Administering Cisco QoS for IP Network

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We would like to acknowledge the following people for their kindness and support in making this book possible. Richard Kristof, Duncan Anderson, David Marini, Jennifer Gould, Kevin Murray, Dale Leatherwood, Laura Cervoni, and Rhonda Harmon of Global Knowledge, for their generous access to the IT industry’s best courses, instructors, and training facilities. Ralph Troupe, Rhonda St. John, Emlyn Rhodes, and the team at Callisma for their invaluable insight into the challenges of designing, deploying and supporting worldclass enterprise networks....

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  1. WINT A I L PALMA Vx ! DE A S ON B CK ADMINISTERING C INETWORKS S C O QoS ® IP IN “This book provides comprehensive, in-depth explanations FREE Palm OS Version and configurations necessary to implement QoS in today's of Book advanced, multiservice Cisco networks.” —Ralph Troupe, President and CEO, Callisma FREE Downloadable HTML FREE MP3 Audio Files TECHNICAL EDITOR: Michael E. Flannagan, CCNA, CCDA Benoit Durand, CCIE #5754 Jerry Sommerville, CCIE #1293 Mark Buchmann, CCIE #3556 Ron Fuller, CCIE #5851
  2. With over 1,500,000 copies of our MCSE, MCSD, CompTIA, and Cisco study guides in print, we have come to know many of you personally. By listening, we've learned what you like and dislike about typical computer books. The most requested item has been for a web-based service that keeps you current on the topic of the book and related technologies. In response, we have created, a service that includes the following features: s A one-year warranty against content obsolescence that occurs as the result of vendor product upgrades. We will provide regular web updates for affected chapters. s Monthly mailings that respond to customer FAQs and provide detailed explanations of the most difficult topics, written by content experts exclusively for s Regularly updated links to sites that our editors have determined offer valuable additional information on key topics. s Access to “Ask the Author”™ customer query forms that allow readers to post questions to be addressed by our authors and editors. Once you’ve purchased this book, browse to To register, you will need to have the book handy to verify your purchase. Thank you for giving us the opportunity to serve you.
  4. Syngress Publishing, Inc., the author(s), and any person or firm involved in the writing, editing, or production (collectively “Makers”) of this book (“the Work”) do not guarantee or warrant the results to be obtained from the Work. There is no guarantee of any kind, expressed or implied, regarding the Work or its contents. The Work is sold AS IS and WITHOUT WARRANTY. You may have other legal rights, which vary from state to state. In no event will Makers be liable to you for damages, including any loss of profits, lost savings, or other inci- dental or consequential damages arising out from the Work or its contents. Because some states do not allow the exclusion or limitation of liability for consequential or incidental damages, the above limitation may not apply to you. You should always use reasonable case, including backup and other appropriate precautions, when working with computers, networks, data, and files. Syngress Media® and Syngress® are registered trademarks of Syngress Media, Inc. “Career Advancement Through Skill Enhancement™,” “Ask the Author™,” “Ask the Author UPDATE™,” “Mission Critical™,” and “Hack Proofing™” are trademarks of Syngress Publishing, Inc. Brands and product names mentioned in this book are trademarks or service marks of their respective companies. KEY SERIAL NUMBER 001 ALKJD48753 002 LERQAR9T83 003 ERQ395E932 004 45BHSKERF3 005 SLDFAPW93V 006 LWE432532R 007 36FCBFGK454 008 NVCW5DGK43 009 FJA495G8N3 010 4U34BRA395 PUBLISHED BY Syngress Publishing, Inc. 800 Hingham Street Rockland, MA 02370 Administering Cisco QoS for IP Networks Copyright © 2001 by Syngress Publishing, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the Copyright Act of 1976, no part of this publication may be reproduced or dis- tributed in any form or by any means, or stored in a database or retrieval system, without the prior written per- mission of the publisher, with the exception that the program listings may be entered, stored, and executed in a computer system, but they may not be reproduced for publication. Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 ISBN: 1-928994-21-0 Co-Publisher: Richard Kristof Freelance Editorial Manager: Maribeth Corona-Evans Technical edit by: Michael E. Flannagan Index by: Robert A. Saigh Technical Review by: Mark Buchmann Copy edit by: Beth Roberts and Juli Smith Acquisitions Editor: Catherine B. Nolan Page Layout and Art by: Shannon Tozier Distributed by Publishers Group West
  5. Acknowledgments We would like to acknowledge the following people for their kindness and support in making this book possible. Richard Kristof, Duncan Anderson, David Marini, Jennifer Gould, Kevin Murray, Dale Leatherwood, Laura Cervoni, and Rhonda Harmon of Global Knowledge, for their generous access to the IT industry’s best courses, instructors, and training facilities. Ralph Troupe, Rhonda St. John, Emlyn Rhodes, and the team at Callisma for their invaluable insight into the challenges of designing, deploying and supporting world- class enterprise networks. Karen Cross, Lance Tilford, Meaghan Cunningham, Kim Wylie, Harry Kirchner, Bill Richter, Kevin Votel, Brittin Clark, and Sarah MacLachlan of Publishers Group West for sharing their incredible marketing experience and expertise. Mary Ging, Caroline Hird, Simon Beale, Caroline Wheeler,Victoria Fuller, Jonathan Bunkell, and Klaus Beran of Harcourt International for making certain that our vision remains worldwide in scope. Anneke Baeten, Annabel Dent, and Laurie Giles of Harcourt Australia for all their help. David Buckland,Wendi Wong, Daniel Loh, Marie Chieng, Lucy Chong, Leslie Lim, Audrey Gan, and Joseph Chan of Transquest Publishers for the enthusiasm with which they receive our books. Kwon Sung June at Acorn Publishing for his support. Ethan Atkin at Cranbury International for his help in expanding the Syngress program. Joe Pisco, Helen Moyer, and the great folks at InterCity Press for all their help. v
  6. From Michael E. Flannagan, Technical Editor A world of thanks to the Cisco RTP Routing Protocols Team for an unbelievable amount of knowledge, experience, assistance, and fun…you guys are the best! Thanks to Matt Carling (Cisco Systems, Australia) for his assistance with our MPLS chapter. Special thanks to Shannon Brown (Cisco Systems,TAC) for her knowledge and especially her patience back in the days when I could hardly spell “router.” And, of course, I’ll be disowned if I don’t say…Hi mom! vi
  7. From Global Knowledge At Global Knowledge we strive to support the multiplicity of learning styles required by our students to achieve success as technical professionals. As the world's largest IT training company, Global Knowledge is uniquely positioned to offer these books.The expertise gained each year from providing instructor-led training to hundreds of thousands of students world-wide has been captured in book form to enhance your learning experience.We hope that the quality of these books demonstrates our commitment to your lifelong learning success. Whether you choose to learn through the written word, computer based training, Web delivery, or instructor-led training, Global Knowledge is committed to pro- viding you with the very best in each of these categories. For those of you who know Global Knowledge, or those of you who have just found us for the first time, our goal is to be your lifelong competency partner. Thank your for the opportunity to serve you.We look forward to serving your needs again in the future. Warmest regards, Duncan Anderson President and Chief Executive Officer, Global Knowledge vii
