questions about multicast

We all know that udp is not reliable,by learning unix network programming I add some hdrs about seq and ts to make udp reliable.the idea is simple.when 开发者_StackOverflowthe receiver receives a packet,it must send a ack packet,there is also something about the round trip time algothrim to estimate the rto.But to multicast,a sender sends a packet to a multicast addr, all host in that multicast group must send a ack packet.Even if the seq is right and acks comes in time,we are still not sure whether all host got the packet,because we don't know the host number.maybe one or more host's ack packet is lost.

I wonder if I can get the number of the host on a specific multicast group or perhaps there is a better idea to make mulitcast reliable.

Try to talk to you network admin and ask him to make your network transmitting reliably. I have 2Gbps multicast all around my network in europe, middle east, asia, north and south america and never lost a single packet - all switches are "voip ready", so this way they automatically internally prioritize the multicast traffic and this is the best way to approach this problem.