Using MIS 3e Chapter 6A Appendix

Study Questions Using MIS 3e Chapter 6A Appendix How the Internet Works David Kroenke Q1: How does email travel? Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-3 Chapter Appendix Preview The chapter appendix discusses the third type of network, internets, and explains in particular how one such network the Internet works. Using the example of email from a hotel in Hawaii to a company in Ohio, the appendix explains the nature of layered protocols and describes how the Internet uses the TCP/IP OSI protocol architecture. The appendix also explains how the Internet transforms URLs such as pearsonhighered.com into globally unique logical addresses. You may be tempted to skip the appendix, and, if time is short, you may need to. However, the Internet is the foundation of 21st-century commerce, and knowing Internet components and their interactions is part of a business professional s literacy. Just as you need to know terms like LIFO and FIFO and understand what it means when marginal revenue equals marginal cost, so, too, you need to know what TCP/IP and related protocols are and how they are used. How Does Email Travel? Messages and attachments sent from your computer Broken down into pieces called packets Packets sent to LAN switch Routers determine the best way to move messages through Internet to destination Software at destination email server ensures all packets are received Requests missing packets to be resent Messages and attachments reassembled at recipient s email server and readied to be opened by recipient Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-2 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-4 1

How Email Travels What Is a Communications Protocol? Protocol Standardized means for coordinating activity between two or more entities Follows a sequence of ordered steps Communications protocol Means for coordinating activities between communicating computers Computers agree on protocol to use Broken down into layers based on category of task performed Divide and conquer concept Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-5 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-7 Q1: How does email travel? Study Questions Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Q1: How does email travel? Study Questions Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-6 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-8 2

What Are the Functions of the Five TCP/IP-OSI Layers? 1. Reference Model for Open Systems Interconnection (OSI) Seven layers Developed by International Organization for Standardization (ISO) 2. Transmission Control Program/Internet Protocol (TCP/IP) (video) Four layers Developed by the Internet Engineering Task Force (IETF) 3. TCP/IP-OSI architecture is a five-layer blend of OSI and TCP/IP. Layer 5: Protocols SMTP Simple Mail Transfer Protocol HTTP Hypertext Transfer Protocol FTP File Transfer Protocol Three important terms 1. Architecture arrangement of protocol layers in which each layer is given specific tasks to accomplish 2. Protocol a set of rules that accomplish tasks assigned to its layer 3. Program a specific computer product that implements a protocol (Example: browser) Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-9 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-11 CE10-11 TCP/IP-OSI Architecture Layer 4: Transmission Control Program (TCP) Email program (SMTP) interacts with TCP TCP operates at Layer 4 TCP Breaks email message and attachments into segments Attaches To/From addresses to each segment Ensures reliability that all segments are received Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-10 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-12 3

TCP/IP-OSI on Your Computer Layers 1 and 2 Handles basic computer connectivity Packages packets into frames Frames transmitted between programs, switches (SW1, SW3), internal routers (RH) shown in Figure CE10-1 Switches facilitate communication Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-13 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-15 Layer 3: Internet Protocol (IP) TCP interacts with Layer 3 protocols Purpose of IP: Route messages across an Internet Packages each segment into a packet Places IP data in front of TCP data on each packet Routers use IP data to decide where to send packets. Dozens of Internet routers involved in getting email message from Hawaii to Cincinnati. Q1: How does email travel? Study Questions Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-14 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-16 4

How Does the Internet Work? Each computer and device has two addresses: (1) physical address; (2) logical address. Layer 2 protocol programs use physical addresses or MAC addresses Layer 3 and 4 programs use logical addresses or IP addresses Public vs. Private IP Addresses Public IP address Used on Internet Assigned by ICANN (Internet Corporation for Assigned Names and Numbers) Each address is unique Private IP address Used within private networks Controlled by company operating network Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-17 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-19 Network Addresses: MAC and IP MAC addresses Physical addresses Implemented by programs that use Layer 2 protocols Each NIC card given an address by manufacturer Address only shared within network or segment IP addresses Logical addresses Written as series of dotted decimals 192.68.2.28 Not permanently associated with hardware device Can be reassigned as necessary Dynamic Host Configuration Protocol DHCP server computer or router that hosts DHCP program Program distributes temporary IP address to computers and devices on connecting to network Address loaned while computer connected to LAN When computer disconnected, IP address made available to others Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-18 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-20 5

