Re: [Roll] ETX metric

[Henning Rogge <hrogge at googlemail.com>]

Am Dienstag 13 Oktober 2009 15:35:40 schrieb JP Vasseur:
> > So the question about a metric for ROLL should not only be "what's
> > the best metric for our networks" but "what metric is simple enough that
> > everyone can implement it on any kind of hardware".
> 
> I fully agree with your approach.
> 
> Yes, what we have done so far (in the new revision to be posted) is to
> define one mandatory metric (hop count) and have all other ones optional.
> May be "hop count" is one the one that we will keep as mandatory but the
> spirit is to have a set of metrics people can decide to use based on the OF.

OLSRv1 did the same way and it shaped the conclusion "OLSR is crap" or "OLSR 
does not work" in huge parts of the industry. Hop count metrics can be called 
"use worst link" metrics for wireless networks, because it tries to optimize 
for the LONGEST links possible, which will be (most likely) worst links your 
network knows.

With OLSR and 802.11 you can summarize it "Hopcount does not work in real 
networks outside the lab". There are some special cases how you can improve 
hopcount, but most times you will still get a poor performance and your 
protocol will be blamed.

Unless 802.15.4 is totally different (I don't think so) I would strongly 
suggest thinking about something better than hopcount for your mandatory 
metric. At least that's the message I can tell from OLSR.

Henning Rogge

-- Those who cannot learn from history are doomed to repeat it.

Attachment: signature.asc
Description: This is a digitally signed message part.