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MPLS Fundamentals

Book Description

A comprehensive introduction to all facets of MPLS theory and practice

  • Helps networking professionals choose the suitable MPLS application and design for their network

  • Provides MPLS theory and relates to basic IOS configuration examples

  • The Fundamentals Series from Cisco Press launches the basis to readers for understanding the purpose, application, and management of technologies

MPLS has emerged as the new networking layer for service providers throughout the world. For many service providers and enterprises MPLS is a way of delivering new applications on their IP networks, while consolidating data and voice networks. MPLS has grown to be the new default network layer for service providers and is finding its way into enterprise networks as well. This book focuses on the building blocks of MPLS (architecture, forwarding packets, LDP, MPLS and QoS, CEF, etc.). This book also reviews the different MPLS applications (MPLS VPN, MPLS Traffic Engineering, Carrying IPv6 over MPLS, AToM, VPLS, MPLS OAM
etc.).
You will get a comprehensive overview of all the aspects of MPLS, including the building blocks, its applications, troubleshooting and a perspective on the future of MPLS.

Table of Contents

  1. Copyright
    1. Dedication
  2. About the Author
  3. About the Technical Reviewers
  4. Acknowledgments
  5. Icons Used in This Book
    1. Command Syntax Conventions
  6. Introduction
    1. Goals and Methods
    2. Who Should Read This Book?
    3. How This Book Is Organized
    4. About the Cisco Press Website for This Book
  7. 1. Fundamentals of MPLS
    1. 1. The Evolution of MPLS
      1. Definition of MPLS
      2. Pre-MPLS Protocols
      3. Benefits of MPLS
        1. Bogus Benefit
        2. The Use of One Unified Network Infrastructure
        3. Better IP over ATM Integration
        4. BGP-Free Core
        5. Peer-to-Peer VPN Model Versus Overlay VPN Model
          1. Overlay VPN Model
          2. Peer-to-Peer VPN Model
        6. Optimal Traffic Flow
        7. Traffic Engineering
      4. History of MPLS in Cisco IOS
        1. Tag Switching to MPLS
        2. MPLS Applications
      5. Summary
      6. Chapter Review Questions
    2. 2. MPLS Architecture
      1. Introducing MPLS Labels
        1. Label Stacking
        2. Encoding of MPLS
      2. MPLS and the OSI Reference Model
      3. Label Switch Router
      4. Label Switched Path
      5. Forwarding Equivalence Class
      6. Label Distribution
        1. Piggyback the Labels on an Existing IP Routing Protocol
        2. Running a Separate Protocol for Label Distribution
      7. Label Distribution with LDP
      8. Label Forwarding Instance Base
      9. MPLS Payload
      10. MPLS Label Spaces
      11. Different MPLS Modes
        1. Label Distribution Modes
        2. Label Retention Modes
        3. LSP Control Modes
      12. Summary
      13. Chapter Review Questions
    3. 3. Forwarding Labeled Packets
      1. Forwarding of Labeled Packets
        1. Label Operation
        2. IP Lookup Versus Label Lookup
        3. Load Balancing Labeled Packets
        4. Unknown Label
      2. Reserved Labels
        1. Implicit NULL Label
        2. Explicit NULL Label
        3. Router Alert Label
        4. OAM Alert Label
      3. Unreserved Labels
      4. TTL Behavior of Labeled Packets
        1. TTL Behavior in the Case of IP-to-Label or Label-to-IP
        2. TTL Behavior in the Case of Label-to-Label
        3. TTL Expiration
      5. MPLS MTU
        1. MPLS MTU Command
        2. Giant and Baby Giant Frames
        3. Giant Frames on Switches
        4. MPLS Maximum Receive Unit
      6. Fragmentation of MPLS Packets
      7. Path MTU Discovery
      8. Summary
      9. Chapter Review Questions
    4. 4. Label Distribution Protocol
      1. LDP Overview
      2. LDP Operation
        1. The Discovery of LSRs That Are Running LDP
        2. LDP Session Establishment and Maintenance
          1. Number of LDP Sessions
        3. Advertising of Label Mappings
          1. Label Withdrawing
