Sosinsky

The book you need to succeed!

Your A-Z guide to networking essentialsWhether you’re setting up a global infrastructure or just networking two computers at home, understanding of every part of the process is crucial to the ultimate success of your system. This comprehensive book is your complete, step-by-step guide to networking—from different architectures and hardware to security, diagnostics, Web services, and much more. Packed with practical, professional techniques and the very latest information, this is the go-to resource you need to succeed.

Spine: 1.82"

• Demystify the basics: network stacks, bus architectures, mapping, and bandwidth

• Get up to speed on servers, interfaces, routers, and other necessary hardware

• Explore LANs, WANs, Wi-Fi, TCP/IP, and other types of networks

• Set up domains, directory services, file services, caching, and mail protocols

• Enable broadcasting, multicasting, and streaming media

• Deploy VPNs, firewalls, encryption, and other security methods

• Perform diagnostics and troubleshoot your systems

Barrie Sosinsky, PhDis Chief Analyst and Founder of the Sosinsky Group, a consulting group focusing on network system design, database design, and application development and testing. He has written or contributed to over 35 technical books and 500 articles and is the founding editor of Storage Update newsletter.

Barrie Sosinsky

Shelving Category:COMPUTERS / Networking / General

Reader Level:Beginning to Advanced

$44.99 USA$53.99 Canada

www.wiley.com/compbooks

Create a secure network for home or enterprise

Learn basic building blocks and standards

Set up for broadcasting, streaming, and more

Netw

ork

ing

Networking

Everything you need to set up and maintain large or small networks

01 431313-ffirs.indd iii01 431313-ffirs.indd iii 7/31/09 8:54 PM7/31/09 8:54 PM

Networking Bible

Barrie Sosinsky

01 431313-ffirs.indd i01 431313-ffirs.indd i 7/31/09 8:54 PM7/31/09 8:54 PM

Networking Bible

Published byWiley Publishing, Inc.10475 Crosspoint BoulevardIndianapolis, IN 46256www.wiley.com

Copyright © 2009 by Wiley Publishing, Inc., Indianapolis, Indiana

Published by Wiley Publishing, Inc., Indianapolis, Indiana

Published simultaneously in Canada

ISBN: 978-0-470-43131-3

Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

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, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, 201-748-6011, fax 201-748-6008, or online at http://www.wiley.com/go/permissions.

LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR MAKE NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CONTAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ.

For general information on our other products and services or to obtain technical support, please contact our Customer Care Department within the U.S. at (877) 762-2974, outside the U.S. at (317) 572-3993 or fax (317) 572-4002.

Library of Congress Control Number: 2009932713

Trademarks: Wiley and related trade dress are registered trademarks of Wiley Publishing, Inc., in the United States and other countries, and may not be used without written permission. All other trademarks are the property of their respective owners. Wiley Publishing, Inc., is not associated with any product or vendor mentioned in this book.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

01 431313-ffirs.indd ii01 431313-ffirs.indd ii 7/31/09 8:54 PM7/31/09 8:54 PM

This book is dedicated to my wife Carol Westheimer, with all my love.

About the AuthorBarrie Sosinsky has written about computers and technology for over 25 years beginning with writing about personal computers for the Boston Computer Society in the early 1980s. He has published books on operating systems, applications, databases, desktop publishing, and network-ing for publishers such as Que, Sybex, Ventana, IDG, Wiley, and others and seen the industry change and reinvent itself several times.

At heart Barrie is a PC enthusiast. He loves building computers, finding and learning about new applications that allow him to do new things, and keeping up with the latest advances in the field of computer technology, which he believes is just in its infancy. Having lived long enough to see the Boston Red Sox win not one but two World Series, he remains committed to living long enough to see grandchildren and to someone clone a wooly mammoth. To this list (replacing the Red Sox) he adds the new milestone of holding a universal translator in his hands; a device he believes will appear within this next decade.

The author lives in Medfield Massachusetts about 25 miles southwest of Boston with his six cats Stormy, Shadow, Smokey, Scamper, Slate, and Spat; his son Joseph, his daughter Allie, his wife Carol; and Brittany the turtle surrounded by pine trees, marauding deer, and wild turkeys.

You can reach Barrie at bsosinsky@mindspring.com, where he welcomes your comments and suggestions.

01 431313-ffirs.indd iii01 431313-ffirs.indd iii 7/31/09 8:54 PM7/31/09 8:54 PM

iv

CreditsAcquisitions EditorCourtney Allen

Project EditorSarah Cisco

Technical EditorSteve Wright

Copy EditorMarylouise Wiack

Editorial DirectorRobyn Siesky

Editorial ManagerCricket Krengel

Business ManagerAmy Knies

Senior Marketing ManagerSandy Smith

Vice President and Executive Group PublisherRichard Swadley

Vice President and Executive PublisherBarry Pruett

Project CoordinatorKristie Rees

Graphics and Production SpecialistsCarrie CesaviceAndrea HornbergerJennifer MayberryMark Pinto

Quality Control TechniciansMelissa CossellJohn Greenough

Proofreading and IndexingBroccoli Information ManagementChristine Sabooni

01 431313-ffirs.indd iv01 431313-ffirs.indd iv 7/31/09 8:54 PM7/31/09 8:54 PM

v

Table of ContentsAbout the Author .................................................................................................................iiiAcknowledgments ............................................................................................................... xxIntroduction ...................................................................................................................... xxi

Part I: Network Basics 1

Chapter 1: Networking Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Defining Computer Networking ............................................................................................4Network Type Overview .......................................................................................................5Transmission Types ..............................................................................................................7

Point-to-point communication ....................................................................................7Broadcast communication ...........................................................................................7

Topologies ............................................................................................................................8Physical topologies ......................................................................................................9

Bus systems .....................................................................................................10Star networks ..................................................................................................11Rings ...............................................................................................................13Mesh networks ................................................................................................14Trees or hierarchical networks .........................................................................15

Hybrid topologies......................................................................................................16Logical topologies......................................................................................................16

Logical daisy chain topology ...........................................................................17Logical star topology .......................................................................................18Logical mesh topology .....................................................................................18

