iisakkila
                                                                   Nokia
                                                            May 27, 2010


                   IPv6 in 3GPP Evolved Packet System
                    draft-korhonen-v6ops-3gpp-eps-02

Abstract

   The increased use of data services, growth of subscribers in 3GPP
   based mobile networks, and the impending exhaustion of available IPv4
   addresses from the registries is driving the need to specify the
   transition to IPv6 solutions in 3GPP network architectures.  This
   document describes the support for IPv6 in 3GPP network architectures
   and a solution to transition to IPv6 using a dual-stack approach.

Status of this Memo

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

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

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

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

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

   This Internet-Draft will expire on November 28, 2010.

Copyright Notice




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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  3GPP Terminology and Concepts  . . . . . . . . . . . . . . . .  4
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  The concept of APN . . . . . . . . . . . . . . . . . . . .  6
   3.  IP over 3GPP GPRS  . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Introduction to 3GPP GPRS  . . . . . . . . . . . . . . . .  7
     3.2.  PDP Context  . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  IP over 3GPP EPS . . . . . . . . . . . . . . . . . . . . . . . 10
     4.1.  Introduction to 3GPP EPS . . . . . . . . . . . . . . . . . 10
     4.2.  PDN Connection . . . . . . . . . . . . . . . . . . . . . . 11
     4.3.  EPS bearer model . . . . . . . . . . . . . . . . . . . . . 11
   5.  Address Management . . . . . . . . . . . . . . . . . . . . . . 12
     5.1.  IPv4 Address Configuration . . . . . . . . . . . . . . . . 12
     5.2.  IPv6 Address Configuration . . . . . . . . . . . . . . . . 12
     5.3.  Prefix Delegation  . . . . . . . . . . . . . . . . . . . . 13
   6.  3GPP Dual-Stack Approach to IPv6 . . . . . . . . . . . . . . . 13
     6.1.  3GPP Networks Prior to Release-8 . . . . . . . . . . . . . 13
     6.2.  3GPP Release-8 and -9 Networks . . . . . . . . . . . . . . 14
     6.3.  PDN Connection Establishment Process . . . . . . . . . . . 15
     6.4.  Mobility of 3GPP IPv4v6 Type of Bearers  . . . . . . . . . 18
   7.  Dual-Stack Approach to IPv6 Transition in 3GPP Networks  . . . 18
   8.  Deployment issues  . . . . . . . . . . . . . . . . . . . . . . 19
     8.1.  Overlapping IPv4 Addresses . . . . . . . . . . . . . . . . 19
     8.2.  IPv6 for transport . . . . . . . . . . . . . . . . . . . . 20
     8.3.  Operational Aspects of Running Dual-Stack Networks . . . . 21
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 21
   11. Summary and Conclusion . . . . . . . . . . . . . . . . . . . . 22
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
   13. Informative References . . . . . . . . . . . . . . . . . . . . 22
   Appendix A.  Transition scenarios discussed in 3GPP  . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25



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1.  Introduction

   IPv6 has been specified in the 3rd Generation Partnership Project
   (3GPP) standards since the early architectures developed for R99
   General Packet Radio Service (GPRS).  However, the support for IPv6
   in commercially deployed networks is nearly non-existent.  There are
   many factors that can be attributed to the lack of IPv6 deployment in
   3GPP networks.  The most relevant one is essentially the same as the
   reason for IPv6 not being deployed by other networks as well, i.e.
   the lack of business and commercial incentives for deployment. 3GPP
   network architectures have also evolved since 1999 (since R99).  The
   most recent version of the 3GPP architecture, the Evolved Packet
   System (EPS), which is commonly referred as SAE, LTE or Release-8, is
   a packet centric architecture.  The number of subscribers and devices
   that are using the 3GPP networks for Internet connectivity and data
   services has also increased significantly.  With the subscriber
   growth numbers projected to increase even further and the IPv4
   addresses depletion problem looming in the near term, 3GPP operators
   and vendors have started the process of identifying the scenarios and
   solutions needed to transition to IPv6.

   This document describes the establishment of IP connectivity in 3GPP
   network architectures, specifically in the context of IP bearers for
   3GPP GPRS and for 3GPP EPS.  It provides an overview of how IPv6 is
   supported as per the current set of 3GPP specifications.  A solution
   to transitioning to IPv6 based on a dual-stack technology is
   described as well as some of the issues and concerns with respect to
   deployment and shortage of private IPv4 addresses within a single
   network domain.

   The IETF has specified a set of tools and mechanisms that can be
   utilized for transitioning to IPv6.  In addition to the dual-stack
   technology, the two alternative categories for the transition are
   encapsulation and translation.  Most of the mechanisms available in
   the toolbox can be categorized as belonging to either one of these.
   The IETF continues to specify additional solutions for enabling the
   transition based on the deployment scenarios and operator/ISP
   requirements.  The 3GPP scenarios for transition, described in
   Appendix A here, can be addressed using transition mechanisms that
   are already available in the toolbox.  The objective of transition to
   IPv6 in 3GPP networks is to ensure that:

   1.  Legacy devices and hosts which have an IPv4 only stack will
       continue to be provided with IP connectivity to the Internet and
       services,

   2.  Devices which are dual-stack can access the Internet either via
       IPv6 or IPv4.  The choice of using IPv6 or IPv4 depends on the



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       capability of:

       A.  the application on the host,

       B.  the support for IPv4 and IPv6 bearers by the network and/or,

       C.  the capability of the server(s) and other end points.

   3GPP networks are capable of providing a host with IPv4 and IPv6
   connectivity today, albeit in many cases with upgrades to network
   elements such as the SGSN and GGSN.


2.  3GPP Terminology and Concepts

2.1.  Terminology

   Access Point Name

      Access Point Name (APN) is a fully qualified domain name and
      resolves to a specific gateway in an operators network.  The APNs
      are piggybacked on the administration of the DNS namespace.

