From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sven Eckelmann Date: Thu, 5 May 2011 20:26:41 +0200 References: <201105051935.12979.sven@narfation.org> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1474908.x8f2loUKKS"; protocol="application/pgp-signature"; micalg=pgp-sha512 Content-Transfer-Encoding: 7bit Message-Id: <201105052026.42719.sven@narfation.org> Subject: Re: [B.A.T.M.A.N.] Routing decisions 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: Ed Okerson Cc: b.a.t.m.a.n@lists.open-mesh.org --nextPart1474908.x8f2loUKKS Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Ed Okerson wrote: > On Thu, May 5, 2011 at 12:35 PM, Sven Eckelmann wrot= e: > > Ed Okerson wrote: > >> On Thu, May 5, 2011 at 10:44 AM, Marek Lindner > >=20 > > wrote: > >> > Hi, > >> >=20 > >> >> We are evaluating using Batman in an environment where there could = be > >> >> 200-300 devices in a single building. We started out setting up 10 > >> >> devices in our office to figure out how everything works and do some > >> >> throughput testing. We have noticed that the routing decisions > >> >> always send the packet to the node towards the destination with the > >> >> highest signal strength. This causes the packet to always traverse > >> >> the network with the maximum possible number of hops, which causes > >> >> performance to degrade quickly. Is it possible to use a different > >> >> routing algorithm? It would seem that sending to the node closest > >> >> to the destination that the source node can still communicate with > >> >> directly would minimize the number of hops. > >> >=20 > >> > if you wish to minimize the number of hops you have to increase the > >> > hop penalty. Check the "hop penalty" section here: > >> > http://www.open-mesh.org/wiki/batman-adv/Tweaking > >>=20 > >> That seems to indicate that it is a per node setting, i.e. "using this > >> node will incur a penalty of x". That is also not the desired > >> behavior. For our installation all nodes are in a fixed location, so > >> using a particular node as a next hop in the route may incur a penalty > >> for one source node, but not another. This should be dynamically > >> determined for each route from each source to each destination to > >> minimize hops. > >=20 > > So you have to increase the hop penalty everywhere to force the routing > > algorithm to reduce the number of hops and prefer worse routes with less > > hops. >=20 > If I increase the hop penalty on all nodes, they will all still be > equal. If all nodes have a hop penalty of 128, will it not make the > same routing decisions as it does if they are all 10? No, the wiki explains it quite well, but I'll try to explain it a little bi= t=20 different. Lets assume that you have perfect links (quality =3D 255) betwee= n all=20 nodes in a route. Each one would say: "hey, I can reach the following=20 neighbors with the quality of 255".... now introduce a penalty in each hop = (10=20 for example) which is just substracted from the incoming value. So after a= =20 distance of 5 hops only a quality of 205 would be announced. Therefore a no= de=20 with only a distance of 2 (quality =3D 235) would be prefered as next hop i= n=20 this case and not the one with the distance of 5. Target - X1 - X2 - X3 - X4 - X5 - (Announces route with quality 205 to Targ= et) \ \ Y1 - Y2 - (Announces route with quality 235 to Target) This is a quite abstract and not 100% correct explanation of the hop penalt= y,=20 but should help to understand the implications a little bit better. You hav= e=20 to do the calculations yourself to find a good value for hop penalty. You should have a look at send.c to find more information about it. You sho= uld=20 see that it is not really substracted in a linear fashion and that the actu= al=20 quality is calculation is also more complex,... but the idea is similar to = the=20 example mentioned before. Kind regards, Sven --nextPart1474908.x8f2loUKKS Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABCgAGBQJNwuvhAAoJEF2HCgfBJntG0JQP/RfdEvbhKs+R97vdY3qeBX0m QOZqm9dLr9bWOXGalK4oq8BTAiChwlxKy8oKFtSaDLOyCfukGOpms7MZBuO4/7jF AfWzMN/egde1XMj+rlIJ6j0mc19Aa9kCkfBBYFosbR9sFOVKKr6JM+Q9bZ0yWNVa b6yrKmeUGNC5poKEFsVdXl4zNh4r2sWEvKJKdWgHmBRD40MZdzHKmEMhkTdKD4qg t6GnuXe6XQLvxXfJFFFvu3e6uveI37eR/u8jG/qnSY1vZf8rj9UdRS46jVEuArN5 7kHnm9zZbfr62SjC6kuyH9s3aGxgVPu2lAEwhQtW+SYJFNZSyXSQ91D2n4mFAMb1 B0lI2lqNvzf61TXJ0uKuyNCCs0JdiYJT7kvLhfd2YKInI57NNyU0awPencM7YpD7 EL0Rk05bMZZOkXYDIyChTKqN+JWbxlX0XwO3RlsVhY+bnZtyiHahlMrWR8eYeqs5 zfCeNIcSTXUUwjxD8qSMjsCG6GHtUTIPY7NNU+nXhuCRXDeFwlVm21xMGsO5Xw7m B4bZQGYYuTeyo5BlQws4O5NPUk2yv8QlqbGR5M7WrWncbiXxetOsSaqfRoLe32Il xEY+jI+iMdjzk/qFQnEqdwdT5MgkegUfIm/Iae+X4WKT/jc79ro0EQi+eS8F0WgG /yFs4hJsA8ZDGpTBl/TW =XxDn -----END PGP SIGNATURE----- --nextPart1474908.x8f2loUKKS--