Subject: Re: [Sip] GRUU Mechanism I-D

From: Rohan Mahy <[email-masked]>
Date: Thu, 6 Nov 2003 07:28:19 -0800

Frankly, I think this medicine will kill the patient.  While not 
pretty, what we have *is* implemented and implementable. While not what 
we would have chosen another go-around, I think we should stick with 
the behavior we have.

thanks,
-rohan

On Wednesday, November 5, 2003, at 12:56 PM, Adam Roach wrote:

>> I do think it would be very good medicine for the protocol to
>> deprecate all dialog reuse.
>
> Hear, hear!
>
>> My personal preference for modifying REFER is to deprecate the
>> implicit subscription behavior altogether (by strengthening the
>> mechanisms proposed in Sean's and Rohan's drafts perhaps).
>
> I agree with this course of action, for the reasons you cite,
> and others.
>
> /a

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From: Volker Hilt <[email-masked]>
Date: Thu, 06 Nov 2003 17:34:22 -0500

The main issue with deprecating the implicit subscription seems to be 
that it must be done in a backwards compatible way, since a lot of 
implementations already exist. To my understanding, a backwards 
compatible solution would need to:
- enable the UAC to detect, whether the UAS is an "old" UA that uses the 
deprecated implicit subscriptions or a "new" UA that supports explicit 
subscriptions.
- enable the UAS to detect, whether the UAC expects implicit or explicit 
subscriptions.

Would a new option tag help (along the lines of Sean's draft) that is 
mandatory for new implementations? Btw. since explicit subscriptions 
require the UAS to use a gruu, the first case could be covered just by 
looking for the gruu option tag. However, I'm not sure if it is safe to 
assume that a "new" UAC also includes a gruu in its REFER request (in 
this case, we could even use the "gruu" option tag as an indicator).

-- Volker

-- 
Volker Hilt                      Bell Labs / Lucent Technologies
phone: +1 732 332 6432           101 Crawfords Corner Rd
email: [email-masked]     Holmdel, NJ 07733