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Building a Wireless Network for an Apartment Complex?
itwerx asks: "I've been asked to design a wireless infrastructure for an apartment complex. Tenants will pay an 'access deposit' and a monthly surcharge to get a PCMCIA/PCI/USB network card along with free installation and, of course, wireless Internet access. The buildings are arranged such that 2 WAP's per building should cover all the tenants (one WAP per side, far enough away to get line-of-sight through the windows). I do have a few concerns, however. All help is appreciated and when we're done we'll put up a HOWTO!"
"My concerns are the following:
- Interference between WAP's (there's several buildings) - there are enough channels if we go 802.11a but cost is a concern.
- Management of 'hitchhikers' - we're planning on manual assignment via DHCP/MAC address for tenants with others having all their HTTP requests get directed to an info page. Anybody done something different?
- Interference from WAP's and other devices that may be owned by tenants! Should we just avoid the default channel and hope for the best?!?
Interference between the two WAPs is not really what you have to worry about. Put them on different channels on opposite ends of the chunk of 802.11b spectrum and its done.
The real issue is interference from other devices. I hope no one has a 2.4GHz phone.. or a microwave.. or X11.. or one of the other dozens of devices on the (unregulated) 2.4GHz band. It can knock your 11Mbit down to 1.
Using your sig line to advertise for friends is lame.
mac addresses are fairly easy to spoof (at least in OpenBSD), and any two-bit prism based sniffer can tell the mac addresses of other nodes on the network. It would probably be better to go with a different scheme, such as login/passphrase authentication, rather than MAC address. I know UC berkeley is using some sort of program like that check out Calnet
- 802.11 manages devices in a friendly way, and is designed specifically to play nice with lots of other 802.11 devices in the area. In fact, infrastructure networks assume it WILL work that way. Put your entire complex on one SSID and one channel - each WAP will form a BSS, and devices should seamlessly roam between them.
- Other peoples' devices shouldn't interfere with yours unless there is a LOT of devices. If they do, too bad for them, they can choose a new channel. Or you can choose a new channel. But it shouldn't be a problem unless there's a ton of networks.
- I would suggest leaving your network entirely open (no WEP, etc.) then putting a router at the edge which authenticates MAC/IP addresses, provides DHCP, and only routes those who enter a password of some sort. This leaves the internal network open to hackers unfortunately, but WEP management for an apartment will be hell, and the alternate solutions all tend to be non-standardized.
I am an assistant network engineer at a large midwestern university. Currently, like you we're in the process of figuring out how to deploy wireless access points. Our campus's Engineering Computer Network let us borrow a mobile testing appratus that has a WAP and an Antenna on it (looks like a camera tripod). We take it to different parts of our residence halls and, with a laptop, we take SNR readings from different parts of the surrounding rooms and record our measurements on the building blueprints. We figure we need about 6 WAP's to sufficiently cover the lounge areas of the older dormitories (with their steel and concrete infrastructure), but for your sake 2 WAP's should sufficiently cover a medium-sized apartment building and more. We also plan to cover several large outdoor areas, a library, and our Union right off the bat. The equipment we are using is Enterasys Roamabouts ($1000 a pop), [link] and they are highly configurable and have a ton of management features. We figure each WAP will get connected to a switch port on the Cisco Catalysts in our buildings. So far, we haven't done much in terms of the deployment because it is a long process, where the Physical Facilities department has to do the actual installation of the equipment, data jacks, etc. I assume in your case you can better coordinate this without all the red tape. We figure that by the time these are all installed and our userbase is well-informed of the network, we will have a great system that will scale to thousands of students and staff in the future.l
http://www.purdue.edu/ITaP/projects/wireless.shtm
U.C. Berkeley has been working on implementing a wireless network around campus. You can read up on the project here. It mentions some of the technical issues they face like 2.4GHz cordless phones and even interference from old microwave ovens.
If you are worried about data sniffing, IPSec / WEP is your answer. If however, as I assume, you are worried about "free rides" on your bandwidth, I'd suggest PPPoE. That way no one gets on the network unless they have an account. Seeing how it is a relatively small number pf tenants I assume (less than 500 or so) it should be simple to keep a list of names / logins so as to provide a tenant with two logins should he get a second PC. This method saves you the hassle of managing a bunch of fixed IPs and MAC addresses with everyone on the network.
