Tài liệu MPLS Fundamentals (amazon books)

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MPLS Fundamentals (amazon books)
MPLS Fundamentals Luc De Ghein, CCIE No. 1897 Cisco Press 800 East 96th Street Indianapolis, IN 46240 USA ii MPLS Fundamentals Luc De Ghein Copyright© 2007 Cisco Systems, Inc. Published by: Cisco Press 800 East 96th Street Indianapolis, IN 46240 USA All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher, except for the inclusion of brief quotations in a review. Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 First Printing November 2006 Library of Congress Number: 2004101984 ISBN: 1-58705-197-4 Warning and Disclaimer This book is designed to provide information about Multiprotocol Label Switching (MPLS). Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information is provided on an “as is” basis. The authors, Cisco Press, and Cisco Systems, Inc., shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the discs or programs that may accompany it. The opinions expressed in this book belong to the author and are not necessarily those of Cisco Systems, Inc. Feedback Information At Cisco Press, our goal is to create in-depth technical books of the highest quality and value. Each book is crafted with care and precision, undergoing rigorous development that involves the unique expertise of members from the professional technical community. Readers' feedback is a natural continuation of this process. If you have any comments regarding how we could improve the quality of this book, or otherwise alter it to better suit your needs, you can contact us through e-mail at feedback@ciscopress.com. Please make sure to include the book title and ISBN in your message. We greatly appreciate your assistance. Corporate and Government Sales Cisco Press offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales. For more information, please contact: U.S. Corporate and Government Sales 1-800-382-3419 corpsales@pearsontechgroup.com For sales outside of the U.S. please contact: International Sales 1-317-581-3793 international@pearsontechgroup.com iii Trademark Acknowledgments All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Cisco Press or Cisco Systems, Inc. cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Publisher: Paul Boger Team Coordinator: Vanessa Evans Cisco Representative: Anthony Wolfenden Book Designer: Louisa Adair Cisco Press Program Manager: Jeff Brady Cover Designer: Louisa Adair Executive Editor: Mary Beth Ray Composition: Tolman Creek Managing Editor: Patrick Kanouse Indexer: Tim Wright Development Editor: Allison Beaumont Johnson Project Editor: Seth Kerney Copy Editor: Karen A. Gill Technical Editors: Mohammad Miri, Ivan Pepelnjak, Hari Rakotoranto iv About the Author Luc De Ghein, CCIE No. 1897, is an escalation engineer for Cisco Systems in EMEA. Luc has been in the networking industry for 13 years and has been with Cisco for more than 11 years. He provides escalation support to Cisco engineers worldwide and teaches others about IP routing protocols and MPLS technologies. Luc has been a speaker at several Networkers conferences. During the past 7 years, Luc has specialized in the area of MPLS technologies. Before moving to his current position, Luc was a Technical Assistance Center (TAC) customer support engineer for two and a half years, specializing in routing. He has been an escalation engineer for routing and MPLS technologies for more than eight years. Since 1996, Luc has been a Cisco Certified Internetwork Expert (CCIE). He is certified as both a Routing and Switching CCIE and as a Service Provider CCIE. v About the Technical Reviewers Mohammad Miri is currently employed by Alcatel NA. He has more