COMPUTER NETWORKS SERVING UNIVERSITY NEEDS By Hamed Nassar EE Department New Jersey Institute of Technology hxn8477%njitx.decnet@njitc.njit.edu Although it was designed to be a computing tool, the computer is becoming more and more a powerful means of communication. People today use computers to exchange mail, move files from one place to another, chat with each other, access information centers and remote databases, and attend conferences. When computers are connected to form what is called a network, all these functions are possible. Computers may be connected through standard electrical wires, coaxial cables, optical fibers, radio channels or satellite links. A network may use one or more of these communications media to tie together what would otherwise be isolated sources of data. A computer on such a network may be called a node, machine, host or site. A computer may be connected to two networks. This allows it to communicate with a greater number of other computers. More importantly, this computer can be used to transfer traffic from one network to another, acting as a GATEWAY. For the computers on a given network to send and receive data, they must use an agreed upon set of communications rules. This set of rules is called a COMMUNICATIONS PROTOCOL or simply a protocol. NETWORK SERVICES Among the services that networking makes available are: Electronic Mail: For the average user, this is probably the most tangible and interesting service a computer network can offer. A network user has an e-mail address and a mailbox. An e-mail address usually takes the form user@node, where user is the user's ID and node is the name of the computer used. As with ordinary (paper) mail, two network users can send messages to each other regardless of the physical distance that separates them. However, electronic mail is much faster and more convenient. For example, a message can be sent from a desk in the U.S. to Europe and a reply received in just a few hours. Interestingly, one cannot receive an anonymous electronic letter, for computer mail programs stamp an outgoing letter automatically with the name of the sender and the date and time it was sent. File Transfer: For business, military and educational applications, rapid sharing of computerized information is considered vital. Using network file transfer capabilities, an individual on one computer can access another computer and send or retrieve files quickly and easily. This eliminates the need for having to package disks or tapes, and avoids the delay, expense and risks associated with ordinary mail. Remote login: This allows a person on one computer to log into, and communicate in real-time with another remote computer, as if connected to a direct terminal. The person may then execute a program, read some on-line information,, or participate in a computer-mediated conference. Distributed bulletin boards: A distributed bulletin board can be visualized as information in the form of articles, messages, or announcements, posted on the network. The information is usually contributed by and intended for the users. The contents may be anything form a serious discussion about a scientific problem, to an entertaining joke about a show business personality. A network may offer one or more of the above services, depending on the sophistication of its hardware and software and the need of its users. We at NJIT are fortunate to be on a network that offers all of the above services, as will be explained later. Because of these important services, computer networks have proliferated dramatically over the past two decades. The networks operational today can be put in four categories: 1. Public (commercial) networks, such as Telenet and Tymnet. These networks are accessible to anyone through the regular telephone network. They connect a wide range of commercial and noncommercial organizations and services around the world. 2. Research (academic) networks, such as the Internet and Bitnet. These networks are accessible only to organizations conducting research activities, such as universities, research centers, and companies with R&D divisions. 3. Cooperative (home brew) networks, such as UUCP and Fidonet. These networks are collaborative efforts of computer enthusiasts who share a desire to communicate with various computers. As such, they have no central administration and their operation can be chaotic at times. There is no restriction on accessibility. 4. Private networks. These are limited to use within an organization. They can be Local Area Networks (LAN), such as our Decnet at NJIT, or Wide Area Networks (WAN) such as IBM's worldwide Vnet. In this article we examine only the research and cooperative networks. RESEARCH NETWORKS The DARPA Internet: This is by far the largest, most complex, and most efficient research network in the world. Administered by the Defense Advanced Research Projects Agency(DARPA), this giant web of computers currently spans about half the globe. The Internet is not just a network; it is a network of networks. Among the constituent networks, which are linked to each other by dedicated gateways, are: 1. The Arpanet: This was the the first Packet Switching Network (PSN) in the world. (Packet switching is the technology that has really made computer networks economically feasible). It started in 1969 within the Department of Defense (DoD) as a research project under the supervision of the Advanced Research Projects Agency (ARPA, which later became DARPA). The intent was to explore the field of computer communications, but the Arpanet soon evolved into a sophisticated network linking a large number of computers. 2. Milnet: As its name implies, this is a military network, linking together bases, offices, and arsenals. Nevertheless, the network is unclassified and access to it is readily available. Currently, the Arpanet and Milnet make up a major part of what is called the Defense Department Network (DDN). 