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Soininen, 3 Document: draft-ietf-v6ops-3gpp-cases-02.txt Editor 4 Expires: July 2003 Nokia 5 January 2003 7 Transition Scenarios for 3GPP Networks 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 Copyright Notice 31 Copyright (C) The Internet Society (2002). All Rights Reserved. 33 Abstract 35 This document describes different scenarios in Third Generation 36 Partnership Project (3GPP) defined packet network, i.e. General 37 Packet Radio Service (GPRS) that would need IP version 6 and IP 38 version 4 transition. The focus of this document is on the scenarios 39 where the User Equipment (UE) connects to nodes in other networks, 40 e.g. in the Internet. GPRS network internal transition scenarios, 41 i.e. between different GPRS elements in the network, are out of scope 42 of this document. 44 The purpose of the document is to list the scenarios for further 45 discussion and study. 47 Table of Contents 49 1. Introduction...................................................2 50 2. Scope of the document..........................................2 51 3. Brief description of the 3GPP network environment..............3 52 3.1 GPRS architecture basics...................................3 53 3.2 IP Multimedia Core Network Subsystem (IMS).................4 54 4. Transition scenarios...........................................5 55 4.1 GPRS Scenarios.............................................5 56 4.2 Transition scenarios with IMS..............................8 57 5. Security Considerations........................................9 58 Authors...........................................................9 59 Informative references...........................................10 60 Normative References.............................................10 61 Editor's Address.................................................10 63 Copyright 65 (C) The Internet Society (2002). All Rights Reserved. 67 1. Introduction 69 This document will describe the transition scenarios in 3GPP packet 70 data networks that might come up in the deployment phase of IPv6. 71 The main purpose of this document is to identify, and document those 72 scenarios for further discussion, and for study in the v6ops working 73 group. 75 This document gives neither an overview, nor an explanation of 3GPP 76 or the 3GPP packet data network, GPRS. A good overview of the 3GPP 77 specified GPRS can be found from [1]. The GPRS architecture 78 specification is defined in [2]. 80 2. Scope of the document 82 The scope of this document is to describe the possible transition 83 scenarios in the 3GPP defined GPRS network where a UE connects to, or 84 is contacted from, the Internet or another UE. The document describes 85 scenarios with and without the usage of the SIP based IP Multimedia 86 Core Network Subsystem (IMS). 88 The scope of this document does not include scenarios inside the GPRS 89 network, i.e. on the different interfaces of the GPRS network. This 90 document neither changes 3GPP specifications, nor proposes changes to 91 the current specifications. 93 In addition, this document describes the possible transition 94 scenarios. The solutions will be documented in a separate document. 96 These scenarios may or may not be found feasible, or even likely in 97 further study. 99 3. Brief description of the 3GPP network environment 101 This section describes the most important concepts of the 3GPP 102 environment for understanding the transition scenarios. The first 103 part of the description gives a brief overview to the GPRS network as 104 such. The second part concentrates on the IP Multimedia Core Network 105 Subsystem (IMS). 107 3.1 GPRS architecture basics 109 This section gives an overview to the most important concepts of the 110 3GPP packet architecture. For more detailed description, please see 111 [2]. 113 From the point of view of this document, the most relevant 3GPP 114 architectural elements are the User Equipment (UE), and the Gateway 115 GPRS Support Node (GGSN). A simplified picture of the architecture is 116 shown in Figure 1. 