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Independant P2P Community Network Advice

Discussion in 'Networking Issues' started by bburley, Mar 9, 2007.

  1. bburley

    bburley LI Guru Member

    Hello to everyone!

    In my search for information, I ran across this forum and it seems like a very good place to ask my question :)

    I have a fair amount of experience with ordinary home networking, but I have a little learning to do when it comes to extended wireless networks.

    I am about to purchase a Linksys WRT54GL Router. I assume that it is virtually identical to the WRT54G v1 thru v4 (except for a little extra memory) as far as using third party firmware.

    My eventual goal is to start a community-wide peer-to-peer network which will connect a number of the homes of local amateur radio operators. This network will not likely include internet access (unless someone is silly enough to provide free access). It may be used as part of an emergency communications network and may involve such things as web pages, forum and file sharing software, VPN's, and maybe even an email server.

    My immediate concern is how best to connect these nodes? External antenna's will certainly be required and those shouldn't be a problem. I have read that WDS will cause severe bandwidth issues after only a few hops. Should I be using repeaters, bridges, or some other method?

    What about the possibility of dynamic routing for redundant paths? What happens as additional nodes spring up? I am sure I will have more questions but I will wait for some initial direction first.

    The hope is to keep the costs as low as possible to allow more to participate. Each location should be as independant as possible. Thanks in advance for any and all replies.
     
  2. frenchy2k1

    frenchy2k1 LI Guru Member

    What you are trying to do is called a "mesh network". It's a network where nodes talk to each other to establish the shortest connection and share their connections with each other (so each node is both a client and a repeater).
    http://en.wikipedia.org/wiki/Mesh_network

    Several projects have been open to convert the WRT54G routers to mesh network nodes.
    Here is the account of the creation of such a network:
    http://www.vdomck.org/blog/2005/07/22/how-to-build-a-mesh-network-with-wrt54gs/

    They are using freifunk, that you can find here:
    http://freifunk.net/wiki/FreifunkFirmwareEnglish

    Otherwise, DD-WRT with WDS has been used successfully to realize such a project too, as you said. Sure, the speed you will have wont be the maximum possible (as WDS reserves half the bandwidth for internetwork transmission), but it has been reported to work on large surfaces. Bandwidth shouldn't be too much of a problem (at least for web pages or email. P2P filesharing can be though), although latency could be (depending on the size).
     
  3. bburley

    bburley LI Guru Member

    Thanks for the reply :)

    Yes, your description "each node is both a client and a repeater" is accurate, but even further, "each node is a client, a host, and a repeater" might be even closer as each node should be able to serve web pages or other useful functions that could be dreamed up by the users. I don't see this network providing internet access, so finding ways to make it useful will be interesting projects for everyone after connections are established.

    The WRT54GL I am ordering seems to be the most versatile way for me to get my node up and running, and friefunk seems like a good choice with the use of OLSR. As I read more about this stuff I am starting to think that there are many ways that a node could attach itself to this network, even if efficiency and bandwidth are not optimum. My thinking could still be flawed, so if I write what I think will work, I will welcome any corrections or discussion.

    Even if I am running friefunk with OLSR, I think another node could connect just by running a single windows PC and a wireless card in ad-hoc mode. In this mode, the node should be a repeater, a client, and could even be a host if that PC were running server software.

    For those locations that are already running a wired or wireless network, the addition of a router like the WRT54G series would likely be the best choice. To use a wireless card, some form of routing or bridge would be needed and I am not sure that a windows based machine would do that very well. Some users may not be willing to figure out how to configure a linux machine to do that job.

    Nodes will be far enough apart that running an external antenna will be required for all but a very few of the locations. The simplest antenna would be an omnidirectional.

    Some locations will have to use directional antennas. I can't see anyone having to use more than two directional antennas to extend the network. Can a WRT54G series router be configured to run two separate links with two directional antennas while connecting to the users network through the LAN ports?

    What happens to the efficiency of a friefunk mesh network (running OLSR) when a wireless card in ad-hoc mode is thrown into the mix?

    If I can get nodes connected by whatever means available, the ability to use the network should provide some incentive to make improvements and experiment with network configuration. Even I will need a working link to test my ability to understand all of this :)
     

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