AW: [Sipping-tispan] Requirements -02h

["Poetzl, Joachim" <[e-mail]>]

Hi all,

If I understood correctly we are mixing two things up here.

We have to differentiate two approaches in PSTN world:

Functianal protocoll - The service executing entity knows if the callee (A) is free/not busy and can (if he wishes) accept and incoming CCBS recall indication which will lead to an call setup procedure to User B. This is done by an facility element checking user As Status

Keypad approach - hence the Callees terminal does not support protocol elememnts / procedures the service executing entity will set up a call to the callee which may be busy which will not happen in the functional case. If the user is free he can accept the call.

Even that ITU I253.3 talks abot an CCBS recall we should be clear that we are talking about an indication to the user (functional case) or a call to the USER A (CCBS recall).

Taken from I.253.3:
2.2.4	CCBS recall: A network-to-user indication, informing user A that the network is ready to initiate a CCBS call to destination B and that the network is awaiting a response to this indication from user A.
2.2.5	CCBS call: Call set-up by the network from user A to destination B resulting from user A's acceptance of a CCBS recall.

Regards


Joachim Pötzl
Deutsche Telekom AG
T-Com Zentrale
TE332-4; Dienste- und Netzkonvergenz, Protokolle von NGN
64307 DARMSTADT, GERMANY 
Phone:  [phone]
Fax:      [phone]
PCFax:  [phone]
>mailto:[e-mail] 



-----Ursprüngliche Nachricht-----
Von: [e-mail] [mailto:[e-mail]] Im Auftrag von Drage, Keith (Keith)
Gesendet: Dienstag, 11. Oktober 2005 23:09
An: 'Paul Kyzivat'; 'Michael Hammer (mhammer)'
Cc: '[e-mail]'
Betreff: RE: [Sipping-tispan] Requirements -02h


In the ISDN service there is no "try again" to the callee, once the CCBS completion has been presented to the end terminal, and therefore performed alerting to the absent user.. 

As you identify, it is almost impossible to identify an algorithm that works for the user, apart from the knowledge that the user is there and involved in another call. In the latter case, the callee is not alerted on the assumption that the user can only deal with one call at once.

So, just as on every PBX that I know of, if the recall to the callee fails, then the CCBS is cancelled. The callee can come back to the phone, interrogate the service to see if the CCBS request is still there, and if it is not, then reactivate it.

regards

Keith

> -----Original Message-----
> From: [e-mail]
> [mailto:[e-mail]]On Behalf Of Paul Kyzivat
> Sent: 30 September 2005 18:43
> To: Michael Hammer (mhammer)
> Cc: [e-mail]; Alexeitsev, D
> Subject: Re: [Sipping-tispan] Requirements -02h
> 
> 
> 
> 
> Michael Hammer (mhammer) wrote:
> > Paul,
> > 
> > This would suggest that so long as one terminal belonging 
> to the AoR has
> > the capability to accept another call *and* that terminal 
> was recently
> > used by the user
> 
> This is the weak spot in the whole service.
> 
> If the callee has been alerted without success once, there is 
> need for 
> some algorithm to decide when to try again. *Any* change in 
> state of any 
> registered UA may be considered justification for trying 
> again. But even 
> that isn't a great huristic. I may have been gone all afternoon, and 
> have recently returned. I am now available though I have not recently 
> used any terminal. I would think that even in the absence of 
> any state 
> change, another attempt should be made periodically.
> 
> > (hopefully the correct human),
> 
> I think by definition any human that can cause the terminal 
> to answer is 
> a correct human. Certainly that is the assumption when regular calls 
> arrive, and I see no reason why it should be different here.
> 
> > an attempt should be
> > made to complete using that terminal (plus any terminal 
> that can accept
> > a call independent of activity - could be broadcast to all).
> > 
> > Boy, hope that presence system is smart.
> 
> One that can detect "someone is now in the area" would be good.
> 
> 	Paul
> 
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