Hi Venkatesh, Phone1, Phone2, and Phone3 all share a line using your proposed scheme. Phone1 and Phone2 both try to seize at about the same time, but Phone1 is slightly faster.
Lets see what happens in two cases. First with a state agent: The NOTIFY from Phone1 is "accepted". The NOTIFY from Phone 2 is rejected, and according to RFC 3265, the dialog terminates. Oops. Now lets try this with a mesh of dialogs among the three phones. This is even worse as you have no idea whether Phone3 will accept the dialog update from Phone1 or from Phone2. State agents aren't supposed to change the semantics of the event package and I think this demonstrates that the proposed package does. thanks, -rohan > Francois: > > I am not sure about additional complexity with using SIP as the mechanism > and resulting in PUBLISH/NOTIFY flying all over the place. All the draft > was > proposing is that the UA send a NOTIFY indicating that it is going to > place > a call using a specific line *before* sending out the actual INVITE. This > NOTIFY would have gotten sent by the UA anyway post dialing. The draft is > just moving the position of when the NOTIFY gets sent out. From an end > user > perspective, when a user dials a number, he/she would simply see that it > is > 'attempting' to use a specific line appearance when the call is placed. If > there is no contention for that specific line, call proceeds fine. If the > NOTIFY is rejected, the line goes busy and user is provided a fast busy. > > Thanks > Venkatesh > > On Fri, Mar 21, 2008 at 12:15 PM, Francois Audet <[EMAIL PROTECTED]> wrote: > >> It's not POST call-setup. It's AT call setup. >> >> It's the difference between: >> >> Line seisure by pressing key >> >> - User press Line appearance. This is reported to Presence/Dialog >> server. PUBLISH or BFCP. >> - Presence/dialog for that line goes "busy" right away, for anybody >> that sees it >> - Nobody can use that line regardless of how long it takes the user >> to dial >> >> Line seisure at call setup >> >> - User press Line appearance. This is local: no reporting anywhere. >> - Nothing changes anywhere >> - Line is "seized" when the call is actually made >> - In the interim between pressing the key, somebody else could also >> press the key and make a call. If he's faster, he'll be able to seize >> the >> line before the first guy. >> >> Besides the mind-numbing complexity of doing the first approach, there >> are >> also advantages to the second approach. It avoids the problem of having >> somebody "hogging" the line by pressing on the key and not dialling >> anybody. >> >> And frankly, the SIP mechanism to "arbitrate" the >> line-seisure-by-pressing-an-appearance will by definition be very >> complicated and generate lots of traffic. I don't be believe it will be >> simpler than BFCP. >> >> Furthermore, there will be lots of potential for race condidtions (while >> the NOTIFYs and PUBLISH are flying all over the place). This will result >> in >> very poor user experience. Basically, pressing on the button will often >> "not >> work". (I have a vision of pissed-off users repeatedly pressing the key >> that >> doesn't want to turn on, and banging on their sets). >> >> The second option, with line seisure at call setup does not suffer from >> this problem. The expectation is that the line is "taken" when you >> actually >> make the call, not when you press the button. >> >> I will point out that PBXs (as opposed to key systems) often work the >> second way, not the first way. >> >> This is all very similar to arbitrating between making an outgoing call >> and receiving an incoming one while dialing. >> >> ------------------------------ >> *From:* Bill Mitchell [mailto:[EMAIL PROTECTED] >> *Sent:* Friday, March 21, 2008 11:58 >> *To:* DOLLY, MARTIN C, ATTLABS >> *Cc:* [email protected]; Audet, Francois (SC100:3055); [EMAIL PROTECTED] >> *Subject:* RE: [BLISS] MLA with Floor Control >> >> My answer is YES. Line seizing before call setup is worthwhile, >> because >> it enables shout control with a **reasonable end-user experience**. >> >> >> >> Line seizing post-call-setup is NOT worthwhile. It only adds confusion >> with potential mid or post-dial line