SigComp – Signalling Compression
RFC 3320 specifies a protocol on the IETF (Internet Engineering Task Force) standards track that may be used to compress application layer protocols such as SIP (Session Initiation Protocol). In turn SigComp may interface with the three principle transport layer protocols; namely TCP (Transport Control Protocol), UDP (User Datagram Protocol) and SCTP (Stream Control Transmission Protocol). The main driver for the development of SigComp is the planned usage of protocols like SIP which are text based in wireless handsets as part of 2.5G, 3G and 4G cellular networks. Consequently the large message size coupled with relatively low data rates across the radio interface will result in significant transmission delays. SigComp provides a means to eliminate this problem by offering robust, lossless compression of application messages. In SIP SigComp is invoked and negotiated between the client and server. The client initiates the compression mechanism by advertising its ability to employ SigComp through the inclusion of the extension header comp=sigcomp in the request message.
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