[zeromq-dev] Unreliable multicast was: udp not enabled on Mac OS X 10.6

Martin Sustrik sustrik at 250bpm.com
Fri Mar 5 19:04:48 CET 2010

Martin Lucina wrote:

> Yes, but once you introduce sequence numbers you're going to need a
> handshake to initialise those, which means a "virtual connection" of some
> sort, and if you want to do that using multicast I guess you'll end up with
> something like PGM anyway :-)

No. You need no negotiation. Receiver just has to handle first seqnum it 
sees as beginning of the stream and wait for following packet. Any 
larger seqnum means the stream is disrupted at that point. Any lower 
seqnum means the sender was restarted.

It may cause some hickups when packets are reordered, but that doesn't 
really matter, it's unreliable anyway.

Of course, multiple senders would make a mess.

> I guess the answer depends on what applications Chris has in mind.



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