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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Draft J. Soininen, 3 Document: draft-ietf-v6ops-3gpp-cases-01.txt Editor 4 Expires: June 2003 Nokia 5 December 2002 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 References.......................................................10 60 Editor's Address.................................................10 62 Copyright 64 (C) The Internet Society (2002). All Rights Reserved. 66 1. Introduction 68 This document will describe the transition scenarios in 3GPP packet 69 data networks that might come up in the deployment phase of IPv6. 70 The main purpose of this document is to identify, and document those 71 scenarios for further discussion, and for study in the v6ops working 72 group. 74 This document gives neither an overview, nor an explanation of 3GPP 75 or the 3GPP packet data network, GPRS. A good overview of the 3GPP 76 specified GPRS can be found from [1]. The GPRS architecture 77 specification is defined in [2]. 79 2. Scope of the document 81 The scope of this document is to describe the possible transition 82 scenarios in the 3GPP defined GPRS network where a UE connects to, or 83 is contacted from, the Internet or another UE. The document describes 84 scenarios with and without the usage of the SIP based IP Multimedia 85 Core Network Subsystem (IMS). 87 The scope of this document does not include scenarios inside the GPRS 88 network, i.e. on the different interfaces of the GPRS network. This 89 document neither changes 3GPP specifications, nor proposes changes to 90 the current specifications. 92 In addition, this document describes the possible transition 93 scenarios. The solutions will be documented in a separate document. 95 These scenarios may or may not be found feasible, or even likely in 96 further study. 98 3. Brief description of the 3GPP network environment 100 This section describes the most important concepts of the 3GPP 101 environment for understanding the transition scenarios. The first 102 part of the description gives a brief overview to the GPRS network as 103 such. The second part concentrates on the IP Multimedia Core Network 104 Subsystem (IMS). 106 3.1 GPRS architecture basics 108 This section gives an overview to the most important concepts of the 109 3GPP packet architecture. For more detailed description, please see 110 [2]. 112 From the point of view of this document, the most relevant 3GPP 113 architectural elements are the User Equipment (UE), and the Gateway 114 GPRS Support Node (GGSN). A simplified picture of the architecture is 115 shown in Figure 1. 117 The UE is the mobile phone. It can either be an integrated device 118 comprised of a combined GPRS part, and the IP stack, or it might be a 119 separate GPRS device, and a separate equipment with the IP stack, 120 e.g. a laptop. 122 The GGSN serves as an anchor-point for the GPRS mobility management. 123 It also serves as the default router for the UE. 125 The Peer node mentioned in the picture refers to a node with which 126 the UE is communicating. 128 -- ---- ************ --------- 129 |UE|- ... -|GGSN|--+--* IPv4/v6 NW *--+--|Peer node| 130 -- ---- ************ --------- 131 Figure 1: Simplified GPRS Architecture 133 There is a dedicated link between the UE, and the GGSN called the 134 Packet Data Protocol (PDP) Context. This link is created through the 135 PDP Context activation process. During the activation the UE is 136 configured with its IP address, and other information needed to 137 maintain IP access, e.g. DNS server address. There are three 138 different types of PDP Contexts: IPv4, IPv6, and Point-to-Point 139 Protocol (PPP). 