TECHNOLOGY GUIDE 4TECHNOLOGY GUIDE 4

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Telecommunications, Networks, and the World Wide Web

Technology Guide OverviewTechnology Guide Overview

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AgendaAgendaTG4.1 The Telecommunications System

TG4.1.1 Definition and conceptsTG4.1.2 Communications processorsTG4.1.3 Communications media and channelsTG4.1.4 Transmission

TG4.2 Types of NetworksTG4.2.1 Local Area NetworksTG4.2.2 Wide Area NetworksTG4.2.3 Enterprise networking

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TG4.3 Network FundamentalsTG 4.3.1 NetworksTG 4.3.2 Types of Network ProcessingTG4.3.3 Client/Server computingTG4.3.4 Peer-to-Peer processing

TG4.4 The InternetTG4.4.1 Accessing the InternetTG4.4.2 The future of the Internet

TG4.5 The World Wide Web

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LEARNING OBJECTIVESLEARNING OBJECTIVES

1. Understand the basics of telecommunications systems including the main types of wired communications media and transmission technologies. TG4.1

2. Differentiate between local area network and wide area network. TG4.2

3. Describe the main network protocols and processing. TG4.3

4. Explain how the Internet works and how it can be accessed. TG4.4

5. Differentiate between the Internet and the World Wide Web. TG4.5

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TG4.1 The Telecommunications TG4.1 The Telecommunications SystemSystem

TG4.1.1 Definition and conceptsTG4.1.2 Communications processorsTG4.1.3 Communications media and channelsTG4.1.4 Transmission

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TG4.1.1 Definition and TG4.1.1 Definition and conceptsconceptsA telecommunications system consists of

hardware and software that transmit information from one location to another. These systems can transmit text, data, graphics, voice, documents, or full-motion video information. They transmit this information with two basic types of signals: analog and digital.

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Analog signals are continuous waves that transmit information by altering the characteristics of the waves. Analog signals have two parameters: amplitude and frequency.

Digital signals are discrete pulses that are either on or off, representing a series of bits (0s and 1s). This quality allows them to convey information in a binary form that can be clearly interpreted by computers.

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TG4.1.2 Communications TG4.1.2 Communications processorsprocessorsCommunications processors are hardware

devices that support data transmission and reception across a telecommunications system. These devices include◦ Modems◦ Multiplexers◦ Front-end processors

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Modems The function of a modem is to convert digital signals

to analog signals, a process called modulation, and analog signals to digital signals, a process called demodulation. Modems are used in pairs.

The modem at the sending end converts a computer’s digital information into analog signals for transmission over analog lines (for example, telephone lines).

At the receiving end, another modem converts the analog signal back into digital signals for the receiving computer.

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There are three types of modems: dial-up modems, DSL modems, and cable modems.

Dial-up modems have transmission speeds of up to 56 Kbps.

Cable modems are modems that operate over coaxial cable (for example, cable TV). They offer high-speed access to the Internet or corporate intranets.

DSL (digital subscriber line) modems operate on the same lines as voice telephones and dial-up modems, but DSL signals do not interfere with voice service. Also, DSL modems always maintain a connection, so an Internet connection is immediately available.

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Multiplexer and front-end processorA multiplexer is an electronic device that

allows a single communications channel to carry data transmissions simultaneously from many sources.

A front-end processor is a specialized computer manages all routing communications with peripheral devices.

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TG4.1.3 Communications media TG4.1.3 Communications media and channelsand channelsFor data to be communicated from one

location to another, some form of pathway or medium must be used. These pathways are called communications channels.

The communications channels are divided into two types of media: cable (twisted-pair wire, coaxial cable, and fibre optic cable) and broadcast (microwave, satellite, radio, and infrared).

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TG4.1.4 TransmissionTG4.1.4 Transmission

Transmission speedBandwidth refers to the range of frequencies

available in any communications channel. Narrowband channels typically provide low-

speed transmission speeds up to 64 Kbps, although some now reach speeds of up to 2 Mbps.

Broadband channels provide high-speed transmission rates ranging from 256 Kbps up to several terabits per second.

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Transmission technologies Integrated services digital network (ISDN)Digital subscriber lines (DSL)Asynchronous transfer mode (ATM)Synchronous optical network (SONET)T-Carrier system

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Integrated services digital network (ISDN) is an older international telephone standard for network access that uses existing telephone lines and allows users to transfer voice, video, image, and data simultaneously.

Digital subscriber lines (DSL) provide high-speed, digital data transmission from homes and businesses over existing telephone lines. Because the existing lines are analog and the transmission is digital, you need DSL modems.

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Asynchronous transfer mode (ATM) networks allow for almost unlimited bandwidth on demand. ATM currently requires fibre-optic cable, but it can transmit up to 2.5 gigabits per second. On the downside, ATM is more expensive than ISDN and DSL.

Synchronous optical network (SONET) is an interface standard for transporting digital signals over fibre optic lines that allows users to integrate transmissions from multiple vendors.

The T-carrier system is a digital transmission system that defines circuits that operate at different rates, all of which are multiples of the basic 64 Kbps used to transport a single voice call.

