1. Chapter 09: Communications and Networks

2. Competencies (Page 1 of 2)
Discuss connectivity, the wireless revolution, and communication systems.
Describe physical and wireless communications channels.
Discuss connection devices and services, including dial-up, DSL, cable, satellite, and cellular.
Describe data transmission factors, including bandwidths and protocols.

3. Competencies (Page 2 of 2)
Discuss networks and key network terminology including network interface cards and network operating systems.
Describe different types of networks, including local, home, wireless, personal, metropolitan, and wide area networks.
Describe network architectures, including topologies and strategies.
Describe the organization issues related to Internet technologies and network security.

4. Introduction We live in a truly connected society.
Increased connectivity potentially means increased productivity, especially in business.
You will learn more about the concept of connectivity and the impact of the wireless revolution in this chapter.

5. Communications
Computer communications is the process of sharing data, programs, and information between two or more computers
Numerous applications depend on communication systems, including
Instant messaging
Internet telephone
Electronic commerce
Global positioning systems (GPS)
Ask students to give examples of communication devices that they use daily

6. Communications Today
Connectivity uses computer networks to link people and resources
The Wireless Revolution
Single most dramatic change in connectivity and communications has been widespread use of mobile telephones with wireless Internet connectivity
Connectivity is a concept related to using computer networks to link people and resources
Microcomputers. minicomputers, and mainframes can all be connected
Wireless revolution
Use of mobile or wireless devices
The revolution is the support of more than just the wireless telephone
Many devices can and will connect to one another without any physical connection

7. Communication Systems
Four basic elements
Sending and receiving devices
Communication channel
Connection devices
Data transmission specifications
Electronic systems that transmit data from one location to another
Communication systems can be wired or wireless
Basic elements
Sending and receiving devices – computer or a specialized communication device
Communication channel – carries the message
Connection devices – act as an interface between sending and receiving devices; convert outgoing messages into packets (key term) that can travel across the communication channel
Data transmission specifications – rules and procedures that coordinate the sending and receiving devices

8. Communication Channels
Communication channels carry the data from one computer to another
Two categories of communication channels
Physical connection
Wireless connection
Channels are essential to a communication system
They carry data
Types of channels
Telephone lines (key term)
Coaxial cables(key term)
Fiber-optic cable (key term)
Infrared (key term)
Broadcast radio (key term)
Microwave (key term)
Satellite (key term)

9. Physical Connections Ethernet cable (Twisted pair cable) Coaxial cable
Fiber-optic cable
Ethernet cable – consists of twisted pair cable; slowest; being phased out by more advanced and reliable media
Coaxial cable – single solid copper core; 80 times transmission of twisted pair; television and computer networks
Fiber optic – 26,000 times capacity of twisted pair cable; more secure and reliable; best over limited distances; lighter, more reliable, and less expensive than coaxial cable
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10. Wireless Connections Radio frequency (RF) Microwave Satellite Infrared
Wi-Fi (wireless fidelity)
Bluetooth (short-range)
WiMax (extends Wi-Fi)
Microwave
Satellite
Global positioning system (GPS)
Infrared
Short distances and line of sight
Wireless connections do not use a solid substance to connect; uses the air itself
Types of wireless connections are:
Infrared
Light waves used over short distances
Sometimes called line of sight communications
Sending and receiving devices must be in clear view of one another
Broadcast radio
Uses towers called transceivers (key term)
Web-enabled devices follow a standard known as Wi-Fi (wireless fidelity)
Microwave
Uses high-frequency radio waves
Also line of sight
Used for short distances
Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations; many of these offered by Intelsat, the International Telecommunications Satellite Consortium which is owned by 114 governments and forms a worldwide communications system
Satellites can be used to send and receive data; Uplink is sending data to satellite and Downlink refers to receiving data from a Satellite
GPS (Global Positioning system) use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth
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11. Communication Channels Summary

12. Connection Device Signals
Types of signals
Analog
Digital
Signals
Sent analog – telephone signals; continuous electronic wave
Sent digital – computer signals; presence or absence of an electronic pulse; on/off

13. Connection Devices Types of modems Telephone modem
DSL (digital subscriber line)
Cable modem
Wireless modem (WWAN)
Modem – modulator-demodulator
Modulation (key term) is the name of the process for converting from digital to analog
Demodulation (key term) is the name of the process for converting from analog to digital
Telephone – can be either internal or external; connects computer directly to a telephone line
DSL – uses standard phone lines; external and uses either USB or Ethernet
Cable – coaxial cable – same as your television; uses either USB or Ethernet
Wireless modem
Does not use cables
Also known as WWAN (wireless wide are network modem) (key term)
Signals are sent through the air
Transfer Speed or transfer rate (key term)-measured in bits per second (key term); the higher the speed the faster the transfer rate

