Ethernet Networking- P1

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Ethernet Networking- P1:One of the biggest problems when discussing networking is knowing where to start. The subject of computer networks is one of those areas for which you have to "know everything to do anything." Usually, the easiest way to ease into the topic is to begin with some basic networking terminology and then look at exactly what it means when we use the word Ethernet.

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L:l llertlet I letworl< for the 5mall Office and Professional Home Office Jan L. Harrington AMSTERDAM " BOSTON ~ HEIDELBERG ~ LONDON NEW YORK 9 OXFORD ~ PARIS ~ SAN DIEGO SAN FRANCISCO ~ SINGAPORE ~ SYDNEY 9 TOKYO MORGAN KAUFMANN PUBLISHER. c ELSEVIER Morgan Kaufmann is an imprint of Elsevier
Publisher Denise Penrose Acquistions Editor Rick Adams Publishing Services Manager George Morrison Project Manager Marilyn E. Rash Assistant Editor Kimberly Honjo Copyeditor Joan Flaherty Proofreader Debbie Prato Cover Design Alisa Andreola Interior Printer Malpe-Vail Cover Printer Phoenix Color Corp. Morgan Kaufmann Publishers is an imprint of Elsevier. 30 Corporate Drive, Suite 400 Burlington, MA 01803 This book is printed on acid-free paper. Copyright 9 2007 by Elsevier Inc. All rights reserved. Designations used by companies to distinguish their products are often claimed as trademarks or registered trademarks. In all instances in which Morgan Kaufmann Publishers is aware of a claim, the product names appear in initial capital or all capital letters. Readers, however, should contact the appropriate companies for more complete information regarding trademarks and registration. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any meansm electronic, mechanical, photocopying, scanning, or otherwisemwithout prior written permission of the publisher. Permissions may be sought directly from Elsevier's Science & Technology Rights Department in Oxford, UK: phone: (+44) 1865 843830, fax: (+44) 1865 853333, e-mail: permissions@elsevier.com. You may also complete your request on-line via the Elsevier homepage (http://elsevier.com),by selecting "Support & Contact" then "Copyright and Permission" and then "Obtaining Permissions." Library of Congress Cataloging-in-Publication Data Harrington, Jan L. Ethernet networking for the small office and professional home office / Jan L. Harrington. p. cm. Includes bibliographical references and index. ISBN-13:978-0-12-373744-1 (alk. paper) ISBN-10:0-12-373744-3 (alk. paper) 1. Ethernet (Local area network system) 2. Home offices. 3. Business enterprisesmComputer networks. I. Title. TK5105.8.E83H273 2007 004.6'8--dc22 2007010951 For information on all Morgan Kaufmann publications, visit our Web site at www.mkp.com or www.books.elseviercom Printed in the United States of America 07 08 09 10 11 10 9 8 7 6 5 4 3 2 1 I Workingtogether to grow libraries in developing countries
Confenfs Preface ix What You Need to Know xi Acknowledgments xi Part One: Introduction Chapter 1: Introduction 3 Anatomy of a Network 3 Network Components 5 Clients, Servers, and Peers 7 Data Communications Protocols 9 Layered Protocols 11 Another Word on Protocol Stacks 13 Network Operating Systems 14 What Ethernet Really Means 15 Types of Ethernet 15 The Speed and Bandwidth Connection 17 Ethernet Standards 18 A Bit of Ethernet History 19 iii
iv Contents Chapter 2: How TCP/IP and Ethemet Work 21 Network Data Transmission 22 Major TCP/IP Protocols 23 The Operation of a Protocol Stack 23 The Application Layer 24 The Transport Layer 25 The Internet Layer 29 The Logical Link Control Layer 31 The Ethernet MAC Protocol 33 Ethernet Frames 33 Ethernet Media Access 35 Alternative Protocol Stacks 38 Part Two: Design and Connectivity Chapter 3: Fast and Gigabit Ethernet Media and Standards 41 UTP Cabling 41 UTP Standards 42 UTP Cabling Lengths 44 UTP Jack Wiring 46 Fiber Optic Cabling 47 Single versus Multimode Fiber Optics 48 Fiber Optic Cable Bundles 49 Fast Ethernet Standards 50 Twisted-Pair Wire 51 Fiber Optics 51 Gigabit Ethernet Standards 52 Fiber Optics 52 Twisted-Pair Wire 53 Chapter 4: Creating Network Segments 55 Hubs (Repeaters) 56 Unmanaged Hubs 57 Managed Hubs 59 Stackable Hubs 62 Propagation Delay 62 Switches 64 Switch Learning 66 Creating a Simple Switched Segment 68 Creating Hierarchical Switched Configurations 68
