Discovering Computers 2008 Chapter 9 Communications and Networks Communications -- Telecommunications What are computer communications? Process in which two or more computers or devices transfer data, instructions, and information notebook computers smart phones servers Web-enabled PDAs GPS receivers desktop computers mainframe computers Tablet PCs p. 460 Fig. 9-1 Blackberry Video Next Networks – Local Area Network What is a local area network (LAN)? Network in limited geographical area such as home or office building p. 471 Fig. 9-10 Metropolitan area network (MAN) connects LANs in city or town Next Communication Devices -- Hardware Requirements Sending Device Initiates Instruction to Transmit Communications Device Connects Sending Device to Channel Connects Channel to Receiving Device Communications Channel or Transmission Media Media on Which Data Travels Receiving Device p. 460 Accepts Transmission Communications Devices What are examples of communications devices? Common types are dial-up modems, ISDN and DSL modems, cable modems, network cards, wireless access points, routers, and hubs ISDN and DSL modems send and receive data from ISDN and DSL lines p. 482 Next Communications Channel also known as Transmission Media What are examples of transmission media? Transfer Rates for Various Types of LANs Using Physical Transmission Media Wire, cable, and other tangible materials used to send communications signals p. 490 Fig. 9-35 Next Wireless Transmission Media What is wireless transmission media? Used when inconvenient, impractical, or impossible to install cables Includes Bluetooth and IrDA p. 494 Fig. 9-40 Networks Collection of Computers & Devices Connected via Communications Devices -- Slide 5 Transmission Media – Slide 6 Uses of Computer Communications What are some uses of communications technology? Internet Chat Rooms FTP p. 462 Web Instant Messaging E-Mail Newsgroups Web Folders Internet Telephony Video Conferencing Fax Machine or Computer Fax/Modem Next Uses of Computer Communications What are Wireless Messaging Services? Text Messaging Send / Receive Short Text Messages Using Phone Picture Messaging Send / Receive Graphics, Pictures, Video, Sound Uses of Computer Communications What is a global positioning system (GPS)? Step 1. GPS satellites orbit Earth. Every 1/1000 of a second, each satellite sends a signal that indicates its current position to the GPS receiver. Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click GPS below Chapter 9 p. 466 Fig. 9-6 Step 2. A GPS receiver (such as in a car, a wearable device, a smart phone, a handheld device, or a collar) determines its location on Earth by analyzing at least 3 separate satellite signals from the 24 satellites in orbit. Next Uses of Computer Communications What is groupware? Groupware is software that allows people work together and share information MS Office 2007: SharePoint Server: A big share drive to share files with others at the college. SharePoint video Google Wave p. 467 Fig. 9-7 Next Network Types LAN (Local Area Network) Network in Limited Geographical Area Typically Within a Building Network Types What is a wide area network (WAN)? Network that covers large geographic area using many types of media Internet is world’s largest WAN p. 472 Fig. 9-12 Next Network Types What is a client/server network? One or more computers act as server and other computers, or clients, access server Clients request RESOURCES on the server p. 472 Fig. 9-13 Next Networks What is a site license? Legal agreement that allows multiple users to run a software package simultaneously License fee usually based on number of users or number of computers attached to network www.cursorarts.com/ca_price.html Networks What are the components of a client/server network? File server Workstation Network interface card UPS Network Operating System Printers Backups p. 472 Fig. 9-12 Next Network Types What is a peer-to-peer network? Simple network that connects fewer than 10 computers Each computer, or peer, has equal capabilities p. 473 Fig. 9-14 Next Network Types What is Internet peer-to-peer (P2P)? Sometimes called a file sharing network Enables users to connect to each other’s hard disks and exchange files directly Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click BitTorrent below Chapter 9 p. 473 - 474 Fig. 9-15 Next Criticism Illegal music/video sharing Kazaa Napster The Pirate Bay Strain on ISP Bandwidth supply < Bandwidth demand Network Topology Layout of devices in a network Popular types of topology Bus Ring Star Bus Topology What is a bus network? All computers and devices connect to central cable, or bus Star Topology What is a star network? All devices connect to a central device, called hub All data transferred from one computer to another passes through hub p. 475 Fig. 9-17 Next Networks What is a ring network? Cable forms closed ring, or loop, with all computers and devices arranged along ring Data travels from device to device around entire ring, in one direction p. 474 Fig. 9-16 Next Networks What is an intranet? Internal network that uses Internet technologies Makes information accessible to employees Typically includes connection to Internet Don’t confuse and intranet with: Extranet allows customers or suppliers to access part of company’s intranet p. 475 Next Networks What is an extranet? Allows customers or suppliers outside of the company to access part of company’s intranet Customer checking package on Fed Ex’s intranet via the Internet Bus Topology What is a bus network? All computers and devices connect to central cable, or bus Protocol & Standards -- Wired Ethernet How Ethernet Cards Work For LANs Uses Bus or