1. Chapter 7:
Computer Networks

2. 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.

3. 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.

4. 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

5. 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

6. 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 isn’t available
Dual-mode phones
Allows users to make telephone calls on more than one network
Cellular / Wi-Fi dual mode phone are most popular

7. Networking and Communications Applications

8. Networking and Communications Applications
Paging
Sending short numeric or text messages to a person’s pager
Most often used for onsite paging applications
Messaging
Two-way paging
Most often takes place today via a mobile phone

9. 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

10. 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

11. 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

12. 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

13. Networking and Communications Applications
Telemedicine: Use of communications technology to provide medical information and services
Remote monitoring and consultations
Remote diagnosis
Telesurgery

14. 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

15. Network Topologies

16. 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

17. Types of Networks
Peer-to-peer networks: All computers at the same level)
Internet peer-to-peer (P2P) computing: Performed via the Internet

18. 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

19. 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

20. 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 = at least 1 byte at a time

21. 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)

22. 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)

23. 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

24. Type of Connections

25. 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

26. 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

27. Wired Network Transmission Media

28. 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

29. Wireless Network Transmission Media

30. 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
Today’s phones are third-generation
4G service is beginning to become available

31. Cellular Radio Transmissions

32. 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

33. Microwave and Satellite Transmissions

34. 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

35. Networking Standards and Communications 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

36. 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

37. Ethernet

38. 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

39. TCP/IP

40. Wi-Fi (802.11)
Wi-Fi (Wireless Fidelity): A family of wireless networking standards using the IEEE standard
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

41. Wi-Fi (802.11)

42. Wi-Fi (802.11) Various standards Current standard is 802.11g
Emerging standard is n

43. WiMAX, Mobile WiMAX, and Mobile-Fi
WiMAX (Worldwide Interoperability for Microwave Access or ): 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

44. WiMAX, Mobile WiMAX, and Mobile-Fi

45. 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

46. Bluetooth

47. 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

48. 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

49. 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

50. 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

51. Network Adapters

52. 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

53. Modems

54. Networking Hardware for Connecting Devices 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

55. 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

56. Networking Hardware

57. 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