Subject: Re: [Sipping] Exploders and ad-hoc lists

From: Paul Kyzivat <[email-masked]>
Date: Mon, 08 Dec 2003 09:32:32 -0500

Xavier,

Depending on circumstance and preference, it is ok for the subscription 
to either share the dialog with the invite or create a new one.

Circumstances that may affect the decision:
- if the contact from the invite is not globally routable,
   then reusing the dialog will be successful while
   attempting to establish a new one may not be.
- if the contact is globally routable, (see GRUU proposal)
   then either way should work.
- there may be some slight efficiency to reusing a dialog
- there may be some UAs that don't support dialog sharing

If everybody is fully compliant to all the rules, then the contact will 
be globally routable, and dialog sharing will be supported, so that 
either choice is ok. If one end or the other isn't fully compliant, then 
one or the other may be preferable, but there is no general way to tell 
which one is most likely to work.

	Paul

Marjou Xavier wrote:
> Hi,
> 
> In draft-camarillo-sipping-uri-list-00.txt, it is written that:
> "The conference server responds with a 200 (OK) that carries the URI for the conference in its Contact header field. If the UA wants to obtain information about the status of the conference, for instance, it will SUBSCRIBE to the conference package using this URI."
> 
> Will the SUBSCRIBE be sent in the dialog of the INVITE, or will it create its own dialog?
> 
> Regards,
> Xavier
> 
> 
> _______________________________________________
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_______________________________________________
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This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
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---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 09 Dec 2003 00:58:01 -0500

> which one is most likely to work.

You are mixing two cases - one case where the UA doesn't support a 
feature mandated by 3261 (dialog sharing), and the other, where it 
doesnt support an extension (gruu). Dealing with the first one of 
these is generally hard, and not something we can really address. 
However, dealing with the second case is easy. If the peer UA 
indicated support for GRUU (from the presence of the Supported: gruu 
header field), send the subscribe in a new dialog. Otherwise, reuse 
the dialog.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
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