I hope this helps. Our wireless guys pulled this off in 130 buildings over a several square kilometer area. Good Luck!
PS. Cracks about Redneck Rocky Top and such ilk should be modded -1!
Comparing it to Windows will be a moot point, since El Dorado is going to have a 40% larger code base than XP.
Back at my alma mater, one of the students (who thought he was clever) founded an ISP that provided 802.11b wireless access to apartments on campus. Inevitably, the WEP key he used was compromised, and student account passwords were sniffed and abused. Now, common sense would dictate that he shouldn't be responsible for what a criminal does with his network; but common sense does not reign supreme in the ivory tower of academia. What happened next was shocking: the student was disciplined, expelled, and sued for damages by the state college. Although he certainly could have won his case in front of a jury, he settled because he could not afford $15k to hire a good trial lawyer. Right now he has no degree, can't get into a good school, and is pumping gas for a living.
So, if you are considering rolling out a notoriously insecure network architecture (such as 802.11[ab]), consider the fact that you may be personally liable for anything bad that a crook does with your network. Be afraid.
df
Its not really spoofing as such. Anyone can change their MAC identification to anything they want with most cards. in linux you do it through ifconfig and in WindNT/2K/XP you can do it in the network control panel. This is another reason I would go with PPPoE or a VPN.
I've worked with Karlnet's stuff. It does work as advertised, but in my opinion it is not at all worth the cost (something like $500 per base station *for the software* and $25 per client). In addition, I have never ever seen their Linux driver work. They supposedly came out with a new one recently, but I haven't heard good reports about it either.
Aside from all of that, Turbocell does do some neat stuff: bandwidth throttling on the client end, key-based authentication, and it supports hidden nodes on wireless networks. It seems more suited for "wireless ISP" type of arrangements than smaller rigs as described in the article.
To Karlnet's credit, they also now have a $75 version of their firmware that goes on an RG-1000 and allows for one or two wired ethernet devices. Still more than I prefer to pay for such things. And of course, your milage may vary.
are you just the fix-it guy that has computer knowledge, or a private contractor?
if you are expected to stay in house and manage the thing once it is up, get ready for a lot of sleepless nights and angry users.
it is probably MUCH more cost effective for the complex to just pay for the DSL in all the buildings and keep them hooked up forever. ~$60 a month including a phone line and you have no hassles what-so-ever. then pass the cost onto the tennant
your month cost per tennant will probably be $20-30/month in hardware depreciation and bandwidth usage. plus you would have a HUGE (you didn't give building or unit numbers so i'll guess) setup fee of $10,000+ assuming you get a couple T1s and all the wireless hardware.
as a tenant i won't pay you more than $50 a month (standard DSL cost) so you have to figure out if you can provide all this service and not spend $20 a month per user of your time. i don't think you can.
MARIJUANA, SHROOMS, X: ONLINE?! - E
There's several ways to go about this.
- Buy CheckPoint FireWall-1 in addition to your access points. There are SOHO versions of FW1 on dedicated hardware (e.g. Nokia IP71) that retail for less than $1000 and can accomodate up to 50 users. Use its Session Authentication agent to arbitrate access to anything other than DHCP and don't bother with enabling WEP. Unfortunately, the agent seems to be only available for Windows 9X/ME/NT/2K/XP.
- Buy Cisco access points and Cisco ACS software and enable LEAP. While non-standard, you are probably forcing them to buy a wireless card anyway, and Cisco's client devices aren't all that expensive. The Aironet device is supported in Windows and Windows CE, Linux, and MacOS 9.x and 10.x. My employer uses LEAP and it works great.
- Hack your own. Set up Linux and Squid and Apache and transparent forwarding to redirect unauthenticated web traffic to a HTTPS login form. Have the form automatically add the necessary firewall rules to allow them out, and have a cron job remove them after a delay. Upside: A five banana problem once you've mirrored enough of CPAN to write the Perl scripts. Downside: Easily spoofed/hacked with a copy of AirSnort, Kismet, and Ettercap.
