[zeromq-dev] epgm protocol question

Steven McCoy steven.mccoy at miru.hk
Tue Apr 13 15:29:28 CEST 2010


On 13 April 2010 21:11, Martin Sustrik <sustrik at 250bpm.com> wrote:

> However, my guess is that you are simply pushing data to the socket as
> fast as possible. That way you are going to saturate the rate however
> high you set it. In such case you are guaranteed your network won't be
> overflowed (max is 20Mb/s) but you experience messages lost as there's
> no spare rate available for RDATA.
>
> In theory, the rate could be spread between RDATA and ODATA (maybe two
> different rate limits) but again: how would you establish the ratio?
>
>
SmartPGM has an additional option to set either ODATA or RDATA as
uncontrolled rate, but you cannot specify two independent rates.  So for
instance you could say ODATA is 20mb/s and have RDATA unleashed to murder
your network.

The most sensible if arduous option would be to implement a coarse rate
limit in your application feeding ØMQ.  Consider that the PGM rate limit is
to protect the network, it is up to your application above ØMQ to make the
most out of provided channel.

The extra care is needed, compared with TCP, is because OpenPGM does not
have a congestion control implementation and is currently design for the
case that you don't want crybaby receivers slowing or halting the broadcast
for the entire network.

-- 
Steve-o
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