From: Antonio Quartulli <ordex@autistici.org>
To: b.a.t.m.a.n@lists.open-mesh.org
Subject: Re: [B.A.T.M.A.N.] TTL yes, TTL no
Date: Sat, 26 Mar 2011 18:21:55 +0100 [thread overview]
Message-ID: <20110326172155.GA11235@ritirata.org> (raw)
Hello,
On sab, mar 26, 2011 at 04:31:42 +0100, Marek Lindner wrote:
>
> Hi,
>
> > In these days I was wondering whether the TTL field in the OGM packet is
> > really useful or not...Due to hop_penalty an OGM will be discarded as
> > soon as the TQ will reach 0 (which is a sort of TTL mechanism itself).
> > At this point why is the TTL field needed?
>
> uhm.., you probably are right. As long as there is a hop penalty it also
> functions as a TTL. Keep in mind that it is possible to set the hop penalty to
> zero. With the current default hop penalty of 10 the maximum number of hops is
> limited to 25.
I think it is wrong: TQ is not decremented by hop_penalty each time, but it is
multiplied by (TQ_MAX-hop_penalty/TQ_MAX), then the number of hops is
bigger than what you said. With hop_penalty = 10 we can probably reach
~135 hops (raw calculus 255*(TQ_MAX-hop_penalty/TQ_MAX)^135) =~ 0)
>
>
> > Someone could probably say that a node far at least TTL hops will never
> > be reached by a unicast packet, then it is meaningless to let it know
> > about me. But then it could be possible to recalibrate the TTL such that
> > it has to be equal to the maximum length in number of hops of the longest
> > path the OGM can traverse.
>
> Not quite sure what you are proposing. A TTL of TQ_MAX / hop penalty ?
>
Looking at the calculus above, I'm proposing to use TTL = ~135
Bye!
--
Antonio Quartulli
..each of us alone is worth nothing..
Ernesto "Che" Guevara
next reply other threads:[~2011-03-26 17:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-26 17:21 Antonio Quartulli [this message]
2011-03-26 17:45 ` [B.A.T.M.A.N.] TTL yes, TTL no Andrew Lunn
2011-03-26 18:15 ` Antonio Quartulli
-- strict thread matches above, loose matches on Subject: below --
2011-03-26 18:17 Antonio Quartulli
2011-03-26 18:01 Antonio Quartulli
2011-03-26 13:04 Antonio Quartulli
2011-03-26 15:31 ` Marek Lindner
2011-03-26 16:14 ` Andrew Lunn
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