[zeromq-dev] PGM: multiple listener behavior?

Steven McCoy steven.mccoy at miru.hk
Wed Aug 8 16:59:38 CEST 2012

On 7 August 2012 13:33, Stuart Levy <salevy at illinois.edu> wrote:

>  Thanks - could you explain a bit more?   In the
> PUB+SUB-on-same-port-on-same-host situation Pierre described - which
> applies to me too - *all* NAKs will be lost, not just some small fraction
> of them, if the SUB socket gets opened before PUB, IIUC.   Does that imply
> that recovery can never happen, regardless of rate limiting, etc.?   I
> don't want the loss of a single multicast packet to mean that the whole
> system will need to be restarted...

With multiple senders on the same host on the same PGM session only the
first will receive NAKs due to unicast routing.  It's an OS and protocol
design feature.

I believe with 0MQ only one PGM publisher should ever be active on the
network: a bus topology is not supported by the 0MQ socket.  This is
probably the more pertinent issue that voids a lot of the previous

> If so, then I don't see how I can use zeromq multicast to create a barrier
> primitive - that I'd be better off just doing all the low-level networking
> myself.  That's a pity, if true.

Need a bit more clarification on what you are looking for?  Atomic
multicast?  I think there was a brief mention about this previously.

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