Chapter 4 Telecommunications the Internet Intranets and Extranets

Chapter 4 Telecommunications, the Internet, Intranets, and Extranets

An Overview of Telecommunications ü Telecommunications: the electronic transmission of signals for communications ü Telecommunications medium: anything that carries an electronic signal and interfaces between a sending device and a receiving device

Telecommunications System Components

Channel Bandwidth ü Telecommunications professionals consider the capacity of the communications path or channel when they recommend transmission media for a business ü Channel bandwidth: the rate at which data is exchanged over a communication channel ä Usually measured in bits per second (bps)

Types of Signals Analog signal ü Continuous waveform ü Passes through communications medium ü Used for voice communications Digital signal ü Discrete waveform -- Transmits data coded into two discrete states as 1 -bits and 0 -bits ü Used for data communications Modem ü Translates computer’s digital signals into analog and vice versa

Communications Media

Telecommunications Hardware Table 4. 3: Common Telecommunications Devices

Services ü Digital subscriber line (DSL): telecommunications service that delivers high-speed Internet access to homes and small businesses over the existing phone lines of the local telephone network ü All major long distance carriers offer wireless telecommunications services that enable you to place phone calls or access the Internet

Networks and Distributed Processing ü Computer network: the communications media, devices, and software needed to connect two or more computer systems and/or devices ü Network nodes: the computers and devices on the networks

Network Types ü Personal area network (PAN) ü Local area network (LAN) ü Metropolitan area network (MAN) ü Wide area network (WAN) ü International networks ü Mesh networking

Distributed Processing ü Centralized processing: all processing occurs in a single location or facility ü Decentralized processing: processing devices are placed at various remote locations ü Distributed processing: computers are placed at remote locations but connected to each other via a network

Client/Server Systems ü Client/Server system: multiple computer platforms are dedicated to special functions, such as database management, printing, communications, and program execution

Communications Software and Protocols ü Communications protocol: a set of rules that govern the exchange of information over a communications channel ü Protocols govern several levels of a telecommunications network, such as: ä Hardware device level ä Application program level Wireless communications protocols are still evolving as the industry matures

Communications Software ü Network operating system (NOS): systems software that controls the computer systems and devices on a network and allows them to communicate with each other ü Network-management software: software that a manager uses on a networked desktop ä Monitors the use of individual computers and shared hardware (such as printers) ä Scans for viruses ä Ensures compliance with software licenses

Use and Functioning of the Internet ü Internet: a collection of interconnected networks, all freely exchanging information ü ARPANET ä The ancestor of the Internet ä A project started by the U. S. Department of Defense (Do. D) in 1969 ü Internet Protocol (IP): communication standard that enables traffic to be routed from one network to another as needed

How the Internet Works ü Data is passed in chunks called ü The Internet transmits data packets from one computer (called a ü Transmission Control Protocol host) to another (TCP): widely used transport-layer ü If the receiving computer is on protocol that is used in combination with IP by most a network to which the first Internet applications computer is directly connected, ü Uniform Resource Locator (URL): it can send the message an assigned address on the directly Internet for each computer ü If the receiving computer is not on a network to which the sending computer is connected, the sending computer relays the message to another computer that can forward it

How the Internet Works ü Accessing the Internet ä Connect via LAN server ä Connect via Serial Line Internet Protocol (SLIP)/Point-to-Point Protocol (PPP) ä Connect via an online service ä Several other ways to connect ä Example: WAP

Internet Service Providers ü Internet service provider (ISP): any company that provides individuals or organizations with access to the Internet ü Most charge a monthly fee ü Many ISPs and online services offer broadband Internet access through digital subscriber lines (DSLs), cable, or satellite transmission

The World Wide Web ü The Web, WWW, or W 3 ü A menu-based system that uses the client/server model ü Organizes Internet resources throughout the world into a series of menu pages, or screens, that appear on your computer ü Hypermedia: tools that connect the data on Web pages, allowing users to access topics in whatever order they want ü Hypertext Markup Language (HTML): the standard page description language for Web pages ü HTML tags: codes that let the Web browser know how to format text - as a heading, as a list, or as body text - and whether images, sound, and other elements should be inserted

Web Browsers ü Web browser: software that creates a unique, hypermedia-based menu on a computer screen, providing a graphical interface to the Web ü The menu consists of graphics, titles, and text with hypertext links ü Popular Web browsers: Microsoft Internet Explorer, Netscape Navigator, Mozilla Firefox, Apple Computer’s Safari

Search Engines and Web Research ü Search engine: Web search tool ä Examples: Yahoo. com, Google. com ü Most search engines are free ü Searches can use words, such as AND and OR to refine the search ü Meta-search engine: submits keywords to several individual search engines and returns results from all these search engines

Internet Cell Phones and Handheld Computers ü Some cell phones can be connected to the Internet to: ä Search for information ä Buy products ä Chat with business associates and friends ü Handheld computers and other devices can be connected to the Internet using phone lines or wireless connections, such as Wi-Fi

Intranets and Extranets ü Intranet ä Internal corporate network built using Internet and World Wide Web standards and products ä Used by employees to gain access to corporate information ä Reduces need for paper ü Extranet ä A network based on Web technologies that links selected resources of a company’s intranet with its customers, suppliers, or other business partners ü Virtual private network (VPN): secure connection between two points across the Internet ü Tunneling: process by which VPNs transfer information by encapsulating traffic in IP packets over the Internet

Net Issues ü Management issues ä No centralized governing body controls the Internet ü Service and speed issues ä Web server computers can be overwhelmed by the amount of “hits” (requests for pages) ü Privacy, fraud, security, and unauthorized Internet sites