MPLS Fundamentals - Lagout
MPLS FundamentalsLuc De Ghein, CCIENo. 1897Cisco Press800 East 96th StreetIndianapolis, IN 46240 USA
iiMPLS FundamentalsLuc De GheinCopyright 2007 Cisco Systems, Inc.Published by:Cisco Press800 East 96th StreetIndianapolis, IN 46240 USAAll rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic ormechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission fromthe 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 0First Printing November 2006Library of Congress Number: 2004101984ISBN: 1-58705-197-4Warning and DisclaimerThis book is designed to provide information about Multiprotocol Label Switching (MPLS). Every effort has been made to make thisbook 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 norresponsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or fromthe 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 InformationAt 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 ofthis book, or otherwise alter it to better suit your needs, you can contact us through e-mail at feedback@ciscopress.com. Please makesure to include the book title and ISBN in your message.We greatly appreciate your assistance.Corporate and Government SalesCisco 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.comFor sales outside of the U.S. please contact:International com
iiiTrademark AcknowledgmentsAll terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Cisco Pressor Cisco Systems, Inc. cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affectingthe validity of any trademark or service mark.Publisher: Paul BogerTeam Coordinator: Vanessa EvansCisco Representative: Anthony WolfendenBook Designer: Louisa AdairCisco Press Program Manager: Jeff BradyCover Designer: Louisa AdairExecutive Editor: Mary Beth RayComposition: Tolman CreekManaging Editor: Patrick KanouseIndexer: Tim WrightDevelopment Editor: Allison Beaumont JohnsonProject Editor: Seth KerneyCopy Editor: Karen A. GillTechnical Editors: Mohammad Miri, Ivan Pepelnjak, Hari Rakotoranto
ivAbout the AuthorLuc De Ghein, CCIE No. 1897, is an escalation engineer for Cisco Systems in EMEA. Luc has beenin the networking industry for 13 years and has been with Cisco for more than 11 years. He providesescalation support to Cisco engineers worldwide and teaches others about IP routing protocols andMPLS technologies. Luc has been a speaker at several Networkers conferences. During the past 7years, 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 formore than eight years. Since 1996, Luc has been a Cisco Certified Internetwork Expert (CCIE). Heis certified as both a Routing and Switching CCIE and as a Service Provider CCIE.
vAbout the Technical ReviewersMohammad Miri is currently employed by Alcatel NA. He has more than 14 years of experiencein design and implementation of IP networks for Telecom and Mobile providers involvingbroadband, narrowband, and MPLS and traffic engineering applications over IP. He received hiscomputer science degree in 1989.Ivan Pepelnjak, CCIE No. 1354, is a 25-year veteran of the networking industry. He has more than10 years of experience in designing, installing, troubleshooting, and operating large service providerand enterprise WAN and LAN networks and is currently chief technology advisor at NIL DataCommunications focusing on advanced IP-based networks and web technologies. His bookspublished by Cisco Press include EIGRP Network Design Solutions and MPLS and VPNArchitectures (volumes I and II).Hari Rakotoranto is currently product manager for GMPLS in ITD at Cisco Systems, Inc. He alsoworks closely with service providers and interoperability bodies (ISOCORE and EANTC) in thefield of MPLS on technology deployment and overseeing of future directions. Hari has worked as asoftware engineer and pre- and post-sales technical consultant on different technologies, includingLayer 2/3 switches, routing protocols, network management, and UNIX kernel design. He is anactive member of ITU-T SG13, focusing mainly on MPLS, MPLS OAM, and MPLS Management.
viDedicationThis book is dedicated to my wife Ania, and to my sons Robbe and Lander.
viiAcknowledgmentsI wish to acknowledge a few people who made this book possible. First, I wish to acknowledge myemployer Cisco Systems for providing a great working and learning place. Second, I wish to expressmy 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 itstechnical 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—fortheir support in getting this book published and for their patience with me. Last, but not least, I'dlike to thank my family for their support and understanding.
