Data Communication David Kroenke Using MIS 3e Chapter 6

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-2 If you go into business for yourself, there’s an excellent chance you’ll have a problem just like Neil’s. How much do you really have to pay toward a network infrastructure? You’ll need the knowledge of this chapter to understand the conversations you’ll have to make that assessment. Of course, you can just rely on outside experts, but that probably doesn’t work in the 21st century. Many of your competitors will be able to ask and understand those questions—and use the money their knowledge saves them for other facilities they need, like locker rooms and parking lots. Or, what if youwork in productmanagementfor a large company? Does your product “talk” to some network? If not, could it? Should it? Does it require a LAN or a WAN? As stated mega-times already, data communication is nearly free today, generating exciting opportunities. This trend makes basic knowledge of this free resource even more important. Chapter Preview

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-3 To help you be prepared, we will discuss the overarching concepts of computer networks and related technology. We will greatly simplify the discussion, but, even still, this topic involves the interaction of dozens of equipment types, methods, and standards and a sea of terms and acronyms. To help you deal with this complexity, we divide this topic into a conceptually oriented chapter and a supplemental appendix with more details. In particular, this chapter defines three types of computer networks and discusses the components and alternatives for two of those types: local area networks (LANs) and wide area networks (WANs). It then explains, at a high level, how computer encryption works and finally describes firewalls, which are devices for protecting networks from unauthorized access and use. Chapter Preview (cont’d)

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-4 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-5 Computer network is a collection of computers that communicate with one another over a variety of transmission lines. Three basic types of networks: LAN, WAN, Internet (The Internet is discussed in Appendix 6A) (video)video What Is a Computer Network? Figure 6-1 Major Network Types

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-6 Additional characteristics of networks:  LAN communication lines reside on- premises, making it easier for a business to locate a network wherever it chooses.  WAN communication lines are owned by a third-party vendor. A business contracts with vendor to use its WAN lines.  Each type of network uses protocols which are sets of rules that two devices use to communicate with each other. What Is a Computer Network?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-7 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-8 Components are usually located within a half mile of each other. A switch is a special-purpose computer that receives and transmits messages to computers in the LAN. A network interface card (NIC) is a hardware component that connects each device’s circuitry to a cable allowing protocols to send data across the LAN. Most computers today include an NIC. What Are the Components of a LAN? Fig 6-2 Local Area Network (LAN)

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-9 Media access control (MAC) address serves as a unique identifier for each NIC on a LAN. Unshielded twisted pair (UTP) cables, shown on left, are one way to connect devices to a LAN. Optical fiber cables, shown on right, connect devices to a LAN using fiberglass wires to transmit signals which are light rays. Cladding contain the signals. Optical fiber carries more traffic than UTP cables. What Are the Components of a LAN? Fig 6-3 Unshielded Twisted Pair (UTP) CableFig 6-5 Optical Fiber Cable

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-10 What Are the Components of a LAN? Typical arrangement of switches in a multistory building

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-11 The IEEE, Institute for Electrical & Electronics Engineers, is a committee that creates and publishes protocols and standards used by virtually every network.IEEE IEEE 802.3, or Ethernet, protocol is used by all LAN devices. It specifies hardware characteristics and describes how messages are packaged and processed. Onboard NICs in new PCs support10/100/1000 Ethernet protocol which describes transmission rate speed. Communication speeds are expressed in bits like 1,000,000 for megabits. What Are the Components of a LAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-12 IEEE wireless protocol uses wireless NICs (WNIC) to connect devices to networks similar to how wired NICs operate. Figure depicts a combination of NICs and WNICs on a LAN. Access points (AP) use protocol to communicate with a switch and protocol to send and receive wireless traffic. What Are the Components of a LAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-13 Summary of LAN and WAN Networks