  8. Technical Editor Michael E. Flannagan (CCNA, CCDA) is a Network Consulting Engineer in the Network Supported Accounts (NSA) Group at Cisco Systems and is a team lead for the MPLS/QoS Virtual Team. His experi- ence includes extensive work with Routing Protocol and Quality of Service support for customer networks. Prior to joining Cisco Systems, he worked as an enterprise network architect and as a consultant specializing in Quality of Service. Mike’s Quality of Service testing and research was used to recommend the implementation of various QoS mechanisms for one of the world’s largest pharmaceutical companies and he has partici- pated in large-scale QoS designs for several major US companies. In addi- tion to holding various certifications from Cisco, 3Com, and Nortel Networks, Mike has passed both the CCIE Routing/Switching and the CCIE Design written exams and is currently preparing for his CCIE Lab exams. He lives in Morrisville, NC. Technical Reviewer Mark Buchmann (CCIE#3556, CCSI) is a Cisco Certified Internetworking Expert and has been a Certified Cisco Systems Instructor since 1995. He is the owner of MAB Enterprises, Inc., a com- pany providing consulting, network support, training, and various other services. Mark is also a co-owner of, a company pro- viding on-line certification assistance for a variety of network career paths including all the various Cisco certifications. Mark is Series Editor for Syngress Media’s Cisco Certification Study Guides. In his free time he enjoys spending time with his family and boating. He currently lives in Raleigh, NC. viii
  9. Contributors Benoit Durand (CCIE #5754, CCNA, CCDA, CCNP, CCDP) is the Midwest Region Network Engineer for Tivoli Systems ( located in Indianapolis, IN. Ben designs and integrates high-end network solutions for Tivoli’s worldwide operations while maintaining his own Cisco-powered network in Indianapolis. He has over 10 years of net- working engineering experience in a wide range of environments. Prior to working at Tivoli, Ben worked on many high-profile military projects for the Canadian Air Force, deploying wide-area network solutions to peacekeeping forces in Kuwait,Yugoslavia, and other international loca- tions. His latest projects involve Voice-over-ATM,Virtual Private Network solutions, and Wide-Area Network switching. Ben lives with his wife Dr. Christy Snider in Kingston, GA. Ron Fuller (CCIE #5851, CCNP-ATM, CCNP-Voice, CCNP-Security, CCDP, MCNE) is a Senior Systems Engineer with 3X Corporation. He currently provides network design and implementation services to 3X Corporation clients in the Eastern United States. His specialties include Cisco LAN/WAN design, security consultation, and Novell network design. He has held senior engineer positions for two other network con- sulting companies in the past nine years. Ron also contributed to Syngress’ Building Cisco Remote Access Networks (1-928994-13-X). He currently resides in Sunbury, OH with his wife, Julie, and his yet-to-be-born baby. Jerry Sommerville (CCIE #1293) is a Senior Consultant for Callisma. His background includes network management, system management, system integration, network support and planning, user training, proce- dure automation, and program analysis. Jerry holds a Master of Science in Computer Aided Design & Computer Aided Manufacturing from Eastern Michigan University and a Bachelor of Science in Industrial Technology and Engineering from Texas A & M University. ix
  10. James Placer (CCDP, CCNP Security,Voice Access, NNCDS, NNCSS, MCSE) is a Senior Network Design Engineer at Interactive Business Systems, Inc. in the Enterprise Networking Group ( He designs, troubleshoots, and implements large-scale LAN and WAN networks based primarily on Cisco Systems and Nortel Networks plat- forms. James previously contributed to the Syngress CCNP Support Study Guide for Exam 640-506 and has over 14 years of experience in the net- working and computer systems field. He currently resides with his wife Kathy just outside the town of Allegan, MI. Kevin Davis (CCNA, MCSE, MCP+I) is a Consultant with Callisma where he consults with Service Providers and enterprise clients on var- ious networking issues. Formerly, Kevin was a consultant with International Network Services in Raleigh, NC working with Service Providers in the Research Triangle Park (RTP). He graduated with a degree in Computer Engineering from the Dwight Look College of Engineering at Texas A&M University in College Station,TX. Kevin also contributed