Connecting with Computer Science, 2e Chapter 4 NetworksConnecting with Computer Science, 2e 2 Objectives • In this chapter you will: – Learn how computers are connected – Become familiar with different types of transmission media – Learn the differences between guided and unguided media – Learn how protocols enable networking – Learn about the ISO OSI reference model – Understand the differences between network types – Learn about local area networks (LANs)Objectives (cont’d.) • In this chapter you will (cont’d.): – Learn about wide area networks (WANs) – Learn about wireless local area networks (WLANs) – Learn about network communication devices – Learn how WANs use switched networks to communicate – Learn how devices can share a communication medium – Learn about DSL, cable modems, and satellite communications Connecting with Computer Science, 2e 3Why You Need to Know About... Networks • Networks – Connect computers together – Allows sharing of resources – Used in government research centers, universities, large corporations, and home computing – Integral part of computing for homes and enterprises – Include the Internet • Integrated into personal computers • Computing professional – Incorporates network technology into everything Connecting with Computer Science, 2e 4Connecting Computers • Linking computers through system bus is impractical – PCI bus has 98 wires • Requires a very thick cable – Connection problem solved with technology – Connecting requires a medium (e.g., wire) • Carries electric signal and a communications protocol to manage processes Connecting with Computer Science, 2e 5Connecting with Computer Science, 2e 6 Transmission Medium • Transmission medium – Material conducting electrical and/or electromagnetic signals – Most popular: copper • Rating transmission media – Bandwidth: medium speed measured in bits/second – Signal-to-noise ratio: 10 log10 (signal/noise) – Bit error rate: ratio of incorrect bits to total number of bits in unit time – Attenuation: signal weakening over distanceConnecting with Computer Science, 2e 7 Transmission Medium (cont’d.) • Two general transmission media types – Guided • Physical media – Copper wire: form of twisted pair or coaxial cable – Fiber-optic: uses glass and light to transmit data – Unguided • Air and space carry radio frequency (RF) or infrared (IR) light signalsConnecting with Computer Science, 2e 8 Figure 4-1, Coaxial, twisted pair, and fiber-optic cable are guided media Transmission Medium (cont’d.)Connecting with Computer Science, 2e 9 Copper Wire: Coaxial and Twisted Pair • Two wires used to transmit data: signal and ground • Coaxial cable (coax) – Copper surrounded by metal shield to reduce noise – Support bandwidths up to 600 MHz • 10BaseT • Twisted pair – Replacing copper – Twists dampens effects of inductance – All copper wiring is subject to impedance • Attenuation: reduction in signal – Two types: shielded and unshielded (UTP)Connecting with Computer Science, 2e 10 Table 4-1, EIA/TIA twisted pair cable categories Copper Wire: Coaxial and Twisted Pair (cont’d.)Copper Wire: Coaxial and Twisted Pair (cont’d.) • Twisted pair (cont’d.) – Unshielded twisted pair (UTP) • More popular than shielded twisted pair (STP) – Category 5 (Cat 5) • Most common twisted pair cable • Maximum frequency: 100 MHz • Good for business and home use • Computer industry has turned to optical media – Provides faster data transmission Connecting with Computer Science, 2e 11Fiber-Optic Cable • Glass fibers guide light pulses along a cable – Thin strand of nearly pure glass • Surrounded by reflective material and a tough outer coating • Transmission speeds much higher than with copper – Fiber-optic cables are much less susceptible to attenuation and inductance – Principle of inductance does not apply – Bandwidths hundreds of times faster than copper • Economies of scale bringing price down Connecting with Computer Science, 2e 12Unguided Media: Wireless Technologies • Benefits of wireless technology – Eliminates cables and cabling costs – Provides device mobility • Basis of wireless technology: radio transmission – Examples: cell phones, microwave ovens, etc. – Electronic signal is amplified • Radiated from an antenna as electromagnetic waves • Receiving antenna converts back to electronic signal • Electromagnetic waves – Transmitted at many different frequencies Connecting with Computer Science, 2e 13Connecting with Computer Science, 2e 14 Table 4-2, Wireless technologies Unguided Media: Wireless Technologies (cont’d.)Connecting with Computer Science, 2e 15 Figure 4-2, Wireless technologies Unguided Media: Wireless Technologies (cont’d.)Unguided Media: Wireless Technologies (cont’d.) • Difference between low-pitched sound and a high-pitched sound – Frequency of the sound waves, or vibrations • Uses same technology as car radio and cell phone • Industry standards (based on 2.4 GHz range) – IEEE 802.11 series: most common – Bluetooth specification • Short-range RF links between mobile computers, mobile phones, digital cameras, other portable devices • Maximum distance between devices: three inches to 328 feet Connecting with Computer Science, 2e 16Light Transmission • Infrared light used over short distances • Uses transmission media of air – Requires clear line of sight between devices • Used in PDAs, cell phones, notebook computers, wireless keyboards, and mice • Pulses of infrared light represent 1s and 0s of binary transmission – Speeds up to 4 Mbps Connecting with Computer Science, 2e 17Connecting with Computer Science, 2e 18 Protocols • Set of rules facilitating communication – Example: classroom questioning • Often represented with a timing diagram • Transmission protocol – Provides for an orderly flow of information – HTTP, TCP/IP, FTP • Transmission Control Protocol (TCP) – Allows two computers to establish a communication connection, transfer data, and terminate the
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