[zeromq-dev] EPGM packets

Martin Lucina martin at lucina.net
Fri Feb 3 12:27:38 CET 2012

sustrik at 250bpm.com said:
> Hi Matteo,
> > we just switched our PUB/SUB architecture on 0MQ from TCP to EPGM to
> > reduce traffic and get over the need for a central repeater to have
> > multiple publisher/multiple subscribers.
> > I tcpdump'ed the traffic to see what was going on, but I can only see
> > repeated multicast messages from the publisher, but nothing from the
> > subscribers. Is that normal? Is that because of UDP encapsulation?
> Yes. It's normal. Subscribers complain only if there's packet loss on 
> the network.
> For more details check RFC 3208

Specifically, subscribers send NAKs back via unicast to the publisher.

Therefore, if you run tcpdump on the publisher, you should see that


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