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Networks
• A network is a collection of computers and devices connected together via communications devices and transmission media
• Advantages of a network include:
Facilitating communications
Sharing hardware
Sharing data and information
Sharing software
Transferring funds
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Bandwidth
• Measurement of the capacity of the channel• Categories – Voiceband also known as low bandwidth– Medium band – Broadband• Used for high capacity transmission• Used by DSL, cable, and satellite
Protocols
• Set of communication rules• Standard for Internet: TCP/IP (Transmission
control protocol/Internet protocol)– Identification – Reformatting
Network Classifications
• Local area networks (LAN)• Home networks
– WLAN (Wireless LAN)• Metropolitan area networks (MAN)• Wide area networks (WAN)
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Network Classifications
• A local area network (LAN) is a network that connects computers and devices in a limited geographical area
• A wireless LAN (WLAN) is a LAN that uses no physical wires
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Network Classifications
• A metropolitan area network (MAN) connects LANs in a metropolitan area
• A wide area network (WAN) is a network that covers a large geographical area
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Network Architecture
• The design of computers, devices, and media on a network is sometimes called the network architecture
Client/server Peer-to-peer
Terminal
Peer-to-peer (P2P) Model
Client
Server
Client
Client Client
Client/Server Model
Peer Peer
Server must be prepared to serve multiple clients at any time.
Peers communicate as equals on a one-to-one basis.
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The Client/Server Model• When processes need to communicate:
• Examples:– file server– mail server– web server =>
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The Client/Server Model (continued)• Client & server have strictly defined roles:
– client sends request – then waits for answer– server accepts request – processes & returns answer
• Protocols, defining how to:– encode messages– address messages– handle sending and
receiving
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• Protocols: Example• http, ftp
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The Peer-to-peer Model
• P2P describes an Internet network on which users access each other’s hard disks and exchange files directly over the Internet
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Network Topology
• A network topology refers to the layout of the computers and devices in a communications network
Star network Bus network Ring network
Network Topology
• Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer.
• Types of network topology– Star– Bus– Ring– Hierarchical
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Star Network
• Smaller computers linked to a central unit
• Central unit is called the network hub
• Control is maintained by polling
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Bus Network • Each device handles its own communication control• There is no host computer• Has a common connecting cable called a backbone
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Ring Network
• Each device is connected to two other devices
• No central file server or computer
• Useful in a decentralized environment
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Hierarchical Network
• Several computers linked to a central host
• Computers are hosts to other computers
• Useful in centralized organizations
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Principal Network Configurations
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Network Communications Standards
Ethernet Token ring TCP/IP Wi-Fi
Bluetooth UWB IrDA RFID
WiMAX WAP
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Network Communications Standards
Ethernet is a network standard that specifies no computer controls when data can be transmitted
The token ring standard specifies that computers and devices on the network share or pass a special signal (token)
TCP/IP is a network standard that defines how messages are routed from one end of a network to another
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Network Communications Standards
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Network Communications Standards
• Wi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication
• Sometimes referred to as wireless Ethernet
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Network Communications Standards
• Bluetooth defines how two Bluetooth devices use short-range radio waves to transmit data
• UWB (ultra-wideband) specifies how two UWB devices use short-range radio waves to communicate at high speeds
• IrDA transmits data wirelessly via infrared (IR) light waves• RFID uses radio signals to communicate with a tag placed in
or attached to an object, animal, or person
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Network Communications Standards
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Network Communications Standards
WiMAX (802.16)
• Developed by IEEE• Towers can cover a 30-mile
radius• Two types are fixed
wireless and mobile wireless
• Provides wireless broadband Internet access
Wireless Application Protocol (WAP)
• Specifies how some mobile devices can display the content of Internet services• Web• E-mail• Chat rooms
• Uses a client/server network
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Communications Software
• Communications software consists of programs that:
Help users establish a connection to
another computer or network
Manage the transmission of
data, instructions, and information
Provide an interface for users to communicate with one another
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Communications Over the Telephone Network
• The public switched telephone network (PSTN) is the worldwide telephone system
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Communications Over the Telephone Network
Dial-up lines
Dedicated line ISDN line
DSL FTTP T-carrier line
ATM
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Communications Over the Telephone Network
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Communications Over the Telephone Network
• ADSL connections transmit data downstream at a much faster rate than upstream
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Home Networks
• Home networks provide computers with the following capabilities:
Connect to the Internet at the
same time
Share a single high-speed Internet
connection
Access files and programs on other
computersShare peripherals
Play multiplayer games
Connect game consoles to the
Internet
Subscribe to and use VoIP
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Home Networks
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Organizational Internets• Intranets– Private network within an organization– Provides information to employees
• Extranets– Private network that connects
organizations– Used to allow suppliers and others
access • Firewalls– Security system – Protects against external threats
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Careers In IT
• Network Administrator– Manage a company’s LAN and
WAN networks– Maintain hardware and
software– Diagnose and repair problems– Candidates usually have a
bachelor’s degree in computer science and practical experience
– Annual salary is typically between $43,000 and $68,000