key hopping. >> >> >> >> >> >> Pre-call-setup line seizure can be optional. >> >> >> >> >> >> BFCP has the right primitives, but I firmly agree with Venkatesh that it >> adds significant network complexity and would be a large barrier for >> implementation. I'll add my vote for a SIP-based mechanism to >> communicate >> line seize requests and responses. >> >> >> >> -Bill >> >> >> ------------------------------ >> >> *From:* [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] *On >> Behalf >> Of *DOLLY, MARTIN C, ATTLABS >> *Sent:* Friday, March 21, 2008 9:09 AM >> *To:* Francois Audet; Venkatesh; Paul Kyzivat >> *Cc:* Rohan Mahy; [email protected] >> *Subject:* Re: [BLISS] MLA with Floor Control >> >> >> >> I agree, NO >> >> >> ------------------------------ >> >> *From:* [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] *On >> Behalf >> Of *Francois Audet >> *Sent:* Friday, March 21, 2008 11:45 AM >> *To:* Venkatesh; Paul Kyzivat >> *Cc:* Rohan Mahy; [email protected] >> *Subject:* Re: [BLISS] MLA with Floor Control >> >> The real question is "should we do line seizing before call setup" as a >> worthwile feature. >> >> >> >> I think "No". >> >> >> >> If the group feels "Yes", then we could look at BFCP. I really think we >> should not be stupid enough to make this mandatory. >> >> >> ------------------------------ >> >> *From:* Venkatesh [mailto:[EMAIL PROTECTED] >> *Sent:* Thursday, March 20, 2008 21:49 >> *To:* Paul Kyzivat >> *Cc:* Audet, Francois (SC100:3055); Rohan Mahy; [email protected] >> *Subject:* Re: [BLISS] MLA with Floor Control >> >> I don't disagree with your argument. However, I also think, should a >> particular approach unduly complicate implementation of a feature >> (especially require support from multiple network elements for a feature >> to >> work), vendors are going to resort to non standard ways to implement the >> feature as well...... >> >> Venkatesh >> >> On Thu, Mar 20, 2008 at 9:15 PM, Paul Kyzivat <[EMAIL PROTECTED]> >> wrote: >> >> I'm not promoting one way or the other. Ultimately people building >> products will build the functionality they think they need to sell their >> products. If people feel this is important then they will want a way to >> do it. If it isn't standard then it will be nonstandard. >> >> Paul >> >> >> Francois Audet wrote: >> > >> > >> >> There is a tradeoff... >> >> >> >> If multiple extensions can place outgoing calls from the same >> >> line, then the line doesn't have "binary" status, so it can't >> >> be indicated as active or not with a light. And you can't >> >> "conference in" by picking up on the same line. >> >> >> >> While I am not into it myself, I can see how someone can >> >> build a "business process" around the specific way in which >> >> lines are managed by the phones, and then be very upset if >> >> they can't get that same user experience. >> > >> > Yeah, sure, it's doable. I do not believe that adding the concept >> > of a Line number to do this is required to do this, or even >> > desireable. >> > >> >> Now you can come up with some very nice UIs that provide >> >> better user experience, if you have a suitable display >> >> instead of just a bunch of lights. (E.g. an entry for the >> >> "number" (AOR that people call), and a variable length drop >> >> down list of active calls, showing the callerid of the >> >> caller, how long it has been active, and which extensions are >> >> currently connected to it.) But that is *different*, and >> >> requires a device with richer UI. >> > >> > Agreed. >> > >> > My point is that we shouldn't bastardize the protocol with all this >> > complex extra protocol (Line numbers, BFCP, NOTIFY/PUBLISH-storms, >> etc.) >> > just do do this. >> > >> > The basic "single-lamp" based approach is doable without any of this. >> > >> _______________________________________________ >> BLISS mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/bliss >> >> >> >> >> _______________________________________________ >> BLISS mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/bliss >> >> > _______________________________________________ BLISS mailing list [email protected] https://www.ietf.org/mailman/listinfo/bliss
