Thanks Dale (sorry to not respond for so long). I've been going through all possible scenarios for the IP address changing during call setup, mid call, and call tear down and this is a much larger problem than I had initially realized. I've been following the "Remote Target on Established Dialog" thread on the SIP email list (and I saw you're following it as well). It's very relevant to this problem.
If anyone else is interested in this problem, check out the thread on the SIP email alias and check out the race condition draft (referenced in that thread): http://tools.ietf.org/html/draft-ietf-sipping-race-examples-04 thanks, Joel On Jan 25, 2008 4:35 PM, <[EMAIL PROTECTED]> wrote: > From: Joel Dodson <[EMAIL PROTECTED]> > > UA1 UA2 > ---------- INVITE ----------> > <---------- 200 OK ---------- > At this point UA2 roams to a different subnet and its IP address > changes. > ---------- ACK ----------> > > The ACK is being sent to the IP address specified in the Contact > header in the 200OK, which is no longer valid. > > Well, the ACK is likely to be very quick after the 200. OTOH, the 200 > might be a minute or more after the INVITE, and the 200 gets to UA1 > based on the address specified in the first Via. (Here we have to > assume that UA1 is mobile in order to make this interesting.) In > theory, you can put a DNS name in a Via header, but I don't know of > any phone that supports that. > > I suppose if the Contact header never contained an IP address this > wouldn't be an issue, but then there has to be a separate network > component that keeps the mapping (Dynamic DNS I guess) to UA2s > current IP address. What about the SDP though? Would you put an > FQDN in the SDP? > > According to RFC 4566, the connection address may be an FQDN. I've > never heard of that being supported, either. > > But maybe there's no better choice -- you can't successfully identify > a network location with an address that has to be updated more > frequently than the updating mechanism makes possible. In SIP, the > worst case is a prolonged INVITE transaction, which can last for > minutes. If your IP address becomes invalid with less warning than > that, you've got to use FQDNs. > > Dale > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
