[zeromq-dev] 0MQ experimental OpenPGM support

Martin Sustrik sustrik at fastmq.com
Tue Jan 20 16:37:31 CET 2009

Pieter Hintjens wrote:
> On Tue, Jan 20, 2009 at 4:26 PM, Pavol Malosek <malosek at fastmq.com> wrote:
>> Maybe you have noticed that we have added multicast support into 0MQ trunk,
> Nice!
> What level of reliability does this give compared to TCP?

The difference is that PGM tx window is rolling on with every message 
you send - thus, if consumer requests retransmission of a packet that 
was already rolled out of the window "connection" breaks. With TCP 
sender will be blocked when tx window is full. In other words, PGM is 
somehow less reliable than TCP.

PGM = "pretty good multicast" rather than "perfectly reliable multicast" :)


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