UA opens a new TCP connection to the SIP proxy. This TCP connection will use a new source port (this is normal for TCP). It will go through NAT again, which will probably assign different public port to this connection. This means connection to proxy will come from a different source port and potentially IP.
Normal SIP operations assume that UA Contact address and port are publicly accessible and typically are different from the port used for outbound TCP connection. Normally there are two TCP connections between the two SIP end-points communicating over TCP. With sip-outbound only one connection is used. BTW, this is a very serious issue. If this is not resolved this makes proxy operation and maintenance a lot harder, since you cannot restart a proxy until all the calls going through it are completed, which will require dialog tracking. ___________________________ Roman Shpount - www.telurix.com On Tue, Aug 24, 2010 at 3:28 PM, Worley, Dale R (Dale) <[email protected]>wrote: > ________________________________________ > From: Roman Shpount [[email protected]] > > 4. A SIP messages for this dialog arrives to this edge proxy. New flow from > UA is very likely to have different source IP and port (and even if ti does > it should not be re-used since it can be a completely different client), so > edge proxy will have no way of knowing that this connection should be used > to communicate with this UA for the dialog. UA is behind NAT, so there is no > way to open a TCP connection from the proxy to UA. > _____________________________ > > Why would the new flow from the UA originate from a different IP? The UA > has not rebooted. > > Although if the UA can no longer use the IP/port that it previously used as > its Contact URI, then of course any dialog that it formed is now > inaccessable. > > Dale > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
