[OpenSIPS-Users] UDP fragmentation in reply routes

[Olle Frimanson]

Hi,

 

We have an issue on our home proxy (opensips 2.4.6), when it receives  200
OK (over UDP)  from our Freeswitch and the package size is higher than the
MTU size , we sometimes get fragmentation  of the UDP packets, but only the
first part of the fragmented package is sent to our edge proxy. Is this a
known issue or is it a OS bug?

 

We have not yet spotted any pattern on this and in most cases bigger packets
with MTU around 1600 bytes gets through without an issue.

 

I can add that in the other direction in the normal request routes we don't
have any issue at all can have packets > 2000 bytes without any issues.

Does Opensips use IP_MTU_DISCOVER or how is fragmentation controlled and is
it expected to have different behavior in reply routes vs other routes?

We use Centos 7 in a virtual server environment.

 

I was hoping someone can share some light on this strange issue.

 

BR/Olle

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