[Freeswitch-users] FW: FS injecting packets - what are they and how do I stop them?

[Nathan Downes]

Nobody got a clue? Surely someone has seen this!


From: FreeSWITCH-users [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Nathan Downes
Sent: Wednesday, 8 November 2017 7:12 PM
To: freeswitch-users at lists.freeswitch.org
Subject: [Freeswitch-users] FS injecting packets - what are they and how do I stop them?

Hi guys,

So I have an onsite FS at a clients, and we send calls to it from another FS.

Provider -> FS1 -> FS2 -> phone

Occasionaly there is a small amount of jitter on these certain trunks, FS1 passes it through normally, FS2 appears to add its own packets in to the stream to fill the gaps which have the incorrect timestamp that jumps around, this plays havoc with certain phones (T4 series Yealinks, T2 series, Polycom)

Stream from FS1 to FS2 looks like below

[cid:image001.png at 01D358C3.F1C54260]
Can see a few missed packets around the Mark bit

FS2 then send this to the phone

[cid:image002.png at 01D358C5.30BF2070]


It is filling in the missing packets with wrong timestamps and a payload containing just 55555555555555555555555555555555555555555555's

Certain Yealink phones freak out with the timestamp jumping around (confirmed by Yealink support) but this has little effect on a Cisco or T5 series Yealinks.  We would get a 2 second gap of audio from the above when it is only 200ms or so.

What exactly are these packets? And how can I stop FS2 generating them?  From memory FS2 is latest Debian stable packages. I have tried every combination of all variables that I feel may have an effect on this but am getting nowhere fast (CNG/VAD/RTP bugs etc)

We tried rewriting timestamps and that solves the gaps in audio, but then the jitter is much more noticeable as the jitter buffer on phone can't tell anything is going on because the timestamps are perfect.

FS1 is much older 1.4.23 and doesn't exhibit the same behaviour when phone is direct connected to it.

Thanks,

Nathan
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