Subject: Re: [Sip] Updated GRUU spec - big changes

From: "Jeroen van Bemmel" <[email-masked]>
Date: Sun, 4 Mar 2007 00:27:48 +0100

Jonathan Rosenberg wrote:
> I've submitted an update to the GRUU spec. Until it appears in the
> archives, you can pick it up at:
>
> http://www.jdrosen.net/papers/draft-ietf-sip-gruu-11.txt
>

Jonathan,

Two minor comments:
1) I believe a UA is allowed to add a 'transport=tcp' parameter when using a 
GRUU obtained from a registrar, perhaps this should be mentioned explicitly 
somewhere (e.g. section 4.4).
2) (nit) in light of rfc4320, the references to 18x responses to SUBSCRIBE 
and REFER in section 4.4 should be removed

Regards,
Jeroen 

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 04 Mar 2007 07:21:08 -0500

inline.

Jeroen van Bemmel wrote:

> 1) I believe a UA is allowed to add a 'transport=tcp' parameter when 
> using a GRUU obtained from a registrar, perhaps this should be mentioned 
> explicitly somewhere (e.g. section 4.4).

I don't think so; the GRUU terminates on the registrar, so only the 
registrar knows what transports are really supported.

> 2) (nit) in light of rfc4320, the references to 18x responses to 
> SUBSCRIBE and REFER in section 4.4 should be removed

OK.

-Jonathan R.

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

---

From: "Jeroen van Bemmel" <[email-masked]>
Date: Sun, 4 Mar 2007 17:26:42 +0100

>> using a GRUU obtained from a registrar, perhaps this should be
>> mentioned explicitly somewhere (e.g. section 4.4).
>

In that case there seems to be a missing requirement: it should be possible 
for a UA to obtain a GRUU for a particular transport (in practice: tcp). 
While it is true that only the registrar knows which transports are 
supported, if it is RFC3261 compliant it MUST support TCP and TLS (26.3.1).

So either we allow the UAC to assume support for TCP/TLS, or we need some 
signaling to indicate preference / supported transports

Regards,
Jeroen

---

From: "Jeroen van Bemmel" <[email-masked]>
Date: Sun, 4 Mar 2007 17:50:01 +0100

> In that case there seems to be a missing requirement: it should be
> possible for a UA to obtain a GRUU for a particular transport (in
> practice: tcp). While it is true that only the registrar knows which
> transports are supported, if it is RFC3261 compliant it MUST support
> TCP and TLS (26.3.1).
> So either we allow the UAC to assume support for TCP/TLS, or we need
> some signaling to indicate preference / supported transports
>

On second thought: any transport param (or port component for that matter) 
would be ignored by the registrar / home proxy when using the GRUU as an 
index into the location service. So the transport that gets used is the 
transport from the registered contact address (with possible exception of 
UDP->TCP switch for large requests). This implies that the UA no longer has 
a choice for transport upon initiating/responding to a dialog, it is 
determined at registration time.

Should we add some words to make this explicit? Perhaps it would be good to 
state that the UA SHOULD use the obtained GRUU verbatim, without adding 
parameters etc

Regards,
Jeroen