3. NSFnet: This was set up in 1986 to link research groups, in particular projects supported by the National Science Foundation. NSFnet is made up of seven regional networks, each of which is built around a national supercomputer center. A backbone network connects all seven centers, thereby linking their respective regional networks. NJIT is in the regional network of the Jon von Neuman Supercomputer Center. 4. CSnet X25Net: The CSnet was created to foster communication among researchers in computer science. It has two major components: X.25net, which is built on top of Telenet, and Phonenet, which is a dial-up central message relay system based at BBN in Cambridge, Massachusetts. Only the first wing is part of the Internet The communications protocol on the Internet is called Transfer Control Protocol/Internet Protocol (TCP/IP). It is a set of specifications and rules that insure reliable and efficient data transmission from the source to the destination. The remote login and file transfer capabilities are provided on the Internet through the Telnet and FTP protocols, respectively. The bulletin board service is available on the Internet in the form of mailing lists, with each list concentrating on a specific topic. Bitnet (Because It's Time Network): This started in 1981 as a link between the City University of New York (CUNY) and Yale University. It has since expanded to include the European Academic Research Network (EARN) and the Canadian NetNorth network. Today it includes over 4000 hosts in approximately 800 organizations (mainly universities and research centers) around the world. For e-mail exchange purposes, there are gateways between Bitnet and the Internet. At this writing there are three official gateways: cunyvm.cuny.edu, mitvma.mit.edu, and cornellc.ccs.cornell.edu. Bitnet supports file transfer and distributed bulletin boards (called discussion groups) using dedicated file and list servers. There is a limited real-time communications capability but no remote login. There are many other lesser known research networks such as Bionet, Span, and Hepnet in the US, CDNnet in Canada, FUnet in Finland, Janet in Britain, Junet in Japan, Estnet in Egypt, and Uninett in Norway. COOPERATIVE NETWORKS UUCP (Unix to Unix Copy Program): UUCP is the creation of some unix wizards and computer hackers. Computers on this network (called sites) use the telephone network to dial up each other and exchange communications. With over 5000 sites today in around 50 countries, this network offers modestly reliable e-mail services. A backbone site in UUCP is one of about four dozen sites, half of which are in the US. These sites carry the network traffic for large distances (e.g. between the two coasts of the US or between two European countries). Sites in the same area can get or send traffic for reasonable telephone charges. Almost all the American backbone sites of UUCP are also on the Internet, and most of them act as gateways between the two networks. Some such gateways are uunet.uu.net, bellcore.bellcore.com and gatech.edu. Joining UUCP is as easy as finding an existing site that is willing to provide a connection (feed) to the new site. Once limited only to unix machines, today it is not necessary to be running Unix to join UUCP. A PC running MS-DOS can be a UUCP site, by running a Unix-compatible communications utility on top of DOS. Two such utilities are UUPC and UULINK. On top of UUCP is a very interesting bulletin board called USENET (User's Network). Usenet is organized into hundreds of News Groups, each focusing on a special topic. The topics vary widely, ranging from computers, history and astronomy, to match- making and jokes. Literally thousands of articles are sent and read daily by an estimated half million users around the globe. Fidonet: Although today one can have access to UUCP with a PC, the MS-DOS community has started a network of its own, Fidonet. Like UUCP, Fidonet depends on phone dial-ups between neighboring sites to exchange news and mail traffic. The traffic moves from site to site until it reaches its destination, which may be thousands of miles away. Although new, Fidonet has become so popular that there are nodes not only in almost every American and European city, but also in countries as distant as Japan an Indonesia. Joining Fidonet is as easy as finding a feed from an existing node, preferably close by to save on phone bills. The Fido software is available in the public domain. What can we access at NJIT? NJIT has hosts on three major networks. First, all NJIT computers have access to the Internet through VAX/VMS computers. If you have a computer account, you have a unique e-mail address consisting of your user ID, the name of the computer and a gateway to the Internet. Suppose you have an account on ADMIN1 with the user ID "nancy". Your e-mail address then is nancy%admin1.decnet@njitc.njit.edu People can send you mail from the six continents at this address. Conversely you can send mail to people on almost all other research and cooperative networks. FTPing is available on NJITC and Mars, whereas Telnet is available on Mars and on the terminal servers. The mailing lists are available on all computers. NJIT also has two UUCP sites: Mars and Argus. However, USENET is available only on Argus. If your user ID on Mars is teddy, then your uucp (old style) address is bellcore!argus!mars!teddy All sites on UUCP know how to get to bellcore because it is a backbone site. The third network to which NJIT is connected is Bitnet; the node name is Orion. If your account name on orion is jack12 then your e-mail address is jack12@orion This works within Bitnet; but from other networks, gateways must be used as explained above. ACKNOWLEDGEMENTS The author would like to thank all of those who supplied information used directly or indirectly in this article. Special thanks are due to Dr. John Carpinelli, Steve Keeton and Brian White of NJIT; Dr. John Klensin of MIT; and Francine Perillo of NIC.