[zeromq-dev] QoS / prioritization status
Martin Sustrik
sustrik at 250bpm.com
Fri Jun 24 21:54:26 CEST 2011
Hi Gary,
> 1) Have there been changes/additions in 0MQ since the above thread that
> might provide added support for either 0MQ-level or application-level
> prioritization of messages? (FWIW, I'm OK with some messages getting
> higher priorities than requested, via message-bunching.)
No. No changes in this respect.
> 2) Are there any (related?) 0MQ features or patterns that might help
> optimize message flow through a (known) network bottleneck?
The important point to take into account here is that TCP enforces
strict ordering of data and thus you get head-of-line blocking syndrome
not matter what you do on application level.
That's the reason why 0MQ encourages using different sockets for
different kinds of data, eg. normal vs. urgent.
The receiving application can then poll on 2 sockets, processing
messages from the "urgent" one before anything else.
As for the ToS bits, these are meant to be set by the networking stack.
Having two sockets using different ports allows you to set your
networking hardware and/or networking stack at the endpoints in such a
way that it sets appropriate ToS bits on the urgent feed but not on the
normal feed.
HTH
Martin
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