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Versions: 00                                                            
Internet Draft                                             J. Soininen
Document: draft-soininen-ngtrans-3gpp-cases-00.txt         J. Wiljakka
Expires: October 2002                                            Nokia
                                                              A.Durand
                                                      Sun Microsystems
                                                            P. Francis
                                                        Tahoe Networks
                                                            April 2002

                  Transition Scenarios for 3GPP Networks

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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.

Abstract

   This document describes different scenarios in Third Generation
   Partnership Project (3GPP) defined packet network, i.e. General
   Packet Radio Service (GPRS) that would need IP version 6 and IP
   version 4 transition. The focus of this document is on the scenarios
   where the User Equipment (UE) connects to nodes in other networks,
   e.g. in the Internet. GPRS network internal transition scenarios,
   i.e. between different GPRS elements in the network, are out of scope
   of this document.

   The purpose of the document is to list the scenarios for further
   discussion and study.

Table of Contents

   1. Introduction...................................................2
   2. Scope of the document..........................................2
   3. Transition scenarios...........................................2


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                Transition Scenarios for 3GPP Networks      April 2002


      3.1 GPRS Scenarios.............................................3
      3.2 Transition scenarios with IMS..............................4
   4. Security Considerations........................................5
   Acknowledgements..................................................5
   References........................................................5
   Author's Addresses................................................5

Copyright

   (C) The Internet Society (2002).  All Rights Reserved.

1. Introduction

   This document will describe the transition scenarios in 3GPP packet
   data networks that might come up in the deployment phase of IPv6.
   The main purpose of this document is to identify, and document those
   scenarios for further discussion, and for study in the NGTRANS
   working group.

   This document does give neither an overview, nor an explanation of
   3GPP or the 3GPP packet data network - the GPRS. A good overview of
   the 3GPP specified GPRS can be found from [1]. The GPRS architecture
   specification is defined in [2].

2. Scope of the document

   The scope of this document is to describe the possible transition
   scenarios in the 3GPP defined GPRS network where a UE connects to, or
   is contacted from the Internet, or another UE. The document describes
   scenarios with and without the usage of the SIP based IP Multimedia
   Core Network Subsystem (IMS).

   The scope of this document does not include scenarios inside the GPRS
   network, i.e. on the different interfaces of the GPRS network. In
   addition, this document does not identify solutions - just possible
   scenarios.

   These scenarios may, or may not be found feasible, or even likely in
   further study.

3. Transition scenarios

   This section is divided into two main parts - GPRS scenarios, and
   scenarios with the IP Multimedia Subsystem (IMS). The first part -
   GPRS scenarios - concentrate on scenarios with a User Equipment (UE)
   connecting to services in the Internet, e.g. mail, web. The second
   part - IMS scenarios - then describes how an IMS capable UE can
   connect to other SIP capable nodes in the Internet using the IMS
   services.


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                Transition Scenarios for 3GPP Networks      April 2002



3.1 GPRS Scenarios

   This section describes the scenarios that might occur when a GPRS UE
   contacts services, or nodes outside the GPRS network, e.g. web-server
   in the Internet.

   Transition scenarios of the GPRS internal interfaces are outside of
   the scope of this document.

   The following scenarios are described here. In all of the scenarios,
   the UE is part of a network where there is at least one router of the
   same IP version, i.e. GGSN, and it is connecting to a node in a
   different network.

      1) Dual Stack UE connecting to IPv4 and IPv6 nodes
      2) IPv6 UE connecting to an IPv6 node through an IPv4 network
      3) IPv4 UE connecting to an IPv4 node through an IPv6 network
      4) IPv6 UE connecting to an IPv4 node
      5) IPv4 UE connecting to an IPv6 node


   1) Dual Stack UE connecting to IPv4 and IPv6 nodes

   The GPRS system has been designed in a manner that there is the
   possibility to have simultaneous IPv4, and IPv6 PDP Contexts open.
   Thus, in cases where the UE is dual stack capable, and in the network
   there is a GGSN (or separate GGSNs) that supports both connection to
   IPv4, and IPv6 networks, it is possible to connect to both at the
   same time.

   However, the IPv4 addresses might be a scarce resource for the mobile
   operator or an ISP. In that case, it might not be possible for the UE
   to have a globally unique IPv4 address allocated all the time. Hence,
   either activating the IPv4 PDP Context only when needed, or having an
   IPv4 address from a private address space.


