[sr-dev] why new tcp connection?

Klaus Darilion klaus.mailinglists at pernau.at
Mon Nov 9 12:10:56 CET 2009

Iñaki Baz Castillo schrieb:
> El Sábado, 7 de Noviembre de 2009, Olle E. Johansson escribió:
>>> However, the fact is that during a TCP dialog there "should" exist
>>> *two* TCP
>>> connections (assuming binding port = 5060):
>>> a) UA:random_port - Proxy:5060
>>> b) Proxy:random_port - UA:5060
>>> If UA initiates the dialog the connection a) is created.
>>> If Proxy sends an in-dialog request the connection b) is created.
>>> Of course b) is not created when using "alias" or forcing the proxy
>>> to reuse
>>> the connection established by UA (server solution).
>> Imaging having TLS. The B connection would not work unless we had a
>> valid certificate in the UA.
>> For TLS each TCP connection needs a property on when it's allowed to
>> reuse.
> Annoying. Let me a question:
> If UA is not behind NAT (but supports and uses sip-outbound), how many TCP 
> connections would exist when communicating with the proxy?

since October 2009: 1


> PS: I insinst. How is possible that IETF has designed a protocol in which, by 
> default, two TCP connections are required in a direct communication between A 
> and B?

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