Understanding Computers, Chapter 7

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Chapter 7 Computer Networks
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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.

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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.

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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

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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

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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 isnt available
• Dual-mode phones
• Allows users to make telephone calls on more than
  one network
• Cellular / Wi-Fi dual mode phone are most popular

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Networking and Communications Applications
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Networking and Communications Applications

• Paging
• Sending short numeric or text messages to a
  persons pager
• Most often used for onsite paging applications
• Messaging
• Two-way paging
• Most often takes place today via a mobile phone

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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

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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

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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

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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

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Networking and Communications Applications

• Telemedicine Use of communications technology to
  provide medical information and services
• Remote monitoring and consultations
• Remote diagnosis
• Telesurgery

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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

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Network Topologies
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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

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Types of Networks

• Peer-to-peer networks All computers at the same
  level)
• Internet peer-to-peer (P2P) computing Performed
  via the Internet

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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

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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

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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

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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)

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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)

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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

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Type of Connections
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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

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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

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Wired Network Transmission Media
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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

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Wireless Network Transmission Media
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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
• Todays phones are third-generation
• 4G service is beginning to become available

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Cellular Radio Transmissions
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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

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Microwave and Satellite Transmissions
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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

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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

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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

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Ethernet
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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

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TCP/IP
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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

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Wi-Fi (802.11)
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Wi-Fi (802.11)

• Various standards
• Current standard is 802.11g
• Emerging standard is 802.11n

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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

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WiMAX, Mobile WiMAX, and Mobile-Fi
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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

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Bluetooth
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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

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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

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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

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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

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Network Adapters
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Networking Hardware

• Modem Device that connects a computer to the
  Internet or to another computer
• Term used for Internet connection device, even if
  not connecting via a phone line
• Type of modem needed depends on the type of
  Internet access being used
• Conventional dial-up
• Cable
• Fixed wireless
• DSL
• These and other types of Internet access are
  discussed in Chapter 8

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Modems
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Networking Hardware for ConnectingDevices and
Networks

• Hub Central device that connects all of the
  devices on the network
• Switch Connects devices and identifies the
  device on the network for which the data is
  intended and sends the data only to that node
• Wireless access point Used to connect devices to
  a network wirelessly
• Gateway A devices that connects two different
  networks
• Bridge Usually connects wired LANs
• Router Connects networks and plans path (routes
  traffic)
• Can be wired or wireless

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Other Networking Hardware

• Repeater Amplifies signals along a network
• Range extender Repeater for a wireless network
• Antenna Used when Wi-Fi networks need to go
  further than hardware normally allows
• Higher-gain antennas can be used with routers
• Some network adapters can use an external antenna
• Multiplexer Combines transmissions from several
  different devices to send them as one message
• Concentrator Combines messages and sends them
  via a single transmission medium in such a way
  that all of the messages are active

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Networking Hardware
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Summary

• What Is a Network?
• Networking and Communications Applications
• Types of Networks
• How Does Data Travel Over a Network?
• Networking Standards and Communications Protocols
• Networking Hardware