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Layer 2 VPN Architectures

Layer 2 VPN Architectures

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  • Copyright 2004
  • Pages: 648
  • Edition: 1st
  • eBook (Watermarked)
  • ISBN-10: 0-13-279851-4
  • ISBN-13: 978-0-13-279851-8

A complete guide to understanding, designing, and deploying Layer 2 VPN technologies and pseudowire emulation applications

  • Evaluate market drivers for Layer 2 VPNs
  • Understand the architectural frame-work and choices for Layer 2 VPNs, including AToM and L2TPv3
  • Grasp the essentials of Layer 2 LAN and WAN technologies
  • Examine the theoretical and operational details of MPLS and LDP as they pertain to AToM
  • Understand the theoretical and operational details of Layer 2 protocols over L2TPv3 in IP networks
  • Learn about Layer 2 VPN bridged and routed interworking and Layer 2 local switching
  • Understand the operation and application of Virtual Private LAN Services (VPLS)
  • Learn about foundation and advanced AToM and L2TPv3 topics through an extensive collection of case studies 

The historical disconnect between legacy Layer 2 and Layer 3 VPN solutions has forced service providers to build, operate, and maintain separate infrastructures to accommodate various VPN access technologies. This costly proposition, however, is no longer necessary. As part of its new Unified VPN Suite, Cisco Systems® now offers next-generation Layer 2 VPN services like Layer 2 Tunneling Protocol version 3 (L2TPv3) and Any Transport over MPLS (AToM) that enable service providers to offer Frame Relay, ATM, Ethernet, and leased-line services over a common IP/MPLS core network. By unifying multiple network layers and providing an integrated set of software services and management tools over this infrastructure, the Cisco® Layer 2 VPN solution enables established carriers, IP-oriented ISP/CLECs, and large enterprise customers (LECs) to reach a broader set of potential VPN customers and offer truly global VPNs.

Layer 2 VPN Architectures is a comprehensive guide to consolidating network infrastructures and extending VPN services. The book opens by discussing Layer 2 VPN applications utilizing both AToM and L2TPv3 protocols and comparing Layer 3 versus Layer 2 provider-provisioned VPNs. In addition to describing the concepts related to Layer 2 VPNs, this book provides an extensive collection of case studies that show you how these technologies and architectures work. The case studies include both AToM and L2TPv3 and reveal real-world service provider and enterprise design problems and solutions with hands-on configuration examples and implementation details. The case studies include all Layer 2 technologies transported using AToM and L2TPv3 pseudowires, including Ethernet, Ethernet VLAN, HDLC, PPP, Frame Relay, ATM AAL5 and ATM cells, and advanced topics relevant to Layer 2 VPN deployment, such as QoS and scalability.