   2) IPv6 UE connecting to an IPv6 node through an IPv4 network

   Especially in the first stages of IPv6 deployment, there are cases
   where an IPv6 node would need to connect to the IPv6 Internet through
   a network that is IPv4. For instance this can be seen in current
   fixed networks, where the access is provided in IPv4 only, but there
   is an IPv6 network deeper in the Internet.

   In this case, in the GPRS system, the UE would be IPv6 capable, and
   the GPRS network would be IPv6 capable of providing an IPv6 capable



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                Transition Scenarios for 3GPP Networks      April 2002


   GGSN in the network. However, the operator only has an IPv4 network
   as such.


   3) IPv4 UE connecting to an IPv4 node through an IPv6 network

   Further in the future, there are cases where the legacy UEs are still
   IPv4 only, capable of connecting to the legacy IPv4 Internet.
   However, the GPRS operator network has already been upgraded to IPv6.

   In this case, the operator would still provide the IPv4 capable GGSN,
   and a connection through the IPv6 network to the IPv4 Internet.


   4) IPv6 UE connecting to an IPv4 node

   In this scenario an IPv6 UE connects to an IPv4 node in the IPv4
   Internet. As an example, an IPv6 UE connects to an IPv4 web server in
   the legacy Internet.


   5) IPv4 UE connecting to an IPv6 node

   This is similar to the case above, but to the opposite direction.
   Here an IPv4 UE connects to an IPv6 node in the IPv6 Internet. As an
   example, a legacy IPv4 UE is connected to an IPv6 server in the IPv6
   Internet.


3.2 Transition scenarios with IMS

   IP Multimedia Core Network Subsystem (IMS) is a SIP based multimedia
   service architecture. It is specified in the Release 5 of 3GPP. It
   comprises a set of SIP proxies, servers, and registrars. In addition,
   there are Media Gateways (MGWs) that offer connections to non-IP
   networks such as the Public Switched Telephony Network (PSTN).

   IMS is exclusively IPv6. Hence, all the traffic for the IMS is IPv6,
   even if the UE would be dual stack capable. More information on IMS
   can be found in [3].

   As IMS is exclusively IPv6, the number of possible transition
   scenarios is reduced dramatically. In the following, the possible
   transition scenarios are listed.

      1) UE connecting to a node in an IPv4 network through IMS
      2) Two IPv6 IMS connected via an IPv4




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   1) UE connecting to a node in an IPv4 network through IMS

   This scenario occurs when an IMS UE (IPv6) connects to a node in the
   IPv4 Internet through the IMS, or vice versa. This happens when the
   other node is a part of a different system than 3GPP, e.g. a fixed
   PC, with only IPv4 capabilities.


   2) Two IPv6 IMS connected via an IPv4

   At the early stages of IMS deployment, there may be cases where two
   IMS islands are separated on IPv4 network such as the legacy
   Internet. Here both the UEs are IPv6 and the IMSes where the UEs are
   IPv6. However, the IPv6 islands are not native IPv6 connected.


4. Security Considerations

   This document does not generate any additional security
   considerations.

Acknowledgements

   The authors would like to thank Basavaraj Patil, Tuomo Sipila, and
   Jens Staack for good input, and comments that helped writing this
   document.

References
    [1] Wasserman, M. et al, "Recommendations for IPv6 in 3GPP
    Standards", January 2002, draft-ietf-ipv6-3gpp-recommend-00.txt.

    [2] 3GPP TS 23.060 v 3.11.0, "General Packet Radio Service (GPRS);
    Service description; Stage 2(Release 1999)", March 2002.

    [3] 3GPP TS 23.228 v 5.3.0, " IP Multimedia Subsystem (IMS); Stage
    2(Release 5)", January 2002.


 Author's Addresses

    Jonne Soininen
    Nokia
    313 Fair Child Dr.           Phone:  +1-650-864-6794
    Mountain View, CA, USA       Email:  jonne.Soininen@nokia.com

    Juha Wiljakka
    Nokia
    Visiokatu 3                  Phone:  +358 7180 47562
    FIN-33720 TAMPERE, Finland   Email:  juha.wiljakka@nokia.com


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                 Transition Scenarios for 3GPP Networks      April 2002



    Alain Durand
    Sun Microsystems
    901 San Antonio rd UMPK17-202
    Palo Alto, CA, USA           Email:  Alain.Durand@sun.com

    Paul Francis
    Tahoe Networks
    3052 Orchard Dr.             Phone:  +1-408-944-8632
    San Jose CA, USA             Email:  francis@tahoenetworks.com









































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