No So Fast

Plugged In

You can conduct your own speed trials on Internet claims of lightning-quick broadband connections

August 09, 2007|By Mike Himowitz | Mike Himowitz,Sun Columnist

You can't watch TV, listen to the radio or read a newspaper today without being bombarded by ads for broadband Internet service. Cable and telephone companies are in a ferocious battle for market share, and they're all bragging about how fast they are. Unfortunately, they're usually exaggerating.

In fact, the gap between advertised and actual performance may be so great that it doesn't matter whether you choose cable, DSL or fiber-optic service. If your online life is mainly limited to Web browsing and e-mail, any broadband provider will deliver acceptable speed. But it's likely to be well below the advertised speed for the slowest category of broadband - basic DSL.

On the other hand, raw speed may be important if you frequently download large files, such as full-length movies, or if you want to watch streaming TV shows online. Even then, the performance of your Internet service provider (ISP) is likely to be well below its advertised speed.

Don't believe me? Check it out yourself. The Web is full of free broadband speed testing programs. The problem is that different tests are likely to produce widely differing results - because they may not test speed in quite the same way.

We'll look at two examples today and help you decide which one is more useful. Or you can try both; there's no charge.

Before you start testing, let's talk about how Internet speed is measured, advertised, and abbreviated.

Typically you'll see ads that say something like this: "Blazing 8 Mbps downloads," or "Rip-roaring 768Kbps downloads." These generally refer to how many bits per second the service can transmit to your computer.

A bit is a digital one or a zero - the basic unit of data - and it's abbreviated with a small "b."

The "K" or "M" at the beginning stands for "kilo," which is Greek meaning 1,000, or "mega," which means 1 million. So a service with an advertised speed of 768 Kbps can move 768,000 bits of data per second from its server to your computer.

An ISP that offers 4 Mbps downloads is claiming 4 million bits per second. Typically, upload speeds from your computer to another one are slower, but that's another story.

It takes roughly 10 bits to transmit a single character of data (known as a byte). The text in this column requires about 6,000 bytes, or 60,000 bits. So basic DSL (digital subscriber line) service operating at the advertised speed of 768 Kbps should be able to transmit this golden prose in less than 1/10th of a second.

To put this in perspective, the first modem I bought in 1983 transmitted data at just 300 bits per second, so sending a column to The Sun took almost 3 1/2 minutes, assuming the connection held up that long. That's why today's communication speeds seem like magic to old-timers like me.

Why aren't you likely to get the speed your ISP advertises? First, that speed is the maximum the network is set up to deliver - and then only on a point-to-point delivery of a single file from a server on the same network. If you venture no further than your ISP's Web site or servers, you might get close to the advertised performance.

But the real-world Internet is an unthinkably huge and complex highway system, with millions of byways, many of them slower than your ISP's network. The data that flows through them is pumped by millions of servers handling requests from millions of users every second. The data you send or receive may take dozens of hops from network to network, from server to server on the way to its destination. And it will travel only as fast as the slowest link in the system.

The lesson: Even if you pay for 8 Mbps of download capacity, it won't help if you're waiting for a server that can only pump out 200 Kbps.

Now consider Web browsing, which is far more complex than receiving e-mail or downloading a song from iTunes. A Web page is a simple text file that tells your Web browser how to display the text it contains, as well as the location of the photos, graphics, and other multimedia components on the page.

Your computer has to retrieve each of those files over that same labyrinth. The ads on commercial pages often come from faraway, third-party servers. By the time your computer completes dozens of these transactions for each page, your ISP's advertised download speed looks like wishful thinking indeed.

True, your Web browser stores some downloaded graphics on your hard drive so it won't have to reach out to a remote server if they're needed again. But there's still plenty of overhead built into every complex Web page.

How much overhead? The best speed test I've seen is a free download from PC Magazine called SurfSpeed. It duplicates requests your Web browser would generate from 10 popular Web sites, including Google, Yahoo, MapQuest, AOL, MySpace, Microsoft and Apple.

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