COMMUNICATIONS, NETWORKS, & SAFEGUARDS The Wired & Wireless World

1. COMMUNICATIONS, NETWORKS, & SAFEGUARDS The Wired & Wireless World 6 Chapter

2. Chapter Topics 6.1 From the Analog to the Digital Age 6.2 Networks 6.3 Wired Communications Media 6.4 Wireless Communications Media 6.5 Cyberthreats, Hackers, & Safeguards

3. Digital convergence is the gradual merger of computing and communications into a new information environment, in which the same information is exchanged among many kinds of equipment, using the language of computers. • At the same time, there has been a convergence of several important industries—computers, telecommunications, consumer electronics, entertainment, mass media— producing new electronic products that perform multiple functions.

4. 6.1 From the Analog to the Digital Age

5. Digital • Computers use digital signals—0s and 1s, off and on. • All the data that a computer processes is a series of 0s and 1s. • Each signal is a bit. • Analog • But most phenomena in life are analog. • Analog signals use wave variations. • Sound, light, and temperature are analog forms. • Traditional TV and radio use analog signals. • Humans’ vision operates in analog mode. But analog data can be converted into digital form. Even though digital data is not as exact as analog data, it is easier to manipulate.

6. For data transmission over telephone lines and cables, modems are needed to convert analog data into digital data that computers can use. • Modem is short for modulate/demodulate. Modems modulate (convert) a computer’s digital data to analog data, transmit it, then demodulate (reconvert) it back to digital data for the receiving computer. • Modems can convert data by modulating either a analog wave’s amplitude or its frequency.

9. Converting Reality to Digital Form: Sampling • Tape recorders, voices, and musical instruments are analog; CDs are digital • To burn a CD, the digital recording equipment must convert from analog to digital • The analog-to-digital converter samples the sound and converts the height of the wave to a number • Samples of the sound wave are taken at regular intervals – about 44,100 times each second • Because the digital samples are played back faster than our ears can react, it sounds to us like a single continuous sound wave

10. 6.2 Networks

11. A network is a system of interconnected computers, telephones, and/or other communications devices that can communicate with one another and share applications and data • Benefits of Networks • Share peripheral devices, such as printers, scanners, disk drives • Share programs and data • Better communications, including email • Centralized communications • Security of information, because of improved backup systems • Access to shared databases

12. Some disadvantages of networks: • Expense: The initial set up cost of a computer network can be high depending on the number of computers to be connected and the number of connecting devices and NICs . • Security Issues: If a computer is on a network, a computer hacker can get unauthorized access by using different tools. • Rapid Spread of Computer Viruses: If any computer system in a network gets affected by computer virus, there is a possible threat of other systems getting affected, too. Viruses get spread on a network easily because of the interconnectivity of workstations. • Dependency on the Main File Server: If the main file server of a computer network breaks down, the entire system can become useless. In case of big networks, the file server is often a powerful computer, which often makes a failure expensive—not to mention causing a service outage for many customers or system users.

13. Main types of networks • A wide area network (WAN) is a communications network that covers a wide geographic area, such as a country or the world. Most long-distance and regional telephone companies are WANs. WANs are used to connect local area networks, so that users and computers in one location can communicate with users and computers in other locations. The best example of a WAN is the Internet. • A metropolitan area network (MAN) is a communications network covering a city or asuburb. Many cellphone systems are MANs, and some cities set up wireless MANs to connect local area networks to the Internet. • Alocal area network (LAN)connects computers and devices in a limited geographic area, such as one office, one building, or a group of buildings close together.LANs are the basis for most office networks, and the organization that runs the LAN owns it. WANs and MANs generally use a common carrier—a telecommunications company that hires itself out to the public to provide communications transmission services—for at least part of its connections. (continued)

16. A home area network uses wired, cable, or wireless connections to link a household’s digital devices—not only multiple computers, printers, and storage devices but also VCRs, DVDs, televisions, fax machines, videogame machines, and home security systems. • A personal area network uses short-range wireless technology to connect an individual’s personal electronics, such as cellphone, MP3 player, notebook PC, and printer. These networks are made possible with such inexpensive, short-range wireless technologies as Bluetooth, ultra wideband, and wireless USB. • A home automation network relies on inexpensive, very short-range, low-power wireless technology to link switches and sensors around the house. Such networks run on inexpensive AA batteries and use wireless remotes, in-wall touch screens, and smartphones, along with special software, to control lights and switches, thermostats and furnaces, smoke alarms and outdoor floodlights, etc.

