Chapter 7: Computer Networks

1. Chapter 7: Computer Networks

2. Learning Objectives Define a network and its purpose. Describe several uses for communications technology. Understand the various topologies and architectures a computer network might use. Explain the difference between a LAN, a WAN, and a PAN, and between an intranet, an extranet, and a VPN.

3. Learning Objectives Understand characteristics about data and how it travels over a network. Name specific types of wired and wireless transmission media and explain how they transmit data. Identify different protocols that can be used to connect the devices on a network. List several types of networking hardware and explain the purpose of each.

4. Overview This chapter covers: Networking concepts and terminology Common networking and communications applications Technical issues related to networks, including the major types of networks, how data is transmitted over a network, and types of transmission media involved Explanation of the various ways networked devices communicate with one another Various types of hardware used in conjunction with a computer network

5. What Is a Network? Network: A connected system of objects or people Computer network: A collection of computers and other hardware devices connected together so that users can share hardware, software, and data, as well as electronically communicate with each other Internet: Largest computer network in the world Types of networks Business networks Phone networks Home and multimedia networks

6. Networking and Communications Applications Mobile phones (wireless phones) Cellular (cell) phones Must be within range of cell tower to function Satellite phones Used where cell service isn’t available Dual-mode phones Allows users to make telephone calls on more than one network Cellular / Wi-Fi dual mode phone are most popular

7. Networking and Communications Applications

8. Networking and Communications Applications Paging Sending short numeric or text messages to a person’s pager Most often used for onsite paging applications Messaging Two-way paging Most often takes place today via a mobile phone

9. Networking and Communications Applications Global positioning system (GPS): Uses satellites and a receiver to determine the exact geographic location of the receiver Commonly found in cars today Available as handheld units Used by the military, hikers, travelers, and others who need to know their precise location

10. Networking and Communications Applications Monitoring systems: Monitor status or location of individuals, vehicles, assets, etc. RFID-based systems GPS-based monitoring systems Electronic medical monitors and other types of home health monitoring Digital entertainment High-definition television/radio: HDTV is replacing analog broadcasts Satellite radio: Delivers digital radio content to satellite receivers Multimedia networking and digital data distribution

11. Networking and Communications Applications Videoconferencing: Use of communications technology for real-time, face-to-face meetings between individuals located in different places Technology continues to improve and mimic real-life meeting environments Telepresence videoconferenceing Online conferencing (via the Internet) Video phone calls

12. Networking and Communications Applications • Collaborative computing (workgroup computing): Using a computer and communications technology to work together on documents and other project • Tools include Microsoft Office markup tools and collaboration software • Telecommuting: Individuals work at home and communicate with their place of business and clients via communications technologies • Possible because of the Internet and other communications technologies

13. Networking and Communications Applications Telemedicine: Use of communications technology to provide medical information and services Remote monitoring and consultations Remote diagnosis Telesurgery

14. Types of Networks Topology: How the devices in the network (called nodes) are arranged Star networks: All devices connect to a central device or hub) Bus networks: All devices connect to a central cable Ring networks: Devices connect to one another in a ring Mesh networks: Multiple connections between devices Some networks use a combination of topologies

15. Network Topologies

16. Types of Networks Architecture : The way networks are designed to communicate Client-server networks Client: PC or other device on the network that requests and utilizes network resources Server: Computer dedicated to processing client requests

17. Types of Networks Peer-to-peer networks: All computers at the same level) Internet peer-to-peer (P2P) computing: Performed via the Internet

18. Types of Networks Local area network (LAN): Small geographical area (office, campus, etc.) Wide area network (WAN): Large geographical area (Internet) Metropolitan area network (MAN): Serves a metropolitan area Municipal Wi-Fi projects Personal area network (PAN): Connects personal devices for one individual, such as his or her portable PC, mobile phone, and portable printer

19. Types of Networks Wireless sensor networks (WSNs): Contain sensors (devices that respond to a stimulus and generate an electrical signal that can be measured or interpreted) Intranet: Private network set up by an organization for use by its employees Extranet: Intranet that is at least partially accessible to authorized outsiders Virtual private network (VPN): Secure path over the Internet that provide authorized users a secure means of accessing a private network via the Internet

