User manual

Siqura A-80
Page 38
SAP Settings
The A-80 includes a SAP announcer. The Session Announcement Protocol is used to advertise
that a media stream generated by the A-80 is available at a specific multicast address and port.
For more information about SAP, see the note below.
Advanced section: SAP Settings
SAP Settings
Enable SAP
When selected, session announcements are sent at the frequency determined by
the Announcement interval parameter and the media stream is transmitted to the
multicast IP address specified in the Stream dest. IP address box.
Stream name
Enter a descriptive name to identify the media stream.
Stream dest. IP
Enter the multicast IP address the media stream is to be sent to. The address
must be within the range defined by the Multicast IP range parameter.
Stream dest. port
The destination port number. Default: 1024.
Stream DSCP field
Range: [0…63]. See the note on DSCP.
Multicast TTL
Range: [0...255]. Range: [0...127]. Specify the number of routers (hops) that
multicast traffic is permitted to pass through before expiring on the network.
Announcement interval
Determines the frequency of announcements.
Session scope
Global, the default session scope, sets the Multicast IP range parameter to
224.2.128.0 - 224.2.255.255 (IPv4 global scope sessions). A SAP listening
application will recognize the global scope and automatically listen for SAP
announcements at the 224.2.127.254 multicast IP address.
The Administrative session scope allows you to enter a custom IP range within
the 239.0.0.0 - 239.255.255.255 (IPv4 administrative scope sessions) range. For
an Administrative session scope, the multicast address for SAP announcements
will be set to the highest address in the relevant administrative scope. For
example, for a scope range of 239.16.32.0 - 239.16.33.255, the IP address
239.16.33.255 is used for SAP announcements.
Multicast IP range
See Session scope.
Note on the Session Announcement Protocol (SAP): SAP, defined in RFC 2974 (see RFC 2974 -
http://www.ietf.org/rfc/rfc2974.txt), is a protocol for advertising multicast session information.
A SAP announcer periodically broadcasts announcement packets which include the session
description information of multicast sessions presented by the announcer. SAP uses the Session
Description Protocol (SDP) as the format of the session descriptions. The announcement is
multicast with the same scope as the session it is announcing, ensuring that the recipients of the
announcement are within the scope of the session the announcement describes. SAP listening
applications can listen to the announcements and use the information to construct a guide of all
advertised sessions. This guide can be used to select and start a particular session. The SAP
announcer is not aware of the presence or absence of SAP listeners.