Using MIS 2e Chapter 6: Data Communications Appendix: How the Internet Works David Kroenke

Using MIS 2eChapter 6: Data CommunicationsAppendix: How the Internet Works David Kroenke This presentation has been modified from the original and should be downloaded from the Course Documents area in Blackboard

Study Questions (Chapter 6) • Q1 – What is a computer network? • Q2 – What are the components of a LAN? • Q3 – What are the alternatives for a WAN? • Q4 – How does encryption work? • Q5 – What is the purpose of a firewall? • Reflection Guide: Human Networks Matter More Chapter 6/Appendix 6: Data Communications/Internet

Q1 – What is a computer network? • A computer network is a collection of computers that communicate with one another over transmission lines. • Three basic types of networks are: • Local area networks (LANs) –connects computers that reside in a single geographic location on the premises of the company that operates the LAN. • Wide area networks (WANs) –connects computers at different geographic sites. WAN communication lines are owned by a third-party vendor. • Internet – a network of networks (the author defines an internet as a network of networks and distinguishes between internets and the Internet) • The networks that comprise the Internet use a large variety of communication methods and conventions, and data must flow seamlessly across them. This is accomplished via communications protocols. Chapter 6/Appendix 6: Data Communications/Internet

Q2 – What are the components of a LAN? • A local area network (LAN) is a group of computers connected together on a single company site. • A switch is a special purpose computer that receives and transmits messages on a LAN. • Each device on a LAN has a hardware component called a network interface card(NIC) or wireless network interface card (WNIC) connects the device’s circuitry to the cable. • Each NIC (or WNIC) has a unique identifier, which is called the (MAC) media access control address. • Communicating devices have two addresses: physical address (MAC) and an IP address (logical address). • Devices on a LAN are connected using either Unshielded, Twisted Pair (UTP) cable or optical fiber cables Chapter 6/Appendix 6: Data Communications/Internet

Q2 – What are the components of a LAN? Different protocols; e.g., 802.3 (also called Ethernet) or 802.11 (wireless) enable communication among devices on a LAN. The WNICs connect via an access point Chapter 6/Appendix 6: Data Communications/Internet

Q2 – What are the components of a LAN? • This figure shows how a typical LAN might be arranged in a multistory building. Notice the combination of switches, UTP cable, and optical fiber cable on each floor. • Communications speeds are expressed in bits, whereas memory sizes are expressed in bytes; also unlike memory, K and M imply 1,000 and 1,000,000 respectively as opposed to 210 and 220. Narrowband refers to speeds less than 56 kbps; Broadband implies speeds in excess of 256 kbps Chapter 6/Appendix 6: Data Communications/Internet

Q2 – What are the components of a LAN? Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN? • WANs connect computers located at physically separated sites by obtaining connection capabilities from a third-party, typically an Internet Service Provider (ISP). The network may be created using: • Leased lines from telecommunication companies; the number of lines increases dramatically as new sites are added; beneficial when high volume of traffic occurs between fixed locations • Public switched network (PSDN), a network of computers and leased lines that is developed and maintained by a vendor that leases time on the network to other organizations; the organization pays for the time it uses • Virtual private network (VPN) use the Internet to create the appearance of private point-to-point connections. VPN software encrypts the messages to ensure security; offers the benefit of point-to-point leased lines while enabling remote access Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN (Connecting a PC)? • Connecting personal computers to an ISP requires that digitalsignals coming out of the computer are converted to analogsignals and vice versa. Modems are used to convert the signals back and forth as shown in the figure below. Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN (Types of Modems)? • A dial-up modem uses telephone lines and a Point-to-Point Protocol (PPP) to connect a personal computer to an ISP. • You dial the number for your ISP and connect • The maximum speed is 56 kbps • A DSL (digital subscriber line) modem operates on the same lines as voice telephones • The signals do not interfere with voice telephone service. • They provide much faster transmission speeds than dial up • They always maintain a connection. • May be symmetric or asymmetric (same or different upload and download speeds) • A cable modem provides high-speed data transmission using cable television lines. • Transmission speeds vary based on the number of network users • A wireless modem connects to a wireless network instead of to the telephone system. When you connect with a wireless modem, you are attached directly to your wireless ISP (Internet Service Provider) Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN (Leased Lines)? • Organizations can use networks of leased lines from telecommunications companies to connect computers located at geographically distributed sites as this figure shows. • Only predefined sites can use the leased lines. • These lines provide low-cost connections if the amount of traffic warrants it. Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN (PSDN)? • A public switched data network (PSDN) is developed and maintained by a vendor who leases network time to other organizations. • Each user site must lease a line on a PSDN. The line connection location is called a Point of Presence (POP). • PSDNs are less costly and require less management than leased lines. Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the alternatives for a WAN (VPNs)? • Virtual Private Networks (VPNs) create the appearance of private point-to-point connections by using tunnels to create virtual, private pathways over the Internet; i.e., a VPN appears to be a direct connection between two sites as shown in this figure. • Software encrypts data as they pass through the VPN, then decodes them when the user receives a message. Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does encryption work? • Encryption is the process of transforming clear text into coded, unintelligible text for secure storage or communication. • Consider a simple encryption scheme where each letter is transposed by a constant (known as the key) • “Go Canes” becomes “Hp Dboft” (using key of 1) • “Go Canes” becomes “Iq Ecpgu” (using key of 2) • In this example: • Only 25 keys are possible which is too limited • This a symmetric key because the same key is used to encrypt and decrypt a message. Both sender and recipient must keep the key secret. • In practice: • Web browsers use 2128 possible keys (39-digit number) • Two different keys are used to encrypt and decrypt a message (an asymmetric key). The public key is freely distributed; the private key is kept secret Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does encryption work? Most secure communication over the Internet uses a protocol called HTTPS. With HTTPS, data are encrypted using a protocol called the Secure Socket Layer/Transport Layer Security (SSL/TLS). Chapter 6/Appendix 6: Data Communications/Internet

