Subject: interactive layered video problem (was: Which service class for a scalable flow ?)

From: [email-masked] (Francois Toutain)
Date: Thu, 4 Jul 96 17:22:37 +0200

Hi, thanks for your interest in the interactive layered video problem. Below
are some comments and ideas I'd like to share with you.

There is a clear consensus from your various answers to send the layers
into different flows, although it raises several issues, as it has
been already mentionned (common route, in order setup). We may add the
need for end-systems to merge subbands. Also it is not
clear wether controlled load would be appropriate, due to jitter problems.
Hence guaranteed service seems best suited (arun, jj, Roch).

Comment: the users in my example asked for *best possible quality* (apart
from the baseband). It surprises me they have to use guaranteed service
for something which sounds like a "best-effort" request (OK, I required
real-time service, but...)

What if the various subbands were sent into a single flow ? What are the
issues then ? It seems to me that no current service class would be suited,
but one could imagine a class in which users would make a reservation for
the baseband and then submit actual traffics exceeding the reservation
(i.e. higher layers). Depending on the load, excess traffics could be
discarded. This would require some "priority filtering" mechanisms, so as
to ensure that low bands (at worst, only the baseband) packets be
preferentially serviced.
The reservation could also be tuned to not only guarantee the baseband, but
the few bands that the user consider as minimal acceptable quality.
In addition, consider that such a class could also serve redundantly-encoded
streams with a similar degradation effect.

My feeling is such a service offer could meet many users demands, if the
reward for being prepared to degradation is a low price. Also it is close to
the current Internet "philosophy" of sharing congestion.

Any comment on this ?

How could I get the Van J. SIGCOMM'96 paper ?

Francois

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