Using TCP/IP-OSI Protocols Within the Hotel Hotel has private Web server IP address of hotel server (HS with address IP8) assigned by network administrator Router (RH with IP address IP9) is a DHCP server Guest computer signs into Web server Guest browser sends service request to hotel server TCP program breaks request into segments and adds data to each segment TCP programs hands segments to IP program for routing Using TCP/IP-OSI Protocols Within the Hotel IP program adds IP9 header and passed wrapped packet to an Ethernet program Ethernet program translates IP address into MAC address of device IP9 (Hotel router) Ethernet wraps packet into frame addressed to hotel router (RH) Sends packet through switch Since Ethernet program on your computer connected to switch S3 when you signed on, frame is relayed accordingly Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-21 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-23 Private IP Addresses at the Hawaii Hotel Communications Processing on the Switches Switch consults switch table Directs frame to router Ethernet unpacks frame, sends packet to IP Router consults routing table, sends packet one hop down network Ethernet determines MAC address needed Ethernet packages packet into frame addressed to appropriate MAC address Sends frame to switch S1 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-22 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-24 6

Communications Processing on the Router Routers Routing tables Contain data where to send packets Directs packet traffic on LAN and Internet Ethernet unpacks frames addressed to router RH as they arrive Sends packets to IP program on router IP changes packet destination to IP8 Ethernet matches IP8 to MAC address HS (hotel server), puts packets in frame with HS MAC address Sends frame to switch S1 Switches relay frame to hotel server (HS) Using TCP/IP-OSI Protocols over the Internet Network Address Translation LAN use private IP addresses Internet traffic uses public IP addresses Hotel s ISP assigns public IP address to hotel router (IPx) Router RH has two IP addresses Private one assigned by organization for local traffic Public one assigned by ISP for Internet traffic Network Address Translation (NAT) Process of changing public IP addresses into private addresses and reverse Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-25 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-27 Communications Processing on the Web Server At Web server HS: Ethernet unpacks frame, sends packet to IP program. IP program strips off IP header, sends packet to TCP program. TCP sees packet is one of two. TCP sends receipt acknowledgement back to email sender. TCP waits for second packet. When packet two arrives, TCP sends complete request (contained in both packets) to Web server for HTTP protocol processing. Your Email!: How Does It Get to CarterK@OhioCompany.com? You enter email address of recipient Email program works at application layer Implements SMTP to send email Uses domain name system to get public IP address Email message sent to router Sends message to TCP Breaks into segments, placed in packets Sent to router RH Packets sent to Ethernet program Placed in frame Sent to switch S3, then S1, and sent to router Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-26 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-28 7

Accessing the (Private) Hotel Web Server Domain Name Resolution Uniform Resource Locator (URL) User-friendly document Web address For example: www.pearsonhighered.com/kroenke Domain name resolution Process of converting a domain name into a public IP address Starts from the TLD and works to the left across URL ICANN manages 13 special computers called root servers distributed around the world. Each root server maintains a list of IP addresses of servers that resolve each type of TLD. Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-29 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-31 Your Email!: How Does It Get to CarterK@OhioCompany.com? Packets of email and picture arrive at router. Implements NAT Replaces private IP address with public IP address Router consults table, sends packets to router R2 (San Francisco). Packets travel router to router until they reach OhioCompany router. Segments unpacked from packets, sent to TCP program. Program waits for all segments, then sends to program that implements SMTP. Program operates at Layer 5, puts message in mailbox of CarterK. Domain Name Resolution Domain name resolvers Thousands of computers at academic institutions, large companies, government organizations Cache domain names and IP addresses locally Save time by not needing to go through entire resolution process somewhere else Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-30 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-32 8

Hawaii Hotel to OhioCompany LAN via Internet Figure CE7-7 How Does www.pearsonhighered.com Become 165.193.123.253? Domain name system (DNS) Converts user-friendly names into their IP address Domain name a registered, valid name Every DNS is unique in world Resolving the domain name Process of changing a domain name into its IP address (Layer 5 application) Top-level domain (TLD) Examples.com;.org;.edu;.gov Non-United States www.somewhere.uk Industry.aero Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-33 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-35 Q1: How does email travel? Study Questions Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Domain Name Registration ICANN International Corporation for Assigned Names and Numbers A nonprofit organization responsible for administering the registration of domain names. Does not register domain names itself; instead, it licenses other organizations to register names. ICANN is also responsible for managing the domain name resolution system. DNS (Domain Name System ) Converts user-friendly names into public IP address Resolves domain names Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-34 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-36 9

