This chapter is from the book
This chapter is from the book
This chapter is from the book
THE DOMAIN NAME SYSTEM
The URL naming scheme developed by Tim Berners-Lee is very powerful. Recall that a URL has three parts, one of which is the name of the server. This name is called a domain name. An example of a domain name is gsbkip.uchicago.edu. The domain name is ordered right to left. The top level domain in this name is .edu, the domain for educational institutions. The current top level domains are given in Table 4–2. Besides the domains listed in Table 4–2 there are extensions that denote a foreign country. For example, .jp is the extension for Japan and .defor Germany. Reading right to left, the next part of the domain name in our example is uchicago(note that dots separate levels of the domain name). This is a second level domain, in this case, the University of Chicago. Finally, gsbkiprepresents a host machine within the University of Chicago.
Table 4--2 Top Level Domains
|
Domain Type |
Description |
|
.com |
commercial users |
|
.net |
network providers |
|
.edu |
educational institutions |
|
.org |
nonprofit organization |
|
.gov |
United States government |
|
.mil |
United States military |
|
.aero |
(new) |
|
.biz |
commercial use (new) |
|
.coop |
(new) |
|
.info |
all uses (new) |
|
.museum |
(new) |
|
.name |
for individuals (new) |
|
.pro |
(new) |
When you click on a link with an underlying URL, you are taken to the computer named in the URL. Having a name for a server is important for Internet business. For example, if you wanted to go to the IBM Web site, you would naturally guess the name to be http://www.ibm.com. Certainly names like amazon.comhave become valuable trademarks. Indeed, there have been numerous law suits over domain names. Many businesses invest a great deal of time and money in selecting an appropriate domain name. It is important to have a name that is easy to remember. A good domain name can also be a marketing tool.
In an earlier section we saw that TCP/IP software uses IP addresses, not names, for addressing packets. This means that somehow the domain names must get converted or resolved into IP addresses. This is done through an Internet service called the domain name system (DNS). This system makes use of special servers called domain name servers. The process is illustrated in Figure 4–7.
For example, assume an employee sitting at a desktop PC makes a request for a file to the machine with domain name gsbkip.uchicago.edu. The domain name gets resolved from right to left. The first thing that would happen is that the local DNS server would make a request to a root server for addresses in the .edudomain. There are multiple copies of root servers throughout the world that do nothing but serve up addresses in top level domains. This root server would then provide the address for a DNS server that had the address for the second level domain uchicago.
In Figure 4–7 this is the server with the address 128.135.4.2. This server knows all of the addresses of host machines for the uchicagodomain including the host machine gsbkip. It then responds to the local DNS, sending it the IP number 128.135.130.201, which is the IP address for the domain name gsbkip.uchicago.edu. The local DNS server then passes that IP number to the desktop PC that originally made the request. It now has an IP address associated with the domain name gsbkip.uchicago.eduand can send packets out over the Internet requesting files from the server (labeled enterprise Web server in the figure) with this domain name. All of this happens in a matter of seconds or even less. Simple!
)
Figure 4--7 Domain name resolution.
Clearly, in order for the process outlined in Figure 4–7 to work properly, the IP addresses and domain names must be globally unique. The organization entrusted with ensuring this is the Internet Corporation for Assigned Names and Numbers (ICANN). This organization was established by the United States Commerce Department for the purpose of making the Internet run smoothly. At one time, Network Solutions Inc., which is now owned by VeriSign, had a monopoly on assigning domain names. They no longer have a monopoly on assigning domain names, but they still have control of the domain name database for .comand .netand get $6 per year per name for maintaining this database. Now, if a company wants to register a domain name they can contact one of the ICANN Accredited Registrars. Many Internet service providers will, for a fee, take care of the process of getting an IP address and registering a domain name.
Many companies are discovering that if they want to register a domain name, the name is already taken. To help alleviate this problem, ICANN has approved seven new top level domain names. They are .aero, .biz, .coop, .info, .museum, .name, and .pro. Not surprisingly, there are companies trying to usurp the power of ICANN. One such company is New.net. They have come up with their own top level domain names like .family, .tech, and .normaltitle. However, because they are not approved by ICANN, their domain names are not part of the root server system. In order to reach host computers using the New.net domain names, a user, or the user's Internet service provider, must use special software that adds the extension new.netonto every address [29].
CYBERSQUATTING
Cybersquatting is the practice of registering a domain name for the purpose of reselling it at a later date. Early in the domain name registration process, clever individuals registered domain names related to well-known products or company names, e.g., Mcdonalds.com, with the express purpose of charging a large ransom fee on the name when the company finally decided to use it. This is also called domain name hijacking. This is now much more difficult to do. In October of 1999, ICANN approved a set of rules for the Uniform Domain Name Dispute Resolution Policy. This policy is followed by all domain name registrars for the top level domains of .com, .org, and .net. Victims of cybersquatting can make a formal complaint under this policy and be heard by an ICANN-approved dispute-resolution service provider. If someone has registered a domain name in ''bad faith,'' there is high probability he will be forced to give it up. We refer the reader to the ICANN Web site for what constitutes ''bad faith.''
How can New.net establish new top level domain names without being given the authority to do so? No government or company owns the Internet. Organizations such as the W3C try to provide standards on HTML and HTTP, and ICANN tries to control domain names and numbers, but there is no central worldwide authority. Perhaps that is why the Internet has worked so well to date.