   Packet Data Protocol Context

      A Packet Data Protocol (PDP) Context is the equivalent of a
      virtual connection between the host and a gateway.

   General Packet Radio Service

      General Packet Radio Service (GPRS) is a packet oriented mobile
      data service available to users of the 2G and 3G cellular
      communication systems Global System for Mobile communications
      (GSM), and specified by 3GPP.

   Packet Data Network

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

   Gateway GPRS Support Node

      Gateway GPRS Support Node (GGSN) is a gateway function in GPRS,
      which provides connectivity to Internet or other PDNs.  The host



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      attaches to a GGSN identified by an APN assigned to it by an
      operator.  The GGSN also serves as the topological anchor for
      addresses/prefixes assigned to the mobile host.

   Packet Data Network Gateway

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

   Serving Gateway

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

   Serving Gateway Support Node

      Serving Gateway Support Node (SGSN) is a network element that is
      located between the radio access network (RAN) and the gateway
      (GGSN).  A per mobile host point to point (p2p) tunnel between the
      GGSN and SGSN transports the packets between the mobile host and
      the gateway.

   GPRS tunnelling protocol

      GPRS Tunnelling Protocol (GTP) [3GPP.29.060] is a tunnelling
      protocol defined by 3GPP.  It is a network based mobility protocol
      and similar to Proxy Mobile IPv6 (PMIPv6) [RFC5213].  However, GTP
      also provides functionality beyond mobility such as inband
      signaling related to Quality of Service (QoS) and charging among
      others.

   Evolved Packet System

      Evolved Packet System (EPS) is an evolution of the 3G GPRS system
      characterized by higher-data-rate, lower-latency, packet-optimized
      system that supports multiple Radio Access Technologies (RAT).
      The EPS comprises the Evolved Packet Core (EPC) together with the
      evolved radio access network (E-UTRA and E-UTRAN).





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   Mobility Management Entity

      Mobility Management Entity (MME) is a network element that is
      responsible for control plane functionalities, including
      authentication, authorization, bearer management, layer-2
      mobility, etc.  The MME is essentially the control plane part of
      the GPRS' SGSN and not located on the user plane data path, i.e.
      user plane traffic bypasses the MME.

   UMTS Terrestrial Radio Access Network

      UMTS Terrestrial Radio Access Network (UTRAN) is communications
      network, commonly referred to as 3G, and consists of NodeBs (3G
      base station) and Radio Network Controllers (RNC) which make up
      the UMTS radio access network.  The UTRAN allows connectivity
      between the mobile host/device and the core network.

   Evolved UTRAN

      Evolved UTRAN (E-UTRAN) is communications network, sometimes
      referred to as 4G, and consists of eNodeBs (4G base station) which
      make up the E-UTRAN radio access network.  The E-UTRAN allows
      connectivity between the mobile host/device and the core network.

   GSM EDGE Radio Access Network

      GSM EDGE Radio Access Network (GERAN) is communications network,
      commonly referred to as 2G or 2.5G, and consists of base stations
      and Base Station Controllers (BSC) which make up the GSM EDGE
      radio access network.  The GERAN allows connectivity between the
      mobile host/device and the core network.

   UE, MS, MN and Mobile

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

2.2.  The concept of APN

   The Access Point Name (APN) essentially refers to a gateway in the
   3GPP network.  The 'complete' APN is expressed in a form of a Fully
   Qualified Domain Name (FQDN) and also piggybacked on the
   administration of the DNS namespace, thus effectively allowing the
   discovery of gateways using the DNS.  Mobile hosts/devices can choose
   to attach to a specific gateway in the packet core.  The gateway



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   provides connectivity to the Packet Data Network (PDN) such as the
   Internet.  An operator may also include gateways which do not provide
   Internet connectivity, rather a connectivity to closed network
   providing a set of operator's own services.  A mobile host/device can
   be attached to one or more gateways simultaneously.  The gateway in a
   3GPP network is the GGSN or PDN-GW.  Figure 1 below illustrates the
   APN-based network connectivity concept.

                                                            .--.
                                                          _(.   `)
                        .--.         +------------+     _(   PDN  `)_
                      _(Core`.       |GW1         |====(  Internet   `)
           +---+     (   NW   )------|APN=internet|   ( `  .        )  )
   [MN]~~~~|RAN|----( `  .  )  )--+  +------------+    `--(_______)---'
    ^      +---+     `--(___.-'   |
    |                             |                       .--.
    |                             |  +----------+       _(.PDN`)
    |                             +--|GW2       |     _(Operator`)_
    |                                |APN=OpServ|====(  Services   `)
   MN is attached                    +----------+   ( `  .        )  )
   to GW1 and GW2                                    `--(_______)---'
   simultaneously

   Figure 1: Mobile host/device attached to multiple APNs simultaneously


3.  IP over 3GPP GPRS

3.1.  Introduction to 3GPP GPRS

   A simplified 2G/3G GPRS architecture is illustrated in Figure 2.
   This architecture basically covers the GPRS core network since R99 to
   Release-7, and radio access technologies such as GSM (2G), EDGE (2G),
   WCDMA (3G) and HSPA (3G).  The architecture shares obvious
   similarities with the Evolved Packet System (EPS) as will be seen in
   Section 4.  Based on Gn/Gp interfaces, the GPRS core network
   functionality is logically implemented on two network nodes, the SGSN
   and the GGSN.













