information technology
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INFORMATION TECHNOLOGY
Networks and Telecommunications
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Learning Outcomes
• Summarize the individual components of a computer network
• Describe the three main network topologies• Explain the difference between the three main forms
of network access methods• Summarize the difference between guided media
and unguided media• Explain how a network operating system works• List the transmitting and receiving devices used in a
computer network• Describe the function of TCP/IP• Summarize the use of a VPN
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Introduction
introduces the concept of computer networks Computer network (or network) - a group of
two or more computer systems linked together using wires or radio waves over a geographical area
Computer networks that do not use physical wires are called wireless
takes a detailed look at the key conceptsthat are integrating computer networks and data communications
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The Need for Networking
A network provides two principle benefits: The ability to communicate The ability to share
Groupware - software that supports team interactions and dynamics including calendaring, scheduling, and videoconferencing
is the most popular form of
network communication
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The Benefits of Computer Networking
Store virtually any kind of information at, and retrieve it from, a central location on the network
Combines the power and capabilities of diverse equipment providing a collaborative medium to combine the skills of different people, regardless of physical location
Enables people to share information and ideas easily They can work more efficiently and
productively
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Networking Basics
Networks are assembled according to certain rules: Each cabling strand can only support a certain
amount of network traffic, etc Topology - the actual physical organization of
the computer devices including connections Bandwidth - indicates how much information
can be carried in a given time period over a wired or wireless communications link
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Networking Basics (continued)
The network industry refers to nearly every type of network as an “area network”
Local Area Network (LAN) - connects network devices over a relatively short distance Sometimes one building will contain a few small LANs,
and occasionally a LAN will span a group of nearby buildings
Wide Area Network (WAN) - is a geographically dispersed telecommunications network
Metropolitan Area Network (MAN) - interconnects users in a geographic area or region larger than a local area network, but smaller than a wide area network Example: A university may have a MAN that joins
together many of their local area networks situated around its campus
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Networks – The Big Picture
A network is made up of many physical elements: Computers, printers, and other devices
The manner in which all these items are connected is referred to as the network topology
Network topologies are further subdivided into two categories: Physical topologies Logical topologies
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Physical Topologies
the actual physical organization of the computers on the network and its connections
Bus topology - all devices are connected to a central cable
Star topology - all devices are connected to a hub Ring topology - all devices are connected to one
another in a closed loop Tree topology - combines the characteristics of the
bus and star topologies Wireless topology - all devices are connected by a
receiver/transmitter to a special network interface card that transmits signals between a computer and a server; all within an acceptable transmission range
Physical Topologies
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Network Access Methods (Protocols)
Protocol - the predefined way that someone (who wants to use a service) talks with or utilizes that service
The most popular LAN protocols include: Token Ring Ethernet Fiber Distributed Data Interface (FDDI)
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Token Ring
Token ring network - a LAN in which all computers are connected in a ring or star topology and a token-passing schema is used in order to prevent the collision of data between two computers that want to send messages at the same time
Second most widely used protocol on local area networks
Data transfer rates of either 4 or 16 megabits per second
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Ethernet
Ethernet is the most widely installed LAN access method originally developed by Xerox
When it first began to be widely deployed in the 1980s, Ethernet supported a maximum data rate of 10 megabits per second (Mbps)
Fast Ethernet standards have extended traditional Ethernet technology to 100 Mbps peak
Gigabit Ethernet technology extends performance up to 1000 Mbps
Ethernet and Token Ring Network
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Fiber Distributed Data Interface (FDDI)
FDDI - a set of protocols for sending digital data over fiber optic cable
FDDI networks are token-passing networks that supports data rates of up to 100 megabits per second
FDDI networks are typically used as backbones for wide area networks
Fiber Distributed Data Interface
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Networking Hardware
To be sent from one location to another, a signal must travel along a physical path
The physical path that is used to carry a signal between a signal transmitter and a signal receiver is called the transmission medium
Network transmission media - the various types of media used to carry the signal between computers
Two types of transmission media: Guided and Unguided
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Guided media
Transmissions material manufactured so that signals will be confined to a narrow path and will behave predictably
Three common types of guided media are: twisted-pair wiring, coaxial cable, and fiber optic cable
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Twisted-Pair Wiring
a type of cable composed of four (or more) copper wires twisted around each other within a plastic sheath
The wires are twisted to reduce outside electrical interference
The RJ-45 connectors on twisted-pair cables resemble large telephone jacks
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Coaxial Cable
cable that can carry a wide range of frequencies with low signal loss
Consists of a metallic shield with a single wire placed along the center of a shield and isolated from the shield by an insulator
Two different types Thinnet coaxial cable - similar to the cable
used by cable television companies Thicknet coaxial cable - similar to thinnet
except that it is larger in diameter
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Fiber Optic Cable
Fiber optic (or "optical fiber") - the technology associated with the transmission of information as light impulses along a glass or plastic wire or fiber