14. Connection Services Dial-Up services Leased lines – T1
Uses phone lines
Leased lines – T1
Faster T3 and DS3
Replaced by optical carrier (OC) lines
Digital subscriber line (DSL)
ADSL is most widely used type of DSL
Cable
Uses existing TV cable
Speeds as fast as DSL
Satellite connection services
Use almost anywhere
Slower than DSL and cable modem
Cellular Services
Use 3G and 4G cellular network to provide wireless connectivity
Standard telephone lines and conventional modems use a dial-up service
Slow
Still popular, but many are using other types of connections
T1, T2, T3, and T4 leased lines – do not require conventional modems and provide very high capacity and is expensive—mainly used by corporations not typical end user; T1 lines provide a speed of 1.5 mbps (mega bits per second)(key term) which is over 26 times as fast as a conventional modem
DSL – uses existing telephone lines to provide high-speed connections; uses DSL modems
Cable – Cable connections reach 90% of homes in America but not all cable companies support cable modems presently
Satellite/air connection services – Uses just what it says—satellite and air connections; older satellites couldn’t upload and dial up was still used for the process; but newer satellites are two-way satellites capable of handling both uploading and downloading; available almost anywhere but slower than DSL
Cellular services – option for mobile devices and laptops using 3G and 4G cellular networks (key term) – current access is limited but growing – download speed 400 – 700 Kpbs and upload at 50 Kbps – future service to have speeds equal to DSL

15. Connection Costs and Speeds
Typical user connection costs, bandwidth speeds, and comparable time required to download an image
This is a good time to discuss the various connection services available to the public
Verizon
Time Warner
Comcast
Others

16. Bandwidth
Measurement of the width or capacity of the communication channel
Categories
Voice band (or low bandwidth)
Medium band
Broadband
Baseband
Several technical matters affect data communications
One is bandwidth – bits-per-second (bps) transmission capability of a channel
Three types:
Voiceband – also known as low bandwidth; standard phone line; too slow for many types of transmissions – especially high-quality video; typical speeds are 56 to 96 kbps
Medium band – with special leased lines to connect minicomputers and mainframes as well as to transmit data over long distances (for larger computer systems); not typically used by individuals
Broadband – used for high-capacity transmissions (DSL, cable, satellite connections); specialized high-speed devices; effectively transmits high-quality video and other communication needs; typically 1.5 mbps; higher speeds possible
Baseband – widely used to connect individual computers that are located close to one another

17. Protocols Communication rules for exchanging data between computers
Internet standard: TCP/IP (Transmission control protocol/Internet protocol)
Identification – unique IP address
Packetization – broken down and reassembled
Rules for exchanging data between computers
Essential features of protocol
Identification - Identifying sending and receiving devices (IP address); (key term) Internet unique number address; domain name server (DNS) (key term) converts text-based addresses to IP addresses
Packetization – allows message to be broken into so easier to transmit over Internet through various interconnected networks; allows message to be reassembled at destination

18. Networks
A computer network is a communication system that connects two or more computers
Allows exchange of information and resources
A computer network is a communication system that connects two or more computers so that they can exchange information and share resources

19. Computer Networks Node Client Server Directory server Host Switch
Network interface cards (NIC)
Network operating systems (NOS)
Network administrator
Node – any device connected to a network
Client – a node that requests and uses resources available from other nodes
Server – a node that shares resources with other nodes; dedicated servers specialize in performing specific tasks—could be an application server, communication server, database server, file server, printer server, or Web server
Directory server – a specialized server that manages resources such as user accounts for an entire network
Host – large centralized computer
Switch – the center or central node for other nodes; previously done by something called a hub
Network interface cards (NIC) – connects the computer to a network
Network operating system (NOS) – software to control and coordinate activities between computers on a network
Network administrator – a computer specialist; network administrator

20. Network Types Local area network (LAN) Home network
Wireless LAN (WLAN)
Personal area network (PAN)
Metropolitan area network (MAN)
Wide area network (WAN)
Communications networks differ in geographical size. Three important types are:
LANs
Computers and devices linked in close proximity to each other
Linked by cable
Typically use a bus (key term) form of organization
With gateways, LANs can be connected to other LANs or any other type of network. Ethernet (key term) is one standard for connecting network nodes together.
Home Networks – LANs are now being commonly used by individuals in home/apartments; allow different computers to share resources including a common Internet connection; can be connected by various means including a wireless LAN (key term) (WLAN) that uses radio frequencies to connect computers; all communications pass through the network’s centrally located wireless receiver (key term) or base station (key term)
Home networking includes the following:
Radio frequency, telephone lines, electric wiring, cables, NIC/adapter cards
Wireless LAN – wireless local area network
All communications pass through the network’s centrally located wireless access point
Personal Area networks – works within a very small area
Connects cell phones to headsets, PDAs to other PDAs, keyboards to cell phones, etc.
MANs (metropolitan area network) – also known as a regional network; (key term) span distances up to 100 miles
Network linking nodes and resources within the geographical bounds of a city
Cellular phones can extend the reach of a MAN
WANs (wide area networks)
Countrywide and worldwide networks
Use microwave relays and satellites to reach users
Internet is the widest WAN

