On Sun, Jun 08, 2003 at 01:16:33PM -0400, [EMAIL PROTECTED] wrote: > Is it true > that tcp over a 3 hop mesh network link generally works at 15% of expected > throughput (due to tcp's poor performance in the face of packet loss and > latency).
I think it is reasonable to expect less than 2Mb/s in one direction over three 802.11b hops, even before TCP overheads, if you use one radio per node. This is simply because 802.11b is half-duplex. If you add one or two more hops, you will see some overhead that CSMA adds to a multihop network, the term for which I think is the "exposed node problem." Add in unfairness in the 802.11 MAC, near-far problems, and so on, and you see that 802.11b is a crummy radio technology for building multihop, ad-hoc networks. That does not keep some of us from still trying, though! I think you can triple that speed by using two 802.11b radios attached to two omni antennas, provided that you tune the radios to non-interfering channels and you make the right choice of routes, HOWEVER 1) The right routes are essentially the ones that minimize co-interference of TCP packets on the same path. No distance vector algorithm will be able to do that. I think that a link-state algorithm can do an adequate job at it. 2) I am not at all certain that two 802.11b radios tuned to different channels will not STILL interfere with each other, even if they are tuned to opposite ends of the spectrum, when their antennas are on the same mast. Can anyone say anything about that? Dave -- David Young OJC Technologies [EMAIL PROTECTED] Urbana, IL * (217) 278-3933 -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
