[SR-Users] Kamailio - passing registration to another sip server

[Klaus Darilion]

Am 25.08.2016 um 16:19 schrieb E. Schmidbauer:
> Hi Matt,
> Check out this post and config: 
> https://blog.voipxswitch.com/2016/08/11/kamailio-and-freeswitch-on-the-same-server-with-nsq-and-jansson-rpc/
>
> It demonstrates how to handle NAT & forward a REGISTER to FreeSWITCH 
> (on localhost)
> Thanks,
> Emmanuel

Just a comment (I found this thread as I currently have the some 
problem). Both provided solutions do use PATH which of course requires 
PATH support on the registrar. If the reigstrar does not support PATH 
then things get complicated.

I see 2 solutions:
a) if the registrar does NAT traversal (and thus always send SIP 
messages to the IP:port it received the REGISTER), does not manipulate 
the received Contact header and the client does not care about 
manipulated Contact header it may be possible by just applying 
"fix_nated_contact()" and route messages from the registrar to the 
client by using the R-URI in the incoming request.

b) if the Contact header must be preserved (strict clients) or if the 
registrar does not apply NAT traversal, then it is necessary to do heavy 
message rewriting and registration in the proxy too:
- the URI in the Contact forwarded to the registrar must point to the proxy
- this URI must be mapped by the proxy to the clients received/NAT address
- depending on the requirements (e.g. multiple registrars, multiple 
domains) the mapping can be simple or complex

Thus, I think a generic solution for registrars without PATH support 
involves plenty of message manipulation and lot of time and testing.

regards
Klaus