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                  IPv6 Operations Working Group
                  Internet Draft                                               J.P. Yoo
                  Document: draft-ietf-v6ops-3gpp-ipv6use-00.txt              K. C. Kim
                                                                      Konkuk University
               
                                                                              J.P. Hong
                                                                                   HUFS
               
                                                                              K. J. Lee
                                                                         Hyoung-Jun Kim
                                                                                   ETRI
               
                  Expires: May 2002                                       October 2003
               
               
                         IPv6 in 3GPP networks satisfying IETF's recommendations
               
               
               Status of this Memo
               
                  This document is an Internet-Draft and is in full conformance with
                  all provisions of Section 10 of RFC2026 [i].
               
                  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."
               
               
               Abstract
               
                  3GPP PS (Packet Switched) domain Standard states the usage of IPv6 as
                  its network protocol to compensate the shortage of Internet address
                  and to use the enhanced network protocol functions. In case of the
                  current IPv6 usage in 3GPP packet domain standards, they have unique
                  IPv6 address allocation scheme which is somewhat different from the
                  one of IETF due to its 3G equipments and packet network elements.
                  Meanwhile, IETF presents " recommendations to 3GPP networks (RFC3314
                  [2])" to satisfy compatibility between IETF IPv6 and IPv6 of 3GPP
                  networks and to lift up the IPv6 capabilities. In this situation,
                  this document provides a new IPv6 address allocation scheme in 3GPP
                  networks satisfying IETF' recommendations. Provided scheme keeps
                  rules of recommendations of IETF standards and guarantees backward
                  compatibility with the legacy 3GPP IPv6 autoconfiguration.
               
               
               Conventions used in this document
               
               
               
               
               
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                         IPv6 in 3GPP networks satisfying IETF's recommendations
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                  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
                  "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
                  document are to be interpreted as described in RFC-2119 [ii].
               
               
               Table of Contents
               
                  1. Introduction...................................................2
                     1.1 Terminology................................................2
                     1.2 3GPP network architecture..................................3
                  2. IPv6 in 3GPP and IETF Recommendations..........................3
                     2.1 3GPP IPv6 Address Allocation Scheme........................3
                     2.2 IETF Recommendation for 3GPP IPv6 Address Allocation.......5
                  3. IPv6 in 3GPP networks satisfying IETFÆs Recommendations........5
                     3.1 Address allocation procedures..............................5
                     3.2 Network elements actions...................................7
                     3.3 Autoconfiguration steps for Backward compatibility.........8
                  4. Security Considerations.......................................10
                  5. References....................................................10
                  Author's Addresses...............................................10
               
               
               1. Introduction
               
                  Currently, 3GPP networks optionally use IPv6 and IETF IPv6 working
                  group helps 3GPP networks for the efficient protocol usage. In
                  addition, IPv6 working group gives advices to 3GPP networks for
                  protocol compatibility. As a result, IETF RFC standard (RFC 3314) was
                  provided to recommend the correct usage of IPv6 to 3GPP networks. In
                  this situation, this draft document provides an IPv6 usage scheme for
                  3GPP networks. This document has the following contents.
               
                     1. Introduction to this documents and terminology.
                     2. 3GPP IPv6 address allocation scheme and recommendations of
                         IETF to 3GPP networks.
                     3. IPv6 usage in IPv6 in 3GPP networks satisfying IETF's
                         recommendations.
               
               
               1.1 Terminology
               
               
                     GGSN         Gateway GPRS Support Node.  A router between the GPRS
                                  network and an external network (i.e., the Internet).
               
                     GPRS         General Packet Radio Services
               
                     GTP-U        General Tunneling Protocol - User Plane
               
               
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                     GSN          GPRS support Node (GGSN, SGSN)
               
                     IMSI         International Mobile Subscriber Identity. A unique
                                  15-digit number which designates the subscriber. This
                                  number is used for provisioning in network elements.
               
                     MT           Mobile Termination.  For example, a mobile phone
                                  handset.
               
