Hi Alex
There are lots of strategies for reducing message size, although the RFC-recommended (better said, mandated :-) approach is just to switch to TCP whenever your message sizes come within 200 bytes of the MTU, if I'm not mistaken.
Those CPE do not support TCP.
Otherwise:
- Turn on compact (abbreviated) SIP headers;
I would love to do that. But can I somehow instruct kamailio to translate all headers to their compact format?
- Strip header fields you can do without. This is dangerous territory, but clearly some headers are less important than others, like "Date" or "Allow";
Done that, removed User-Agent and some more. Still not enough if there are 5 or more Via and RR header.
- Do not offer any unnecessary codecs, reducing SDP bloat.
The message body is not the issue, this seems to be handled in a different memory buffer. The CPE crashed with a 'memory buffer too small' when composing the reply to an invite with 5 or more Via and RR even with minimalistic SDP. On the other hand, I threw a huge SDP with ICE and Crypto to that CPE and it handled it well when only one Via and no RR was present (after being handled by topos).
Mit freundlichen Grüssen
-Benoît Panizzon-