MPLS Fundamentals

Introduction



Part I: Fundamentals of MPLS



Chapter 1 The Evolution of MPLS

Definition of MPLS

Pre-MPLS Protocols

Benefits of MPLS

Bogus Benefit

The Use of One Unified Network Infrastructure

Better IP over ATM Integration

BGP-Free Core

Peer-to-Peer VPN Model Versus Overlay VPN Model0

Overlay VPN Model0

Peer-to-Peer VPN Model

Optimal Traffic Flow

Traffic Engineering

History of MPLS in Cisco IOS

Tag Switching to MPLS

MPLS Applications

Summary

Chapter Review Questions



Chapter 2 MPLS Architecture



Introducing MPLS Labels

Label Stacking

Encoding of MPLS

MPLS and the OSI Reference Model

Label Switch Router

Label Switched Path

Forwarding Equivalence Class

Label Distribution

Piggyback the Labels on an Existing IP Routing Protocol

Running a Separate Protocol for Label Distribution

Label Distribution with LDP

Label Forwarding Instance Base

MPLS Payload

MPLS Label Spaces

Different MPLS Modes

Label Distribution Modes

Label Retention Modes

LSP Control Modes

Summary

Chapter Review Questions



Chapter 3 Forwarding Labeled Packets



Forwarding of Labeled Packets

Label Operation

IP Lookup Versus Label Lookup

Load Balancing Labeled Packets

Unknown Label

Reserved Labels

Implicit NULL Label

Explicit NULL Label

Router Alert Label

OAM Alert Label

Unreserved Labels

TTL Behavior of Labeled Packets

TTL Behavior in the Case of IP-to-Label or Label-to-IP

TTL Behavior in the Case of Label-to-Label

TTL Expiration

MPLS MTU

MPLS MTU Command

Giant and Baby Giant Frames

Giant Frames on Switches

MPLS Maximum Receive Unit

Fragmentation of MPLS Packets

Path MTU Discovery

Summary

Chapter Review Questions



Chapter 4 Label Distribution Protocol



LDP Overview

LDP Operation

The Discovery of LSRs That Are Running LDP

LDP Session Establishment and Maintenance

Number of LDP Sessions

Advertising of Label Mappings

Label Withdrawing

Housekeeping by Means of Notification

Targeted LDP Session

LDP Authentication

Controlling the Advertisement of Labels via LDP

MPLS LDP Inbound Label Binding Filtering

LDP Autoconfiguration

MPLS LDP-IGP Synchronization

How MPLS LDP-IGP Synchronization Works

MPLS LDP-IGP Synchronization Configuration

MPLS LDP Session Protection

Summary

Chapter Review Questions



Chapter 5 MPLS and ATM Architecture



Brief Introduction to ATM

Label Encoding

Label Advertisement

Downstream-on-Demand Label Advertisement

LDP Control Mode for ATM

LDP for LC-ATM

Label Space

Loop Detection by LDP

Loop Detection by Hop Count TLV

TTL Manipulation

Loop Detection by Path Vector TLV

LDP Address Messages

Blocking Label Requests

Aggregate Labels

VC-Merge

Non MPLS-Aware ATM Switches

Label Switch Controller

Multi-Virtual Circuit Tagged Bit Rate

MPLS CoS

Frame Mode ATM

Reducing the Number of LVCs

Summary

Chapter Review Questions



Chapter 6 Cisco Express Forwarding



Overview of Cisco IOS Switching Methods

Process Switching

Fast Switching

CEF Switching

Why Is CEF Needed in MPLS Networks?

What Are the Components of CEF?

The Adjacency Table

The CEF Table

Operation of CEF

Distributed CEF (DCEF)

