Network - Internet
As a general term, an internet is an internetwork, which is a network consisting of two or more smaller networks that can communicate with each other. See the Internetwork article for a discussion of this type of networking. As a specific reference, the Internet (note the uppercase I) is the giant internetwork created originally by linking various research and defense networks (such as NSFnet, MILnet, and CREN). Since then, various other networks-large and small, public and private-have become attached to the Internet. With about a million registered nodes, many of which are servers for smaller networks, the Internet is by far the largest network in the world. Just a list of all 470 Internet INTERNAL ROUTING the nodes would be a book much larger than this one. The Internet, its ancestors, and its subnetworks have been the developing grounds for many of the most commonly used protocols and networking principles. For example, the TCP/IP protocol suite was developed as part of the ARPAnet project, which was a predecessor to many of the subnetworks, and also to the Internet itself. The Internet has a three-tiered structure: n The backbone is the highest level in the Internet hierarchy; it is the level that holds the entire Internet together. It consists of networks such as NSFNET and EBONE. The backbone will carry traffic and do routing for the intermediate (transit) level networks. Because this high-level traffic volume can get heavy, the backbone networks have a very high bandwidth. For example, the NSFNET runs over T3 lines, which have a bandwidth of about 45 Mbps. n The mid-level networks-also known as regional, or transit, networks-lie below the backbone. These carry data and do routing for the lower-level (stub) networks and for their own Internet Structure Internet 471 hosts. A mid-level network must have paths to at least two other networks. Examples of transit networks include NEARNET, PSINet and SURANET. A mid-level computer is sometimes known as a rib site because it's an appendage off the backbone. (How's that for rib-tickling humor on the Internet?) n The stub networks are basically local or metropolitan area networks. These carry packets only between hosts, but not between networks. This is the level with which most users communicate. A stub network may be connected to other networks, but will not carry traffic for them. Examples of stub networks include MHVNet and the Santa Cruz Community Internet. This structure is sketched in the figure "Three levels of Internet networks." The Internet grows very rapidly: at the rate of 10 to 20 percent per month. The number of networks branching off the Internet backbone more than doubled within a 16-month period. There are now over a million nodes, and planning is already underway for managing a billion-node internetwork. The IAB (Internet Architecture Board, formerly Internet Activities Board), which oversees standards and development for the Internet. This board also administrates, with the help of the IANA (Internet Assigned Numbers Authority), the internet(1) subtree Internet Organizations in the global tree in which all networking knowledge is stored. The IANA is responsible for assigning values for networks, attributes, and so on. This service, which is operated by the University of Southern California Information Sciences Institute (USC-ISI) makes sure that the same identifier values are not assigned to two different entities. The IAB has two task forces: IETF (Internet Engineering Task Force) and IRTF (Internet Research Task Force). The IETF is the committee largely responsible for formulating the Remote Network Monitoring Management Information Base (RMON MIB), which is expected to become the standard for monitoring and reporting network activity in the Internet environment. The IRTF works on long-term research projects. These projects may have to do with any aspect of Internet operations, and some results have led or may lead to major changes in certain aspects of Internet activity. Topics on which the IRTF has worked include how to increase the privacy of electronic mail, and how to make services available to mutually suspicious participants. The IESG (Internet Engineering Steering Group) is the executive committee for the IETF. The IRSG (Internet Research Steering Group) is the group that oversees the IRTF. The ISOC (Internet Society) is an international organization that promotes the use of the Internet for communication and collaboration. It provides a forum for the discussion of issues related to the administration and evolution of the Internet. The ISN (Internet Society News) is the official newsletter of ISOC. The figure "Internet administrative 472 Internet layout" shows how these various committees and groups are related. There are hundreds (possibly thousands) of services and resources available on the Internet. These include the following: n Electronic mail (e-mail) n Remote login services (Telnet) n Special interest and other discussion groups and forums (Usenet) GETTING IN TOUCH WITH THE ISOC You can write, phone, fax, or send e-mail to ISOC: n The Internet Society; 1895 Preston White Drive, Suite 100; Reston, VA 22091; USA n Telephone: (703) 648-9888 n Fax: (703) 620-0913 n E-mail: isoc@nri.reston.va.us THREE LEVELS OF INTERNET NETWORKS 1 = Backbone 2 = Mid-level 3 = Stub 1 2 3 3 2 2 2 2 3 Internet 473 n File retrieval and transfer services (FTP) n Various services to find files, interest groups, and even individual users (including Archie, Veronica, Jughead, Gopher, Finger, and World Wide Web, or WWW) n Magazines, news services, directories, and other information (including White Pages Directories and mailing lists) n Real-time, node-to-node or conference communications (Talk and Internet Relay Chat, or IRC) n Games, jokes, and other diversions for passing, enjoying, or wasting your time The