Q5 – What is the purpose of a firewall? • A firewall is a computing device that prevents unauthorized network access. It can be a special-purpose computer or a program on a general-purpose computer or on a router • Organizations normally use multiple firewalls (next slide). Chapter 6/Appendix 6: Data Communications/Internet

Q5 – What is the purpose of a firewall (multiple firewalls)? • A perimeter firewall sits outside the organization network; it is the first device that Internet traffic encounters. • A packet-filtering firewall examines each packet and determines whether to let the packet pass. • Packet-filtering firewalls can prohibit outsiders from starting a session with any user behind the firewall. • They can also disallow traffic from particular sites, such as known hacker addresses. • They can also prohibit traffic from legitimate, but unwanted addresses, such as competitors’ computers. • Firewalls can filter outbound traffic as well. • Many organizations employ internal firewalls inside the organizational network in addition to the perimeter firewall. The internal firewall protects the LAN Chapter 6/Appendix 6: Data Communications/Internet

Reflection Guide–Human Networks Matter More • The Hungarian writer, Frigyes Karinthy, came up with the idea that everyone on earth is connected to everyone else by five or six people. • Suppose you want to meet your university’s president. • The president has a secretary who acts as a gatekeeper. • If you walk up to that secretary and say, “I’d like a half hour with President Jones,” you’re likely to be palmed off to some other university administrator. What else can you do? • Most successful professionals consistently build personal human networks. • They meet people at professional and social situations, collect and pass out cards, and engage in pleasant conversation (all part of a social protocol) to expand their networks. • Who do you interact with at a company function, people or your department or people in another department? Chapter 6/Appendix 6: Data Communications/Internet

Study Questions (Appendix Chapter 6) • Q1 – How does email travel? • Ethics Guide: Sending Personal e-mail at work? • Q2 – What is a communications protocol? • Q3 – What are the functions of the five TCP/IP—OSI layers? • Q4 – How does the Internet work? • Q4a – How is the Web different from the Internet? • Q4b – How do you create a Web site? • Q5 – How does www.prenhall.com become 165.193.123.253? Chapter 6/Appendix 6: Data Communications/Internet

Q1 – How does email travel? You are on vacation in Hawaii and you want to send a photograph to your friend at work in the snow-bound Midwest. You click send and the picture arrives a minute later. You take it for granted, but “a techno-miracle” has occurred You have a Dell, your friend has a Mac, and you use different e-mail programs. The LAN in your hotel uses wires, but the LAN in your friend’s company is wireless. Your message has to travel via the Internet by underwater cable or satellite, but it gets there. Amazing! Should your friend give you his/her e-mail address at work? Chapter 6/Appendix 6: Data Communications/Internet

