3.4.2.1. When not to perform Admission Control
In general, the Access Node and NAS may not be aware of all
possible
multicast groups that will be streamed in the access network. For
instance, it is likely that there will be multicast streams offered
across the Internet. For these unknown streams, performing
bandwidth
admission control may be challenging.
To solve this, these requests could be accepted without performing
Admission Control. This solution works, provided that the network
handles the streams as best effort, so that other streams are not
impacted at times of congestion.
Disabling Admission Control for unknown stream can be achieved by
adding a "catch-all statement" in the Access Node white list or
grey
list. In case the Access Node queries the NAS, the NAS on his turn
will have to accept the request. That way, the unknown streams are
not blocked by default.
Next, in order to ensure that the streams are handled as best
effort,
the flow must be marked as such when entering the service provider
network. This way, whenever congestion occurs somewhere in the
access/aggregation network, this stream will be kicked out
before the
access provider's own premium content.
The above concept is applicable beyond the notion of "Internet
streams" or other unknown streams; it can applied to known
multicast
streams as well. In this case, the Access Node or NAS will accept
the stream even when bandwidth may not be sufficient to support the
stream. This again requires that the stream is marked as best
effort
traffic before entering the access/aggregation network.