following is a very brief summary of some of the more commonly used services and resources on the Internet. Just a list of the Usenet discussion groups runs longer than 50 pages in small print. Archie: A service for gathering, indexing, and displaying information (such as a list of the files available through anonymous ftp). See the Archie entry for information about specific Archie clients and servers. Browsers: Programs that can read hypertext files, such as those found on the World Wide Web (WWW). Various browsers are available, ranging from the line- and text-oriented Lynx to the graphics- and multimedia-browsers such as Mosaic and NetScape. See the entry on browsers and entries for specific browsers for more information. Finger: A service that can provide information about the person associated with a particular userid. INTERNET ADMINISTRATIVE LAYOUT 474 Internet FTP: A program that allows you to transfer files between computers. Many Internet nodes contain files that are available to the general public through anonymous FTP. An FTP program is generally provided by Internet Access Providers as part of their basic software package. Gopher: A distributed service that can organize and provide access to hierarchically related information. The information can be in various forms: library catalogs, databases, newsgroups, and so on. Internet Hunt: A monthly information scavenger hunt in which participants try to find the answers to 10 questions using only resources available on the Internet. The Internet hunt is an excellent, fun, and nonthreatening way to learn about the Internet and its available services and resources. IRC (Internet Relay Chat): A service that extends Talk capabilities to allow multiparty conversations. Jughead: A service that helps make certain Gopher searches easier and more manageable. Lycos: A tool for searching for documents on the World Wide Web (WWW). Lycos is a search engine with information on over 6 million Web documents. Mail: A very basic mail service developed for UNIX systems, but also available on the Internet. Other mail programs are easier and/or more powerful. These include Elm and Pine (for UNIX) and Eudora and Pegasus (for Windows). MUDs: These multiuser dimensions (or dungeons) are sophisticated descendants of earlier dungeons and dragons games. MUDs and related resources (MUSHes MOOs, MUSEs, etc.) provide interactive games or virtual environments in which players can assume roles or characters, can manipulate simulated environments (labs, societies, etc.), or just socialize. Each MUD environment has its own client and server programs. News: Various newsreaders (programs for searching and reading news items) are available on the Internet. UNIX newsreaders include rn (read news), nn (no news, a more selective newsreader), and tin (threaded Internet newsreader). Windows newsreaders include News Xpress, WinTrumpet, and WinVN. Ping: A simple program that can be used to determine whether a connection is available between your machine and a specified other machine. You can also use Ping to test whether you're connected properly to your Internet Access Provider. Players: Programs for playing various kinds of audio or sound files. Players differ in the file formats they can handle, in the speakers and sound boards they support, and in the platforms on which they run. Example players for Windows include Wham and WPlany. Internet 475 Readers: Programs for interpreting and displaying the contents of formatted documents (such as PostScript files). Such programs must be able to understand formatting and layout commands and must also be able to translate these into instructions for displaying the material on the screen. Arguably, the best known reader is the one for Adobe Acrobat. Readers are essentially viewers (see below) for documents. Talk: A service that allows two users logged onto the Internet to communicate with each other in real time (subject to any transmission and routing delays). Telnet: A program that provides terminalemulation capabilities for logging in to a network from a remote location. Usenet: A loose network of thousands of discussion groups about various topics ranging from the mainstream and mundane to the esoteric and "out of this world," with some topics being even further out than that. Veronica: A service that helps make Gopher searches easier and more manageable. Viewers: Programs for displaying various types of graphics or video files. Viewers differ in the kinds of files they can handle, in whether they can handle compressed files (either on-the-fly or through preprocessing), and in whether they can handle animation or video formats. Viewers generally fall into one of three categories: those that can handle images (possibly compressed), those for displaying animation, and those for displaying video. Wais: A service that can be used to gather information about a topic from various locations and provide easier access to the information. White Pages Directories: Resources that provide electronic address listings for users on the Internet. WWW (World Wide Web): A giant information network containing millions of hypertext documents that are accessible through Web server programs. To access and read or print such documents, users need a browser program that can request the documents from the server and display them for the user. The WWW is currently the fastest growing segment of the Internet as individuals and corporations are discovering the advantages of putting their own Web pages (hypertext documents) on the Web. WWWW (World Wide Web Worm): A search engine for finding hypertext documents on the Web. WWWW can search for keywords or keyword combinations in titles, authors, or contents of the documents, and will display the addresses of documents that match your search criteria. WWWW has information about more than 3 million documents.