RFC 3574
Transition Scenarios for 3GPP Networks
RFC 3574: Transition Scenarios for 3GPP Networks 🦋
Okay bestie, let's dive into RFC 3574 ✨ It's titled Transition Scenarios for 3GPP Networks, written by J. Soininen, Ed. from Nokia, under the Network Working Group. It's an Informational doc, dated August 2003. So it's not a standard, it's a "here's what we're looking at" kind of document 💅
Status of this Memo
This memo is giving info for the Internet community 🌸 It does not specify an Internet standard of any kind, so nothing here is a rule you have to follow. Distribution of this memo is unlimited, so share it with everyone 💜
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. 🎀
Abstract
Okay so this doc describes different scenarios in the Third Generation Partnership Project (3GPP) defined packet network, which is the General Packet Radio Service (GPRS). These scenarios would need IP version 6 and IP version 4 transition 🔥 The main focus is on cases where the User Equipment (UE) connects to nodes in other networks, like the Internet. GPRS network internal transition scenarios, meaning the stuff between different GPRS elements in the network, are out of scope 🙈 The whole point is to list the scenarios so people can discuss and study them later 🧚
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scope of the Document. . . . . . . . . . . . . . . . . . . . . 2
3. Brief Description of the 3GPP Network Environment. . . . . . . 2
3.1 GPRS Architecture Basics . . . . . . . . . . . . . . . . . 3
3.2 IP Multimedia Core Network Subsystem (IMS) . . . . . . . . 3
4. Transition Scenarios . . . . . . . . . . . . . . . . . . . . . 5
4.1 GPRS Scenarios . . . . . . . . . . . . . . . . . . . . . . 5
4.2 IMS Scenarios . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations. . . . . . . . . . . . . . . . . . . . 9
6. Contributing Authors . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
9. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 11
10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 121. Introduction ✨
Okay so this document describes the transition scenarios in 3GPP packet data networks that might come up when IPv6 gets deployed 🦋 The main goal is to identify and document those scenarios so the v6ops working group can discuss and study them 💖
We also give a quick overview of the 3GPP packet data network, GPRS, so you can actually follow the transition scenarios 🌈 If you want a deeper dive on the 3GPP specified GPRS, check out [6]. The GPRS architecture itself is defined in [1].
2. Scope of the Document
The scope is describing the possible transition scenarios in the 3GPP defined GPRS network, where a UE connects to the Internet or another UE, or gets contacted from there 🫶 The doc covers scenarios both with and without the SIP-based (Session Initiation Protocol [5]) IP Multimedia Core Network Subsystem (IMS). The 3GPP releases 1999, 4, and 5 are the basis here 🎀
Anything inside the GPRS network, meaning on its different interfaces, is out of scope 🙈 This document doesn't change 3GPP specifications, and it doesn't propose changes to the current ones either.
The possible transition scenarios are described here, but the solutions will be documented in a separate document 🌸
All the possible scenarios are listed here. Further analysis may show that some of them aren't actually relevant in this context, so no stress 💅
3. Brief Description of the 3GPP Network Environment
This section covers the most important 3GPP concepts you need to get the transition scenarios 💜 The first part gives a quick overview of the GPRS network itself. The second part focuses on the IP Multimedia Core Network Subsystem (IMS) 🧚
3.1. GPRS Architecture Basics
This section gives an overview of the most important concepts in the 3GPP packet architecture. For a more detailed description, see [1] 📖
From the point of view of this document, the most relevant 3GPP architectural elements are the User Equipment (UE) and the Gateway GPRS Support Node (GGSN) 👑 A simplified picture of the architecture is shown in Figure 1.
