What is the Internet? by Paul Jones Office for Information Technology University of North Carolina Chapel Hill, NC (pjones@samba.oit.unc.edu) Permission to reprint and distribute given only if this attribution is also given. "In the beginning there was the ARPAnet, a wide area experimental network connecting hosts and terminal servers together. Procedures were set up to regulate the allocation of addresses and to create voluntary standards for the network. As local area networks became more pervasive, many hosts became gateways to local networks. A network layer to allow the interoperation of these networks was developed and called IP (Internet Protocol). Over time other groups created long haul IP based networks (NASA, NSF, states...). These nets, too, inter-operate because of IP. The collection of all of these interoperating networks is the Internet. " So begins The Hitchhiker's Guide to the Internet, a text prepared in 1987 by Ed Krol. Since those ARPAnet days, the Internet has grown and divided without losing interoperability, allowing researchers, scholars, students, and even introverted computer nerds to interact with thousands of their peers around the world. As of August 1989, there were over 118,000 sites (computers) directly connected to the Internet. Each site has from 2 or 3 to several thousand people using the computer at that site. Thus the Internet has a population size close to that of a major city. The resources of this city include some of the world's fastest super-computers, some of the world's most sophisticated computer software (which is often shared), library card catalogues of many major universities, and often intelligent discussions with experts (accredited and self-proclaimed) on every subject under the sun. The major means by which this "massive information highway" serves its participants is by the support of the three "canonnical" applications: electronic mail (mail), file transfer (ftp), and remote login (telnet). These applications will be briefly covered in this document along with a few suggestions for you to try out. Mail (aka SMTP) Mail, often called SMTP or Simple Mail Transfer Protocol, is probably the most used Internet service. While the mail interface (what you see when you type mail on your computer) may be different on each computer (see your local support folks for details), the means by which Internet computers deliver mail is standardized, as is the way by which you address other people on the Internet. Unlike certain other networks with which you may be familiar (UUCP and BITNET), Internet mail is either delivered directly to the recipient or sent through a small number of gateways which are usually hidden from the person originating the message. Under this scheme, mail is much less often held up due to a computer being "down" somewhere between you and your correspondent. Of course, telephone and other communication lines could still be a source of delay, but in general SMTP mail is delivered much faster. pjones@samba.oit.unc.edu is my mail address. Let's look at how it is composed. pjones my user logon id @ separates the user from his address samba my computer's name (ours are named after lively dances) oit my department (Office FOR Information Technology) unc my organization (University of North Carolina) edu Internet domain (edu for educational institutions) Other Internet domains are: com commercial operations gov government agency mil military sites net network centers org organizations that fall between the cracks When you think of it, the address is a lot like an address on a letter, moving from most specific to most general. That's how postal systems delivering paper mail worldwide work and how the Internet works, too. Ocasionally you may need to use "gateway addressing" in order to reach people on networks other than the Internet. To reach BITNET sites, you may send to user@site.BITNET or you may need to specify a gateway (if your systems folks are new or lazy) by sending to user%site.bitnet@cunyvm.cuny.edu. In general, most sites hide gatewaying from their users and make your life easier. All major networks can send and receive mail from the Internet so you need not fear losing communication with your friends on the other nets by using Internet mail. Logging on to other computers on the Internet (telnet and tn3270) You may be working with people at another site, you might want to use a database in another state, you might need the power of a super- computer to assist you in your research, or you might want to browse a library card catalogue at another institution. You can do all this on the Internet without the expense of a long distance telephone call. telnet, also known as remote virtual terminal, allows you to log on to computers on the Internet by using the same form of address you saw above in the Mail section. telnet can emulate any terminal type that you can emulate locally, but it is most often a vt100 emulation or a Tektronics 40xx emulation for graphics. If you want to log on to an IBM computer running the VM or MVS operating system, you'll need a special version of telnet called tn3270 which emulates an IBM full screen 3270 terminal. To connect to the UNC ACS bulletin board system, you'd type: telnet samba.oit.unc.edu then login: bbs and follow the instructions for using bbs. Notice that the samba.oit.unc.edu is the same computer you saw in my mail address; the information to the right of the @ is the computer's name. However, Internet connections may also be made by using an IP address instead of a name. The IP address is a group of four numbers separated by periods. If your computer does not run the Internet name service program, you will need to use IP addressing for telnet and ftp. To connect to samba.oit.unc.edu by IP address, you'd type: telnet 128.109.157.30 To connect to the University of California's Library Service, you'd type: telnet melvyl.ucop.edu To connect by IP address, you'd type: telnet 31.1.0.11 From there you'll be given local prompts to help you use the