118 The UE is the mobile phone. It can either be an integrated device 119 comprised of a combined GPRS part, and the IP stack, or it might be a 120 separate GPRS device, and a separate equipment with the IP stack, 121 e.g. a laptop. 123 The GGSN serves as an anchor-point for the GPRS mobility management. 124 It also serves as the default router for the UE. 126 The Peer node mentioned in the picture refers to a node with which 127 the UE is communicating. 129 -- ---- ************ --------- 130 |UE|- ... -|GGSN|--+--* IPv4/v6 NW *--+--|Peer node| 131 -- ---- ************ --------- 132 Figure 1: Simplified GPRS Architecture 134 There is a dedicated link between the UE, and the GGSN called the 135 Packet Data Protocol (PDP) Context. This link is created through the 136 PDP Context activation process. During the activation the UE is 137 configured with its IP address, and other information needed to 138 maintain IP access, e.g. DNS server address. There are three 139 different types of PDP Contexts: IPv4, IPv6, and Point-to-Point 140 Protocol (PPP). 142 A UE can have one or more simultaneous PDP Contexts open to the same 143 or to different GGSNs. The PDP Context can be either of the same, or 144 different types. 146 3.2 IP Multimedia Core Network Subsystem (IMS) 148 IP Multimedia Core Network Subsystem (IMS) is a SIP based multimedia 149 service architecture. It is specified in Release 5 of 3GPP. This 150 section provides an overview of the 3GPP IMS and is not intended to 151 be comprehensive. A more detailed description can be found in [3], 152 [4] and [5]. 154 The IMS comprises a set of SIP proxies, servers, and registrars. In 155 addition, there are Media Gateways (MGWs) that offer connections to 156 non-IP networks such as the Public Switched Telephony Network (PSTN). 157 A simplified overview of the IMS is depicted in figure 2. 158 +-------------+ +-------------------------------------+ 159 | | | +------+ | 160 | | | |S-CSCF|--- 161 | | | | +------+ | 162 +-|+ | | | / | 163 | | | SIP Sig. | | +------+ +------+ | 164 | |----|------+------|--|----|P-CSCF|----------|I-CSCF| | 165 | | | | | +------+ +------+ | 166 | |-----------+------------------------------------------------ 167 +--+ | User traf. | | | 168 UE | | | | 169 | GPRS access | | IP Multimedia CN Subsystem | 170 +-------------+ +-------------------------------------+ 171 Figure 2: Overview of the 3GPP IMS architecture 173 The SIP proxies, servers, and registrars shown in Figure 2 are as 174 follows. 176 - P-CSCF (Proxy-Call Session Control Function) is the first 177 contact point within the IMS for the subscriber. 179 - I-CSCF (Interrogating-CSCF) is the contact point within an 180 operator�s network for all connections destined to a subscriber 181 of that network operator, or a roaming subscriber currently 182 located within that network operator�s service area. 184 - S-CSCF (Serving-CSCF) performs the session control services for 185 the subscriber. It also behaves as a SIP Registrar. 187 IMS UEs use the GPRS as an access network for the IMS. Thus, a UE has 188 to have an activated PDP Context to the IMS before it can proceed to 189 use the IMS services. The PDP Context activation is explained briefly 190 in section 3.1. 192 The IMS is exclusively IPv6. Thus, the activated PDP Context is of 193 PDP Type IPv6. This means that an 3GPP IP Multimedia terminal uses 194 exclusively IPv6 to access the IMS, and the IMS SIP server and proxy 195 support exclusively IPv6. Hence, all the traffic going to the IMS is 196 IPv6, even if the UE is dual stack capable - this comprises both 197 signaling and user traffic. 199 This, of course, does not prevent the usage of other unrelated 200 services (e.g. corporate access) on IPv4. 202 4. Transition scenarios 204 This section is divided into two main parts - GPRS scenarios, and 205 scenarios with the IP Multimedia Subsystem (IMS). The first part - 206 GPRS scenarios - concentrates on scenarios with a User Equipment (UE) 207 connecting to services in the Internet, e.g. mail, web. The second 208 part - IMS scenarios - then describes how an IMS capable UE can 209 connect to other SIP capable nodes in the Internet using the IMS 210 services. 