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                    3G                                     .--.
              Uu  +-----+  Iu  +----+      +----+        _(    `.
   [TE]+[MT]~~|~~~|UTRAN|--|---|SGSN|--|---|GGSN|--|----(   PDN  )
                  +-----+      +----+  Gn  +----+  Gi  ( `  .  )  )
                               / |                      `--(___.-'
                     2G    Gb--  |
                    +---+    /   --Gp
     [TE]+[MT]~~|~~~|BSS|___/    |
                Um  +---+       .--.
                              _(.   `)
                            _( [GGSN] `)_
                           (    other    `)
                          ( `  . PLMN   )  )
                           `--(_______)---'

         Figure 2: Overview of the 2G/3G GPRS Logical Architecture

   Gn/Gp:  These interfaces provide a network based mobility service for
           a mobile host and are used between a SGSN and a GGSN.  The Gn
           interface is used when GGSN and SGSN are located inside one
           operator (i.e.  PLMN).  The Gp-interface is used if the GGSN
           and the SGSN are located in different operator domains (i.e.
           'other' PLMN).  GTP protocol is defined for the Gn/Gp
           interfaces (both GTP-C for the control plane and GTP-U for
           the user plane).

   Gb:     Is the Base Station System (BSS) to SGSN interface, which is
           used to carry information concerning packet data transmission
           and layer-2 mobility management.  The Gb-interface is based
           on either on Frame Relay or IP.

   Iu:     Is the Radio Network System (RNS) to SGSN interface, which is
           used to carry information concerning packet data transmission
           and layer-2 mobility management.  The user plane part of the
           Iu-interface (actually the Iu-PS) is based on GTP-U.  The
           control plane part of the Iu-interface is based on Radio
           Access Network Application Protocol (RANAP).

   Gi:     It is the interface between the GGSN and a PDN.  The PDN may
           be an operator external public or private packet data network
           or an intra-operator packet data network.

   Uu/Um:  Are either 2G or 3G radio interfaces between a mobile
           terminal and a respective radio access network.

   The SGSN is responsible for the delivery of data packets from and to
   the mobile hosts within its geographical service area when a direct
   tunnel option is not used.  If the direct tunnel is used, then the



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   user plane goes directly between the RNS and the GGSN.  The control
   plane traffic always goes through the SGSN.  For each mobile host
   connected with the GPRS, at any given point of time, there is only
   one SGSN.

3.2.  PDP Context

   A PDP context is an association between a mobile host represented by
   one IPv4 address and/or one /64 IPv6 prefix and a PDN represented by
   an APN.  Each PDN can be accessed via a gateway (typically a GGSN or
   PDN-GW).  On the device/mobile host a PDP context is equivalent to a
   virtual interface/connection.  A host may hence be attached to one or
   more gateways via separate virtual interfaces/connections, i.e.  PDP
   contexts.  Each primary PDP context has its own IPv4 address and/or
   one /64 IPv6 prefix assigned to it by the PDN and anchored in the
   corresponding gateway.  Applications on the host use the appropriate
   PDP context (virtual interface) for connectivity to a specific PDN.
   Figure 3 represents a high level view of what a PDP context implies
   in 3GPP networks.

   Y
   |                               +---------+       .--.
   |--+ __________________________ | APNx in |     _(    `.
   |  |O__________________________)| GGSN /  |----(Internet)
   |MS|                            | PDN-GW  |   ( `  .  )  )
   |/ |                            +---------+    `--(___.-'
   |UE| _______________________ +---------+          .--.
   |  |O_______________________)| APNy in |        _(Priv`.
   +--+                         | GGSN /  |-------(Network )
                                | PDN-GW  |      ( `  .  )  )
                                +---------+       `--(___.-'

           Figure 3: PDP contexts between the MS/UE and gateway

   In the above figure there are two PDP contexts at the MS/UE (UE=User
   Equipment in 3GPP parlance).  The PDP context that is connected to
   APNx provided Internet connectivity and the other PDP context
   provides connectivity to a private IP network (as an example this
   network may include operator specific services such as MMS (Multi
   media service).  An application on the host such as a web browser
   would use the PDP context that provides Internet connectivity for
   accessing services on the Internet.  An application such as MMS would
   use APNy in the figure above because the service is provided through
   the private network.







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4.  IP over 3GPP EPS

4.1.  Introduction to 3GPP EPS

   In its most basic form, the EPS architecture consists of only two
   nodes on the user plane, a base station and a core network Gateway
   (GW).  The basic EPS architecture is illustrated in Figure 4.  The
   Mobility Management Entity (MME) node performs control-plane
   functionality and is separated from the node(s) that performs bearer-
   plane functionality (GW), with a well-defined open interface between
   them (S11).  The optional interface S5 can be used to split the
   Gateway (GW) into two separate nodes, the Serving Gateway (SGW) and
   the PDN-GW.  This allows independent scaling and growth of traffic
   throughput and control signal processing.  The functional split of
   gateways also allows operators to choose optimized topological
   locations of nodes within the network in order to optimize the
   network in different aspects.

                                                             +--------+
                         S1-MME  +-------+  S11              |   IP   |
                       +----|----|  MME  |---|----+          |Services|
                       |         |       |        |          +--------+
                       |         +-------+        |               |SGi
    +----+ LTE-Uu +-------+ S1-U               +-------+  S5  +-------+
    |MN  |----|---|eNodeB |---|----------------| SGW   |--|---|PDN-GW |
    |    |========|=======|====================|=======|======|       |
    +----+        +-------+DualStack EPS Bearer+-------+      +-------+

                Figure 4: EPS Architecture for 3GPP Access

   S5:      It provides user plane tunnelling and tunnel management
            between SGW and PDN-GW, using GTP or PMIPv6 as the network
            based mobility management protocol.

   S1-U:    Provides user plane tunnelling and inter eNodeB path
            switching during handover between eNodeB and SGW, using the
            GTP-U protocol (GTP user plane).

   S1-MME:  Reference point for the control plane protocol between
            eNodeB and MME.

   SGi:     It is the interface between the PDN-GW and the packet data
            network.  Packet data network may be an operator external
            public or private packet data network or an intra operator
            packet data network.

