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Lecture 5: What is Computer Communications?

Learn about computer communications, networks, local area networks (LAN), nodes, network operating systems, servers and clients, peer-to-peer networking, network topologies, intranets, extranets, firewalls, home networks, intelligent home networks, communications software, and dial-up lines.

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Lecture 5: What is Computer Communications?

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  1. Lecture 5Communications and Networks

  2. What is computer communications? A process in which one computer transfers data, instructions, and information to another computer(s) Communications b f a c c a a e d a

  3. Voice mail Fax E-mail Chatroom Instant Message FTP Newsgroup Telephony Videoconference Groupware Global Positioning System (GPS) Uses of Communications Technologies

  4. What is a network? A collection of computers and devices connected by communications channels Facilitates communications among users Allows users to share resources Networks share data and information facilitate communications share hardware share software

  5. What is a local area network (LAN)? Network that connects computers and devices in a limited geographical area. Often uses Ethernet protocol Networks

  6. What is a node ? Each computer or device on a network Networks often the nodes are connected to the LAN via cables a wireless LAN (WLAN) is a LAN that uses no physical wires node node node node node

  7. What is a network operating system? The system software that organizes and coordinates the activities on LAN Also called a network OS or NOS Networks Administration Adding, deleting, and organizing users and performing maintenance tasks File management Locating and transferring files Printer management Prioritizing print jobs and reports sent to specific printers on the network Security Monitoring and, when necessary, restricting access to network resources

  8. What are servers and clients? Server Controls access to the hardware and software on the network Provides a centralized storage are for programs Dedicated servers perform a specific task Clients Other computers on the network Rely on the server for resources Networks file server stores and manages files print server manages printers and print jobs database server stores and provides access to a database network servermanages network traffic

  9. What is an Internet use of peer-to-peer (P2P)? An Internet network that enables users with the same networking software to connect to each other’s hard disks and exchange files directly Napster and Gnutella are two examples of P2P Networks

  10. What is a network topology? The configuration, or physical arrangement, of the devices in a communications network Networks usually use combinations of three topologies Networks bus ring star

  11. What is a bus network? Consists of a single central cable, to which all computers and other devices connect The bus is the physical cable The bus is also called the backbone Inexpensive and easy to install Networks personal computer personal computer personal computer personal computer personal computer

  12. What is a ring network? A cable forms a closed ring, or loop, with all computers and devices arranged along the ring Data travels from device to device around the entire ring Networks

  13. What is a star network? All of the devices connect to a central computer/hub All data that transfers from one computer to another passes through the hub Networks personal computer personal computer personal computer host computer personal computer printer file server

  14. An internal network that uses Internet technologies Generally make company information accessible to employees and facilitate working in groups Typically also includes a connection to the Internet What is an intranet? Networks has a Web server uses TCP/IP technologies accessible via a Web browser supports multimedia Web pages coded in HTML users can post and update information on the intranet by creating and posting a Web page

  15. What is an extranet? Allows customers or suppliers to access part of a company’s intranet Networks

  16. What is a firewall? Hardware and/or software that restricts access to data and information on a network Networks printer personal computer corporate network personal computer personal computer Internet firewall personal computer personal computer personal computer personal computer

  17. What is a home network? Multiple computers connected together in a home or home office All computers in the house can connect to the Internet at the same time Access files and programs on the other computers in the home Share peripherals Networks

  18. What is an intelligent home network? Extends the basic home network to include features such as lighting control, thermostat adjustment, and a security system Networks

  19. What is communications software? Consists of programs that help you establish a connection to another computer or network Manages the transmission of data, instructions, and information Communications Software

  20. What is a dial-up line? A temporary connection that uses one or more analog telephone lines for communications A modem at the sending end dials the telephone number of a modem at the receiving end The Telephone Network Advantages Costs no more than making a regular call Computers at any two locations can establish a connection using modems and the telephone network Disadvantage Cannot control the quality of the connection because the telephone company’s switching office randomly selects the line

  21. What is a dedicated line? A connection that always is established between two communications devices The quality and consistency of the connection is better because dedicated lines provide a consistent connection The Telephone Network Can be analog or digital Digital lines transfer data and information at faster rates than analog lines

  22. What is transfer rate? The speed with which a line carries data and information The faster the transfer rate the faster you can send and receive data and information Usually are expressed as bits per second (bps) The Telephone Network bits per second (bps) kilobits per second (Kbps) megabits per second (Mbps) gigabits per second (Gbps)

  23. What are popular types of digital dedicated lines? ISDN DSL T-carrier CATV ATM The Telephone Network

  24. What is a communications device? Any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device Sometimes the device must convert the data, instructions, and information from analog to digital signals or vice versa Communications Devices cable modems dial-up modems network interface cards ISDN and DSL modems

  25. What is a modem? A communications device that converts a computer's digital signals to analog signals before they are transmitted over standard telephone lines Sometimes called a dial-up modem Communications Devices mo + dem demodulate To convert an analog signal into a digital signal modulate To change into an analog signal

  26. What is a digital modem? One that sends and receives data and information to and from a digital telephone line such as ISDN or DSL Communications Devices ISDN modem Also called an ISDN adapter Sends and receives digital data to an ISDN line DSL modem Sends and receives digital data to a DSL line

  27. What is a cable modem? A modem that sends and receives data over the cable television (CATV) network Currently much faster than a dial-up modem or ISDN Usually attaches to a USB port or a port on a network interface card Communications Devices

  28. What is a network interface card (NIC)? A card you insert into an expansion slot of a personal computer or other device, enabling the device to connect to a network Communications Devices NIC for desktop computer NIC for notebook computer

  29. What is a BUS? The communications path between two devices Communications Channel

  30. What is twisted-pair cable? Consists of one or more twisted pair wires bundled together Each twisted pairwire consists of two separate insulated copper wires Twisted together to reduce noise Noise is an electrical disturbance that can degrade communications Physical Transmission Media twisted pair cable twisted pair cable twisted pair wire

  31. What is coaxial cable? Consists of a single copper wire surrounded by at least three layers Often called coax Often used for cable television wiring Physical Transmission Media coaxial cable woven or braided wire copper wire plastic outer coating insulating material

  32. What is fiber-optic cable? Contains a core of dozens or hundreds of thin strands of glass or plastic Uses light to transmit signals Each strand is called an optical fiber Thin as a human hair Physical Transmission Media optical fiber core cable contains many optical fibers glass cladding outer covering jacket protective coating fiber-optic cable between floors of a building

  33. What is broadcast radio? A wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home Slower and more susceptible to noise than physical transmission media Wireless Transmission Media receiver accepts the broadcast radio signal must have an antenna that is located in the range of the signal transmitter sends the broadcast radio signal transceiver both sends and receives signals from wireless devices

  34. What is cellular radio? A form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cellular telephones A cellular telephoneis a telephone device that uses radio signals to transmit voice and digital data messages Wireless Transmission Media mobile telephone switching office (MTSO) calling party in auto cell public switched telephone network cell cell base station (microwave station) cell called party

  35. What is a microwave station? An earth-based reflective dish that contains the equipment necessary for microwave communications Microwaves are extremely high-speed signals Line-of-sight towers Must transmit in a straight line Wireless Transmission Media

  36. What is a communications satellite? A space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signals back over a wide area to any number of earth-based stations Transmission to a satellite is an uplink Transmission from a satellite to an earth-based station is a downlink Wireless Transmission Media

  37. What is infrared (IR)? A wireless transmission media that sends signals using infrared light waves Requires a line-of-sight transmission Many computers and devices have an IrDA port that enables the transfer of data using infrared light rays Wireless Transmission Media

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