212 4.1 GPRS Scenarios 214 This section describes the scenarios that might occur when a GPRS UE 215 contacts services, or nodes outside the GPRS network, e.g. web-server 216 in the Internet. 218 Transition scenarios of the GPRS internal interfaces are outside of 219 the scope of this document. 221 The following scenarios are described here. In all of the scenarios, 222 the UE is part of a network where there is at least one router of the 223 same IP version, i.e. GGSN, and it is connecting to a node in a 224 different network. 226 The scenarios here apply also for PDP Context type Point-to-Point 227 Protocol (PPP) where PPP is terminated at the GGSN. On the other 228 hand, where the PPP PDP Context is terminated e.g. at an external 229 ISP, the environment is the same as for general ISP cases. 231 1) Dual Stack UE connecting to IPv4 and IPv6 nodes 232 2) IPv6 UE connecting to an IPv6 node through an IPv4 network 233 3) IPv4 UE connecting to an IPv4 node through an IPv6 network 234 4) IPv6 UE connecting to an IPv4 node 235 5) IPv4 UE connecting to an IPv6 node 237 1) Dual Stack UE connecting to IPv4 and IPv6 nodes 239 The GPRS system has been designed in a manner that there is the 240 possibility to have simultaneous IPv4, and IPv6 PDP Contexts open. 241 Thus, in cases where the UE is dual stack capable, and in the network 242 there is a GGSN (or separate GGSNs) that supports both connection to 243 IPv4 and IPv6 networks, it is possible to connect to both at the same 244 time. Figure 3 depicts this scenario. 246 +-------------+ 247 | | 248 | UE | +------+ 249 | | | IPv4 | 250 | | /| | 251 |------|------+ / +------+ 252 | IPv6 | IPv4 | +--------+ / 253 +-------------+ IPv4 | | / 254 | |------------------------| |/ 255 | | | 256 | IPv6 | GGSN |\ 257 |-------------------------------| | \ 258 +-----------+ | | \ +------+ 259 | GPRS Core | | | \ | IPv6 | 260 +-----------+ +--------+ | | 261 +------+ 262 Figure 3: Dual-Stack Case 264 However, the IPv4 addresses might be a scarce resource for the mobile 265 operator or an ISP. In that case, it might not be possible for the UE 266 to have a globally unique IPv4 address allocated all the time. Hence, 267 the UE should either activate the IPv4 PDP Context only when needed, 268 or be allocated an IPv4 address from a private address space. 270 2) IPv6 UE connecting to an IPv6 node through an IPv4 network 272 Especially in the first stages of IPv6 deployment, there are cases 273 where an IPv6 node would need to connect to the IPv6 Internet through 274 a network that is IPv4. For instance, this can be seen in current 275 fixed networks, where the access is provided in IPv4 only, but there 276 is an IPv6 network deeper in the Internet. This scenario is shown in 277 the Figure 4. 279 +------+ +------+ 280 | | | | +------+ 281 | UE |------------------| |-----------------| | 282 | | +-----------+ | GGSN | +---------+ | IPv6 | 283 | IPv6 | | GPRS Core | | | | IPv4 Net| | | 284 +------+ +-----------+ +------+ +---------+ +------+ 285 Figure 4: IPv6 nodes communicating over IPv4 287 In this case, in the GPRS system, the UE would be IPv6 capable, and 288 the GPRS network would provide an IPv6 capable GGSN in the network. 289 However, there is an IPv4 network between the GGSN, and the peer 290 node. 292 3) IPv4 UE connecting to an IPv4 node through an IPv6 network 294 Further in the future, there are cases where the legacy UEs are still 295 IPv4 only, capable of connecting only to the legacy IPv4 Internet. 296 However, the GPRS operator network has already been upgraded to IPv6. 297 Figure 5 represents this scenario. 299 +------+ +------+ 300 | | | | +------+ 301 | UE |------------------| |-----------------| | 302 | | +-----------+ | GGSN | +---------+ | IPv4 | 303 | IPv4 | | GPRS Core | | | | IPv6 Net| | | 304 +------+ +-----------+ +------+ +---------+ +------+ 305 Figure 5: IPv4 nodes communicating over IPv6 307 In this case, the operator would still provide an IPv4 capable GGSN, 308 and a connection through the IPv6 network to the IPv4 Internet. 