The UE is the mobile phone 📱 It can either be an integrated device with a combined GPRS part and the IP stack, or it might be a separate GPRS device plus separate equipment with the IP stack, like a laptop 💻
The GGSN is an anchor point for GPRS mobility management. It also acts as the default router for the UE 🦋
The Peer node in the picture is a node the UE is talking to 🫶
-- ---- ************ ---------
|UE|- ... -|GGSN|--+--* IPv4/v6 NW *--+--|Peer node|
-- ---- ************ ---------
Figure 1: Simplified GPRS ArchitectureSo there's a dedicated link between the UE and the GGSN called the Packet Data Protocol (PDP) Context ✨ This link gets created through the PDP Context activation process. During activation, the UE gets configured with its IP address and other info it needs to keep IP access working, like a DNS server address 🌈 There are three types of PDP Contexts: IPv4, IPv6, and Point-to-Point Protocol (PPP) 🔥
A UE can have one or more simultaneous PDP Contexts open to the same GGSN or to different GGSNs. The PDP Contexts can be the same type or different types 💖
3.2. IP Multimedia Core Network Subsystem (IMS)
The IP Multimedia Core Network Subsystem (IMS) is an architecture for supporting multimedia services over a SIP infrastructure 🎀 It's specified in 3GPP Release 5. This section gives an overview of the 3GPP IMS and isn't meant to be comprehensive, so for more detail check [2], [3] and [4] 📚
The IMS is made of a set of SIP proxies, servers, and registrars 🧚 There are also Media Gateways (MGWs) that connect to non-IP networks like the Public Switched Telephony Network (PSTN) 🌸 A simplified overview of the IMS is shown in Figure 2.
+-------------+ +-------------------------------------+
| | | +------+ |
| | | |S-CSCF|---
| | | | +------+ |
+-|+ | | | / |
| | | SIP Sig. | | +------+ +------+ |
| |----|------+------|--|----|P-CSCF|----------|I-CSCF| |
| | | | | +------+ +------+ |
| |-----------+------------------------------------------------
+--+ | User traf. | | |
UE | | | |
| GPRS access | | IP Multimedia CN Subsystem |
+-------------+ +-------------------------------------+
Figure 2: Overview of the 3GPP IMS architectureThe SIP proxies, servers, and registrars in Figure 2 are these 🍓
- P-CSCF (Proxy-Call Session Control Function) is the first contact point within the IMS for the subscriber 🌟
- I-CSCF (Interrogating-CSCF) is the contact point within an operator's network for all connections going to a subscriber of that operator, or to a roaming subscriber currently located in that operator's service area 🗺️
- S-CSCF (Serving-CSCF) does the session control services for the subscriber. It also acts as a SIP Registrar 👑
IMS capable UEs use the GPRS network as their access network to reach the IMS 🦋 So a UE needs an activated PDP Context to the IMS before it can use any IMS services. The PDP Context activation is briefly explained in section 3.1 💅
The IMS is exclusively IPv6 😭 So the activated PDP Context is of PDP Type IPv6. That means a 3GPP IP Multimedia terminal uses exclusively IPv6 to access the IMS, and the IMS SIP server and proxy support exclusively IPv6. Therefore all the traffic going to the IMS is IPv6, even if the UE is dual stack capable. This covers both signaling and user traffic 🔥
Obviously this doesn't stop other unrelated services, like corporate access, from using IPv4 🌈
4. Transition Scenarios ✨
This section has two main parts: GPRS scenarios, and scenarios with the IP Multimedia Subsystem (IMS) 💖 The first part, the GPRS scenarios, is about a User Equipment (UE) connecting to services on the Internet, like mail or web 🎀 The second part, the IMS scenarios, describes how an IMS capable UE can connect to other SIP-capable nodes on the Internet using the IMS services 🧚
4.1. GPRS Scenarios ✨
okay bestie, this section is about the scenarios that can happen when a GPRS UE (user equipment) reaches out to services or nodes outside the GPRS network, like a web server on the Internet 🌐💖
Transition scenarios of the GPRS internal interfaces are outside the scope of this document, so we're not going there today 🙅♀️
Here's the lineup. In every scenario, the UE is part of a network with at least one router of the same IP version, i.e., a GGSN, and it's 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