Contents Cabling Issues 73 Looping Issues 74 Where Do You Put It? Wiring Closets, Walls, Floors, and Ceilings--Oh, My! 75 Appendix: Wiring RJ-45 Plugs and Connectors 81 Chapter 5: C o n n e c t i n g to the Internet 89 ISPs and IP Addresses 89 Internet Connection Protocols 91 Point-to-Point Protocol 91 Point-to-Point Protocol Over Ethernet for Cable and DSL 92 Dial-up Connections 92 Modems and POTS 92 Integrated Services Digital Network 97 Direct Connections 100 Satellite 100 Cable 103 Digital Subscriber Line 105 Leased Lines 108 Wireless 109 Chapter 6: Routing 111 IP Addressing 112 IPv4 Addressing 113 IPv6 Addressing 115 Getting an IP Address 117 ISPs and IP Addresses 118 Static IP Addresses 118 Dynamic IP Addresses 122 Domain Names and DNS 125 Making Routing Decisions 127 Routers and the TCP/IP Protocol Stack 127 Routing Tables 128 Subnet Masking 129 Router Capabilities 130 Making Connections and Network Address Translation 131 Firewalls and Port Management 132 Adding Routers to an Ethernet 133 Physical Connections 133 Configuring the Router 135
vi Contents Chapter 7: Integrating Wireless Transmissions 141 Wireless MAC Protocol versus Ethernet MAC Protocol 142 Wireless Speeds and Standards 142 Wireless Access Points 144 Service Set Identifiers 144 Adding Access Points to a Wired Network 147 Wireless Security Issues 148 WEP 148 WiFi Protected Access 150 Part Three: Making the Network Work Chapter 8: N e t w o r k Servers: Files, the Web, and Printers 155 Client-Server versus Peer-to-Peer File Sharing 156 Server Operating Systems 157 File Server Services 157 Widely Used Server Operating Systems 158 Web Servers 166 Print Serving 167 Shared Printer Architectures 168 Occasional Printer Sharing 168 Printing through a Server 174 Chapter 9: N e t w o r k Maintenance, Monitoring, and Control 177 Command-Line Tools 178 netstat 179 ping 182 Sample GUI-Based Tools 183 Freeware: Spiceworks 184 For Very Small Networks: Network Magic 186 For Larger Networks: LANsurveyor 189 Real-Time Monitoring and Packet Sniffing 193 Example: LANdecoder32 193 Remote Control 196 Making a Connection 196 Observation and Control 197 File Exchange 200 Messaging 200
Contents vii Chapter 10: Security Issues 203 Security Threats to Home and Small Offices 204 Malware 204 Denial-of-Service Attacks 205 Authentication Vulnerabilities 206 Employees and Other Local People 207 Physical Vulnerabilities 214 Basic Defenses 214 Virus Detection Software 214 Firewalls 222 Software Patching 226 Backup 227 Passwords 234 Enhancing Password Security with Tokens 234 User Education 236 Handling DoS Attacks 236 Advanced Defenses 241 Intrusion Detection Systems 241 Virtual Private Networks 244 Security Resources 248 Professional Security Update Sites 248 Other Sites of Interest 249 Chapter 11: Network Design and Simulation Software 251 Network Design Tools 252 The Network Hierarchy 253 Choosing and Configuring Network Devices 254 Linking Network Devices 263 Simulating Network Traffic 267 Assigning Traffic Loads 268 Running Simulations 270 Documenting the Network Design 272 Part Four: Ethernet Solution Examples Chapter 12: Network Example 1: Professional Home Network 277 Chapter 13: Ethernet Example 2: Small-But-Growing Real Estate 281 Business Overview 281 Network Plans 283 Network Design Considerations 284
viii Contents Chapter 14: Network Example 3" Small Law Firm 289 The Internet, the Backbone, and Equipment Rooms 291 Between the Floors 293 The Fifth-Floor Server Room 294 The Fourth-Floor Wiring Closet 295 Connecting End-User Devices 295 Security Considerations 297 A p p e n d i x A: O l d e r E t h e r n e t S t a n d a r d s 299 Thick Coaxial Cable (10BASE5) 300 Thin Coaxial Cable (10BASE2) 301 10BASE-T 305 Creating 10BASE-T Network Segments with a Hub 305 A p p e n d i x B" T C P a n d U D P P o r t s 309 Well-Known Ports 309 Registered Ports 314 Port List References 315 A p p e n d i x C: P r o d u c t s a n d V e n d o r s 317 Glossary 323 Index 333
Preface Computer networks interconnected collections of computing hardware and s o f t w a r e ~ a r e a fact of life today. You might use a network to connect to a printer located in another room, to interact with the Internet, or to share files with someone in your company who is working in another city. Each type of network has its own hardware and software requirements, all of which is surrounded by a bewildering array of terminology. A network can be as small as two computers and a printer located in the comer of a family room or as large as the entire world. Although much of the theory of data transmission is the same, regardless of the network's size, the specifics of the hardware and software are somewhat different, and no single book could describe all of it (unless you wanted to move the book with a forklift, that is). This book focuses on professional networks that are in either a small com- mercial space or a home. Today, such small networks use a single physical ix
