Hello,

if the packets are sent out from Kamailio, check to see in hepic server if they arrive.

The modules in Kamailio do not control the MTU or the UDP fragmentation, the only options are in the core.

Cheers,
Daniel

On 01.07.20 21:48, Andrew Chen wrote:

Hi all,

I've been assigned a task to investigate why hepic doesn't generate MOS scores ever since we changed the kamailio interface MTU from 9001 -> 1500.

During my investigation, this is what I have found out so far:

- Putting MTU back to 9001 removes this condition where no MOS was generated.

- I did a tcpdump of port 9063 which is the port used to send data to Hepic capture server and saw it reports packets are fragmented:

3:48:55.895505 IP (tos 0x68, ttl 64, id 38049, offset 0, flags [+], proto UDP (17), length 1500)
  206.81.181.40.5060 > 10.225.88.239.9063: SIP
13:48:55.896451 IP (tos 0x68, ttl 64, id 38050, offset 0, flags [+], proto UDP (17), length 1500)
  206.81.181.40.5060 > 10.225.88.239.9063: SIP

- Hepic support also caused by using 1500 MTU on the interface.

- I tried using the following core parameters to see if they could remedy this issue but didn't seem to work:

## MTU related core settings

udp4_raw=-1

udp4_raw_mtu=1500

I can't seem to find any parameters in the siptrace module that controls fragmentation of the packets to Hepic.

Any suggestions on how else to troubleshoot this?

Thanks.

--

Andy Chen

Sr. Telephony Lead Engineer

achen@fuze.com

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