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-14 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-15 WANs connect computers located at physically separated sites by obtaining connection capabilities from a third-party, typically an Internet Service Provider (ISP). Three primary functions of an ISP are to: 1.Provide users with a legitimate Internet address 2.Serve as a gateway for users to connect to the Internet 3.Help pay for the Internet by collecting money from customers and using it to pay access fees and other charges What Are the Alternatives for a WAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-16 Connecting personal computers to an ISP requires that digital signals coming out of the computer are converted to analog signals. Analog signals coming into a personal computer must be converted to digital signals. Comparison of digital and analog signals. What Are the Alternatives for a WAN? Fig 6-8 Analog Versus Digital Signals

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-17 Fig 6-9 Personal Computer Internet Access What Are the Alternatives for a WAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-18 Dial-up modem uses regular telephone lines and a Point-to-Point Protocol (PPP) to connect a personal computer to an ISP.  Dial-up modem is considered narrowband because it uses transmission speeds less than 56 kbps. DSL modem shares a single communication line for a telephone and a personal computer. It’s much faster than a dial-up modem and allows a user to maintain a constant network connection with an ISP.  Asymmetric DSL, ADSL, provides different upload/download speeds.  Symmetrical DSL, SDSL, provides the same upload/download speeds. What Are the Alternatives for a WAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-19 Cable modem shares a single communication line for cable TV and a personal computer. It’s also faster than a dial-up modem and allows users to maintain a constant network connection.  Because cable modems use a neighborhood distribution center, transmission speeds vary based on the number of network users. DSL and cable modems are considered broadband because their transmission speeds exceed 256 kbps. What Are the Alternatives for a WAN?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-20 Leased lines from telecommunications companies to connect computers located at geographically distributed sites (see figure) Lines use a variety of access devices to connect to each site: What Are the Alternatives for a WAN? Switches and Routers— special-purpose computers that move network traffic from one node to another. Only predefined sites can use the leased lines. These lines provide low- cost connections if amount of traffic warrants it.

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-21 Fig 6-11 Transmission Line Types, Uses, and Speeds What Are the Alternatives for a WAN? Comparison of line types, uses, and speeds.

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-22 Public switched data network, PDSN, developed and maintained by a vendor who leases network time to other organizations.Public switched data network Each user site must lease a PDSN line connection called a Point of Presence (POP). What Are the Alternatives for a WAN? PDSNs are less costly, don’t require as much management involvement as leased lines. Uses three protocols: 1.Frame relay with speeds from 56 kbps to 40 Mbps 2.Asynchronous transfer mode (ATM) with speeds from 1 to 156 Mbps. 3.Ethernet with speeds from 10 to 40 Gpbs

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-23 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-24 Virtual Private Networks (VPNs) create the appearance of private point-to-point connections by using tunnels to create virtual, private pathways over the Internet.Virtual Private Networks Figure below shows connections a VPN uses. Why Do Organizations Use Virtual Private Networks? Fig 6-13 Remote Access Using VPN: Actual Connections

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-25 Fig 6-14 Remote Access Using VPN: Apparent Connection Why Do Organizations Use Virtual Private Networks? 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 making them more secure. Then, decodes when user receives them.

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-26 Fig 6-15 WAN Using VPN Why Do Organizations Use Virtual Private Networks? This figure shows how a WAN uses three different VPN tunnels to connect geographically separated users.

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-27 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-28 Encryption—process of transforming clear text into coded, unintelligible text for security reasons is called encryption. Used to make transmissions more secure across networks and between users and Web sites. Encryption algorithms use a key (number) to encode data in messages before sending and decode them when they reach their destination.Encryption algorithms  Symmetric encryption uses same key to encode and decode a message.  Asymmetric encryption uses a different key to encode than is used to decode a message. How Does Encryption Work?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-29 Public key/private key is a special version of asymmetric encryption mainly used on the Internet.  The public key encodes a message and is exchanged among users.public key  The private key decodes a message but is never exchanged among users.private key HTTPS is most secure protocol used on the Internet.  Secure Socket Layer (SSL), also known as Transport Layer Security (TLS), combines public key/private key with symmetric encryption to establish a secure exchange of data on a Web site.  Web sites using this type of security will have at the beginning of the URL. How Does Encryption Work?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-30 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-31 Firewall—a special-purpose computer or a program on a general-purpose computer or router that prevents unauthorized network access. What is the Purpose of a Firewall? Fig 6-17 Use of Multiple Firewalls Figure shows a perimeter firewall that sits outside the network and is first device incoming network traffic encounters. An internal firewall is located inside the network and protects the LAN.

