RAMDEV SHARMA : IP M ULTIMEDIA S UBSYSTEM

This layer has two sub layers namely the Application layer and service capability layer. This is where the Application Servers (AS) are resident. This is where all of the services are delivered through the IMS interface into the Session Control layer through the SIP protocol. There are a few different types of Application Servers defined, including the ENIP AS, SIP AS, CSI AS, HO AS, OSA-GW, Info-x GMPS and IM-SSF.

The SIP AS is a future IMS Application Server and it is anticipated that most of the new services developed for IMS will be built on this type of server. The OSA is defined to interface with legacy application servers such as the Open Service Access framework servers and CAMEL (Customized Applications for Mobile network Enhanced Logic).