While surfing the Internet, do you find yourself going to get a cup of coffee, grab a magazine or retile your bathroom between page loads? If so, chances are you're using a dial-up connection, and a sneaking suspicion may be growing on you: Is your connection actually getting slower? It is and it isn't. As always, the connection speed of dial-up is limited by the bandwidth of phone lines; but at the same time, the average file size for Web content is getting larger and larger. More people are using broadband connections that can handle a bigger load, so Web sites feel more comfortable bulking up their pages. It takes a lot time to squeeze all of that data through a dial-up connection. Services like NetZero and EarthLink are now offering "high-speed dial-up." According to ads for these services, you can get connection speeds that are five times faster than traditional dial-up service.
When you think of dial-up Internet service, the first thing that probably comes to mind is the strange sort of "R2-D2 in a blender" type chirping that the modem makes as it connects. This song is called the handshake protocol, and it is the first thing that bogs down the speed of dial-up Internet. The handshake protocol, as the name implies, begins the conversation that allows data to be sent to and from your computer using the Internet. There are actually two separate handshakes that occur in this process. The first half is the modem initializing the Internet connection. We'll call that the modem handshake. The second part is the software handshake. That deals with authenticating the user's access to the ISP (Internet Service Provider). When your computer is chirping away, it is introducing itself to your ISP. High-speed dial-up providers can't do anything about the modem handshake, but they can speed up the software handshake.
On the next page learn about the standard software handshake and how it can be accelerated. ISP Server: Hello, Sparky. Your machine: I am John's computer. ISP Server: John who? Your machine: John Smith. ISP Server: I know 32,422 John Smiths. Your machine: He is one of your customers. ISP Server: Does he have an account number? ISP Server: What is that number? ISP Server: Ah, yes. This is a simplified explanation, of course, but you can get the idea of the back-and-forths that need to occur in the handshake protocol before information can be sent or received. High-speed dial-up providers have cut down on this back-and-forth by creating a system that allows the conversing machines to remember responses to questions. ISP Server: Ah, hello, Sparky. Aren't you John Smith's machine. This shorter handshake equals much faster connection times. The increase in speed varies by machine, but in some cases it can reduce the handshake by up to 50 percent. What might take 45 seconds with a "normal" dial-up service becomes maybe a 30-second process with a high-speed service.
When you search for a Web page on the Internet, your request is routed though your ISP to the Web. After making a series of stops along the way at machines that help find the page you're looking for, your machine is connected to the computer that serves the Web page you requested. Once this connection is established, data can flow freely from the Web server to your computer. Once the information leaves the Web server and hits your dial-up connection, that's where the bottleneck begins in the typical Internet transaction. But high-speed dial-up providers have come up with some pretty clever ways to open up that bottleneck. By loading special software into a server, they turn it into what they call an acceleration server. And by sandwiching the acceleration server into the chain between your dial-up connection and the Web, they can speed up the process considerably. When you search for a Web page using high-speed dial-up, your request is sent from the dial-up modem in your computer to the ISP's acceleration server.
Now the acceleration server is requesting and serving pages on your behalf. The acceleration server uses a broadband connection to quickly search the Internet for the server that hosts the page you're looking for. Once it finds that server, the two machines start talking and exchanging the information you need. Your ISP's acceleration server takes that information and sends it to your machine. Next, we'll go over how these acceleration servers drop the pedal on your dial-up. If you've read How File Compression Works, then you know that there are two types of file compression: lossy and lossless. Text and other files that need to remain perfectly intact during the compression process use lossless compression. Once they are uncompressed, the files return to their original state. When these files are uncompressed, they are not exactly as they were before compression: They have lost some of the original data in the process. For example, a picture that originally had 2 million colors may only have 16 thousand after lossy compression.
|