Sample Content

Table of Contents


Part I   Foundation

Chapter 1   Understanding Layer 2 VPNs

Understanding Traditional VPNs

Legacy Layer 2 VPNs

Layer 3 VPNs

Challenges of Traditional VPNs

Introducing Enhanced Layer 2 VPNs


Chapter 2   Pseudowire Emulation Framework and Standards

Pseudowire Emulation Overview

Network Reference Model

Protocol Layer and System Architecture

Native Service Processing

Pseudowire Encapsulation Processing

Transporting over the PSN

Setting Up a Pseudowire

Pseudowire Emulation Standardization

IETF Working Groups

Layer 2 VPN Architectures on Pseudowire Emulation



Other Layer 2 VPN Architectures


Chapter 3   Layer 2 VPN Architectures

Legacy Layer 2 VPNs

Frame Relay and ATM

Data Link Switching

Virtual Private Dial-Up Network

Any Transport over MPLS Overview

Using Label Stacking in AToM

Layer 2 Protocols Supported by AToM

Deciding Whether to Use AToM

Existing Network Installation Base

Advanced Network Services


Network Operation Complexity

Layer 2 Tunnel Protocol Version 3 Overview

L2TPv3 Operations

Layer 2 Protocols Supported by L2TPv3

Deciding Whether to Use L2TPv3

Existing Network Installation Base

Advanced Network Services


Network Operation Complexity


Part II   Layer 2 Protocol Primer

Chapter 4   LAN Protocols

Ethernet Background and Encapsulation Overview

Metro Ethernet Overview

Metro Ethernet Service Architectures

Understanding Spanning Tree Protocol

Spanning-Tree Operation Overview

Drawbacks of a Spanning-Tree Implementation in Today’s Networks

Pure Layer 2 Implementation

802.1q Tunneling

802.1q and 802.1p Tagging

Understanding How 802.1q Tunneling Works

802.1q Tunneling Guidelines and Restrictions


Chapter 5   WAN Data-Link Protocols

Introducing HDLC Encapsulation

Introducing PPP Encapsulation

Understanding Frame Relay


Frame Relay Link Management Interface Protocol

Status Enquiry Message Frame

Status Message Frame

Update Status Message Frame

Comparing Gang of Four LMI with Annex A and Annex D

Managing Traffic

Frame Relay Traffic Policing

Frame Relay Traffic Shaping

Understanding ATM


ATM Adaptation Layer

ATM Cell Structure

ATM Management Protocols: ILMI and OAM

Managing Traffic

ATM Traffic Policing

ATM Traffic Shaping


Part III  Any Transport over MPLS

Chapter 6   Understanding Any Transport over MPLS

Introducing the Label Distribution Protocol

LDP Protocol Components

Discovery Mechanisms

LDP Basic Discovery

LDP Extended Discovery

Session Establishment

Label Distribution and Management

Label Binding

LDP Advertisement Message

Label Advertisement Mode

Label Distribution Control Mode

Label Retention Mode

LDP Security

Understanding AToM Operations

Pseudowire Label Binding

Establishing AToM Pseudowires

Control Word Negotiation

Using Sequence Numbers

Pseudowire Encapsulation


Frame Relay





Chapter 7   LAN Protocols over MPLS Case Studies

Understanding Ethernet over MPLS Technology

EoMPLS Label Stack

Packet Format

MTU Size Requirements

Supported VC Types

Label Imposition

Label Disposition

EoMPLS Transport Case Studies

Case Study 7-1: Router to Router–Port Based

Configuring Port Transparency

Verifying and Troubleshooting Port Transparency Operation

Case Study 7-2: Router to Router–VLAN Based

Configuring VLAN-Based EoMPLS on PE Routers

Configuring VLAN-Based EoMPLS on CE Routers

Verifying and Troubleshooting the Configuration

Case Study 7-3: VLAN Rewrite

Case Study 7-4: Switch to Switch–VLAN Based

Configuring VLAN-Based EoMPLS on PEs

Configuring VLAN-Based EoMPLS on the CE Switches

Verifying and Troubleshooting the Configuration

Case Study 7-5: Switch to Switch–Port Based

Configuring Port-Based EoMPLS on the SanFran Switch

Configuring Port-Based EoMPLS on the NewYork Switch

Case Study 7-6: VLAN Rewrite in Cisco 12000 Series Routers

Verifying and Troubleshooting the Configuration

Port VLAN ID Inconsistency Issue

Case Study 7-7: Map to Pseudowire

Common Troubleshooting Techniques

Troubleshooting EoMPLS on Routers

Debugging EoMPLS Operation on PE Routers

Troubleshooting EoMPLS on Switches


Chapter 8   WAN Protocols over MPLS Case Studies

Setting Up WAN over MPLS Pseudowires

Control Plane

Pseudowire Types Used

Data Plane Encapsulation

Usage of the Control Word

MTU Requirements

Introducing WAN Protocols over MPLS



Frame Relay over MPLS


Encapsulations and Packet Format for AAL5 Transport

Encapsulations and Packet Format for Cell Transport

Configuring WAN Protocols over MPLS Case Studies

Case Study 8-1: HDLC over MPLS

Configuring HDLCoMPLS

Verifying HDLCoMPLS

Troubleshooting HDLCoMPLS

Case Study 8-2: PPP over MPLS

Configuring PPPoMPLS

Verifying and Troubleshooting PPPoMPLS

Case Study 8-3: Frame Relay DLCI over MPLS

Configuring Frame Relay DLCI over MPLS

Verifying and Troubleshooting Frame Relay DLCI over MPLS

Case Study 8-4: ATM AAL5 SDU over MPLS

Configuring AAL5oMPLS

Verifying and Troubleshooting AAL5oMPLS

Case Study 8-5: ATM Cell over MPLS

Configuring CRoMPLS

Verifying CRoMPLS

Advanced WAN AToM Case Studies

Case Study 8-6: Decoding LDP Label Mapping and Pseudowire ID FEC Elements

Case Study 8-7: AToM Hardware Capabilities

Case Study 8-8: Packed Cell Relay over MPLS

Configuring Cell Packing

Verifying Cell Packing Configuration and Operation

Case Study 8-9: Understanding Different ATM Transfer Modes


Single Cell Relay Mode

Packed Cell Relay Mode


Chapter 9   Advanced AToM Case Studies

Load Sharing

Case Study 9-1: Unequal-Cost Multipath

Case Study 9-2: Equal-Cost Multipath

Preferred Path

Case Study 9-3: Configuring Preferred Path Using IP Routing

Case Study 9-4: Configuring a Preferred Path Using MPLS Traffic Engineering Tunnels

Case Study 9-5: Protecting AToM Pseudowires with MPLS Traffic Engineering Fast Reroute