viiiContents at a GlanceIntroductionxxiPart IFundamentals of MPLS 2Chapter 1The Evolution of MPLS 4Chapter 2MPLS Architecture 24Chapter 3Forwarding Labeled Packets 42Chapter 4Label Distribution Protocol 66Chapter 5MPLS and ATM Architecture 104Chapter 6Cisco Express Forwarding 146Part IIAdvanced MPLS Topics 170Chapter 7MPLS VPN 172Chapter 8MPLS Traffic Engineering 248Chapter 9IPv6 over MPLS 328Chapter 10Any Transport over MPLS 382Chapter 11Virtual Private LAN Service 434Chapter 12MPLS and Quality of Service 456Chapter 13Troubleshooting MPLS Networks 492Chapter 14MPLS Operation and Maintenance 522Chapter 15The Future of MPLS 578Part IIIAppendixes 586Appendix A Answers to Chapter Review Questions 588Index608
ixContentsIntroductionPart IxxiFundamentals of MPLS 2Chapter 1The Evolution of MPLS4Definition of MPLS 5Pre-MPLS Protocols 5Benefits of MPLS 6Bogus Benefit 6The Use of One Unified Network Infrastructure 7Better IP over ATM Integration 7BGP-Free Core 8Peer-to-Peer VPN Model Versus Overlay VPN Model 10Overlay VPN Model 10Peer-to-Peer VPN Model 12Optimal Traffic Flow 16Traffic Engineering 17History of MPLS in Cisco IOS 19Tag Switching to MPLS 19MPLS Applications 21Summary 21Chapter Review Questions 22Chapter 2MPLS Architecture24Introducing MPLS Labels 25Label Stacking 26Encoding of MPLS 27MPLS and the OSI Reference Model 28Label Switch Router 29Label Switched Path 29Forwarding Equivalence Class 30Label Distribution 32Piggyback the Labels on an Existing IP Routing ProtocolRunning a Separate Protocol for Label Distribution 33Label Distribution with LDP 34Label Forwarding Instance Base 35MPLS Payload 36MPLS Label Spaces 36Different MPLS Modes 38Label Distribution Modes 38Label Retention Modes 38LSP Control Modes 3933
xSummary 40Chapter Review QuestionsChapter 340Forwarding Labeled Packets42Forwarding of Labeled Packets 43Label Operation 43IP Lookup Versus Label Lookup 44Load Balancing Labeled Packets 49Unknown Label 51Reserved Labels 51Implicit NULL Label 51Explicit NULL Label 53Router Alert Label 53OAM Alert Label 54Unreserved Labels 54TTL Behavior of Labeled Packets 55TTL Behavior in the Case of IP-to-Label or Label-to-IPTTL Behavior in the Case of Label-to-Label 56TTL Expiration 57MPLS MTU 59MPLS MTU Command 60Giant and Baby Giant Frames 60Giant Frames on Switches 61MPLS Maximum Receive Unit 62Fragmentation of MPLS Packets 63Path MTU Discovery 63Summary 64Chapter Review Questions 64Chapter 4Label Distribution Protocol66LDP Overview 68LDP Operation 69The Discovery of LSRs That Are Running LDP 69LDP Session Establishment and Maintenance 73Number of LDP Sessions 76Advertising of Label Mappings 77Label Withdrawing 81Housekeeping by Means of Notification 83Targeted LDP Session 84LDP Authentication 86Controlling the Advertisement of Labels via LDP 87MPLS LDP Inbound Label Binding Filtering 90LDP Autoconfiguration 92MPLS LDP-IGP Synchronization 9355
xiHow MPLS LDP-IGP Synchronization Works 95MPLS LDP-IGP Synchronization Configuration 95MPLS LDP Session Protection 100Summary 103Chapter Review Questions 103Chapter 5MPLS and ATM Architecture104Brief Introduction to ATM 106Label Encoding 110Label Advertisement 111Downstream-on-Demand Label AdvertisementLDP Control Mode for ATM 122LDP for LC-ATM 124Label Space 124Loop Detection by LDP 125Loop Detection by Hop Count TLV 125TTL Manipulation 127Loop Detection by Path Vector TLV 129LDP Address Messages 130Blocking Label Requests 130Aggregate Labels 131VC-Merge 132Non MPLS-Aware ATM Switches 135Label Switch Controller 138Multi-Virtual Circuit Tagged Bit Rate 139MPLS CoS 142Frame Mode ATM 143Reducing the Number of LVCs 144Summary 145Chapter Review Questions 145Chapter 6Cisco Express Forwarding146Overview of Cisco IOS Switching Methods 147Process Switching 148Fast Switching 148CEF Switching 149Why Is CEF Needed in MPLS Networks? 149What Are the Components of CEF? 150The Adjacency Table 151The CEF Table 152Operation of CEF 153Distributed CEF (DCEF) 154CEF Switching Packets in Hardware 155116
