All-IP distributed (proxy) control model architecture

Henrik Basilier, Ericsson

ALLIP-20000717-011__ERI_distributed_CM

Roaming view of the architecture

The inter-operator interfaces, that needs to be defined for purposes ofsupporting roaming subscribers are essential for the overall applicabilityof 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 !

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

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

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.

• 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

ACS

Visited network Home network

BSC+PCF

HA

H-SCM

PDSN

MGW

MGCFMRF T-SGW

R-SGW

IP MMed domain only

AAAL

LDS

AAAH

DS

HA

V-SCM

MGW

MGCF MRFT-SGW

R-SGW

LS

“VSF” “HSS”

Example Call Flows

Call Flows - Assumptions

• SIP is used as the protocol• AAA is used for Authentication purposes

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.

Schematic Registration call flow part 1

Mobile node V-SCM H-SCMAAAL AAAH

V-SCMDiscoverya)

b)

SIPRegistration

AAA Msg(SIP Reg)

AAA Msg(SIP Reg*)

AAAL indicates whether visitedcontrol can be supported

AAAH authenticates the user andmakes a policy decision on whetherhome or visited control applies

V-SCM is discovered e.g using ServiceLocation protocol, or by piggy-backingon lower layers (Mobile IP)

Mobile node issues normal SIP Registration message

Could possibly go through any number of brokers (AAAB)

Schematic Registration call flow part 2a - home control

Mobile node V-SCM H-SCMAAAL AAAH

AAA Msg(SIP specificReply)

AAA Msg(SIP specicifReply)

SIPRegistration

SIP200 OKSIP

200 OK

AAAH assigns a H-SCM for the user, possiblyseparated into two entities, one in the serving roleand 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-SCMaware of the proxy location (IP address)

Received by the Serving entity

LSUpdate Location Server,so that incoming calls may beredirected to the Serving entity of the H-SCM

Mobile node V-SCM H-SCMAAAL AAAH

Schematic Registration call flow part 2b - visited control

AAAH makes a policy decision to allow the visited network to take the control, i.ethe serving role will be played by the V-SCM.AAA Msg

(SIP specicifReply)

AAA Msg(SIP specicifReply)

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 Registrationtake on this role, or by assigning a new to assigning a new to take on the serving role.

LS

SIP200 OK

Get Subscriber profile

If the server profile has not been cached inAAAL, go back to home for it !

Update Location Server,so that incoming calls may beredirected to the Serving entity of the H-SCM

Schematic MN TerminatingCall Flow - Home ctrl

Mobile node V-SCM(proxy) H-SCM (Interrog)H-SCM (Serving) LS

SIP Invite

Loc Req

SIP Invite

SIP Invite

SIP Invite

Call comes in

Findout where the useris served (not needed if Interrogating and Serving is one)

Call/Session controlinitiated

Message proxied tothe mobile node

Schematic MN TerminatingCall Flow - Visited ctrl

Mobile node V-SCM(proxy) H-SCM (Interrog)V-SCM (Serving) LS

SIP Invite

Loc Req

SIP Invite

SIP Invite

SIP Invite

Call comes in

Findout where the useris served (not needed if Interrogating and Serving is one)

Call/Session controlinitiated

This message forwardingif the isn’t any proxy

Message proxied tothe mobile node

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.

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.