For transferring voice, video, or multimedia, we need perform two functions. The first one is to carry the media stream, which is mostly voice or video, and the second one is for signaling, which is to establish and terminate the call, to invite participants to the call, and so on. Two protocol suites were proposed over the years for signaling:
- The ITU-T suite of protocols, including H.323 as an umbrella protocol for the suite, H.225 for registration and address resolution, H.245 for control, and some others
- The IETF suite of protocols, including SIP as a signaling protocol (RFC 3261 with later updates) and Session Description Protocol (SDP) to describe the session parameters (RFC 4566)
The ITU-T set of protocols phased out in the last few years, and the majority of the applications today are using the IETF set of protocols, which we will be focusing on in this...