Summary ............................................................................................................................19

Chapter 2: The Network Stack  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Standard Development Organizations .................................................................................21The OSI Reference Model ....................................................................................................23How Layers Communicate ..................................................................................................24The Physical Layer ..............................................................................................................28The Data Link Layer ............................................................................................................28The Network Layer .............................................................................................................29The Transport Layer ............................................................................................................30The Session Layer ...............................................................................................................31The Presentation Layer ........................................................................................................31The Application Layer .........................................................................................................31

02 431313-ftoc.indd v02 431313-ftoc.indd v 7/31/09 8:57 PM7/31/09 8:57 PM

vi

Contents

The TCP/IP Reference Model ..............................................................................................32Comparing the OSI and TCP/IP Reference Models ..............................................................33Summary ............................................................................................................................34

Chapter 3: Architecture and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Network Architecture and Topology ...................................................................................36

Point-to-point ...........................................................................................................38Physical point-to-point connections ................................................................39Virtual point-to-point connections ..................................................................40Packet switched or transient connections ........................................................42Switched connections ......................................................................................44

Switched and Packet Networks ...........................................................................................45Bus Architectures ................................................................................................................46

Network segments .....................................................................................................47Collision domains .....................................................................................................48Signal termination .....................................................................................................50

Connection Points ...............................................................................................................50Peer-to-Peer Networks ........................................................................................................53Client-Server Networks .......................................................................................................54Multi-Tiered Networks ........................................................................................................56Thin Client/Server ...............................................................................................................58

Terminal servers ........................................................................................................58X Window networks .................................................................................................59

Summary ............................................................................................................................59

Chapter 4: Network Discovery and Mapping . . . . . . . . . . . . . . . . . . . . . . 61Network Discovery .............................................................................................................62

Node advertisement ..................................................................................................67Browsing ...................................................................................................................68Polling .......................................................................................................................70Connections ..............................................................................................................70

Simple Network Management Protocol ...............................................................................73Windows Management Instrumentation .............................................................................77Mapping .............................................................................................................................78Summary ............................................................................................................................80

Chapter 5: Bandwidth and Throughput  . . . . . . . . . . . . . . . . . . . . . . . . . . 81Bandwidth and Capacity .....................................................................................................82

Beads flow through a pipe of syrup ...........................................................................82Signaling ...................................................................................................................83Bandwidth.................................................................................................................87Sampling theory ........................................................................................................88

Multiplexing .......................................................................................................................91Time Division Multiplexing .......................................................................................92Frequency Division Multiplexing ..............................................................................93Other multiplexing technologies ...............................................................................94

02 431313-ftoc.indd vi02 431313-ftoc.indd vi 7/31/09 8:57 PM7/31/09 8:57 PM

vii

Contents

Flow Control ......................................................................................................................96Traffic Engineering ..............................................................................................................97

Packet shaping ..........................................................................................................97Leaky Bucket algorithm .............................................................................................98Token Bucket algorithm ............................................................................................99

Quality of Service ..............................................................................................................101Summary ..........................................................................................................................102

Part II: Hardware 105

Chapter 6: Servers and Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107Network Server Types .......................................................................................................108Capacity and Loading .......................................................................................................111

Three approaches ....................................................................................................111Solution frameworks ...............................................................................................112

Microsoft Operations Framework .................................................................115Microsoft Solutions Framework ....................................................................115

Server and Systems Sizing .................................................................................................117Defining levels of service .........................................................................................117

Response time ..............................................................................................118Throughput ..................................................................................................118Availability ...................................................................................................119Reliability .....................................................................................................120Scalability .....................................................................................................120Adaptability ..................................................................................................120Security ........................................................................................................120

Quantifying performance ........................................................................................120Performance relationships .............................................................................122Eliminating bottlenecks .................................................................................125Network modeling ........................................................................................129

Server upgrades .......................................................................................................131Summary ..........................................................................................................................133

Chapter 7: The Network Interface  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135What Is a Network Interface? ............................................................................................135

Physical network interfaces .....................................................................................136Logical network interfaces .......................................................................................137

Network Addressing .........................................................................................................138Physical addresses ...................................................................................................138Logical addresses .....................................................................................................139

Configuring Network Interfaces ........................................................................................141Bindings and Providers .....................................................................................................144Isolation and Routing ........................................................................................................146

Physical isolation .....................................................................................................147Protocol isolation ....................................................................................................148

02 431313-ftoc.indd vii02 431313-ftoc.indd vii 7/31/09 8:57 PM7/31/09 8:57 PM

viii

Contents

Bus Interfaces for NICs .....................................................................................................149A sample network adapter .......................................................................................151Network drivers ......................................................................................................152

Summary ..........................................................................................................................153

Chapter 8: Transport Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155Wired Media .....................................................................................................................155

Wiring the physical plant ........................................................................................156Twisted pair ............................................................................................................158Coaxial cable ...........................................................................................................161Ethernet wiring .......................................................................................................162Fiber-optic cable .....................................................................................................167

Attenuation and dispersal ..............................................................................168Physical description .......................................................................................171Fiber-optic networks .....................................................................................174

Wireless ............................................................................................................................176Electromagnetic radiation ........................................................................................176Information and transmission..................................................................................179Wireless connections ...............................................................................................181

Radio links ....................................................................................................181Microwave links ............................................................................................182

Summary ..........................................................................................................................183

Chapter 9: Routing, Switching, and Bridging . . . . . . . . . . . . . . . . . . . . . 185Circuit versus Packet Switching ........................................................................................185Layer 1 and Layer 2 Connection Devices ...........................................................................189

Passive hubs ............................................................................................................189Repeaters .................................................................................................................190

Switches ............................................................................................................................191Bridges ..............................................................................................................................192Routers .............................................................................................................................195

Control plane ..........................................................................................................197Forwarding plane ....................................................................................................197Routing topologies ..................................................................................................199Optimization methods ............................................................................................201Distance vector routing ...........................................................................................201

The Bellman-Ford algorithm .........................................................................202Count-to-infinity ...........................................................................................204Routing Information Protocol ........................................................................204Destination-Sequenced Distance Vector Routing ...........................................206

