Service layer in IMS

[sukishan]

Service layer in IMS
The service layer of an IMS architecture provides multimedia services to the overall IMS network. This layer contains network elements which connect to the Serving-CSCF (Call Session Control Function) using the IP multimedia Subsystem Service Control Interface (ISC)[2]. The ISC interface uses the SIP signalling protocol.

Elements of the IMS service layer
The network elements contained with in the service layer are generically referred to as 'service platforms' however the 3GPP specification (3GPP TS 23.228 V8.7.0) defines several types of service platforms:

SIP Application Server
OSA Service Capability Server

IM-SSF
SIP Application Server
The SIP Application Server (AS) performs the same function as a Telephony Application Server in a pre-IMS network, however it is specifically tailored to support the SIP signalling protocol for use in an IMS network.


OSA Service Capability Server
An OSA Service Capability Server acts as a secure gateway between the IMS network and an application which runs upon the Open Services Architecture (this is typically a SIP to Parlay gateway)


IM-SSF
The IM-SSF (IP Multimedia Service Switching Function) acts as a gateway between the IMS network and application servers using other telecommunication signalling standards such as INAP and CAMEL.

[dhoni]

the service layer in ims should be used in many ways
there are many service layer should explain on it