What is the Internet? by Paul Jones Office for Information Technology University of North Carolina Chapel Hill, NC (paul_jones@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. T hus 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 catalog ues 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@lambada.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 lambada 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 ISO country codes are used for most countries other than the US. For example cl for Chile, pl for Poland, za for South Africa. 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 supercomputer 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 laUNChpad bulletin board system, you'd type: telnet launchpad.unc.edu or telnet lambada.oit.unc.edu NOTE that we've made two names that direct you to the same computer. The first is the name of the service so that you only need to know what service you wish to use. The second is the name of the computer on which laUNChpad lives. then login: launch and follow the instructions for using laUNChpad. Notice that the lambada.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 lambada.oit.unc.edu by IP address, you'd type: telnet 152.2.22.80 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 152.2.21.8) 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. A Short Guide to Anonymous ftp How to access to White House Papers and other useful information on SunSITE.unc.edu 152.2.22.81 Introduction A great deal of useful information is stored in files at computers throughout the world. Many of these files are freely available to you as a member of the Internet. A simple method for transferring such files from a remote computer to a user's computer is anonymous ftp. Anonymous ftp allows a user to transfer files without having an account on SunSITE (i.e. the user is anonymous.) SunSITE uses a special version of the ftp program from Washington University - St. Louis that displays README files that describe each directory level of the archives as you move through the archives' file directory. This will help you find the programs, documents, and data items that you want to retrieve fairly easily. How Do I Access the Anonymous ftp files at SunSITE.unc.edu? An example of connecting to the SunSITE.unc.edu anonymous ftp site follows: ================================================================== EXAMPLE: % ftp sunsite.unc.edu (you type this at your local computer) Connected to sunsite.unc.edu. 220 SunSITE is from UNC & Sun.Read DISCLAIMER.readme for our legal disclaimer Name (sunsite.unc.edu:pjones): anonymous (you type anonymous) 331-Guest login ok, send e-mail address as password. 331 Begin your password entry with a - (dash) to suppress the helpful messages. Password: pjones@lambada.oit.unc.edu (please use your own mail address) 230- WELCOME to UNC and SUN's anonymous ftp server 230- University of North Carolina 230- Office of Information Technology 230- SunSITE.unc.edu < a few introductory lines deleted> 230- An OpenLook FTPtool can be found in 230- /pub/X11/Openlook/Ftptool4.3.unc.1.tar.Z 230- This is the top directory!! cd pub will take you to the good stuff. 230- 230-Please read the file README 230- it was last modified on Thu Aug 20 23:14:18 1992 - 7 days ago 230 Guest login ok, access restrictions apply. ftp> =================================================================== Once you have gained access to SunSITE, the ftp> prompt returns and acknowledges that the system is ready to use. Listing the Directories and Changing Directories Once you have connected to Sunsite, to transfer a file, you may have to change directories to reach the directory that includes the files in which you are interested. In the example below the user has typed in the commands that follow the ftp> prompt in order to retrieve a file named Nato-Statement from SunSITE. ================================================================== EXAMPLE: ftp> cd pub 250- UNC Sun Archive - /pub - top level directory 250- 250-X11/ interesting packages that run under X-Windows 250-academic/ software written by researchers in different disciplines 250-archives/ archives of mailing lists and Usenet newsgroups 250-bbs/ the source to utilities running on the internet bbs 250-docs/ a large selection of documents, books, speeches, papers, etc. 250-gnu/ Unix Software written by the Free Software Foundation. 250-books/ entire books for download 250- 250 CWD command successful. ftp> ls 200 PORT command successful. 150 Opening ASCII mode data connection for /bin/ls. README academic sun-sounds docs DISCLAIMER.readme X11 terminal-emulators 226 Transfer complete. 231 bytes received in 0.051 seconds (4.4 Kbytes/s) ftp> cd academic/political-science (this moves you down two directory levels in one command). ftp> ls (this lists the contents of the directory) 200 PORT command successful. 150 Opening ASCII mode data connection for file list. whitehouse-papers .cache speeches 226 Transfer complete. 37 bytes received in 0.75 seconds (0.05 Kbytes/s) ftp> cd whitehouse-papers/1993 (again we go down two since I already know where I'm going). ftp> ls 200 PORT command successful. 150 Opening ASCII mode data connection for file list. Feb Jan .cache Mar 226 Transfer complete. 23 bytes received in 0 seconds (18.35 Kbytes/s) ftp> cd Mar (this takes us to the March 1993 White House Papers) ftp> ls (this list the files in the directory) 200 PORT command successful. 150 Opening ASCII mode data connection for file list. Remarks-by-the-President-in-National-Service-Address Remarks-by-the-President-in-Discussion-w--Nat-Serv-Vols Nato-Statement Statement-on-Haiti-3293 ftp> get Nato-Statement (this grabs the file for you and puts it on your computer using the same name, Nato-Statement). 200 PORT command successful. 150 Opening ASCII mode data connection for Nato-Statement (1685 bytes). 226 Transfer complete. local: Nato-Statement remote: Nato-Statement 1725 bytes received in 0.01 seconds (1.72e+02 Kbytes/s) ftp> quit 221 Goodbye. ================================================================== Some Useful ftp Commands for SunSITE Unix directories are hierarchal. In the example above some simple Unix commands were used to change directories and list possible directories or files (i.e. move up or down the hierarchy.) the ls command lists the contents of the active directory the cd command enables the user to change directories (move up or down the hierarchy) the cd .. command allows the user to return to the previous directory, using this command it is possible to return to the initial directory the get command retrieves files from SunSITE the put command places files on SunSITE. Note that this will ONLY work within the uploads directory. the binary command sets the transfer type for binary files. You should always issue the binary command before retrieving compiled programs or files with endings of tar or Z. A Note About Special File Types in the SunSITE Archives You will notice that many of the files on SunSITE have special endings such as .Z .tar .zip .hqx and .sit Such files have been compressed and/or specially encoded to allow them to be more quickly and easily transfer in working order via ftp. It is a good idea to use the binary command before attempting to retrieve any of these file types. .Z files have been compressed using the UNIX compress command. Once you have retrieved a file with the .Z suffix, you should use the UNIX uncompress command which will create a new file (uncompressed and larger than the original) without the .Z ending. .tar files are usually a collection of several related files and directories combined as one file for transfer or archiving by the UNIX tar (tape archive) command. Once you have retrieved such a file, you should use the tar -xvf command to extract the files and directories from tar format. The file will remain on your local computer even after the extraction has successfully completed. It is a good idea to remove the tar file after extraction. .zip files are usually files for pcs running DOS or Windows that have been processed by the zip program. Use the unzip program (or pkunzip) to make such files usable. .hqx files are usually Macintosh files that have been converted to binHex format for files transfer or archiving. Use the binHex program's download option to convert .hqx files to a usable format. .sit files are usually Macintosh files and folders that have been combined and compressed for transfer and archiving (much like tar files in UNIX). Use the StuffIt program to unpack such files and folders. Select Bibliography * indicates that these documents are available via anonymous ftp from sunsite.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 supercomputers, 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. NOTE since this paper was produced (about four or five years ago now) there have been several new books that assist in exploring the Internet. Be sure to check the files in pub/docs/about-the-net/internet-tutorials on sunsite.unc.edu for later more up-to-date on-line free documents.