   The eNodeB is a base station entity that supports the Long Term
   Evolution (LTE) air interface and includes functions for radio



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   resource control, user plane ciphering, and other lower layer
   functions.  MME is responsible for control plane functionalities,
   including authentication, authorization, bearer management, layer-2
   mobility, etc.

   The SGW is the Mobility Anchor point for layer-2 mobility.  For each
   MN connected with the EPS, at any given point of time, there is only
   one SGW.

4.2.  PDN Connection

   A PDN connection is an association between a mobile host represented
   by one IPv4 address and/or one /64 IPv6 prefix, and a PDN represented
   by an APN.  Each PDN can be accessed via a gateway (a PDN-GW).  PDN
   is responsible for the IP address/prefix allocation to the mobile
   host.  On the device/mobile host a PDN connection is equivalent to a
   virtual interface/connection.  A host may hence be attached to one or
   more gateways via separate virtual interfaces/connections, i.e.  PDN
   connection.  Each PDP connection has its own IP address/prefix
   assigned to it by the PDN and anchored in the corresponding gateway.
   Applications on the host use the appropriate PDN connection (virtual
   interface) for connectivity.  The PDN connection is the EPC
   equivalent of the GPRS PDP context.

4.3.  EPS bearer model

   The logical concept of a bearer has been defined to be an aggregate
   of one or more IP flows related to one or more services.  An EPS
   bearer exists between the Mobile Node (MN i.e. a mobile host) and the
   PDN-GW and is used to provide the same level of packet forwarding
   treatment to the aggregated IP flows constituting the bearer.
   Services with IP flows requiring a different packet forwarding
   treatment would therefore require more than one EPS bearer.  The
   mobile host performs the binding of the uplink IP flows to the bearer
   while the PDN-GW performs this function for the downlink packets.

   In order to provide low latency for always on connectivity, a default
   bearer will be provided at the time of startup and an IPv4 address
   and/or IPv6 prefix gets assigned to the mobile host (this is
   different from GPRS, where mobile hosts are not automatically
   assigned with an IP address or prefix).  This default bearer will be
   allowed to carry all traffic which is not associated with a dedicated
   bearer.  Dedicated bearers are used to carry traffic for IP flows
   that have been identified to require a specific packet forwarding
   treatment.  They may be established at the time of startup; for
   example, in the case of services that require always-on connectivity
   and better QoS than that provided by the default bearer.  The default
   bearer and the dedicated bearer(s) associated to it share the same IP



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   address(es)/prefix.

   An EPS bearer is referred to as a GBR bearer if dedicated network
   resources related to a Guaranteed Bit Rate (GBR) value that is
   associated with the EPS bearer are permanently allocated (e.g. by an
   admission control function in the eNodeB) at bearer establishment/
   modification.  Otherwise, an EPS bearer is referred to as a non-GBR
   bearer.  The default bearer is always non-GBR, with the resources for
   the IP flows not guaranteed at eNodeB, and with no admission control.
   However, the dedicated bearer can be either GBR or non-GBR.  A GBR
   bearer has a Guaranteed Bit Rate (GBR) and Maximum Bit Rate (MBR)
   while more than one non-GBR bearer belonging to the same UE shares an
   Aggregate Maximum Bit Rate (AMBR).  Non-GBR bearers can suffer packet
   loss under congestion while GBR bearers are immune to such losses.


5.  Address Management

5.1.  IPv4 Address Configuration

   Mobile host's IPv4 address configuration is essentially always
   conducted during PDP context/EPS bearer setup procedures (on
   layer-2).  DHCPv4-based [RFC2131] address configuration is supported
   by the 3GPP specifications, but is not used in wide scale.  The
   mobile host must always support layer-2 based address configuration,
   since DHCPv4 is optional for both mobile hosts and networks.

5.2.  IPv6 Address Configuration

   IPv6 Stateless Address Autoconfiguration (SLAAC) is the only
   supported address configuration mechanisms [RFC4862].  Stateful
   DHCPv6-based address configuration is not supported by 3GPP
   specifications [RFC3315].  On the other hand, Stateless DHCPv6-
   service to obtain other configuration information is supported
   [RFC3736].  This implies that the M-bit must always be set to zero
   and the O-bit may be set to one in the Router Advertisement (RA) sent
   to the UE.

   3GPP network allocates each default bearer a unique /64 prefix, and
   uses layer-2 signaling to suggest user equipment an Interface
   Identifier that is guaranteed not to conflict with gateway's
   Interface Identifier.  The UE may configure link local address using
   this Interface Identifier, but is allowed to use also other Interface
   Identifiers and as many globally scoped addresses as it needs.  There
   is no restriction, for example, of using Privacy Extension for SLAAC
   [RFC4941] or other similar types of mechamisms.

   In the 3GPP link model the /64 prefix assigned to the UE is always



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   off-link (i.e. the L-bit in the Prefix Information Option (PIO) in
   the RA must be set to zero).  If the advertised prefix is used for
   SLAAC then the A-bit in the PIO must be set to one.  The details of
   the 3GPP link-model and address configuration is described in Section
   11.2.1.3.2a of [3GPP.29.061].

   The current 3GPP architecture limits number of prefixes in each
   bearer to a single /64 prefix.  Therefore, multi-homing within a
   single bearer is not possible.  Renumbering without closing layer-2
   connection is also not possible.  The lifetime of /64 prefix is bound
   to lifetime of layer-2 connection even if the advertised prefix
   lifetime would be longer than the layer-2 connection lifetime.

5.3.  Prefix Delegation

   Prefix delegation is not covered yet by 3GPP specifications as of
   Release-9.  The /64 prefix allocated for each default bearer may be
   shared to local area network by user equipment implementing Neighbor
   Discovery proxy (ND proxy) [RFC4389] functionality.  Discussion is
   ongoing in 3GPP to add the prefix delegation support, e.g. using the
   DHCPv6-based prefix delegation [RFC3633], which is likely to be the
   adopted solution as well.