141 A UE can have one or more simultaneous PDP Contexts open to the same 142 or to different GGSNs. The PDP Context can be either of the same, or 143 different types. 145 3.2 IP Multimedia Core Network Subsystem (IMS) 147 IP Multimedia Core Network Subsystem (IMS) is a SIP based multimedia 148 service architecture. It is specified in Release 5 of 3GPP. This 149 section provides an overview of the 3GPP IMS and is not intended to 150 be comprehensive. A more detailed description can be found in [3], 151 [4] and [5]. 153 The IMS comprises a set of SIP proxies, servers, and registrars. In 154 addition, there are Media Gateways (MGWs) that offer connections to 155 non-IP networks such as the Public Switched Telephony Network (PSTN). 156 A simplified overview of the IMS is depicted in figure 2. 157 +-------------+ +-------------------------------------+ 158 | | | +------+ | 159 | | | |S-CSCF|--- 160 | | | | +------+ | 161 +-|+ | | | / | 162 | | | SIP Sig. | | +------+ +------+ | 163 | |----|------+------|--|----|P-CSCF|----------|I-CSCF| | 164 | | | | | +------+ +------+ | 165 | |-----------+------------------------------------------------ 166 +--+ | User traf. | | | 167 UE | | | | 168 | GPRS access | | IP Multimedia CN Subsystem | 169 +-------------+ +-------------------------------------+ 170 Figure 2: Overview of the 3GPP IMS architecture 172 The SIP proxies, servers, and registrars shown in Figure 2 are as 173 follows. 175 - P-CSCF (Proxy-Call Session Control Function) is the first 176 contact point within the IMS for the subscriber. 178 - I-CSCF (Interrogating-CSCF) is the contact point within an 179 operator�s network for all connections destined to a subscriber 180 of that network operator, or a roaming subscriber currently 181 located within that network operator�s service area. 183 - S-CSCF (Serving-CSCF) performs the session control services for 184 the subscriber. It also behaves as a SIP Registrar. 186 IMS UEs use the GPRS as an access network for the IMS. Thus, a UE has 187 to have an activated PDP Context to the IMS before it can proceed to 188 use the IMS services. The PDP Context activation is explained briefly 189 in section 3.1. 191 The IMS is exclusively IPv6. Thus, the activated PDP Context is of 192 PDP Type IPv6. This means that an 3GPP IP Multimedia terminal uses 193 exclusively IPv6 to access the IMS, and the IMS SIP server and proxy 194 support exclusively IPv6. Hence, all the traffic going to the IMS is 195 IPv6, even if the UE is dual stack capable - this comprises both 196 signaling and user traffic. 198 This, of course, does not prevent the usage of other unrelated 199 services (e.g. corporate access) on IPv4. 201 4. Transition scenarios 203 This section is divided into two main parts - GPRS scenarios, and 204 scenarios with the IP Multimedia Subsystem (IMS). The first part - 205 GPRS scenarios - concentrates on scenarios with a User Equipment (UE) 206 connecting to services in the Internet, e.g. mail, web. The second 207 part - IMS scenarios - then describes how an IMS capable UE can 208 connect to other SIP capable nodes in the Internet using the IMS 209 services. 211 4.1 GPRS Scenarios 213 This section describes the scenarios that might occur when a GPRS UE 214 contacts services, or nodes outside the GPRS network, e.g. web-server 215 in the Internet. 217 Transition scenarios of the GPRS internal interfaces are outside of 218 the scope of this document. 220 The following scenarios are described here. In all of the scenarios, 221 the UE is part of a network where there is at least one router of the 222 same IP version, i.e. GGSN, and it is connecting to a node in a 223 different network. 225 The scenarios here apply also for PDP Context type Point-to-Point 226 Protocol (PPP) where PPP is terminated at the GGSN. On the other 227 hand, where the PPP PDP Context is terminated e.g. at an external 228 ISP, the environment is the same as for general ISP cases. 