        4. Housekeeping by Means of Notification
      3. Targeted LDP Session
      4. LDP Authentication
      5. Controlling the Advertisement of Labels via LDP
      6. MPLS LDP Inbound Label Binding Filtering
      7. LDP Autoconfiguration
      8. MPLS LDP-IGP Synchronization
        1. How MPLS LDP-IGP Synchronization Works
        2. MPLS LDP-IGP Synchronization Configuration
      9. MPLS LDP Session Protection
      10. Summary
      11. Chapter Review Questions
    5. 5. MPLS and ATM Architecture
      1. Brief Introduction to ATM
      2. Label Encoding
      3. Label Advertisement
        1. Downstream-on-Demand Label Advertisement
        2. LDP Control Mode for ATM
      4. LDP for LC-ATM
        1. Label Space
        2. Loop Detection by LDP
          1. Loop Detection by Hop Count TLV
          2. TTL Manipulation
          3. Loop Detection by Path Vector TLV
        3. LDP Address Messages
        4. Blocking Label Requests
      5. Aggregate Labels
      6. VC-Merge
      7. Non MPLS-Aware ATM Switches
      8. Label Switch Controller
      9. Multi-Virtual Circuit Tagged Bit Rate
        1. MPLS CoS
      10. Frame Mode ATM
      11. Reducing the Number of LVCs
      12. Summary
      13. Chapter Review Questions
    6. 6. Cisco Express Forwarding
      1. Overview of Cisco IOS Switching Methods
        1. Process Switching
        2. Fast Switching
        3. CEF Switching
      2. Why Is CEF Needed in MPLS Networks?
      3. What Are the Components of CEF?
        1. The Adjacency Table
        2. The CEF Table
      4. Operation of CEF
      5. Distributed CEF (DCEF)
      6. CEF Switching Packets in Hardware
      7. Load Balancing in CEF
      8. Unequal Cost Load Balancing
      9. Labeling IP Packets by CEF
      10. Load Balancing Labeled Packets
      11. Troubleshooting CEF
      12. Summary
      13. Chapter Review Questions
  8. 2. Advanced MPLS Topics
    1. 7. MPLS VPN
      1. Introduction to MPLS VPN
        1. Definition of a VPN
        2. VPN Models
        3. MPLS VPN Model
      2. Architectural Overview of MPLS VPN
        1. Virtual Routing Forwarding
        2. RD
        3. RTs
        4. VPNv4 Route Propagation in the MPLS VPN Network
        5. Packet Forwarding in an MPLS VPN Network
      3. BGP
        1. BGP Multiprotocol Extensions and Capabilities
        2. BGP Extended Community: RT
        3. VPNv4 Routes
        4. BGP Carrying the Label
        5. RRs
          1. RR Group
        6. BGP Route Selection
          1. BGP Multipath
          2. Using Multiple RDs
      4. Packet Forwarding
      5. PE-CE Routing Protocols
        1. Connected Routes
        2. Static Routing
        3. RIP Version 2
        4. OSPF
          1. OSPF VRF Configuration
          2. OSPF Metric Propagation
          3. BGP Extended Communities for OSPF
          4. OSPF Network Design
          5. Sham Link
          6. Down Bit and Domain Tag
        5. EIGRP
          1. Configuration
          2. Pre-Bestpath POI
          3. EIGRP PE-CE with Backdoor Links
      6. IS-IS
        1. eBGP
          1. Autonomous System Override
          2. allowas-in
      7. Hub-and-Spoke
      8. SOO
      9. VRF Access
      10. Internet Access
        1. Internet in a VPN
        2. Internet Access Through the Global Routing Table
        3. Internet Access Through the Global Routing Table with Static Routes
        4. Internet Access Through a Central VRF Site
      11. Multi-VRF CE
        1. OSPF VRF-Lite Command
      12. CE Management
      13. Summary
      14. Chapter Review Questions
    2. 8. MPLS Traffic Engineering
      1. The Need for MPLS TE
      2. Overview of the Operation of MPLS TE
      3. Distribution of TE Information
        1. Requirements for the IGP
        2. OSPF Extensions for TE
        3. IS-IS Extensions for TE
        4. Flooding by the IGP
      4. Routing and Cost of a TE LSP
        1. Link TE Attributes
          1. Maximum Reservable Bandwidth
          2. Attribute Flags
          3. TE Metric
          4. Shared Risk Link Groups
          5. Maximum Reservable Sub-Pool Bandwidth
        2. MPLS TE Tunnel (Trunk) Attributes