to Syngress’ Building Cisco Remote Access Networks (1-928994-13-X) and has written several whitepapers on minimizing computer viruses in a network environment and browser security. He lives in McKinney,TX. Paul Salas (CCNA, MCT, MCSE, Network+) is a Senior Network Engineer for Fleet Mortgage Corporation. Paul designs and manages Fleet’s internetwork infrastructure, which consists of a wide variety of networking equipment from an assortment of vendors. He currently is involved in implementing a high-end Web network solution. He is also a part-time technical instructor for Microstaff Corporation where he delivers Microsoft Official Curriculum for the Windows 2000 track. Paul lives in Columbia, SC with his family. He would like to dedicate his writ- ings to his wife, Margaret, for tolerating his “hair on fire” work pace and to his two children, Michael and Allison, Mountains are conquered one step at a time. x
  11. Jeff Corcoran (CCNA, MCSE, CNE) is a Senior Network Consultant for Siemens Enterprise Networks, Inc. where he is a network planner in the Ford Motor Company Advanced Network Technologies group. He is responsible for global network planning and testing of emerging network technologies and their application to the Ford Intranet. He has a special focus on VoIP, QoS, high availability architectures, and multicast. Jeff holds a Bachelors of Science in Physics and Applied Mathematics from the University of Toledo. He lives in Dearborn, MI. Lisa Giebelhaus (CCNA) is a Senior Consultant with Callisma. She has been in the Telecommunications field for eight years. Her main focus has been designing, implementing, and managing projects for large-scale enter- prise networks. Prior to joining Callisma, Lisa was a Senior Consultant for Lucent NetworkCare Professional Services (formerly INS) in Detroit, MI. She graduated from Michigan State University with a Bachelor of Science degree in Engineering Arts. She lives in Royal Oak, MI. Richard Hamilton is a Senior Consultant with Callisma. He is currently responsible for leading engineering teams in the design and implementa- tion of complex networks for service providers. Richard is industry rec- ognized as a subject matter expert in MPLS, ATM, and Frame Relay switching. Richard has spent 14 years providing technical services in the financial and service provider industries for companies including NatWest Bank, Fleet Bank, International Network Services, Lucent Technologies, Cisco Systems, Sprint,WorldCom, South Western Bell, GTE, CapRock, CTC Communications, ILD Telecommunications, and Triton PCS. Richard also contributed to Syngress Publishing’s Building Cisco Remote Access Networks (1-928994-13-X). He lives in Flower Mound,TX. xi
  12. Robert Melancon is a Consultant with Callisma. His recent projects involve the maintenance of a 400+ site LAN/WAN implementing TCP/IP, Frame Relay, 3COM hubs, Cisco Catalyst 1900 series switches, and Cisco 2500 series routers. He has also worked on proof of concept and certification of xDSL and WAN technologies and vendor equipment including Promatory and Pairgain DSLAMs and Nortel and Lucent WAN switches. Robert has also developed many training programs and docu- mentation. He has a degree in engineering from Southern Methodist University and lives in Dallas,TX. xii
  13. Contents Foreword xxiii Chapter 1 Cisco IOS Feature Review 1 Introduction 2 IP Address Classes and Classful IP Routing 2 Classes A, B, and C 5 Class D Addresses (Multicast) 8 RIPv1 and IGRP 10 RIPv1 11 IGRP 13 Variable-Length Subnet Mask (VLSM) Review 17 Why Do We Need VLSM? 19 Common Uses for Subnetting 20 Standard Access Control Lists (ACLs) 21 Filtering Traffic 24 Configuration Examples 25 Extended Access Control Lists (ACLs) 25 Benefits of Extended ACLs 30 Common Ports Used with Extended ACLs 30 Configuration Examples 32 Network Address Translation (NAT) 35 Controlling NAT with ACLs 39 Dynamic versus Static Translations 39 Configuration Example 40 Route Maps 40 Where to Use Route Maps 41 Controlling Traffic with Route Maps 41 Configuration Example 41 Summary 43 FAQs 44 Chapter 2 EIGRP A Detailed Guide 47 Introduction 48 Reviewing Basic Concepts of IGRP 48 xiii