230 1) Dual Stack UE connecting to IPv4 and IPv6 nodes 231 2) IPv6 UE connecting to an IPv6 node through an IPv4 network 232 3) IPv4 UE connecting to an IPv4 node through an IPv6 network 233 4) IPv6 UE connecting to an IPv4 node 234 5) IPv4 UE connecting to an IPv6 node 236 1) Dual Stack UE connecting to IPv4 and IPv6 nodes 238 The GPRS system has been designed in a manner that there is the 239 possibility to have simultaneous IPv4, and IPv6 PDP Contexts open. 240 Thus, in cases where the UE is dual stack capable, and in the network 241 there is a GGSN (or separate GGSNs) that supports both connection to 242 IPv4 and IPv6 networks, it is possible to connect to both at the same 243 time. Figure 3 depicts this scenario. 245 +-------------+ 246 | | 247 | UE | +------+ 248 | | | IPv4 | 249 | | /| | 250 |------|------+ / +------+ 251 | IPv6 | IPv4 | +--------+ / 252 +-------------+ IPv4 | | / 253 | |------------------------| |/ 254 | | | 255 | IPv6 | GGSN |\ 256 |-------------------------------| | \ 257 +-----------+ | | \ +------+ 258 | GPRS Core | | | \ | IPv6 | 259 +-----------+ +--------+ | | 260 +------+ 261 Figure 3: Dual-Stack Case 263 However, the IPv4 addresses might be a scarce resource for the mobile 264 operator or an ISP. In that case, it might not be possible for the UE 265 to have a globally unique IPv4 address allocated all the time. Hence, 266 the UE should either activate the IPv4 PDP Context only when needed, 267 or be allocated an IPv4 address from a private address space. 269 2) IPv6 UE connecting to an IPv6 node through an IPv4 network 271 Especially in the first stages of IPv6 deployment, there are cases 272 where an IPv6 node would need to connect to the IPv6 Internet through 273 a network that is IPv4. For instance, this can be seen in current 274 fixed networks, where the access is provided in IPv4 only, but there 275 is an IPv6 network deeper in the Internet. This scenario is shown in 276 the Figure 4. 278 +------+ +------+ 279 | | | | +------+ 280 | UE |------------------| |-----------------| | 281 | | +-----------+ | GGSN | +---------+ | IPv6 | 282 | IPv6 | | GPRS Core | | | | IPv4 Net| | | 283 +------+ +-----------+ +------+ +---------+ +------+ 284 Figure 4: IPv6 nodes communicating over IPv4 286 In this case, in the GPRS system, the UE would be IPv6 capable, and 287 the GPRS network would provide an IPv6 capable GGSN in the network. 288 However, there is an IPv4 network between the GGSN, and the peer 289 node. 291 3) IPv4 UE connecting to an IPv4 node through an IPv6 network 293 Further in the future, there are cases where the legacy UEs are still 294 IPv4 only, capable of connecting only to the legacy IPv4 Internet. 295 However, the GPRS operator network has already been upgraded to IPv6. 296 Figure 5 represents this scenario. 298 +------+ +------+ 299 | | | | +------+ 300 | UE |------------------| |-----------------| | 301 | | +-----------+ | GGSN | +---------+ | IPv4 | 302 | IPv4 | | GPRS Core | | | | IPv6 Net| | | 303 +------+ +-----------+ +------+ +---------+ +------+ 304 Figure 5: IPv4 nodes communicating over IPv6 306 In this case, the operator would still provide an IPv4 capable GGSN, 307 and a connection through the IPv6 network to the IPv4 Internet. 309 4) IPv6 UE connecting to an IPv4 node 311 In this scenario an IPv6 UE connects to an IPv4 node in the IPv4 312 Internet. As an example, an IPv6 UE connects to an IPv4 web server in 313 the legacy Internet. In the figure 6, this kind of possible 314 installation is described. 