                     MS           Mobile Station. (MT + TE)
               
                     PDP          Packet Data Protocol
               
                     PDP Context  A PDP connection between the UE and the GGSN.
               
                     PS           Packet Switched
               
                     SGSN         Serving GPRS Support Node
               
                     TE           Terminal Equipment.  For example, a laptop attached
                                  through a 3GPP handset.
               
                     UE           User Equipment (TE + MT + USIM).  An example would be
                                  a mobile handset with a USIM card inserted and a
                                  laptop attached.
               
                     UMTS         Universal Mobile Telecommunications System
               
                     USIM         Universal Subscriber Identity Module.  Typically, a
                                  card that is inserted into a mobile phone handset.
               
                     UTRAN        Universal Terrestrial Radio Access Network
               
               
               1.2 3GPP network architecture
               
                  We recommend to refer to IETF documents and 3GPP documents(RFC3314,
                  TS 23.060[3])in order to understand 3GPP basic network architecture
               
               
               2. IPv6 in 3GPP and IETF Recommendations
               
               2.1 3GPP IPv6 Address Allocation Scheme
               
                  3GPP address allocation steps are composed of two phases. In the
                  first phase, MS gets its interface identification from GGSN. That is
                  why 3GPP equipments can't make an unique identification. In this
               
               
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                  phase, 3GPP PDP context setup procedure is used. In the second phase,
                  MS gets IPv6 network prefix that is required for global address from
                  GGSN. In this phase, RS (Router Solicitation) and RA (Router
                  advertisement) messages are required.
               
                  3GPP address autoconfiguration has the following steps:
               
                      1. The Activate PDP Context message is sent to the SGSN (PDP
                          Type=IPv6, PDP Address = 0, etc.).
               
                      2. The SGSN sends a Create PDP Context message to the GGSN with
                          the above parameters.
               
                      3. GGSN chooses an interface identifier for the PDP Context and
                         creates the link-local address.  It answers the SGSN with a
                         Create PDP Context response (PDP Address = link-local
                          Address).
               
                      4. SGSN sends an Activate PDP Context accept message to
                          the UE (PDP Address = link-local address).
               
                      5. UE keeps the link-local address, and extracts the
                         interface identifier for later use. UE may send a Router
                          Solicitation message to the GGSN (first hop router).
               
                      6. After PDP Context Activation, GGSN sends a Router
                         Advertisement to the UE. The UE should be configured not to
                         send a Neighbor Solicitation message.  However, if one is sent,
                         the GGSN will silently discard it. The GGSN updates the SGSN
                         with the whole IPv6 address.
               
                       MS              BSS/UTRAN           SGSN              GGSN
               
                       |                  |                 |                 |
                       |1. Active PDP Context Request       |                 |
                       |----------------------------------->|                 |
                       |                  |                 |                 |
                       |                  |              2. Create PDP Context Request
                       |                  |                 |---------------->|
                       |                  |                 |                 |
                       |                  |              3. Create PDP Context Response
                       |                  |                 |<----------------|
                       |                  |                 |                 |
                       |4. Active PDP Context Accept        |                 |
                       |<-----------------------------------|                 |
                       |                  |                 |                 |
                       |5. Router Solicitation              |                 |
                       |- - - - - - - - - - - - - - - - - - - - - - - - - - ->|
               
               
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                       |                  |                 |                 |
                       |6. Router Advertisement             |                 |
                       |<-----------------------------------------------------|
                       |                  |                 |                 |
                           Figure 1:  3GPP IPv6 Address Autoconfiguration steps
               
               
               2.2 IETF Recommendation for 3GPP IPv6 Address Allocation
               
                  IPv6 Working Group recommends following three changes regarding the
                  use of IPv6 within 3GPP networks for a productive cooperation.
               
