1. Introduction to How High-speed Dial-up Works
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.

2. High-speed Dial-up: Acceleration Servers
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.

3. High-speed Dial-up: File Compression
The key element of high-speed dial-up Internet is file compression. 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.
Photos and graphics can be transmitted using lossy compression. 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. The loss in quality may not be important to the user when
weighed against the increase in speed gained through the compression process. Companies like
NetZero let the user control how much compression is used on photos and certain sites.
File compression is an evolving technology, and it doesn't work on every file type yet. The chart
below will help you understand what will and will not be accelerated by high-speed dial-up.

4. High-speed Dial-up: Filtering and Caching
The first time your browser loads a Web page, it has to load the entire thing, along with all of the
images it displays. If the browser saves the images and text, then the second time it loads the same
page it can check for duplicates. If an image has not changed, there is no need to download it again.
This process of saving a file in the hopes of reusing it in the future is called caching. For a complete
explanation of the caching process, see How Caching Works.
High-speed dial-up uses a similar system for commonly requested Web pages. Instead of constantly
requesting the same page, the acceleration server takes note of which Web pages are being
commonly asked for by all subscribers. So instead of asking the HowStuffWorks server thousands of
times a day if it can see the homepage of HowStuffWorks.com, it just asks once. Then it stores the
page in its memory, and every time another subscriber asks to see HowStuffWorks, it simply transmits
the page out of its memory to the user. This is called server-side caching, and it saves time by
eliminating redundant requests.
There is a second side to caching -- client-side caching. Internet browsers like Explorer or Netscape
are made to cache frequently viewed pages to cut down on load times.

5. High-speed Dial-up: The Bottom Line
Now that you understand how it works, let's take a moment to look at how well it works. We decided
to try out one of the more popular high-speed dial-up providers, NetZero, to see how much the
service sped up a dial-up connection.
After signing up for the service and choosing the "out of the box" settings, HowStuffWorks tooled
around the Web with both normal and high-speed dial-up connections to test the difference in
speed.
After log-in, we surfed repeatedly to some of the most popular sites on the Web. The results varied
by site, but as an example, HowStuffWorks came up three times faster with high-speed dial-up. For
the complete results, see the chart below.

6. Lots More Information
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. This makes for a much shorter conversation:
Your machine: Hello, my name is Sparky.
ISP Server: Ah, hello, Sparky. Aren't you John Smith's machine.
Your machine: Yes, his account number is 5546743897.
ISP Server: Go ahead, 5546743897. You have access.
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.