[Spce-user] UDP packet size

Andreas Granig agranig at sipwise.com
Wed Mar 5 07:55:03 EST 2014


Please keep the list in CC for any non-privacy-critical things, we're
not doing private email support.

Alright, the second INVITE indeed exceeds typical MTU sizes (usually
1400 byte, you're at 1540) according to your client log:

On 03/05/2014 01:42 PM, Nikita Stashkov wrote:
> channel [0x2d3d000]: message sent to [UDP://sipmobile.org:5060], size: [1540] bytes

Does this happen only on a particular network? If so, I guess you have a
faulty SoHo router/firewall, which drops the second part of the
fragmented UDP package of the INVITE message, so the Linux kernel on the
SPCE is unable to re-assemble the package.

If it happens anywere, then you should check your network in front of
your SPCE, maybe there is some kind of firewall or something.

I'm 100% sure it's a network issue, as it starts working if you remove
some codes, making the overall packet smaller (<1400 bytes) and it
doesn't get fragmented. I've seen this issue with dropped UDP fragments
a lot of times already, both in residential routers (wifi routers of
some sort) and in carrier grade firewalls.


More information about the Spce-user mailing list