Today and Tomorrow 12 th Edition Understanding Computers Chapter 7: Computer Networks.

Today and Tomorrow 12th Edition

Understanding Computers

Chapter 7:

Computer Networks

Chapter 7 Understanding Computers, 12th Edition 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.


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.


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


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


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





• 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



• 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



• 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



• 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



• 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



• Telemedicine: Use of communications technology to provide medical information and services

– Remote monitoring and consultations

– Remote diagnosis

– Telesurgery


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


Network Topologies


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


Types of Networks• Peer-to-peer networks: All computers at the same

level)

– Internet peer-to-peer (P2P) computing: Performed via the Internet


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


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


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


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)


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)


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


Type of Connections


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


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


Wired Network Transmission Media


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


Wireless Network Transmission Media


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


Cellular Radio Transmissions


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


Microwave and Satellite Transmissions


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


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


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


Ethernet


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


TCP/IP


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


Wi-Fi (802.11)


Wi-Fi (802.11)• Various standards

– Current standard is 802.11g

– Emerging standard is 802.11n


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


WiMAX, Mobile WiMAX, and Mobile-Fi


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


Bluetooth


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


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


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


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


Network Adapters


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


Modems


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


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


Networking Hardware


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

Today and Tomorrow 12 th Edition Understanding Computers Chapter 7: Computer Networks.

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computer networks

collection of computers

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