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Chapter 6

Chapter 6. Telecommunications and Networks. Presentation Overview. The Evolution of Networking Data Transmission Characteristics Communications Media Network Classifications Network Topologies Network Hardware Network Software Communications Software and Protocols.

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Chapter 6

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  1. Chapter 6 Telecommunications and Networks

  2. Presentation Overview • The Evolution of Networking • Data Transmission Characteristics • Communications Media • Network Classifications • Network Topologies • Network Hardware • Network Software • Communications Software and Protocols

  3. Telecommunications, combined use of computer hardware and communications software for sending and receiving information over communications media, enables computer users throughout the world to communicate. The Evolution of Networking

  4. Data Transmission Characteristics What are the characteristics of transmitted data? • Bandwidth – number of bits that can be transferred per second over a given medium • Analog signals – continuous waves transmitted over a medium at a certain frequency range • Digital signals send data in the form of bits

  5. Bandwidth number of bits that can be transmitted per second terms for measuring bandwidth Data Transmission Characteristics

  6. Analog and Digital Transmission Modulate – sending modem changes digital signal into analog signal Demodulate – receiving modem changes analog signal back into digital signal Data Transmission Characteristics

  7. Translating digital signals to analog signals Data Transmission Characteristics

  8. Internal modem – electronic board plugged into a slot on a computer’s motherboard Data Transmission Characteristics External modem – stand-alone device connected by cable to a computer

  9. Parallel and Serial Transmission Serial transmission sends 1 byte plus the parity bit one bit after another in a continuous line. Parallel transmission sends 8 bits plus a parity bit at the same time over 9 separate paths. Data Transmission Characteristics

  10. Coaxial cable is an insulated center wire grounded by a shield of braided wire. Communications Media

  11. Twisted-pair cable is two parallel copper wires, individually wrapped in plastic and bound by another plastic casing. Communications Media

  12. Fiber-optic cable transmits beams of light through a glass or plastic core. Communications Media

  13. Wired Communications Media Integrated Services Digital Network (ISDN) Lines are used to dial into the Internet and receive information at high speeds. Digital Subscriber Lines (DSL) use existing phone lines and new switched connections to get faster speeds than traditional phone access. T Linesare digital, high-speed, long-distance lines capable of carrying signals across the line. Communications Media

  14. Microwave systems transmit data through the atmosphere from one microwave station to another. Communications Media

  15. Communications satellite is a solar-powered, electronic device with specialized radios (transponders) for receiving signals from ground transmission stations. A satellite receives transmitted signals, amplifies them, and retransmits them to other ground locations. Communications Media

  16. Infrared technology allows data as infrared light waves to be transmitted from a special port in a computer to an infrared sensor in a printer. Communications Media

  17. Wireless Communications Media Bluetooth technology offers short-range connectivity with other Bluetooth devices. Devices form a small, temporary network that can transmit voice and data. Communications Media

  18. Wi-Fi-enabled devices use a broadband Internet connection through a wireless access point. Communications Media home

  19. Signals sent by cell phones are transmitted and received from cell to cell until they reach their destination. Communications Media

  20. Network Classifications Networking paths allow networkedclient computers to send information to a server, which relays information back to the computer or to another on the network. Fax machines and printers are shared resources. The file server accesses a shared hard disk.

  21. Network Classifications Local area network (LAN)is a private network using a file server that houses all networkresources.

  22. Network Classifications Wide area network (WAN)spans a large geographical area connecting two or more LANs.

  23. Network Classifications An intranetis a network within an organization to serve internal users.

  24. A network interface card (NIC) is used for wired connections in a desktop PC. A wireless NIC allows notebook computers to use Wi-Fi hotspots. Network Hardware Network Interface Card (NIC) connects each client computer to a network

  25. Network Classifications In peer-to-peer architecture, computers act as both client and server.

  26. Network Topologies Bus Topology • all computers linked to a single line of cable (bus) • all communications travel length of bus

  27. Network Topologies Ring Topology has no hub, and each computer is connected to two other computers in a circular path.

  28. Network Topologies Star Topology links multiple computers and devices to a central hub in a configuration resembling a star.

  29. Network Hardware Hubs, Switches, Routers devices that links computers in a network

  30. Network Hardware A gatewayis a combination of hardware and software that allows dissimilar networks to communicate. A bridge is a combination of hardware and software that enables devices on similar networks to communicate

  31. Network Software Network Operating Systems (NOS) • controls flow of messages from client computers and provides services such as file access and printing • systems such as Linux and Mac OS have networking functions built in • Windows systems include Novell’s Netware or Windows Server software to enhance the basic operating system

  32. Communications Software Communication software programs can be used to • access and use services of an Internet service provider for e-mail and Web browsers • send and receive information to and from computers through LAN and WAN networks • send and receive faxes

  33. Protocols What are protocols? • Protocols are rules and procedures for exchanging information among computers on a network. • Computers involved must have the same settings and follow the same standards.

  34. Communications Software and Protocols With simplex data transmission, data flows only one way. With half-duplex data transmission, data flows in both directions but only in one direction at a time. With full-duplex data transmission, data flows in both directions at the same time.

  35. Communications Software and Protocols Synchronous Transmission Protocols blocks of bytes are wrapped in a start and stop byte called a synch byte.

  36. Communications Software and Protocols Asynchronous Transmission Protocols each byte of data is surrounded by control bits: • start bit signals the beginning of a character • stop bit signals the end • parity bitchecks for errors

  37. Communications Software and Protocols Local Area Network (LAN) Protocols • Ethernet protocol specifies how the network is set up, how devices communicate, how problems are identified and corrected, and how components are connected. • Token ringprotocol sends an electronic signal (token) around the ring quickly.

  38. sending receiving user user protocol stack layer physical media physical media Communications Software and Protocols TCP/IPTransfer Control Protocol / Internet Protocol

  39. Communications Software and Protocols Circuit Switching / Packet Switching • Circuit switching • Networks create an end-to-end circuit between the sending and receiving computers. • Electronic switches establish and maintain the connection. Packet switching • Outgoing messages are divided into fixed-size data units called packets. • Packets are numbered and addressed to the receiving computer. • Routers examine the packets and send them to their destination.

  40. Packet Switching

  41. Communications Software and Protocols Internet and Web Protocols • Hypertext Transfer Protocol (HTTP) is used on the World Wide Web. • sends small blocks (packets) of data along the Internet to their destinations • File Transfer Protocol (FTP)transmits and receives large files over the Internet.

  42. Communications Software and Protocols Electronic Mail Protocols • Post Office Protocol (POP) server allows the recipient to retrieve the message. • Simple Mail Transfer Protocol (SMTP) determines how a message will be routed through the Internet and then sends the message.

  43. Communications Software and Protocols Variations of the 802.11 protocol 802.11 n 2007 600 Mbps

  44. On the Horizon Based on the information presented in this chapter and your own experience, what do you think is on the horizon?

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