for a particular end-user. This means that even with a priority value of 0, the end-user may receive multicast traffic only; unicast packets might be dropped because the multicast flow overwhelms the LAC forwarding buffer(s).
The default Priority Value is 0. The M-bit MUST be set to 0, and the AVP MAY be hidden (H-bit set to 0 or 1).
There are two ways of using this AVP: global configuration and individual configuration.
6.3.1. Global Configuration
The Multicast Priority Packet AVP is sent for all L2TP unicast sessions concerned with a specific multicast flow represented by an L2TP multicast session. In this case, the AVP is sent in an L2TP MSI control message for the corresponding multicast session ID (Session ID = L2TP session for the corresponding multicast group). The priority value applies to all L2TP unicast sessions to which the multicast group designated by the L2TP multicast session is intended, as soon as this AVP is received.
6.3.2. Individual Configuration
The Multicast Priority Packet AVP is sent for a specific L2TP unicast session that SHALL adopt a specific behavior for both unicast and multicast traffics. In this case, the AVP is sent in an L2TP MSI control message for the L2TP unicast session (Session ID = L2TP session for the concerned user). The priority value applies to the targeted session only and does not affect the other sessions. Note that in this case, all multicast packets carried in L2TP multicast sessions are treated the same way by the LAC for the concerned user.
This is the only case in which an MSI control message can be sent for an L2TP unicast session.
6.3.3. Priority
It is the responsibility of the network administrator to decide which behavior to adopt between global or individual configurations, if the AVP is sent twice (one for a multicast group and one for a specific end-user). By default, only the individual configurations SHOULD be taken into consideration in that case.
Support of the Multicast Packets Priority AVP is optional and SHOULD be configurable by the LAC administrator, if it is relevant.
7. Multicast Session Teardown
An L2TP multicast session should be torn down whenever there are no longer any users interested in receiving the corresponding multicast traffic. A multicast session becomes useless once the related OSL has fewer than a predefined number of entries, this number being
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