SIP Has Its Roots In Multicast Video

Last weekend I read Gonzalo Camarillo’s “SIP Demystified” (McGraw-Hill) as a way to get up to speed with SIP which is the Session Initiation Protocol. I am leading a productization effort here at VBrick to integrate our technology with various Unified Communications solutions including Microsoft’s Office Communications Server.

SIP is commonly known as a signaling protocol used by VOIP and video conferencing. It suggests the SDP format for describing audio and video compression and delivery in the RTP packet format. SIP has been extended to support instant messaging and presence applications. Many believe that SIP will enable a diverse set of products and business processes to be linked together forming a UC framework for digital human communication (voice, video, chat, and collaboration) and machine interactions (greeting visitors in lobbies with automated kiosks, collecting remote instrumentation data, and turning on lamps). There are some detractors who believe that other protocols like H323 may be better suited for video conferencing but SIP is now widely used by the leading UC vendors.

Since I have more experience with streaming than conferencing, I was less familiar with the history of SIP. According to Camarillo, SIP comes from the merger of two related protocols: the Session Invitation Protocol by Mark Handley and Eve Schooler and the Simple Conference Invitation Protocol by Henning Schulzrinne. The latter was used to enable clients to join multicast video broadcasts. Clients would use SIP to request an SDP message that would describe how to join an RTP-based multicast video stream.

I found this to be interesting as I am now brainstorming on how to bring together technologies from VBrick, that has a long history of enabling multicast video broadcasts in the enterprise, with the growing set of unified communications technologies in the marketplace. Broadcasting reliable and high-quality video via standard unicast and multicast protocols has been VBrick’s founding mission. Integrating this capability into a unified communications framework with SIP may be a lot more simple than I had expected since the roots of SIP lay with the same sets of protocols that VBrick has deployed widely for our customers for more than a decade.