Designing a Municipal Wireless Service? 42
EvilTwinSkippy asks: "I am on a team generating a proposal for the Wireless Philadelphia Initiative. In short I have to figure out how to cover 135 square miles of city with Wifi. I'm reading through the requirements. (Not linking to them, no fair slashdotting the customer, or my employer.) I have already figured out that supporting Wireless B and G simultaneously has to go. As does supporting cars traveling at 60mph. And getting 1MB sustained across the network is a pipedream. In the end, I'm looking down the barrel of designing a network this is projected to have 160,000 users in 5 years, over at least 3000 nodes. I know that Rooftop mesh networks are going to be a large part of the design, as will Linux boxes acting as routers and access points. What massive network issues has 4 years of electrical engineering, and 10 years of hacking routers and servers not prepared me for?"
Don't lead the pack (Score:2, Funny)
Re:Don't lead the pack (Score:3, Informative)
3000 unattended servers? (Score:3, Informative)
Consider using dumb access points with battery backup, the kind that can be replaced easily and without much configuration. Centralize your authentication mechanism on the back end.
Re:3000 unattended servers? (Score:2)
Re:3000 unattended servers? (Score:1)
Why is admin on 3000 unattended servers hard? (Score:1)
I would be concerned with the scalability of the solution. I would be looking for an upgradable WiFi AP and I'd make plans for the next generation of WiFi.
Re:3000 unattended servers? (Score:2)
In hindsight, that seems quite a flawed setup for this application and each AP being a full server/router seems neccessary.
*slaps forehead*
However, as someone else mentioned, I don't see why administering them should be so difficult. If setup properly the b
Re:3000 unattended servers? (Score:4, Insightful)
What I think that the submitter is trying to do is to find strategies to minimize 'network churn'. I have a couple of ideas on what is needed, but my lunch hour is almost up and I need to get back (my company block my attempt to post to slashdot a couple of weeks ago and I have been avoiding it at work ever since.)
Re:3000 unattended servers? (Score:2, Informative)
And in the meantime
Re:3000 unattended servers? (Score:2)
IPv6 (Score:2)
IPv6 is designed to solve this problem. I don't know how well it works, but if it works as well in practice as theory, you tell everyone on IPv4 that they need IPv6 to get good roaming. Maybe this would force Microsoft write a good IPv6 implementation for Windows. (yeah right)
Re:3000 unattended servers? (Score:2)
the larger netmask lets one do things like have 10.10.10.10 use 10.10.20.1 as a gateway because 10.10.x.x are treated as local
The other idea I had
Re:3000 unattended servers? (Score:2)
FWIW, most of your "dumb access points" are actually running an embedded form of Linux. D-Link and LinkSys/Cisco equipment comes to mind.
3000 untended servers, Take Two (Score:4, Funny)
Philly's Wireless (Score:1)
Re:Philly's Wireless (Score:2)
Re:Philly's Wireless (Score:2)
Wireless Philadelphia is going to be putting out it's own bonds and whatnot to fund the project. I don't believe it's getting a nickel of state money. (At least not according to the financials I've seen.)
About the only thing they have going for them over anyone else setting this up is the City's blessing to use light poles. My plan actually calls for ren
Re:You're joking right? (Score:2)
Answer: Impossible (Score:2)
Re:Answer: Impossible (Score:3, Informative)
The primary allocation is to amateur radio; other users are there on a Part 15 basis, which explains your experience with your neighbor's phone. You're required to accept any interference from other devices on the band. Since I hold a licence for that band, I'm a primary user, and if interfered with by a Part 15 device can require that they fix the problem or shut down.
If I can find them.
Re:Answer: Impossible (Score:3, Interesting)
Re:Answer: Impossible (Score:2)
Why not B and G? and speed (Score:2, Informative)
Seems G would be the way to go. Higher cost, but better longevity and compatibility and potential bandwidth.
As for concerns about speed: Here's the thing that gets me about WiFi speed potential (or Ethernet for that matter) when it comes to an open network: What difference does the speed of the line to the node make as long as it's at least as fast as the pipe you'll be using on the back to connect out to the w
Re:Why not B and G? and speed (Score:2)
Re:Why not B and G? and speed (Score:2)
Boosting output may increase the range of the access point, but my problem is population density. We have 30,000 people per square mile. As it is, each access point will have to cover 80 users, even spaced 300 feet apart. Not saturating the access points is a bigger problem than range.