Ethics Guide: Sending/Receiving personal e-mail at Work • Sending/receiving personal e-mail from work generally takes only a few minutes and consumes little of the company’s resources. Is it OK to send personal e-mail? • What if you send a picture (or other large file) to your friend? If you send 10 pictures to 100 friends? Where do you draw the line? • What is the greater cost to the company; its resources or your time? Is there a problem? • Is the activity illegal? • Is the activity against company policy? • Is the activity unethical? • Is the activity smart? Chapter 6/Appendix 6: Data Communications/Internet

Q2 – What is a communications protocol? • A protocol is a standard means for coordinating an activity between two or more entities. • A communications protocol is a means for coordinating activity between two or more communicating computers. • Two machines must agree on the protocol to use, and they must follow that protocol as they send messages back and forth. • An architecture is an arrangement of protocol layers in which each layer accomplishes a specific task • The most commonly used architecture is comprised of five levels and is known as TCP/IP-OSI architecture. • A program is product that implements a protocol • Internet Explorer and Netscape are programs that implement the HTTP protocol at the top level of the TCP/IP-OSI architecture Chapter 6/Appendix 6: Data Communications/Internet

Q3 – What are the functions of the five TCP/IP—OSI layers? Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does the Internet work (Overview)? • The Post Office is a good analogy of how the Internet works (Ed Krol in the Whole Internet, O’Reilly and Associates, 1992) • You drop a letter into a mailbox where it is picked up with other letters and delivered to local post office • The letters are sorted and sent to another post office that is closer to the destination • The process is repeated until the letter is eventually picked up by the mail carrier at the other end and delivered to the local destination • Each postal substation considers all of the routes available and makes the best possible decision according to the prevailing conditions • All that matters is the beginning and ending address; i.e., the path may change the next time a letter is mailed Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does the Internet work? All that matters is the beginning and ending address Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does the Internet work (TCP/IP)? • Continue the Post Office analogy, but this time we are mailing a book, not a letter. The Post Office (for whatever reason) does not accept large packages and thus we have to rip the pages out of the book and send them separately • Each page is placed in its own envelope and each envelope (packet) is sent separately into the postal system • Each packet may travel a different route, but all packets are assembled on the other end and then delivered • This may seem complicated, but it is actually quite clever: • Individual packets take turns using the connection medium so that large packages (books) do not monopolize traffic • Each packet is checked for accuracy individually; if an error is found only the individual packet has to be resent • All that matters is the starting and ending address; the path of individual packets may change the next time a letter is mailed Chapter 6/Appendix 6: Data Communications/Internet

D D E F D E 2 The router reads the IP addresses of individual packets and routes them to the destination; e.g. Network 2 and Computer D E D E F D 1 3 TCP on Computer D checks the accuracy of individual packets as they are received, checks for missing packets, then reassembles the message TCP (Transmission Control Protocol) on Computer A breaks message into packetsIP (Internet Protocol) adds the source and destination address to each packet Q4 – How does the Internet work (Packet Switching)? Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does the Internet work? (Acronyms)? • HTTP (Hyper Text Transfer Protocol) the protocol that is used to transmit Web documents • HTTPS – Secure protocol for confidential transactions; data is encrypted prior to being sent over the Internet • HTML – The main language in which Web documents are displayed; uses codes to specify how the content should appear to the user • URL (Uniform Resource Locator) – the address of a document on the Web • Web Browser – A software program used to locate and display Web pages; e.g., Netscape or Internet Explorer • IP address – a series of dotted decimals that identifies a unique device on a network Chapter 6/Appendix 6: Data Communications/Internet

Q4 – How does the Internet work? (Internet versus the Web) • The Internet is a network of networks • Connects millions of computers in a global network where any computer can communicate with any other computer, as long as both have an Internet connection and follow Internet protocols • Supports multiple protocols and applications including e-mail, news groups, instant messaging, HTTP, and FTP • Originally a project of the US government and ARPANet (1969) • The Web is a subset of the Internet which consists of sites that process the HTTP protocol • Uses HTTP and Web browsers to access Web pages linked together by hyperlinks • Created by Tim Berners Lee of CERN (1991) • The Internet is about computers whereas the Web is about documents. The Web makes the Internet more interesting, but the Internet makes the Web possible Chapter 6/Appendix 6: Data Communications/Internet