Link state routing ....................................................................................................206Dijkstra’s algorithm .......................................................................................207Open Shortest Path First ................................................................................209Intermediate System to Intermediate System Routing ....................................210

02 431313-ftoc.indd viii02 431313-ftoc.indd viii 7/31/09 8:58 PM7/31/09 8:58 PM

ix

Contents

Path vector routing ..................................................................................................211A path vector example ...................................................................................212The Border Gateway Protocol ........................................................................212

Network loops ........................................................................................................214The Spanning Tree Protocol ....................................................................................216

Node/bridge hierarchy ...................................................................................217Network segment costs ..................................................................................220Dynamic optimization ...................................................................................220Rapid Spanning Tree Protocol .......................................................................222

Onion Routers ..................................................................................................................226Tor ..........................................................................................................................228Tor clients ...............................................................................................................228Hidden services .......................................................................................................229

Gateways ..........................................................................................................................231Summary ..........................................................................................................................231

Part III: Network Types 233

Chapter 10: Home Networks  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235Features of a Home Network ............................................................................................236Broadband Connections ....................................................................................................240Wireless Connections ........................................................................................................241Wired Connections ...........................................................................................................242

Ethernet ..................................................................................................................242Phone lines..............................................................................................................243Power over Ethernet ................................................................................................246HomePlug Powerline ...............................................................................................246

HomePlug modulation ..................................................................................248Frames and sequences ...................................................................................250Security .........................................................................................................252

Home Network Servers .....................................................................................................252Summary ..........................................................................................................................254

Chapter 11: Peer-to-Peer Networks and Personal LANs . . . . . . . . . . . . . 255Peer-to-Peer Networks ......................................................................................................256

Pure P2P networks ..................................................................................................257Small world networks ....................................................................................257Gnutella ........................................................................................................257Freenet ..........................................................................................................259

Hybrid P2P systems ................................................................................................260Napster ..........................................................................................................260Torrents ........................................................................................................260

Friend-to-Friend Networks ...............................................................................................264

02 431313-ftoc.indd ix02 431313-ftoc.indd ix 7/31/09 8:58 PM7/31/09 8:58 PM

x

Contents

Bus Networking ................................................................................................................264Universal serial bus .................................................................................................265FireWire ..................................................................................................................268Bluetooth ................................................................................................................270

Connections ..................................................................................................271Profiles ..........................................................................................................273

Summary ..........................................................................................................................274

Chapter 12: Local Area Networking  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275Introduction .....................................................................................................................276

The IEEE 802 LAN standards ..................................................................................277Broadcast channels ..................................................................................................277

Ethernet ............................................................................................................................281Ethernet frames .......................................................................................................284

Frame structure .............................................................................................286Burst mode ....................................................................................................288VLAN frames .................................................................................................288

Carrier Sense Multiple Access with Collision Detection ..........................................289Full-duplex operation .............................................................................................291

Token Ring Networks .......................................................................................................291Fiber Distributed Data Interface Networks ........................................................................297Automation Networks .......................................................................................................301

X10 and home automation ......................................................................................302Process control systems ...........................................................................................308

Modbus .........................................................................................................311BACnet and LonTalk .....................................................................................314OPC ..............................................................................................................314

Summary ..........................................................................................................................317

Chapter 13: Wide Area Networks and Backbones  . . . . . . . . . . . . . . . . . 319What Is a WAN? ...............................................................................................................320Circuit Switching Networks ..............................................................................................321

The Public Switched Telephone Network ................................................................322Integrated Services Digital Network ........................................................................325Digital Subscriber Line ............................................................................................326Cable network .........................................................................................................331

T- and E-Carrier Networks ................................................................................................331Synchronous Optical Networking .....................................................................................333

SONET architecture ................................................................................................334Framing ..................................................................................................................335Packet over SONET .................................................................................................338

Packet Switching Networks ...............................................................................................340X.25 Networks ..................................................................................................................341Switched Multi-megabit Data Services ...............................................................................342Asynchronous Transfer Mode ..........................................................................................342Frame Relay ......................................................................................................................345

02 431313-ftoc.indd x02 431313-ftoc.indd x 7/31/09 8:58 PM7/31/09 8:58 PM

xi

Contents

Multi Protocol Label Switching ........................................................................................346The Internet and Internet2 ................................................................................................347

Internet Exchange Points .........................................................................................348Internet2 .................................................................................................................350

Summary ..........................................................................................................................351

Chapter 14: Wi-Fi Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353Wireless Networking .........................................................................................................354

Wi-Fi networks .......................................................................................................356IEEE 802.11x Standards ..................................................................................................357

802.11 legacy .........................................................................................................359802.11y ...................................................................................................................361Modulation .............................................................................................................362

Direct-Sequence Spread Spectrum .................................................................365Frequency Hopping Spread Spectrum ...........................................................367Orthogonal Frequency Division Multiplexing ................................................368

802.11 protocol ......................................................................................................369Collision avoidance .......................................................................................370802.11 frame structure ..................................................................................371Connection example ......................................................................................373

Wireless Access Points and Gateways ................................................................................375Repeaters and bridges..............................................................................................375Wireless Distribution System...................................................................................378

Wireless Routers and Gateways .........................................................................................380Router configuration ..............................................................................................382Router upgrades ......................................................................................................382

OLPC XO Wireless Network .............................................................................................384Antennas ...........................................................................................................................385

Antenna characteristics ............................................................................................385Multiple-Input Multiple-Output ..............................................................................389

Wireless Software ..............................................................................................................391Security .............................................................................................................................393

Wired Equivalent Privacy ........................................................................................394Wi-Fi Protected Access ............................................................................................396

Summary ..........................................................................................................................398

Chapter 15: Storage Networking  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399Storage Networking ..........................................................................................................400Storage Network Types .....................................................................................................401SANs versus NAS ..............................................................................................................403

Business Continuance Volumes ...............................................................................403Storage virtualization ...............................................................................................404

The Shared Storage Networking Model .............................................................................406The shared tape extension .......................................................................................407The Storage Domain ................................................................................................412