310 4) IPv6 UE connecting to an IPv4 node 312 In this scenario an IPv6 UE connects to an IPv4 node in the IPv4 313 Internet. As an example, an IPv6 UE connects to an IPv4 web server in 314 the legacy Internet. In the figure 6, this kind of possible 315 installation is described. 317 +------+ +------+ 318 | | | | +---+ +------+ 319 | UE |------------------| |-----| |----| | 320 | | +-----------+ | GGSN | | ? | | IPv4 | 321 | IPv6 | | GPRS Core | | | | | | | 322 +------+ +-----------+ +------+ +---+ +------+ 323 Figure 6: IPv6 node communicating with IPv4 node 325 5) IPv4 UE connecting to an IPv6 node 327 This is similar to the case above, but in the opposite direction. 328 Here an IPv4 UE connects to an IPv6 node in the IPv6 Internet. As an 329 example, a legacy IPv4 UE is connected to an IPv6 server in the IPv6 330 Internet. Figure 7 depicts this configuration. 332 +------+ +------+ 333 | | | | +---+ +------+ 334 | UE |------------------| |-----| |----| | 335 | | +-----------+ | GGSN | | ? | | IPv6 | 336 | IPv4 | | GPRS Core | | | | | | | 337 +------+ +-----------+ +------+ +---+ +------+ 338 Figure 7: IPv4 node communicating with IPv6 node 340 4.2 Transition scenarios with IMS 342 As described in section 3.2, IMS is exclusively IPv6. Thus, the 343 number of possible transition scenarios is reduced dramatically. In 344 the following, the possible transition scenarios are listed. 346 1) UE connecting to a node in an IPv4 network through IMS 347 2) Two IPv6 IMS connected via an IPv4 network 349 1) UE connecting to a node in an IPv4 network through IMS 351 This scenario occurs when an IMS UE (IPv6) connects to a node in the 352 IPv4 Internet through the IMS, or vice versa. This happens when the 353 other node is a part of a different system than 3GPP, e.g. a fixed 354 PC, with only IPv4 capabilities. This scenario is shown in the Figure 355 8. 357 +------+ +------+ +-----+ 358 | | | | | | +---+ +------+ 359 | UE |-...-| |-----| IMS |--| |--| | 360 | | | GGSN | | | | ? | | IPv4 | 361 | IPv6 | | | | | | | | | 362 +------+ +------+ +-----+ +---+ +------+ 363 Figure 8: IMS UE connecting to an IPv4 node 365 2) Two IPv6 IMS connected via an IPv4 network 367 At the early stages of IMS deployment, there may be cases where two 368 IMS islands are only connected via an IPv4 network such as the legacy 369 Internet. See Figure 9 for illustration. 371 +------+ +------+ +-----+ +-----+ 372 | | | | | | | | 373 | UE |-...-| |-----| IMS |--------| | 374 | | | GGSN | | |+------+| IMS | 375 | IPv6 | | | | || IPv4 || | 376 +------+ +------+ +-----++------++-----+ 377 Figure 9: Two IMS islands connected over IPv4 379 5. Security Considerations 381 This document does not generate any additional security 382 considerations. 384 Authors 386 This is document is a result of a joint effort of a design team. The 387 members of the design team are listed in the following. 389 Alain Durand, Sun Microsystems 390 392 Karim El-Malki, Ericsson Radio Systems 393 395 Niall Richard Murphy, Enigma Consulting Limited 396 398 Hugh Shieh, AT&T Wireless 399 401 Jonne Soininen, Nokia 402 404 Hesham Soliman, Ericsson Radio Systems 405 407 Margaret Wasserman, Wind River 408 410 Juha Wiljakka, Nokia 411 413 Acknowledgements 415 The authors would like to thank Basavaraj Patil, Tuomo Sipil�, Fred 416 Templin, Rod Van Meter, and Jens Staack for good input, and comments 417 that helped writing this document. 419 Informative references 421 [1] Wasserman, M., "Recommendations for IPv6 in Third Generation 422 Partnership Project (3GPP) Standards", September 2002, RFC3314. 424 Normative References 426 [2] 3GPP TS 23.060 v 5.2.0, "General Packet Radio Service (GPRS); 427 Service description; Stage 2(Release 5)", June 2002. 429 [3] 3GPP TS 23.228 v 5.3.0, "IP Multimedia Subsystem (IMS); Stage 430 2(Release 5)", January 2002. 432 [4] 3GPP TS 24.228 V5.0.0, "Signalling flows for the IP multimedia 433 call control based on SIP and SDP; Stage 3 (Release 5)", March 434 2002. 436 [5] 3GPP TS 24.229 V5.0.0, "IP Multimedia Call Control Protocol 437 based on SIP and SDP; Stage 3 (Release 5)", March 2002. 439 Editor's Address 441 Jonne Soininen 442 Nokia 443 313 Fairchild Dr. Phone: +1-650-864-6794 444 Mountain View, CA, USA Email: jonne.Soininen@nokia.com