        3. TE Tunnel Path Calculation
          1. Path Setup Option
          2. IP Explicit Address Exclusion
          3. Setup and Holding Priority
          4. Reoptimization
          5. Periodic Reoptimization
          6. Event-Driven Reoptimization
          7. Manual Reoptimization
      5. Dual TE Metrics
      6. PCALC
      7. RSVP
        1. RSVP and Labels
        2. Record Route Object
        3. Other Information Carried by RSVP
        4. Putting It All Together
        5. Shared Explicit Style
        6. RSVP Messages
          1. PathTear
          2. ResvTear
          3. PathErr
          4. ResvErr
      8. Link Manager
      9. FRR
        1. FRR—Link Protection
        2. FRR—Node Protection
        3. SRLG Used by Backup Tunnels
        4. Multiple Backup Tunnels
      10. Forwarding Traffic onto MPLS TE Tunnels
        1. Static Routing
        2. Policy-Based Routing
        3. Autoroute Announce
        4. Forwarding Adjacency
        5. Direct Mapping of AToM Traffic onto TE Tunnels
        6. Class-Based Tunnel Selection
        7. Cost Calculation of IGP Routes over TE Tunnels
          1. Default Cost Calculation
          2. Adjusting the Cost Calculation
        8. Load Balancing
      11. MPLS TE and MPLS VPN
        1. TE Tunnels Between PE Routers
        2. TE Tunnel with P Router as Tail End Router
        3. VRF-to-TE Tunnel Routing
      12. Summary
      13. Chapter Review Questions
    3. 9. IPv6 over MPLS
      1. Introduction to IPv6
        1. The Driving Forces for IPv6
        2. Overview of the IPv6 Protocol
          1. The IPv6 Header
          2. The IPv6 Addressing
          3. Other IPv6 Novelties
        3. Overview of IPv6 Unicast Routing in Cisco IOS
          1. IPv6 RIP (RIPng)
          2. OSPF for IPv6 or OSPFv3
          3. IS-IS for IPv6
          4. EIGRP for IPv6
          5. Multiprotocol BGP Extensions for IPv6
        4. CEFv6
      2. Carrying IPv6 over an MPLS Backbone
      3. MPLS VPN Network Using IPv6 over IPv4 Tunnels on the CE Routers
      4. Carrying IPv6 over an MPLS Backbone (6PE)
        1. Operation of 6PE
        2. Configuration of 6PE
        3. Verifying 6PE Operation
      5. Carrying IPv6 in VPNs Across an MPLS Backbone (6VPE)
        1. Operation of 6VPE
        2. Configuration of 6VPE
        3. Verifying 6VPE Operation
        4. IPv6 Internet Access Through 6VPE
        5. Supported Features for 6VPE
      6. Remarks for Both 6PE and 6VPE
        1. Route Reflectors
        2. Turning Off TTL Propagation on the PE Routers
        3. Load Balancing Labeled IPv6 Packets
        4. PHP
        5. BGP Functionality
      7. Summary
      8. Chapter Review Questions
    4. 10. Any Transport over MPLS
      1. Understanding the Need for AToM
      2. Transporting Layer 2 Frames
      3. AToM Architecture
        1. Data Plane of AToM
        2. Signaling the Pseudowire
          1. C-Bit
          2. PW Type
          3. Group ID
          4. PW ID
          5. Interface Parameters
        3. Signaling the Status of the Pseudowire
      4. The Control Word
        1. Control Word Functions
          1. Pad Small Packets
          2. Carry Control Bits of the Layer 2 Header of the Transported Protocol
          3. Preserve the Sequence of the Transported Frames
          4. Facilitate the Correct Load Balancing of AToM Packets in the MPLS Backbone Network
          5. Facilitate Fragmentation and Reassembly
      5. MPLS MTU in the MPLS Backbone
      6. The Basic AToM Configuration
      7. Transported Layer 2 Protocols
        1. HDLC
        2. PPP
        3. Frame Relay
          1. DLCI-to-DLCI
          2. Port-to-Port Mode (Port Trunking)
        4. ATM
        5. ATM AAL5
        6. ATM Cell Relay
          1. Single Cell Relay Mode
          2. Packed Cell Relay Mode
        7. Ethernet
          1. Ethernet Frame Format
          2. EoMPLS Forwarding
          3. VLAN ID Rewrite
          4. EoMPLS Scenario Examples
          5. EoMPLS Carrying Simple Ethernet
          6. EoMPLS Carrying an Ethernet Trunk
          7. EoMPLS Carrying One VLAN
        8. Dot1q Tunneling (QinQ) over AToM