02 431313-ftoc.indd xi02 431313-ftoc.indd xi 7/31/09 8:58 PM7/31/09 8:58 PM

xii

Contents

Aggregation .............................................................................................................413Device models .........................................................................................................413

Fibre Channel Networks ...................................................................................................417Fibre Channel standards .........................................................................................418Port designations .....................................................................................................418The Fibre Channel Protocol ....................................................................................419

Fibre Channel traffic management .................................................................421Fibre Channel flow control ............................................................................421

Fibre Channel Arbitrated Loops ..............................................................................422Fibre Channel Switched fabrics ...............................................................................423

Fibre Channel addressing ..............................................................................423Zoning ...........................................................................................................424

Storage over IP ..................................................................................................................425iSCSI protocol .........................................................................................................426Fibre Channel over IP .............................................................................................428Internet Fibre Channel Protocol ..............................................................................429

Storage Area Network Management ..................................................................................429Internet Storage Name Service .................................................................................430

Summary ..........................................................................................................................431

Chapter 16: High-Speed Interconnects  . . . . . . . . . . . . . . . . . . . . . . . . . 433High-Performance Computing ..........................................................................................434Beyond Gigabit Ethernet ...................................................................................................435

10GBase-T .....................................................................................................436Higher-Speed Gigabit Ethernet ......................................................................437

TCP Offloading Engines ....................................................................................................437Zero Copy Networks .........................................................................................................440

Virtual Interface Architecture ..................................................................................441InfiniBand ...............................................................................................................443

Network Clusters ..............................................................................................................445Load balancing ........................................................................................................448Grid systems ...........................................................................................................449

Summary ..........................................................................................................................451

Part IV: TCP/IP Networking 453

Chapter 17: Internet Transport Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 455Transmission Control Protocol ..........................................................................................456Packet Structure ................................................................................................................457

Header fields ...........................................................................................................458Flags .......................................................................................................................459Checksum field .......................................................................................................459Control fields ..........................................................................................................460Data field.................................................................................................................460

02 431313-ftoc.indd xii02 431313-ftoc.indd xii 7/31/09 8:58 PM7/31/09 8:58 PM

xiii

Contents

Protocol Operation ...........................................................................................................461Connections ......................................................................................................................464Flow Control ....................................................................................................................465

Sliding windows ......................................................................................................465Congestion control ..................................................................................................466Multiplexing ............................................................................................................466

User Datagram Protocol ....................................................................................................467Ports .................................................................................................................................469Problems with TCP ...........................................................................................................472Summary ..........................................................................................................................474

Chapter 18: The Internet Protocols  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475Internet Protocol Overview ...............................................................................................476Internet Protocol Version 4 ...............................................................................................478

Addressing ..............................................................................................................478Dividing the namespace .................................................................................478Reserved addresses ........................................................................................483Zero Configuration addressing ......................................................................486IP datagrams ..................................................................................................486

Subnetting ........................................................................................................................494Setting an IP Address ........................................................................................................497

Static addressing .....................................................................................................498Dynamic addressing ................................................................................................499

Dynamic Host Configuration Protocol ..............................................................................500Configuration ..........................................................................................................501Securing DHCP .......................................................................................................502Bootstrap Protocol ...................................................................................................503

Internet Control Message Protocol ....................................................................................503Internet Protocol Version 6 ...............................................................................................506

Addressing ..............................................................................................................508IPv6 compressed notation .............................................................................509IPv6 calculators .............................................................................................510Dual-stack IPv6/IPv4 addresses .....................................................................512Address scopes and zones ..............................................................................512

IPv6 datagrams ........................................................................................................515IPv6 Neighbor Discovery .........................................................................................517ICMPv6 ...................................................................................................................518

Summary ..........................................................................................................................519

Chapter 19: Name Resolution Services . . . . . . . . . . . . . . . . . . . . . . . . . . 521HOSTS Files .....................................................................................................................522Address Resolution Protocol .............................................................................................525

ARP requests ...........................................................................................................526Reverse Address Resolution Protocol .......................................................................526Viewing the ARP cache ............................................................................................527

02 431313-ftoc.indd xiii02 431313-ftoc.indd xiii 7/31/09 8:58 PM7/31/09 8:58 PM

xiv

Contents

Network Basic Input/Output System .................................................................................528Windows Internet Name Service .......................................................................................529Domain Name System .......................................................................................................530

DNS requests ..........................................................................................................531DNS topology..........................................................................................................533Resource records .....................................................................................................534

Name Resolution versus Directory Services .......................................................................539Summary ..........................................................................................................................539

Part V: Applications and Services 541

Chapter 20: Network Operating Systems . . . . . . . . . . . . . . . . . . . . . . . . 543What Is a Network Operating System ...............................................................................544

Protocols and services .............................................................................................545General versus Special-Purpose NOS ......................................................................545

NOS Systems and Software ...............................................................................................547UNIX ......................................................................................................................548

POSIX ...........................................................................................................550STREAMS and sockets ...................................................................................551Single UNIX specification ..............................................................................552

Linux ......................................................................................................................553Distributions .................................................................................................554LAMP ............................................................................................................554Linux Standard Base ......................................................................................555

Solaris .....................................................................................................................555Novell NetWare and Open Enterprise Server ..........................................................557Windows Server ......................................................................................................557

Summary ..........................................................................................................................559

Chapter 21: Domains and Directory Services . . . . . . . . . . . . . . . . . . . . . 561Directory Services and Domains ........................................................................................562

Banyan VINES .........................................................................................................563Domain types ..........................................................................................................563Interoperability .......................................................................................................565

Domain Servers .................................................................................................................565Directory Services .............................................................................................................566

Synchronization and replication ..............................................................................567Single sign on ..........................................................................................................568Namespaces ............................................................................................................568Policy engines .........................................................................................................570Role-Based Access Control ......................................................................................574Identity management...............................................................................................575

02 431313-ftoc.indd xiv02 431313-ftoc.indd xiv 7/31/09 8:58 PM7/31/09 8:58 PM

xv

Contents

X.500 and LDAP ...............................................................................................................576Network Information Service ..................................................................................577LDAP servers ...........................................................................................................578LDAP Data Interchange Format ...............................................................................578Novell eDirectory ....................................................................................................579Distinguished Names ..............................................................................................580