Q4a – How do you create a Web site (Obtain a Domain Name)? Register.com enables you to search for the domain name (bobsgolfclubs.com) and offers alternatives Whois.com shows the owner of the domain name and is useful if the site does not yet exist; i.e., you can buy it Chapter 6/Appendix 6: Data Communications/Internet

Q4a – How do you create a Web site? • Once you register a domain name, you will be contacted by multiple developers seeking to create and/or host your Web site. • Easiest initially to have the same company do both • The cost can vary from a few hundred dollars to many thousands, depending on the nature of the site. • Four distinct steps – create, host, maintain, and attract • Create the site • Determine the complexity of the site; the more complex, the more expensive. Complexity can go from merely displaying information, to downloading documents, to simple security (log-in), to e-commerce • Navigation (depth of links; horizontal versus vertical links) • Determine a visual design; a simple template is inexpensive whereas custom design adds significant Chapter 6/Appendix 6: Data Communications/Internet

Q4a – How do you create a Web site (continued)? • Host the site • After the site is created you need a company to host the site (i.e., provide a Web server) for you. The site should be scalable; i.e., it should be built in such as way that you can simply add more servers as traffic increases • Maintain the site • You want control of the content (at least initially); i.e., you should be the one to add/modify content (e.g., the special of the month) • Attract visitors to the site • This is an entirely different issue and requires a marketing campaign in conjunction with various search engines to direct users to your site Chapter 6/Appendix 6: Data Communications/Internet

Q5 – How does www.prenhall.com become 165.193.123.253? • The domain name system (DNS) converts user-friendly names into their IP addresses. Any registered valid name is a domain name. • Every domain name must be unique. • A non-profit agency (ICANN, Internet Corporation for Assigned Names and Numbers) administers the registration of domain names. • The top-level domain (TLD) refers to the last letters in a domain name; e.g., com, edu, and gov • Converting a domain name into an IP address is called Domain Name Resolution • www.prenhall.com = 165.193.123.253 • Domain name resolvers are computers that store the correspondence of domain names and IP addresses. • Root servers maintain lists of IP addresses of servers that resolve each type of TLD. • Each Web address is called a Uniform resource locator (URL); e.g., http://www.prenhall.com is the URL for Prentice Hall. • The URL may contain additional information about the document or folder where it is located; e.g., http://www.prenhall.com/kroenke Chapter 6/Appendix 6: Data Communications/Internet

Q5 – How does www.prenhall.com become 165.193.123.253? (Top Level Domains 2005) Chapter 6/Appendix 6: Data Communications/Internet

www.warriorsofthe.net Chapter 6/Appendix 6: Data Communications/Internet

Summary • A computer network is a collection of computers that communicate with one another over transmission lines. • Three types of computer networks are: LANs, WANs, and the Internet. • A protocol is a set of rules for accomplishing the functions of a particular layer. • An architecture is an arrangement of protocol layers; The most commonly used architecture is comprised of five levels and is known as TCP/IP-OSI architecture • The Internet functions conceptually the same way as the post office; i.e., all that matters is the ending address in sending a message across the network. Chapter 6/Appendix 6: Data Communications/Internet

Summary (Continued) • The Web is a subset of the Internet which consists of sites that process the HTTP protocol • The domain name system (DNS) converts user-friendly names into their IP addresses. You can apply for your own domain name using Register.com or a host of similar sites • Four distinct tasks associated with establishing a Web site (Create, Host, Maintain, and Attract Customers) • Encryption is the process of transforming clear text into coded, unintelligible text for secure storage or communication. An asymmetric approach is used with two keys, one public and one private Chapter 6/Appendix 6: Data Communications/Internet

Review: Select the appropriate term for each item HTML – Architecture – HTTP – HTTPS – Protocol – Browser – World Wide Web – IP address – Router – Ethernet – Berners-Lee • Subset of the Internet World Wide Web • Software application used to display Web pagesBrowser • Arrangement of protocol layersArchitecture • He invented the WebBerners-Lee • The language of the WebHTML • Special purpose computer that implements the IP protocol (the basic building block of the Internet)Router • Popular protocol for LANEthernet • Series of dotted decimals to identify a device IPAddress • An agreed upon format for transferring data between computersProtocol • Protocol used to transmit Web documentsHTTP • A secure Internet protocolHTTPS Chapter 6/Appendix 6: Data Communications/Internet

Using MIS 2e Chapter 6: Data Communications Appendix: How the Internet Works David Kroenke