Summary: cast rates greater than about 0.4 per output port, since at that rate
the multicast queues themselves become unstable.
While more efficient multicast scheduling could reduce the
space available to unicast, we nevertheless expect the gains to
remain significant. In particular, owing to the hardness of the
multicast problem, we expect most multicast algorithms to allow
substantial scope for unicast integration.
In this paper we consider two problems related to the schedul
ing of multicast packets in an inputqueued switch. We first as
sume that the multicast schedule is given and we present algo
rithms for scheduling unicast traffic on the idle ports. We be
lieve that this is especially important in view of our later results
which show that multicast scheduling is a hard problem. With
any practical multicast scheduling algorithm there are likely to
be many ``holes'' in the schedule where extra unicast cells can be
``squeezed'' in. Our experimental results support this conclusion.
We also present a new analysis of the multicast scheduling prob
lem when fanoutsplitting is allowed.
One important problem for further work is to try to reduce the