Microsoft Active Directory ................................................................................................580Replication ..............................................................................................................584

Summary ..........................................................................................................................585

Chapter 22: File Services and Caching  . . . . . . . . . . . . . . . . . . . . . . . . . . 587Network Attached Storage ................................................................................................588

Features ..................................................................................................................589NAS versus SAN ......................................................................................................590Network file caching ...............................................................................................591

File Service Protocols ........................................................................................................593Network File System ...............................................................................................593Server Message Block/Common Internet File System ...............................................594

Samba ...............................................................................................................................595Samba security ........................................................................................................596Samba name resolution and browse lists .................................................................597Samba on Ubuntu ...................................................................................................598

Distributed File System .....................................................................................................601Summary ..........................................................................................................................604

Chapter 23: Web Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605The Hypertext Transfer Protocol .......................................................................................606

HTTP requests ........................................................................................................607HTTP status codes ...................................................................................................609Static versus dynamic pages ....................................................................................613

Web Services ....................................................................................................................614Service Oriented Architectures ..........................................................................................616Summary ..........................................................................................................................619

Chapter 24: Mail Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621The Three Main Protocols .................................................................................................622

Polled e-mail ...........................................................................................................622Push e-mail .............................................................................................................624

Message Parts ....................................................................................................................624Simple Mail Transfer Protocol ...........................................................................................626

Multipurpose Internet Mail Extensions ...................................................................627Base64 encoding ............................................................................................629MIME rendering ............................................................................................631

02 431313-ftoc.indd xv02 431313-ftoc.indd xv 7/31/09 8:58 PM7/31/09 8:58 PM

xvi

Contents

Post Office Protocol ..........................................................................................................632Web mail clients .....................................................................................................633

Internet Message Access Protocol ......................................................................................634Mail Servers ......................................................................................................................634Setting Up a Mail Client ....................................................................................................636Summary ..........................................................................................................................638

Chapter 25: Streaming Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639How Streaming Works ......................................................................................................640

Streaming versus progressive downloads .................................................................640Unicasting versus multicasting ................................................................................644

Streaming Protocols ..........................................................................................................646Real-Time Streaming Protocol .................................................................................646Real-Time Transport Protocol..................................................................................647Real-Time Control Protocol .....................................................................................649Synchronized Markup Integration Language ...........................................................650Encoding .................................................................................................................651

Streaming Servers .............................................................................................................653Streaming file formats .............................................................................................656Players.....................................................................................................................656Flash .......................................................................................................................657Silverlight ................................................................................................................659

Summary ..........................................................................................................................660

Chapter 26: Telephony and VoIP  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661Telephony .........................................................................................................................662Private Branch Exchange Systems .....................................................................................663

Asterisk ...................................................................................................................663Cisco Unified Communications Manager ................................................................665Microsoft Response Point ........................................................................................665

Voice over Internet Protocol ..............................................................................................666Analog telephone adapters ......................................................................................669Internet Protocol phones .........................................................................................670VoIP protocols ........................................................................................................672

Skinny Call Control Protocol .........................................................................672Real-Time Transport Protocol and Real-Time Transfer Control .....................673Session Traversal Utilities for NAT ................................................................673The H.323 Protocol .......................................................................................673Inter-Asterisk eXchange Protocol ...................................................................674Media Gateway Control Protocol ...................................................................674

Computer Telephony Integration ......................................................................................674

02 431313-ftoc.indd xvi02 431313-ftoc.indd xvi 7/31/09 8:58 PM7/31/09 8:58 PM

xvii

Contents

Video Telephony ...............................................................................................................676Mobile VoIP ............................................................................................................677Webcams ................................................................................................................677

Summary ..........................................................................................................................679

Part VI: Network Security 681

Chapter 27: Security Protocols and Services . . . . . . . . . . . . . . . . . . . . . . 683Network Security Overview ..............................................................................................684

Network vulnerabilities ...........................................................................................684The National Vulnerability Database .......................................................................687Points of Attack .......................................................................................................688Principles of secure network design ........................................................................690

Location Awareness and Network Access Protection .........................................................692Internet Security Protocols ................................................................................................694

IPsec .......................................................................................................................695Transport Layer Security .........................................................................................698HTTPS ....................................................................................................................700

Encryption and Cryptography ...........................................................................................702Brute force and ignorance........................................................................................703Symmetric key algorithms .......................................................................................704

Block ciphers .................................................................................................705Stream ciphers ...............................................................................................705Hash functions ..............................................................................................706

Asymmetric or public key algorithms ......................................................................708Kerberos ..................................................................................................................708

Summary ..........................................................................................................................711

Chapter 28: Firewalls, Gateways, and Proxy Servers . . . . . . . . . . . . . . . . 713Firewalls ...........................................................................................................................714

Firewall features ......................................................................................................714Personal firewalls ...........................................................................................716Router firewalls .............................................................................................717Hardware firewalls .........................................................................................718Server firewalls ..............................................................................................719Security gateways ..........................................................................................720

Network zones ........................................................................................................720Stateless filters .........................................................................................................722Stateful filters ..........................................................................................................723Application filters ....................................................................................................726Deny by default .......................................................................................................727Network Address Translation ..................................................................................728

02 431313-ftoc.indd xvii02 431313-ftoc.indd xvii 7/31/09 8:58 PM7/31/09 8:58 PM

xviii

Contents

Proxy Servers ....................................................................................................................732Transparent proxy servers and honeypots ...............................................................735Reverse proxy servers ..............................................................................................735

Summary ..........................................................................................................................737

Chapter 29: Virtual Private Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . 739VPN Technologies .............................................................................................................740

VPN types ...............................................................................................................740VPN links ................................................................................................................741Site-to-site topologies ..............................................................................................743VPN hardware .........................................................................................................745VPN software ..........................................................................................................746

The Windows Server 2008 VPN Service ........................................................747The Vista client ..............................................................................................749

