Getting more Nines on Wi-Fi Availability

Reliable, Available and Scalable - RAS - is almost like a mantra we mumble to ourselves in Enterprise computing. You've all heard the story of the renovated University building at Stanford or Berkeley where some Sun box running as a department mail server was walled up behind sheet rock accidentally, and it remained that way for 5 years and kept running until some decided to upgrade the system and couldn't find it anywhere, but they could still ping it.

But I had a little related "thank you" email come across from a neighbour up in British Columbia where my vacation home is. It's half way up Hwy 99 toward Squamish/Whistler next to a fancy golf course and next to the water. Well, about 1/3rd of the neighbours are residents from the States. Last Christmas, Telus (a.k.a. BCTel) finally dropped some fibre down from Hwy 99 (which they laid 18 months ago!) into our complex. We all got broadband at a clean 1.5Mbps down/640kbps up. I planned a Christmas/New Year's trip up at the time just to get the network up and install some wireless. That way, I could kick back out on the water fishing and still be logged into work. It always seems like the fish bite better when I'm not paying attention to the rod, so surfing the net just invites more hits.

I keep the Wi-Fi network open to the neighbours and put up two access points on opposite sides of my house. The units also sport high gain attennaes that push the signal clearly out to Hwy 99 which is 1/2 km away. So folks on the Golf Course should be able to get clear signal as well. Also, I set one AP to channel 4 and the other to channel 10 to support more users with fewer collisions.

My US neighbours just love the WiFi. Most head up there to ski and golf several times a year. And they've gotten used to the very reliable and available wireless and it saves them the monthly fees and hassles paying for their own connection, and insuring that it's up and running and secure when they arrive up in B.C. every couple of months. I simply donate the bandwidth. It's a small cost compared to what I pay for down here in the Bay Area for my DSL and the signal is so much cleaner up there too - as if I was just next door to the C.O. Plus with the exchange rate for $CDN, the price is even better.

So one neighbour wrote me a pleasant thank you email that expressed some amazement. On a recent trip, they had a power outage in the complex for about 30 minutes (a frequent event that happens once a month or so). But amazingly, they had laptops up and running, and the network never waivered. He said that he almost came over and knocked on my door because he swore I must be up there in the house working and maintaining that Wi-Fi connection because it's ALWAYS up. Even during the power outage. Whatever I was doing, Kudos.

I smiled when I read that. I guess what he didn't see when I came up during Christmas were the dual 50lb UPS backup power units I had. Each was connected to the AP plus the DSL router and switch. I chose the components carefully. Not so much for performance as I did for reliability and power consumption. I also have learned that less moving parts means more reliability. So I didn't put a running server up as the firewall/router, but used a solid-state off-the-shelf one that only has a limited number of ports. This way, I have battery backed power always available for the network and it's enough to power the entire network for 7 or 8 hours. Which exceeds 95% of outages.

So why back up the network? Because the Network IS the Computer. That's another mantra our company has preached for like that last two decades. But more importantly, I've learned from my mistakes. It was pretty embarrassing a few years ago when I was helping a friend setup his server for a Linux startup. The whole rig was in his garage. We bought a boat load of big UPS's to back up the servers. But we completely forgot about the network and on our first power outage, the servers were fine, but the network was down. That was pretty stupid and I've gone on to refine how I get more reliability into my networks. Some tips I remind myself with:

  1. With UPS, size matters. Bigger means more power longer.
  2. Cheapest and Simply are often better. Instead of forking over big bucks on name brand UPS power for your home, the biggest and simplest way to get power is to daisy chain a couple of deep cycle 12VA batteries to one of those plug in rechargeable Outdoors/Jumpstart camping power packs with CAR/12VDC cigarette lighter socket.
  3. To support multiple devices, buy a car cigarette lighter socket power-strip. It's got like 4 or 5 sockets. Then for each devices, I get a DC-to-DC converter that has a Zener diode to down-step the voltage. So this is why I select network devices for their DC power requirements. As long as they are under 12 VDC, I can buy/make an adapter cable that will power the device.
  4. Forget those 12VDC-to-110VAC inverters. Too much power loss in the conversion to AC and conversion back into 9VDC/1.5 amps. You get LONGER backup times going DC-to-DC only.
  5. Don't put a PC running Linux as a NAT firewall/router/DHCP server, even if it's a VIA Eden MoBo unit. It's less reliable and eats LOTS more power and requires a tonne of maintenance, plus you still need to power a switch. Most common WiFi AP routers have all these functions plus remote manageability.
  6. Wi-Fi APs with router and switch are much more integrated, lower power, and more reliable than separate switch, router and dumb AP.

In tbe backcountry of San Diego county we add solar panels to the mix. A deep cycle marine batter, solar panel, and charge controller runs some of our mountaintop network backbone quite reliably. We don't have AC power in many places, so we have to improvise. Many of the radios, access points, and bridges only consume 10-15 W, so they can go for many days on just the battery alone. Of course we have the benefit of 300+ sunny days per year, which probably isn't the case in BC!

Posted by Richard Elling on August 23, 2004 at 02:58 AM PDT #

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