than 14 years of experience in design and implementation of IP networks for Telecom and Mobile providers involving broadband, narrowband, and MPLS and traffic engineering applications over IP. He received his computer science degree in 1989. Ivan Pepelnjak, CCIE No. 1354, is a 25-year veteran of the networking industry. He has more than 10 years of experience in designing, installing, troubleshooting, and operating large service provider and enterprise WAN and LAN networks and is currently chief technology advisor at NIL Data Communications focusing on advanced IP-based networks and web technologies. His books published by Cisco Press include EIGRP Network Design Solutions and MPLS and VPN Architectures (volumes I and II). Hari Rakotoranto is currently product manager for GMPLS in ITD at Cisco Systems, Inc. He also works closely with service providers and interoperability bodies (ISOCORE and EANTC) in the field of MPLS on technology deployment and overseeing of future directions. Hari has worked as a software engineer and pre- and post-sales technical consultant on different technologies, including Layer 2/3 switches, routing protocols, network management, and UNIX kernel design. He is an active member of ITU-T SG13, focusing mainly on MPLS, MPLS OAM, and MPLS Management. vi Dedication This book is dedicated to my wife Ania, and to my sons Robbe and Lander. vii Acknowledgments I wish to acknowledge a few people who made this book possible. First, I wish to acknowledge my employer Cisco Systems for providing a great working and learning place. Second, I wish to express my gratitude to the technical reviewers, Mohammad Miri, Ivan Pepelnjak, and Hari Rakotoranto, for their feedback, guidance, suggestions, time, and effort in reviewing this book and ensuring its technical accuracy. Third, I'm grateful for the Cisco Press team—Jim Schachterle, Raina Han, Dayna Isley, Mary Beth Ray, Jill Batistick, Karen A. Gill, Seth Kerney, and Allison Johnson—for their support in getting this book published and for their patience with me. Last, but not least, I'd like to thank my family for their support and understanding. viii Contents at a Glance Introduction xxi Part I Fundamentals of MPLS 2 Chapter 1 The Evolution of MPLS 4 Chapter 2 MPLS Architecture 24 Chapter 3 Forwarding Labeled Packets 42 Chapter 4 Label Distribution Protocol 66 Chapter 5 MPLS and ATM Architecture 104 Chapter 6 Cisco Express Forwarding 146 Part II Advanced MPLS Topics 170 Chapter 7 MPLS VPN 172 Chapter 8 MPLS Traffic Engineering 248 Chapter 9 IPv6 over MPLS 328 Chapter 10 Any Transport over MPLS 382 Chapter 11 Virtual Private LAN Service 434 Chapter 12 MPLS and Quality of Service 456 Chapter 13 Troubleshooting MPLS Networks 492 Chapter 14 MPLS Operation and Maintenance 522 Chapter 15 The Future of MPLS 578 Part III Appendixes 586 Appendix A Answers to Chapter Review Questions 588 Index 608 ix Contents Introduction Part I xxi Fundamentals of MPLS 2 Chapter 1 The Evolution of MPLS 4 Definition of MPLS 5 Pre-MPLS Protocols 5 Benefits of MPLS 6 Bogus Benefit 6 The Use of One Unified Network Infrastructure 7 Better IP over ATM Integration 7 BGP-Free Core 8 Peer-to-Peer VPN Model Versus Overlay VPN Model 10 Overlay VPN Model 10 Peer-to-Peer VPN Model 12 Optimal Traffic Flow 16 Traffic Engineering 17 History of MPLS in Cisco IOS 19 Tag Switching to MPLS 19 MPLS Applications 21 Summary 21 Chapter Review Questions 22 Chapter 2 MPLS Architecture 24 Introducing MPLS Labels 25 Label Stacking 26 Encoding of MPLS 27 MPLS and the OSI Reference Model 28 Label Switch Router 29 Label Switched Path 29 Forwarding Equivalence Class 30 Label Distribution 32 Piggyback the Labels on an Existing IP Routing Protocol