Re: [Sip] draft-ietf-sip-gruu-10 comments

[Cullen Jennings <fluffy at cisco.com>]

On Sep 11, 2006, at 12:21 PM, Paul Kyzivat wrote:

> Cullen Jennings wrote:
>
> > Section 8.2.2
> > I think I am likely confused here. I basically don't see why a  
> > simple classic sip trapezoid deployment would ever need to Record  
> > Route. The fact that the GRUU refereed to the "home" domain would  
> > cause it work get back here. As a side note, I find the terms  
> > "home", "edge" etc very undefined outside the IMS context.  
> > Anyways, I believe this section might be all right but I am  
> > failing to understand what needs to be done and why. If I was a  
> > non IMS proxy implementer, I suspect I would just ignore this  
> > whole section.
>
> *If* the topology is a simple trapezoid then I think you are correct.
>
> But if there is a proxy before the originating home proxy, or after  
> the terminating home proxy, then the R-R is needed to prevent a  
> spiral.
>
> On the originating side, this can be determined by whether there is  
> a R-R present when the request arrives at the originating home  
> proxy. On the terminating side that doesn't work, because the  
> potential R-R hasn't happened yet, and you can't know in advance if  
> it will happen.
>
> So the problem is that you don't need it in a trapezoid, but you  
> don't know if you have a trapezoid.

But on the terminating side, it seems like the home proxy know there  
is another proxy because it needs to insert that into the route

(I don't spend enough time thinking about this so I assume you are  
right, just trying to make sure I understand)

> 	Paul

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