WEP key management sucks so hard that relying on it is stupid. I'd probably go the LEAP route just because it is so damn easy on both the client side and on the server side, even though I hate Cisco. The build-it-yourself solution would be a complete kludge and would be totally unsupportable except by the author, i.e. lots of work. The CheckPoint firewall is in between the Cisco (easy) and do-it-yourself (really hard) in terms of difficulty.Anyway, I'm rambling now, so hopefully this helps and makes sense. If you have questions, post 'em here.
I'm proud of my Northern Tibetian Heritage
Wireless network that spanned several different buildings, and required a few different AP's. Toughy, but not impossible. First, set each AP on its own channel. Second, enable MAC Address security for each Card on the network. Then instead of using DHCP to give out IPs you should assing each computer an IP and Subnet mask. Turn off DHCP server on the AP to try and stop any hitchhikers. The next thing you should do is enable WEP on the AP and the cards. Use the highest possible key. This should keep most of the standard users out of the network and force them to pay. As far as hardware, I suggest Linksys cards as they allow for the "any" SSID to be used allow each resident to use the best AP. Also, for desktops use USB so that you dont have to open up the computers. That could be a BIG liability for you and your employer. Only use PCI cards if they sign a letter releasing you from all liability. You can do this on 802.11b for the cost reasons. If you need further help with this project email me. If this works out please let me know.
LowneWulf states:
To which MarkKomus replies: LowneWulf states: Which is rebutted by MarkKomus: I need to know who has more money or a bigger house so I can know who to believe!Pick up Hacker's Challenge. They detail 20 real life attack scenarios, many of them are attacks against a wireless network, and the detail the steps taken to prevent attacks of that nature.
I don't know if it's been mentioned, but I would use IPSEC if I were you,
simply because 802.11a/b sniffing is trivial now and mac address spoofing is
even easier. Also, I would probably recommend against going with an
established commercial wap product, as they all almost definately aren't going
to have the flexibility you need in the future and are probably way too
expensive. I would roll a couple of OpenBSD boxes with wireless cards, that
way you have an all in one solution with lots of nifty stuff like traffic
shaping per mac, monthly bandwidth accounting capablities via pf, syslog, and
tons of other stuff that commercial vendors just don't offer. And I do mean,
don't offer, regardless of price. This page
offers a good howto regarding ipsec on openbsd and this page
give a pretty good read on replacing wep with ipsec on openbsd as well. Good
luck.
SealBeater
-- Its survival of the fittest...and we got the fucking guns!!!
The whole point about using wireless LANs is to enable environments where you either need to support roaming/migrant users or you have little/no control over the local infrastructure.
Neither is the case here.
You also need to remember that the 11MB/s provided by WiFi is shared between all users. If you have 50 "dwelling units" and two WiFi access points, you'll be offering a service with less maximum bandwidth than bottom-of-the-range xDSL... and you'll be charging for $100 WiFi NICs instead of $10 PCI ethernet NICs (which many PCs now have as standard anyway)... and for a service subject to atmospheric outages (ever use a WiFi network during a thunderstorm) as well as interference from a multitude of other devices like microwaves, cordless headphones and DECT telephones...
I'd recommend taking a bit of up-front hit and running CAT5 to each apartment. Put a switch on each floor (unmanaged 16-port switches are less than $80), and run each floor-switch to a central switch, and from there to the T1 router, squid server and whatever other infrastructure you've going to value-add into the equation.
This is what business-class hotels now do - just provide an ethernet RJ-45 jack and a DHCP server... all a guest has to do is plug in, configure for DHCP, and reboot.
If nothing else, support costs for a wired network are trivial... but for a WiFi? How do you explain to a user that they can't get their mail because the guy in apartment 2B is listening to a CD?
This sig left unintentionally blank.
WEP is weak. Especially in situations where there is a lot of use and lots of bits flying around. All that one needs to do to crack a WEP key is accumulate data sent using said key.
