Subject: Re: [Sipping] Dialoge states / Interworking CCBS/CCNR

From: "Alexeitsev, D" <[email-masked]>
Date: Thu, 1 Aug 2002 10:55:52 +0200

Hello Mark,

Some issues inline 

 I am still confused about how dialog state can be used to implement CCBS-like service when the called party is a normal SIP UA (rather than a PSTN gateway).

If there are three dialogs in progress at the terminating UA, how do you know which one is keeping the user 'busy'. Perhaps two of them are for IM sessions, and the user is happy to take voice calls whilst the IM sessions are ongoing. 

What about the remote/local-session-description (not always available)?

Or there are might be some user preferences like "urgent"/"busy" that could be assigned to a dialog by the user.

In general I share your confusion and would like to ask the group for clarification on this topic.  

Or is your intention only to implement an 'asymetric' service, where SIP users can invoke CCBS against PSTN endpoints but not vice-versa ? 

That's the main target, but even in this case we are missing the general consensus about the definition of a dialog busyness from the user perspective.

comments? 

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---

From: Michael Hammer <[email-masked]>
Date: Thu, 01 Aug 2002 10:02:37 -0400

Denis,

It would seem that, if one really feels the need to do this at all (given 
that voice-mail tends to obviate a busy condition), that it should be 
interworked with a presence interworking application, as this is 
essentially a subscription to the presence of the destination user.

Mike

At 10:55 AM 8/1/2002 +0200, Alexeitsev, D wrote:
>Hello Mark,
>
>Some issues inline
>
>  I am still confused about how dialog state can be used to implement 
> CCBS-like service when the called party is a normal SIP UA (rather than a 
> PSTN gateway).
>
>If there are three dialogs in progress at the terminating UA, how do you 
>know which one is keeping the user 'busy'. Perhaps two of them are for IM 
>sessions, and the user is happy to take voice calls whilst the IM sessions 
>are ongoing.
>
>Or there are might be some user preferences like "urgent"/"busy" that 
>could be assigned to a dialog by the user.
>
>Or is your intention only to implement an 'asymetric' service, where SIP 
>users can invoke CCBS against PSTN endpoints but not vice-versa ?
>
>That's the main target, but even in this case we are missing the general 
>consensus about the definition of a dialog busyness from the user perspective.
>
>comments?
>
>

---

From: "Elwell, John" <[email-masked]>
Date: Thu, 01 Aug 2002 16:13:56 +0100

Picking up on a couple of comments made in this thread:

I don't think voice mail completely replaces the traditional CCBS in public
or private PSTN/ISDN. With voice mail the onus is on the recipient to return
the call (or take whatever action is requested). The recipient will do so at
a time that suits him. Often this is good enough for the caller, but not
always. Sometimes he will regard the situation as urgent enough to make the
call as soon as the called user becomes "free". For this traditional
networks offer both CCBS and call waiting. Call waiting means that the
caller has to keep the call open and keep listening, which may or may not
suit the caller. CCBS gives an intermediate capability. It all comes down to
what the caller prefers in a given situation.

I would not be happy about just addressing Denis's "main target", where SIP
users can invoke a CCBS-like service on PSTN/ISDN users. The other
direction, and also the provision of a similar service between SIP users,
are equally important. If a similar service between SIP users can already be
made available through use of presence, then we should see whether this can
be interworked with PSTN/ISDN (including QSIG as well as ISUP) in each
direction.

--------------------------------------------------------------
John Elwell ([email-masked])
Siemens Communications Limited,
--------------------------------------------------------------
	Internet communications are not secure and therefore Siemens
Communications Limited does not accept legal responsibility for the
contents of this message. Any views or opinions presented are solely
those of the author and do not necessarily represent those of Siemens
Communications Limited unless otherwise specifically stated.

> -----Original Message-----
> From: Michael Hammer [mailto:[email-masked]]
> Sent: 01 August 2002 15:03
> To: Alexeitsev, D
> Cc: [email-masked]; [email-masked]; Poetzl, Joachim
> Subject: Re: [Sipping] Dialoge states / Interworking CCBS/CCNR
> 
> 
> Denis,
> 
> >In general I share your confusion and would like to ask the 
> group for 
> >clarification on this topic.
> >

---

From: "Alexeitsev, D" <[email-masked]>
Date: Thu, 1 Aug 2002 17:44:36 +0200

Hello John

Thanks for the constructive comments!

Some issues inline:

[DA] Sorry for confusion cased by the "main target" phrase. What we are trying to achieve is to get the service through the GW in both directions. The targeting comes from the issue that there is no common understanding when the UAs user is busy. That gave us a thought to start first with the SIP->ISDN direction. 
You are correct speaking about the SIP-SIP case as well. It wont be beneficial to separate this cases. That is why we will base our research on the event package for dialog state as it is the basic element for this type of services in the SIP net.

I'm not sure I fully understand how the presence information can help in the determination of the user busyness. 
Would it be possible to solve this issue by extending the notion of the virtual FSM to represent the state of the User?

Greetings,
Denis Alexeitsev

---

From: Michael Hammer <[email-masked]>
Date: Thu, 01 Aug 2002 12:11:15 -0400

John,

My comment concerning voice-mail was directed to the fact that a call 
forwarded to voice mail is never busy.  Do current implementations of CCBS 
get triggered off of Call Forward Busy?

My thought in terms of presence-CCBS IW was that a request from the PSTN 
for CCBS would trigger a Subscription to the SIP user's presence.  (I won't 
re-trace the discussion about Open/Close versus more detailed 
states.)  Upon Notification of the "open for voice communication" state 
(however that is rendered), the IW GW would send the appropriate CCBS 
signaling that triggers the PSTN user to re-attempt the voice call.

In the opposite direction, if the SIP user submits a Subscription for 
presence related to voice communication state of the PSTN user, then 
corresponding CCBS procedures are invoked.  When CCBS indicates PSTN user 
is not busy, then Notification to SIP user indicates "open for voice 
communication."

That is the overall conecpt, but the details still fuzzy.

Mike

---

From: "Elwell, John" <[email-masked]>
Date: Fri, 02 Aug 2002 08:17:39 +0100

Mike,

See in-line.

John

> Sent: 01 August 2002 17:11
> To: Elwell, John
> Cc: Alexeitsev, D; [email-masked]; 
> [email-masked]; Poetzl,
> Joachim
> Subject: RE: [Sipping] Dialoge states / Interworking CCBS/CCNR
> 
> 
> John,
> 

[JRE] In most cases probably not, except where used in conjunction with a
forwarding override capability (more common on PBXs than public networks),
thereby forcing the call to encounter busy or call waiting. In theory, of
course, an entity could invoke CCBS (or CCNR) at any time, not necessarily
after encountering busy / call waiting.

> That is the overall conecpt, but the details still fuzzy.

[JRE] Yes, that is the sort of thing I imagined.

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