20. Data Transmission Characteristics Analog vs. digital (waves vs. discrete) Bandwidth: The amount of data that can be sent at during a given period of time Measured in bits per second (bps) Serial vs. parallel transmission Serial = 1 bit Parallel = atleast 1 byte ata time

21. Data Transmission Characteristics Transmission timing Synchronous transmission (at regular, specified intervals) Asynchronous transmission (sent when ready) Isochronous transmission (sent at the same time as other, related, data)

22. Data Transmission Characteristics Transmission directions Simplex transmission (one way only) Half-duplex transmission (one way at a time) Full-duplex transmission (both ways at the same time)

23. Data Transmission Characteristics Type of connections Circuit-switched: Dedicated path over a network is established and all data follows that path Packet-switched: Messages are separated into small units called packets and travel along the network separately Used to send data over the Internet Broadcast: Data is sent out to all other nodes on the network Primarily used with LANs

24. Type of Connections

25. Data Transmission Characteristics Wired connections: The PC is physically cabled to the network Common in schools, business, and government facilities Wireless connections: Typically use radio waves to send data through the air Rapidly becoming more popular in homes and businesses Wireless hotspots are commonly available in public locations

26. Wired Network Transmission Media Twisted-pair cable Pairs of wires twisted together Used for telephone and network connections Coaxial cable Thick center wire Used for computer networks, short-run telephone transmissions, cable television delivery Fiber-optic cable Glass or fiber strands through which light can pass Used for high-speed communications

27. Wired Network Transmission Media

28. Wireless Network Transmission Media Use radio signals Short-range (such as Bluetooth) can connect a wireless keyboard or mouse to a PC Medium-range (such as Wi-Fi) are used for wireless LANs and to connect portable PC users to the Internet at public hotspots Longer-range (WiMAX) can be used to provide Internet access to wide geographic areas Radio frequencies are assigned by the FCC and are measured in hertz (Hz) The electromagnetic spectrum is the range of common electromagnetic radiation (energy) that travels in waves

29. Wireless Network Transmission Media

30. Cellular Radio Transmissions Use cellular towers within cells Calls are transferred from cell tower to cell tower as the individual moves Different transmission frequencies are used to avoid interference and allow multiple conversations to take place via a single tower at one time Widely used, but cell service not available everywhere Cell phone technology is referred to in generations Today’s phones are third-generation 4G service is beginning to become available

31. Cellular Radio Transmissions

32. Microwave and Satellite Transmissions Microwaves: High-frequency radio signals Sent and received using microwave stations or satellites Microwave stations are earth-based and can transmit signals to each other over distances of about 30 miles Signals are line of sight, so stations are usually built on tall buildings, towers, mountaintops Communication satellites: Space-based devices launched into orbit to send and receive microwave signals from earth Traditional satellites use geosynchronous orbit Low earth orbit (LEO) satellites were developed to combat delay Medium earth orbit (MEO) satellites are most often used for GPS systems Can send large quantities of data at high speed over long distances

33. Microwave and Satellite Transmissions

34. Infrared (IR) Transmissions Sends data as infrared light Like an infrared television remote, IR requires line of sight Because of this limitation, many formerly IR devices (wireless mice, keyboards) now use RF technology IR is still sometimes used to beam data between handheld PCs or gaming systems, or send documents from portable PCs to printers

35. Networking Standards andCommunications Protocols Standards: A set of criteria or requirements considered to be the approved model for something Networking standards: Address how networked computers communicate and connect Communications protocol: An agreed-upon standard for transmitting data between two devices on a network In networking, standards and protocols specify how: Devices physically connect to a network Data is packaged for transmission Receiving devices acknowledge signals Errors are handled Also ensure products can work together

