Subject: [Sip] outbound-08 : using different Contact URIs for different flows?

From: "Jeroen van Bemmel" <[email-masked]>
Date: Sat, 28 Apr 2007 17:17:41 +0200

All,

While trying to implement GRUU and outbound in combination, I stumbled upon 
a minor issue: what if the UAC uses different Contact URIs when registering 
multiple flows. The examples in outbound don't do this, but there is no 
explicit statement that this is not allowed, and the example in 3.2 
([email-masked]>;reg-id=1) could be seen as suggesting that the 
registration with reg-id=2 would use "line2"

See my previous mail: for GRUU this could mean that the authorative proxy 
cannot select the right URI to rewrite with, there can be an inconsistency 
between the temporary GRUU the UAC selected (associated with a specific 
contact) and the request URI received.

One solution may be to adapt the algorithm used to generate temporary GRUUs. 
A second option, which is perhaps simpler, is to simply state in outbound 
that the UAC MUST use identical Contact URIs when registering multiple flows 
(in section 4.2), and that the authoritative proxy MAY select any one of the 
registered Contact URIs to rewrite with (e.g. needed to cover transitional 
cases where the UAC obtains a new IP address and starts re-registering)

Regards,
Jeroen

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---

From: Paul Kyzivat <[email-masked]>
Date: Sun, 29 Apr 2007 23:53:43 -0400

Jeroen,

Abstractly I understand your issue, and it seems valid, though I would 
like to think about it a bit.

But I'm trying to think of why you would want to do this. If a single UA 
registers multiple contacts with the same AOR, then it is pretty likely 
that incoming calls will be delivered to the UA multiple times. That 
seems like an undesirable situation.

	Paul

Jeroen van Bemmel wrote:
> All,
>  
> While trying to implement GRUU and outbound in combination, I stumbled 
> upon a minor issue: what if the UAC uses different Contact URIs when 
> registering multiple flows. The examples in outbound don't do this, but 
> there is no explicit statement that this is not allowed, and the example 
> in 3.2 ([email-masked]>;reg-id=1 
> <mailto:[email-masked]>;reg-id=1>) could be seen as suggesting that 
> the registration with reg-id=2 would use "line2"
>  
> See my previous mail: for GRUU this could mean that the authorative 
> proxy cannot select the right URI to rewrite with, there can be an 
> inconsistency between the temporary GRUU the UAC selected (associated 
> with a specific contact) and the request URI received.
>  
> One solution may be to adapt the algorithm used to generate temporary 
> GRUUs. A second option, which is perhaps simpler, is to simply state in 
> outbound that the UAC MUST use identical Contact URIs when registering 
> multiple flows (in section 4.2), and that the authoritative proxy MAY 
> select any one of the registered Contact URIs to rewrite with (e.g. 
> needed to cover transitional cases where the UAC obtains a new IP 
> address and starts re-registering)
>  
> Regards,
> Jeroen
>  
>  
> 
> 
> ------------------------------------------------------------------------
>