CALL FORWARDING IN AN IP MULTIMEDIA SUBSYSTEM (IMS)

摘要

A method and Serving Call/State Control Function (S-CSCF) for handling a Session Initiation Protocol (SIP) communication within an IP Multimedia Subsystem (IMS), wherein the communication is subject to a call-forwarding operation handled by a SIP Application Server (AS). An INVITE is received at the S-CSCF, which serves a user equipment (UE) identified by an R-URI. The S-CSCF adds a URI for the S-CSCF to the INVITE route header together with an Original Dialog Identifier (ODI) mapped to the R-URI. The S-CSCF forwards the INVITE to the AS, which changes the R-URI to a URI of a UE to which the call is to be forwarded. The AS adds a forwarding indicator to the INVITE and returns it to the S-CSCF. The S-CSCF identifies the forwarding indicator and determines the original R-URI based on the ODI received in the returned INVITE. The S-CSCF determines call restrictions and Initial Filter Criteria (IFCs) based on the original R-URI.