Communications & Networks Chapter 8 Communications & Networks

Overview Identify Various Communication Uses List Network Advantages Differentiate Network Types Describe Communications Standards Describe Communications Devices Identify Different Transmission Media

Communications Two or More Devices Requirements Transfer Data or Instructions Requirements Sending Device Communications Device Connects Sending Device to Channel Connects Channel to Receiving Device Communications Channel Media on Which Data Travels Receiving Device

Uses Wireless Messaging Text Messaging Picture Messaging Send / Receive Text Messages Using Phone 14-17: 60 v. 5 Picture Messaging Send / Receive Graphics, Pictures, Video Sexting: 30% of 17-year-olds Loss of Reaction : Alcohol=12%, Marijuana=21%, Texting=35% Pew Internet 5/10 Pew Internet 12/09

Uses GPS (Global Positioning System) Groupware Signals Sent by Satellites Orbiting Earth Signal Sent Every 1/1000 of a Second Earth-based Receivers Analyze Signals Determine Receiver’s Geographic Location Groupware Assists Groups in Working Together Share Data Over Network e.g., Schedule Meetings

Uses Web Services Software Applications Mashup Communicate with Other Remote Computers Use Internet or Internal Business Network Mashup Combines Services from Multiple Sources

Uses Very Hard to Give Up Pew Internet 3/08

Networks Collection of Computers & Devices Connected via Advantages Communications Devices Transmission Media Advantages Facilitating Communications Sharing Hardware Sharing Software Sharing Data And Information

Network Types LAN (Local Area Network) WLAN WAN (Wide Area Network) Network in Limited Geographical Area Typically Within a Building WLAN Wireless LAN WAN (Wide Area Network) Large Geographic Area Uses Many Types of Media Internet

Network Architectures Client/Server Client Requests Resource Accessed from Server Server One or More Computers Controlling Resource P2P (Peer-to-Peer) Access Any Other Computer in Network Internet File Sharing

Network Topology Configuration of Devices in a Network Bus Consists of Single Central Cable All Devices Connect to it Inexpensive & Easy to Install

Network Topology Ring Star Cable Forms Closed Ring Data Travels In One Direction Expensive & Difficult to Install Star All Devices Connect to Hub All Data Passes Through Hub Bottlenecks Can Occur Easy to Install

Intranet & Extranet Intranet Extranet Internal Corporate Network Uses Internet Accessible to Corporate Employees Facilitates Working in Groups Extranet Allows Access to Parts of a Intranet Customers / Suppliers

Protocol Protocol Collection of Procedures Type of Error Checking Used Establish, Maintain, & Terminate Transmissions Type of Error Checking Used Data Compression Method, If Any Indicate Finished Sending Message Indicate Message Has Been Received

Standards Ethernet TCP/IP For LANs Uses Bus or Star Topology Widely Implemented TCP/IP Used for Internet Transmissions Packet Switching Transmits Data by Breaking it Into Packets Reassembles Data at Destination

Standards 802.11 (Wi-Fi) 802.16 (WiMAX) Bluetooth WAP Family of Standards for Wireless LANs 802.16 (WiMAX) Towers Cover 30-mile Radius Provides Wireless Broadband Internet Bluetooth Short-range Radio Technology WAP Wireless Mobile Devices Connect to Internet

Standards IrDA RFID Data Transferred via Infrared Light Waves Radio Signals Communicate with Tags Failed Legislation Nevada Require Retailers to Inform Customers Rhode Island Government Agency Cannot Track Individuals Texas Prohibit Schools from Using RFID on Students

Types & Speeds Measured in bps (Bits per Second)

Devices Modem DSL Modem Cable Modem Converts Analog to Digital & Vice Versa Required for Telephone Line Communication DSL Modem Cable Modem Uses Cable TV Network

Devices Wireless Modem Network Card Wireless Access Point Internet Access Network Card Connects PC to Network Wireless Access Point

Devices Router Hub / Switch Connects Multiple Computers / Routers Transmits Data to Network Destination Uses Fastest Available Path Many Protected by Hardware Firewall Hub / Switch Provides Central Point for Network Cables

Channel Communication Path Between Devices Bandwidth Latency Difference Between Frequencies Amount of Data that Travel Over Channel Latency Time for Signal to Travel From One Network Location to Another

Channel Broadband Transmission Media Transmit Multiple Signals over Channel Transmission Media Materials or Techniques Capable of Carrying Signals

Physical Transmission Media Twisted-pair Telephone System Coaxial Cable Cable Television Fiber-optic Thin Strands of Glass or Plastic Uses Light to Transmit Signals Less Susceptible to Interference More Secure

Wireless Transmission Media Broadcast Radio Distributes Radio Signals Long & Short Distances Cellular Radio Widely Used for Mobile Communications

Wireless Transmission Media Microwave Station Earth-based Reflective Dish Contains Antenna, Transceivers Uses Line-of-sight Transmission Satellite Space Station Receives Microwave Signals Amplifies Signals Broadcasts Signals Back