Congestion Avoidance in S-CSCF Selection in an IMS Network

In the signaling plane of an IMS (IP Multimedia Subsystem) network, the Interrogating Call/Session Control Function (I-CSCF) is required to choose the serving CSCF (SCSCF) for user requests arriving at the Proxy CSCFs (P-CSCF). This requires S-CSCF selection in such a way that the response time is minimized. However, in an overloaded situation, the PCSCF entry points for arriving requests must balance between rejecting new requests and having an acceptable response time from S-CSCF for those that are allowed to enter.