[OLSR-users] Metrics

[Andreas Petersson]

hello!

> 
> 1. Let's assume that we look at a path from node A to node B via 
> intermediate nodes and that we want to know the total metric of the path 
> in order to minimize it to find the best path. Then there are three 
> different kinds of metrics:
> 

there you are going into the field of true QoS, which leaves the area of 
routing with tables. you will have to decide on a per-packet basis, 
which route to take, since each packets defines his own contraints 
(delay, bandwidth, jitter).
some ideas how this could look are at
http://qolsr.lri.fr/.

even worse, to obtain the best route in a multiplicative metric 
environment, dijkstras algorithm does not work any longer. according to 
my graph algorthmics professor (prof. mutzel) you will have to resort to 
an algorithm that has a O(2^n) runtime :-(  or come up with a heuristic.

> implementation minimizes additive edge weights. The question now is 
> whether there is a way of converting multiplicative metrics and minimum 
> metrics into additive metrics in a meaningful way.

i don't think so.

> I think that the biggest problem is that you need a pretty big testbed 
> to test any modification to the employed metric. However, each 
> modification has the potential of completely breaking an existing mesh, 
> if the new metric turns out to be unsuitable.

some parts of our mesh are also routed statically, in a different 
subnet, which causes great pain in various body parts to configure. 
delpoying and later removing a potentially unstable olsrd would be possible.

greetings
andreas