In the Beginning...

1. In the Beginning... • The Internet grew from a grass-roots society into a global community. • Usenet (Users’ Network) • Individual conferences organized by topics of interest such as: • World events • New technology • National elections • Privacy issues • Entertainment • Computer viruses • Generates over 100 meg of new text daily • Does not reside on any one computer Courtesy of: The Computer Continuum

2. Internet: Planting the Seed and Growing the Plant • Early 1960’s • Packet-switching envisioned (Baran and Davies) • Divide a message into a smaller pieces called packets. • Each packet contains where they came from and the address of where they are going. • Each packet is sent to its destination separately. • Provided the foundation for what became the Internet. • 1966: ARPA (Advanced Research Projects Agency) • Funded computer network research. Courtesy of: The Computer Continuum

3. Internet: Planting the Seed and Growing the Plant • ARPANET (Advanced Research Projects Agency NETwork) • Funded by ARPA. • Pooled computer scientists and resources from several universities. • In 1969, linked 4 nodes at UCLA, UC Santa Barbara, SRI (Stanford Research Institute) and U of Utah. • By mid-1970’s, linked several military sites and about 20 universities. • ARPA intended to sell off the ARPANET. • Transferred to the Defense Communications Agency in 1975. Courtesy of: The Computer Continuum

4. Internet: Planting the Seed and Growing the Plant • NSF (National Science Foundation) • In 1980, started CSnet. • Provided a resource sharing network for computer science research at all universities. • Used TCP/IP protocol. • Linked 5 supercomputing centers with a very fast connection called a backbone. • Each region surrounding the centers developed their own community network. • Each community network had exclusive access to the backbone. • Became known as NSFnet. Courtesy of: The Computer Continuum

5. Internet: Planting the Seed and Growing the Plant • In 1983, ARPANET split. • Part remained ARPANET: universities, research institutes. • Part became Milnet: non-classified military information. • Converted from Network protocol to TCP/IP protocol. • In 1989, majority of ARPANET switched to NSF’s backbone. • Became what is known as the Internet. • Early 1995: “Information Superhighway.” Courtesy of: The Computer Continuum

6. UNIX, Gurus, and Gophers • With the thousands of computers running the UNIX operating system, and freely distributed TCP/IP software suite: • Original access to the Internet had UNIX “feel.” • Exact addresses were needed to access information. • Addresses were strings of numbers • Address for UCSD: 128.54.16.1 • UNIX gurus “ran the net.” • Gopher (University of Minnesota): • Land of the “Golden gophers.” • Introduced first improvement to accessing the Internet. • Menu-driven system gave access to databases of information. • Were once over 5,000 gopher servers. Courtesy of: The Computer Continuum

7. UNIX, Gurus, and Gophers Internet Gopher Information Client v2.1.3 Home Gopher server: gopher.tc.umn.edu 1. Information About Gopher/ 2. Computer Information/ 3. Discussion Groups/ 4. Fun & Games/ 5. Internet file server (ftp) sites/ 6. Libraries/ 7. News/ 8. Other Gopher and Information Servers/ 9. Phone books/ 10. Search Gopher Titles at the University of Minnesota <?> 11. Search lots of places at the university of Minnesota <?> 12. University of Minnesota Campus Information/ Press ? For Help, q to Quit, u to go up a menu Courtesy of: The Computer Continuum

8. UNIX, Gurus, and Gophers • Searching for information on the Internet from Gopher: • Veronica: • Very Easy Rodent-Oriented Netwide Index to Computerized Archives. • Indexed the entries of all of the known Gopher menus. • Updated about twice weekly. • Archie: • Searched ftp archive sites. • These files were for downloading by using the Internet. • Has more than 1,000,000 filenames today. • Currently accessible through the WWW. Courtesy of: The Computer Continuum

9. The Internet Growing • Popular Internet functions illustrate the diversity of Internet use: • Information gathering: • University sites provide class and faculty information, books, library sources, lists of government documents • Employment offices could provide vacancy notices • Governmental agencies provide informational documents • Students and academic researchers could use online bibliographies Courtesy of: The Computer Continuum

10. The Internet Growing • MUDs - Multi-User Dungeons • MOOs - MUDs Object-Oriented • Both are an outgrowth of Dungeons and Dragons role playing games of the 70s and 80s. • Can play with people all over the world. • There are more than 500 active MUDs. Courtesy of: The Computer Continuum

11. The Internet Growing • IRC - Internet Relay Chat • “Real-time” online chat facilities • Communication is accomplished via typing text over a “channel” Courtesy of: The Computer Continuum

12. Communication Basics: The Physical Topology • Types of connection - Physical connection versus wireless. • Network: A Collection of computers, display terminals, printers, and other devices linked either by physical or wireless means. • Node: Any device on a network. Each device has a unique address assigned to it by the network. • Network links: Connections between computers and other electronic devices. Courtesy of: The Computer Continuum

13. Communication Basics: The Physical Topology • The physical media used to connect the networks are: Twisted pair, coaxial cable, fiber optic cable, and space. • Three types of wireless communication commonly used in networking: Infrared, Radio frequency, Microwave. Courtesy of: The Computer Continuum

14. Communication Basics: The Physical Topology • Three physical types of links used in networks. Courtesy of: The Computer Continuum