Encryption ........................................................................................................................752Tunneling .........................................................................................................................752Tunneling Protocols ..........................................................................................................753

Generic Routing Encapsulation ..............................................................................753IPsec tunnels ...........................................................................................................754Secure Sockets Layer/Transport Layer Security ........................................................754Point-to-Point tunneling protocols ..........................................................................754

Point-to-Point Tunneling Protocol .................................................................754Layer 2 Forwarding Protocol .........................................................................755Layer 2 Tunneling Protocol ...........................................................................755

Summary ..........................................................................................................................756

Part VII: Network Management and Diagnostics 757

Chapter 30: Network Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759The Importance of Network Management .........................................................................760

FCAPS .....................................................................................................................760Fault management ...................................................................................................762

Event log files ................................................................................................762Alarms ...........................................................................................................764Event correlation ...........................................................................................765

Configuration management .....................................................................................766Consoles ........................................................................................................767Software lifecycles and deployments ..............................................................768

Accounting and administration ...............................................................................775Performance management .......................................................................................776Security management ..............................................................................................780

Network Management Software Categories .......................................................................780Network Frameworks .......................................................................................................781Summary ..........................................................................................................................784

02 431313-ftoc.indd xviii02 431313-ftoc.indd xviii 7/31/09 8:58 PM7/31/09 8:58 PM

xix

Contents

Chapter 31: Network Diagnostic Commands . . . . . . . . . . . . . . . . . . . . . 785Network Diagnostics .........................................................................................................786Network Commands .........................................................................................................786

Command line tools ................................................................................................786Network Shells ..................................................................................................................802

The Windows NetShell ...........................................................................................802Telnet sessions ........................................................................................................809PowerShell ..............................................................................................................810

Summary ..........................................................................................................................824

Chapter 32: Remote Access  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825Remote Access ..................................................................................................................826

Remote connection protocols ..................................................................................828Remote access services ............................................................................................828Remote desktops .....................................................................................................829

RADIUS Servers ................................................................................................................832RADIUS sessions .....................................................................................................834RADIUS roaming .....................................................................................................836The Diameter protocol ............................................................................................836

Summary ..........................................................................................................................838

Appendix A: TCP - UDP Port Assignments . . . . . . . . . . . . . . . . . . . . . . . 839

Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859

02 431313-ftoc.indd xix02 431313-ftoc.indd xix 7/31/09 8:58 PM7/31/09 8:58 PM

xx

This book is the culmination of many months of really hard work during which my family and publisher were very supportive. For many years now I’ve watched and read numerous books on network technology that have appeared — some highly technical, others specific

to a particular platform — and all written to various levels of expertise. This book aims to be a general introduction that will take a knowledgeable computer user from the basics to a much higher level of expertise in computer networking. As much as possible I have tried to not only include multiple platforms, but include developments that are on the cusp of their introduction.

I would like to thank my literary agent Matt Wagner at Fresh Books for recommending me for this title. His support and friendship over the years has been very gratifying to me.

The chance to write the Networking Bible for Wiley was something I really enjoyed doing. The Bible Series was created by IDG Books, acquired by Wiley, and has nurtured many high quality books that have helped people learn about different fields of technology for many years. I very well remember the people who started IDG, and although most of them are not now associated with these books their contribution to the field of computer publishing continues on.

I also would like to acknowledge the support of the staff at Wiley for their support in this project. They have been very professional and easy to work with. In particular I would like to thank the three people most associated with this project: Courtney Allen, who was the Acquisition Editor; Sarah Cisco who was the Project Editor; and Steve Wright, who was the Technical Editor. Steve did a terrific job with his technical oversight, as did Sarah and the others involved in the editing project. My special thanks to them all.

All book projects involve a considerable investment by both the author and the publisher. Shared risk. This book also required sacrifice by my family, who put up with my disappearance for many days at a time. During the course of writing this book, over many days and late nights I was con-stantly visited by a large number of small grey creatures who were my companions. With this book completed, I look forward to spending more time with them.

02 431313-ftoc.indd xx02 431313-ftoc.indd xx 7/31/09 8:58 PM7/31/09 8:58 PM

xxi

Networking is a vast subject that touches all aspects of computer technology. Indeed, some will argue that a computer that isn’t networked isn’t really a computer at all. It may be hyperbole to suggest that “The network IS the computer” as Sun did some years ago, but

every important computer technology has incorporated some method for sending and receiving data to and from other computers. If you go as far back as you care to, the very first commercial computers were built to amortize their costs by allowing users to time share. Computer reservation systems such as SABRE linked to terminals worldwide, and when the personal computer became nearly as cheap as a dumb terminal, those PCs became the distributed nodes.

The rise of the personal computer in the early 1980s and 1990s helped to spawn networking tech-nologies that made connectivity easier to achieve, cheaper, and most importantly more standard-ized. A whole host of different proprietary networking technologies have given way to the networking technologies of the Internet, TCP/IP networking. Although this book discusses some of the older technologies, the focus of this book is on the current state of computer networking and, therefore, much of the book explains internetworking standards based on TCP/IP. In ultrafast, high-bandwidth, and highly reliable networks, other technologies are used.

A number of these alternative technologies are presented in the context of the different capabilities that they provide. So while you will learn about local area networks of various types, a number of chapters in this book describe important technologies in the field of wide area networks, fiber optics, storage area networks, grid and cloud computing, and other advanced technologies. Sprinkled in the book are descriptions of new products such as the X0-1 laptop created by the One Laptop Per Child organization, SETI @ Home grid system, SONET networking, optical solitons, and many other things that you may not have heard about but that make the experience of reading this book I hope richer for you.

This book was written to be a general networking book and not to favor one computer platform over another. By nature I’m not a computer platform zealot. My first computer was a Macintosh, and over the years I’ve switched to Windows systems. Recently I’ve been working on a Ubuntu sys-tem, and at various times I’ve worked on different Linux as well as Solaris systems. I work on a small network, but over the years I’ve worked on both large and small, homo- and heterogeneous networks. Each network operating system has its plusses and minuses, but I’ve found that it is rare that I couldn’t perform some essential function on all of these operating systems.

