The trying state in RFC 4235 is ok (that's after the INVITE). No ptoblems there.
It's the line seize BEFORE sending an INVITE that is a problem.
________________________________
From: Venkatesh [mailto:[EMAIL PROTECTED]
Sent: Friday, March 21, 2008 13:35
To: Audet, Francois (SC100:3055)
Cc: Bill Mitchell; [email protected]
Subject: Re: [BLISS] MLA with Floor Control
Francois:
The dialog state RFC 4325 specifically provides a "trying" state to
indicate a state where a call is about to be initiated. We are simply using
this state to indicate origination of a new call request.
Thanks
Venkatesh
On Fri, Mar 21, 2008 at 1:19 PM, Francois Audet <[EMAIL PROTECTED]>
wrote:
I really believe that this whole idea of "line seizure" is
completely out-of-line with the SIP model.
If we do something like that, we are completely changing the
nature of SIP and making it a stimulus control protocol like MGCP (or the old
proprietary Phone control protocols used by many vendors, including my
employer).
If we go in that direction, we would need to redefine what "on
the phone" means, so that instead of "in a session", it would mean "off-hook".
Every single INVITE would now be preceded by a PUBLISH of some "off-hook"
status. This would not only hamper significantly scalability of SIP, but would
make it a different protocol.
What's next? Cursor control? Bitmap screen control?
If one wants a blast from the past with these types of
features, one should stick with protocols from the past.
I am completely opposed to changing SIP to be a stimulus
protocol.
________________________________
From: Bill Mitchell [mailto:[EMAIL PROTECTED]
Sent: Friday, March 21, 2008 12:55
To: Audet, Francois (SC100:3055)
Cc: [email protected]
Subject: RE: [BLISS] MLA with Floor Control
Completely agree that line seizure upon
line-key-selection is complex, but the idea behind line seizure over SIP was to
minimize complexity. We've heard that customers want the functionality for
shout control. And issues like line key hogging can be addressed with a proper
implementation.
My terminology wasn't quite right. I should have said
"Line seizure post-line-key-selection" is not worthwhile. If the client is
going to render a UI based on the line #, for purposes of shout-control, then
"Line Key Hopping" will occur. When a user has selected a line key and is
dialing, an Inbound call will force a change in line key usage, as will an
outbound call placed from a different phone. I see this as unacceptable to
most users.
________________________________
From: Francois Audet [mailto:[EMAIL PROTECTED]
Sent: Friday, March 21, 2008 12:15 PM
To: Bill Mitchell; DOLLY, MARTIN C, ATTLABS
Cc: [email protected]; [EMAIL PROTECTED]
Subject: RE: [BLISS] MLA with Floor Control
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.
>
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