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

[Vigneswaran R]

On 06/14/2013 12:42 PM, Henning Rogge wrote:
> 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.

Oh, yes. It just saves B from getting some traffic by routing through E. 
However, after that the remaining path is same (C,D,H).


Regards,
Vignesh