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