An IP address is made up of a series of numbers that are divided into four groups, or octets, separated from each other by a decimal point (an example being 216.182.167.200). The first (and sometimes the second and third) octet of an IP address represents the network on which the host is located, and the other octets identify the host itself.
Since the late 1980s the number of hosts accessing the Internet has grown so rapidly that by 1995 a new generation of IP was designed, primarily owing to the prediction that the total number of addresses that the current IP allows would be exhausted by the year 2000. The newer IP, officially IP version 6, can provide up to 2128 addresses, a virtually infinite supply.
However, in the late 1990s, through a combination of more conservative IP address allocation and the introduction of technology permitting the reuse of addresses, the demand for additional addresses slowed. Consequently, it was predicted that conversion to IP version 6 would probably not be needed until 2010 or later.
Domain Naming System
Rather than require users to type in an IP address in order to direct e-mail to a specific host or to locate a Web page (discussed below), the Internet employs the domain naming system (DNS), which transforms IP addresses into more easily remembered words and letters. Internet hosts are assigned within the DNS to one of several basic "domains," including government (abbreviated gov), military (mil), educational (edu), commercial (com), nonprofit organization (org), network operator (net), business (biz), information service (info), cooperative (coop), museum (museum), aeronautical organization (aero), professional service (pro), and individual person (name). In addition, there are several hundred geographic domains that exist, such as Canada (ca), Japan (jp), and Antarctica (aq).
A name within a domain is appended to the front of the address, as, for example, in whitehouse.gov (for the U.S. White House), ucla.edu (for the University of California at Los Angeles), and ibm.com (for the International Business Machines Corporation). Subdomains also are commonly used, to indicate a more specific address. For example, eecs.berkeley.edu is the host for both the electrical engineering and computer sciences divisions at the University of California at Berkeley. Once a user sends an e-mail message, the Internet utilizes a domain name server to translate the DNS address back into an IP address for the network computers to read.
Uses of the Internet
Tasks performed on the Internet, including the transmission of person-to-person e-mail and the transfer of files between computers, parallel those that are carried out on smaller computer networks. It is the vast size of the Internet that adds to the complexity of accomplishing these particular tasks.
E-mail. By the early 21st century, billions of e-mail messages were being routed over the Internet each day. E-mail transmissions utilize the simple mail transfer protocol (SMTP). The addresses to which they are sent take the form userid@host, in which host indicates the name (assigned via the DNS) of the computer or group of computers that is receiving the message and userid identifies a specific individual or group accessing that computer.
File Transfer. Another significant use of the Internet is the electronic transfer of documents and other filed data between computers. This is accomplished using the file transfer protocol (FTP). The protocol can also be used to distribute both free and commercial software over the Internet.
USENET Discussion groups have thrived over USENET (short for users' network), also known as Netnews, a worldwide electronic system employed by the general public to post messages on topics of special or general interest. The messages, referred to as articles, appear in USENET discussion forums known as newsgroups, which are typically dedicated to specific topics. Although USENET articles are sent over the Internet, non-Internet computer networks transmit them as well. Therefore, while USENET makes use of the Internet, it is not, strictly speaking, an actual part of the Internet.
Each of the thousands of existing newsgroups has a hierarchically constructed name. For example, the newsgroup comp.arch, which is one of a large number of newsgroups about computers (comp), was created specifically for the discussion of computer architecture (arch). Similarly, the comp.lang.c++ newsgroup was devised for often arcane discussions on the C++ programming language, while the misc.computers group was developed for miscellaneous (misc), and relatively simple, computer-related questions and discussions. Other examples of newsgroup abbreviations include soc, for newsgroups oriented toward social issues (such as soc.culture.japan), and rec, used by recreation-related groups (such as rec.sport.hockey).
USENET operates by way of specialized protocols that transmit a news feed (that is, a batch of articles) to a server. A program called a news reader lets a client see the list of newsgroups available on the server and gives the client access to specific articles. It also enables articles to be sent from the client to a newsgroup.
