Re: [B.A.T.M.A.N.] Node keeps switching back and forth

[elektra <onelektra@gmx.net>]

Hi Philippe -

fast switching of a route is a problem if does cause routing loops. I 
have verified in a 7x7 physical mesh grid that B.A.T.M.A.N. doesn't loop 
- ever. And - yes - particularly in my tests where I saturated the grid 
with several massive traffic  streams that were colliding in the center 
of the grid, B.A.T.M.A.N. was switching routes quite often (every few 
seconds).

I see therefore no point in adding hysteresis. If someone can show that 
there is an issue we can add hysteresis to the protocol.

cu elektra


> I tried that but I think it's only for switching from a gateway to 
> another gateway.
>
> My problem is for switching from an intermediate node, to another...
>
> For example, imagine a square where there's a node in each corner at 
> almost equal distance/signal quality (to keep things simple) with some 
> interference, and only one of them is the gateway, and the node 
> opposite to the gateway can't reach the gateway directly.
>
> That node (opposite to the gateway) has the choice between two nodes 
> to get to the gateway.
>
> In my/this case, it keeps switching from one to the other (since the 
> quality is almost the same on each). I guess it doesn't help keeping 
> things reliable for laptop connections behind... Playing with -r 
> doesn't seem to help because I only have one gateway node.
>
> Am I right?
>
> On 15-Apr-08, at 2:02 PM, Marek Lindner wrote:
>
>>
>>> As soon as signal from node2 to node1 goes down from let's say 250 to
>>> 240, if another connection to the gateway's quality is 241, it'll
>>> switch as soon as it hits 240... Then when quality comes back up to
>>> 242, it switches back to node1.
>>>
>>> I don't think it's very good to switch as soon as the quality is
>>> higher somewhere else, it should at least "give it a chance" by either
>>> having a threshold, or switch only if it's been in a more degraded
>>> state for more than x minutes, etc.
>>>
>>> Is there something I can do to influence that? Did I miss a command
>>> line argument?
>>
>> You can use e.g. "-r 20" to switch the gateway as soon as the TQ 
>> difference is
>> bigger than 20.
>>
>>> From "batmand -H":
>>
>> -r routing class (only needed if gateway class = 0)
>>          default:         0  -> set no default route
>>          allowed values:  1  -> use fast internet connection 
>> (gw_flags * TQ)
>>                           2  -> use stable internet connection (TQ)
>>                           3  -> use fast-switch internet connection 
>> (TQ but
>> switch as soon as a better gateway appears)
>>
>>                           XX -> use late-switch internet connection 
>> (TQ but
>> switch as soon as a gateway appears which is XX TQ better)
>>
>> Greetings,
>> Marek
>>
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>
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