RE: [Sipping] comments on draft-roach-sipping-callcomp-bfcp-00
"Elwell, John" <john.elwell@siemens.com> Fri, 03 November 2006 14:49 UTC
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Date: Fri, 03 Nov 2006 14:46:56 +0000
From: "Elwell, John" <john.elwell@siemens.com>
Subject: RE: [Sipping] comments on draft-roach-sipping-callcomp-bfcp-00
To: "Huelsemann, Martin" <Martin.Huelsemann@t-com.net>, sipping@ietf.org
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Martin, Thanks for preparing these examples. Concerning the point about managing without GRUU/GRID for call completion calls that come in via a different MGC, how exactly would this work? By the way, I am not sure if it has already been mentioned in this context, but GRID is no longer part of GRUU. John > -----Original Message----- > From: Huelsemann, Martin [mailto:Martin.Huelsemann@t-com.net] > Sent: 03 November 2006 12:52 > To: sipping@ietf.org > Cc: adam@nostrum.com > Subject: AW: [Sipping] comments on > draft-roach-sipping-callcomp-bfcp-00 > > > Hi, > > I have drawn two basic flows for a PSTN interworking, available at > http://www.softarmor.com/sipping/drafts/Roach%20Call%20Complet > ion%20interworking.pdf. > I think they show an interwoking according to Adams proposal, > Adam please correct me if I'm wrong. > > The interworking itself seems to be feasible to me, but > looking at the flow where CCBS is invoked in the PSTN, I > share Johns concern that the call completion INVITE (or > respectivly the IAM with the call completion indication) has > to be routed exactly via that MGC that has the function of > the BFCP client and that handles that specific GRUU/GRID > instance, and it's not determinstic that this will be the > case in the PSTN as far as I know. > It has to be that particular MGC, because only this MGC knows > the GRUU/GRID and could interwork it because of the IAM > Calling Party Number and CCSS indication. > > So at least from a PSTN point of view there would be an > advantage if the call completion call could be handled > independently from a specific GRUU/GRID, perhaps as a kind of > fallback mechanism for an interworking with networks that > don't support GRUU. > > > > Regards, Martin > > > > > > > > > > > -----Ursprüngliche Nachricht----- > > Von: Adam Roach [mailto:adam@nostrum.com] > > Gesendet: Donnerstag, 2. November 2006 16:43 > > An: Jonathan Rosenberg > > Cc: IETF Sipping List > > Betreff: Re: [Sipping] comments on > > draft-roach-sipping-callcomp-bfcp-00 > > > > > > Jonathan Rosenberg wrote: > > > Its not clear to me that this mechanism works well in the face of > > > forking. Seems like you could end up with disparate queues > > for each of > > > my phones. > > > > That's pretty much what I intended, yes. As far as I can > > tell, the net > > result -- that is, the behavior of the system -- would end up being > > identical (or, at least, substantially the same) with queues > > maintained > > on each of your devices versus a single, centralized queue > -- unless > > there's more than one of you, in which case neither solution > > will behave > > particularly gracefully (although I believe the forking setup > > has better > > recovery properties under such circumstances). > > > > When I get a spare moment, I'll work through a few scenarios to > > demonstrate how the externally observed system behavior is the same > > between distributed management of several queues and centralized > > management of one queue. > > > > > Similar issues arise when the originating user has multiple > > devices. > > > So if I call you from phone 1, and later you are available, > > does the > > > ringback happen only at phone 1 or all of my phones? > Seems like the > > > latter is much more desirable. That too implies that a UA-based > > > solution on the originating side has some problems. > > > > That depends. Are you asserting this as a new requirement? > No one has > > raised this capability as a requirement so far, and the previously > > offered solution certainly didn't have this property. > > > > To be clear: I agree that this is probably an improvement on the > > service; however, the more requirements we pile on, the harder a > > solution becomes -- and we've become experts at putting so many > > requirements on a problem that the solution space dwindles > > down to nothing. > > > > > There is clearly a relationship between all of this and > presence; I > > > think you need to call that out. > > > > Martin beat me to it, but I'll reiterate his comment: the > > relationship > > here