[Olsr-users] Using different LQ algorithms

[Henning Rogge]

Am Tuesday 03 February 2009 14:01:38 schrieb ZioPRoTo (Saverio Proto):
> > Depends on the LQ algorithm you use.
> >
> > etx_float and etx_fpm use an exponential moving average, so they consider
> > an "infinite amount of hellos".
> > etx_ff considers all OLSR packages (not only hellos) within the last 16
> > seconds.
>
> Ehm ... I read this email and I got pretty scared :)
No need to be scared.

> At Ninux.org we have some tens of nodes speaking OLSR, all with
> different versions. From 0.4.x going on up up to the latest shipped
> with the trunk of OpenWRT.
>
> Last weekend I went to install a new node, and OLSR was acting really
> funny with a neighbor node that was shipping and older OLSR version.
There are a few bugs in the old (pre 0.5.6 olsr) ETX logic, so I would not be 
surprised to see strange results with old versions.

> At this point my question is:
>
> I always believed that different versions of OLSR where supposed to
> work consistently, but now that different algorithm are implemented,
> are different version still compatible ??
all three algorithms calculate the same ETX value. The problem is that the old 
OLSR implementation has a REALLY bad scheduler, so the hello timeouts are not 
okay (sometimes hello packages come more than 50% too late).

So you might see strange results.

etx_ff should do better with old olsr versions I think.

> What is the default
> algorithm assuming standard config file ?
etx_fpm for 0.5.6, etx_ff for the development tree.

Oh, the next mayor update (most likely 0.6.0 or 1.0.0, not 0.5.7) will have 
additional link layer aware metrics that will be DEFINITELY incompatible with 
the old ETX value... but they won't be activated as a default metric.

They will be not in 0.5.7 because we need time to test the new linklayer aware 
metric system. But there will be an OLSR version in the future with real ETT 
support.

Henning

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