6.  3GPP Dual-Stack Approach to IPv6

6.1.  3GPP Networks Prior to Release-8

   3GPP standards prior to Release-8 provide IPv6 access for cellular
   devices with PDP contexts of type IPv6 [3GPP.23.060].  For dual-stack
   access, a PDP context of type IPv6 is established in parallel to the
   PDP context of type IPv4, as shown in Figure 5 and Figure 6.  For
   IPv4-only service, connections are created over the PDP context of
   type IPv4 and for IPv6-only service connections are created over the
   PDP context of type IPv6.  The two PDP contexts of different type may
   use the same APN (and the gateway), however, this aspect is not
   explicitly defined in standards.  Therefore, cellular device and
   gateway implementations from different vendors may have varying
   support for this functionality.












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   Y                                        .--.
   |                                      _(IPv4`.
   |---+              +---+    +---+     (  PDN   )
   | D |~~~~~~~//-----|   |====|   |====( `  .  )  )
   | S | IPv4 context | S |    | G |     `--(___.-'
   |   |              | G |    | G |        .--.
   | M |              | S |    | S |      _(IPv6`.
   | N | IPv6 context | N |    | N |     (  PDN   )
   |///|~~~~~~~//-----|   |====|(s)|====( `  .  )  )
   +---+              +---+    +---+     `--(___.-'

    Figure 5: A dual-stack mobile host connecting to both IPv4 and IPv6
       Internet using parallel IPv4-only and IPv6-only PDP contexts


   Y
   |
   |---+              +---+    +---+
   | D |~~~~~~~//-----|   |====|   |        .--.
   | S | IPv4 context | S |    | G |      _( DS `.
   |   |              | G |    | G |     (  PDN   )
   | M |              | S |    | S |====( `  .  )  )
   | N | IPv6 context | N |    | N |     `--(___.-'
   |///|~~~~~~~//-----|   |====|   |
   +---+              +---+    +---+

   Figure 6: A dual-stack mobile host connecting to dual-stack Internet
            using parallel IPv4-only and IPv6-only PDP contexts

   The approach of having parallel IPv4 and IPv6 type of PDP contexts
   open is not optimal, because two PDP contexts require double the
   signaling and consume more network resources than a single PDP
   context.  However, these costs and complexities are lesser than what
   other transition solutions would incur.  In the figure above the IPv4
   and IPv6 PDP contexts are attached to the same GGSN.  While this is
   possible, the DS MS may be attached to different GGSNs in the
   scenario where one GGSN supports IPv4 PDN connectivity while another
   GGSN provides IPv6 PDN connectivity.

6.2.  3GPP Release-8 and -9 Networks

   Since 3GPP Release-8, the powerful concept of a dual-stack type of
   PDN connection and EPS bearer have been introduced [3GPP.23.401].
   This enables parallel use of both IPv4 and IPv6 on a single bearer
   (IPv4v6), as illustrated in Figure 7, and makes dual stack simpler
   than in earlier 3GPP releases.  As of Release-9, GPRS network nodes
   also support dual-stack type (IPv4v6) PDP contexts.




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   Y
   |
   |---+              +---+    +---+
   | D |              |   |    | P |        .--.
   | S |              |   |    | D |      _( DS `.
   |   | IPv4v6 (DS)  | S |    | N |     (  PDN   )
   | M |~~~~~~~//-----| G |====| - |====( `  .  )  )
   | N | bearer       | W |    | G |     `--(___.-'
   |///|              |   |    | W |
   +---+              +---+    +---+

   Figure 7: A dual-stack mobile host connecting to dual-stack Internet
                 using a single IPv4v6 type PDN connection

   The following is a description of the various PDP contexts/PDN bearer
   types that are specified by 3GPP:

   1.  For 2G/3G access to GPRS core (SGSN/GGSN) pre-Release-9 there are
       two IP PDP Types, IPv4 and IPv6.  Two PDP contexts are needed to
       get dual stack connectivity.

   2.  For 2G/3G access to GPRS core (SGSN/GGSN) from Release-9 there
       are three IP PDP Types, IPv4, IPv6 and IPv4v6.  Minimum one PDP
       context is needed to get dual stack connectivity.

   3.  For 2G/3G access to EPC core (PDN-GW via S4 Release-8 SGSN) from
       Release-8 there are three IP PDP Types, IPv4, IPv6 and IPv4v6
       which gets mapped to PDN Connection type.  Minimum one PDP
       Context is needed to get dual stack connectivity.

   4.  For LTE (E-UTRAN) access to EPC core from Release-8 there are
       three IP PDN Types, IPv4, IPv6 and IPv4v6.  Minimum one PDN
       Connection is needed to get dual stack connectivity.

6.3.  PDN Connection Establishment Process

   The PDN connection establishment process is specified in detail in
   3GPP specifications.  Figure 8 illustrates the high level process and
   signaling involved in the establishment of a PDN connection.












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   UE         eNb/        MME         SGW       PDN-GW       HSS/
   |           BS          |           |           |         AAA
   |           |           |           |           |           |
   |---------->|(1)        |           |           |           |
   |           |---------->|(1)        |           |           |
   |           |           |           |           |           |
   |/---------------------------------------------------------\|
   |             Authentication and Authorization              |(2)
   |\---------------------------------------------------------/|
   |           |           |           |           |           |
   |           |           |---------->|(3)        |           |
   |           |           |           |---------->|(3)        |
   |           |           |           |           |           |
   |           |           |           |<----------|(4)        |
   |           |           |<----------|(4)        |           |
   |           |<----------|(5)        |           |           |
   |/---------\|           |           |           |           |
   | RB setup  |(6)        |           |           |           |
   |\---------/|           |           |           |           |
   |           |---------->|(7)        |           |           |
   |---------->|(8)        |           |           |           |
   |           |---------->|(9)        |           |           |
   |           |           |           |           |           |
   |============= UL Data =============>==========>|(10)       |
   |           |           |           |           |           |
   |           |           |---------->|(11)       |           |
   |           |           |           |           |           |
   |           |           |<----------|(12)       |           |
   |           |           |           |           |           |
   |<============ DL Data =============<===========|(13)       |
   |           |           |           |           |           |

     Figure 8: Simplified PDN connection setup procedure in Release-8

   1.   The UE (i.e the MS) requires a data connection and hence decides
        to establish a PDN connection with a PDN-GW.  The UE sends an
        "Attach Request" (layer-2) to the BS.  The BS forwards this
        attach request to the MME.