The scenarios here also apply to PDP Context type Point-to-Point Protocol (PPP) where PPP is terminated at the GGSN. But if the PPP PDP Context is terminated somewhere else, like an external ISP, the environment is the same as the general ISP cases 🧚
1) Dual Stack UE connecting to IPv4 and IPv6 nodes
The GPRS system is set up so you can have IPv4 and IPv6 PDP Contexts open at the same time 🦋 So if the UE is dual stack capable, and the network has a GGSN (or separate GGSNs) that supports connections to both IPv4 and IPv6 networks, it can connect to both at once. Figure 3 shows this slay 👑
+-------------+
| |
| UE | +------+
| | | IPv4 |
| | /| |
|------|------+ / +------+
| IPv6 | IPv4 | +--------+ /
+-------------+ IPv4 | | /
| |------------------------| |/
| | |
| IPv6 | GGSN |\
|-------------------------------| | \
+-----------+ | | \ +------+
| GPRS Core | | | \ | IPv6 |
+-----------+ +--------+ \| |
+------+Figure 3: Dual-Stack Case
BUT (and this is a big but 😭) IPv4 addresses can be a scarce resource for the mobile operator or an ISP. So the UE might not be able to have a globally unique IPv4 address allocated all the time. In that case, the UE could either activate the IPv4 PDP Context only when it's needed, or be allocated an IPv4 address from a private address space 🫶
2) IPv6 UE connecting to an IPv6 node through an IPv4 network
Especially in the early days of IPv6 deployment, an IPv6 node might need to reach the IPv6 Internet through a network that's only IPv4 🌸 For example, this happens in current fixed networks, where access is provided over IPv4 only, but there's an IPv6 network further into the Internet. Figure 4 shows this one.
+------+ +------+
| | | | +------+
| UE |------------------| |-----------------| |
| | +-----------+ | GGSN | +---------+ | IPv6 |
| IPv6 | | GPRS Core | | | | IPv4 Net| | |
+------+ +-----------+ +------+ +---------+ +------+Figure 4: IPv6 nodes communicating over IPv4
In this case, in the GPRS system, the UE is IPv6 capable, and the GPRS network provides an IPv6 capable GGSN. The catch is that there's an IPv4 network sitting between the GGSN and the peer node 🥺
3) IPv4 UE connecting to an IPv4 node through an IPv6 network
Further down the road, legacy UEs may still be IPv4 only, only able to connect to the legacy IPv4 Internet. Meanwhile, the GPRS operator network has already been upgraded to IPv6 🧚 Figure 5 shows this vibe.
+------+ +------+
| | | | +------+
| UE |------------------| |-----------------| |
| | +-----------+ | GGSN | +---------+ | IPv4 |
| IPv4 | | GPRS Core | | | | IPv6 Net| | |
+------+ +-----------+ +------+ +---------+ +------+Figure 5: IPv4 nodes communicating over IPv6
In this case, the operator would still provide an IPv4 capable GGSN, plus 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 on the IPv4 Internet. For example, an IPv6 UE connects to an IPv4 web server on the legacy Internet 🌐 Figure 6 describes this possible setup.
+------+ +------+
| | | | +---+ +------+
| UE |------------------| |-----| |----| |
| | +-----------+ | GGSN | | ? | | IPv4 |
| IPv6 | | GPRS Core | | | | | | |
+------+ +-----------+ +------+ +---+ +------+Figure 6: IPv6 node communicating with IPv4 node
5) IPv4 UE connecting to an IPv6 node
This is like the case above, but flipped 🔄 Here an IPv4 UE connects to an IPv6 node on the IPv6 Internet. For example, a legacy IPv4 UE connects to an IPv6 server on the IPv6 Internet. Figure 7 shows this setup.
+------+ +------+
| | | | +---+ +------+
| UE |------------------| |-----| |----| |
| | +-----------+ | GGSN | | ? | | IPv6 |
| IPv4 | | GPRS Core | | | | | | |
+------+ +-----------+ +------+ +---+ +------+Figure 7: IPv4 node communicating with IPv6 node
4.2. IMS Scenarios 🎀
As described in section 3.2, IMS is exclusively IPv6 🫶 That means the number of possible transition scenarios drops dramatically. So here are the possible ones, listed below.
- 1) UE connecting to a node in an IPv4 network through IMS
- 2) Two IPv6 IMS connected via an IPv4 network
1) UE connecting to a node in an IPv4 network through IMS
This happens when an IMS UE (IPv6) connects to a node on the IPv4 Internet through the IMS, or the other way around. It happens when the other node is part of a different system than 3GPP, e.g., a fixed PC with only IPv4 capabilities 💻 Figure 8 shows this one.