Case Study 9-6: Configuring AToM Pseudowire over  GRE Tunnel

Pseudowire Emulation in Multi-AS Networks

Case Study 9-7: Interconnecting Pseudowires with Dedicated Circuits

Case Study 9-8: BGP IPv4 Label Distribution with IGP Redistribution

Case Study 9-9: BGP IPv4 Label Distribution with IBGP Peering

Case Study 9-10: Configuring LDP Authentication for Pseudowire Signaling

Verifying Pseudowire Data Connectivity

Case Study 9-11: Advertising the VCCV Capability

Case Study 9-12: Verifying Data Plane Connectivity

Quality of Service in AToM

Case Study 9-13: Traffic Marking

Case Study 9-14: Traffic Policing

Case Study 9-15: Queuing and Shaping

Case Study 9-16: Intermediate Markings

Case Study 9-17: Layer 2—Specific Matching and Setting

Ethernet over MPLS QoS

Frame Relay over MPLS QoS



Part IV Layer 2 Tunneling Protocol Version 3

Chapter 10   Understanding L2TPv3

Universal Transport Interface: L2TPv3’s Predecessor

Introducing L2TPv3

L2TPv3 Data Encapsulation

Packet-Switched Network Layer

Demultiplexing Sublayer

Encapsulation Sublayer

L2TPv3 Control Connection

Control Message Encapsulation

L2TPv3 Control Channel Signaling


Chapter 11   LAN Protocols over L2TPv3 Case Studies

Introducing the L2TPv3 Configuration Syntax

xconnect Command Syntax

pseudowire-class Command Syntax

l2tp-class Command Syntax

LAN Protocols over L2TPv3 Case Studies

Case Study 11-1: Ethernet Port-to-Port Manual Session

Ethernet Port-to-Port Manual Configuration

Verifying Ethernet Port-to-Port Manual Session

Ethernet Port-to-Port L2TPv3 Data Plane Details

Case Study 11-2: Ethernet Port-to-Port Manual Session with Keepalive

Ethernet Port-to-Port Manual Session with Keepalive Configuration

Ethernet Port-to-Port Manual Session with Keepalive Verification

Ethernet Port-to-Port Manual Session with Keepalive Control Plane Details

Case Study 11-3: Ethernet Port-to-Port Dynamic Session

Ethernet Port-to-Port Dynamic Configuration

Ethernet Port-to-Port Dynamic Session Verification

Ethernet Port-to-Port Dynamic Session Control Plane Details

Case Study 11-4: Ethernet VLAN-to-VLAN Dynamic Session

Ethernet VLAN-to-VLAN Dynamic Configuration

Ethernet VLAN-to-VLAN Dynamic Session Verification

Ethernet VLAN-to-VLAN Dynamic Session Control Plane Details

Ethernet VLAN-to-VLAN Frame Encapsulation


Chapter 12   WAN Protocols over L2TPv3 Case Studies

WAN Protocols over L2TPv3 Technology Overview

Control Plane

Data Plane

Using the Layer 2-Specific Sublayer

MTU Considerations

HDLC and PPP over L2TPv3

Frame Relay over L2TPv3

ATM over L2TPv3

Configuring WAN Protocols over L2TPv3 Case Studies

Case Study 12-1: HDLC over L2TPv3 with Static Session

Configuring HDLCoL2TPv3

Verifying HDLCoL2TPv3

Data Plane Details

Case Study 12-2: PPP over L2TPv3 with Dynamic Session

Configuring PPPoL2TPv3

Verifying PPPoL2TPv3

Control Plane Negotiation

Data Plane Details

Case Study 12-3: Frame Relay DLCI over L2TPv3 with Dynamic Session

Configuring FRoL2TPv3

Verifying FRoL2TPv3

Data Plane Details

Case Study 12-4: AAL5 SDU over L2TPv3 with Dynamic Session