Running a Separate Protocol for Label Distribution 33 Label Distribution with LDP 34 Label Forwarding Instance Base 35 MPLS Payload 36 MPLS Label Spaces 36 Different MPLS Modes 38 Label Distribution Modes 38 Label Retention Modes 38 LSP Control Modes 39 33 x Summary 40 Chapter Review Questions Chapter 3 40 Forwarding Labeled Packets 42 Forwarding of Labeled Packets 43 Label Operation 43 IP Lookup Versus Label Lookup 44 Load Balancing Labeled Packets 49 Unknown Label 51 Reserved Labels 51 Implicit NULL Label 51 Explicit NULL Label 53 Router Alert Label 53 OAM Alert Label 54 Unreserved Labels 54 TTL Behavior of Labeled Packets 55 TTL Behavior in the Case of IP-to-Label or Label-to-IP TTL Behavior in the Case of Label-to-Label 56 TTL Expiration 57 MPLS MTU 59 MPLS MTU Command 60 Giant and Baby Giant Frames 60 Giant Frames on Switches 61 MPLS Maximum Receive Unit 62 Fragmentation of MPLS Packets 63 Path MTU Discovery 63 Summary 64 Chapter Review Questions 64 Chapter 4 Label Distribution Protocol 66 LDP Overview 68 LDP Operation 69 The Discovery of LSRs That Are Running LDP 69 LDP Session Establishment and Maintenance 73 Number of LDP Sessions 76 Advertising of Label Mappings 77 Label Withdrawing 81 Housekeeping by Means of Notification 83 Targeted LDP Session 84 LDP Authentication 86 Controlling the Advertisement of Labels via LDP 87 MPLS LDP Inbound Label Binding Filtering 90 LDP Autoconfiguration 92 MPLS LDP-IGP Synchronization 93 55 xi How MPLS LDP-IGP Synchronization Works 95 MPLS LDP-IGP Synchronization Configuration 95 MPLS LDP Session Protection 100 Summary 103 Chapter Review Questions 103 Chapter 5 MPLS and ATM Architecture 104 Brief Introduction to ATM 106 Label Encoding 110 Label Advertisement 111 Downstream-on-Demand Label Advertisement LDP Control Mode for ATM 122 LDP for LC-ATM 124 Label Space 124 Loop Detection by LDP 125 Loop Detection by Hop Count TLV 125 TTL Manipulation 127 Loop Detection by Path Vector TLV 129 LDP Address Messages 130 Blocking Label Requests 130 Aggregate Labels 131 VC-Merge 132 Non MPLS-Aware ATM Switches 135 Label Switch Controller 138 Multi-Virtual Circuit Tagged Bit Rate 139 MPLS CoS 142 Frame Mode ATM 143 Reducing the Number of LVCs 144 Summary 145 Chapter Review Questions 145 Chapter 6 Cisco Express Forwarding 146 Overview of Cisco IOS Switching Methods 147 Process Switching 148 Fast Switching 148 CEF Switching 149 Why Is CEF Needed in MPLS Networks? 149 What Are the Components of CEF? 150 The Adjacency Table 151 The CEF Table 152 Operation of CEF 153 Distributed CEF (DCEF) 154 CEF Switching Packets in Hardware 155 116 xii Load Balancing in CEF 156 Unequal Cost Load Balancing 159 Labeling IP Packets by CEF 161 Load Balancing Labeled Packets 163 Troubleshooting CEF 164 Summary 167 Chapter Review Questions 168 Part II Advanced MPLS Topics 170 Chapter 7 MPLS VPN 172 Introduction to MPLS VPN 173 Definition of a VPN 173 VPN Models 174 MPLS VPN Model 174 Architectural Overview of MPLS VPN 176 Virtual Routing Forwarding 176 RD 179 RTs 180 VPNv4 Route Propagation in the MPLS VPN Network Packet Forwarding in an MPLS VPN Network 187 BGP 188 BGP Multiprotocol Extensions and Capabilities 189 BGP Extended Community: RT 192 VPNv4 Routes 193 BGP Carrying the Label 194 RRs 197 RR Group 198 BGP Route Selection 200 BGP Multipath 200 Using Multiple RDs 203 Packet Forwarding 204 PE-CE Routing Protocols 207 Connected Routes 207 Static Routing 208 RIP Version 2 208 OSPF 209 OSPF VRF Configuration 211 OSPF Metric Propagation 213 BGP Extended Communities for OSPF 214 OSPF Network Design 215 Sham Link 216 Down Bit and Domain Tag 219 EIGRP 220 Configuration 222 185 xiii Pre-Bestpath POI 223 EIGRP PE-CE with Backdoor Links 225 IS-IS 226 eBGP 