Optical fiber cable can transmit data over long distances with little loss in data integrity
Optical fiber is not subject to interference
Cable Summary
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Unguided Media
Unguided media - natural parts of the Earth’s environment that can be used as physical paths to carry electrical signals
Examples include microwaves, infrared light waves, and radio waves
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Transmitting and Receiving Devices
Network adapters Modems Repeaters Wiring
concentrators, hubs, and switches
Bridges, routers, and gateways
Microwave transmitters
Infrared and laser transmitters
Cellular transmitters Wireless LAN
transmitters
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Network Adapters
Network adapter - the hardware installed in computers that enables them to communicate on a network
The most common form is designed to be installed directly into a standard expansion slot inside a PC
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Modems
Modems - provide the means to transmit digital computer data typically over ordinary telephone lines The transmitting modem converts the encoded
data signal to an audible signal and transmits it A modem connected at the other end of the line
receives the audible signal and converts it back into a digital signal for the receiving computer
Modems are commonly used for inexpensive communications between a network and geographically isolated computers
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Repeaters
used to increase the distance over which a network signal can be propagated
A signal travels through a transmission medium, it encounters resistance and gradually becomes weak and distorted
The repeater receives the network signal and retransmits it at the original transmission strength
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Concentrators, Hubs, and Switches
Concentrators, hubs, and switches - provide a common physical connection point for computing devices
Most hubs and all wiring concentrators and switches have built-in signal repeating capability to perform signal repair and retransmission
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Bridges, Routers, and Gateways
used to interconnect network segments Bridges Routers
Bridges and routers - generally used to connect networks that use similar protocols
Gateways used to connect networks that use dissimilar
protocols; examples includes TCP/IP and IPX
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Microwave Transmitters & Receivers
commonly used to transmit network signals over great distances
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Infrared and Laser Transmitters
Infrared and laser transmitters - similar to microwave systems: they use the atmosphere and outer space as transmission media
They require a line-of-sight transmission path Useful for signaling across short distances
where it is impractical to lay cable
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Cellular Transmitters
Cellular transmitters - radio transmissions and therefore have the advantage of being able to penetrate solid objects
A cellular base station at the center of each cell contains: Low-power transmitters Receivers Antennas Common control computer equipment
Cellular devices are configured to operate at low power to avoid interfering with other cellular devices in the area
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Wireless LAN Transmitters
function like hubs and switches in a wired environment, only they propagate signals through radio waves or infrared light instead of wires
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The Network Operating System
an operating system that includes special functions for connecting computers and devices into a local area network
Two categories: Client-server Peer-to-peer
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Client-Server Networks
a versatile, message-based, and modular infrastructure that is intended to improve usability, flexibility, interoperability, and scalability as compared to centralized, mainframe computing
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Thin Client-Server Networks
Thin clients - similar to terminals connected to mainframes, the server performs the bulk of the processing, and the client presents the interface
Thin clients are usually devoid of floppy drives, expansion slots, and hard disks; consequently, the “box” or central processing unit is much smaller than that of a conventional PC
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Peer-to-Peer Networks
Enable networked computers to function as both servers and workstations
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Internet Technology
The world’s largest computer network
Two most influential technologies: Transmission Control Protocol/Internet
Protocol (TCP/IP) suite World Wide Web (WWW)
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TCP/IP
TCP/IP - a group, or suite, of networking protocols used to connect computers on the Internet
Two main protocols in the suite are: TCP provides transport functions, ensuring,
among other things, that the amount of data received is the same as the amount transmitted
The IP part of TCP/IP provides the addressing and routing mechanism
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The TCP/IP suite of applications
File Transfer Protocol (FTP) - allows files to be downloaded off or uploaded onto a network
Simple Mail Transfer Protocol (SMTP) - TCP/IP’s own messaging system for e-mail
Telnet protocol - provides terminal emulation Hypertext Transfer Protocol (HTTP) - allows Web
browsers and servers to send and receive Web pages
Simple Network Management Protocol (SNTP) - allows the management of networked nodes to be managed from a single point
The TCP/IP Protocol Suite
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World Wide Web
The World Wide Web is a client-server environment
Information is managed through Web sites on computers called Web servers
Accessing Web sites is done through the use of client software (i.e., a browser) and the Internet’s HTTP
Computers and Web sites on the Internet are linked through documents called Web pages written in HTML
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Intranet vs. Extranet
Intranet – an internalized portion of the Internet, protected from outside access, that allows an organization to provide access to information and application software to only its employees
Extranet - a private network that uses the Internet protocol and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses
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Virtual Private Network (VPN)
VPN - a private WAN that uses the Internet as a low-cost WAN backbone to transport data between two or more geographically separate sites
Advantages that a VPN has over a dedicated-line WAN: The cost of implementation No need to lay cable or lease dedicated lines between
the remote sites needing to connect Businesses can network remote offices into one large
WAN and provide access to the Internet
Intranet, Extranet, and VPN Technologies
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