;) ;)
See: AirSnort
Rather than worry about people having their sh*t sniffed, here are a couple other solutions:
#1. Set up a portal that uses HTTPS and fetches web pages for the user, then presents these pages to them.
Pros: Simple
Cons: Doesn't really work all that well with some sites
#2. Use IPSec
Pros: Damn secure.
Cons: CPU intensive, limited software support outside of the OSS crowd.
#3. Keep it insecure, but keep the users educated. Let them know their data may be sniffed easily, but also let them know what HTTPS is. Show them how to sign into their Yahoo mail so that their password won't get sent in the clear, etc etc.
Pros: Cheap
Cons: Depends on the intelligence of users. You never want to do that
I setup a small AP in my apartment, only used by me, so far ;)
I used an old 486 laptop running Linux 2.4.18 (RedHat base) with an Orinoco Silver card, using 40-bit WEP (which to a cracker, is slightly inconvenient at best) and IPTABLES, MAC filtering with IPSEC 3DES and 1024-bit keys.
Be sure to use some kind of encryption better than WEP (like Checkpoint VPN, IPSEC, etc.) otherwise, it's only a matter of time before your users' account info is stolen.
Also consider the kinds of antennas used on the AP. I actually bought the 3 dB loop antenna (size of a 10" plastic ruler) but I don't even need it within my own apartment (100' radius). I use both 2.4GHz phone and microwave with no major problems in my access. Mind you, I'm not using the link for heavy-use or Internet/media streaming. Here are some links to sites that helped me:
Good luck with it, please post a link to your HOWTO when you get it running!
Suncoast Linux - Sarasota, FL
Having used Karlnet quite a bit, I can say that they do offer products that work well for this application. I worked for a wireless ISP and we used Karlnet exclusivly.
Having already gone through what you are attempting to do, here are a few tips.
1. Use a DHCP server. Otherwise, you will be getting calls all the time about how to set up DNS, IP's etc. It's a nightmare.
2. Line of site through a window doesn't always work well. The glass tends to refract some of the signal. If you can align the antenna parallel to the window it will work. Also, it doesn't necessarly have to go through a window. 2.4 GHz will also go through wood and sheetrock to a certian degree.
3. It works best when you can mount the antenna outside and point it straight at the tower. People are less likely to mess with it then.
4. You may think that you have three clear channels but many companies are using this spectrum now. If you are in an urban area, you will probably find that someone is already using some or all of these channels. Check before you spend a lot of money on equipment.
5. Keep your signal levels high. When we started, we would hook up customers with an 8 dB signal to noise ratio. As time went on, the noise floor came up and we had to devise new methods to keep customers online. If you can't get at least a 15 dB S/N ratio, don't even bother hooking them up.
6. Keep your antenna cables short (usually LMR-400). This is usually your bigest sorce of signal loss.
The company I worked for eventually came up with a design where the radio card was mounted on the back of the antenna outside the building. Cat 5 cable was run to the antenna with power injected onto the unused pairs. This design works well because the signal is converted directly to 10-BT at the antenna with minimal signal loss. Since the entire unit is outside the building, there is much less interference from microwave ovens and cordless phones.
Good luck.
My father is a big Radio Shack Remote lighting finatic. (X10) Every Light is hooked up with a remote switch. All his laps have the plugin appliance system. Even his Cristmas lights are X10 enabled.
Well I needed to toss a cablle modem to me LAN which BTW was Wireless. And the only spot I had was down in the basement. Infact exactly 4 inches (yes I just mesured) away from the X10 modual controling the christmass lights.
My laptop is now on the third floor on the other side of the house. Almost the furthest point without going outside. Well on avarage I get about an 80% signal strength considering the amount of plaster and copper pipes between me and the basement. (For some reason tonight I have a 60% strength).
So, that being the case I'll go check the x-mass lights
. . .
Yup it worked... I'll place my bet that the interferance if any is not that big a deal!!!
> SELECT * FROM brain_cells WHERE synaptic_rate > 0
0 row returned
Phase matching the antennas is the biggest pain, simply due to the high frequency (and therefore small wavelength). Many AP's and some cards provide 2 antenna sockets for a system called diversity.
