From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4FDF7780.1040704@inti.gob.ar> Date: Mon, 18 Jun 2012 15:46:24 -0300 From: gtolon@inti.gob.ar MIME-Version: 1.0 References: <4FDA40A5.1050008@inti.gob.ar> <20120615095525.GA32707@pandem0nium> In-Reply-To: <20120615095525.GA32707@pandem0nium> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Subject: Re: [B.A.T.M.A.N.] link alternation when radios are not on batman-adv router? 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 Hi Simon, thanks for your reply! El 15/06/2012 06:55 a.m., Simon Wunderlich escribió: > On Thu, Jun 14, 2012 at 04:51:01PM -0300, gtolon@inti.gob.ar wrote: >> Hi, >> >> we are interested too in interface alternating, so we made some >> tests to understand how it works. As you can see on the attached >> sketch.png, we connected two pair of routers using their ethernet >> interfaces, E6 with E7, and E8 with E9. All of them have eth0, and >> an ad hoc interface, wlan0-1, managed by batman. E6 and E8 are in >> channel 11, whereas E7 and E9 are in channel 1. Besides we used two >> other routers, E12 and E13, both in channel 11, with their tx power >> set to just 0 dbm, to avoid a direct sight between them. >> >> Then we sent traffic from E12 to E13. We expected that packets >> travelled from E12 to E6, and that E6 forwarded them to his eth0 to >> use the interface alternating feature, making traffic flow to E7, >> then E9, E8 and finally E13. But instead, we observed that the >> actual path was E12--E6--E8--E13. The resulting routes for each >> router are attached in a text file, and also the graph from the >> batctl vd dot command. >> >> After this result, we read again the thread mentioned by Guido, >> specially in this part: >> >> https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2012-March/006344.html >> >> And if we understand correctly, the alternation feature works >> after the batman path has been selected. So in our case, E12 looks >> at his table to know where to send a packet to E13, and finds E6. >> Then E6 receives the packet and looks in his own table, finding that >> the best path to reach E13 is E8. At this point, the alternating >> should work, but there's only one interface directly connected to >> E8, so the packet goes there, and so on. We think that if E6 and E7 >> were not two different routers running batman-adv but they were two >> radios of the same batman-adv router, and the same for E8 and E9, >> the alternating would work, because the unique router would choose >> the best path, and then would find two possible interfaces to the >> same next-hop, changing the interface. > This is entirely correct - batman-adv has only one link to choose from > (E6 -> E8) to reach its best nexthop E8, so there is no way to > "alternate" the interfaces. > >> We'd like to know if this interpretation is correct, and in that >> case, if it were possible to use interface alternating in a case >> like this, with two routers connected to work together. Thanks! > Mhm, with the current implementation - no, unfortunately not. We would > need some kind of multipath routing to select between routes, this is > much more complex. Ok, i understand. > > An alternative might be to use the routers E7/E9 as secondary routers > without batman, but only forwarding traffic between Ethernet and > WiFi. Then the "primary" routers (E6 -> E8) would think they have > an alternative route via Ethernet (because they don't see the > intermediate hops E7/E9). This comes with some caveats however, e.g. > 4-addr mode in Ad-Hoc, you need some very simple ethernet forwarder, > and most probably other things I forgot. We had tried with something like that using ap and sta modes in E7 and E9, and it hadn't worked. Thanks to your suggestion we noticed the necessity of the 4-address mode, so we are now trying with wds: http://wiki.openwrt.org/doc/recipes/atheroswds Unfortunately, we haven't found yet a way to use 4-address mode in ad hoc. Apparentrly, it's not possible: http://linuxwireless.org/en/users/Documentation/iw#Using_4-address_for_AP_and_client_mode Best Regards Gabriel