   2.   Authentication of the UE with the AAA server/HSS follows.  If
        the UE is authorized for establishing a data connection, the
        following steps continue

   3.   The MME sends a "Create Session Request" message to the
        Serving-GW.  The SGW forwards the create session request to the
        PDN-GW.  The SGW knows the address of the PDN-GW to forward the
        create session request to as a result of this information having
        been obtained by the MME during the authentication/authorization



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        phase.

        The UE IPv4 address and/or IPv6 prefix get assigned during this
        step.  If a subscribed IPv4 address and/or IPv6 prefix is
        statically allocated for the UE for this APN, then the MME
        already passes the address information to the SGW and eventually
        to the PDN-GW in the "Create Session Request" message.
        Otherwise, the PDN-GW manages the address assignment to the UE
        (there is another variation to this where IPv4 address
        allocation is delayed until the UE initiates a DHCPv4 exchange
        but this is not discussed here).

   4.   The PDN-GW creates a PDN connection for the UE and sends "Create
        Session Response" message to the SGW from which the session
        request message was received from.  The SGW forwards the
        response to the corresponding MME which originated the request.

   5.   The MME sends the "Attach Accept/Initial Context Setup request"
        message to the eNodeB/BS.

   6.   The radio bearer between the UE and the eNb is reconfigured
        based on the parameters received from the MME

   7.   The eNb sends "Initial Context Response" message to the MME.

   8.   The UE sends a "Direct Transfer" message to the eNodeB which
        includes the Attach complete signal.

   9.   The eNodeB forwards the Attach complete message to the MME.

   10.  The UE can now start sending uplink packets to the PDN GW.

   11.  The MME sends a "Modify Bearer Request" message to the SGW.

   12.  The SGW responds with a "Modify Bearer Response" message.  At
        this time the downlink connection is also ready

   13.  The UE can now start receiving downlink packets

   The type of PDN connection established between the UE and the PDN-GW
   can be any of the types described in the previous section.  The DS
   PDN connection, i.e the one which supports both IPv4 and IPv6 packets
   is the default one that will be established if no specific PDN
   connection type is specified by the UE in Release-8 networks.







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6.4.  Mobility of 3GPP IPv4v6 Type of Bearers

   3GPP discussed at length various approaches to support mobility
   between Release-8 and pre-Release-8 networks for the new dual-stack
   type of bearers.

   The chosen approach for mobility is as follows, in short: if a mobile
   is known to be at risk for doing handovers between Release-8 and pre-
   Release-8 networks, only single stack bearers are used.  Essentially
   meaning:

   1.  If a network knows a mobile may do handovers between Release-8
       and pre-Release-8 networks (segment), network will only provide
       single stack bearers, even if the mobile host requests dual-stack
       bearers.  This can happen e.g. if an operator is using pre-
       Release-8 SGSNs in some parts of the network.  The single stack
       bearers of Release-8 are easy to map one-to-one to pre-Release-8
       bearers.

   2.  If a network knows a mobile will not be able to do handover to
       pre-Release-8 network (segment), it will provide mobile with
       dual-stack bearers on request.  This can happen e.g. if an
       operator has upgraded their SGSNs to support dual-stack bearers,
       or if an operator is running LTE-only network.

   The operators should upgrade their, and also if possible roaming
   partners', networks to Release-8 level in order to support new dual-
   stack type of bearers.  A Release-8 mobile device always requests for
   a dual-stack bearer, but accepts what is assigned by the network.


7.  Dual-Stack Approach to IPv6 Transition in 3GPP Networks

   3GPP networks can natively transport IPv4 and IPv6 packets between
   the mobile station/UE and the gateway (GGSN or PDN-GW) as a result of

      establishing either a dual-stack PDP context or

      parallel IPv4 and IPv6 PDP contexts.

   Current deployments of 3GPP networks primarily support IPv4 only.
   These networks can be upgraded to also support IPv6 PDP contexts.  By
   doing so devices and applications that are IPv6 capable can start
   utilizing the IPv6 connectivity.  This will also ensure that legacy
   devices and applications continue to work with no impact.  As newer
   devices start using IPv6 connectivity, the number of IPv4 addresses
   in use is expected to slowly decrease, providing operators with a
   smooth transition to IPv6 With a dual-stack approach, there is always



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   the potential to fallback to IPv4.  A device which may be roaming in
   a network wherein IPv6 is not supported by the visited network would
   fall back to using IPv4 PDP contexts and hence the end user does not
   see an interruption to the services.

   As the networks evolve to support Release-8 EPS architecture and the
   dual-stack PDP contexts, newer devices will be able to leverage such
   capability and have a single bearer which supports both IPv4 and
   IPv6.  Since IPv4 and IPv6 packets are carried as payload within GTP
   between the MS and the gateway (GGSN/PDN-GW) the transport network
   capability in terms of whether it supports IPv4 or IPv6 on the
   interfaces between the eNodeB and SGW or, SGW and PDN-GW is
   immaterial.

   The dual-stack approach enables a systematic migration path to IPv6.
   From an operational standpoint operators are concerned about ensuring
   that there is no disruption to the connectivity that subscribers rely
   on.  This can be achieved by upgrading the network to support IPv6
   while continuing to maintain IPv4 legacy.  Dual-stack capability in
   the network and devices for the foreseeable future at least is a
   pragmatic solution.