Preface s t a n d a r d ~ E t h e m e t ~ t h a t was designed primarily for networks that are contained within a single physical location. (Remote users can access the network through interconnections to other networks made, for example, by the Internet, but the permanent parts of the network are typically housed in one building or a group of buildings located in close physical proximity.) If you need to design, install, and manage a network in such an environ- ment, then this book will give you an understanding of the technology in- volved in an Ethernet network. It will teach you how Ethernets work and what you need to put one together. Probably the toughest part of understanding networks is the jargon. If you're unfamiliar with networking terminology and acronyms, then a sen- tence like "To hook up to the legacy 10BASE2 segment, you connect the B NC connector to the NIC" is meaningless gibberish. One of the major goals of this book is therefore to demystify the secret language of networks for you so that you can speak in acronyms just like the rest of the network gurus. One of my greatest frustrations with networking books is that they often focus on only one layer of the network. To be technically accurate, "Ether- net" refers to only one part of the hardware. However, if you are going to be responsible for an Ethernet network, then you need to know a lot more than just how to choose and configure your network hardware. You also need information about the devices you can attach to your network and the software you will need to make it all work. In addition, you will probably want to give some thought to managing the network. And most important, you will want to look at your network in terms of security; even if your net- work's only outside connection is to the Internet, you are vulnerable to a variety of system attacks! This book goes beyond the hardware aspects of Ethernet to look at the entire network from bottom to top. Another major concem with writing a book of this type is the level of tech- nical detail. How much do you really need or want to know about how net- work signals are transmitted? If you want to know which specific signals are carried on which wires within a network cable, then this is not the book for you. However, if you want enough technical detail to be able to make intelligent choices about what types of transmission media to use for your
Preface xi network and the way to interconnect the parts of that network, then you are holding the fight volume. What You Need to Know To understand the material in this book, you need a thorough knowledge of basic PC hardware and at least one PC operating s y s t e m ~ f o r example, Windows 2000 or newer, some flavor of UNIX, or Mac OS X. I have an unabashed preference for the latter, but we each go where our experience and hearts take us. You should also be comfortable with basic PC software such as word processors, e-mail, and World Wide Web browsers. Acknowledgments Writing a book for Morgan Kaufmann is an absolute delight. I'd like to thank both Rick Adams, my editor, and Rachel Roumeliotis, his assistant, for all their help. And, of course, much thanks to the project manager, Marilyn Rash; the copy editor, Joan Flaherty; and the proofreader, Debbie Prato. In addition, a large number of vendors gave us permission to use illustra- tions and photos of their products. My thanks go out to all of them. (You can find contact information for those vendors in Appendix C.) http ://www.blackgryphon.info
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Introduction The first two chapters of this book present some introductory conceptual material about networking and Ethernet. By the time you finish reading them, you will understand exactly what Ethernet is and the part it plays in your network.
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Introduction One of the biggest problems when discussing networking is knowing where to start. The subject of computer networks is one of those areas for which you have to "know everything to do anything." Usually, the easiest way to ease into the topic is to begin with some basic networking terminology and then look at exactly what it means when we use the word Ethernet. Anatomy of a Network A computer network is a combination of hardware and software that allows computers and other devices (for example, printers and file servers) to communicate with one another through some form of telecommunications media (for example, telephone lines).
