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  1. 1. How High-speed Dial-up Works 1.Introduction to How High-speed Dial-up Works Surfing the Internet, do you find yourself going to get a cup of tea, a comic or clean yourbathroom between page loads? There are chances are youre using a dial-up connection, and asneaking suspicion may be growing on you; eventually , is your connection actually gettingslower? Sometimes, 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. So Websites feel more comfortable bulking up their pages. It takes a lot time to squeeze all of that datathrough a dial-up connection. New technology offers a solution to the slow-down that doesntnecessitate broadband. Services like NetZero and EarthLink are now offering "high-speeddial-up.“ According to advertisement for these services, you can get connection speeds that arefive times faster than traditional dial-up service. High-speed dial-up providers cant do anythingabout the modem handshake, but they can speed up the software handshake.
  2. 2. 2. High-speed Dial-up: Acceleration ServersThe standard software handshake is usually a simplified explanation, of course, but youcan get the idea of the back-and-forth that need to occur in the handshake protocol beforeinformation can be sent or received. High-speed dial-up providers have cut down onthis back-and-forth by creating a system that allows the conversing machines to rememberresponses to questions. This makes for a much shorter conversation. This shorterhandshake 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 45seconds with a "normal" dial-up service becomes maybe a 30-second process with ahigh-speed service.When you search for a Web page on the Internet, your request is routed though your ISPto the Web. After making a series of stops along the way at machines that help find thepage youre looking for, your machine is connected to the computer that serves the Webpage you requested. When you search for a Web page using high-speed dial-up, yourrequest is sent from the dial-up modem in your computer to the ISPs acceleration server.Now the acceleration server is requesting and serving pages on your behalf. Theacceleration server uses a broadband connection to quickly search the Internet for theserver that hosts the page youre looking for. Once it finds that server, the two machinesstart talking and exchanging the information you need. Your ISPs acceleration server takesthat information and sends it to your machine
  3. 3. 3. High-speed Dial-up: File CompressionYou know that there are two types of file compression that is the Key element ofhigh-speed dial –up Internet. Text and other files that need to remain perfectly intactduring the compression process use lossless compression. Once they are uncompressed,the files return to their original state. When these files are uncompressed, they are notexactly as they were before compression. They have lost some of the original data in theprocess. The loss in quality may not be important to the user when weighed against theincrease in speed gained through the compression process.Eventually, the on-the-fly file compression utilized in high-speed dial-up cant be added tothe file types specified above because of the nature of the data. For instance, data on secureWeb sites is encrypted. When it is transmitted, the code looks like a bunch of gibberish sothat no one can read it. I will describe three examples is text, image and other files.At text files ・・・ Typically, text will compress at least 50 percent using on-the-fly techniques.At image files ・・・ Typically, the image file size shrinks anywhere from 50 percent to 90percent in the process.At many other files ・・・ It is not possible to compress the file any further in a quick way.In the case of secure Web pages, we already discussed why they cannot be compressed.The acceleration server will not touch these files -- it just passes them through something.
  4. 4. 4.High-speed Dial-up: Filtering and Caching If you type a URL into the address bar of your browser, you are sending a request for aspecific page. When the information is sent back to your machine, the hidden codeexecutes a program that launches the advertisement. In order for the pop-up to pop, thathidden code must display parameters that tells your machine what size the ad is, where onthe screen it should appear, and other details about the ad. These ads take up valuablebandwidth, slowing down the transmission of data to your machine. When you combat this drag, high-speed dial-up providers have bundled a pop-up blockerinto the software they send to subscribers. This pop-up blocker is programmed torecognize those lines of code that spell out the ad parameters. When it sees those tell-talelines of code, it rejects the ads request to be displayed. What this amounts to is lessinformation being sent across the phone line to your machine. The less data that is sent,the faster the load time. High-speed dial-up uses a similar system for commonly requested Web pages. Instead ofconstantly requesting the same page, the acceleration server takes note of which Webpages are being commonly asked for by all subscribers. So instead of asking theHowStuffWorks server thousands of times a day, it just asks once. Then it stores the pagein its memory, and every time another subscriber asks to see that, it simply transmits thepage out of its memory to the user. This is called server-side caching, and it saves time byeliminating redundant requests.
  5. 5. 5.High-speed Dial-up: The Bottom Line We decided to try out one of the more popular high-speed dial-up providers to see howmuch the service sped up a dial-up connection. After signing up for the service andchoosing the "out of the box" settings, HowStuffWorks tooled around the Web with bothnormal and high-speed dial-up connections to test the difference in speed. After log-in, wesurfed 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. It would seem that a clever combination of fairly straightforward technologies has helpedto overcome some of the speed bumps of dial-up Internet. These advances serve to prolongthe life of dial-up Internet and provide an alternative for those who are tired of standarddial-up but not quite ready for the leap to broadband. If these advances continue, dial-upmay be here to stay for quite a while. For more information on high-speed dial-up andrelated topics, check out the links on the next page.
  6. 6. 6. Lots More InformationHow WiFi Works ・・・ WiFi has a lot of advantages. Wireless networks are easy to set up andinexpensive. Theyre also unobtrusive -- unless youre on the lookout for a place to use yourlaptop, you may not even notice when youre in a hotspot. In this article, well look at thetechnology that allows information to travel over the air. Well also review what it takes tocreate a wireless network in your home.First, lets go over a few WiFi basics.How DSL Works ・・・ When you connect to the Internet, you might connect through a regularmodem, through a local-area network connection in your office, through a cable modem orthrough a digital subscriber line (DSL) connection. DSL is a very high-speed connection thatuses the same wires as a regular telephone line.How Modems Work ・・・ In this edition of HowStuffWorks, well show you how a modembrings you Web pages. Well start with the original 300-baud modems and progress all theway through to the ADSL configurations!(Note: If you are unfamiliar with bits, bytes and the ASCII character codes, reading How Bitsand Bytes Work will help make this article much clearer.)