Configuring AAL5_SDUoL2TPv3 with Dynamic Session

Verifying AAL5_SDUoL2TPv3

Control Plane Details

Data Plane Details

Case Study 12-5: ATM Cell Relay over L2TPv3 with Dynamic Session

Configuring ATM_CRoL2TPv3 with Dynamic Session

Verifying ATM_CRoL2TPv3

Cell Relay Details


Chapter 13   Advanced L2TPv3 Case Studies

Case Study 13-1: L2TPv3 Path MTU Discovery

The Problem: MTU and Fragmentation with L2TPv3

The Solution: Path MTU Discovery

Understanding PMTUD

Implementing PMTUD

Combining PMTUD with DF Bit

Advanced ATM Transport over L2TPv3

Case Study 13-2: ATM OAM Emulation

Case Study 13-3: ATM Cell Packing

Quality of Service

Case Study 13-4: Traffic Marking

ToS Setting

ToS Reflection

MQC IP Precedence or DSCP Setting

Case Study 13-5: Traffic Policing

Case Study 13-6: Queuing and Shaping

Case Study 13-7: Layer 2-Specific Matching and Setting


Part V   Additional Layer 2 VPN Architectures

Chapter 14   Layer 2 Interworking and Local Switching

Layer 2 Interworking Technology Overview

Bridged Interworking

Routed Interworking

Interworking MTU Considerations

Layer 2 Interworking Case Studies

Ethernet (Bridged) Interworking Case Studies

Case Study 14-1: Ethernet-to-VLAN Using AToM

Case Study 14-2: Ethernet-to-VLAN Using L2TPv3

Case Study 14-3: ATM AAL5-to-VLAN Using AToM

Ethernet-VLAN IW Switch Environment Considerations

Routed Interworking

Case Study 14-4: Frame Relay-to-VLAN Using AToM

Case Study 14-5: Frame Relay-to-PPP Using L2TPv3

Case Study 14-6: IP L2-Transport MTU Considerations

Case Study 14-7: Frame Relay-to-ATM Interworking Best Practices

Layer 2 Local Switching

Case Study 14-8: Frame Relay-to-Frame Relay Local Switching

Case Study 14-9: ATM-to-ATM Local Switching

Case Study 14-10: Ethernet-to-Ethernet Local Switching

Layer 2 Local Switching with Interworking

Case Study 14-11: Ethernet-to-VLAN Local Switching

Case Study 14-12: ATM Attachment Circuits and Local Switching

Understanding Advanced Interworking and Local Switching

connect Command


Encapsulation 1: Ethernet-to-VLAN Local Switching Ethernet IW

Encapsulation 2: Frame Relay-to-VLAN IP IW Using AToM

Encapsulation 3: VLAN-to-Ethernet Bridged IW Using L2TPv3

Encapsulation 4: Frame Relay-to-PPP IP-IW Using L2TPv3


Chapter 15   Virtual Private LAN Service

Understanding VPLS Fundamentals

Service Definitions

Virtual Switch

VPLS Forwarding and Flooding

VPLS Signaling

VPLS Deployment Models

Basic Topologic Models

Full Mesh

Hub and Spoke

Partial Mesh

Hierarchical VPLS

Hierarchical VPLS with MPLS Access Network

Hierarchical VPLS with QinQ Access Network

VPLS Redundancy

VPLS Configuration Case Studies

Case Study 15-1: Basic Configuration

Configuring Attachment Circuit

Configuring VFI

Associating Attachment Circuits to the VFI

Configuration Example

Case Study 15-2: Per-VLAN MAC Address Limiting

Case Study 15-3: Quality of Service

Case Study 15-4: Layer 2 Protocol Tunneling

Case Study 15-5: Multihoming


Appendix    L2TPv3 AVP Attribute Types



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