               
                        1. Specify that multiple prefixes may be assigned to each
                           primary PDP context,
               
                        2. Require that a given prefix must not be assigned to more
                           than one primary PDP context, and
               
                        3. Allow 3GPP nodes to use multiple identifiers within those
                           prefixes, including randomly generated identifiers.
               
                  For further understanding about IETF recommendation, refer to RFC3314.
               
               
               3. IPv6 in 3GPP networks satisfying IETF' Recommendations.
               
               3.1 Address allocation procedures
               
                  This section describes IPv6 autoconfiguration procedure satisfying
                  IETF's recommendation. This procedure is made of two phases. In the
                  first phase, MS gets multiple prefix from GGSN using RS/RA message by
                  IMSI based interface identification. In the second phase, MS
                  associates the selected prefix and interface identification created
                  by itself and register IPv6 address to GSNs using PDP context
                  activation.
               
                      MS              BSS/UTRAN           SGSN              GGSN
               
                       |                  |                 |                 |
                       |1. Router Solicitation              |                 |
                       |----------------------------------------------------->|
                       |                  |                 |                 |
                       |2. Router Advertisement             |                 |
                       |<-----------------------------------------------------|
                       |                  |                 |                 |
                       |3. Active PDP Context Request       |                 |
                       |----------------------------------->|                 |
               
               
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                       |                  |                 |                 |
                       |                  |              4. Create PDP Context Request
                       |                  |                 |---------------->|
                       |                  |                 |                 |
                       |                  |              5. Create PDP Context Response
                       |                  |                 |<----------------|
                       |                  |                 |                 |
                       |6. Active PDP Context Accept        |                 |
                       |<-----------------------------------|                 |
                       |                  |                 |                 |
                       |(7. Router Solicitation : Backward Compatibility)     |
                       |----------------------------------------------------->|
                       |                  |                 |                 |
                       |(8. Router Advertisement : Backward Compatibility)    |
                       |<-----------------------------------------------------|
               
                    Figure 2:  3GPP Address Autoconfiguration steps satisfying IETFÆs
                                       Recommendations to the 3GPP
               
                      1. RA message is sent to GGSN.
                         At this time, IMSI number is used for lower 64bit portion
                         (Interface Identification) in IPv6 address to identify each RA
                         message. Note that this IMSI based interface identification is
                         not the lower potion of IPv6 source address used in user
                         traffic connection. Since IMSI number is an unique 15-digit
                         number, it can be converted into about 50-bit length binary
                         number. This length is very close to the length of 48bit MAC
                         address . So, It is natural to map IMSI number into lower
                         64bit portion in IPv6 address field. In this case, we cannot
                         omit RA message different from 3GPP standard shown in section
                         2.1. As we can see from figure 2, the procedure starts with RA
                         message from MS to satisfy the IETF's recommendation different
                         from 3GPP legacy procedure.
               
                      2. After receiving RS message from MS, GGSN sends a RA message to
                         MS.
                         In this step, GGSN selects multiple /64 prefix for MS and
                         includes these multiple prefix in RA message in a precedence
                         sequence. Undoubtedly, the prefix must not be assigned to
                         other MS. The GSSN can identify the MS uniquely by IMSI based
                         interface identification.
               
                      3. The Activate PDP Context message is sent to the SGSN (PDP
                          Type=IPv6, PDP Address = IPv6 address selected by MS, etc.).
                         In this case, PDP address means full global IPv6 address and
                         is made of the following combination.
               
               
               
               
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                         PDP Address = prefix selected by MS in RA message + interface
                         identification selected by MS from TE or MT itself.
               
                                                  or
               
                         PDP Address can be 0 for backward compatibility
               
                      4. SGSN sends a Create PDP Context message to the GGSN with
                         the above parameters(parameters used in step 3).
               
