My 2-3 lines at the end. Daniel Corbe wrote:
>On Mar 8, 2007, at 6:39 PM, Paul Kyzivat wrote: > > > >>Daniel Corbe wrote: >> >> >>>What are you trying to fix? Are you not getting ring indicator >>>tone back from one of your carriers? >>>In practice you shouldn't be generating any provisional responses >>>except for 100 Trying. In the voice world at least this is >>>generally regarded as a bad idea. >>> >>> >>That is a good recommendation for a proxy. It is presumptive to >>make such a statement for a B2BUA. >> >> >> >>>RFC3261 specifically makes no distinction between a proxy and a >>>B2BUA other than this: >>> >>> >> >> >>>6 Definitions >>>Back-to-Back User Agent: A back-to-back user agent (B2BUA) is a >>> logical entity that receives a request and processes it as a >>> user agent server (UAS). In order to determine how the >>>request >>> should be answered, it acts as a user agent client (UAC) and >>> generates requests. Unlike a proxy server, it maintains >>>dialog >>> state and must participate in all requests sent on the >>>dialogs >>> it has established. Since it is a concatenation of a UAC >>>and >>> UAS, no explicit definitions are needed for its behavior. >>>So "proxy" and "b2bua" are very ambiguous. Based on that >>>definition, one would be going out on a limb to say "A B2BUA can >>>do more than a proxy can." >>> >>> >>You make it sound like 3261 considers them to be almost the same >>thing! >> >> > >It does, really. Where does it say otherwise? > > > >>Nothing could be further from the truth. 3261 makes very clear >>distinctions between a Proxy and a UA. A B2BUA *is* a UA, so in >>general you must assume that is how it acts. E.g. if it wants to >>*answer* a call itself, before sending another call out, it can do >>that. >> >> > >Well that's a good point... but in this type of scenario why would >the B2BUA send a 180 and not simply a 200 OK so it can start playing >its media stream? > > > Well, its a B2BUA, so there could be several reasons why it would want to behave in this manner. A typical setup is an IVR system and couple this with (age-old)users who want the system to behave just like the plain old POTS system. Not all are comfortable with changes. And for the Service Provider, a ring doesn't hurt much. Am planning to write a book on the kind of demands that people make with a simple communication system. I'll get rich alrite. cheerz - Ben. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
