Session Announcement Protocol

The Session Announcement Protocol (SAP) is a network protocol in the field of IP telephony, which supports multicast multimedia sessions and other multicast sessions and the corresponding session configuration passes to eligible participants. It was developed by the IETF and described in RFC 2974.

Principle of operation

The SAP announcer periodically sends this announcement packets to the well-known ( "well known " ) multicast address ( sap.mcast.net = 224.2.127.254 ) on the corresponding port (default: 9875 ). The SAP client listens on this port to recognize and accept any requests for multicast sessions.

Development of a SAP packet

  • V - 3 bits - version number must be set to 1
  • A - 1 bit - Address Type can be 0 or 1 0 - Originating Source field contains IPv4 address (32 bits)
  • 1 - Originating Source field contains the IPv6 address (128 bits)
  • 0 - packet announcing a meeting
  • 1 - package to delete a session
  • 0 - the payload is not encrypted, the timeout field may be missing
  • 1 - The payload is encrypted, the time-out field must be added to the header
Internet Engineering Task Force Client (computing) Internet Media Type Session Initiation Protocol Session Description Protocol
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