                      5. GGSN updates context from MS. Especially, GGSN only
                         updates the prefix information extracted from PDP address
                         information not the whole IPv6 address. It is possible because
                         the GGSN has sent a multiple prefix not assigned to other MS.
                         It also means that each MS can be identified by just only
                         prefix not the whole IPv6 address. After that, the GGSN sends
                         Create PDP Context response to the SGSN with the parameters
                         (PDP address=prefix selected by MS + interface identification
                         ->0). If the GGSN gets PDP address with '0', the GGSN follows
                         legacy 3GPP address auto-configuration steps. Section 3.3
                         explains backward compatibility. We can avoid the ambiguity
                         between the new steps and the legacy steps by using ?Æpadding
                         in an interface identification field.
               
                      6. SGSN updates the context based on the Create PDP Context
                         response message from GGSN. SGSN extracts prefix information
                         and keeps it for routing information. After that, SGSN sends
                         an Activate PDP Context Accept to the MS with the
                         parameters(PDP address=prefix selected by MS + interface
                         identification ->0). If the SGSN checks that interface
                         identification is not 0, the SGSN follows legacy 3GPP address
                         auto-configuration steps. Refer to 3.3 for backward
                         compatibility.
               
                      7. for Backward Compatibility. Refer to section 3.3
               
                      8. for Backward Compatibility. Refer to section 3.3
               
               
               3.2  Network elements actions
               
                  MS Actions
               
                         When starts a session, MS prepares RS message with the
                         interface identification based on its IMSI number. GGSN will
                         reply MS with RA message including multiple /64 prefix. After
                         receiving a multiple /64 prefix, MS selects one /64 prefix for
                         a primary PDP context and stores the rest of prefix(s) for
               
               
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                         later use. For an  Activate PDP context, MS prepares an
                         interface identification. In order to prepare this, MS must
                         have a capability to create a randomly chosen interface
                         identification by way of MT, TE or MS itself. With the chosen
                         /64 prefix and interface identification produced by MS, MS
                         composes PDP address and sends it to GGSN.
               
                  GGSN Actions
               
                         When receiving RS from MS, GGSN prepares multiple /64 prefix
                         for MS. These selected multiple prefix(s) must not be pre-
                         assigned to other MS. Prefix sets must be always unique to MS.
                         After preparing prefix(s), GGSN replys to MS with RA message
                         including selected prefix(s). If GGSN receives PDP context
                         from MS through SGSN, it must find whether PDP context means
                         the  start of a session(legacy procedure) or the continuity of
                         a session. Those steps shown in figure 1 must go on in the
                         former case and the steps in figure 2 must be followed in the
                         later case. If GGSN finds that PDP address with /64
                         prefix(figure 2 steps), it stores only /64 prefix information
                         in its memory not the whole IPv6 address for efficiency. If
                         GGSN finds the PDP address with 0, it replys to MS with PDP
                         address including link-local address.
               
                  SGSN Actions
               
                         When receiving an Activate PDP Context message from MS, the
                         SGSN does not modify PDP type and PDP address information,
                         just relay to GGSN. If it receives a Create PDP Context
                         message from GGSN, it must find whether the interface
                         identification field is empty or not. If not empty, SGSN
                         notice that this session is for a legacy process. So, SGSN
                         just relay to MS with a Activate Context Accept message
                         without storing any information in PDP Context message. If
                         empty, SGSN notices that this session is for steps satisfying
                         IETF's recommendations. So, SGSN stores /64 prefix information
                         and replays toMS with an Activate Context Accept message.
               
               3.3 Autoconfiguration steps for Backward compatibility
               
                  This section describes a backward compatibility supporting legacy
                  3GPP MS which is compatible with the process in section 2.1
               
                      MS              BSS/UTRAN           SGSN              GGSN
               
                       |                  |                 |                 |
                       |(0. Router Solicitation : not used )|                 |
                       |----------------------------------------------------->|
               