CEF Switching Packets in Hardware

Load Balancing in CEF

Unequal Cost Load Balancing

Labeling IP Packets by CEF

Load Balancing Labeled Packets

Troubleshooting CEF

Summary

Chapter Review Questions



Part II: Advanced MPLS Topics



Chapter 7 MPLS VPN



Introduction to MPLS VPN

Definition of a VPN

VPN Models

MPLS VPN Model

Architectural Overview of MPLS VPN

Virtual Routing Forwarding

RD

RTs

VPNv4 Route Propagation in the MPLS VPN Network

Packet Forwarding in an MPLS VPN Network

BGP

BGP Multiprotocol Extensions and Capabilities

BGP Extended Community: RT

VPNv4 Routes

BGP Carrying the Label

RRs

RR Group

BGP Route Selection

BGP Multipath

Using Multiple RDs

Packet Forwarding

PE-CE Routing Protocols

Connected Routes

Static Routing

RIP Version 2

OSPF

OSPF VRF Configuration

OSPF Metric Propagation

BGP Extended Communities for OSPF

OSPF Network Design

Sham Link

Down Bit and Domain Tag

EIGRP

Configuration

Pre-Bestpath POI

EIGRP PE-CE with Backdoor Links

IS-IS

eBGP

Autonomous System Override

allowas-in

Hub-and-Spoke

SOO

VRF Access

Internet Access

Internet in a VPN

Internet Access Through the Global Routing Table

Internet Access Through the Global Routing Table with Static Routes

Internet Access Through a Central VRF Site

Multi-VRF CE

OSPF VRF-Lite Command

CE Management

Summary

Chapter Review Questions



Chapter 8 MPLS Traffic Engineering



The Need for MPLS TE

Overview of the Operation of MPLS TE

Distribution of TE Information

Requirements for the IGP

OSPF Extensions for TE

IS-IS Extensions for TE

Flooding by the IGP

Routing and Cost of a TE LSP

Link TE Attributes

Maximum Reservable Bandwidth

Attribute Flags

TE Metric

Shared Risk Link Groups

Maximum Reservable Sub-Pool Bandwidth

MPLS TE Tunnel (Trunk) Attributes

TE Tunnel Path Calculation

Path Setup Option

IP Explicit Address Exclusion

Setup and Holding Priority

Reoptimization

Periodic Reoptimization

Event-Driven Reoptimization

Manual Reoptimization

Dual TE Metrics

PCALC

RSVP

RSVP and Labels

Record Route Object

Other Information Carried by RSVP

Putting It All Together

Shared Explicit Style

RSVP Messages

PathTear

ResvTear

PathErr

ResvErr

Link Manager

FRR

FRR-Link Protection

FRR-Node Protection

SRLG Used by Backup Tunnels

Multiple Backup Tunnels

Forwarding Traffic onto MPLS TE Tunnels

Static Routing

Policy-Based Routing

Autoroute Announce

Forwarding Adjacency

Direct Mapping of AToM Traffic onto TE Tunnels

Class-Based Tunnel Selection

Cost Calculation of IGP Routes over TE Tunnels

Default Cost Calculation

Adjusting the Cost Calculation

Load Balancing

MPLS TE and MPLS VPN

TE Tunnels Between PE Routers

TE Tunnel with P Router as Tail End Router

VRF-to-TE Tunnel Routing

Summary

Chapter Review Questions



Chapter 9 IPv6 over MPLS



Introduction to IPv6

The Driving Forces for IPv6

Overview of the IPv6 Protocol

The IPv6 Header

The IPv6 Addressing

Other IPv6 Novelties

Overview of IPv6 Unicast Routing in Cisco IOS

IPv6 RIP (RIPng)

OSPF for IPv6 or OSPFv3

IS-IS for IPv6

EIGRP for IPv6

Multiprotocol BGP Extensions for IPv6

CEFv6

Carrying IPv6 over an MPLS Backbone

MPLS VPN Network Using IPv6 over IPv4 Tunnels on the CE Routers

Carrying IPv6 over an MPLS Backbone (6PE)

Operation of 6PE

Configuration of 6PE

Verifying 6PE Operation

Carrying IPv6 in VPNs Across an MPLS Backbone (6VPE)

Operation of 6VPE

Configuration of 6VPE

Verifying 6VPE Operation

IPv6 Internet Access Through 6VPE

Supported Features for 6VPE

Remarks for Both 6PE and 6VPE

Route Reflectors

Turning Off TTL Propagation on the PE Routers

Load Balancing Labeled IPv6 Packets

PHP

BGP Functionality

Summary

Chapter Review Questions



Chapter 10 Any Transport over MPLS



Understanding the Need for AToM

Transporting Layer 2 Frames

AToM Architecture

Data Plane of AToM

Signaling the Pseudowire

C-Bit

PW Type

Group ID

PW ID

Interface Parameters

Signaling the Status of the Pseudowire

The Control Word

Control Word Functions

Pad Small Packets

Carry Control Bits of the Layer 2 Header of the Transported Protocol

Preserve the Sequence of the Transported Frames

Facilitate the Correct Load Balancing of AToM Packets in the MPLS Backbone Network

