1. All-IP distributed (proxy) control model architecture Henrik Basilier, Ericsson ALLIP-20000717-011__ERI_distributed_CM

2. Roaming view of the architecture The inter-operator interfaces, that needs to be defined for purposes of supporting roaming subscribers are essential for the overall applicability of the 3GPP2 All-IP architecture ! => The NAM clearly needs to address these entities => A roaming view of the architecture is needed, to complement the reference model !

3. Assumptions A hybrid/distributed model is assumed, where the actual Session/Call Control is allowed to be either in the home network or in the visited network. The home network decides (has the final say about) where the control will be The decision is taken when the user registers Home control should be mandatory: - Operator A has to be able to allow users roaming from operator B (into A’s network) to have the control in B - Operator C can not assume operator D to support visited control (D must acknowledge/allow it) Localized services (e.g. 9-1-1) must be able to be served by the visited network

4. The session manager function in the IP MMed service layer is housed in a box that we label SCM for Session Control Manager, similar to CSCF used in 3GPP terminology. The new name is used to differentiate the function from the session manager function at the access level (housed in a box labeled ACS). We propose to name the box SCM for now. The SCM manages Sessions (Call Control) + all kinds of message routing (e.g SIP proxying) needed for the IP MMed service For explanatory purposes the SCM is labeled H-CSM when located in the home network and V-SCM when located in the visited network. Session Control Manager

5. Databases and framework servers HSS was used up to now to encompass databases and servers used to support framework functions such as Authentication, Authorization, Accounting, Address management, storage of user policy and network policies … However, by adopting a roaming view, it becomes very apparent that some of these functions are also required in the visited network, and confusion comes when referring to HSS when using these functions in the visited network.

6. Consequently, we propose to clearly define the required support functions such as local AAA, local directory server in the visited network and home AAA and directory server (global) in the home network. These set of support functions needed for all network operations in the visited network could be labeled VSF ( Visited support functions). Databases and framework servers

7. ACS Visited network Home network BSC+PCF HA H-SCM PDSN MGW MGCF MRF T-SGW R-SGW IP MMed domain only AAAL LDS AAAH DS HA V-SCM MGW MGCF MRFT-SGW R-SGW LS “VSF”“HSS”

8. Example Call Flows

9. Call Flows - Assumptions SIP is used as the protocol AAA is used for Authentication purposes

10. Roles of the SCM Serving. The entity controlling the call, and interacts with the services (Service triggers). This role may be taken by either V-SCM (Visited control) or H-SCM (Home control) Interrogating. The H-SCM is the entity that first receives incoming calls for the user. It is intended to be the fixed entry point, and it will forward the call to the serving entity. Proxy. An entity of the V-SCM that has the task of forwarding requests to the serving entity. May also play a role in e.g. 9-1-1 calls.

11. Schematic Registration call flow part 1 Mobile nodeV-SCMH-SCMAAALAAAH V-SCM Discovery a) b) SIP Registration AAA Msg (SIP Reg) AAA Msg (SIP Reg*) AAAL indicates whether visited control can be supported AAAH authenticates the user and makes a policy decision on whether home or visited control applies V-SCM is discovered e.g using Service Location protocol, or by piggy-backing on lower layers (Mobile IP) Mobile node issues normal SIP Registration message Could possibly go through any number of brokers (AAAB)

12. Schematic Registration call flow part 2a - home control Mobile nodeV-SCMH-SCMAAALAAAH AAA Msg (SIP specific Reply) AAA Msg (SIP specicif Reply) SIP Registration SIP 200 OK SIP 200 OK AAAH assigns a H-SCM for the user, possibly separated into two entities, one in the serving role and one in the Interrogating role (The interrogating entity is typically statically defined) Get Subscriber profile V-SCM is instructed to act in proxy mode Needed to make the H-SCM aware of the proxy location (IP address) Received by the Serving entity LS Update Location Server, so that incoming calls may be redirected to the Serving entity of the H-SCM

13. Mobile nodeV-SCMH-SCMAAALAAAH Schematic Registration call flow part 2b - visited control AAAH makes a policy decision to allow the visited network to take the control, i.e the serving role will be played by the V-SCM. AAA Msg (SIP specicif Reply) AAA Msg (SIP specicif Reply) V-SCM is instructed to act in serving mode AAAL assigns a Serving entity, either by letting the same V-SCM as received the SIP Registration take on this role, or by assigning a new to assigning a new to take on the serving role. LS SIP 200 OK Get Subscriber profile If the server profile has not been cached in AAAL, go back to home for it ! Update Location Server, so that incoming calls may be redirected to the Serving entity of the H-SCM

14. Schematic MN Terminating Call Flow - Home ctrl Mobile nodeV-SCM(proxy)H-SCM (Interrog)H-SCM (Serving)LS SIP Invite Loc Req SIP Invite Call comes in Findout where the user is served (not needed if Interrogating and Serving is one) Call/Session control initiated Message proxied to the mobile node

15. Schematic MN Terminating Call Flow - Visited ctrl Mobile nodeV-SCM(proxy)H-SCM (Interrog)V-SCM (Serving)LS SIP Invite Loc Req SIP Invite Call comes in Findout where the user is served (not needed if Interrogating and Serving is one) Call/Session control initiated This message forwarding if the isn’t any proxy Message proxied to the mobile node

16. Conclusion Using AAA as a means to authorize the user, to provide trust relationships and to do the policy decision on the position of the control within the network is possible and desirable. The NAM should include descriptions on how functionality is distributed, i.e a roaming view of the architecture Propose a new name to the session manager for MMed services to differentiate from the session manager for packet data sessions at the access level that we propose to house in an ACS box.

17. Conclusion (2) Identify a set of support functions needed for all network operations and may for now include AAA, address management, directory functions for storage of local network policies. In the visited network, these functions could be referred to as VSF.