               
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                       |                  |                 |                 |
                       |(0. Router Advertisement : not used )                 |
                       |<-----------------------------------------------------|
                       |                  |                 |                 |
                       |1. Active PDP Context Request       |                 |
                       |----------------------------------->|                 |
                       |                  |                 |                 |
                       |                  |              2. Create PDP Context Request
                       |                  |                 |---------------->|
                       |                  |                 |                 |
                       |                  |              3. Create PDP Context Response
                       |                  |                 |<----------------|
                       |                  |                 |                 |
                       |4. Active PDP Context Accept        |                 |
                       |<-----------------------------------|                 |
                       |                  |                 |                 |
                       |5. Router Solicitation              |                 |
                       |----------------------------------------------------->|
                       |                  |                 |                 |
                       |6. Router Advertisement             |                 |
                       |<-----------------------------------------------------|
               
                       Figure 3:  3GPP Address Autoconfiguration steps for backward
                                              compatibility
               
                  3GPP address autoconfiguration for backward compatibility has the
                  following steps:
               
                      0. Not used in backward compatibility steps.
               
                      1. The Activate PDP Context message is sent to SGSN (PDP
                          Type=IPv6, PDP Address = 0, etc.).
               
                      2. The SGSN sends a Create PDP Context message to GGSN with
                          the above parameters.
               
                      3. If GGSN gets PDP address with 0, GGSN chooses an interface
                         identifier for the PDP Context and creates a link-local
                         address. It answers to SGSN with a Create PDP Context response
                         (PDP Address = link-local Address). If GGSN gets a PDP address
                         with not 0, the GGSN follows step 5 in section 3.1
               
                      4. SGSN sends an Activate PDP Context accept message to
                         the MS (PDP Address = link-local address). If SGNS gets an
                         Interface identification with 0, the SGSN follows step 6 in
                         section 3.1
               
                      5. MS keeps the link-local address, and extracts the
               
               
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                                            October 2003
               
               
                         interface identifier for later use. UE may send a Router
                          Solicitation message to GGSN (first hop router).
               
                      6. After the PDP Context Activation, the GGSN sends a Router
                         Advertisement to MS. MS should be configured not to send a
                         Neighbor Solicitation message. However, if one is sent,
                         the GGSN will silently discard it. The GGSN updates the SGSN
                         with the whole IPv6 address. In case of GGSN actions, some
                         classification method needs whether RS message is a start of a
                         session(in steps satisfying IETF recommendation) or the rest
                         of the session(in steps of legacy 3GPP autoconfiguration).
                         This can be possible for GGSN by checking the interface
                         identification whether it is allocated by GGSN itself or not.
               
               
               4. Security Considerations
               
                  The description of IPv6 usage in 3GPP networks does not have any
                  security considerations.
               
               
               5. References
               
               
                  [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9,
                      RFC 2026, October 1996.
               
                  [2] M Wasserman, "Recommendations for IPv6 in Third Generation
                      Partnership Project(3GPP) Standards", RFC 3314, September 2002
               
                  [3] 3GPP TS Group, "GPRS Service Description State2? 3GPP 23.060,
                      March, 2003
               
               
               Author' Addresses
               
                  Jae-Pil Yoo
                  Ph. D. Student in Konkuk University
                  Konkuk University Kwangjin gu Hwayangdong Seoul Korea
                  Email: willow@konkuk.ac.kr
               
                  Kee-cheon Kim
                  Professor in Konkuk University
                  Konkuk University Kwangjin gu Hwayangdong Seoul Korea
                  Email: kckim@konkuk.ac.kr
               
                  Jin-Pyo Hong
                  Professor in Hankook University of Foreign Study
                  89. Wangsan-ri Mohyun-myon. Yongin-shi. Kyongki-do. Korea
                  Email: jphong@hufs.ac.kr
               
                  Kyeong-Jin Lee
               
               
               
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                         IPv6 in 3GPP networks satisfying IETF's recommendations
                                            October 2003
               
               
                  ETRI / PEC
                  161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea
                  Phone: +82 42 860 6484
                  EMail: leekj@etri.re.kr
               
                  Hyoung-Jun Kim
                  ETRI / PEC
                  161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea
                  Phone: +82 42 860 6576
                  EMail: khj@etri.re.kr
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
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