This chapter describes Request for Comments (RFC) 3485 that deals with the compression support in Session Description Protocol (SDP) and Session Initiation Protocol (SIP). The SDP is a text-based protocol intended for describing multimedia sessions and may carry files like Multipurpose Internet Mail Extensions and others. The call control protocols like SIP (see Section 1.2) or web real-time communication (see Section 1.3) that uses SDP for session negotiations between the conferencing parties is also a text-based protocol. In a combination of SDP and call control protocol, the bandwidth may be a problem to carry the signaling traffic, especially in resource-constraints wireless networks. RFC 3485 specifies the SIP/SDP-specific static dictionary that the signaling compression scheme defined in RFC 3320 may use in order to achieve higher bandwidth efficiency as well as better response time for the call setup. The dictionary is compression algorithm independent.