316 +------+ +------+ 317 | | | | +---+ +------+ 318 | UE |------------------| |-----| |----| | 319 | | +-----------+ | GGSN | | ? | | IPv4 | 320 | IPv6 | | GPRS Core | | | | | | | 321 +------+ +-----------+ +------+ +---+ +------+ 322 Figure 6: IPv6 node communicating with IPv4 node 324 5) IPv4 UE connecting to an IPv6 node 326 This is similar to the case above, but in the opposite direction. 327 Here an IPv4 UE connects to an IPv6 node in the IPv6 Internet. As an 328 example, a legacy IPv4 UE is connected to an IPv6 server in the IPv6 329 Internet. Figure 7 depicts this configuration. 331 +------+ +------+ 332 | | | | +---+ +------+ 333 | UE |------------------| |-----| |----| | 334 | | +-----------+ | GGSN | | ? | | IPv6 | 335 | IPv4 | | GPRS Core | | | | | | | 336 +------+ +-----------+ +------+ +---+ +------+ 337 Figure 7: IPv4 node communicating with IPv6 node 339 4.2 Transition scenarios with IMS 341 As described in section 3.2, IMS is exclusively IPv6. Thus, the 342 number of possible transition scenarios is reduced dramatically. In 343 the following, the possible transition scenarios are listed. 345 1) UE connecting to a node in an IPv4 network through IMS 346 2) Two IPv6 IMS connected via an IPv4 network 348 1) UE connecting to a node in an IPv4 network through IMS 350 This scenario occurs when an IMS UE (IPv6) connects to a node in the 351 IPv4 Internet through the IMS, or vice versa. This happens when the 352 other node is a part of a different system than 3GPP, e.g. a fixed 353 PC, with only IPv4 capabilities. This scenario is shown in the Figure 354 8. 356 +------+ +------+ +-----+ 357 | | | | | | +---+ +------+ 358 | UE |-...-| |-----| IMS |--| |--| | 359 | | | GGSN | | | | ? | | IPv4 | 360 | IPv6 | | | | | | | | | 361 +------+ +------+ +-----+ +---+ +------+ 362 Figure 8: IMS UE connecting to an IPv4 node 364 2) Two IPv6 IMS connected via an IPv4 network 366 At the early stages of IMS deployment, there may be cases where two 367 IMS islands are only connected via an IPv4 network such as the legacy 368 Internet. See Figure 9 for illustration. 370 +------+ +------+ +-----+ +-----+ 371 | | | | | | | | 372 | UE |-...-| |-----| IMS |--------| | 373 | | | GGSN | | |+------+| IMS | 374 | IPv6 | | | | || IPv4 || | 375 +------+ +------+ +-----++------++-----+ 376 Figure 9: Two IMS islands connected over IPv4 378 5. Security Considerations 380 This document does not generate any additional security 381 considerations. 383 Authors 385 This is document is a result of a joint effort of a design team. The 386 members of the design team are listed in the following. 388 Alain Durand, Sun Microsystems 389 391 Karim El-Malki, Ericsson Radio Systems 392 394 Niall Richard Murphy, Enigma Consulting Limited 395 397 Hugh Shieh, AT&T Wireless 398 400 Jonne Soininen, Nokia 401 403 Hesham Soliman, Ericsson Radio Systems 404 406 Margaret Wasserman, Wind River 407 409 Juha Wiljakka, Nokia 410 412 Acknowledgements 414 The authors would like to thank Basavaraj Patil, Tuomo Sipil�, Fred 415 Templin, Rod Van Meter, and Jens Staack for good input, and comments 416 that helped writing this document. 418 References 420 [1] Wasserman, M., "Recommendations for IPv6 in Third Generation 421 Partnership Project (3GPP) Standards", September 2002, RFC3314. 423 [2] 3GPP TS 23.060 v 5.2.0, "General Packet Radio Service (GPRS); 424 Service description; Stage 2(Release 5)", June 2002. 426 [3] 3GPP TS 23.228 v 5.3.0, " IP Multimedia Subsystem (IMS); Stage 427 2(Release 5)", January 2002. 429 [4] 3GPP TS 24.228 V5.0.0, "Signalling flows for the IP multimedia 430 call control based on SIP and SDP; Stage 3 (Release 5)", March 431 2002. 433 [5] 3GPP TS 24.229 V5.0.0, "IP Multimedia Call Control Protocol 434 based on SIP and SDP; Stage 3 (Release 5)", March 2002. 436 Editor's Address 438 Jonne Soininen 439 Nokia 440 313 Fairchild Dr. Phone: +1-650-864-6794 441 Mountain View, CA, USA Email: jonne.Soininen@nokia.com