Diversity actually is best used to reduce multipath signals, as the radio listens to both signals, and "picks" the best signal to use from the 2 it received. Since both antennas are in different physical locations (from a few inches to about 2 feet is best), each antenna gets a different signal. Do not place these antennas in largely disparate locations, or seperated by some interfering object (like a steel support beam), as diversity works best when it can see the signal at BOTH antennas.
There are a huge variety of antennas out there, that produce different polarisation and radiation patterns. Some antennas have receiving amplifiers that produce huge (30+ dB) gain on receive, while only producing about 7dB gain on transmit. Semi-directional (from 60 degree to 180 degree coverage) antennas are great for outside walls. Some have clockwise or counter-clockwise "Circular" polarisation patterns instead of the average horizontal or vertical (circular polarisation tends to be better for point to point applications, and your antennas should match each other - CW will talk to CCW).
Yes.
It really is the party-pooper solution, as it's so low-tech, but when we priced it out, for most buildings Cat5 wiring is cheaper.
Depending on what kind of walls you're working with, (drywall vs. brick, etc) i've gotten quotes from roughly $30-100 per drop in an apt. Add to that $40/port for a good switch, and you're looking at $140 per room. And good cat5 contractors will give you some ungodly long warranty, on the order of tens of years.
Contrast this with 802.11. You have to pay for multiple APs (500~2k each depending on what you want/need), then you either have to a) pay for the 802.11 card for each pc and have the tenants pay a deposit (which was ~150ish when i priced them out, 100ish if they had a laptop) or b) force the tenants to buy their own. From doing some informal surveys and asking around, the latter wont work.
Then you have the line-of-sight problem (the computer has to be kinda near the window for them to pick anything up), the rf interference issue, and other funky stuff rf physics stuff. Not to mention you're on most likely a 1yr warrenty, and have to deal with helping people get their wireless card working, which can be a huge pain in the ass as likely they'll be using one of those pcmcia-pci slot converter things.
Furthermore security-wise, you honestly cannot beat having a plugged vs. not-plugged-in port, thus you can assure people are not stealing your service... A good switch will tell you what mac addresses are coming from what port, so with some good accounting on the side, you can tell exactly which apt has a hub and is sharing with their neighbors, etc. It also makes catching troublemakers (and there will be some, trust me) a lot lot easier, as you can pinpoint it to the room, not just to a mac address.
I more or less planned/ran a campus apartment project like this, and we did at first also seriously consider the 802.11 alternative, but quickly threw it away as we realized that a) it was going to certainly cost more long-run in labor than cat5 would,and b) it most likely wouldnt save us money upfront either.
#2. Use IPSec
Pros: Damn secure.
Cons: CPU intensive, limited software support outside of the OSS crowd.
OSS only? Win2k has support for it in its default configuration. I use this procedure to get win2k to connect to my frees/wan gateway using x.509 certificates. Piece of cake (it looks convoluted but it really easy once you do it once or twice) to set up, and lets anybody (linux, windows, mac, anyone with IPSec and x.509) on in a secure fashion.
CPU intensive? Not that I'm aware of. I'm pushing about half a T1 to another frees/wan server using a P100 on one side and a P200 on the other. Now I imagine this scales less than linearly for each client that connects, but I've been pleased with the throughput of this little computer.
