Networking: Computer Connections

1. Networking: Computer Connections Chapter 7

2. Data Communications • Send and receive information over communications lines

3. Distributed Data Processing

4. Network • Uses communication equipment to connect two or more computers and their resources • LAN – shares data and resources among users in close proximity (same floor/building) • WAN – shares data among users who are geographically distant

5. Basic Components • Sending device • Communications link • Receiving device

6. Data Transmissionbandwidth • Digital lines • Sends data as distinct pulses • Need digital line • Analog lines • Sends a continuous electrical signal in the form of a wave • Conversion from digital to analog needed • Telephone lines, coaxial cables, microwave circuits

7. Modemlow bandwidth connection • Modulate • Convert from digital to analog • Demodulate • Convert from analog to digital • Speeds up to 56,000 bps (56K) • (bps: is speed of transferring data (bits per second)

8. Types of Modems • Direct-connect • External • Internal • PCMCIA • Personal Computer Memory Card International Association • Notebook and laptop computers

9. Broad bandwidth connections

10. ISDNIntegrated Services Digital Network • Digital transmission • Speeds of 128,000 bps • Connect and talk at same time • Need • Adapter • Upgraded phone service • Initial costs high • Ongoing monthly fees may be high • Not available in all areas

11. DSLDigital Subscriber Line • Uses conventional telephone lines • No industry standard • Cost • Speed • Phone line shared between computer and voice • Always on • Speed ranges from 1mbps & Up to 10 Mbps • (security problems since its always on)

12. Cable Modem • Coaxial cables • Does not interfere with cable TV reception • Up to 10 million bps • Always on • Shared capacity • Security problem

13. High Capacity Digital Lines • T1 • 1.54 Mbps • T3 • 43 Mbps • Expensive • High-volume traffic

14. Summary of bandwidth connections available for individuals and businesses • Low speed PPP (modem) : • Modem connections: 28,000k - 56,000K • High-speed (broad bandwidth) connection to the Internet • ISDN, Cable Modem, DSL, T1, T2, & T3: • ISDN (Integrated Service Digital Network): Digital transmission over telephone lines. Its speed is up to 128Kbps. Available from Telephone company. • Cable Modem: connects you PC to a local cable TV line and receives data at 1.5-10 Mbps (Millions bits per second). RCN Cables • DSL(Digital subscriber line): Digital transmission of data over telephone line. Available from Telephone company. Speed is about 1- 10 Mbps. • T1: The T-carrier system transmits at 1.43 Mbps. Used by ISP’s • T2: The T-carrier system transmits at 6.3 Mbps. Used by ISP’s • T3: Also used by ISP’s. 44 Mbps

15. Network Cable • Twisted pair • Coaxial cable • Fiber optic cable • Wireless • No cables • Easy to set up and reconfigure • Slower transmission rates • Small distance between nodes • Uses infrared or low-power radio wave transmissions

16. Twisted PairWire Pair • Inexpensive • Susceptible to electrical interference (noise) • Telephone systems • Physical characteristics • Twisted around each other to reduce electrical interference • Plastic sheath • Shielded twisted pair • Metallic protective sheath • Reduces noise • Increases speed

17. Coaxial Cable • Higher bandwidth • Less susceptible to noise • Used in cable TC systems • Physical characteristics • Center conductor wire • Surrounded by a layer of insulation

18. Fiber Optics • Transmits using light • Higher bandwidth • Less expensive • Immune to electrical noise • More secure – easy to notice an attempt to intercept signal • Physical characterizes • Glass or plastic fibers • Very thin (thinner than human hair) • Material is light

19. Microwave Transmission • Line-of-site • High speed • Cost effective • Easy to implement • Weather can cause interference • Physical characteristics • Data signals sent through atmosphere

20. Satellite Transmission • Microwave transmission with a satellite acting as a relay • Long distance • Components • Earth stations – send and receive signals • Transponder – satellite • Receives signal from earth station (uplink) • Amplifies signal • Changes the frequency • Retransmits the data to a receiving earth station (downlink)

21. Satellite Transmission

22. Combination Example – East and West coast: • Request made • Twisted pair in the phone lines on the East Coast • Microwave and satellite transmission across the country • Twisted pair in the phone lines on the West coast • Data transferred • Twisted pair in the phone lines on the West Coast • Microwave and satellite transmission across the country • Twisted pair in the phone lines on the East coast

23. Network TopologyLAN & WAN • Physical layout • Star • Ring • Bus • Node– any device connected to the network • Server • Computer • Printer • Other peripheral

24. LAN (Local Area Network) • Connections over short distances through communications media • Same floor or building • Components • PCs • Network cable

25. WANWide Area Network • Link computers in geographically distant locations