How Domains and Internet Addresses Work
The Internet Protocol delivers mail to a specific IP address at the recipients e-mail server. The address is written as four numbers separated by periods (called dots), for example, 62.143.245.76. Internet addresses, however, are made up of words because it would be difficult to remember series of numbers for every Web site. Computers called domain name server translate the alphabetical address into the numerical one, so that e-mail can be sent to where it should arrive.
An e-mail address is made up of two main parts separated by an @ sign. The first part of the address is the username, which identifies the person who owns the account. The second part of the address, which is on the other side of the @ sign, contains the hostname (which is not necessarily used). The hostname can name a certain server on a network. The hostname (if there is one) is followed by the Internet address. For example if your e-mail address is [email protected], johnnyq is the username, customer is the hostname, and yahoo.ca is the Internet address.
When an e-mail is sent, it first goes to a name server. The name server looks up the alphabetical address and substitutes the numerical IP address, so that the e-mail can be delivered.
The Domain Name System (DNS) divides the Internet into groups called domains. The domain name is the last part of the address. It tells you what domain, and what type of organization the person’s address belongs to. To the left of the largest domain is specific information that tells routers what server to send the e-mail to (for example, hotmail.com). To the left of that is the hostname which tells routers which computer in the domain the e-mail should be delivered to. The host computer that receives the e-mail looks at the username and puts the e-mail in the proper inbox.
How Uniform Resource Locators (URLs) are Made
Take the URL: http://www.mysite.com/personal/pictures.html as an example.
The first part of the URL – http:// – states which transfer protocol will be used to find the requested document. The most common protocol requested is the HTTP protocol.
The second part of the URL (www.mysite.com) states which host computer the document can be found on. This section is called the domain. The suffix of the domain name tells you what type of organization the domain is. The suffix can also tell you what country the computer is in. Some common endings include:
· .com: a commercial business
· .org: a not-for-profit organization
· .edu: a college or university
· .gov: a government office
· .mil: a military facility
· .ca: the computer is in Canada
· .uk: the computer is in the United Kingdom
The third part of the URL (/personal) is the directory on the host computer that has the Web site being requested. This part is used because the host computer can have many Web sites on it.
The last part of the URL (/picture.html) is the filename of the requested Web page.