I've done this before. (Score:4, Interesting)
Find the highest point in a particular region of town, and get the rights to put a weatherproof box and an antenna up on a tower near there. (cell phone companies are very good at finding the best points to place a tower or antenna. you should follow their lead.) in the weatherproof box put a soekris board running linux and two wireless cards and antennas on them. One card will be a backbone 802.11g link with a directional, high gain antenna, the other a customer link with a 802.11b omni antenna.
do that for every region that needs coverage.
Find points where multiple region APs can see, and do the same as above, but get a horizontally polarized omnidirectional antenna. they're expensive, but worth it. Connect all the regional APs to this. Run a T1 into whatever computer controls this antenna.
do that for every group of regions.
viola! citywide wirless. a true star topology.
there are some details i'm leaving out, but this should give you a good idea.
run zebra on the linux APs to handle routing.
use backbone redundancy where possible, the APs will fail occaisionally.
Re:I've done this before. (Score:2)
With the right antennas, we'll never have to go more than one hop. My projections show that we charge $7.95/month and turn a profit. (Assuming we get 160,000 users by year 5.)
The most expensive part of the project is actually the staff to maintain it.
Go for WiMAX (Score:2)
For more information, mail me. I have an account on Yahoo named mtetrode.
What you need ot be prepared for (Score:1, Insightful)
In Philadelphia: union thuggery, municipal corruption, and pay to play.
Is this for real? (Score:4, Insightful)
3000 full-blown linux servers? Jiminy Christmas. Probably COTS PC hardware, right? Please tell me there are competing bids from experienced networking outfits?
Mod Parent +99999, Hilarious (Score:1)
Competitive bidding in Philadelphia? You crack me up!
Re:Is this for real? (Score:2)
You expect the vendors to give better advice?
From another angle: Even smart, experienced, people benifit from asking basic and potentially stupid questions. If they listen.
I call that "The Columbo Method" after the TV detective of the same name.
Good point! (Score:2)
It is said that there are actually few dishonest auto mechanics, but a lot of incompetent ones. Unfortunately the same it true in IT.
Warning Will Robinson!!! (Score:3, Insightful)
Know your scope, technically you are setting up WiFi but you need to forget about the technology for a moment and have AT LEAST a prioritized list of what this network is to be used for. Without that guiding light it will do what it does, but it may not do what anybody (or perhaps a particular high ranking somebody) will want it to do. You won't have anything to guide your decisions or your priorities.
Second, LATENCY!
I haven't played with WiFi meshes so this may not come in to play but from past experience with Wireless solutions ala ISP you have to remember that cabling and bandwidth is VERY IMPORTANT. Donot be tempted to use wireless repeaters with abandon. You need to be able to have a greater amount of backbone, node to node bandwidth than the nodes themselves will provide. If the wireless nodes get overloaded and TCP retransmissions (or retransmissions by the WiFi repeaters themselves) will climb and there will be a point no packets will move. The latency of WiFi will cause this packet storm (if you will) way quicker than wired solutions. Without a good amount of bandwidth behind the nodes, or even a backup landline for administration bringing it back could be quite a pain.
The ISP I worked for tried to deploy point to point wireless bypassing the telco. Rather than run cable to the tower, they used point to point to the tower and then point to point to their customer. It didn't take long (since all of the point to point links were rated the same) for the whole solution to get snarled up bottlenecked on the point to point between the ISP and the tower. With the latency of wireless it would be unusable REALLY quick. (If only we had SQUID and bandwidth limiters back then... SIGH...)
Lastly, you have the greatest opportunity to win through control. Your watchwords should be metrics and design. As you roll out your nodes you best be pulling metrics so you know how your design will handle load and how it will fail. This will be knowledge that is good as gold, and will allow you to re-design and re-deploy. Your first attempt will be a guess but if you capture the metrics and track as most information as you can, whether that be the temperature of the wireless nodes (do they overheat, are they sheltered, is there a pattern to failure) or the packet retransmissions; all of that information will be vital to learn how to tune it up, engineer it and deploy it.
Have fun... I'm envious...
There are commercial solutions (Score:2, Informative)
Cisco CAT 6500 and the mobility extensions (Score:1)
Assume 20 users per AP. 200,000 users would mean that you are looking at 10,000 access points with NO redundancy. OK, you want each client to have two access points to connect to so you are going to need 20,000 access points. Now you need switches to connect to. Lets assume you can connect 400 access points to one Cisco 6500 switch. You would need 50 switches at $100,000 each. 5 million in switches and 20 million in access points. Now you n