From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sat, 26 Mar 2011 18:21:55 +0100 From: Antonio Quartulli Message-ID: <20110326172155.GA11235@ritirata.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Subject: Re: [B.A.T.M.A.N.] TTL yes, TTL no Reply-To: The list for a Better Approach To Mobile Ad-hoc Networking List-Id: The list for a Better Approach To Mobile Ad-hoc Networking List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: b.a.t.m.a.n@lists.open-mesh.org 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