This Recommendation defines a call control protocol for use in the IP multimedia (IM) core network (CN) subsystem based on the session initiation protocol (SIP)@ and the associated session description protocol (SDP). The Third Generation Partnership Project (3GPP) has developed the specification in a form optimized for the wireless environment. This Recommendation references the ETSI version of the 3GPP specification and specifies only the modifications necessary to optimize it for the cable environment. It is an important objective of this work that interoperability between IPCablecom 2.0 and 3GPP IMS is provided. IPCablecom 2.0 is based upon 3GPP IMS@ but includes additional functionality necessary to meet the requirements of cable operators. Recognizing developing converged solutions for wireless@ wireline and cable@ it is expected that further development of IPCablecom 2.0 will continue to monitor and contribute to IMS developments in 3GPP@ with the aim of alignment of 3GPP IMS and IPCablecom 2.0. Because this Recommendation indicates modifications from the ETSI specification [ETSI TS 124 229]@ the structure of the Recommendation does not follow normal ITU-T practice@ so as to ease the task of the reader to correlate the two documents. The modifications are shown in clause 6.