This book presents examples of networking technology using a number of different platforms. Unfortunately (from my way of thinking) there are more examples drawn from Windows that I would have liked. Please take this as being largely the result of the time I had and the convenience these examples offered, more than a statement of their being particularly special.

03 431313-flast.indd xxi03 431313-flast.indd xxi 7/31/09 8:58 PM7/31/09 8:58 PM

xxii

Introduction

I’ve tried to walk the fine line between being theoretical enough to give you a solid foundation in computer networking, while being practical enough for you to find and use new technologies and products in your everyday work. There is a considerable amount of product information in this book, and I’ve tried very hard to make this information both accurate and up to date. Unfortunately, prod-uct information ages faster than any one of use would like, and many times in the course of writing this book, I’ve encountered products and companies I’ve known that are no longer with us. Many of these products were associated with people I’ve either met, known, or had some acquaintance with, so the passing of these products forces me to reminisce about times gone by.

This book is organized into seven parts:

l Part 1. The first part of this book presents general theory and networking principles. I’ve presented much of the material in the context of different networking models that have been widely used in the industry.

l Part 2. The second part of this book looks at various network hardware components, which includes systems, network interfaces, various physical media, and methods for cre-ating and maintaining circuits with particular emphasis on routing.

l Part 3. The third part of this book focuses on different network types, small and home networks, peer to peer technology, LANs and WANs, storage networks (SANs), as well as various high speed and high performance networks.

l Part 4. The fourth part of this book describes the various parts of the TCP/IP networking suite. This includes not only how TCP/IP is used, but details on addressing, name resolu-tion, and other features that both bedevil and occupy modern network administrators.

l Part 5. The fifth part of this book describes different applications and services that run on computer networks. Various network operating systems are discussed from a general prin-ciples viewpoint, and network services such as directory services, file services, mail, streaming media, and voice over IP round out this part of the book.

l Part 6. The three chapters in Part 6 focus on computer network security. In these chap-ters, you learn about: security protocols and services; firewalls, gateways, proxy servers, and other isolation technologies: and virtual private networks.

l Part 7. In the final part of this book, different network management and diagnostic tech-nologies are discussed. This includes classes of network management applications, some of which are large management frameworks that you might be unfamiliar with. Two chap-ters on network diagnostics and remote access technologies round out this book.

I hope that you enjoy reading this book as much as I have enjoyed writing it.

Barrie Sosinsky

Medfield, Massachusetts

March 18, 2009

03 431313-flast.indd xxii03 431313-flast.indd xxii 7/31/09 8:58 PM7/31/09 8:58 PM

Part I

Network Basics

IN THIS PARTChapter 1Networking Introduction

Chapter 2The Network Stack

Chapter 3Architecture and Design

Chapter 4Network Discovery and Mapping

Chapter 5Bandwidth and Throughput

04 431313-pp01.indd 104 431313-pp01.indd 1 7/31/09 8:59 PM7/31/09 8:59 PM

04 431313-pp01.indd 204 431313-pp01.indd 2 7/31/09 8:59 PM7/31/09 8:59 PM

3

CHAPTER

Networking Introduction

IN THIS CHAPTERNetwork and transmission

types

Topologies

pLANs, LANs, MANs, CANs, and WANs

A computer network is a connection or set of connections made between two or more computers for the purpose of exchanging data. Networks are built from a variety of building blocks: computers,

switches, cables, and so forth. In order to classify networks into different types, you need to consider factors such as the number of elements, distribu-tion of objects, and connection methods. In this chapter, different types of networks are described, as well as how the different network types impact their design.

The smallest network is a direct attachment between two computers with a cable. Peer-to-peer systems are used in computer workgroups where there are a small number of systems that don’t require a central service. Some computer buses are configurable and thus are considered small networks. These are called personal LANs, or pLANs, and Bluetooth is an example of this type of network. USB is not configurable and is therefore not a network.

A network that spans an office, floor, or building is called a local area net-work, or LAN. LANs can support multiple protocols, and connect different types of clients. A LAN that is separated by a bridging element would be considered a separate LAN. When the bridge separates multiple LANs that are geographically dispersed, it is considered a wide area network, or WAN.

You can analyze and categorize network topologies in terms of graph theory. Networks can be formed in a variety of ways that involve forming lines or chains, stars or hubs, rings, or mesh topologies. Different topologies offer different capabilities and have different requirements. The processes of map-ping a network’s topology can be done for physical or logical network ele-ments, or based on how signals propagate through the network.

05 431313-ch01.indd 305 431313-ch01.indd 3 7/31/09 8:59 PM7/31/09 8:59 PM

Part I: Network Basics

4

Defining Computer NetworkingTo be considered a network, a collection of elements needs to have the following: connection soft-ware, systems, and network elements (such as switches, physical transmission media, and an addressing system). Any computer network has the following essential components:

l The connected systems

l Connection software

l Networking hardware

l Physical transmission media

l An addressing system for each of the aforementioned components

This definition is sufficiently broad to allow us to discuss not only systems composed of comput-ers, but also cell phones and other aspects of telephony, storage devices, Wi-Fi, streaming, broad-band connections, and a wide range of disparate systems that you are likely to want to network together in some way.

Connection software is ubiquitous in all systems that must be networked together. You will find network software inside your computers’ operating systems, inside your networking hardware (routers or firewalls), in custom ASICs (Application Specific Integrated Circuit) or flash memory in network cards or hubs, and even inside the physical transmission medium if the medium is intelli-gently switched or amplified.

The physical transmission medium refers to any medium that can transmit an electromagnetic sig-nal. A signal is a time varying pattern in signal amplitude, voltage, or frequency that represents information in the form of data that can be propagated some distance and recognized by a receiver. Signals can be continuously variable (analog), or they can be discrete and limited to specific states (digital). Although analog computers exist, in nearly all circumstances the systems in use are digi-tal, and more specifically binary. Binary systems transmit information in one of two states: ON or OFF, 1 or 0, YES or NO, or voltage 1 or voltage 2. Digital computers use binary signals and Boolean logic because signaling is relatively simple and fast, and because binary signals can be made to represent any character or solve nearly any mathematical equation.

