Services in IMS

IMS is an advanced infrastructure enabling services. But the services are in the end points or peers (calls, etc.), not in the IMS.

Application Servers (AS) are the key part to endow IMS with services.

AS offered services enjoy all IMS advantages.

AS interact – using SIP - with the S-CSCF (which controls user’s SIP session).

AS can behave as another SIP proxy or as a SIP UA (terminal).

Where is IMS ?

Basic call flow