Introduction Note: As you read material about data communications, you may see references to POTS lines. POTS stands for "plain old telephone service." Networks can be classified by the distances they cover and whether they include technology like that used on the Internet: LAN (local area network): A network confined to a small geo- graphic a r e a ~ s u c h as a floor, single building, or group of buildings in close physical proximity (for example, a college campus or an office p a r k ) ~ that is almost always owned by a single organization. The organization owns the telecommuni- cations lines as well as the hardware connected to the network. Intranet: A network (LAN or WAN) owned by a single compa- ny that uses technology similar to that used on the Internet. MAN (metropolitan area network): An outdated term describ- ing a network that covers an entire city. Today, the concept of a MAN has been replaced largely by the WAN. WAN (wide area network): A network that covers a large geo- graphic area, such as a city, state, or one or more countries. Al- though a WAN may be owned by a single organization, the network usually includes telecommunications media (for ex- ample, telephone lines or satellite transmissions) that are leased from commercial telecommunications providers. Internet: When in all lowercase letters (internet), a WAN that connects multiple networks into a larger network. When writ- ten with a leading uppercase letter (Internet), it is the global network that supports the World Wide Web. Because of the po- tential for confusion between internet and Internet, the term in- ternet is rarely used today. The technologies we will be discussing in this book are applicable to LANs and intranets. Although we will discuss connecting LANs to the Internet, the focus is on creating and maintaining networks that serve small to medium-size workgroups in small offices, regardless of whether they are located in commercial buildings or homes.
Anatomy of a Network Network Components A computer network is made up of three major components: Hardware: The equipment that connects to the network. Typi- cally, this includes computers, printers, and modems. Each dis- tinct piece of hardware on a network is known as a node. In addition to the hardware that actually uses the network to trans- fer data to perform work for an organization, a network may contain specialty hardware that helps manage the network and connects it to other networks. Such hardware includes routers, bridges, switches, hubs, repeaters, and gateways. You will read about network hardware of these types throughout this book. Each device on a network is identified by two types of ad- dresses. The first is a hardware address that physically identi- fies the piece of equipment. In many cases, this address is set by the hardware manufacturer and is not easily changed. These addresses, known as MAC (media access control) addresses, must be unique throughout the network segment. If a manufac- turer happens to produce hardware with duplicated MAC ad- dresses, then a network segment that uses that hardware cannot function. The second type of address is a software address that is add- ed by the software that handles data transmission. The software address can be changed as needed. Software: The programs that manage the transfer of data throughout the network, most commonly known as network operating systems (NOS). Current desktop operating s y s t e m s ~ Windows, Mac OS X, and L i n u x ~ a r e capable of network operations fight out of the box. However, they cannot provide the robust, centralized, shared services such as file sharing needed by commercial networks. Most organizations therefore end up investing in specialized network operating system soft- ware to provide services such as file sharing, user management, security, and directory management. Transmission media: The cables or wireless signals that carry data from one node to another. In addition, there must be interfaces between the hardware and the network. These often take the form of expansion boards that are added to pieces of
Introduction hardware (network interface cards, or NICs, such as that in Figure 1-1), al- though a significant number of today's computers and printers are shipped with network hardware already installed on their motherboards. Depending on the type of transmissions media in use, a network may also need hardware connections between the media coming from a piece of hardware and the network itself. Figure 1-1: A network interface card (Courtesy of Farallon Corp.) In Figure 1-2 you can see a generalized diagram of how the hardware fits together. Each device you want to connect to a network must have either a network interface card or networking hardware installed on its mother- board. The NIC (or the motherboard) contains a port to which a cable can be attached. That cable runs to the network, connecting to the network transmission medium with some sort of attachment unit. Early networks had visible attachment units that physically tapped into the network cable. Today, however, most attachment units are part of the network interface hardware.
Anatomy of a Network Network j~---.-.--.--.-. Hardware device Interface Card (computer, printer, etc.) or Networking support on motherboard Port for attaching network cable Device-to-network cable (transceiver cable) Network transmission medium Medium Attachment Unit or transceiver Figure 1-2: Generalized network connections A wide variety of hardware and transmission media are available for Ether- net LANs and intranets. We will therefore be spending a considerable amount of time in this book looking at hardware choices. Clients, Servers, and Peers When hardware devices exchange messages over a network, the software governing the exchange can view the hardware in one of two relationships: client~server or peer-to-peer. With a client/server relationship, the client device (usually a computer) makes a request for some type of network s e r v i c e ~ f o r example, printing or a file t r a n s f e r ~ f r o m a device (typically, but not always, another computer) dedicated to providing that service (the server). Servers may store files to be printed, manage files that are to be shared by multiple users, send and receive e-mail, or support a Web site. Because servers are designed to handle requests from multiple network users, they are typically the fastest and most powerful computers on the network. How many servers you have and the specific functions they per- form depend on the needs of your network. We will discuss a number of types of servers throughout this book.