[ANCP] Multicast Admission Control issues.

[<peter.naveen at wipro.com>]

Hi,

The protocol defined in draft-maglione-ancp-mcast-00.txt may not scale
well for multiple flows per Access Port.

There exists a scenario where the user (behind the Access Port) can
request for a new channel when the first channel is still being streamed
on his Access Port, that is, a join is sent by the user for the 2nd flow
without leave being sent for the 1st flow. As per the draft, AN will
honor the 2nd flow as that flow group was already
authorized/authenticated by the NAS, when Admission Request was sent for
the 1st flow (by AN to NAS) for the 1st flow of that flow group. This
will cause issues if sum of the bandwidth demanded by 1st and 2nd flow
exceeds the DSL synch up rate of the Access Port.

A similar issue might exist with White list configuration as well. As
per the draft, AN does not need to consult with NAS for channels listed
in white list. In this case, 

   * The bandwidth demanded by a channel in White list may be more than
the DSL sync up rate on the Access Port.
   * The sum of the bandwidth demanded by the 1st and subsequent White
list channels on an Access Port may be more than the DSL sync up rate on
the Access Port.

In both the scenarios, explained above, NAS is not aware of the Access
Port bandwidth used by,
  * White list channels Joined.
  * 2nd and subsequent flows (of an already authenticated Flow group)
Joined.

NOTE: The protocol seems to address only the "Conditional Access"
requirement but not the "Admission control" for multiple flows. Also the
"Multicast Accounting" requirement for "Joins of White list channels"
and "Joins of 2nd and subsequent flows of a flow group" are not
addressed, as there is no NAS-AN communication for these cases.

Regards,
Peter



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