[SR-Users] Handling of packet loss in the Kamailio to RTPEngine control protocol

[Patrick Wakano]

Thanks for the explanation Richard! Much appreciated! Sorry I didn't read
the documentation properly....
I agree the network should be more reliable, but I will investigate if
those parameters can help me.
That's good news about the HTTP and websocket support! Looking forward to
it!

Thank you!
Kind regards!


On Thu, 3 Sep 2020 at 22:34, Richard Fuchs <rfuchs at sipwise.com> wrote:

> On 02/09/2020 19.30, Patrick Wakano wrote:
>
> Hello list,
> Hope you are all well.
>
> Under some load test simulations I've been facing cases where the command
> Kamailio sends to RTPEngine times out with such message:
> send_rtpp_command(): timeout waiting reply for command "" from RTP proxy
> After checking RTPEngine logs, I can see the command was received and a
> reply was sent, so I am thinking the reply packet could have been lost
> somewhere in the network (they are in different servers). So my question
> is, how resilient is the RTPEngine NG protocol to handle packet loss
> situations? I saw TCP is not supported, so are there UDP retransmissions in
> place to guarantee packet delivery? Any ideas to make this connection more
> reliable?
>
> The module automatically resends the command a number of times if no reply
> was received within the timeout period. The modparam `rtpengine_retr` is
> how many times a command is resent, and `rtpengine_tout_ms` is how long it
> waits (in ms) each time for a reply.
>
> If you don't get a reply even after multiple retries, you might have an
> underlying network issue. Most often this is due to broken IP fragmentation
> in the network.
>
> We're currently working on adding HTTP and Websocket support to rtpengine,
> so this could be used in the future as control protocol from Kamailio
> instead of UDP, even though in a properly functioning network there's no
> reason why UDP shouldn't be as reliable as TCP.
>
> Cheers
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