xiiLoad Balancing in CEF 156Unequal Cost Load Balancing 159Labeling IP Packets by CEF 161Load Balancing Labeled Packets 163Troubleshooting CEF 164Summary 167Chapter Review Questions 168Part IIAdvanced MPLS Topics 170Chapter 7MPLS VPN172Introduction to MPLS VPN 173Definition of a VPN 173VPN Models 174MPLS VPN Model 174Architectural Overview of MPLS VPN 176Virtual Routing Forwarding 176RD 179RTs 180VPNv4 Route Propagation in the MPLS VPN NetworkPacket Forwarding in an MPLS VPN Network 187BGP 188BGP Multiprotocol Extensions and Capabilities 189BGP Extended Community: RT 192VPNv4 Routes 193BGP Carrying the Label 194RRs 197RR Group 198BGP Route Selection 200BGP Multipath 200Using Multiple RDs 203Packet Forwarding 204PE-CE Routing Protocols 207Connected Routes 207Static Routing 208RIP Version 2 208OSPF 209OSPF VRF Configuration 211OSPF Metric Propagation 213BGP Extended Communities for OSPF 214OSPF Network Design 215Sham Link 216Down Bit and Domain Tag 219EIGRP 220Configuration 222185
xiiiPre-Bestpath POI 223EIGRP PE-CE with Backdoor Links 225IS-IS 226eBGP 230Autonomous System Override 231allowas-in 232Hub-and-Spoke 233SOO 235VRF Access 237Internet Access 237Internet in a VPN 237Internet Access Through the Global Routing Table 238Internet Access Through the Global Routing Table with Static RoutesInternet Access Through a Central VRF Site 240Multi-VRF CE 241OSPF VRF-Lite Command 243CE Management 243Summary 246Chapter Review Questions 246Chapter 8MPLS Traffic Engineering248The Need for MPLS TE 249Overview of the Operation of MPLS TE 252Distribution of TE Information 255Requirements for the IGP 255OSPF Extensions for TE 256IS-IS Extensions for TE 261Flooding by the IGP 264Routing and Cost of a TE LSP 266Link TE Attributes 266Maximum Reservable Bandwidth 267Attribute Flags 267TE Metric 267Shared Risk Link Groups 268Maximum Reservable Sub-Pool BandwidthMPLS TE Tunnel (Trunk) Attributes 268TE Tunnel Path Calculation 269Path Setup Option 269IP Explicit Address Exclusion 272Setup and Holding Priority 273Reoptimization 274Periodic Reoptimization 274Event-Driven Reoptimization 275Manual Reoptimization 275268239
xivDual TE Metrics 275PCALC 279RSVP 279RSVP and Labels 280Record Route Object 282Other Information Carried by RSVP 284Putting It All Together 285Shared Explicit Style 288RSVP Messages 289PathTear 289ResvTear 289PathErr 289ResvErr 290Link Manager 290FRR 291FRR—Link Protection 292FRR—Node Protection 297SRLG Used by Backup Tunnels 302Multiple Backup Tunnels 303Forwarding Traffic onto MPLS TE Tunnels 303Static Routing 304Policy-Based Routing 304Autoroute Announce 305Forwarding Adjacency 306Direct Mapping of AToM Traffic onto TE Tunnels 309Class-Based Tunnel Selection 309Cost Calculation of IGP Routes over TE Tunnels 311Default Cost Calculation 311Adjusting the Cost Calculation 319Load Balancing 320MPLS TE and MPLS VPN 321TE Tunnels Between PE Routers 321TE Tunnel with P Router as Tail End Router 321VRF-to-TE Tunnel Routing 324Summary 325Chapter Review Questions 326Chapter 9IPv6 over MPLS328Introduction to IPv6 329The Driving Forces for IPv6 329Overview of the IPv6 Protocol 330The IPv6 Header 330The IPv6 Addressing 332Other IPv6 Novelties 333
xvOverview of IPv6 Unicast Routing in Cisco IOS 334IPv6 RIP (RIPng) 334OSPF for IPv6 or OSPFv3 337IS-IS for IPv6 342EIGRP for IPv6 345Multiprotocol BGP Extensions for IPv6 348CEFv6 351Carrying IPv6 over an MPLS Backbone 352MPLS VPN Network Using IPv6 over IPv4 Tunnels on the CE RoutersCarrying IPv6 over an MPLS Backbone (6PE) 354Operation of 6PE 355Configuration of 6PE 358Verifying 6PE Operation 361Carrying IPv6 in VPNs Across an MPLS Backbone (6VPE) 364Operation of 6VPE 364Configuration of 6VPE 366Verifying 6VPE Operation 372IPv6 Internet Access Through 6VPE 377Supported Features for 6VPE 378Remarks for Both 6PE and 6VPE 378Route Reflectors 378Turning Off TTL Propagation on the PE Routers 379Load Balancing Labeled IPv6 Packets 379PHP 379BGP Functionality 379Summary 380Chapter Review Questions 380Chapter 10Any Transport over MPLS382Understanding the Need for AToM 384Transporting Layer 2 Frames 384AToM Architecture 386Data Plane of AToM 387Signaling the Pseudowire 388C-Bit 390PW Type 390Group ID 391PW ID 392Interface Parameters 392Signaling the Status of the PseudowireThe Control Word 393Control Word Functions 394Pad Small Packets 394392353
