Using SigComp to compress SIP/SDP messages

SIP and SDP are used in 3G cellular IP multimedia subsystems (IMS) to perform multimedia session setup and maintenance. However, both protocols are text-based and have large messages with sizes frequently exceeding several hundred bytes. SigComp can be used to compress these messages and greatly reduce the call setup and feature invocation delays. In this paper, the potential gain of using SigComp to compress SIP/SDP is demonstrated through performance results. Our results show that dictionary-based compression algorithms are best suited for SigComp. Static and user-defined dictionaries are very important for reducing the first several messages in a SIP dialog while extended operations such as dynamic and shared compression can significantly improve the overall compression efficiency. On average, the message sizes can be reduced by as much as 88% with negligible compression/decompression time.