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

[Cullen Jennings <fluffy at cisco.com>]

On Sep 15, 2006, at 1:42 PM, Paul Kyzivat wrote:

> Cullen Jennings wrote:
> > 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)
>
> Well, the terminating home proxy will know if it is including  
> another proxy after it. But it doesn't know if that proxy, or some  
> other proxy *it* includes, will R-R.
>
> And even if the home proxy isn't inserting a proxy (e.g. no Path  
> header registered), it doesn't really know if the contact that was  
> registered is the actual destination, or whether it identifies  
> another proxy.

Ok, but that seems like the advice should be "if you are using the  
path stuff (or the broken 3rd party registrations) to include another  
proxy, then you must R-R".  Making everyone R-R for no good reason  
just seems like a complicated wasted and will slow down systems that  
don't need it.


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