Facilitate Fragmentation and Reassembly

MPLS MTU in the MPLS Backbone

The Basic AToM Configuration

Transported Layer 2 Protocols

HDLC

PPP

Frame Relay

DLCI-to-DLCI

Port-to-Port Mode (Port Trunking)

ATM

ATM AAL5

ATM Cell Relay

Single Cell Relay Mode

Packed Cell Relay Mode

Ethernet

Ethernet Frame Format

EoMPLS Forwarding

VLAN ID Rewrite

EoMPLS Scenario Examples

Dot1q Tunneling (QinQ) over AToM

AToM Tunnel Selection

AToM and QoS

Summary

Chapter Review Questions



Chapter 11 Virtual Private LAN Service



The Need for VPLS

VPLS Architecture

VPLS Data Plane

VPLS Signaling

The Basic VPLS Configuration

Verifying the VPLS Operation

VPLS and Tunneling Layer 2 Protocols

Tunneling Cisco Discovery Protocol

Tunneling Spanning Tree Protocol

Trunk Port Between the CE and PE

Hierarchical VPLS

H-VPLS with Dot1q Tunneling (QinQ) in the Access Layer

H-VPLS with MPLS in the Access Layer

Quality of Service

Limiting MAC Addresses

Routing Peering

Summary

Chapter Review Questions



Chapter 12 MPLS and Quality of Service



DiffServ with IP Packets

DiffServ with MPLS Packets

Default MPLS QoS Behavior in Cisco IOS

DiffServ Tunneling Models

Pipe Model

Short Pipe Model

Uniform Model

Advantages of the DiffServ Tunneling Models

How to Implement the Three DiffServ Tunneling Models

Recoloring the Packet

MQC Commands for MPLS QoS

Moving MPLS QoS from the PE to the CE Router

Implementing the DiffServ Tunneling Models in Cisco IOS

The Table-Map Feature

The Use of MPLS QoS for Ethernet over MPLS

Summary

Chapter Review Questions



Chapter 13 Troubleshooting MPLS Networks



Label Stack Depth

Verifying Label Switched Path

Tracerouting in MPLS Networks

Tracerouting in an IP Network

Label-Aware ICMP

TTL Behavior in MPLS Networks

Tracerouting in MPLS Networks

Problems with Tracerouting in MPLS Networks

mpls ip ttl-expiration pop Command

no mpls ip propagate-ttl

MPLS MTU

Ping

Debug MPLS Packets

Debugging Load Balancing of Labeled Packets

Verifying MPLS on the Interface

Verifying Number of Bytes Label Switched

MPLS-Aware Netflow

Summary

Chapter Review Questions



Chapter 14 MPLS Operation and Maintenance



Requirements of MPLS OAM

Detection and Diagnosis of Control and Data Plane Defects

Detection of a Defect in a Label Switched Path (LSP)

OAM Packets Flowing on the Same Path as MPLS Data Traffic

Path Characterization

Measurement of SLAs

OAM Interworking

MIBs

Accounting

Router Alert Option and Router Alert Label

Router Alert Label

OAM Alert Label

MPLS LSP Ping

LSP Ping Protocol Details

Target FEC Stack

Downstream Mapping

Interface and Label Stack TLV

Errored TLVs TLV

Reply TOS Byte

LSP Ping Operation

LSP Verification

MPLS Ping in Cisco IOS

MPLS LSP Traceroute

MPLS Traceroute in Cisco IOS

Router Alert Label

Load Balancing

VCCV

IP Service Level Agreement

VRF-Aware IP SLA

Netflow Accounting

SNMP/MIBs

Context-Based Access for SNMP over MPLS VPN

MPLS VPN MIBs

Syslog

OAM Message Mapping

Summary

Chapter Review Questions



Chapter 15 The Future of MPLS



New MPLS Applications

Work at IETF

MPLS Control Word

FCS Retention

AToM Fragmentation and Reassembly

Circuit Emulation

GMPLS

OAM Protocols

MPLS Labeled Multicast

The Proliferation of MPLS

Summary



Part III: Appendixes



Appendix A Answers to Chapter Review Questions

Appendix B Static MPLS Labels (online)



Index