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From: Marek Lindner <lindner_marek@yahoo.de>
Date: Fri, 27 Jan 2012 23:54:25 +0800
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Subject: Re: [B.A.T.M.A.N.] [PATCH] batman-adv: encourage batman to take
	shorter routes by changing the default hop penalty
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To: Andrew Lunn <andrew@lunn.ch>
Cc: The list for a Better Approach To Mobile Ad-hoc Networking <b.a.t.m.a.n@lists.open-mesh.org>


Hi Andrew,

> Do you have any performance analysis to show this is really helpful
> and not harmful?
> 
> I've seen indoor results where i had to reduce the hop penalty,
> otherwise BATMAN was taking a short path which worked badly. By
> reducing the hop penalty, so encouraging it to take more hops, i got
> usable routes.
> 
> I see the danger here this could break working networks, so maybe it
> needs justification?

as a matter of fact I do believe it is helpful. In various networks (more than 
a dozen) I have seen that batman would largely favor multi-hop routes, thus 
reducing the overall throughput. By setting it to a higher value I regained 
some of its performance. The networks are still up & running - I can show them 
to you if you are interested.

So, you had to reduce the default value of 10 to something even smaller ? A 
hop penalty of 10 results in a penatly of 4% per hop. A rough equivalent of 2 
lost packets (62/64). Does not sound very much to me. Can you explain your 
test setup a little more ?

Nevertheless, this patch was intended to get a discussion going. The main 
problem I have been seeing in the last weeks is that OGM broadcasts have a 
hard time estimating the link quality / throughput on 11n devices. I'll also 
try to hack a proof of concept for an rssi influence on the routing and see if 
that has a better effect.

Regards,
Marek