CSCI 1200 / ASSC 1000

1. CSCI 1200 / ASSC 1000 Chapter 8

2. Telecommunications • long distance, electronic communications. • protocol : rules.

3. Network • two or more computers linked together. • why? • share hardware, software & data. • connect people, allowing collaboration.

4. Keep the Network Running • network administrator (person). • network management software. • Network Operating System - NOS

5. Network Operating System • functions for connecting computers & devices to a LAN. • must deal with multiple computers & coordinate things throughout the network. • today many operating systems have networking functions built in.

6. Intranet • open standard protocols instead of a proprietary operating system. • same technology as the Internet, but owned by an organization or individual.

7. Important Terms • nodes – any point on a network (often a computer). • servers - the computers & devices that allocate resources for the network. • backbone - key connection, very high speed, heavy traffic.

8. Important Terms Protocol : In the case of a network, a set of agreed upon rules & signals defining how the computers and devices on the network will communicate.

9. Important Terms • Bridges & Gateways - connect networks, may translate if the networks use different protocols or operating systems, may also handle security (like firewalls). • Router - forwards network traffic, sending it to bridges & gateways. • Switches & Hubs – forwards traffic between network nodes

10. Type of Networks • LAN – Local Area Network • physically close, usually the same building. • may use cables or be wireless. • wireless is slower, but convenient and less invasive. • MAN - Metropolitan Area Network • city sized network. • typically links several LANs.

11. Type of Networks WAN – Wide Area Network • geographically large. • each node is a site. • telephone lines, microwave towers, satellite links make WANs possible. • corporate & government.

12. Special Networks GPS – Global Positioning System • network of 24 satellites. • 4 above horizon at any time. • 3 to calculate position, may use up to 6. • land beacons may augment the network. • radio transmitters & atomic clocks, time for the signal to travel from the satellite to you. • hand held devices, vehicle navigation, mobile phones, outdoor enthusiasts. • more accurate for the military.

13. Special Networks Financial Networks : • money represented digitally. • banking & financial industry operate on a global scale. • access your bank account from almost any country.

14. Building a Network Connection Technology : • Direct Connection – dedicated physical link. • Remote Connection – phone lines, cable lines, satellites.

15. Building a Network Traffic Issues : • devoted connection to each node. • or many computers must share the line.

16. Building A Network Network Interface Card • special hardware. • inserted into a slot. • adds a network port for a direct connection. • controls data flow between network & computer’s memory. • boosts the signal on it’s way out. • Ethernet port is often built in now.

17. Bandwidth • amount of data that can be transmitted in a fixed amount of time. • bps, kbps, mbps. • to increase speed: • widen the pipe. • increase the speed of traffic through the pipe. • better protocols.

18. Connections Modem • longer distances. • connect to a telephone line. • internal / external. • phone network – designed for sound. • convert stream of bits to a continuous sound wave – digital to analogue. • generally slower than a direct connection. • speed measured in bps – 56k.

19. Connections Broadband Technology • single medium (wire) can carry several channels at once. • DSL – phone lines • Cable Modems – cable television lines • Wireless – radio or infrared waves • Satellite – satellites & dishes

20. Connections Fiber Optic • use light instead of electricity. • replace 10,000 copper telephone lines. • 500 million bps – half a gigabit per second. • “last mile”

21. Connections Wireless : • may use a radio or infrared transmitter • mobility over speed Infrared : • line of sight is needed. • short distances. • sunlight

22. Connections Wi-Fi (wireless fidelity) • radio based LAN protocol. • describes any type of 802.11 network. • base station, devices may be a distance of about 150 feet.

23. Connections Bluetooth • short-range radio links – up to 30 feet. • lower energy than Wi-Fi - battery operated devices. • mobile computers, mobile phones, digital cameras, other portable devices. • not competing with Wi-Fi, replace cables needed to plug stuff in.

24. Connections 3G • next generation of mobile communications technology. • other countries more fully utilize mobile phones. • increased bandwidth, up to 384 kbps when a device is stationary or moving at pedestrian speed, 128 kbps in a car, and 2 mbps stationary. • video, multimedia support.

25. Approaches to Networking Client Server Model • server fulfils client requests • high speed, high capacity computer is the server • hierarchical structure, server is essential

26. Approaches to Networking Peer 2 Peer Model • any computer can be a client or a server. • often used on smaller networks (but not necessarily, e.g. music sharing). • Windows & MacOS allow for P2P networking.

27. Internet • global network of networks. • TCP / IP communication standard. • to communicate, networks must speak the same language.

28. Internet Motivation • Researchers : share computing resources, very few computers, expensive. • Military : cold war, wanted a communication network.

29. Military Needs • assume unreliability. • decentralized : all connected computers are equal. • most work when lines are broken, and nodes are down.

30. Network Must • connect important government & research computers. • resist point-of-failure attacks : continue to operate even if a city on the network was destroyed. • be fault-tolerant : continue to operate even if something went wrong within the network – e.g., a computer crashed, or a transmission line was broken.

31. Solution • designed to be a decentralized network of computers that could adapt the flow of traffic and to changes in the state of the overall system. • the way that information travels on the Internet is similar to the way that traffic moves on an interconnected system of roads and highways.