On Apr 14, 2008, at 11:22 PM, Francois Audet wrote: > You are making this more complicated than it is. See below. > > > On Apr14 2008 20:08 , "Dean Willis" <[EMAIL PROTECTED]> wrote: > >> I really can't see how; I can't make it work with my providers >> >> Let's revisit the problem again: >> >> Alice is a customer of provider A. Bob is a customer of provider B. >> >> Alice calls Bob. Bob wishes to forward her call to Jenny's telephone >> number, +445558675309. >> >> At this point, Bob and provider B don't know what gateway Alice might >> use to reach the PSTN, They also don't know whether reaching Jenny's >> phone number even requires Alice to use a gateway. >> >> What does Bob put into the Contact of a 302 he might send to Alice? >> >> I've heard several alternatives: >> >> 1) sip:+445588675309:b.com >> >> 2) sip:+445588675309:b.com; user=phone >> >> 3) sip:+445588675309:a.com >> >> 4) sip:+445588675309:b.com;user=phone >> >> 5) tel:+445588675309 >
Yes, I meant "@", > Bob would typically put 2, (assuming you meant > sip:[EMAIL PROTECTED];user=phone) despite the fact that 5 would be > more > appropriate. But this one is fairly certain not to work. > If B.com is not the cheapest crappiest service provider or enterprise > possible, it will then recurse on it's own PSTN gateway and route > the call > there. Try this experiment: Fire up your Gizmo account, and have the registered UA return a 302 to a Contact of sip:[EMAIL PROTECTED] " . Now call "sip:[EMAIL PROTECTED]" (or whatever your Gizmo ID is) from a phone that doesn't have Gizmo credentials and see if they let you make a free phone call to the PSTN. Hint: They don't. > > > I guess in theory, it's possible that it would pass the 302 back. If > it did > do this, then I would think that it should make the 302 usable by > a.com. > Passing a b.com might work (although it would probably have recursed > on it > already). If it doesn't have a gateway, then I guess it could change > it to a > Tel URI (which might then fail) or even substitute the domain with > a.com and > let a.com deal with it (which it may or may not). Fact is, there is > no free > lunch. > > In any case, I think 2 is the most likely. > > Now, if we want a service where you want Alice to be responsible for > figuring out "how to get to the PSNT", then yeah, I think the Tel > URI is > better (but it may not work today in practice unfortunately, in > which case > Alice's Proxy would have to B2BUA it and much around with the > contact, which > would break 4474, yadi yada). You make a mistake in assuming that a phone number means that Alice has to figure out how to get to the PSTN. She doesn't -- she needs to figure out how to get to the target specified by the phone number, which might or might not be on the Internet as well as the PSTN. further, she needs to figure out the "best" (and that's a local policy question) to get there, and answering this question might involve choosing between multiple gateways and connecting directly over the Internet. It might even require something as complex as starting up a VPN in order to get a connection to a corporate gateway. There is no way that the domain of the target can make this decision for her, unless the domain of the target is picking up the cost (the PSTN gateway charge) for doing so, in which a proxy-retargeting operation is arguably a better approach than a 302 response. -- Dean _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
