networking.pdf

Chapter 06: Computer Networks Stair, Reynolds and Chesney: Principles of Business Information Systems, Fourth edition (9781473774605) © Cengage Learning 2021  Principles Effective communications are essential to organizational succes...

Chapter 06: Computer Networks Stair, Reynolds and Chesney: Principles of Business Information Systems, Fourth edition (9781473774605) © Cengage Learning 2021  Principles Effective communications are essential to organizational success Communications technology lets more people send and receive all forms of information over great distances The Internet is like many other technologies – it provides a wide range of services, some of which are effective and practical for use today, others are still evolving, and still others will fade away from lack of use Because the Internet and the World Wide Web are becoming more universally used and accepted for business use, management, service and speed, privacy, and security issues must continually be addressed and resolved For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Telecommunications The electronic transmission of signals for communications, by such means as telephone, radio, and television Telecommunications impacts businesses greatly because it lessens the barriers of time and distance As networks are connected with one another and transmit information more freely, a competitive marketplace demands excellent quality and service from all organizations For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  A general model of telecommunications (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  A general model of telecommunications (2) A sending unit such as a person, a computer system, a terminal, or another device, sends the message signal to a telecommunications device The telecommunications device may process the signal, such as convert it into a different form or from one type to another The telecommunications device then sends the signal through a medium. A telecommunications medium is any material substance that carries an electronic signal to support communications between a sending and receiving device Another telecommunications device connected to the receiving computer (6) receives the signal The process can be reversed, and the receiving unit can send another message to the original sending unit For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Synchronous & asynchronous communication Communication can occur synchronously or asynchronously With synchronous communication, the receiver gets the message almost instantaneously, when it is sent. Examples are a phone call, and instant messaging services With asynchronous communication there is a measurable delay between the sending and receiving of the message, sometimes hours or even days. Examples are sending a letter through the post office and e-mail Both types of communications are important in business For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Types of Guided Transmission Media a) c) b) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Telecommunication media types Guided transmission (using a solid medium): Twisted-pair wire Coaxial cable Fiber-optic cable Broadband over power lines For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Telecommunication media types For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Wireless Transmission Media Types Wireless transmission: Microwave Transmission 5G Wireless Communication Wi-Fi Near Field Communication Bluetooth Ultra wideband Infrared Transmission For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Microwave Transmission (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Microwave Transmission (2) » Microwave is a high-frequency (300 MHz–300 GHz) signal sent through the air » Terrestrial (Earth-bound) microwaves are transmitted by line-of-sight devices, so that the line of sight between the transmitter and receiver must be unobstructed » Microwave signals can carry thousands of channels at the same time For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Satellite Transmission (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Satellite Transmission (2) » A very small aperture terminal (VSAT) is a two- way satellite ground station with a dish antenna smaller than three meters in diameter. » Many retail chains employ this technology to support point-of-sale transactions, including credit cards. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Wireless Communication » 1G (first generation) - analogue communications » 2G (second generation) - fully digital networks » 3G (third generation) - wireless communication supports voice and broadband data communications in a mobile environment at speeds of 2–4 Mbps. – Additional capabilities include mobile video, ecommerce, location-based services, gaming and music. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  4G Wireless Communication » The International Telecommunications Union (ITU) has defined 4G as a network that has meaningful improvement over 3G. » 4G broadband mobile wireless is delivering enhanced versions of multimedia, smooth video streaming, universal access, portability across all types of device and, eventually, worldwide roaming. » 4G delivers access speeds in the range 5–20 Mbps, ten times the speed of 3G. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  5G Wireless Communication 5G is the 5th generation mobile network 5G enables a new kind of network that is designed to connect virtually everyone and everything together including machines, objects, and devices 5G deployments arguably started in 2018 in the USA 5G offer faster data speeds than LTE Supports more devices and users on the same network 5G can handle more data traffic without congestion or degradation For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Comparison of 5 Generations For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning WIFI (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  WIFI (2) WiFi - A medium-range wireless telecommunications technology brand owned by the Wi-Fi Alliance. A wireless access point (WAP) receives the signal, decodes it and sends the information to the Internet over a wired connection. When receiving data, the wireless access point takes the information from the Internet, translates it into a radio signal and sends it to the device’s wireless adapter For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Near Field Communication Near field communication (NFC) – a very short range wireless connectivity technology designed for consumer electronics, smartphones and credit cards. Once two NFC-enabled devices are a few centimetres apart, they exchange communications parameters and passwords to enable Bluetooth or other wireless communications between the devices. Because only two devices participate, NFC establishes a peer-to-peer network. