thanks Michailis, this was very helpful On Wed, 2008-03-05 at 22:46 -0500, Michail Bletsas wrote: > > > Bryan Berry <[EMAIL PROTECTED]> wrote on 03/05/2008 03:07:12 AM: > > > Michailis, thanks for your quick reply > > > > > small schools, the school server is all that you need. In the > > > meantime, APs with controllable WDS behavior are recommended. > > > > I am not an expert on access points. Can you suggest a particular > model > > that meets this criteria? > > Bryan, > > The problem is mostly obvious on consumer APs with Broadcom radios > (the Linksys WRT54 being the most common) and is not an XO specific > problem anymore. > Any application that generates multicast traffic will trigger storms > in environments where many such access points are deployed in the > vicinity of each other. > Most enterprise Access Points will work just fine because they allow > for fine control of WDS. > Since we assume a limited budget here, I will stick to consumer and > prosumer grade gear. > A good starting point should be the DLINK DWL-2100AP which uses an > Atheros Chipset. > > > > > > > > >The solution to that problem is to be able to turn off WDS. The > stock > > >Linksys firmware doesn't do it, however OpenWRT and its variants > can do > > >it. > > > > I am not familiar w/ OpenWRT and its variants. Similar to my > previous > > question, is their an off-the-shelf AP where WDS can be disabled > w/out > > having to load OpenWRT? > > The reason that I mentioned OpenWRT, DD-WRT etc. is that the Linksys > WRT54Gx is the most popular AP that I know off. > Avoiding them completely will be hard ;-) In many models (the ones > with 8MB of RAM) loading DD-WRT is trivial. > > > > > > To Mesh or not to Mesh? > > Using regular access points, is there actually a mesh network at > all? It > > sounds like we are back to using a regular 802.11 g network. Jabber > just > > emulates the features of a mesh over a regular network. > Let's separate the mesh transport (802.11s-like layer-2 transport) > from the collaboration middleware (jabber, avahi, telepathy). > They are completely indepedent and as you point out the applications > will run on any transport. > > > > > > We were really excited about kids using the mesh to connect to the > > Internet from their own homes to and each other via the mesh at > great > > distances. Is this dream currently not a reality? If it is not > currently > > a reality, when can we expect it to work? > > When we started OLPC, we thought that the mesh would have two main > uses: > > * extending the range of access points (via multihopping) > * enabling p2p ad-hoc collaboration for small groups without any > infrastructure > > We had the first scenario working very early on. Every time one XO > connects to an AP, it acts as a gateway for other XOs via its mesh > interface. > Then we disabled that functionality (by means of stopping the gateway > script from running in the XOs - very easy to reenable) for a variety > of reasons, the most important being that we wanted to focus on school > server operation and having multiple gateways (MPPs - mesh portals) > under the same roof, doesn't agree with the current state of the > collaboration software. > > The second scenario works very well now for small groups (<10). Since > it relies heavily on multicast and since the mesh currently implements > multicast as a controlled flooding, it won't scale to larger numbers > of nodes until we address one of the two (or better both) issues. > > Add to that the fact that the mesh is inherently more chatty due to > its control traffic, and you realize that when you care about how to > stuff the maximum number of nodes under one roof (pushing the limits > of what people can do with WiFi in general), using the mesh where you > can easily use access points is a very suboptimal choice. There is no > need for multihopping inside the school. > > > > > > Two Networks? > > Should we use AP's for the school but then also use Active Antennas > so > > that kids can connect to the Internet from home via the mesh? > You could do that, you can also enable MPP functionality on the > laptops, so that the kids who are closer to the school connect via > WiFi to the school and via the mesh interface to other XOs downstream > from them. > > > > What is ironic is that we didn't want to offer many choices to the > users (so that they don't get confused) and that lack of control is > giving us many headaches right now... People who are command-line > jockeys can do very ellaborate setups with the XOs. We have to expose > those capabilities to the GUI too. > > > M.
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