xviCarry Control Bits of the Layer 2 Header of the Transported Protocol 394Preserve the Sequence of the Transported Frames 395Facilitate the Correct Load Balancing of AToM Packets in the MPLS Backbone Network396Facilitate Fragmentation and Reassembly 396MPLS MTU in the MPLS Backbone 397The Basic AToM Configuration 398Transported Layer 2 Protocols 402HDLC 402PPP 403Frame Relay 403DLCI-to-DLCI 403Port-to-Port Mode (Port Trunking) 405ATM 408ATM AAL5 408ATM Cell Relay 411Single Cell Relay Mode 411Packed Cell Relay Mode 414Ethernet 416Ethernet Frame Format 416EoMPLS Forwarding 417VLAN ID Rewrite 418EoMPLS Scenario Examples 418Dot1q Tunneling (QinQ) over AToM 424AToM Tunnel Selection 426AToM and QoS 429Summary 432Chapter Review Questions 432Chapter 11Virtual Private LAN Service434The Need for VPLS 435VPLS Architecture 437VPLS Data Plane 439VPLS Signaling 440The Basic VPLS Configuration 441Verifying the VPLS Operation 443VPLS and Tunneling Layer 2 Protocols 446Tunneling Cisco Discovery Protocol 446Tunneling Spanning Tree Protocol 447Trunk Port Between the CE and PE 449Hierarchical VPLS 450H-VPLS with Dot1q Tunneling (QinQ) in the Access LayerH-VPLS with MPLS in the Access Layer 452450
xviiQuality of Service 452Limiting MAC Addresses 454Routing Peering 454Summary 455Chapter Review Questions 455Chapter 12MPLS and Quality of Service456DiffServ with IP Packets 458DiffServ with MPLS Packets 461Default MPLS QoS Behavior in Cisco IOS 462DiffServ Tunneling Models 466Pipe Model 467Short Pipe Model 467Uniform Model 468Advantages of the DiffServ Tunneling Models 469How to Implement the Three DiffServ Tunneling Models 472Recoloring the Packet 472MQC Commands for MPLS QoS 475Moving MPLS QoS from the PE to the CE Router 480Implementing the DiffServ Tunneling Models in Cisco IOS 482The Table-Map Feature 487The Use of MPLS QoS for Ethernet over MPLS 490Summary 490Chapter Review Questions 491Chapter 13Troubleshooting MPLS Networks492Label Stack Depth 493Verifying Label Switched Path 494Tracerouting in MPLS Networks 495Tracerouting in an IP Network 495Label-Aware ICMP 497TTL Behavior in MPLS Networks 498Tracerouting in MPLS Networks 499Problems with Tracerouting in MPLS Networks 503mpls ip ttl-expiration pop Command 504no mpls ip propagate-ttl 505MPLS MTU 510Ping 511Debug MPLS Packets 511Debugging Load Balancing of Labeled Packets 514Verifying MPLS on the Interface 516Verifying Number of Bytes Label Switched 517
xviiiMPLS-Aware Netflow 518Summary 521Chapter Review Questions 521Chapter 14MPLS Operation and Maintenance522Requirements of MPLS OAM 523Detection and Diagnosis of Control and Data Plane Defects 524Detection of a Defect in a Label Switched Path (LSP) 524OAM Packets Flowing on the Same Path as MPLS Data Traffic 525Path Characterization 525Measurement of SLAs 525OAM Interworking 526MIBs 526Accounting 526Router Alert Option and Router Alert Label 526Router Alert Label 528OAM Alert Label 529MPLS LSP Ping 529LSP Ping Protocol Details 531Target FEC Stack 534Downstream Mapping 536Interface and Label Stack TLV 538Errored TLVs TLV 539Reply TOS Byte 539LSP Ping Operation 539LSP Verification 540MPLS Ping in Cisco IOS 541MPLS LSP Traceroute 545MPLS Traceroute in Cisco IOS 546Router Alert Label 551Load Balancing 552VCCV 555IP Service Level Agreement 558VRF-Aware IP SLA 561Netflow Accounting 563SNMP/MIBs 564Context-Based Access for SNMP over MPLS VPN 571MPLS VPN MIBs 572Syslog 573OAM Message Mapping 575Summary 577Chapter Review Questions 577
xixChapter 15The Future of MPLS578New MPLS Applications 579Work at IETF 580MPLS Control Word 580FCS Retention 581AToM Fragmentation and ReassemblyCircuit Emulation 581GMPLS 582OAM Protocols 582MPLS Labeled Multicast 584The Proliferation of MPLS 584Summary 585581Part III Appendixes 586Appendix AAnswers to Chapter Review QuestionsIndex608588
