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I am running a small network of 5 3350-48 SMI switches trunked to a 3550-12G
running EMI. There is no layer 2 redundancy but the 12G routes between the
two main data VLANS. There is also a voice vlan in the network.

When I run multicast video streams (8mbit mpeg) I am running into QOS
issues. If the sender and receiver is on the same switch, I get good
performance. When the sender/receiver are on different switches but the same
vlan I get picture and sound quality issues. Skipping, occasional dropouts,
etc.

When the sender/receiver are on a different vlan on different switches, I
get poorer performance again.

No packets are dropped at layer 2. The links are not flooded. In fact they
show exactly what you would expect. Around 8% utilisation for the access
ports and hardly anything on the trunks. CPU also seems fine.

Does this sound like a QOS issue? Would I solve it via queuing or policy
maps? I need to take the next step in troubleshooting and I am finding
resources lacking..

thanks

Paul