  14. xiv Contents How Does EIGRP Work? 50 Using Distance Vectors for Path Selection 50 Defining the Four Basic Components of EIGRP 57 Establishing Protocol-Dependent Modules 57 Establishing Neighbor Discovery/Recovery 58 Managing Reliable Transport Protocol 59 Establishing DUAL Finite State Machine 59 Implementing Packet Types 60 Configuring EIGRP’s Distributed Update Algorithm (DUAL) 64 Choosing a Path Selection 64 Handling Failure and Recovery 72 Configuring Basic EIGRP 75 Verifying Configuration with Show Commands 84 Configuring Advanced EIGRP 87 Summarizing EIGRP Addresses 88 Redistributing EIGRP and OSPF 97 Unequal Cost Load Balancing 103 Recognizing Caveats 108 Stuck-in-Active 108 Auto-Summarization 109 Troubleshooting EIGRP 110 Troubleshooting Stuck-in-Active Routes 110 Troubleshooting Auto-Summarization 115 Troubleshooting not-on-common-subnet 117 Summary 119 FAQs 120 Chapter 3 Introduction to Quality of Service 123 Introduction 124 Defining Quality of Service 124 What Is Quality of Service? 125 Applications for Quality of Service 126 Three Levels of QoS 127 Understanding Congestion Management 129 Defining General Queuing Concepts 130 Leaky Bucket 131 Tail Drop 132 Token Bucket 133 First In First Out Queuing 134 Fair Queuing 136 Priority Queuing 138 Custom Queuing 139
  15. Contents xv Understanding Congestion Avoidance 141 Congestion Avoidance in Action 142 Pros and Cons of Congestion Avoidance 142 Introducing Policing and Traffic Shaping 143 Traffic Shaping 144 Generic Traffic Shaping 145 Frame Relay Traffic Shaping 145 Summary 145 FAQs 146 Chapter 4 Traffic Classification Overview 147 Introduction 148 Introducing Type of Services (ToS) 148 ToS Service Profile 150 Defining the Seven Levels of IP Precedence 151 Explaining Integrated Services 152 Defining the Parameters of QoS 154 Admission Requirements 155 Resource Reservation Requirements 156 Packet Classification 156 Packet Scheduling 156 Introducing Resource Reservation Protocol (RSVP) 156 RSVP Traffic Types 157 RSVP Operation 157 RSVP Messages 158 Reservation-Request Messages 158 Path Messages 158 Error and Confirmation Messages 159 Teardown Messages 159 Introducing Differentiated Service (DiffServ) 161 The DiffServ Code Point (DSCP) 162 Per Hop Behavior (PHB) 163 Best Practice Network Design 165 Expanding QoS: Cisco Content Networking 168 Application Aware Classification: Cisco NBAR 169 HTTP Classification 169 Citrix Classification 170 Supported Protocols 170 PDLM 174 NBAR Supported QoS Services 174 NBAR and Content Network Design Guidelines 175 Summary 176 FAQs 178
  16. xvi Contents Chapter 5 Configuring Traffic Classification 181 Introduction 182 Configuring Policy-based Routing (PBR) 182 Using PBR to Route Specific Packet Types 184 Defining Committed Access Rate (CAR) 185 Configuring Distributed CAR (DCAR) 188 Marking and Transmitting Web Traffic 188 Remarking the Precedence Bit and Transmitting Web Traffic 189 Marking and Transmitting Multilevels of CAR 190 Marking and Rate Limiting ISPs 191 Rate Limiting by Access List 193 Using CAR to Match and Limit by MAC Address 194 Monitoring CAR 196 Configuring Cisco Express Forwarding 196 Enabling CEF 197 Monitoring CEF 198 Troubleshooting Cisco Express Forwarding Caveats and Bugs 200 Configuring Basic Network-based Application Recognition (NBAR) 201 Creating an NABR Class Map 202 Creating a Policy Map 203 Applying the Policy Map to an Interface 203 Configuring Complex NBAR 204 Integrating NBAR with Class-based Weighted Fair Queuing 206 Creating a Class Map to Identify NBAR 207 Configuring Class Policy in the Policy Map 207 Attaching the Policy to an Interface 208 Configuring NBAR with Random Early Detection 209 Configuring System Network Architecture Type of Service 211 Mapping SNA CoS to IP ToS 211 Prioritizing SNA Traffic 212 Summary 213 FAQs 215 Chapter 6 Queuing and Congestion Avoidance Overview 217 Introduction 218 Using FIFO Queuing 218 High Speed versus Low Speed Links 220 When Should I Use FIFO? 220 Using Priority Queuing 221 How Does Priority Queuing Work? 221