Star Topology One of Most Widely Implemented Standards Protocol & Standards -- Wired TCP/IP-- Transmission Control Protocol/Internet Protocol Commonly Used for Internet Transmissions Packet Switching Transmits Data by Breaking it Into Packets Reassembles Data at Destination TCP/IP Animation Network Communications Standards Wi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication Sometimes referred to as wireless Ethernet Compare speeds: 802.11n vs. 802.11g 30 How to Setup a Wireless Network http://www.youtube.com/watch?v=hlvYyWbzVa0 Network Communications Standards Bluetooth limited to: 10 meters = 33 ft. TO 100 meters = 330 ft. Short-range Radio Technology IrDA Data Transferred via Infrared Light Waves p. 477 - 478 Fig. 9-20 Next Protocols & Standards RFID -- Radio Frequency Identification – replace bar code reader Uses Radio Signals Communicates with Tag Placed in Object Legislation Nevada – Require Retailers to Inform Customers Product is Tagged Rhode Island – No Government Agency can Use to Track Individuals TX – Prohibit Schools from Using RFID on Students How RFID Works RFID and Sushi Network Communications Standards Communications Over the Telephone Network What is a dial-up line? Temporary connection using telephone line for communications Costs no more than making regular call Computers at any two locations can establish a connection using modems and telephone network Communications Over the Telephone Network The Telephone Network What is transfer rate? Speed at which a line carries data and information Faster the transfer rate, the faster you can send and receive data and information Usually expressed as a measure of bits per second bits per second (bps) kilobits per second (Kbps) megabits per second (Mbps) gigabits per second (Gbps) Communications Over the Telephone Network What is a dedicated line? Always-on connection between two communications devices ISDN DSL T-carrier line ATM -- Asynchronous Transfer Mode p. 482 Fig. 9-24 Next Communications Devices --Wired What are ISDN and DSL modems? Communications devices that send and receive digital ISDN and DSL signals Usually external devices in which one end connects to a telephone line and the other end connects to a port on the system unit p. 485 Next Communications Devices What is a cable modem? Sends and receives data over cable television network Much faster than dial-up modem or ISDN Sometimes called a broadband modem Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Cable Modems below Chapter 9 p. 485 - 486 Fig. 9-28 Next Cable Modem vs. DSL Video –Cable & DSL Cable Modem Advantage: Widespread Availability Disadvantage: Competition with shared users DSL Advantage: Not shared with other users Disadvantage: Radius of user and service limited Communications Over the Telephone Network What is an ADSL (asymmetric digital subscriber line)? Popular type of DSL (Digital Subscriber Line) Faster when receiving data than when sending data Ideal for Internet access Next Communications Devices A network card enables a computer or device to access a network Available in a variety of styles Wireless network cards often have an antenna same waves used by cell phones Communications Devices A router connects multiple computers or other routers together and transmits data to its correct destination on a network Many are protected by a hardware firewall Fastest path available Communications Devices A hub or switch connects several devices in a network together What's the difference between a hub and a router? A hub just allows several network cables to be attached, putting several computers on the same network. A router has a processor that allows it to decide where to send traffic, and possibly to modify the details. A hub glues together an Ethernet network segment A router can do those functions plus route TCP/IP packets between multiple PCs on LAN and a WAN Some hubs include routers Home Networks What is a home network? Multiple computers connected in home Several types of wired home networks Ethernet — connect computers via cable Powerline cable — use electrical lines in house Phoneline — use telephone lines Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Home Networks below Chapter 9 p. 489 - 490 Fig. 9-34 Next Communications Channel What is a communications channel? Transmission media on which data travels in communications system – both wired and wireless Transmission media are materials capable of carrying one or more signals p. 491 Bandwidth is amount of data that can travel over a communications channel Next What is physical transmission media? p. 492 Fig. 9-36 Physical Transmission Media What are twisted-pair cable and coaxial cable? Twisted-pair cable is used for telephone systems and network cabling Coaxial cable is often used for cable television wiring p. 493 Fig. 9-37—9-38 Next Physical Transmission Media What is fiber-optic cable? Capable of carrying significantly more data at faster speeds than wire cables Less susceptible to interference (noise) and, therefore, more secure Smaller size (thinner and lighter) 4/9/09 Fiber Optic Cable Security? p. 493 Fig. 9-39 Next Wireless Transmission Media What is wireless transmission media? Used when inconvenient, impractical, or impossible to install cables Includes Bluetooth and IrDA p. 494 Fig. 9-40 Wireless Transmission Media Microwave Station Earth-based Reflective Dish Contains Antenna, Transceivers Uses Line-of-sight Transmission Universities, hospitals, government, cable television –straight line with no obstructions Wireless Transmission Media Satellite Space Station Receives Microwave Signals Broadcasts Signals Back to Earth-based Stations TV, GPS, air navigation