[Olsr-dev] [OLSR-dev] OLSR for Windows Mobile platforms by Moviquity

[Henning Rogge]

Am Wed July 15 2009 15:06:31 schrieb sebastian sauer:
> in general it's not trival to find a suitable metric for a highly dynamic
> "loss network" like our mesh nets.
ETX is a very "primitive" sollution for this and there might be better 
metrics, but it's easy to implement and depends only on layer 3.

> hop count and ETX has some nice properties like "monotonicity" (some papers
> call that "isotonicity" -- dunno why.)
Isotonicity is a little bit different I think.

Isotonicity means that if a path between two nodes A,B is the shortest path by 
a certain routing metric, any shortest path between nodes on the patch A,B 
will lay on the path between A and B. This is a very important assumption for 
hop-by-hop routing.

> in practice things are even thougher -- none of the bigger OLSR mesh
> setups work without ETX cheating. Hence on guarantee that the metric of
> any randomly chosen path is really monotonic -- in a real life setup.
What do you mean with ETX "cheating" ?

> yep, hop count is an idiotic choice for a dynamic "loss network". because
> the bandwidth of the "edges" / links is not stable over time.
Let's say it was a decission done in a time where noone had experience with 
large scale networks outside the simulator.

Henning Rogge

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