8.  Deployment issues

8.1.  Overlapping IPv4 Addresses

   Given the shortage of globally routable public IPv4 addresses,
   operators tend to assign private IPv4 addresses [RFC1918] to hosts
   when they establish an IPv4 only PDP context or an IPv4v6 type PDN
   context.  About 16 million hosts can be assigned a private IPv4
   address that is unique within a domain.  However, in case of many
   operators the number of subscribers is greater than 16 million.  The
   issue can be dealt with by assigning overlapping RFC 1918 IPv4
   addresses to hosts.  As a result the IPv4 address assigned to a host
   within the context of a single operator realm would no longer be
   unique.  This has the obvious and know issues of NATed IP connection
   in the Internet.  Direct host to host connectivity becomes
   complicated, unless the hosts are within the same private address
   range pool and/or anchored to the same gateway, referrals using IP
   addresses will have issues and so forth.  However, these are generic
   issues and not only a concern of the EPS.  In general this is not
   seen as a major issue in the EPS for the following reasons:

   1.  Very large network deployments are partitioned, for example,
       based on a geographical areas.  This partitioning allows
       overlapping IPv4 addresses ranges to be assigned to hosts that
       are in different areas.  Each area has its own pool of gateways



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       that are dedicated for a certain overlapping IPv4 address range
       (referred here later as a zone).  Standard NAT44 functionality
       enables the communication between hosts that are assigned the
       same IPv4 address but belong to different zones, yet are part of
       the same operator domain.

   2.  A mobile host/device attaches to a gateway as part of the attach
       process.  The number of hosts that a gateway supports is in the
       order of 1 to 10 million.  Hence all the hosts assigned to a
       single gateway can be assigned private IPv4 addresses.  Operators
       with large subscriber bases have multiple gateways and hence the
       same [RFC1918] IPv4 address space can be reused across gateways.
       The IPv4 address assigned to a host is unique within the scope of
       a single gateway.

   3.  The IPv4 address assigned to a host could also be made irrelevant
       from a routing perspective at least by the use of protocol
       solutions such as GI-DSLite
       [I-D.ietf-softwire-gateway-init-ds-lite].  This requires a Large
       Scale NAT (LSN) entity that is detached from the gateway (GGSN or
       PDN-GW).  Multiple gateways in an operator domain would attach to
       a LSN in such an approach and the hosts across these gateways can
       be assigned overlapping IPv4 addresses.

   4.  New services requiring direct connectivity between hosts should
       be build on IPv6.  Possible existing IPv4-only services and
       applications requiring direct connectivity can be ported to IPv6.

8.2.  IPv6 for transport

   The various reference points of the 3GPP architecture such as S1-U,
   S5 and S8 are based on either GTP or PMIPv6.  The underlying
   transport for these reference points can be IPv4 or IPv6.  GTP has
   been able to operate over IPv6 transport (optionally) since R99 and
   PMIPv6 has supported IPv6 transport starting from its introduction in
   Release-8.  The user plane traffic between the mobile host and the
   gateway can use either IPv4 or IPv6.  These packets are essentially
   treated as payload by GTP/PMIPv6 and transported accordingly with no
   real attention paid to the information (at least from a routing
   perspective) contained in the IPv4 or IPv6 headers.  The transport
   links between the eNodeB and the SGW, and the link between the SGW
   and PDN-GW can be migrated to IPv6 without any direct implications to
   the architecture.

   Currently, the inter-operator (for 3GPP technology) roaming networks
   are all IPv4 only (see Inter-PLMN Backbone Guidelines [GSMA.IR.34]).
   Eventually these roaming networks will also get migrated to IPv6, if
   there is a business reason for that.  The migration period can be



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   prolonged considerably because the 3GPP protocols always tunnel user
   plane traffic in the core network and as described earlier the
   transport network IP version is not in any way tied to user plane IP
   version.  Furthermore, the design of the inter-operator roaming
   networks is such that the user plane and transport network IP
   addressing is completely separated from each other.  The inter-
   operator roaming network itself is also completely separated from the
   Internet.  Only those core network nodes that must be connected to
   the inter-operator roaming networks are actually visible there, and
   be able to send and receive (tunneled) traffic within the inter-
   operator roaming networks.  Obviously, in order the roaming to work
   properly, the operators have to agree on supported protocol versions
   so that the visited network does not, for example, unnecessarily drop
   user plane IPv6 traffic.

8.3.  Operational Aspects of Running Dual-Stack Networks

   Operating dual-stack networks does imply cost and complexity to a
   certain extent.  However these factors are mitigated by the assurance
   that legacy devices and services are unaffected and there is always a
   fallback to IPv4 in case of issues with the IPv6 deployment or
   network elements.  The model also enables operators to develop
   operational experience and expertise in an incremental manner.

   Running dual-stack networks requires the management of multiple IP
   address spaces.  Tracking of hosts needs to be expanded since it can
   be identified by either an IPv4 address or IPv6 prefix.  Network
   elements will also need to be dual-stack capable in order to support
   the dual-stack deployment model.

   Deployment and migration cases described in Section 6.1 for providing
   dual-stack like capability may mean doubled resource usage in
   operator's network.  Also handovers between networks with different
   capabilities in terms of networks being dual-stack like service
   capable or not, may turn out hard to comprehend for users and for
   application/services to cope with.  These facts may add other than
   just technical concerns for operators when planning to roll out dual-
   stack service offerings.


9.  IANA Considerations

   This document has no requests to IANA.


10.  Security Considerations

   This document does not introduce any security related concerns.



