Internet Architecture- Lecture 4

Internet Architecture
Lecture 4: How Internet Addresses and Domains Work

Introduction
The heart of how the Internet works is the Domain Name System (DNS), the way in which computers can contact each other and do things such as exchange email or display web pages. When someone on the Internet wants to contact a location for example, to visit a website he types in an address, such as www.metahouse.com. (A specific location on the Internet is also referred to as a uniform resource locator, or URL). The DNS translates the plain English address, www.metahouse.com, into a series of numbers called an IP (for Internet Protocol) address. An IP address, such as 123.23.43.121, marks the location of a computer on the Internet similar to the way a house number and street mark the location of where you live.
In this example, metahouse.com is called a domain. To work most efficiently, the Internet has been organized into a number of major domains. Major domains refer to the letters at the end of a plain English address, such as .com.
-A number of common domains are:
.com (commercial).
.edu (education).
.gov (government).
.mil (military).
.net (Internet service providers and networks companies and groups concerned with the organization of the Internet).
.org (organization).
Domains are organized in a hierarchical manner, so that beneath major domains are many minor domains. As an example of how the DNS and domains work, look at NASA s SPACElink Internet address: spacelink.nasa.gov. The top domain is .gov, which stands for government. The domain just below that is .nasa, which is the NASA domain. Then, spacelink identifies the NASA computer that runs the SPACElink program. SPACElink s numeric IP address has changed through the years, but its Internet address has stayed the same.