Hi again, I've thought about this more and there seem to be a number of potential race conditions. Here's the most basic one (UA1 is a fixed server while UA2 can roam across subnets, causing its IP address to change): 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 The ACK is being sent to the IP address specified in the Contact header in the 200OK, which is no longer valid.
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? Once the call is fully established we can re-register the device and use UPDATE to renegotiate the SDP. Call setup seems to be very problematic. At this point we're planning on simply terminating the call as best we can, re-register and try the call again. I'm curious if others have solved this problem more elegantly, or, more hopefully, I'm overlooking something very basic. thanks, Joel ----- Original Message ---- From: Joel Dodson <[EMAIL PROTECTED]> To: SIP Implementors <[email protected]> Sent: Wednesday, January 23, 2008 2:28:50 PM Subject: subnet roaming in a wireless network Hi all, I thought I had seen a draft discussing how a SIP endpoint ought to behave when roaming between subnets in a wirless network, but I can't find any references. Is there anything documented for that? I'm thinking of something like RFC 3725, best current practices for 3PCC. Maybe a best current practices for wireless networks and subnet roaming. In general, when the endpoint's IP address changes, it could use re-INVITE/UPDATE to change the session parameters (if it's in a call) and REGISTER again to update its AOR binding. Those are the most obvious actions to take. I didn't see anything in the SIP, SIPPING, or SIIMPLE charters discussing mobility, wireless, or roaming. Is there better place to be looking? thanks, Joel ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