230 Autonomous System Override 231 allowas-in 232 Hub-and-Spoke 233 SOO 235 VRF Access 237 Internet Access 237 Internet in a VPN 237 Internet Access Through the Global Routing Table 238 Internet Access Through the Global Routing Table with Static Routes Internet Access Through a Central VRF Site 240 Multi-VRF CE 241 OSPF VRF-Lite Command 243 CE Management 243 Summary 246 Chapter Review Questions 246 Chapter 8 MPLS Traffic Engineering 248 The Need for MPLS TE 249 Overview of the Operation of MPLS TE 252 Distribution of TE Information 255 Requirements for the IGP 255 OSPF Extensions for TE 256 IS-IS Extensions for TE 261 Flooding by the IGP 264 Routing and Cost of a TE LSP 266 Link TE Attributes 266 Maximum Reservable Bandwidth 267 Attribute Flags 267 TE Metric 267 Shared Risk Link Groups 268 Maximum Reservable Sub-Pool Bandwidth MPLS TE Tunnel (Trunk) Attributes 268 TE Tunnel Path Calculation 269 Path Setup Option 269 IP Explicit Address Exclusion 272 Setup and Holding Priority 273 Reoptimization 274 Periodic Reoptimization 274 Event-Driven Reoptimization 275 Manual Reoptimization 275 268 239 xiv Dual TE Metrics 275 PCALC 279 RSVP 279 RSVP and Labels 280 Record Route Object 282 Other Information Carried by RSVP 284 Putting It All Together 285 Shared Explicit Style 288 RSVP Messages 289 PathTear 289 ResvTear 289 PathErr 289 ResvErr 290 Link Manager 290 FRR 291 FRR—Link Protection 292 FRR—Node Protection 297 SRLG Used by Backup Tunnels 302 Multiple Backup Tunnels 303 Forwarding Traffic onto MPLS TE Tunnels 303 Static Routing 304 Policy-Based Routing 304 Autoroute Announce 305 Forwarding Adjacency 306 Direct Mapping of AToM Traffic onto TE Tunnels 309 Class-Based Tunnel Selection 309 Cost Calculation of IGP Routes over TE Tunnels 311 Default Cost Calculation 311 Adjusting the Cost Calculation 319 Load Balancing 320 MPLS TE and MPLS VPN 321 TE Tunnels Between PE Routers 321 TE Tunnel with P Router as Tail End Router 321 VRF-to-TE Tunnel Routing 324 Summary 325 Chapter Review Questions 326 Chapter 9 IPv6 over MPLS 328 Introduction to IPv6 329 The Driving Forces for IPv6 329 Overview of the IPv6 Protocol 330 The IPv6 Header 330 The IPv6 Addressing 332 Other IPv6 Novelties 333 xv Overview of IPv6 Unicast Routing in Cisco IOS 334 IPv6 RIP (RIPng) 334 OSPF for IPv6 or OSPFv3 337 IS-IS for IPv6 342 EIGRP for IPv6 345 Multiprotocol BGP Extensions for IPv6 348 CEFv6 351 Carrying IPv6 over an MPLS Backbone 352 MPLS VPN Network Using IPv6 over IPv4 Tunnels on the CE Routers Carrying IPv6 over an MPLS Backbone (6PE) 354 Operation of 6PE 355 Configuration of 6PE 358 Verifying 6PE Operation 361 Carrying IPv6 in VPNs Across an MPLS Backbone (6VPE) 364 Operation of 6VPE 364 Configuration of 6VPE 366 Verifying 6VPE Operation 372 IPv6 Internet Access Through 6VPE 377 Supported Features for 6VPE 378 Remarks for Both 6PE and 6VPE 378 Route Reflectors 378 Turning Off TTL Propagation on the PE Routers 379 Load Balancing Labeled IPv6 Packets 379 PHP 379 BGP Functionality 379 Summary 380 Chapter Review Questions 380 Chapter 10 Any Transport over MPLS 382 Understanding the Need for AToM 384 Transporting Layer 2 Frames 384 AToM Architecture 386 Data Plane of AToM 387 Signaling the Pseudowire 388 C-Bit 390 PW Type 390 Group ID 391 PW ID 392 Interface Parameters 392 Signaling the Status of the Pseudowire The Control Word 393 Control Word Functions 394 Pad Small Packets 394 392 353 xvi Carry Control Bits of the Layer 2 Header of the Transported Protocol 394 Preserve the Sequence of the Transported Frames 395 Facilitate the Correct Load Balancing of AToM Packets in the MPLS Backbone Network 396 Facilitate Fragmentation and Reassembly 396 MPLS MTU in the MPLS Backbone 397 The Basic