Subject: RE: [Sip] RE: [Sipping] Call and call-id

From: "Sean Olson (EUS)" <[email-masked]>
Date: Wed, 27 Jun 2001 10:18:59 -0500

Have you considered the DCS State: draft for this mechanism?
See 
http://www.softarmor.com/sipwg/drafts/draft-ietf-sip-state-01.txt <http://www.softarmor.com/sipwg/drafts/draft-ietf-sip-state-01.txt> 
 
IMHO, I don't see a need for such a use of a Cookie. Correlating
messages to calls is not that difficult. The key thing to note, as you 
have, is that Call-ID is not necessarily useful for tying multiple call
legs together. 
 
/sean

-----Original Message-----
From: Zmolek, Andrew (Andrew) [mailto:[email-masked]]
Sent: Wednesday, June 27, 2001 9:55 AM
To: Chris Hogg; Jonathan Rosenberg; Mathieu, Marie-Noelle; [email-masked]
Subject: RE: [Sip] RE: [Sipping] Call and call-id

I think it would be good to clarify our terminology, particularly since we sometimes forget SIP does not provide directly for a call with multiple active call legs (i.e. B2BUA is needed to rationalize each individual SIP call with the overall session). I propose we define "call" to mean the two participants in any given transaction and "session" to be some collection of calls associated within a given UA (note that "invited by a common source" is not a complete description since some or all of the invites could have originated outside the UA). 
 
This thread brings out several reasons why Call-ID should not be used to define a "session" of multiple "calls" as defined above. Mainly because of this, I'm preparing an I-D to address this need through the use of header extensions for cookies, which each UA can independently grant and accept in order to correlate call legs and potentially provide additional context for a given call. The alternative is vendor-specific headers and a walled garden approach to many features available in conventional PBXes today, and I don't think that's beneficial for SIP in the long run.
 
--Andy Zmolek
    Technology & Standards Engineer
      CTO Standards
        Avaya Inc.

            [email-masked]
              +1 720 444 4001

 
 -----Original Message-----
From: Chris Hogg [mailto:[email-masked]]
Sent: Wednesday, June 27, 2001 4:03 AM
To: 'Jonathan Rosenberg'; Zmolek, Andrew (Andrew); Mathieu, Marie-Noelle; [email-masked]
Subject: RE: [Sip] RE: [Sipping] Call and call-id

Hi Jonathan, 

Jonathan Rosenberg wrote: 

>Careful; I am not proposing that two call legs with the same Call-ID convey 
>any semantics. Specifically, receiving an INVITE from A, while in a call 
>with B, where the call-id in the INVITE from A equals the call-id in the leg 
>with B, does NOT imply that this is a consultative transfer. For that, we 
>have Replaces, which lists the replaced leg explicitly. 

>All I am saying is that a Call-ID may be reused for local convenience, if 
>desired, but that it has NO semantics outside of the entity that selected 
>that call-id. 

Given, what you are proposing will this not mean that the definition of a call needs to be altered?  The reason I ask is that bis-03 defines a call as "identified by a globally unique callID" and "all participants invited by a common source".  In the case you describe under the current definition of a call this would mean that we would have two calls (under the "all participants invited by a common source" rule) but with the same callID (hence contravening the "globally unique callID" part).    

Comments? 

Regards, 

Chris Hogg 
Nortel Networks. 

-----Original Message----- 
From: Jonathan Rosenberg [ mailto:[email-masked] <mailto:[email-masked]> ] 
Sent: 26 June 2001 22:51 
To: 'Zmolek, Andrew (Andrew)'; Jonathan Rosenberg; Mathieu, 
Marie-Noelle; [email-masked] 
Subject: RE: [Sip] RE: [Sipping] Call and call-id 

-----Original Message----- 
From: Zmolek, Andrew (Andrew) [ mailto:[email-masked] <mailto:[email-masked]> ] 
Sent: Tuesday, June 26, 2001 12:35 PM 
To: Jonathan Rosenberg; Mathieu, Marie-Noelle; [email-masked] 
Subject: RE: [Sip] RE: [Sipping] Call and call-id 

>> >same call-id in the 2 INVITE requests, is this allowed ? 
>> 
>> Well, the current spec would indicate that you shouldn't do this: 
>> 
>> >The callid MUST be a globally unique identifier and MUST NOT be reused 
for 
>> >later calls. 
>> 
>> However, I recall some discussion at an IETF that people were using the 
same 
>> call-id across different call legs as a local identifier to correlate 
those 
>> call legs. With unique From tags and From fields, there really shouldn't 
be 
>> a problem, so I think its OK. However, if we are going to allow it, the 
spec 
>> should reflect it. Comments? 
> 
>If that's the proper way to solve this problem, then let's put that in the 
>spec. But I'm not convinced that this alone will solve all cases, 
especially 
>when this correlated information needs to be presented by a call leg 
attempting 
>to join (as in the consultative transfer case). 

Careful; I am not proposing that two call legs with the same Call-ID convey 
any semantics. Specifically, receiving an INVITE from A, while in a call 
with B, where the call-id in the INVITE from A equals the call-id in the leg 
with B, does NOT imply that this is a consultative transfer. For that, we 
have Replaces, which lists the replaced leg explicitly. 

All I am saying is that a Call-ID may be reused for local convenience, if 
desired, but that it has NO semantics outside of the entity that selected 
that call-id. 

> It only seems to work when the 
>correlating entity initiates all the calls. If there's a reliable way to 
>correlate an incoming call leg with an existing call, I'd love to hear 
about 
>it. 

http://www.softarmor.com/sipwg/drafts/morgue/draft-biggs-sip-replaces-00.txt <http://www.softarmor.com/sipwg/drafts/morgue/draft-biggs-sip-replaces-00.txt>  

needs updating and adoption though, if we plan to move forward with it. As 
you can see, its currently in the morgue. 

-Jonathan R. 
--- 
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave. 
Chief Scientist                             First Floor 
dynamicsoft                                 East Hanover, NJ 07936 
[email-masked]                     FAX:   (973) 952-5050 
http://www.jdrosen.net <http://www.jdrosen.net>                       PHONE: (973) 952-5000 
http://www.dynamicsoft.com <http://www.dynamicsoft.com>  

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From: Gonzalo Camarillo <[email-masked]>
Date: Wed, 27 Jun 2001 22:18:03 +0300

Hello,

>have, is that Call-ID is not necessarily useful for tying multiple call

Note that in
http://search.ietf.org/internet-drafts/draft-ietf-sip-overlap-00.txt

we use the call-ID to correlate different INVITEs for the same call.
However, since the draft clearly states that such a mechanism is to be
used only in a controlled enviroment, I do not think we should worry
about it in this discussion.

This mail was just a clarification. I agree with what Sean said.

Regards,

Gonzalo
-- 
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Columbia University                  Mobile:  +358 40 702 35 35
472 Computer Science Building        Fax   :  +358  9 299 30 52
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