Supported Platforms
Configuring the Session Announcement Protocol
Understanding SAP and SDP
Session announcements are handled by two protocols: the Session Announcement Protocol (SAP) and the Session Description Protocol (SDP). These two protocols display multicast session names and correlate the names with multicast traffic.
SDP is a session directory protocol that is used for multimedia sessions. It helps advertise multimedia conference sessions and communicates setup information to participants who want to join the session. SDP simply formats the session description. It does not incorporate a transport protocol. A client commonly uses SDP to announce a conference session by periodically multicasting an announcement packet to a well-known multicast address and port using SAP.
SAP is a session directory announcement protocol that SDP uses as its transport protocol.
For information about supported standards for SAP and SDP, see Supported IP Multicast Protocol Standards.
Configuring the Session Announcement Protocol
The SAP and SDP protocols associate multicast session names with multicast traffic addresses. Only SAP has configuration parameters that users can change. Enabling SAP allows the router to receive announcements about multimedia and other multicast sessions.
Junos OS supports the following SAP and SDP standards:
- RFC 2327, SDP Session Description Protocol
- RFC 2974, Session Announcement Protocol
To enable SAP and the receipt of session announcements, include the sap statement:
You can include this statement at the following hierarchy levels:
- [edit protocols]
- [edit logical-systems logical-system-name protocols]
By default, SAP listens to the address and port 224.2.127.254:9875 for session advertisements. To add other addresses or pairs of address and port, include one or more listen statements.
Sessions established by SDP, SAP's higher-layer protocol, time out after 60 minutes.
To monitor the operation, use the show sap listen command.
