ANSWERS: 2
  • Internet addresses are in the form of numbers, IP (internet protocol) numbers like 27.15.1.510. Now, you don't really want to memorize the number for www.cnn.com (try it, http://64.236.24.28 ) so there are DNS servers that will resolve the cnn.com into what numbers it should be. Your ISP might use a different DNS server than mine, but in theory, they should be all synchronized. Of course, in reality, they are not always 100% so. For frequently used sites, or if you are having troubles with a particular site with your DNS server, you may want to hard code the site address along with its IP address on your pc. I also use my host file to block certain websites that I know I never want to go to. For more on host files, read: http://www.accs-net.com/hosts/what_is_hosts.html
  • When you connect to an document or service over the Internet, a set of protocols (or rules) is used in order to correctly communicate between your computer the and the server on which the document or service is located. When you want to view a webpage the HyperText Transfer Protocol (or HTTP for short) is used to request and then receive the desired webpage. HyperText Transfer Protocol is a set of rules for requesting and receiving data over the Internet. Mostly, this data is in the form of web pages, images, and music and movie files. First, a sojourn into the Internet has a whole works ... (Note that is not that detailed, and gloses over more of the technical stuff) When you type an address into your web browser, (such as http://www.yahoo.com/), the web browser opens a connection to the requested computer (www.yahoo.com) and sends an HTTP request for a document. Now how your browser knows the location of the computer www.yahoo.com is a bit complicated. Basically, your computer is connected through a physical connection (be it a phone line, cable modem, or wireless connection) to the Internet through an ISP (such as MSN, AOL, Earthlink, etc.) The ISP has a server (called a DNS or Domain Name Server) that is dedicated to the task of translating a computer name, such as "www.yahoo.com", to an actual IP address, such as 206.109.118.68. An IP (or Internet Protocol) address is a unique number giving the address of a computer, much like your mailing address gives the location of your house. Each set of numbers (before the period) is a direction to a certain computer network or computer itself. For example, www.yahoo.com has been assigned the number 68 in the 118 network, which is part of the 109 network, which is a part of the 206 network. When your computer tries to connect to another computer, pieces of hardware called "routers" are used to send your message to the correct computer. Using the example of www.yahoo.com, when you request the www.yahoo.com webpage and that is then translated to the IP address 206.109.118.68, your ISP sends that request to the router for the top-level network 206. Once at the 206 network's router, the message is sent to the 109 network within in. This continues until the message hits the computer 68 (or www.yahoo.com) OK, now that we know how the message gets from point A to point B, what the message contains and how the message is interpretted is also important. Computers that have webpages on them that can been seen on the Internet are called "web servers." The software that is used to recieve requests for webpages and then send the webpages back is also called a "web server." Internet Information Server and Apache are two commonly used web server programs. These programs listen on a specific port on the computer (usually 80) for requests for web pages. A normal request for a webpage is along the forms of: "GET /somedirectory/somepage.html HTTP/1.1 Host: www.yahoo.com" The command GET is one of the commands recognized in the HyperText Transfer Protocol. This command basically tells the web server software to send the requested page back. If the webpage is found successfully, it is sent back to your computer using the following message: "HTTP/1.1 OK 200 Date: (date of page) Server: (web server type) Content/type: text.html .....And the file." The "HTTP/1/1 OK 200" at the beginning of the message indicates that the document was found successfully (a code of 200). HTTP also has other codes which can be returned instead of an error occurred. For example, the code 404 is used if the requested document is not found. The file sent back to your web browser is then processed by the browser and then displayed as a webpage or image, or the music is played, or the file is saved to your computer depending on the type of file you requested. HTTP can be much more complicated than explained here. In HTTP are also the rules for sending and receiving header information which may be required by the web server or browser, including cookies. See also: http://computer.howstuffworks.com/web-server.htm http://computer.howstuffworks.com/router.htm http://computer.howstuffworks.com/internet-infrastructure.htm http://searchwebservices.techtarget.com/sDefinition/0,,sid26_gci214004,00.html

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