[Kamailio-Users] Relaying NOTIFY UDP messages over TCP

[Daniel-Constantin Mierla]

Hello,

On 03/11/2010 05:58 PM, Iñaki Baz Castillo wrote:
> 2010/3/11 Pascal Maugeri<pascal.maugeri at gmail.com>:
>    
>>> Does such NOTIFY go to a TCP registered user? Of course if there is
>>> not an existing TCP connection between Kamailio and the final natted
>>> user then it's not possible to send such NOTIFY.
>>>
>>>        
>> Do you mean that the user is sending "transport=tcp" in his Contact header ?
>>      
> This must be present in the initial SUBSCRIBE. However if the client
> is behind NAT and uses TCP it's required some way to mantain the
> keepalive in the router, if not a future NOTIFY could not arrive. A
> common approach is the client sending some TCP data through the
> existing connection (i.e.<CRLF><CRLF>  as defined in defat-oubound,
> now RFC XXXX).
>    
I have seen clients sending registration over UDP requiring to be 
contacted via TCP.

To be sure it registers via TCP check the configuration of the phone and 
watch the sip traffic with ngrep (or ethereal) to see the transport 
layer protocol.

Connecting from server to a client behind nat is possible only if you 
have port forwarding on your nat box to phone IP address. Therefore, if 
the phone connects via tcp it must keep the connection open. If for some 
reason it closes, it must re-open it. Otherwise it becomes unreachable.

In the server side there are lot of tcp options to tune the behavior and 
optimize. I do suggest using version 3.0 for a much improved TCP 
architecture and implementation (including asynchronous tcp -- in case 
you deal with lot of tcp connections, then this saves you).
http://www.kamailio.org/dokuwiki/doku.php/core-cookbook:3.0.x#tcp_parameters

Worth to mention as well that you can change the value of tcp parameters 
at runtime without need to restart (e.g., connecting timeout, send 
timeout, etc) using sercmd.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
Kamailio SIP Router Masterclass, Berlin, March 22-26, 2010
* http://www.asipto.com/index.php/sip-router-masterclass/