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-32 Packet-filtering firewalls examine the source address, destination address, and other data in each incoming message and decides whether to let the message enter the network.Packet-filtering firewalls Packet-filtering firewalls prohibit outsiders from starting a session with users behind the firewall, disallow traffic from particular sites, and filter outbound traffic. Each incoming message is compared to an access control list (ACL). Firewall stops prohibited messages from entering the network.access control list Many ISPs provide generic firewalls for customers. Large organizations supplement generic firewalls with their own. Most home routers include firewalls, and Windows XP, Vista, and Windows 7 have built-in firewalls as well. Third parties such as Norton and Symantec also license firewall products. What is the Purpose of a Firewall?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-33 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall ? Q72020? Study Questions

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-34 ISPs will charge based on number of bits sent and received. Streamlined Sales Tax Project—more states will collect sales taxes on Internet purchases regardless of whether seller has physical presence in the state. Everything will be connected to everything, everywhere, and everything will be inter-connected (Microsoft Office Communicator). You’ll be receiving via phone (a voice will read it to you), and phone via (a voice-recognition system will type it). All messages, of whatever medium, will be stored in one location. Systems will provide presence, so you’ll know who is on the system, who is available, and who cannot currently be reached. Communications will be ubiquitous. 2020?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-35 You ed a very high-quality (nonpornographic) picture that was 6.2 megabytes in size to a friend. What’s the matter with this and a picture? Consider the resources consumed:  Your message, and picture, traveled over the Internet to OhioCompany’s ISP. Packets of the and picture were transmitted to OhioCompany’s router and then to its server.  It consumed processing cycles on the router and on the server computer. A copy of picture is stored on server until your friend deletes it.  Picture saved on company-owned PC. Entire computing infrastructure, from ISP to your friend’s desk, is owned, operated, and paid for by OhioCompany. Your friend reads his during his working hours. Ethics Guide: Personal at Work?

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-36 Nathan Myhrvold claimed that humans:  Cannot think exponentially  Think of fastest linear change and extrapolate from there Was writing about growth of magnetic storage Applies to growth of computer network phenomena Ubiquitous and cheap connectivity is growing exponentially  What are the threats and opportunities? Guide: Thinking Exponentially Is Not Possible, but…

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-37 Technology doesn’t drive people to do new things Social progress occurs in small, evolutionary, adaptive steps Technology may enable a capability, but people may not want it  People want to do what they are doing more easily.  They want to solve existing problems. Respond by hedging your bets The more time involved, the more potential for error Guide: Thinking Exponentially Is Not Possible, but…

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-38 Six degrees of separation  Social networks are crucial in connecting you to everyone in six degrees.  In general, people you know the least contribute the most to your network. Build personal social networks for success  Someone, somewhere, that you need to know or will need to know  Meet people at professional and social situations Pass out and collect business cards Converse to expand network Look for new channels Ethics Guide: Human Networks Matter More

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-39 Q1What is a computer network? Q2What are the components of a LAN? Q3What are the alternatives for a WAN? Q4Why do organizations use virtual private networks? Q5How does encryption work? Q6What is the purpose of a firewall? Q72020? Active Review

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-40 WiMax—a standards-based technology for wireless broadband access, alternative to cable and DSL Internet access (How WiMax works)How WiMax works Last-mile problem—getting broadband access into homes and small businesses WiMax Forum Certified TM systems to have capacity of 40 Mbps per channel, for fixed, nomadic, portable, and mobile applications IEEE and IEEE e wireless standards Clearwire and Craig McCaw Wireless Broadband Introduction (education) Case Study 6: Keeping Up with Wireless

Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall 6-41 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. Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall