Hybrid Community Networks?

CaryMenage asks: "I live in Philadelphia where there is a chock full of row houses and MDU (Multiple Dwelling Units) buildings. I was wondering if other Slashdot readers have been involved with community networks and what methods they have used. I have been looking at several different ways to distribute a T1 circuit to multiple end users; WiFi, Powerline, HomePNA. Due to the physical and legal complexities of older buildings and crossing public streets, I feel that some type of hybrid mixture of different topologies would work well in many situations. Has anyone implemented any of this on a large scale installation?" "I currently let my neighbor access the Internet through a powerline device that works well through the power meters. It seems to me that in theory, one could repeat the Ethernet with a cheap switch and send it to the next neighbor with another pair of powerline devices. Then when you have to cross a public street one could use a pair of Wireless Access Points in bridge mode. I also found a "leaky coax" product called RADIAX that I was wondering if anyone has applied this to 802.11. Seems to me you could use this coax and amplifiers to expand wireless coverage within buildings. For apartment buildings with somewhat organized main phone closets I have been looking at HomePNA products like the Xterasys HSM-1402 14-port HomePNA Switch and the Xterasys VX-110B for the end users connection."

Comments

Limited physical change

[jtev]

If there are restrictions on what you can do with wiring, wi-fi is probably a good idea, as long as you use encryption, such as WEP. if you can lay wire, ethernet would be the way to go, at least for a single building dwelling. having a WAP may be a good idea anyway, even if you can lay wire for those who want it, but it realy depends on your situation.

Re:Limited physical change

[dissy]

WEP isnt too useful for security, even for point-to-point links.

For something thats more or less a perm network structure, generally one way to do it is with older cheap boxes (IE p133's) that you can get say 4 of. (Two sets of two, one for each side of the bridge, and redundancy)
Throw in a wireless card, hookup your directional antennas, and run without WAP but use IPSEC over the two. Even simplier (But not as flexible or secure, the later of which is all that may be importaint here) is another simpler encryption wrapper and tunnel ppp over it between bridges.

If you go with something like a later p2 or higher, you can get other nice features such as boot from CDROM, USB support (boot from floppy and have root on the USB flash device) etc. Less moving parts the better.

Most PC wireless cards come in the form of a PCI card that you plug a PCMCIA laptop card into. If this expence is too high, you can still throw a second NIC in the box and crossover to a real access point, and just use the PC for the encryption. Simple wireless bridge devices, instead of full blown access point / routers will be better also. You can rely on linux/bsd security totally and not have to worry about people finding the AP's web interface and messing with it (God knows what exploits are available in those, or if their MAC filtering works right/fast, etc)

A p133 will easily handle two 10mbit nics, or one 10mbit nic and a 11mbit wireless card. Even 100mbit cards run mostly at full speed after you throw filtering on the interface.

Your only main worry with old hardware is its failure rate.
But if its that much older, you can hopefully afford 2-3 PCs for every one you need, so when something fails you have a backup on hand and can get things back up and running that same day.

wireless routing

[j1m 5n0w]

For a large wireless network, you'll probably want a robust ad-hoc routing protocol like aodv or dsr. Most cheap wireless access points don't support that sort of thing, though. Take a look at roofnet if you want to see what's possible. This is still an active area of research, though. Any success stories out there about large wireless ad-hoc networks?

-jim

Go All Wireless

[max born]

Don't know how much of a Linux user you are but I built a couple of wireless access points/relays for my neighbors that hook up the to the sflan network.

I used a couple of old junker laptops running Linux. This should be completely scalable to your situation. Here's a link to how I did it. For a relay/access point the same principle applies, just use two cards, one with a directional antenna the links to you, the other with an omnidirectional that serves DHCP. I found that cheapo cards on old hardware works great.

There are plenty of sites that have intructions for building directional antennas. From my experience you don't need to spend a lot of money for this kind of thing.

I'm glad your sharing your bandwidth. More people need to do this. Hopefully, one day the Internet will be entirely wireless and free. Free meaning you don't have to pay an ISP, you just buy your equipment and you're online. Just like CB radio.

Feel free to use my email address at the above site if you have any questions.

Re:Go All Wireless

[Oculus Habent]

I have a couple of thoughts & questions.

First, the questions:

What kind of security plans do you have? Is this to be firewalled from the Internet but an open LAN behind the firewall? Will each building/unit have a firewall?

How large an area are you looking at servicing? One street (both sides)? Two? A city block?

Are you setting up your own servers/services: Web hosting, e-mail, etc? Will everyone receive a live IP, or will it be private?

Next, some thoughts.

I would suggest firewalls. Sure, it's a pain - and an expense - to install at every unit, but it ensures security. If one of your users puts in an unsecured WAP, you aren't vulnerable. I would at least suggest it to each user. If they want to join the "network neighborhood", so be it. A $50 Cable/DSL Router should work splendidly, and transition to other services if a user desires.

Wireless is great for a dozen reasons; the biggest is convenience. If you do install wireless, I would recommend that the access points are 802.11g and support wireless bridging. The extra expense means no extra cables and the ability to expand the network quickly. You might also look into using directional antennas if you just want to bridge a distance. The directional antennas give you much better range and make it slightly more difficult for others to access your network. Encryption should go without saying. You might also consider setting up separate 802.11b base stations if there are many laptop users. 11b users will slow down an 11g access point.

For in-home wiring, it might be preferable to design a common "wiring cabinet" that you can tuck in a corner of the basement or mount on a wall. You can fabricate them identically and drop them into each house with a cheap eight-port switch, a surge protector with a swiveling plug (you have no idea how nice these are until you have one) and a little extra space for firewall/router, more switches, etc. to make installation a breeze.

You might think about a secondary Internet connection and a dual-wan router to improve speed and reliability of the connection. The expense isn't huge and additional bandwidth never killed anyone. :) The XiNCOM router handles specific routing and filtering, so as not to interfere with any servers you might be running.

Another Topology Method

[CaryMenage]

Since I didn't want to take up to many bytes, I left out an idea of taking over the coax cable from the cable company inside an apartment building (in most cases cable after the tap in a building is property of building owner) and create a cable modem network as well as an SMATV system, using cisco broadband equipment, multiple sat receivers and RF modulators, one per channel. The only problem their is the cost of the cisco equipment. So I wonder if anyone has succesfully used old cable modems, say one at a Linux box serving DHCP, DNS gateway etc.. and the end users with standard DOCSIS cable modems? Fiber is still to expensive to install.

Cat5 all the way baby.

[psergiu]

5 & 8 port switches are cheap. Shielded cat5 is cheap. Unshielded cat5 (for runs 70m inside buildings) is even cheaper. For jumps between buildings use some steel wire (the kind used for drying clothes is the best), secure-it and then wrap the cat5 around it. Ensure that the switches won't be rained on and that the power can't be disconnected accidentaly. If you have jumps between buildings larger than 10m use ProtectNet (or other eclators). If you want redundancy use switches that support spanning tree and create network loops. Is 100baseT, is cheap and it works.
See http://www.era.ro/ for an example.
There are almost 100 networks like this here in Bucharest.

Optical Air Link

[Maljin Jolt]

For many community nodes, CZFree network in Prague (and other czech cities) uses an optical light, but no laser(!) device called Ronja. Garage design by professionals, becomes a marketable technology after several years of experiments. Range of the two way direct visibility link is measured in kilometers, band is about 10M.

Here some links:

Home page
Some 64 existing deployments of the device
An example of installation in dense city area