[OpenSIPS-Users] Why does NAT keepalive only work for UDP?

Dan Pascu dan at ag-projects.com
Wed Nov 12 11:00:59 CET 2008

Man, you have a lot of questions today... :P

On Wednesday 12 November 2008, Iñaki Baz Castillo wrote:
> Hi, I wonder why SIP keepalive method (sending a NOTIFY/OPTIONS
> perdiodically) just works for UDP, this is: why the request is not sent
> via TCP?

Mainly I guess it's because nobody did implement it, as none had a need 
for it yet? Add to that that the TCP stack is handled differently (inside 
opensips) and it's a complex beast which is not easy to tap into as it is 
with UDP. Also, I guess historical reasons was also a factor as it was 
meant as an improved replacement for the (UDP only) solutions in the 
nathelper and mediaproxy modules (which it is). While being improved it 
doesn't imply it has to be perfect, so if you need TCP support, you are 
wellcome to implement it and share it with us ;)


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