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Bluetooth Bluetooth is a wireless communications specification that describes how smartphones, computers, printers and other electronic devices can be interconnected over distances of a few meters at a rate of about 2 Mbps. One important application of Bluetooth is in hands free use of mobile phones when driving, using a Bluetooth headset to connect to a phone. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Ultra Wideband Ultra wideband (UWB) communications involves the transmission of extremely short electromagnetic pulses lasting just 50 to 1000 picoseconds. UWB offers several advantages over other communications means: – a high throughput rate, – the ability to transmit virtually undetected and impervious to interception or jamming, and – a lack of interference with current communications services. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Infrared Transmission Infrared sends signals through the air via light waves at a frequency of 300 GHz and above. Infrared transmission requires line-of-sight transmission and short distances – under a few hundred metres. Infrared transmission can be used to connect a display screen, a printer and a mouse to a computer, meaning there are no wires to clutter up the desk. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Telecommunications Hardware Modems Multiplexer Front end processor Private branch exchange Switches, bridges, routers and gateways For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Modems (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Modems (2) Analogue signal - a variable signal continuous in both time and amplitude so that any small fluctuations in the signal are meaningful. Digital signal - a signal that represents bits. Modulation - translates data from digital to analogue Demodulation - translates data from analogue to digital. Modem – a telecommunications hardware device that converts (modulates and demodulates) communications signals so they can be transmitted over the communication mediaFor use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Multiplexers (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Multiplexers (2) A multiplexer is a device that: – encodes data from two or more data sources onto a single communications channel, – thus reducing the number of communications channels needed and – therefore lowering telecommunications cost For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Front-end Processors Front-end processors are special-purpose computers that manage communications to and from a computer system serving hundreds or even thousands of users. They poll user devices to see if they have messages to send and facilitate efficient, error-free communications. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Private Branch Exchange A private branch exchange (PBX) is a telephone switching exchange that serves a single organization. It enables users to share a certain number of outside lines (trunk lines) to make telephone calls to people outside the organization. A PBX also enables the routing of calls between individuals within the organizations. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Switches, Bridges, Routers And Gateways A switch uses the physical device address in each incoming message on the network to determine to which output port it should forward the message to reach another device on the same network. A bridge connects one local area network (LAN) to another LAN that uses the same telecommunications protocol. A router forwards data packets across two or more distinct networks towards their destinations through a process known as ‘routing’. A gateway is a network device that serves as an For use with Principles of Business Information Systems, 4e entrance to another network. by Stair, Reynolds & Chesney © 2021 Cengage Learning Router vs. Modem For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Networks and distributed processing A computer network consists of communications media, devices, and software needed to connect two or more computer systems or devices The computers and devices on the networks are called "network nodes" Nodes can share data, information, and processing jobs Organizations can use networks to share hardware, programs, and databases Increasingly, businesses are linking computers in networks to streamline work processes and allow employees to collaborate on projects and grow into an agile, powerful, and creative organization Networks enable geographically separated workgroups to share information, which fosters teamwork, innovative ideas, and new business strategies For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Network types Personal Area Network (PAN) Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) International networks Mesh networking For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Network Types (2) A personal area network (PAN) is a wireless network that connects information technology devices within a range of ten metres or so. A local area network (LAN) is a network that connects computer systems and devices within a small area, such as an office, home or several floors in a building. A metropolitan area network (MAN) is a telecommunications network that connects users and their computers in a geographical area that For use with Principles of Business Information Systems, 4e spans a campus or city. by Stair, Reynolds & Chesney © 2021 Cengage Learning  Network Types (3) A wide area network (WAN) is a telecommunications network that connects large geographic regions. Mesh networking is a way to route communications between network nodes (computers or other devices) by allowing for continuous connections and reconfiguration around blocked paths by ‘hopping’ from node to node until a connection can be established. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Network Types (4) Partial Mesh Network For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Centralized vs. decentralized processing With centralized processing, all processing occurs in a single location or facility. This approach offers the highest degree of control because a single centrally managed computer performs all data processing With decentralized processing, processing devices are placed at various remote locations. Each computer system is isolated and does not communicate with another system One benefit of distributed processing is that managers can allocate data to the locations that can process it most efficiently Distributed processing can also minimize the consequences of a catastrophic event at one location and ensure uninterrupted systems availability For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Client / Server Systems (1) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Client/Server Systems (2) In client/server architecture computers called servers are dedicated to special functions An application server holds the programs and data