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

[Iñaki Baz Castillo]

2008/11/12 Klaus Darilion <klaus.mailinglists at pernau.at>:

>> So I understand that the server doesn't close the connection before
>> registration expires, but how can the client know it? why would a client
>> mantain the TCP connection open until "expires" time? why to expect it?
>
> Because it is the only way the receive messages if the client is behind NAT.

Yes, but where is specified (I mean before outbound draft) that the
caller must mantain the TCP connection open?
Yes, it makes sense but...


> If you are behind NAT there is no way for the
> server to make a TCP connection to the client. So, if the client is behind
> NAT and tears down the TCP connection it is a damn stupid client.

Sure, but anyway, why the server/proxy couldn't send periodical
NOTIFY/OPTIONS to mantain NAT open (in case the clients doesn't it)?
Well, if we think in UDP, a client could also send periodical
NOTIFY/OPTIONS to the server to mantain the "connection" open (but
it's not very usual), why a client should care about it just in case
of using TCP?


Regards.


-- 
Iñaki Baz Castillo
<ibc at aliax.net>