xxIcons Used in This BookCommunicationServerPCPC rISDN/Frame orkstationTokenRingToken RingPrinterLaptopWebServerIBMMainframeFront atewayRouterNetwork CloudBridgeLine: EthernetHubLine: SerialDSU/CSUDSU/CSUFDDICatalystSwitchLine: Switched SerialCommand Syntax ConventionsThe conventions used to present command syntax in this book are the same conventions used inthe Cisco IOS Command Reference. The Command Reference describes these conventions asfollows: Boldface indicates commands and keywords that are entered literally as shown. In actualconfiguration examples and output (not general command syntax), boldface indicatescommands that are manually input by the user (such as a show command). Italics indicate arguments for which you supply actual values. Vertical bars ( ) separate alternative, mutually exclusive elements. Square brackets [ ] indicate optional elements. Braces { } indicate a required choice. Braces within brackets [{ }] indicate a required choice within an optional element.
xxiIntroductionAs an escalation engineer, I experienced the boom of Multiprotocol Label Switching (MPLS)networking first hand. I saw the first trials of MPLS in service provider networks and saw MPLSsuccessfully expanding further into enterprise networks. In addition, I witnessed new MPLStechnologies coming into existence, which the networkin
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 Edi
VPN Customer Connectivity—MPLS/VPN Design Choices Summary 11. Advanced MPLS/VPN Topologies Intranet and Extranet Integration Central Services Topology MPLS/VPN Hub-and-spoke Topology Summary 12. Advanced MPLS/VPN Topics MPLS/VPN: Scaling the Solution Routing Convergence Within an MPLS-enabled VPN Network Advertisement of Routes Across the .
slide series thatdescribe the Multiprotocol Label Switching (MPLS) concept . Layer-3 VPNs Layer-2 VPNs MPLS QoS MPLS TE MPLS OAM/MIBs End-to-end Services MPLS Network Services . §MPLS label forwarding and signaling mechanisms Network Infrastructure MPLS Signaling and Forwarding Layer-3 VPNs Layer-2 VPNs
MPLS-based VPN services: L3 MPLS VPN and L2 MPLS VPN. MPLS L2VPN has two modes: Virtual Private LAN Service (VPLS) and Virtual Leased Line (VLL). VLL applies to point-to-point networking scenarios, while VPLS supports point-to-multipoint and multipoint-to-multipoint networking. From users' point of view, the whole MPLS network is
MPLS and VPN Architectures, Volume II, begins with a brief refresher of the MPLS VPN Architecture. Part II describes advanced MPLS VPN connectivity including the integration of service provider access technologies (dial, DSL, cable, Ethernet) and a variety of routing protocols (IS-IS, EIGRP, and OSPF), arming the reader with the knowledge of how to
MPLS PW OAM mechanisms are described next, and a brief look at existing layer 2 OAM mechanisms is provided. The article goes on to describe the relationship between end-to-end fault detection and the segment-based OAM mechanisms. MPLS PW An MPLS PW is the mechanism used to carry layer 2 traffic over MPLS. It is a point-to-point
MPLS OAM Overview MPLS OAM technology provides the MPLS network with a defect-detection tool and a defect-rectification mechanism that are independent of any Layer 3 or Layer 2 protocols. The check function of the CR-LSP forwarding plane is implemented through MPLS OAM and protection switching.
Usetheping sr-mpls fec fec-type igp isis CLIcommandtoexecuteanIS-ISSRpingandtheping sr-mpls fec fec-type bgp CLIcommandtoexecuteaBGPping. switch# ping sr-mpls 11.1.1.3/32 fec-type igp isis Sending 5, 100-byte MPLS Echos to IGP Prefix SID(IS-IS) FEC 11.1.1.3/32, timeout
SDN in Access network, SDN in Optical Layer & MPLS on top Working in orchestration Depends on -Control Plane, SDN Controllers, APIs Communication through Open Interfaces Access SDN SDN to MPLS Control Plane API Function Edge Gate way Programmable MAC/VLAN/PBB & MPLS to MPLS Mapping Ethernet CPRI/dRoF
