Subject: [mobile-ip] [Fwd: Re: Eliminating Triangle Routing and RegReg: A Requirement? (RE: [mobile-ip] IPv6 Regional Registration - identifying requirem ents)]

From: Theo Pagtzis <[email-masked]>
Date: Thu, 12 Apr 2001 13:45:06 -0700

<mail access problems..resending>

Hi Jak,

   I agree with what you said, but I think we knew that as soon as the
notion of
LMM was coming into effect as a valid extension of base MIPv6.

I agree with the flexibility issue raised but I think that was a
fundamental
freedom in any LMM scheme I have read so far.

I also think that triangular routing is what it would look like, however
it would
not be suboptimal if the GMA/MAP is positioned at the border router. So
one leg of
the triangle goes away for sure. The border router is the only door to
the domain
so it will go through that anyway. Intermediate routes are transparent
(dynamic) so
we couldn't care less on these.

About the leg from the GMA/MAP to the MN:  I believe that the leg CAN
ONLY
correspond to the normal routing paths that the MN-bound traffic would
take without
RegReg. What else could it be? I cannot see any _non-normal_ routing
paths that
could possible come in effect and really become candidates for the
routing leg of
the mobility agent towards the MN.

We are arguing here on a "ghost" requirement about a tradeoff which is
the very
essence of the extension. I don't think we will ever catch that without
killing the
extension.

Theo

UCL/ Mobile Systems

Now apart from recognizing

James Kempf wrote:

> Phil/Karim,
>
> I think the problem is that both RegReg proposals currently reintroduce
> triangle routing. The elimination of triangle routing was viewed as
> one of the big steps forward with MIPv6. Granted, the fact that the MAP/GFA is
> topologically closer to the mobile node means that the size of the mobile-bound
> leg will be smaller. And, since the network engineer has complete freedom to
> place the MAP/GFA as they choose, it could be placed at a border router, where
> the mobile-bound packets have to come through anyway.
>
> I can't see much possibility for getting around this if the regional care
> of address is to remain unchanged. There is basically a contradiction
> between the major requirement of RegReg to reduce signalling over wide
> areas and the need for a binding update when the mobile changes care of
> address in order to eliminate triangle routing.
>
> Therefore, I think a perhaps better way to handle this would be to
> make sure that the RegReg hierarchical agent is designed flexibly
> enough so that it can be placed at any point in the network:
>
>         Recognizing that triangle routing is unavoidable if signalling
>         is to be reduced over a wide area, the RegReg protocol MUST
>         be designed such that intermediate agents/routers can be
>         flexibly inserted into the path of mobile-bound traffic such
>         that the triangle legs correspond to  the normal routing
>         paths that mobile-bound traffic would take without RegReg.
>
> Or something like that.
>
>                 jak