The 3GPP2 Architecture

1. The 3GPP2 Architecture Sridhar Machiraju CS294-3, Spring 2002, University of California at Berkeley

2. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

3. Introduction We saw that the 3GPP architecture evolved from the already-existing GPRS network. It can be viewed as IP-based multimedia enhancements to 2G networks. However, 3GPP2 has created a new architecture (there was no existing packet packet data service) for the 2G and 3G CDMA air interfaces.

4. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

5. Basic Design Philosophy of 3GPP2 • Leverage existing globally-accepted IETF protocols whenever possible e.g., mobile IP (for mobility), IPSec (for e2e security), AAA (authentication, authorization and accounting for network access). • Some advantages are – • Interoperability/roaming with existing IP networks. • Easy deployment of new services. • Well understood standards.

6. The Official Reference Model!

7. A Simpler Version! Control of Services IP SCP SN PSTN Base Station Internet BTS BSC MSC PDN Traditional “Switching Point” SMS HLR VLR Packet data functions OTAF PDSN AAA

8. Much More Simpler! • BTS – Base Transceiver Station • BSC – Base Station Controller • MSC – Mobile Switching Center • PDSN - Packet Data Serving Node • HA – Home Agent • IWF – Inter-Working Function

9. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

10. A Mobility Perspective • Note that, for simple IP, the HA is not used. • AAA is used for data service authentication. • The PPP tunnel from the MS terminates at the PSDN which acts as the Foreign Agent (FA). • The PSDN is the first hop IP router and performs Diffserv shaping, ingress filtering, handoff between PCFs. • The PDSN is also responsible for forwarding accounting information to the appropriate AAA entity. • The PCF maintains a layer 2 connection with the PSDN for sending/receiving packets for MSs under its control.

11. The Ultimate Goal – An All-IP Network

12. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

13. 3GPP uses GGSN, SGSN nodes. 3GPP does not allow heterogeneous access. The HLR is likely to be used by the SGSN for authenticating data users. Thus, access and data network authentication are integrated. 3GPP2 uses mobile IP and PSDN as FA/HA . It allows heterogeneous access. The PDSN uses an AAA infrastructure to authenticate data users. Access and data network authentication are separate. Security and Mobility Management

14. The 3GPP model has a SIP-like functionality in the 3 types of Call State Control Functions (CSCF). Location service in the 3GPP model is tied closely to the access. GTP is used to provide link-layer mobility. Though the specification is yet to be published, 3GPP2 has decided to use SIP. In the 3GPP2 model, location service is more of a database i.e., access-independent. Link layer mobility in the 3GPP2 world is viewed as a direct extension of mobile IP. Services etc.

15. Note that, • Due to the lack of standards for SIP with all potential applications like VoIP, there is a danger of 3GPP and 3GPP2 coming up with incompatible extensions to SIP which would have to be harmonized sometime later. • The 3GPP2 specification is not as complete as the 3GPP specification. • In the 3GPP specification, there is an option to place a mobile IP-based Foreign Agent in the GGSN. Still, this would introduce a lot of tunneling overhead in the GGSN-SGSN path (Mobile IP over GTP over IP).

16. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

17. Multimedia IP Networks Multimedia IP Networks 3G-SGSN 3G-GGSN UTRAN BSS/ GERAN MSC Server G-MSC Server 3G-HLR BGCF MGCF CSCF 3G-HLR 3G-HLR CSCF Emergency Services Network 3GPP All-IP Network Architecture Model Applications & Services IP Multimedia Subsystem SCP Legacy mobile signalling Network T-SGW PSTN/ Legacy/External MRF MGW UMS R-SGW HSS CS Domain Application Service PS Domain GMLC Control Transport RAN MT TE Signaling only User Data and Signaling

18. 3GPP NAM - Discussion • 3GPP is divided into 4 planes – IP Multimedia, Packet-Switched, Data-Switched and Radio Access. • At each plane, there exist data and control functions. • The picture is very disorganized especially from traditional networking perspective. • Legacy transport gateways are on the same plane as applications. • HLR and Unified Messaging Service are in limbo. • As mentioned earlier, the location service is access dependent because of its presence in the lowest layer. • The CSCF has all the functionality; there is not much modularity. • Transport and Control reside in the same functional node often. • Applications have to talk to either of CSCF, HSS, SGSN. • QoS is implemented in CSCF and GGSN.

19. IP Network PSTN MAP 41 & GSM 3GPP2 All-IP Network Architecture Model Application Service Application Databases EIR DSI Sub Poli Service Roaming Signaling Gateway Subscription QoS Manager Network Capability Gateway Control Trunk Signaling Gateway Position Server AAA Session Control Manager Transport Media Gateway Control Core QoS Manager Position Determining Entity Media Resource Function Access Gateway FA/ Attendant Media Gateway Access Net. Signaling-Control BSC + PCF BTS Bearer MM Mobile IP Home Agent Radio Border Router Other Access Networks MS Legacy MS Domain Support

20. 3GPP2 NAM - Discussion • 3GPP2 fits into the Transport, Control, Service, Application Plane model much better. • The PSDN will have only the HA/FA functionality unlike the GSN nodes. • Applications talk to only the NCG. • The modularity of this model over the 3GPP model is seen in the case of the QoS manager. • The HLR, ESI, location information etc are captured as services available by querying databases.

21. Contents • Introduction • The 3GPP2 Architecture • Mobility Management in 3GPP2 • Functional comparison of 3GPP and 3GPP2. • Architectural comparison of 3GPP and 3GPP2 • The MWIF Architecture.

22. The Mobile Wireless Internet Forum (MWIF) • MWIF is a non-profit association of wireless companies whose objective is to define a single mobile wireless and Internet architecture independent of the access technology. • They have a network reference model to achieve this. Backwards compatibility is still a problem. • Notice the service discovery server in the MWIF architecture. • The CSCF functionality is in the CSM and Session Proxy.

23. Enterprise MAP 41 & GSM PSTN Intranet INTERNET MWIF All-IP Network Architecture Model Directory Services Application Functional Entities Resource Directory Policy Repository Profile Server Core Network Application(s) 3rd Party Application(s) Location Server Global Name Server Application Geographic Location Manager Service Discovery Server AAA Functional Entities Service Authentication Server Authorization Server Accounting Server Control Communications Session Manager (CSM) Home Mobility Manager Multimedia Resource Controller Resource Manager Transport Session Proxy Session Anchor Home IP Address Manager Multimedia Resource Function Media Gateway Controller Access Gateway Mobile Attendant Bearer Transport Gateway Functional Entities Access Transport Gateway i l Signaling-Control Signaling Gateway IP Gateway Media Gateway IP Address Manager Access Network Terminal UIM

24. Summary • Though the 3GPP and 3GPP2 NAM differ, active harmonization initiatives such as MWIF are cause for optimism. • Remember that harmonization on the access is also being tried for (or else dual mode devices would be necessary). • SIP seems to be the choice for session initiation over H.323 and other protocols. • There are strong reasons for using IPv6 in 3G networks. But, all commercial 3G networks till date use IPv4 (since it is easier to deploy).