files for a particular application. An e-mail server sends and receives e-mails. A web server sends out web pages Each server is accessible by all computers on the network Servers can be computers of all sizes A client is any computer (often a user’s personal computer) that sends messages requesting services from the servers on the network For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Communications Software How does an application program request data from a disk drive on the network? Through a network operating system (NOS) The NOS is systems software that controls the computer systems and devices on a network and allows them to communicate with each other The NOS performs the same types of functions for the network as operating system software does for a computer, such as memory and task management and coordination of hardware Network Management Software – enables a manager on a networked desktop to monitor the use of individual computers and shared hardware (such as printers), scan viruses and ensure compliance with software licenses. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Securing Data Transmission (1) Encryption: the process of converting an original message into a form that can only be understood by the intended receiver Encryption key: a variable value that is applied (using an algorithm) to a set of unencrypted text to produce encrypted text (ciphertext) or to decrypt encrypted text For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Securing Data Transmission (2) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Securing Wireless Networks WEP and WPA are the two main approaches to securing wireless networks such as Wi-Fi and WiMAX. Most wireless networks now use the Wi-Fi Protected Access (WPA) security protocol that offers significantly improved protection over WEP. War driving involves hackers driving around with a laptop and antenna trying to detect insecure wireless access points. Once connected to such a network, the hacker can gather enough traffic to analyze and crack the encryption. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Virtual Private Networks Virtual private network (VPN) is a private network that uses a public network (usually the Internet) to connect multiple remote locations. A VPN provides network connectivity over a potentially long physical distance and thus can be considered a form of wide area network. VPNs support secure, encrypted connections between a company’s employees and remote users through a third-party service provider. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  The Internet The Internet is the world’s largest computer network Actually, it is a collection of interconnected networks, all freely exchanging information Nobody knows exactly how big the Internet is because it is a collection of separately run, smaller computer networks For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  How the Internet works (1) The Internet transmits data from one computer (called a host) to another If the receiving computer is on a network to which the first computer is directly connected, it can send the message directly If the receiving and sending computers are not directly connected, the sending computer relays the message to another computer which forwards it on A message can pass through a dozen or more forwarders on its way from one part of the Internet to another So if some nodes on the Internet are down, messages can still be sent via another route For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  How the Internet works (2) Internet Protocol (IP) is the set of conventions used to pass packets from one host to another. Transmission Control Protocol (TCP) is the best known, which operates at the transport layer. Each computer on the Internet has an assigned address called its uniform resource locator (URL), to identify it to other hosts. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Internet Applications (1) World Wide Web: often confused with the Internet, the World Wide Web was conceived of as a document- management system Numerous application have been added on, such as streaming video These are often referred to as Web 2.0 A Web browser is used to access and read Web pages which are usually written in HyperText Markup Language (HTML) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Internet Applications (2) E-mail Telnet: enables you to log on to other computers on the Internet to gain access to their publicly available files. Telnet is particularly useful for perusing library holdings and large databases. It is also called remote logon FTP: used to transfer files between computers Intranets and Extranets: an intranet is an internal company network built using Internet and World Wide Web standards and products. When selected externals (such as supplies) are given access to the intranet, it becomes an extranet For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  The World Wide Web (1) The World Wide Web was developed as an internal document-management system The World Wide Web (web, WWW, or W3) has grown to a collection of tens of thousands of independently owned computers that work together as one in an Internet service These computers, called web servers, are scattered all over the world and contain every imaginable type of data Because of its ability to handle multimedia objects, including linking multimedia objects distributed on web servers around the world, the web has become the most popular means of information access on the Internet today For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  The World Wide Web (2) The Web is a menu-based system that uses the client/server model It organizes Internet resources throughout the world into a series of menu pages, or screens, that appear on your computer Data can exist on the web as ASCII characters, word processing files, audio files, graphic and video images, or any other sort of data that can be stored in a computer file Hypertext allows the linking of certain words to other web pages, so users can click on them to access related material. This feature gives the web its name, as all information is linked together like a spider’s web For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  The World Wide Web (3) Hypertext is text used to connect web pages, allowing users to access information in whatever order they wish. Hypertext Markup Language (HTML) is the standard page description language for web pages. HTML tags is the code that let the web browser know how to format text – as a heading, as a list, or as body text – and whether images, sound or other elements should be inserted. Extensible Markup Language (XML) is the markup language for web documents containing structured information, including words, pictures and other elements. