Wireless

Sizing Wireless Pipes

Is investing in excess capacity the smart play, or is it more sensible to buy what you need now and grow later?

[January 19, 2000]

On the ISP-Wireless list in December 1999, PJ posted a question about moving into wireless despite equipment limitations:

"We don't have a satellite feed for our ISP or a T1 for outbound. Currently, our largest pipe is less than 2Mbps. We plan to sell 128K, 256K, and 384K connections. We're considering an 11 Mbps Aironet BR500E access point as a radio bridge, but Teletronics makes a 2 Mbps access point. I've been told the 2Mbps would work fine; is that correct? What would be the reason for getting the 11Mbps unit?"

 

One respondent felt that PJ's choice should be based on the company's expected potential growth:

[KA wrote] "Pick whichever system is going to give you the most bang for the buck. If you expect a large deployment, go for a 11Mbps system. If you expect small growth, go with the cheaper 2Mbps system. It wouldn't make sense to spend a lot of money on hardware that will not be utilized to its full potential."

Another advocated the larger system:

[MKS opined] "You need the 11meg units so that you can actually get T1 speeds to your customer! Radios will chew up 50 percent or more of the bandwidth with internal chatter."

[KA took issue] "If anyone makes a wireless system with 50 percent or more chatter, look for another product. If a system is set up correctly, you experience 1.8Mbps on a 2Mbps system which really means that about 200Kbps are used for checksums. Fifty percent chatter isn't a possibility, unless you have really crummy signals levels and massively misaligned dishes."

The logical suggestion was made of starting out small and upgrading as needed:

[JT wrote] "Do the Teletronics now and move up to an Aironet later. We started out with Linux boxes with cards set as Ad Hoc in our repeater sites. But since we found the Teletronics access points, we have switched to them for a number of tasks ( bandwidth shaping, NAT [network address translation], and Squid, for example). They are a great inexpensive solution. We use Aironet for our backbone."

Yet another respondent suggested using a combination of the two systems:

[JD wrote] "We use the 11Mbps Aironet for our backbone (ISP-to-REPEATER, REPEATER-to-REPEATER), and at the repeaters we use the 2Mbps Teletronics for multipoint connection to clients. Even with the wireless coming back to your NOC you should route all that traffic to a Squid cache and let that talk to your real internet circuit. That way the backbone on wireless is always a rocket and the clients are impressed."

—End