[Olsr-users] getting second best route from dikjstra's algorithm

[Henning Rogge]

On 06/14/2013 09:07 AM, Vigneswaran R wrote:
>    +---- J --------- K -------+
>   /                            \
> A --- B --- C --- D --- E ---- F
>         \                      /
>          +-- M -- N -- O -- P-+
>
>
> You're right. In the above scenario, A thinks that B,C,D,E,F is the
> second best path. However, as far as B is concerned, M,N,O,P,F is the
> 2nd best path. When we apply policy routing uniformly on all the routers
> to use 2nd best path (for a particular traffic), traffic from A to F
> will flow through B,M,N,O,P,F instead of B,C,D,E,F (and which remains
> unused).

It might be even worse. Think about a network like this:

   B---C---D
  / \ / \ / \
A   X   X   H
  \ / \ / \ /
   E---F---G

A might decide that A-B-C-D-H is the best path and A-E-F-G-H is the 
second best one.

But E decides that E-F-G-H is the best one and E-C-D-H is the second 
best one, pushing the traffic back onto the best path from A to H.

Henning Rogge
-- 
Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
Fraunhofer Straße 20, 53343 Wachtberg, Germany
Telefon +49 228 9435-961,   Fax +49 228 9435 685
mailto:(spam-protected) http://www.fkie.fraunhofer.de

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