Subject: Re: [Sip] target dialog draft

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 04 Apr 2005 03:05:17 -0400

Elwell, John wrote:
> Jonathan,
> 
> Section 3:
> "Typically this is the case when the dialog-initiating request would have
> otherwise been sent over an existing dialog, but was not since this
> specification allows the request to be sent on a new dialog instead."
> This is a bit convoluted. The reason for not using the existing dialog is
> that it would introduce problems with dialog reuse etc., as stated earlier
> in the document. The mere existence of this target dialog spec is not in
> itself sufficient reason for using a new dialog.

OK, I reworded.

> 
> In the next paragraph:
> Change "sent out a dialog" to "sent outside a dialog".

fixed.

> 
> Join and Replaces headers have "to-tag" and "from-tag" with corresponding
> text saying how these relate to the local tag and remote tag respectively at
> the recipient. Would it not be a good idea to stick to the same parameter
> names as Join and Replaces? Likewise the style of BNF is slightly different
> from that used in Join and Replaces. Would alignment be sensible? I don't
> have a strong opinion on these - just a suggestion.

I don't like using those names since they are misleading; whether those 
identifiers represent the values of a to or from tag depend on whether 
the user sends or receives a request. However, the local and remote tags 
are fixed, as they explicitly point to values stored locally in the UA.

You are correct though about the grammar style otherwise. I suspect it 
will confuse people, since the current grammar is more restrictive than 
Join; the parameter ordering is fixed. That is unusual for our 
parameters. So, I fixed this to look like the Join syntax.

> 
> What use do you envisage for this new header in an UPDATE request (for which
> it is marked optional in figure 4)?

Hmm. I think thats a bug. It only makes sense for dialog initiating 
requests, and that excludes UPDATE.

> 
> The title of figure 4 seems wrong.

Oops. Copy-paste error.

Thanks for your comments,
Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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