17. How Networks Are Structured: Two Principal Structures • 1. Client/Server • Consists of clients, which are computers that request data, and servers, which are computers that supply data • File servers act like a network-based shared disk drive • Database servers store data but don’t store programs • Print servers connect one or more printers and schedule and control print jobs • Mail servers manage email

18. How Networks Are Structured: Two Principal Structures (continued) • 2. Peer-to-Peer (P2P) • All computers on the network are “equal” and communicate directly with one another, without relying on servers

20. Intranets, Extranets, & VPNs: use the Internet as their base • Intranets—use infrastructure and standards of the Internet and the web, but for an organization’s internal use only • Extranets—similar to intranets but allows use by selected outside entities, such as suppliers • VPNs—virtual private networks: use a public network (usually the Internet) plus intranets and extranets to connect an organization’s various sites) but on a private basis, via encryption and authentication; regular Internet users do not have access to the VPN’s data and information

21. Network Components — all networks have several things in common: • wired = twisted-pair, coaxial cable, fiber-optic cable • wireless = infrared, microwave, radio, Wi-Fi, satellite • Hosts and Nodes: Client/server network has a host computer, which controls the network; a node is any device attached to the network. • Packets – fixed-length blocks of data for transmission, reassembled after transmission • Protocols—set of conventions, or rules, governing the exchange of data between hardware and/or software components in the network; built into the hardware or software you are using

22. Network linking devices: • Switch—Full-duplex device that connects computers to a network; sends only to intended recipients • Bridge—Interface device that connects same type of networks • Gateway—Interface device that connects dissimilar networks • Router—Device that directs messages among several networks, wired or and/or wireless • Backbone—Main Internet highway that connects all networks in an organization; includes switches, gateways, routers, etc. • NIC—Network interface card; inserted in a slot on the motherboard, enables computer to operate as part of a network • NOS—network operating system; the system software that manages network activity

23. Network topologies: Bus, Ring, Star, Mesh • Bus – all nodes are connected to a single wire or cable • Ring – all nodes are connected in a continuous loop • Star – all nodes are connected through a central host • Mesh – messages sent to the destination can take any possible shortest, easiest route to reach its destination. There must be at least two paths to any individual computer to create a mesh network. (Wireless networks are often implemented as a mesh, and the Internet is a mesh.)

27. Ethernet • Collisions happen when two data packets are going opposite directions on shared media • Ethernet deals with LAN collisions; Ethernetis a LAN technology that can be used with almost any kind of computer and that describes how data can be sent between computers and other networked devices usually in close proximity. • The Ethernet communications protocol is embedded in software and hardware devices intended for building a local area network (LAN), and it is commonly used in star topologies.

28. 6.3 Wired Communications Media

29. Communications media carry signals over a communications path between devices • Twisted-Pair Wire (dial-up connections) • 2 strands of insulated copper wire twisted around each other • Twisting reduces interference (crosstalk) from electrical signals • Data rates are 1 – 128 megabits per second (slow) • Coaxial Cable • Insulated copper wire wrapped in a metal shield and then in an external plastic cover • Used for cable TV and cable Internet electric signals • Carries voice and data up to 200 megabits per second (fast)

30. Communications media (continued) • Fiber-optic cable • Dozens or hundreds of thin strands of glass or plastic that transmit pulses of light, not electricity • Can transmit up to 2 gigabits per second (very fast) • Have lower error rate than twisted-pair or coax • More expensive than twisted-pair or coax • Lighter and more durable than twisted-pair or coax • More difficult to tap into than twisted-pair or coax

31. Wired connections for the home: • Ethernet • Connect to PC’s Ethernet network interface card (NIC) • For several PCs, get a switch to connect them all • 10 or 100 megabits per second • HomePNA • Uses existing telephone wiring and jacks • Requires HomePNA NIC in your PC • Speeds of about 320 megabits per second • Homeplug • Uses existing home electrical lines • Speeds of 200 megabits per second

32. 6.4 Wireless Communications Media

33. Electromagnetic spectrum of radiation is the basis of all telecommunications signals, wired and wireless • Radio-frequency (RF) spectrum is the part of the electromagnetic spectrum that carries most communications signals

34. (continued)

36. Bandwidth: range (band) of frequencies that a transmission medium can carry in a given period of time • Analog bandwidth is expressed in hertz, digital bandwidth usually in bits per second (bps) • Narrowband (voiceband): used for regular telephone communications • Transmission rate 1.5 megabits per second or less • Broadband: For high-speed data and high-quality audio and video; wide band of frequencies • Transmission rate 1.5 megabits per second to 1 gigabit per second or more

37. TC/IP (Ch. 2) is the protocol for getting wired devices connected to the Internet • WAP (wireless application protocol): Wireless handheld devices such as cellphones use the Wireless Application Protocol for connecting wireless users to the Web. Just as the protocol TCP/IP was designed to provide a wired connection to your Internet access provider, WAP is a standard designed to link nearly all mobile devices telecommunications carriers’ wireless networks and content providers.