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11.  Summary and Conclusion

   The 3GPP network architecture and specifications enable the
   establishment of IPv4 and IPv6 connections through the use of
   appropriate PDP context types.  The current generation of deployed
   networks can support dual-stack connectivity if the packet core
   network elements such as the SGSN and GGSN have the capability.  With
   Release-8, 3GPP has specified a more optimal PDP context type which
   enables the transport of IPv4 and IPv6 packets within a single PDP
   context between the mobile station and the gateway.

   The authors believe that transitioning to IPv6 in 3GPP networks can
   be achieved without disruption to legacy devices, networks and
   services only by taking a dual-stack approach to deployment.  As
   devices and applications are upgraded to support IPv6 they can start
   leveraging the IPv6 connectivity provided by the networks while
   maintaining the fallback to IPv4 capability.  Enabling IPv6
   connectivity in the 3GPP networks by itself will provide some degree
   of relief to the IPv4 address space as many of the applications and
   services can start to work over IPv6 right away.  However without
   comprehensive testing of different applications and solutions that
   exist today and are widely used, for their ability to operate over
   IPv6 PDN connections, an IPv6 only access would cause disruptions.
   Hence we recommend adopting the dual-stack approach to IPv6
   transition in 3GPP networks.


12.  Acknowledgements

   The authors thank Shabnam Sultana, Sri Gundavelli, Hui Deng, and
   Zhenqiang Li for their reviews and comments on this document.


13.  Informative References

   [3GPP.23.060]
              3GPP, "General Packet Radio Service (GPRS); Service
              description; Stage 2", 3GPP TS 23.060 8.8.0, March 2010.

   [3GPP.23.401]
              3GPP, "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", 3GPP TS 23.401 8.9.0, March 2010.

   [3GPP.23.975]
              3GPP, "IPv6 migration guidelines", 3GPP TR 23.975 1.0.0,
              March 2010.




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   [3GPP.29.060]
              3GPP, "General Packet Radio Service (GPRS); GPRS
              Tunnelling Protocol (GTP) across the Gn and Gp interface",
              3GPP TS 29.060 8.11.0, April 2010.

   [3GPP.29.061]
              3GPP, "Interworking between the Public Land Mobile Network
              (PLMN) supporting packet based services and Packet Data
              Networks (PDN)", 3GPP TS 29.061 8.5.0, April 2010.

   [GSMA.IR.34]
              GSMA, "Inter-PLMN Backbone Guidelines", GSMA
              PRD IR.34.4.9, March 2010.

   [I-D.ietf-softwire-gateway-init-ds-lite]
              Brockners, F., Gundavelli, S., Speicher, S., and D. Ward,
              "Gateway Initiated Dual-Stack Lite Deployment",
              draft-ietf-softwire-gateway-init-ds-lite-00 (work in
              progress), May 2010.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

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

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.

   [RFC4389]  Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
              Proxies (ND Proxy)", RFC 4389, April 2006.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007.




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   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.


Appendix A.  Transition scenarios discussed in 3GPP

   Several scenarios of IPv4 and IPv6 co-existence and transition have
   been discussed and documented in 3GPP TR 23.975 [3GPP.23.975].

   In scenario 1, a dual-stack connectivity scenario, the operator runs
   the user plane in dual stack mode, i.e., the UEs are assigned both an
   IPv6 prefix and an IPv4 address in order to allow UEs to utilise both
   IPv4 and IPv6 capable applications.

   It is assumed that the proportion of IPv6 capable applications will
   start to increase as soon as UEs and networks starts to become dual-
   stack capable.  As popular services start to support IPv6, a part of
   IPv4 traffic will gradually be offloaded into the IPv6 domain.

   During transition phase, the depletion of public IPv4 addresses will
   be an issue to be solved in some operators' networks.  The shortage
   of public addresses will be aggravated by always-on packet data
   connectivity, which is expected to prevail in newer network
   deployments.

   In scenario 1, the shortage of public IPv4 addresses is alleviated by
   assigning IPv4 addresses from one of the private address ranges as
   specified in [RFC1918].  To enable global connectivity, network
   address translation (NAT) is performed on the (S)Gi interface for
   IPv4 packets originated from or destined to the UEs.

   Scenario 2 is a similar dual-stack connectivity scenario as Scenario
   1, but includes a further challenge where private IPv4 addresses are
   used by more than 16 million active UEs (i.e., have an active PDP
   context/EPS bearer) in the same network at the same time.  If unique
   private IPv4 addresses are not available for all UEs, the operator
   may need to consider assigning the same IPv4 address to multiple UEs.
   The usage of shared IPv4 addresses in parallel to an IPv6 prefix is
   also described in scenario 4.

   In addition to the more general dual-stack connectivity scenarios,
   specific scenarios related to e.g.  M2M terminals have been
   considered in Scenario 3.  The operator may choose to assign only
   IPv6 prefixes to this new group of mobile devices.  These UEs with
   IPv6-only connectivity will be running applications using IPv6, but
   they may need to access both IPv4- or IPv6-enabled services.





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Authors' Addresses

   Jouni Korhonen (editor)
   Nokia Siemens Networks
   Linnoitustie 6
   FI-02600 Espoo
   FINLAND

   Email: jouni.nospam@gmail.com


   Jonne Soininen
   Nokia Siemens Networks
   Linnoitustie 6
   FI-02600 Espoo
   FINLAND

   Email: jonne.soininen@nsn.com


   Basavaraj Patil
   Nokia
   6021 Connection drive
   Irving, TX  75019
   USA

   Email: basavaraj.patil@nokia.com


   Teemu Savolainen
   Nokia
   Hermiankatu 12 D
   FI-33720 Tampere
   FINLAND

   Email: teemu.savolainen@nokia.com


   Gabor Bajko
   Nokia
   323 Fairchild drive 6
   Mountain view, CA  94043
   USA

   Email: gabor.bajko@nokia.com






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   Kaisu Iisakkila
   Nokia
   Itamerenkatu 11-13
   FI-00180 Helsinki
   FINLAND

   Email: kaisu.iisakkila@nokia.com












































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