The transmission of binary signals for the data stream between two systems in a network means not only that the physical media can be wires and cables, but also that any part of the electromag-netic spectrum can theoretically be used to transmit data. When you open a browser on a cell phone, you are connecting to a network with a radio frequency connection. When a cellular net-work wants to transmit data across a long distance, it does so by using microwave transmitters. The 802.11 Wi-Fi standards are radio frequency transmissions. You can get interference from a 900 MHz wireless telephone that overlaps with the 802.11b standard, or from a microwave oven that operates at 2.4 GHz and interferes with the 802.11g Wi-Fi standard. Most of the networks described in this book use fixed wires to connect computer systems. However, radio frequency connections have no physical transmission medium.

05 431313-ch01.indd 405 431313-ch01.indd 4 7/31/09 8:59 PM7/31/09 8:59 PM

Chapter 1: Networking Introduction

5

Cross-RefRadio frequency connections are covered in Chapters 5, 8, and 14.

Any operations where data isn’t transmitted automatically aren’t part of our network definition. For example, if you copy data on one computer to a USB key and walk that USB key over to another computer, that wouldn’t be considered a computer network. The term we use to describe manual data transfer is sneakernet; this is not a network because it doesn’t conform to the principle that networks allow data to be sent to a system based on an address or identification scheme — the data in the USB key isn’t being sent to any address.

It’s best not to be too doctrinaire when using the addressing requirement, however. Broadcast communications would be considered network communications, although there is no specific address to a receiving system. Any system that fits the definition of a receiver can accept broadcast communications. Indeed, broadcast communications are essential in most network technologies. Systems send out broadcasts to indicate that they are available to perform a service, or that they exist and can service a request. Broadcast communications are used to identify a system or to browse the network. Implicit in the definition of a broadcast is that any system that conforms to the requirement meets one of the following conditions:

l It is on the same network, or runs the same identification protocol, such as Windows NetBEUI or WINS; or

l It has the software installed to accept and manage a data stream and can participate in broadcast communications.

In this book, I define a computer network as simply a connection or set of connections made between two or more computers for the purpose of exchanging data. Using this as a guiding princi-ple, I cover the most common problems encountered by network administrators in business net-works; by average users connecting to various important services (such as e-mail); or by people who require fundamental networking skills to manage the collection of devices that are typically found in a connected household. This book teaches you the basic principles of computer networking, which can help you solve some of the problems you might encounter in your daily work or play.

Network Type OverviewNetworks are categorized by distribution, size, and architecture. A network can be as simple as a single serial, parallel, or USB cable joining two computers in a peer-to-peer relationship. When you connect a cable between two computers for the purpose of moving your installed software, you are creating a peer-to-peer network. These relationships can be ad hoc, meaning that the network is configured as needed when it is needed. Most people wouldn’t consider two systems connected in this manner to be a network. However, if you had several systems joined in a workgroup and con-nected though a hub, then this would fit the definition of a peer-to-peer network. A workgroup is a collection of computers that do not share a common security database, and where network services can be provided by any member of the workgroup as required.

05 431313-ch01.indd 505 431313-ch01.indd 5 7/31/09 8:59 PM7/31/09 8:59 PM

Part I: Network Basics

6

The smallest networks from a distribution standpoint are personal area networks, which have come to be called pLANs (alternatively abbreviated as PANs). A pLAN is usually applied to a set of periph-eral devices that connect to a single computer system. Bluetooth is a good example of a pLAN. Bluetooth devices are radio frequency connections that use frequency hopping spread spectrum tech-nology (the communication channel constantly changes) that segments the data stream and transmits it over 75 different frequencies with approximately a 30-foot (10-meter) range. Although this kind of network is small in size, pLANs can be quite sophisticated in terms of their technology. Bluetooth has the ability to self-configure, be secured, and advertise each device’s available abilities and services. Some phones, headsets, mice, keyboards, printers, GPS devices, game consoles, and PDAs use Bluetooth technology and are common examples of Bluetooth devices.

Bluetooth certainly fits this book’s definition of a network because it has all of the necessary com-ponents of a network. Bluetooth is discussed in this book because it is something that you have to configure. On the other hand, Universal Serial Bus (USB) can connect up to 127 devices per host controller, but it is self-configuring and is therefore considered a computer bus. All of the afore-mentioned Bluetooth devices can be connected to a computer using a USB connection. So while they are devices on a Bluetooth pLAN, they are more correctly described as peripheral devices. While USB is very capable of transferring data, it is only described as needed in this book.

Cross-RefFor more on USB, see Chapter 11.

A large portion of this book is dedicated to the subject of local area networks, or LANs. The term local is subjective. A LAN is a connected set of systems that spans a single room, floor, or building, and can be as small as a couple of systems connected through a hub. LANs are differentiated by their addressing scheme, as well as by the set of rules or protocols that they use to communicate. Therefore, an AppleTalk and a Netware network are considered to be separate LANs. Heterogeneous networks are common, and so you may find that a LAN has a Windows network with a domain server that contains Macintosh clients and Netware servers. Those Macintosh and Netware systems can still participate on an AppleTalk or Netware network, but the software and addressing used are separate for each particular LAN.

A LAN ceases to be a LAN when the addressing changes in some meaningful way, or when there is a bridging function that links two or more networks. For example, if you had a network of com-puters and chose to give one group of computers one set of related addresses and another group of computers a different set of addresses, then that arrangement would still be considered a LAN. You can do this with Internet Protocol (IP) networking by using a different IP range (192.168.1.x ver-sus 192.168.3.x), or by defining a part of any range as two or more subnets (192.168.1 through 192.168.1.99 and 192.168.1.100 through 192.168.1.199). In either case, this would still be con-sidered a LAN. If you put a couple of routers or bridges, which are intelligent switches, in between the two network types, you would now have a set of distinct networks. The case is even more com-pelling when the connection between the two switches is long or when there are additional switches in between the two that provide entry to the different networks.

05 431313-ch01.indd 605 431313-ch01.indd 6 7/31/09 8:59 PM7/31/09 8:59 PM