[ns] How could receivers send NAKs in reliable multicast?

[Bai David <ns_uofa@yahoo.com>]

Hi, there,
   Now I am implementing a reliable multicast protocol
in ns-2.1b5. Could someone tell m how receivers send
NAK packets so that the NAK can be sent back the
source (or reservous point) along the multicast tree
rather than use a different unicast path? What should
I set the source and destination address in NAK
packets?

   Thanks a lot!

David

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