Subject: [Sip] I-D ACTION:draft-ietf-sip-gruu-12.txt

From: [email-masked]
Date: Thu, 08 Mar 2007 15:50:03 -0500

A New Internet-Draft is available from the on-line Internet-Drafts 
directories.
This draft is a work item of the Session Initiation Protocol Working Group of the IETF.

	Title		: Obtaining and Using Globally Routable User Agent (UA) URIs (GRUU) in the Session Initiation Protocol (SIP)
	Author(s)	: J. Rosenberg
	Filename	: draft-ietf-sip-gruu-12.txt
	Pages		: 37
	Date		: 2007-3-8
	
Several applications of the Session Initiation Protocol (SIP) require
   a user agent (UA) to construct and distribute a URI that can be used
   by anyone on the Internet to route a call to that specific UA
   instance.  A URI that routes to a specific UA instance is called a
   Globally Routable UA URI (GRUU).  This document describes an
   extension to SIP for obtaining a GRUU from a registrar and for
   communicating a GRUU to a peer within a dialog.

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---

From: "Jeroen van Bemmel" <[email-masked]>
Date: Thu, 8 Mar 2007 23:46:53 +0100

Jonathan,

4 comments:

1. Section 5.1: recommend to somehow explicitly add that for a contact which 
has expires=0, it should be avoided to construct a public GRUU or any new 
temporary GRUUs
2. Section 5.2: the text about Contact:* and Expires:0 is better placed in 
section 5.1
3. Section 6.2 second paragraph: could add explicitly that the GRUU needs to 
be still valid
4. Section 9 (Example call flow) remark under last message: what if the 
GRUU-enabled registrar does not support outbound?

More on point 4: the text in outbound-08 regarding "most recent registration 
first" is in section 3.2: "If the instance-id and reg-id are the same as a 
previous registration for the same AOR, the registrar replaces the old 
Contact URI and flow information." This means that the example will not work 
correctly unless the registrar supports this part of outbound behavior (with 
a difference that it won't necessarily need to deal with 'reg-id')

Perhaps this hints at a missing requirement for the authorative proxy: 
namely that it MUST target Contacts with the same instance-id in 
most-recent-first order, and MUST NOT try a second one if a first one gives 
a final response (ref section 7 of outbound-08)

nits:
- in section 4.4:  The only reason not to use a *public* GRUU would be 
privacy considerations
- section 5.3: yet still meet -> add s
- in section 10.3: invalidate temporary a GRUU (switch "temporary" and "a")

Regards,
Jeroen

[email-masked] wrote:
>> Title : Obtaining and Using Globally Routable User Agent (UA) URIs
>> (GRUU) in the Session Initiation Protocol (SIP) Author(s) : J.
>> Rosenberg
>>   a user agent (UA) to construct and distribute a URI that can be
>>   used by anyone on the Internet to route a call to that specific UA
>> You can also visit
>> https://www1.ietf.org/mailman/listinfo/I-D-announce

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 19 Mar 2007 05:13:07 -0400

Jeroen van Bemmel wrote:

> Jonathan,
> 
> 4 comments:
> 
> 1. Section 5.1: recommend to somehow explicitly add that for a contact 
> which has expires=0, it should be avoided to construct a public GRUU or 
> any new temporary GRUUs

OK, clarified to '...if present with a non-zero expiration..."

> 2. Section 5.2: the text about Contact:* and Expires:0 is better placed 
> in section 5.1

moved

> 3. Section 6.2 second paragraph: could add explicitly that the GRUU 
> needs to be still valid

Added. Also made a bulleted list.

> GRUU-enabled registrar does not support outbound?

Then it would use it for forking but it would eventually evaporate. For 
this example I haven't included sip-outbound. Per below I've fixed this 
so it won't get used; the reference now points to that text in GRUU 
which says this.

> 
> More on point 4: the text in outbound-08 regarding "most recent 
> registration first" is in section 3.2: "If the instance-id and reg-id 
> are the same as a previous registration for the same AOR, the registrar 
> replaces the old Contact URI and flow information." This means that the 
> example will not work correctly unless the registrar supports this part 
> of outbound behavior (with a difference that it won't necessarily need 
> to deal with 'reg-id')
> 
> most-recent-first order, and MUST NOT try a second one if a first one 
> gives a final response (ref section 7 of outbound-08)

Hmm. This is a good point. I believe you are correct; GRUU at the moment 
says that if you have more than one registered contact per instance you 
need sip-outbound. But if there is a single contact and you are using 
GRUU, you should replace since if you were having multiple contacts from 
the same instance you would have sip-outbound. I've updated to fix this.

> - in section 4.4:  The only reason not to use a *public* GRUU would be 

No - there are also cases where you don't even use a temp-GRUU. This is 
described in the privacy considerations.

> - section 5.3: yet still meet -> add s

fixed

> - in section 10.3: invalidate temporary a GRUU (switch "temporary" and "a")

fixed

Thanks,
Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
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