36. Ethernet Ethernet: Most widely used communications protocol for wired LANs Typically used a bus or star topology and twisted-pair, coaxial, or fiber-optic cables Original(10Base-T)Ethernet networks run at 10 Mbps Newer 100 Mbps, 1Gbps, and 10 Gbps versions are common 100 Gbps is in development Power over Ethernet: Allows electrical power to be sent along with data on an Ethernet network Most often used by businesses

37. Ethernet

38. TCP/IP and Wireless Application Protocol (WAP) TCP/IP (Transmission Control Protocol/Internet Protocol): Used for transferring data over the Internet Uses packet switching TCP/IP support built into virtually all Oss IPv4 uses 32-bit addresses IPv6 uses 128-bit addresses and expected to eventually replace IPv4 Wireless Application Protocol (WAP):A standard for delivering Internet content to mobile devices Microbrowser: Used to access WAP content

39. TCP/IP

40. Wi-Fi (802.11) Wi-Fi (Wireless Fidelity): A family of wireless networking standards using the IEEE standard 802.11 Also called wireless Ethernet Current standard for wireless networks in home and office Designed for medium-range transmission Wi-Fi hardware built into most notebook PCs and many consumer devices today Hotspots rapidly multiplying Speed and distance of Wi-Fi networks depends on Standard and hardware being used Number of solid objects between the access point and the PC or wireless device Possible interference

41. Wi-Fi (802.11)

42. Wi-Fi (802.11) Various standards Current standard is 802.11g Emerging standard is 802.11n

43. WiMAX, Mobile WiMAX, and Mobile-Fi WiMAX (Worldwide Interoperability for Microwave Access or 802.16): Fairly new wireless standard for longer range wireless networking connections Designed to deliver broadband to homes, businesses, other fixed locations Mobile WiMAX is the mobile version of the standard 4G mobile phones may be WiMAX-based Mobile-Fi (802.20): Currently in development for providing high-speed mobile Internet access in cars, trains, and other moving vehicles

44. WiMAX, Mobile WiMAX, and Mobile-Fi

45. Short-Range Wireless Networking Bluetooth: Very short range (less than 10 feet) For communication between computers or mobile devices and peripheral devices Bluetooth devices are automatically networked with each other when they are in range (piconets) Ultra Wideband (UWB or WiMedia): Originally developed by the military for locating tanks, enemies, hidden objects Designed for wireless multimedia networking Range of 100 feet or less Speed depends on distance between devices New Bluetooth standards will use UWB to speed up transfers of large amounts of data Wireless USB is UWB-based

46. Bluetooth

47. Short-Range Wireless Networking Wireless HD (WiHD): In development, designed for networking home electronics devices ZigBee: Emerging, designed for inexpensive, simple short-range networking like sensor networks Intended for application that require low data transfer rates and several years of battery life Can accommodate more than 65,000 devices on a single network

48. Phoneline and Powerline Phoneline (HomePNA): Allows computers to be networked through regular phone lines and jacks Geared for quick and easy networking HomePNA 3.0 is fast (320 Mbps) and designed for both computers and multimedia networking Powerline: Allows computers to be networked over power lines and conventional outlets Also designed for quick and easy networks HomePlug AV is fast (200 Mbps) and designed for both computers and multimedia networking Broadband over power lines (BPL): An emerging technology that allows Internet data to be sent over existing power-pole infrastructure

49. Cellular Standards Second-generation wireless standards GSM (Global System for Mobile communications) CDMA (Code Division Multiple Access) Third-generation standards GPRS (General Packet Radio Service) EDGE (Enhanced Data Rates for GSM Evolution) UMTS (Universal Mobile Telecommunications System) HSDPA (High Speed Downlink Packet Access)’ EV-DO (Evolution Data Optimized) SMS (Short Message Service) Fourth generation standards are under development Some are WiMAX-based

50. Networking Hardware Network adapter: Used to connect a PC to a network or the Internet Also called network interface card (NIC) when in the form of an expansion card Available in a variety of formats PCI and PCIe USB PC Card and ExpressCard Adapter must match the type of network being used (Ethernet, Wi-Fi, Bluetooth, etc.) Are often built into portable computers