21. Network Architecture Arrangement is called topology
Types of network topology
Legacy
Bus
Ring
Current
Star
Tree
Hybrid
Mesh
Networks are connections of two or more computers that work together to exchange information and share resources
The network architecture describes how the network is arranged and how the resources are coordinated and shared
Network architecture also describes how a computer network is configured and what strategies are used
 Topology – network arrangement or configuration

22. Bus Network
Each device is connected to a common cable, called a bus or backbone
All communications travel along this bus
There is no host; messages are passed device-to-device in a sequence
Bus network (key term)– each device handles its own communications control
No host
Common connecting cable called a bus or backbone
Not as efficient as star, but it is low cost and widely used
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23. Ring Network Each device is connected to two other devices
No central file server or computer
Useful in a decentralized environment
Ring network (key term)
Each device connected to two others forming a ring
No central files server or computer
Messages passed around ring until reach correct destination
Often used to link mainframes—especially over wide geographical areas
Useful in decentralized organization
Makes possible distributed data processing system (key term)
Computers can perform processing tasks on own
Can also share programs, data, and other resources
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24. Star Network
Most widely used network topology for both homes and large businesses
Each device connects directly to a central network switch
Host – large centralized computer, usually a mainframe
Star network (Key Term) – nodes are connected to a single computer called a network hub
All communications pass through the switch; each connecting device is asked (“polled”) whether it has a message to send and then each device is in turn allowed to send its message
Most widely used network topography today
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25. Tree Network
Each device is connected to a central node, either directly or through subordinate nodes
Also known as a hierarchical network
Tree Network (key term)
Sometime called a hierarchical network
The central node is connected to two or more subordinate nodes that in turn are connected to other subordinate nodes
Useful in centralized organization
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26. Hybrid Network Combination of different topologies
Large organizations have a complex network of smaller networks
These smaller networks use a variety of configurations
When connected together, they form a hybrid
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27. Mesh Network
Does not use a specific physical layout, but requires that each node have more than one connection to other nodes
Wireless technologies are frequently used
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28. Network Topologies

29. Network Strategies Terminal server network Client/server network
Peer-to-peer (P2P) network
Distributed processing network
Every network has a way of coordinating the sharing of information and resources
There are four common strategies:
Terminal server network – processing power is centralized in one large computer
Terminal Server
Client/Server
Peer-to-Peer

30. Organizational Networks
Intranets
Private network within an organization
Works like the Internet, where employees use browsers to access Web sites and Web pages
Extranets
Private network that connects organizations
Works like the Internet, but provides suppliers and other trusted partners with limited access to the organization’s networks
Intranet – Intranets use browsers, Web sites, and Web pages like the public Internet; typically include , mailing lists, newsgroups, and FTP services
Extranet – Purpose is to increase efficiency and reduce costs

31. Network Security Firewalls Intrusion detection systems (NIDS)
Combination of hardware and software
Proxy server provides pass-through access
Protects against external threats
Intrusion detection systems (NIDS)
Virtual private networks (VPN)
Creates a secure private network connection between your computer and the organization
Firewalls – Organizational firewalls include a proxy server (key term) that is a gatekeeper; all communications between the outside world and an organization must pass through the proxy server where the source and content of each communication is evaluated; end users have many of the same concerns regarding security as organizations and can use firewalls as well. See Figure 9-27.
Intrusion detection systems (NIDS) (keyword)
Uses advanced pattern matching and heuristics
Can recognize signs of a network attack and disable access before an intruder can do damage
Virtual private network (VPN)
Creates a secure private connection between a remote user and an organizations’ internal network
Creates the equivalent of a dedicated line between a user’s home or laptio computer and a company server

32. Careers In IT Network Administrator
Manages a company’s LAN and WAN networks
Maintains networking hardware and software, diagnosing and repairing problems that arise
Candidates usually have a bachelor’s degree in computer science and practical experience
Annual salary is typically between $48,500 and $79,000

33. A Look to the Future
Telepresence Lets You Be There without Actually Being There
Seeks to create the illusion that you are actually at a remote location
Early implementations mainly focus on an extension of video-conferencing

34. Open-Ended Questions (1 of 2)
Define and discuss connectivity, the wireless revolution, and communications.
Identify and describe the various physical and wireless communication channels.
Identify the standard Internet protocol and discuss its essential features.
Have students turn to the end of Chapter 9 in their textbooks to view the same “Open-Ended” questions/statements

35. Open-Ended Questions (2 of 2)
Discuss past and present network topologies.
Define and discuss four common network strategies.
Have students turn to the end of Chapter 9 in their textbooks to view the same “Open-Ended” questions/statements