MELVYL system. Another service you may reach via telnet is VideoText. By typing telnet uncvx1.oit.unc.edu ( or by IP address, telnet 128.109.157.1) and logging on as info, you may access the University of North Carolina's info video text system, a system that will allow you to locate faculty, staff and students at UNC Chapel Hill, to check for job openings, and to review the campus calendar. (As I write this you must emulate a vt100 in order to make full use of info). Moving data on the Internet (ftp) Suppose you have a document on another computer and you need to have it on the computer you're now using. You may use the resources of the Internet for very high speed file transfer to copy that document from the other computer to the computer you are using now--even if the computers are on different continents--without the expense of a telephone call. Authorized folks may access files on any computer that allows such file access, but only if the owner of the files gives permission to access them. There is much information on the network that is open to the public. ftp, file transfer protocol, uses a subset of UNIX commands to allow you to change file directories - cd; list a directory's members - ls; show your current directory - pwd; as well as retrieve - get and send - put files. You may use the help command to learn more about other ftp commands. There is a special user id used on the Internet called anonymous. This is used to make certain files available to everyone on the Internet. We use anonymous ftp at UNC to make documentation and support files available to people on our campus, but we welcome others on the Internet to use them, too. Here is a sample ftp session in which a file called library.guide (a guide to library card catalogues accessible on the Internet is retrieved from samba.oit.unc.edu. You would type the commands that follow the ftp> prompt after initiating a session by using the ftp command. (Remember you could use the IP address of 128.109.157.30 instead of samba.oit.unc.edu.): ftp samba.oit.unc.edu Connected to samba.oit.unc.edu. 220 samba.oit.unc.edu FTP server (Ultrix Version 4.36 Thu Dec 29 22:53:11 EST 1988) ready. Name (samba.oit.unc.edu:pjones): anonymous 331 Guest login ok, send ident as password. Password:type your id here--it will be hidden 230 Guest login ok, access restrictions apply. ftp> ls 200 PORT command successful. 150 Opening data connection for /bin/ls (128.109.157.70,4260) (0 bytes). bin pub uploads 226 Transfer complete. 36 bytes received in 0.23 seconds (0.15 Kbytes/s) ftp> cd pub 250 CWD command successful. ftp> ls 200 PORT command successful. 150 Opening data connection for /bin/ls (128.109.157.70,4261) (0 bytes). docs msdos unix vms 226 Transfer complete. 103 bytes received in 0.21 seconds (0.48 Kbytes/s) ftp> cd docs 250 CWD command successful. ftp> ls 200 PORT command successful. 150 Opening data connection for /bin/ls (128.109.157.70,4262) (0 bytes). hitch.hiker library.guide other.anonymice tcpip.intro 226 Transfer complete. 188 bytes received in 0.11 seconds (1.64 Kbytes/s) ftp> get library.guide 200 PORT command successful. 150 Opening data connection for library.guide (128.109.157.70,4263) (45172 bytes). 226 Transfer complete. local: library.guide remote: library.guide 46571 bytes received in 0.66 seconds (69.02 Kbytes/s) ftp> quit The file other.anonymice contains a list of over 200 sites that make software and documents available to people on the Internet. Select Bibliography * indicates that these documents are available via anonymous ftp from samba.oit.unc.edu or nic.ddn.mil Comer, Douglas. Internetworking with TCP/IP. Prentice Hall, Englewood Cliffs, NJ: 1988. Used to teach networking by our CS department. Technical view of the underlying protocols. UPDATE: now in two volumes, this book now deals more deeply with newer expanded network operation. Frey, Donnalyn and Rick Adams. !%@:: A Directory of Electronic Mail Addressing and Networks. O'Rielly and Associates, Inc. Sebastopol, CA: 1989 (nuts@ora.com). Cheap and good. About two pages with maps covering the world for each of over 130 networks. JAN 1992 UPDATE: much expanded after 2 editions. now includes a handy pocket guide (although I can't see that much use for it). Goos, Anke and Daniel Karrenberg. The European R&D E-Mail Directory. European Unix Systems User Group, Buntington, Herts, United Kingdom: 1989. (euug@inset.uucp or euug%inset@uunet.uu.net). Every campus user service should have this. A sort of yellow (they are actually green) pages of European addresses and postmasters with a very good introduction. Should be a newer version available than this one. Not cheap in the States. *Hedrick, Charles. Introduction to Internet Protocols (tcpip.intro on samba) Great brief technical overview. *Krol, Ed. Hitichhiker's Guide to the Internet (hitch.hiker on samba) once you've tried out some of the suggestions in this document get this one. LaQuey, Tracy. Users Directory of Computer Networks. Digital Press, Bedford, MA: 1990. Comprehensive and a good companion to Quarterman, but many of these lists of networks and hosts would be much more useful if available over the net so they could be searched electronically instead of printed on the bodies of dead trees. *NSF Network Service Center. Internet Resource Guide (in resource.guide directory) In both postscript and plain test format. This is the official guide and so lags behind the unoffical guides to libraries and super- computers, but trustworthy. Quarterman, John. The Matrix: Computer Networks and Conferencing Systems Worldwide. Digital Press, Bedford, MA: 1990. (matrix@longway.tic.com). The Bible. Every campus should be required to have this. Todino, Grace and Dale Dougherty. Using UUCP and Usenet. O'Reilly and Associates, Inc. Sebastopol, CA: 1989 (nuts@ora.com ) Handy guide for Unix folks, but not all that much to do with the Internet or the coming NREN. Waite Group. UNIX Communications. Howard W. Sams & Company, Indianapolis: 1987. Great users guide to various Unix network applications.