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Web Browsers Web browser is software that creates a unique, hypermedia-based menu on a computer screen, providing a graphical interface to the web. Hypermedia is an extension of hypertext where the data, including text, images, video and other media, on web pages is connected allowing users to access information in whatever order they wish. Applet is a small program embedded in web pages. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Search Engines and Web Research (1) Search engine is a web search tool. Most search engines, such as Google, are free. Companies pay a search engine for a sponsored link, which is usually displayed at the top of the list of links for an Internet search. Search engines that use keyword indexes produce an index of all the text on the sites they examine. Typically, the engine reads at least the first few hundred words on a page, including the title and any keywords or descriptions that the author has built into the page structure. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Search Engines and Web Research (2) You can use Google to search for images and video. You can search for geographic locations to get a view from the skies using satellites - Google Maps and Google Earth are examples You can use news organizations’ websites, such as the BBC’s (http://news.bbc.co.uk/), to access current information on a variety of topics. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Web Programming Languages Java is an object-oriented programming language from Sun Microsystems based on C++ that allows applets to be embedded within an HTML document. Unlike other programs, Java software can run on any type of computer. Programmers use Java to make web pages come alive, adding splashy graphics, animation and real- time updates. Hypertext Preprocessor, or PHP, is an open- source programming language. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Developing Web Content You can create a web page using one of the following approaches: a) write your code with a word processor and then use an HTML converter to convert the page into HTML format; b) use an HTML editor to write text (it will add HTML tags at the same time); c) edit an existing HTML template (with all the tags ready to use) to meet your needs; or d) use an ordinary text editor such as Notepad and type the start and end tags for each item. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Web services (1) Web services are standards and tools that streamline and simplify communication among websites for business and personal purposes. Internet companies, including Amazon, eBay and Google, are now using web services. Amazon. For example, has developed Amazon Web Services (AWS) to make the contents of its huge online catalogue available by other websites or software applications. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Web services (2) SOAP (Simple Object Access Protocol) is a specification that defines the XML format for messages. WSDL (Web Services Description Language) provides a way for a web service application to describe its interfaces in enough detail to allow a user to build a client application to talk to it. UDDI (Universal Discovery Description and Integration) is used to register web service applications with an Internet directory, so that potential users can easily find them andForcarry out transactions use with Principles of Business Information Systems, 4e over the web. by Stair, Reynolds & Chesney © 2021 Cengage Learning  Developing Web Content and Applications (1) Popular tools for creating web pages and managing websites include Adobe Dreamweaver, Microsoft Expression Web and the open source alternative. Such software allows users to create web pages using an interface similar to a word-processor. The software converts what the user types into HTML code and creates hyperlinks to connect the pages. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Email Email or electronic mail is a method of sending communications over computer networks. It is no longer limited to simple text messages. Email travels through the systems and networks that make up the Internet. Gateways can receive email messages from the Internet and deliver them to users on other networks. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Telnet and FTP Telnet is a terminal emulation protocol that enables you to log on to other computers on the Internet to gain access to their publicly available files. File Transfer Protocol (FTP) is a protocol that describes a file transfer process between a host and a remote computer. You can also use FTP to gain access to a wealth of free software on the Internet. FTP can be used to upload or download content to a website. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Cloud Computing (1) Cloud computing refers to a computing environment where software and storage are provided as an Internet service and accessed with a web browser. Apple Computer has developed a service called iCloud to allow users to store their music, photos and other information. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Cloud Computing (2) Public Cloud Computing – a service provider organization owns and manages the infrastructure) (including computing, network and storage devices) with cloud user organizations (called tenants) accessing slices of shared hardware resources via the Internet. Private Cloud Computing – is a single tenant cloud. Organizations that implement a private cloud do so because they are concerned that their data will not be secured in a public cloud. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  Intranets and Extranets (1) An intranet is an internal company network built using Internet and World Wide Web standards and products. An extranet is a network that links selected resources of the intranet of a company with its customers, suppliers or other business partners. Again, an extranet is built around web technologies. Security and performance concerns are different for an extranet than for a website or network-based intranet. User authentication and privacy are critical on an extranet so that information is protected. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning Intranets and Extranets (2) For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning  The Internet of Things (IoT) The Internet of Things is a network of physical objects or ‘things’ embedded with sensors, processors, software and network connectivity to enable them to exchange data with the manufacturer of the device, device operators and other connected devices Sensors are being installed in a variety of machines and products, ranging from home appliances to cars, clothing and grocery items – A sensor is a device that is capable of sensing something about its surroundings, such as pressure, temperature, humidity, pH level, motion, vibration or level of light. For use with Principles of Business Information Systems, 4e by Stair, Reynolds & Chesney © 2021 Cengage Learning