  17. Contents xvii Queue Sizes 222 Why Do I Need Priority Queuing on My Network? 222 Using Custom Queuing 224 How Does Custom Queuing Work? 224 Queue Sizes 226 Protocol Interactions with Custom Queuing 226 Why Do I Need Custom Queuing on My Network? 227 Using Weighted Fair Queuing (WFQ) 228 How Does Weighted Fair Queuing Work? 228 Where Does the Weight Factor Come into Play? 230 Resource Reservation Protocol (RSVP) 231 Why Do I Need Weighted Fair Queuing on My Network? 231 Using Random Early Detection (RED) 232 How Does Random Early Detection Work? 232 TCP/IP Sliding Window 233 Why Do I Need Random Early Detection on My Network? 235 Summary 235 FAQs 236 Chapter 7 Configuring Queuing and Congestion Avoidance 239 Introduction 240 Configuring FIFO Queuing 240 Enabling FIFO 240 Verifying FIFO Operations 242 FIFO with RED 243 Configuring Priority Queuing 244 Enabling Priority Queuing 244 A Closer Look at the Protocol Classification 245 Applying Your Priority List to an Interface 247 Configuring the Queue Limits 247 Verifying Your Configuration 248 Troubleshooting Priority Queuing 250 Configuring Custom Queuing 252 Enabling Custom Queuing 252 Adjusting Byte Counts and Queue Sizes 254 Applying Your Configuration to an Interface 254 Verifying Your Configuration 255 Troubleshooting Custom Queuing 257 Configuring Weighted Fair Queuing 259 Enabling Weighted Fair Queuing 259 Verifying Your Configuration 260 Troubleshooting Weighted Fair Queuing 262
  18. xviii Contents Configuring Random Early Detection 263 Enabling Random Early Detection 263 RED with Other Queuing Mechanisms 264 Verifying Your Configuration 266 Troubleshooting Random Early Detection 267 Summary 267 FAQs 268 Chapter 8 Advanced QoS Overview 271 Introduction 272 Using the Resource Reservation Protocol (RSVP) 272 What Is RSVP? 273 What RSVP Is Not 275 How Does RSVP Work? 275 Session Startup 276 Session Maintenance and Tear-Down 278 What Kind of QoS Can I Request with RSVP? 279 Reservation Styles and Merging Flows 280 Why Do I Need RSVP on My Network? 282 Advantages of Using RSVP 283 Disadvantages of Using RSVP 283 Using Class-Based Weighted Fair Queuing (CBWFQ) 284 How Does CBWFQ Work? 284 Why Do I Need CBWFQ on My Network? 286 RSVP in Conjunction with CBWFQ 290 Using Low Latency Queuing (LLQ) 291 How Does LLQ Work? 291 Classifying Priority Traffic 292 Allocating Bandwidth 292 Limitations and Caveats 294 Why Do I Need LLQ on My Network? 294 Using Weighted Random Early Detection (WRED) 295 How Does WRED Work? 295 WRED and IP Precedence 296 WRED and RSVP 297 WRED Algorithm 297 Why Do I Need WRED on My Network? 298 Using Generic Traffic Shaping and Frame Relay Traffic Shaping 299 Token Bucket 299 How Does GTS Work? 301 Why Do I Need GTS on My Network? 301 How Does FRTS Work? 303 Why Do I Need FRTS on My Network? 305
  19. Contents xix Running in Distributed Mode 307 Features Supported in Distributed Mode 307 IOS Versions 308 Operational Differences 308 Restrictions 308 Using Link Fragmentation and Interleaving 309 How Does LFI Work? 311 LFI with Multilink Point-to-Point Protocol 312 How Can This Be Useful on My Network? 313 Understanding RTP Header Compression 313 How Does RTP Header Compression Work? 314 When Would I Need RTP Header Compression? 315 Summary 315 FAQs 318 Chapter 9 Configuring Advanced QoS 321 Introduction 322 Enabling, Verifying, and Troubleshooting Resource Reservation Protocol (RSVP) 322 Enabling RSVP 324 Verifying Your RSVP Configuration 324 Troubleshooting RSVP 327 Enabling, Verifying, and Troubleshooting Class-Based Weighted Fair Queuing (CBWFQ) 328 Enabling CBWFQ 328 Defining Class Maps 328 Creating Policies 330 Attaching Policies to Interfaces 334 Verifying Your CBWFQ Configuration 334 Troubleshooting CBWFQ 336 Configuring, Verifying, and Troubleshooting Low Latency Queuing (LLQ) 337 Configuring LLQ 337 Verifying Your LLQ Configuration 338 Troubleshooting LLQ 339 Configuring, Verifying, and Troubleshooting Weighted Random Early Detection (WRED) 340 Configuring WRED 340 Verifying Your WRED Configuration 343 Troubleshooting WRED 348 Configuring and Verifying Generic Traffic Shaping (GTS) and Frame Relay Traffic Shaping (FRTS) 349 Configuring GTS 351 Verifying Your GTS Configuration 352



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