2011/6/2 Dmitry Akindinov <[email protected]>:
> A proxy can maintain a list of TCP connections (both incoming and
> outgoing) sorted by their peer ID (IP:port for example). A response
> coming from a fresh TCP connection is a clear indication that the
> original TCP stream is not used any more by UAS, so 1) is most likely to
> fail and should not be tried.
> That original TCP connection should be disposed of and the new (the one
> where the response is received) added to the list.

If a proxy listening in TCP 1.1.1.1:5060 wants to contact destination
1.2.3.4:5060 and there is already an existing TCP connection between
1.2.3.4:48231 and 1.1.1.1:5060, I don't think proxy should assume that
it can reuse this last connection. As I explain below, RFC 5923
explains in which cases this is possible (and current case is not
listed there).


> Then the proxy tries to find an active TCP connection matching the peer
> and sends ACK in it.

But why should the UAS allow the ACK coming from that TCP connection?

Note that, for example, RFC 5923 (Connection Reuse in SIP) states that
a UAC should just accept incoming request within a connection
established by the UAC in case of:
- Transport is TLS.
- UAC announced "alias" in the first request it sent over such connection.

Anyhow the scenario I ask about is totally different but I still think
that RFC 3261 just allows option 2 above. This is, somewhere in RFC
3261 client transaction section there is something like "ACK for
non-2XX final response must be sent to the same destination as the
original INVITE. If it fails then perform procedures in RFC 3263 and
so on...".


Thanks a lot.

-- 
Iñaki Baz Castillo
<[email protected]>

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