U.S. Top-Level Domains Domain Name Resolution Domain name resolution proceeds more quickly because there are thousands of computers called domain name resolvers that store domain names and IP addresses. These resolvers reside at ISPs, academic institutions, large companies, governmental organizations, and so forth. Resolvers convert a domain name into an IP address. Resolver stores, or caches, a domain name and IP address on a local file when someone on campus uses a domain name. Then, when someone else on campus uses same domain name, there is no need for the resolver to go through entire resolution process. Instead, resolver can supply the IP address from the local file. Curious to know your current IP address, go to http://www.whatis/myipaddress.com Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-37 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-39 Domain Name Resolution Uniform resource locator (URL) (pronounced U-R-L or Earl ) is a document s address on the Web. URLs begin with a domain name and followed by optional data that locates a document within that domain. Thus, in the URL www.pearsonhighered.com/kroenke, the domain name is www.pearsonhighered.com, and /kroenke is a directory within that domain. Domain name resolution is the process of converting a domain name into a public IP address. Process starts from the TLD and works to left across the URL As of 2009, ICANN manages 13 special computers called root servers that are distributed around the world. Each root server maintains a list of IP addresses of servers that resolve each type of TLD. VoIP and IPTV Voice over IP (VoIP, pronounced voyp ) uses the TCP/IP-OSI architecture to carry telephone voice conversations. With VoIP, voice conversations are stored as bits, broken into IP packets, and routed over the Internet. No separate telephone line is required; same connection that routes email, HTTP, and other data also carries voice conversations. A problem occurs when a user who is connected to the Internet wants to dial someone who has only regular telephone access, or, equivalently, when someone who has a regular telephone wants to call someone who has a VoIP connection. Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-38 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-40 10

VoIP and IPTV Companies, such as Skype, have solved this problem and offer subscribers unrestricted telephone access using VoIP. Skype is particularly economical for those who make frequent international calls. Some users complain quality of transmission is not as high as for regular telephone, but they use Skype anyway because cost savings are worth it. Internet Protocol Television (IPTV ) uses TCP/IP-OSI to transmit television and other video signals. Broadband connection is required. Device called a set-top box receives the IPTV signal and distributes it to multiple televisions or home entertainment centers. Some set-top devices provide VoIP, text chat, and other services as well (for example, Tornado M10 Media Center). Expect to see increased use of both VoIP and IPTV in years to come. Case Study 6A: A SOHO Network Administration Small, flat, black box is a DSL modem that is connected to a telephone line. DSL modem also connects to the silver, upright box with the small dark gray antenna. Silver box is a Microsoft wireless base station. Wireless base station, a marketing term Microsoft uses to soften the complexity of what s actually in gray box. Box contains an ethernet LAN switch, an 802.11g wireless access point, and a router. Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-41 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-43 Active Review Q1: How does email travel? Q2: What is a communications protocol? Q3: What are the functions of the five TCP/IP-OSI layers? Q4: How does the Internet work? Q5: How does www.pearsonhighered.com become 165.193.123.253? Case Study 6A: A SOHO Network Administration Notice several UTP cables that connect the wireless base station to computers and other devices on the LAN. A generic term for Microsoft s Wireless Base Station is device access router, the term you should use when you go shopping for one. Wireless Base Station also contains a small special-purpose computer that has firmware programs installed. These programs provide DHCP service as well as NAT. Programs for administration and for setting up wireless security. Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-42 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-44 11

Case Study 6A: A SOHO Network Administration Notice the printer (behind the tape dispenser). Printer has a small black box with a gray UTP cable and a small black power line going into it. Black box is an NIC that connects the printer to the LAN. This NIC is called a printer server, and it, too, has a special-purpose computer with firmware that allows for setting up and administering the printer server and printer. Structure of a SOHO Network Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-45 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-47 A SOHO Network All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-46 Copyright 2011 Pearson Education, Inc. Publishing as Prentice Hall 6A-48 12