38. Five Types of Wireless Communications Media • Infrared Transmission • Sends signals using infrared light • Frequencies are too low to see (1-16 megabits per second) • Broadcast Radio • AM/FM, CB, ham, cellphones, police radio • Sends data over long distances using a transmitter and a receiver (up to 2 megabits per second) • Cellular Radio • Form of broadcast radio • Widely used in cellphones and wireless modems • Transmits voice and digital messages

39. Five Types of Wireless Communications Media (continued) • Microwave Radio • Superhigh-frequency radio transmit voice and data at 45 megabits per second • Requires line-of-sight transmitters and receivers • More than ½ of today’s telephones systems use microwave • Communications Satellites • Microwave relay stations in orbit around the earth • Basis for Global Positioning Systems (GPS) • Cover broad service area (continued)

40. Communications Satellites (continued) • Can be placed at different heights: GEO, MEO, LEO • GEO – geostationary earth orbit • 22,300 miles above earth; travel at the same speed as the earth and so appear to us to be stationary • Always above equator • Transmission delay can make conversations difficult • MEO – medium-earth orbit • 5,000 – 10,000 miles up • LEO – low-earth orbit • 200 – 1,000 miles up • Has no signal delay

41. Long-Distance Wireless: One-Way Communication • GPS (Global Positioning System) • 24 to 32 MEO satellites continuously transmitting timed radio signals • Each satellite circles earth twice each day at 11,000 miles up • GPS receivers pick up transmissions from up to 4 satellites and pinpoint the receiver’s location • Accurate within 3 – 50 feet, with a norm of 10 feet accuracy

43. Long-Distance Wireless: One-Way Communication (continued) • One-way Pagers: radio receivers that receive data sent from a special radio transmitter • Radio transmitter sends out signals over the special frequency; pagers are tuned to that frequency • When a particular pager hears its own code, it receives and displays the message Question: Why do airplane rules require you to turn off pagers and cellphones during flight? Answer: Pilots use radar and radio to determine their position and communicate with ground control. Pager and cellphone signals use radio, too, and competing signals can interfere with one another.

44. Long-Distance Wireless: Two-Way Communications (continued) • 1G: First-Generation Cellular Service • Analog cellphones • Designed for voice communication using a system of hexagonal ground-area cells around transmitter-receiver cell towers • Good for voice – less effective for data because of handing off • 2G: Second-Generation Cellular Service • Uses digital signals • First digital voice cellular network

45. Long-Distance Wireless: Two-Way Communications (continued) • 3G: Third-Generation Cellular Service • Broadband technology • Carries data at high speeds: 144 kilobits per second up to 3.1 megabits per second • Accepts e-mail with attachments • Displays color video and still pictures • Plays music

46. Long-Distance Wireless: Two-Way Communications (continued) • 4G: Fourth-Generation Cellular Service • A nationwide 4G network is in development • Will provide improved on-demand high-quality video and audio services

48. Short-Range Wireless: Two-Way Communications • Local Area Networks • Range 100 – 228 feet • Include Wi-Fi (802.11) type networks • Wi-Fi n is the latest and fastest Wi-Fi technology • Personal Area Networks • Range 30 – 32 feet • Use Bluetooth, ultra wideband, and wireless USB • Home Automation networks • Range 100 – 150 feet • Use Insteon, ZigBee, and Z-Wave standards

49. Wi-Fi set-up in a restaurant

50. Wi-Fi b, a, g, & n for local area networks (LANs) • Named for variations on the IEEE 802.11 standard • Data ranges: 11 megabits per second up to 228 feet • Wireless devices must use the same communications standard to communicate. Many products conform to the 802.11a, 802.11b, 802.11g, or 802.11n wireless standards. Increasingly, people are installing Wi-Fi networks in their homes, going online through wireless hot spots at cafes and other establishments, and connecting via free Wi-Fi networks in airports and hotels. • Be sure the Wi-Fi connection is secure against cyberspying. Also, Wi-Fi connections can be made without your knowledge, so disable your Wi-Fi software, instead of leaving it on to auto connect, whenever you’re not using it. This can keep you from unknowingly connecting to a fraudulent network. • Use cellphone security software!