[zeromq-dev] Is UDP transport needed in ZeroMQ?

Wojtek Sliwinski wojciech.sliwinski at cern.ch
Tue Dec 31 09:59:26 CET 2013


Yes, definitely UDP transport would be a major added value.

For many industrial & control systems, UDP is the solution when we talk
about:
- high frequency (>50Hz) messaging
- scalability: minimal load & use of resources on publisher's side
- some messages may be lost but usually the last one only counts

Publisher runs often on an embedded OS, with 1CPU & limited memory.
Using decent network infrastructure and well configured OS, together with
DSCP bits set for QoS,
we could achieve very good performance, which was not possible with
TCP-based approach.
Moreover, for our case, some measurements showed that UDP was in fact very
reliable with the loss rate of max. ~1%

This approach is used at CERN for the closed-feedback control system,
where many nodes (~2k) send data
to a central service and later on, after the calculations, get back new
control values.

I imagine that many frameworks have built an abstraction layer over ZeroMQ
in order to hide
the details of the communication layer. Having support for UDP transport,
would allow for 
a huge code reuse & seamless use of tcp & udp endpoints via the common API.

We can help in testing of the new extension.

Regards,
Wojtek

>Date: Fri, 27 Dec 2013 15:56:15 +0100
>From: Arnaud Loonstra <arnaud at sphaero.org>
>Subject: Re: [zeromq-dev] Is UDP transport needed in ZeroMQ?
>To: ZeroMQ development list <zeromq-dev at lists.zeromq.org>
>Message-ID: <52BD950F.3070607 at sphaero.org>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>On 12/25/2013 04:08 PM, crocket wrote:
>>Recent mailing list messages seem to revolve around UDP transport.
>>
>>It seems people need UDP transport in ZeroMQ.
>>
>>Since people seem to need it and the task of adding udp looks
>>interesting, it would be a good time for me to learn the internals of
>>libzmq and step in to build udp:// into it, however most of my time is
>>tied to my current job now.
>>
>>Is it actually needed? If so, does anyone else plan to do it in near
>>future?
>
>I've also been looking into UDP. In my scenarios usually low latency is
>more important than reliability. (e.g. OSC controlled instruments, MIDI
>setups, ArtNET controlled lights) UDP is almost always the choice then.
>I've been using 0mq for a while now and I really really like it but I
>foresee I will need to revert to UDP again once TCP gets in the way.
>
>Rg,
>
>Arnaud




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