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)