+------+ +------+ +-----+
| | | | | | +---+ +------+
| UE |-...-| |-----| IMS |--| |--| |
| | | GGSN | | | | ? | | IPv4 |
| IPv6 | | | | | | | | |
+------+ +------+ +-----+ +---+ +------+Figure 8: IMS UE connecting to an IPv4 node
2) Two IPv6 IMS connected via an IPv4 network
In the early stages of IMS deployment, there may be cases where two IMS islands are only connected through an IPv4 network, like the legacy Internet 🏝️ See Figure 9 for the visual.
+------+ +------+ +-----+ +-----+
| | | | | | | |
| UE |-...-| |-----| IMS |----------| |
| | | GGSN | | | +------+ | IMS |
| IPv6 | | | | | | IPv4 | | |
+------+ +------+ +-----+ +------+ +-----+Figure 9: Two IMS islands connected over IPv4
5. Security Considerations 🚨
This document describes possible transition scenarios for 3GPP networks for future study. Solutions and mechanisms are explored in other documents. The description of the 3GPP network scenarios does not have any security issues 🙈
6. Contributing Authors 🌈
This document is a result of a joint effort of a design team. The members of the design team are listed below 🧚
- Alain Durand, Sun Microsystems,
<Alain.Durand@sun.com> - Karim El-Malki, Ericsson Radio Systems,
<Karim.El-Malki@era.ericsson.se> - Niall Richard Murphy, Enigma Consulting Limited,
<niallm@enigma.ie> - Hugh Shieh, AT&T Wireless,
<hugh.shieh@attws.com> - Jonne Soininen, Nokia,
<jonne.soininen@nokia.com> - Hesham Soliman, Ericsson Radio Systems,
<hesham.soliman@era.ericsson.se> - Margaret Wasserman, Wind River,
<mrw@windriver.com> - Juha Wiljakka, Nokia,
<juha.wiljakka@nokia.com>
7. Acknowledgements 💖
The authors would like to thank Basavaraj Patil, Tuomo Sipila, Fred Templin, Rod Van Meter, Pekka Savola, Francis Dupont, Christine Fisher, Alain Baudot, Rod Walsh, and Jens Staack for good input, and for comments that helped write this document 🫶
8. References 📚
8.1. Normative References
- [1] 3GPP TS 23.060 v 5.2.0, "General Packet Radio Service (GPRS); Service description; Stage 2(Release 5)", June 2002.
- [2] 3GPP TS 23.228 v 5.3.0, " IP Multimedia Subsystem (IMS); Stage 2(Release 5)", January 2002.
- [3] 3GPP TS 24.228 V5.0.0, "Signalling flows for the IP multimedia call control based on SIP and SDP; Stage 3 (Release 5)", March 2002.
- [4] 3GPP TS 24.229 V5.0.0, "IP Multimedia Call Control Protocol based on SIP and SDP; Stage 3 (Release 5)", March 2002.
- [5] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002.
8.2. Informative References
- [6] Wasserman, M., "Recommendations for IPv6 in Third Generation Partnership Project (3GPP) Standards", RFC 3314, September 2002.
9. Editor's Address 📬
Jonne Soininen
Nokia
313 Fairchild Dr.
Mountain View, CA, USA
Phone: +1-650-864-6794
EMail: jonne.soininen@nokia.com10. Full Copyright Statement ✨
Okay bestie, the legal bit 💅 Copyright (C) The Internet Society (2003). All Rights Reserved. 🎀
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 🦋 However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations. The one exception is when it's needed for developing Internet standards, in which case the procedures for copyrights defined in the Internet Standards process must be followed. The other exception is when it's required to translate it into languages other than English. 🌍
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. 💜 So that's forever, no cap. ♾️
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 😭 Translation: no guarantees here, so read it carefully before you build anything. 🫶
Acknowledgement 🌸
Funding for the RFC Editor function is currently provided by the Internet Society. 👑 Thank you to the people keeping the RFC Editor running, because honestly the whole Internet's paperwork is giving main character energy. 🧚
📦 where this page comes from
- ietf: rfc3574 2003-08
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms