But TCP/IP assumes that there is a physical connecetion between one computer and another. This is not usually the case. There would have to be a network wire that went to every computer connected to the Internet, but that would make the Internet impossible to access.
学生网上选课系统 The physical connection that is requireed is established by way of modems,phonelines, and other modem cable connections (like cable modems or DSL). Modems on computers read and transmit data over established lines,which could be phonelines or data lines. The actual hard core connections are established among computers called routers.
A router is a computer that serves as a traffic controller for information.
To explain this better, let's look at how a standard computer might view a webpage.
1. The user's computer dials into an Internet Service Provider (ISP). The ISP might in turn be connected to another ISP, or a straight connection into the Internet backbone.
2. The user launches a web browser like Netscape or Internet Explorer and types in an internet location to go to.
3. Here's where the tricky part comes in. First, the computer sends data about it's data request to a router. A router is a very high speed powerful computer running special software. The collection of routers in the world make what is called a "backbone," on which all the data on the Internet is transferred. The backbone presently operates at a speed of several gigabytes per-second. Such a speed compared to a normal modem is like comparing the heat of the sun to the heat of an ice-cube.
Routers handle data that is going back and forth. A router puts small chunks of data into packages called packets, which function similarly to envelopes. So, when the request for the webpage goes through, it uses TCP/IP protocols to tell the router what to do with the data, where it's going, and overall where the user wants to go.
4. The router sends these packets to other routers, eventually leading to the target computer. It's like whisper down the lane (only the information remains intact).
5. When the information reaches the target web server, the webserver then begins to send the web page back. A webserver is the computer where the webpage is stored that is running a program that handles requests for the webpage and sends the webpage to whoever wants to see it.
6. The webpage is put in packets, sent through routers, and arrive at the users computer where the user can view the webpage once it is assembled.
The packets which contain the data also contain special information that lets routers and other computers know how to reassemble the data in the right order.
With millions of web pages, and millions of users, using the Internet is not always easy for a beginning user, especially for someone who is not entirely comfortale with using computers. Below you can find tips tricks and help on how to use main services of the Internet. 本文来自辣.文,论-文·网原文请找腾讯324-9114
Before you access webpages, you must have a web browser to actually be able to view the webpages. Most Internet Access Providers provide you with a web browser in the software they usually give to customers; you. The fact that you are viewing this page means that you have a web browser. The top two use browsers are Netscape Communicator and Microsoft Internet Explorer. Netscape can be found at and MSIE can be found The fact that you're reading this right now means that you have a web browser.
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