Computer Networks · free preview

Multimedia Applications

Moving voice and video over the Internet needs a control plane that telephony always had and data networks lacked, session control protocols locate the callee's current device, negotiate codecs and ports both ends can speak, and set up and tear down calls, the session description protocol conveying media parameters in a standard format while the session initiation protocol does the rendezvous, users addressed by URIs that look like email, proxies routing call invitations toward the callee much as DNS routes lookups, and registrars tracking where each user currently answers, a separation of session control from media transport that lets the real-time flows of the earlier lessons ride whatever path the network offers.