From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 15 Nov 2011 00:43:13 +0100 From: Antonio Quartulli Message-ID: <20111114234312.GA28724@ritirata.org> References: <4EC171B2.9070605@inti.gob.ar> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4EC171B2.9070605@inti.gob.ar> Subject: Re: [B.A.T.M.A.N.] Problem to find better Route 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: The list for a Better Approach To Mobile Ad-hoc Networking Hello Gabriel, On Mon, Nov 14, 2011 at 04:53:22 -0300, gtolon@inti.gob.ar wrote: > Hi. We are using batman-adv 2011.2.0 with Openwrt Backfire-rc6 on D-Link > routers, and we're making some tests with iperf to measure bitrate > capabilities between nodes. When we put three nodes aligned we notice > that the obtained bitrate between the extreme nodes strongly depends on > the batman path between them. To make it clear, we have: > > A ---------- B ---------- C > > With a dinstance of about 20 meters between A and B, and the same > distance between B and C. The problem is that sometimes, A and C get > connected directly in terms of batman-adv protocol (checked with batctl > o), and when that happens, the bitrates are very poor (less than 1Mbps), > like if B wasn't there. In fact we disconnected B and obtained very > similar results. > > Then we reduced tx power settings on A and C, forcing the B hop between > them, and we got much better speeds (~20Mbps). We've read about ELP and > think that maybe simple OGM messages are not good to measure link > quility between A and C in this example, could that be the problem? In > that case is there a way to fix this with actual batman-adv algorithms? > Thanks in advance! > > Gabriel > I think other people will give you better answer than this one, but just as start: OGM are sent in broadcast, which by definition uses a low rate that implies "better transmission than higher rates". Therefore a link having an high TQ doesn't necessarily has a good quality at "high rates" (as you are experiencing). In my opinion the problem resides in the fact that batman-adv uses broadcast packets to measure link qualities which leads to the aforementioned problem. I don't know if ELP would help in this sense because as far as I know it still uses broadcast packets. Please guys correct me if I am wrong. Cheers, -- Antonio Quartulli ..each of us alone is worth nothing.. Ernesto "Che" Guevara