Re: [RRG] Geographic aggregation-based routing

["William Herrin" <bill@herrin.us>]

On Fri, Jul 11, 2008 at 7:05 PM,  <HeinerHummel@aol.com> wrote:
> My understanding of what you want is this: forwarding from C to B is not
> allowed. Hence the packet from D to E must go like
> this: D--->C-->G-->F-->E    and NOT D-->C-->B-->F-->E.
> My saying is: That can be respected. But this is almost normal Dijkstra.Only
> the following enhancements are required: Build a graph, which consists of
> these nodes A,..H and of directed arrows. Between any two nodes according to
> the black lines there are two  inversely directed arrows.Except  between B
> and C. Here there is only one arrow which is from B to C, but not from C to
> B.
> Node C runs Dijkstra with itself being the root, however modified such that
> selecting a predecessor node for any node presumes that  there is an arrow
> from that predecessor node to that "any"-node. So , while running Dijkstra,
> C won't even see that B is a neighbor/candidate.Hence the resulting shortest
> path tree will not include "from C to B" but only "from C to G".

Okay. I added what I think you just described in red at
http://bill.herrin.us/network/geoag-h1.gif. Is that correct?

This means that the forwarding information base at node G looks like:

destination {left area}: send to F
destination C: send to C
destination H: send to H
destination D: send to C

And the FIB at node C looks like:

destination {left area}: send to G
destination G: send to G
destination D: send to D
destination H: send to G

Is that correct?

So, D--->C-->G-->F-->E happens for packets from D to E because when
the packet is at C, C understands that all of {left area} is available
via G and when the packet is at G, G understands that all of {left
area} is available via F. Thus geographic aggregation cut the FIB
almost in half since C and G only have to keep track of {left area}
instead of keeping track of A, B. F and E.

Still correct?

-Bill



-- 
William D. Herrin ................ herrin@dirtside.com bill@herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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