[zeromq-dev] ZeroMQ behavior in satellite networks (high variable latency)

[Doron Somech]

I'm not sure it is an issue with zeromq, it might be an issue with the
design of TCP and OS tcp stack. You can try the UDP socket, either
radio-dish or dgram sockets.

Which operating system are you using?
You might also try and tweak tcp settings at the OS level and maybe with
some of zeromq options.

More information:
https://tools.ietf.org/html/rfc2488
http://www.emmelmann.org/Library/Papers_Reports/docs/TcpIp_overSatellite/TcpIp_overSatellite.html
https://en.m.wikipedia.org/wiki/TCP_tuning

On Wed, Feb 12, 2020, 22:51 Sylvain Fabre - INPIXAL <
sylvain.fabre at inpixal.com> wrote:

> Hi,
>
> I am using ZeroMQ since more than 6 years now, and the library has proven
> its high efficiency and its stability.
>
> But since a few days, i am facing an issue. Here are the facts :
>
>   - I push video packets on a satellite network, thru a PUSH-PULL pattern,
> associated with a ROUTER-DEALER pattern for the control/command.
>   - The PUSH-PULL pattern is working perfectly well on local LAN, pushing
> 10 streams at 2.0 Mb/sec each without any issue
>   - The satellite network offers "high" bandwidth (approx 30 Mbs), and
> variable latency (let's say between 300 and 900ms)
>   - On the satellite network, it becomes unusable : even 1 single
> PUSH-PULL link is not able to push 2.0 Mb/sec
>
> In order to understand the issue, i simulated the satellite network with
> "netem", on my local LAN :
>
>   - When using a constant latency (ie 700 ms for example), everything is
> working fine (command : tc qdisc add dev eth1 root netem delay 700ms)
>   - But as soon as i use a variable latency, i reproduce the behavior of
> the satellite network (command : tc qdisc add dev eth1 root netem delay
> 900ms 200ms 25% )
>
> Do you know why ZMQ behaves like this ? I guess this is linked to the
> bandwith management, so is there any way to deal with this
> variable-high-latency thing ?
>
> Thanks !
>
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>
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