      8. AToM Tunnel Selection
      9. AToM and QoS
      10. Summary
      11. Chapter Review Questions
    5. 11. Virtual Private LAN Service
      1. The Need for VPLS
      2. VPLS Architecture
      3. VPLS Data Plane
      4. VPLS Signaling
      5. The Basic VPLS Configuration
      6. Verifying the VPLS Operation
      7. VPLS and Tunneling Layer 2 Protocols
        1. Tunneling Cisco Discovery Protocol
        2. Tunneling Spanning Tree Protocol
      8. Trunk Port Between the CE and PE
      9. Hierarchical VPLS
        1. H-VPLS with Dot1q Tunneling (QinQ) in the Access Layer
        2. H-VPLS with MPLS in the Access Layer
      10. Quality of Service
      11. Limiting MAC Addresses
      12. Routing Peering
      13. Summary
      14. Chapter Review Questions
    6. 12. MPLS and Quality of Service
      1. DiffServ with IP Packets
      2. DiffServ with MPLS Packets
      3. Default MPLS QoS Behavior in Cisco IOS
      4. DiffServ Tunneling Models
        1. Pipe Model
        2. Short Pipe Model
        3. Uniform Model
        4. Advantages of the DiffServ Tunneling Models
        5. How to Implement the Three DiffServ Tunneling Models
      5. Recoloring the Packet
      6. MQC Commands for MPLS QoS
      7. Moving MPLS QoS from the PE to the CE Router
      8. Implementing the DiffServ Tunneling Models in Cisco IOS
      9. The Table-Map Feature
      10. The Use of MPLS QoS for Ethernet over MPLS
      11. Summary
      12. Chapter Review Questions
    7. 13. Troubleshooting MPLS Networks
      1. Label Stack Depth
      2. Verifying Label Switched Path
      3. Tracerouting in MPLS Networks
        1. Tracerouting in an IP Network
        2. Label-Aware ICMP
        3. TTL Behavior in MPLS Networks
        4. Tracerouting in MPLS Networks
        5. Problems with Tracerouting in MPLS Networks
        6. mpls ip ttl-expiration pop Command
        7. no mpls ip propagate-ttl
      4. MPLS MTU
      5. Ping
      6. Debug MPLS Packets
      7. Debugging Load Balancing of Labeled Packets
      8. Verifying MPLS on the Interface
      9. Verifying Number of Bytes Label Switched
      10. MPLS-Aware Netflow
      11. Summary
      12. Chapter Review Questions
    8. 14. MPLS Operation and Maintenance
      1. Requirements of MPLS OAM
        1. Detection and Diagnosis of Control and Data Plane Defects
        2. Detection of a Defect in a Label Switched Path (LSP)
        3. OAM Packets Flowing on the Same Path as MPLS Data Traffic
        4. Path Characterization
        5. Measurement of SLAs
        6. OAM Interworking
        7. MIBs
        8. Accounting
      2. Router Alert Option and Router Alert Label
        1. Router Alert Label
      3. OAM Alert Label
      4. MPLS LSP Ping
        1. LSP Ping Protocol Details
          1. Target FEC Stack
          2. Downstream Mapping
          3. Interface and Label Stack TLV
          4. Errored TLVs TLV
          5. Reply TOS Byte
        2. LSP Ping Operation
        3. LSP Verification
        4. MPLS Ping in Cisco IOS
      5. MPLS LSP Traceroute
        1. MPLS Traceroute in Cisco IOS
        2. Router Alert Label
      6. Load Balancing
      7. VCCV
      8. IP Service Level Agreement
        1. VRF-Aware IP SLA
      9. Netflow Accounting
      10. SNMP/MIBs
        1. Context-Based Access for SNMP over MPLS VPN
        2. MPLS VPN MIBs
      11. Syslog
        1. OAM Message Mapping
      12. Summary
      13. Chapter Review Questions
    9. 15. The Future of MPLS
      1. New MPLS Applications
      2. Work at IETF
        1. MPLS Control Word
        2. FCS Retention
        3. AToM Fragmentation and Reassembly
        4. Circuit Emulation
        5. GMPLS
        6. OAM Protocols
        7. MPLS Labeled Multicast
      3. The Proliferation of MPLS
      4. Summary
  9. 3. Appendixes
    1. A. Answers to Chapter Review Questions
      1. Chapter 1
      2. Chapter 2
      3. Chapter 3
      4. Chapter 4
      5. Chapter 5
      6. Chapter 6
      7. Chapter 7
      8. Chapter 8
      9. Chapter 9
      10. Chapter 10
      11. Chapter 11
      12. Chapter 12
      13. Chapter 13
      14. Chapter 14