Alan Johnston

The Session Initiation Protocol (SIP): An Evolutionary Study

The Session Initiation Protocol (SIP) was devel- oped to control multi-media sessions on the Internet. Shortly after its debut as a standard in 1999, SIP was adopted by the 3rd Generation Partnership Project (3GPP) as the preferred signaling protocol for the Internet Multimedia Subsystem (IMS). This adoption provided a boost to the nascent protocol as traditional telecommunication services were interpreted in the context of the new protocol and as SIP introduced richer services in the form of instant messaging and rich presence to traditional telephony. In this paper, we study the evolution of the protocol from its roots to its use in operational networks today and the issues it faces in such networks. We also provide a glimpse to the continued progression of SIP in Peer-to-Peer (P2P) networks and take a critical look at where SIP has succeeded, and more importantly, where it has failed to meet expectations.