Hello Cliff: While I have never posted on Slashdot I felt compelled to register and reply. PLEASE READ THIS CAREFULLY Allow me to explain that I am a network consultant and have learned the hard way on wireless--very hard and many sleepless nights. My first WLAN installation reminds me of where I think you may be right now, but I had done six months of research and had had endless hours of conversations with engineers from several manufacturers. Before we get to the problems I had, lets start with what you have missed overall: a site survey. NEVER even agree to take on a task like a WLAN unless you have done an extensive site survey. First, you will need blueprints if possible or will need to take fairly exact measurements of each apartment, know materials used in construction etc. You'll also need to have floor plans and more. That said, you should then know the maximum number of users and throw all the specs the manufacturer gave you out the window as regards range, distance and AP's required. And, I am assuming you will have over 20 users. In two different buildings? Don't go with consumer grade stuff like SMC for the AP's. SMC is the best of it but still lacks signal strength in many installs. Go with Cisco for AP's and routers, and ONLY Orinoco Gold cards for laptops and equivalent for desktops. You'll also need a portable spectrum analyzer and know how to intrepret the data it provides. Not sure if they can be rented but I paid $3,000 for mine and it was a deal. You'll need to set up the AP's and then go to every location and check SNR etc.--and record all the data. There's a mountain of paperwork on a project like this, just for the site survey alone. After that's done you will still need to go to each apartment with a mid-range laptop and again record signal strength etc. There will be dead spots, and God only knows where a tenant will put their PC. Now, you will have to roam about again with the spectrum analyzer AND a laptop to look for both multipath interference and to check for other 802.211b nets in the area. And did I mention if you are in a congested urban area or near a university or hospital you will also need to contact the admins at those institutions and hope they will cooperate and give you a map of their devices, antennae and locations? They generally will but may not even know where it all is if it's a large institution--and that can be yet another nightmare to solve. And, forget about promised scalability. Most AP's will really only handle 10 users or so, especially the consumer grade gear. At least unless things have changed drastically since November of 2001, my last nightmare install. You also have another problem: lack of a homogeneous hardware environment. On the Nigthmare Project 2001 (as I call it now) I had some PC's that never worked right if at all on the WLAN (30 users in one university residence, off-campus.) I spent an average of 8 hrs a day on the phone with high-level engineers from Cisco and SMC. Both companies were good but had to admit at times they had no idea why some problems happened. And I had their home and cell phone numbers. I know. Was dealing with a mix of Macs, Linux boxen and Windows PC's running anything from 98 to XP. And some were old Gateways, others new Dells. Gateways were the worst. Forget about the idea that your big worry will be with other 2.4 Ghz devices. Microwaves and phones have seldom been a problem for me on a project unless within 6 ft of the AP or wireless NIC. One stark exception is Panasonic phones, but this is a known issue fopr professionals. I am NOT anti-wireless but do think you should know that the obstacles you face are severe. I do this for a living and can say that I would not take on a project like this unless I had a very tight contract (you do have a lawyer, right.) CAT 5 and other options are cheaper and more reliable--and I haven't even touched on servers or security issues. Wireless is NOT cheaper, is more difficult to roll out and is a real headache--especially in historical buildings and those "impossible to wire" locations. I still do a lot of it but only for corporate installs where I have an open floor plan and decent line of sight. I also refuse to do an install now unless I know the company has skilled admins and will allow me indemnification. Do what you like but don't go into this believing all you have read from manufacturers or home users. Hope you don't have to learn as painfuly as I did. OK to email me at wavelanexperts@yahoo.com and I will be happy to chat on the phone or get you my real email. Good Luck!
I am in the process of developing a city-wide wireless network. Here are some of the thing I am doing in my lab to prepare for rollout.
1. PPPoE
Yes its anoying to users, and I'm not to fond of it myself, but it is a hell of alot better than any other auth method, IMHO, and it allows me to do some cool stuff with radius.
2. Amps are your friend
Most interference can be weeded out just by drownding it out. Pick a channel, and stay with it, when and if you have problems with interference amp it. Other devices that don't need as much as a spectrum in the 2.4 range, such as phones will just look for another clearer channel. At the ITECH i beamed in a signal into the convension center from a nearby hotel and ran an IP phone over it, I found out the morning of the show that lots of other people were using wireless inside the building, i just ran up to the roof of the hotel and stuck on an amp, and bamo 11Mbs, nailed.
3. Channel Selection
Most devices i've played with will either defaul to channel 1 or 6, put your signal on a high number like 9 to avoid killing your clients internal wireless network.
4. Saturation
The one concern I had is saturation, with only 11Mbs on 802.11b several power users could suck up alot of that. I would expect that more technical clients will realize that they are on an ethernet segment together and start setting up shared folders for their buddy 2 doors down so he can get all of his mp3s/porn. with enough users it could turn into a problem. I am remiding this by creating a backbone of 802.11a and then distriuting it with 802.11b
just my $.02