AToM Configuration 398 Transported Layer 2 Protocols 402 HDLC 402 PPP 403 Frame Relay 403 DLCI-to-DLCI 403 Port-to-Port Mode (Port Trunking) 405 ATM 408 ATM AAL5 408 ATM Cell Relay 411 Single Cell Relay Mode 411 Packed Cell Relay Mode 414 Ethernet 416 Ethernet Frame Format 416 EoMPLS Forwarding 417 VLAN ID Rewrite 418 EoMPLS Scenario Examples 418 Dot1q Tunneling (QinQ) over AToM 424 AToM Tunnel Selection 426 AToM and QoS 429 Summary 432 Chapter Review Questions 432 Chapter 11 Virtual Private LAN Service 434 The Need for VPLS 435 VPLS Architecture 437 VPLS Data Plane 439 VPLS Signaling 440 The Basic VPLS Configuration 441 Verifying the VPLS Operation 443 VPLS and Tunneling Layer 2 Protocols 446 Tunneling Cisco Discovery Protocol 446 Tunneling Spanning Tree Protocol 447 Trunk Port Between the CE and PE 449 Hierarchical VPLS 450 H-VPLS with Dot1q Tunneling (QinQ) in the Access Layer H-VPLS with MPLS in the Access Layer 452 450 xvii Quality of Service 452 Limiting MAC Addresses 454 Routing Peering 454 Summary 455 Chapter Review Questions 455 Chapter 12 MPLS and Quality of Service 456 DiffServ with IP Packets 458 DiffServ with MPLS Packets 461 Default MPLS QoS Behavior in Cisco IOS 462 DiffServ Tunneling Models 466 Pipe Model 467 Short Pipe Model 467 Uniform Model 468 Advantages of the DiffServ Tunneling Models 469 How to Implement the Three DiffServ Tunneling Models 472 Recoloring the Packet 472 MQC Commands for MPLS QoS 475 Moving MPLS QoS from the PE to the CE Router 480 Implementing the DiffServ Tunneling Models in Cisco IOS 482 The Table-Map Feature 487 The Use of MPLS QoS for Ethernet over MPLS 490 Summary 490 Chapter Review Questions 491 Chapter 13 Troubleshooting MPLS Networks 492 Label Stack Depth 493 Verifying Label Switched Path 494 Tracerouting in MPLS Networks 495 Tracerouting in an IP Network 495 Label-Aware ICMP 497 TTL Behavior in MPLS Networks 498 Tracerouting in MPLS Networks 499 Problems with Tracerouting in MPLS Networks 503 mpls ip ttl-expiration pop Command 504 no mpls ip propagate-ttl 505 MPLS MTU 510 Ping 511 Debug MPLS Packets 511 Debugging Load Balancing of Labeled Packets 514 Verifying MPLS on the Interface 516 Verifying Number of Bytes Label Switched 517 xviii MPLS-Aware Netflow 518 Summary 521 Chapter Review Questions 521 Chapter 14 MPLS Operation and Maintenance 522 Requirements of MPLS OAM 523 Detection and Diagnosis of Control and Data Plane Defects 524 Detection of a Defect in a Label Switched Path (LSP) 524 OAM Packets Flowing on the Same Path as MPLS Data Traffic 525 Path Characterization 525 Measurement of SLAs 525 OAM Interworking 526 MIBs 526 Accounting 526 Router Alert Option and Router Alert Label 526 Router Alert Label 528 OAM Alert Label 529 MPLS LSP Ping 529 LSP Ping Protocol Details 531 Target FEC Stack 534 Downstream Mapping 536 Interface and Label Stack TLV 538 Errored TLVs TLV 539 Reply TOS Byte 539 LSP Ping Operation 539 LSP Verification 540 MPLS Ping in Cisco IOS 541 MPLS LSP Traceroute 545 MPLS Traceroute in Cisco IOS 546 Router Alert Label 551 Load Balancing 552 VCCV 555 IP Service Level Agreement 558 VRF-Aware IP SLA 561 Netflow Accounting 563 SNMP/MIBs 564 Context-Based Access for SNMP over MPLS VPN 571 MPLS VPN MIBs 572 Syslog 573 OAM Message Mapping 575 Summary 577 Chapter Review Questions 577 xix Chapter 15 The Future of MPLS 578 New MPLS Applications 579 Work at IETF 580 MPLS Control Word 580 FCS Retention 581 AToM Fragmentation and Reassembly Circuit Emulation 581 GMPLS 582 OAM Protocols 582 MPLS Labeled Multicast 584 The Proliferation of MPLS 584 Summary 585 581 Part III Appendixes 586 Appendix A Answers to Chapter Review Questions Index 608 588
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