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TG4.2 Types of NetworksTG4.2 Types of Networks

TG4.2.1 Local Area NetworksTG4.2.2 Wide Area NetworksTG4.2.3 Enterprise networking

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TG4.2.1 Local Area NetworksTG4.2.1 Local Area Networks

A local area network (LAN) connects two or more devices in a limited geographical region, usually within the same building, so that every device on the network can communicate with every other device.

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TG4.2.2 Wide Area NetworksTG4.2.2 Wide Area Networks

When businesses have to transmit and receive data beyond the confines of the LAN, they use wide area networks. Wide area networks (WANs) are networks that cover large geographic areas. WANs typically connect multiple LANs.

One important type of WAN is the value-added network (VAN). VANs are private, data-only networks managed by outside third parties that provide telecommunication and computing services to multiple organizations. Many companies use VANs to avoid the expenses of creating and managing their own networks.

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TG4.2.3 Enterprise networkingTG4.2.3 Enterprise networking

Organizations today have multiple LANs and may have multiple WANs, which are interconnected to form an enterprise network.

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TG4.3 Network FundamentalsTG4.3 Network Fundamentals

Network protocols is a set of rules and procedures that govern transmission across a network is a protocol.

Ethernet TCP/IP

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The transmission control protocol/Internet protocol (TCP/IP) is the protocol of the Internet. TCP/ IP uses a suite of protocols, the main ones being the transmission control protocol (TCP) and the Internet protocol (IP).

The TCP performs three basic functions:

1. It manages the movement of packets (discussed next) between computers by establishing a connection between the computers,

2. It sequences the transfer of packets, and

3. It acknowledges the packets that have been transmitted. The Internet protocol (IP) is responsible for disassembling, delivering, and reassembling the data during transmission, a process we discuss next.

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TG4.3.2 Types of Network TG4.3.2 Types of Network ProcessingProcessing

TG4.3.2 Client/Server computingTG4.3.3 Peer-to-Peer processing

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TG4.3.3 Client/Server TG4.3.3 Client/Server computingcomputing Client/server computing links two or more computers

in an arrangement in which some machines (called servers) provide computing services for user PCs (called clients).

Usually, an organization does the bulk of its processing or application/data storage on suitably powerful servers that can be accessed by less powerful client machines.

The client requests applications, data, or processing from the server, which acts on these requests by “serving” the desired commodity.

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TG4.3.3 Peer-to-Peer TG4.3.3 Peer-to-Peer processingprocessingPeer-to-peer (P2P) processing is a type of

client/server distributed processing in which each computer acts as both a client and a server. Each computer can access (as assigned for security or integrity purposes) all files on all other computers.

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There are three basic types of peer-to-peer processing.

The first accesses unused CPU power among networked computers. One example is SETI@home

The second form of peer-to-peer is real-time, person-to-person collaboration, such as Google Talk.

The third peer-to-peer category is advanced search and file sharing. One example of this is BitTorrent.

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TG4.4 The InternetTG4.4 The Internet

The Internet (“the net”) is a global WAN that connects approximately one million organizational computer networks in more than 200 countries on all continents, including Antarctica, and features in the daily routine of almost 2 billion people. Participating computer systems, called nodes, include smart phones, PCs, LANs, databases, and mainframes.

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An intranet is a network designed to serve the internal informational needs of a single organization.

An extranet connects parts of the intranets of different organizations and allows secure communications among business partners over the Internet using virtual private networks.

Darknets are private networks that run on the Internet but are open only to users who belong to the network. Typically, relatively few people or organizations have access to a darknet, due to security concerns.

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TG4.4.1 Accessing the InternetTG4.4.1 Accessing the Internet

Connecting via LAN Connecting via an on-line serviceConnecting via other means

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Connecting via an on-line serviceYou can access the Internet by opening an

account with an Internet service provider. An Internet service provider (ISP) is a company that offers Internet connections for a fee.

ISPs connect to one another through network access points (NAPs). NAPs are exchange points for Internet traffic. They determine how traffic is routed. NAPs are key components of the Internet backbone.

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TG4.4.2 The future of the TG4.4.2 The future of the InternetInternet In Canada, CANARIE develops and deploys advanced

network applications essential for national and international collaboration, such as remote medical diagnosis, digital libraries, distance education, on-line simulation, and virtual laboratories.

Internet2 is the equivalent of CANARIE in the United States and is designed to be fast, always on, everywhere, natural, intelligent, easy, and trusted. It allows the deployment of advanced applications such as remote medical diagnosis, digital libraries, distance education, on-line simulation, and virtual laboratories. Internet2 is not a separate physical network from the Internet.

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TG4.5 The World Wide WebTG4.5 The World Wide Web

The World Wide Web (the Web, WWW, or W3) is a system of universally accepted standards for storing, retrieving, formatting, and displaying information via a client/server architecture.

The Web handles all types of digital information, including text, hypermedia, graphics, and sound. It uses graphical user interfaces, so it is very easy to navigate.

To access a website, the user must specify a uniform resource locator (URL), which points to the address of a specific resource on the Web.

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