isn't related as much to presence as it is to dialog > state. And > > that is called out in the discussion about centralized queue > > management. > > > > > On whether BFCP is the right thing or not for this > problem, I'm not > > > sure. In one sense, you could characterize this as really > a problem > > > with RFC3265 in general; that for certain event packages, > > notification > > > of an event to all watchers can cause them to take actions > > that result > > > in a further change to that same state. This is a race condition. > > > > Not in general -- this race condition arises in the draft-poetzl > > document because it's doing something with SUBSCRIBE that > > SUBSCRIBE was > > never meant to do: changing the state of the thing that is watched. > > > > Let's go back to first principles: SUBSCRIBE is a request > to retrieve > > the state of a resource, and receive that state whenever it > changes. > > It's a way for an observer to *LOOK* at a state. > > > > Now, as I'm always having to tell my kids: you look with your > > eyes, not > > with your hands. If the act of subscribing to a state changes > > that very > > state, then you're no longer looking -- you're touching. SUBSCRIBE > > doesn't touch the state it's monitoring. (Now, we have defined some > > *meta* state regarding the very state of that subscription, > > but you need > > to subscribe to that separately, and the act of subscribing to that > > meta-state doesn't change the meta-state). > > > > If you violate the basic principles on which a protocol was > > developed, > > then, yes, you end up with protocol characteristics that are highly > > undesirable. The race condition you describe is one. The > > objections that > > I have repeatedly raised with the "abuse" of SUBSCRIBE to > activate a > > service aren't purely academic: if you use a protocol in a > > way that is > > well outside its original design, then clearly identifiable > > bad things > > happen. > > > > > I share John's concerns as to whether this really > > interoperates with > > > the PSTN. Perhaps if you had some call flows > demonstrating it, this > > > would help. > > > > Martin has put together some pretty nice call flows showing > how this > > interoperates with the PSTN. Perhaps he could be convinced to > > share them > > with the wider group? > > > > /a > > > > _______________________________________________ > > Sipping mailing list https://www1.ietf.org/mailman/listinfo/sipping > > This list is for NEW development of the application of SIP > > Use sip-implementors@cs.columbia.edu for questions on current sip > > Use sip@ietf.org for new developments of core SIP > > > > _______________________________________________ > Sipping mailing list https://www1.ietf.org/mailman/listinfo/sipping > This list is for NEW development of the application of SIP > Use sip-implementors@cs.columbia.edu for questions on current sip > Use sip@ietf.org for new developments of core SIP > _______________________________________________ Sipping mailing list https://www1.ietf.org/mailman/listinfo/sipping This list is for NEW development of the application of SIP Use sip-implementors@cs.columbia.edu for questions on current sip Use sip@ietf.org for new developments of core SIP
- [Sipping] comments on draft-roach-sipping-callcom… Jonathan Rosenberg
- AW: [Sipping] comments on draft-roach-sipping-cal… Huelsemann, Martin
- Re: [Sipping] comments on draft-roach-sipping-cal… Adam Roach
- AW: [Sipping] comments on draft-roach-sipping-cal… Huelsemann, Martin
- RE: [Sipping] comments on draft-roach-sipping-cal… Elwell, John
- AW: [Sipping] comments on draft-roach-sipping-cal… Huelsemann, Martin
- RE: [Sipping] comments on draft-roach-sipping-cal… GARCIN Sebastien RD-CORE-ISS
- Re: AW: [Sipping] comments on draft-roach-sipping… Jonathan Rosenberg
- Re: AW: [Sipping] comments on draft-roach-sipping… Paul Kyzivat
- RE: [Sipping] comments on draft-roach-sipping-cal… Michael Hammer (mhammer)
- RE: [Sipping] comments on draft-roach-sipping-cal… GARCIN Sebastien RD-CORE-ISS
- Re: [Sipping] comments on draft-roach-sipping-cal… Jeroen van Bemmel
- RE: [Sipping] comments on draft-roach-sipping-cal… GARCIN Sebastien RD-CORE-ISS
- Re: [Sipping] comments on draft-roach-sipping-cal… Thomas.Froment
- Re: [Sipping] comments on draft-roach-sipping-cal… Jeroen van Bemmel
- RE: [Sipping] comments on draft-roach-sipping-cal… Michael Hammer (mhammer)
- RE: [Sipping] comments on draft-roach-sipping-cal… Elwell, John
- RE: [Sipping] comments on draft-roach-sipping-cal… Francois Audet