15. Communication Basics: The Physical Topology • Wireless communication. Courtesy of: The Computer Continuum

16. Communication Basics: The Physical Topology • Properties of Transmission: • Each link has common attributes • 1. Type of signal communicated (analog or digital) • 2. The speed at which the signal is transmitted. • 3. The type of data movement allowed on the channel. • Simplex transmission - One way transmission. • Half-duplex transmission - Can flow only one way at a time. • Full-duplex transmission - Two-way at the same time. • 4. The method used to transport the data – Asynchronous, synchronous. • 5. Single channel and multichannel transmission. Courtesy of: The Computer Continuum

17. Communication Basics: The Physical Topology • Type of signal communicated. • Analog - A continuously changing signal similar to that found on the speaker wires of a high-fidelity stereo system. • Digital - Signals consist of pulses of electrical energy that represent 0’s or 1’s. Courtesy of: The Computer Continuum

18. Communication Basics: The Physical Topology • Speed of signal. • In digital systems: Speed is measured in... • Bits per second (bps). • The number of bits (0’s and 1’s) that travel down the channel per second. • Baud rate • The number of bits that travel down the channel in a given interval. • The number is given in signal changes per second, not necessarily bits per second. Courtesy of: The Computer Continuum

19. Communication Basics: The Physical Topology • MODEM - MOdulator DEModulator • Outgoing: Converts binary data from computer (digital) into telephone compatible signals (analog). • Incoming: Converts telephone signal (analog) into binary data for the computer (digital). • Can be an external or internal device (usually a “card”). Courtesy of: The Computer Continuum

20. Communication Basics: The Physical Topology • Speed of Signal: Sample bps and baud rate speeds. 300 bps (=300 baud) Painfully slow to the college-level reader 1200 bps (=1200 baud) Good reader can keep up 2400 bps (=2400 baud) A speed reader would get the general idea 9600 bps (=9600 baud) Impossible to read 14.4 K bps (not measured in baud) 14,400 bps 28.8 K bps Minimum desired for WWW (needed for receiving images and sound) 33.6 K bps 56 K bps Download speed is 56 K bps. Sending speed is much less. These speeds are restricted to the maximum speed of the modem at the other end of the connection. If the Internet connection modem is limited to 28.8 K, then even if your modem is 56 K, it is limited to the 28.8 K speed! Courtesy of: The Computer Continuum

21. Communication Basics: The Physical Topology • Linking Computers Together - • Network - 2 or more devices are linked together. • Node - Individual devices on the network. • Direct link networks - One whose nodes have direct connections through either physical or wireless links. • Point to point link - Simplest of networks where a connection is made between computer systems. • Ways to link the nodes of a network: • bus, ring, star, tree, and the fully connected topology networks. Courtesy of: The Computer Continuum

22. Communication Basics: The Physical Topology • Networks not directly linked: • Internetworking - (Hybrid networks) • Linking any type of direct linked networks together. • Can be as small as connecting two computers together to as large as the largest of all, the Internet. • Demand special software to allow information to be exchanged between them. Courtesy of: The Computer Continuum

23. Communication Basics: The Physical Topology • Categorizing networks according to size: • DAN (Desk Area Network) • LAN (Local Area Network) • MAN (Metropolitan Area Network) • WAN (Wide Area Network) Courtesy of: The Computer Continuum

24. The Software Architecture of the Network • Problem: • Connect several different machines running different operating systems (Windows, OS/2, MacOS, UNIX, VMS..) • Now, try to: send email, data or files between them. • Solution: • Create a set of rules, or protocols, that, when followed, will allow an exchange of information. • Sometimes in a collection of programs called a protocol suite. • Network Architecture: The overall organization of the rules of the network and is implemented in a set of programs called the protocol suite. Courtesy of: The Computer Continuum

25. The Software Architecture of the Network • The Internet Architecture is based on a four-layer protocol. FTP HTTP NV TFTP TCP UDP IP Network#1 Network#2 NetworkN Courtesy of: The Computer Continuum

26. The Software Architecture of the Network • The Internet is referred to as a packet-switching network. • Packet - The Internet chunks information into packets. • Once a file is requested, it is split into packets. • Contains information regarding content, where it came from, where it is supposed to go. • Each packet is assigned a number. • As the packet travels through the Internet from network to network: • Each packet may not travel through the same path through the Internet to its destination. • Each network has its own “packet-limiting” size. • Packets are often “packaged” and “repackaged.” • They are reconstructed in order when they reach the destination. Courtesy of: The Computer Continuum

27. The Software Architecture of the Network • Problem: If someone wants his own WWW site, he must find a home for it. • Solution: • Server - • A dedicated computer that is part of a network. • The hard drive contains files that are “served” to whatever requests them. • Could be data, programs, or home pages for the WWW. • The server normally runs the networking software. Courtesy of: The Computer Continuum

28. The Software Architecture of the Network • Types of nodes important to networks. Hub A device that repeats or broadcasts the network stream of information to individual nodes ( usually personal computers) Switch A device that receives packets from its input link, and then sorts them and transmits them over the proper link that connects to the node addressed. Bridge A link between two networks that have identical rules of communication. Gateway A link between two different networks that have different rules of communication. Router A node that sends network packets in one of many possible directions to get them to their destination. Courtesy of: The Computer Continuum