When a listener misses a message it requests a retransmission from the sender, which then retransmits the message.  The problem is excessive retransmissions from a problematic receiver can cause issues on other receivers or even network congestion. 

This link talks about it briefly:

http://www.29west.com/docs/THPM/multicast-retransmissions.html

I'm not sure if there is anyway to distinguish a multicast retransmission on the switch and rate limit them or if this is something that HAS to be done in the application itself.

Hi,

This is specific to your multicast application and from the network perspective, the retransmitted packets are the same as the non-retransmitted ones so we can't isolate them. If the source could mark differently (different IP Prec value) the retransmitted packets then you would be able to police them without impacting the regular traffic.

Of course you should also focus on fixing the issue on your problematic receiver.

HTH

Laurent.