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# High Availability Network Fundamentals

## Overview

A practical guide to modeling and designing reliable networks

- Provides a detailed introduction to modeling availability necessary for network design
- Helps network designers understand the theoretical availability of their topologies
- Explains the factors that limit availability to minimize the number of network failures
- Provides all the information necessary to do basic availability modeling/budgeting

High Availability Network Fundamentals discusses the need for and the mathematics of availability, then moves on to cover the issues affecting availability, including hardware, software, design strategies, human error, and environmental considerations. After setting up the range of common problems, it then delves into the details of how to design networks for fault tolerance and provides sample calculations for specific systems. Also included is a complete, end-to-end example showing availability calculations for a sample network.

## Product Details

ISBN-13: | 9781587130175 |
---|---|

Publisher: | Cisco Press |

Publication date: | 05/09/2001 |

Series: | Networking Technology Series |

Edition description: | New Edition |

Pages: | 256 |

Product dimensions: | 7.38(w) x 9.20(h) x 0.58(d) |

## About the Author

**Chris Oggerino** is a Serviceability Design Engineer with Cisco Systems. Chris has spent the last 4+ years working on the reliability, availability, serviceability and usability of products atthe world's leading company for internetworking devices. Prior to his current position, Chris was a Support Engineer at 3Com where he focused on the design, implementation, and maintenance of the network for Wells Fargo and Columbia Healthcare Network. Chris has a BA in Mathematics from San Jose State University.

## Read an Excerpt

**Chris Oggerino** is a Serviceability Design Engineer with Cisco Systems. Chris has spent the last 4+ years working on the reliability, availability, serviceability and usability of products atthe world's leading company for internetworking devices. Prior to his current position, Chris was a Support Engineer at 3Com where he focused on the design, implementation, and maintenance of the network for Wells Fargo and Columbia Healthcare Network. Chris has a BA in Mathematics from San Jose State University.

## First Chapter

**Chris Oggerino** is a Serviceability Design Engineer with Cisco Systems. Chris has spent the last 4+ years working on the reliability, availability, serviceability and usability of products atthe world's leading company for internetworking devices. Prior to his current position, Chris was a Support Engineer at 3Com where he focused on the design, implementation, and maintenance of the network for Wells Fargo and Columbia Healthcare Network. Chris has a BA in Mathematics from San Jose State University.

## Table of Contents

Part I Introduction to Availability

Chapter 1

Introduction to High Availability Networking

Why Do We Need High Availability?

What Is High Availability?

Attracting and Keeping Internet Customers

High Availability and Government Regulation

Presenting and Describing High Availability Measurements

The Percentage Method

The Defects per Million Method

MTBF, MTTR, and Availability

Relating the Percentage and DPM Methods

Additional Considerations in Measuring Availability

Analyzing Time Spent in Network Outages

Chapter 2

The Basic Mathematics of High Availability

Determining the Availability of Network Device Components

Estimating MTTR of a Network

The Availability Equation and Network Device Components

Availability and Uptime/Downtime

Determining the Availability of a Single Component

Determining the Availability of Multiple Components

Serial Availability

Simple Parallel Availability

N + 1 Parallel Availability

Serial/Parallel Availability

Determining Data Flow in a Network: Path Analysis

Using Reliability Block Diagrams for Path Analysis

Chapter 3

Network Topology Fundamentals

Serial Topology

Parallel Topology

Serial/Parallel Topology

Summary

Part II Predicting Availability

Chapter 4

Factors That Affect Availability

Predicting Hardware Availability

MTBF and MTTR

Calculating the Availability of a Simple Network Device

Calculating the Availability of a Redundant Single System

Calculating the Availability of a Network Segment

Predicting Software Availability

Calculating Software MTBF

Examples of Including Software Availability

Predicting Availability Considering the Environment

MTBF and MTTR for Electrical Power

Mitigating Power Loss

Power Loss Summary

Including Human Error and Process in Availability Calculations

Historical Downtime Due to Human Error and Process

Creating a Map of Downtimes Caused by Process Issues

Incorporating Process Issues in Network Availability Predictions

Mitigating Human Error Through Operations Process

Human Error and Operation Process Summary

Network Design

Load Sharing Redundant Fail-over Mechanisms

Standby Redundant Fail-over Mechanisms

Examples of Fail-over Mechanism Calculations

Summary

References Used in This Chapter

Chapter 5

Predicting End-to-End Network Availability: The Divide-and-Conquer Method

The Divide-and-Conquer Steps

A VoIP Network Example

Step 1: Determine Scenarios and RBDs

Step 2: Calculate the Availability of the Network Components

Step 3: Scenario-by-Scenario Redundancy Computations

Step 4: End-to-End Availability Calculations for Each Scenario

Section Summary: The End-to-End Network Availability Results

Designing Networks for Availability Goals

Summary

Part III Examples of Analyzing Real-World Availability

Chapter 6

Three Cisco Products:An Availability Analysis

Cisco uBR 924 Availability Calculations

Cisco uBR 7246 Availability Calculations

Cisco 12000 Availability Calculations

Chapter 7

A Small ISP Network: An Availability Analysis

The Small Internet Service Provider Network

Scenario 1 of The Small ISP Example

System Level Calculations for Scenario 1

The Network Availability for Scenario 1

Summary of Scenario 1

Scenario 2 of The Small ISP Example

System Level Calculations for Scenario 2

The Network Availability for Scenario 2

Summary

Chapter 8

An Enterprise Network: An Availability Analysis

System Level Calculations for an Enterprise Network

The Cisco 3600 Availability Calculations

The Cisco 1538 Availability Calculations

The Downtime from Lost Power for an Enterprise Network

Network Calculations for an Enterprise Network

The Parallel Component Calculations

The Serial Availability Calculations

Human Error and Process Contribution to Downtime in an Enterprise Network

Summary

Chapter 9

A Large VoIP Network: An Availability Analysis

A VoIP over Cable Network

The Availability Scenarios of VoIP over HFC

Scenario 1: Data to the Internet

Scenario 2: On Net Local Calling

Scenario 3: Off Net Local Calling

Scenario 4: Off Net Long Distance Calling

A Final Note About Scenarios

The System Level Calculations for VoIP over HFC

The CPE Router System Level Calculations

The Head-end Router System Level Calculations

The Backbone Router System Level Calculations

The Switch (8540) System Level Calculations

The PSTN Gateway System Level Calculations

The Assumed Availability Figures

Network Level Availability Calculations

Calculating Smaller Redundant Segments

Small Serial Network Component Calculations

Major Network Service Construct Availability

The Internet Access Service Availability

The Network Control Service Availability

Power Contribution to Downtime

PSTN Gateway Services Availability Computations

Calculating Scenario Availability

The Scenario 1 Calculations

The Scenario 2 Calculations

The Scenario 3 and 4 Calculations

Summary

Appendix A

The Contents of the CD

Computer Requirements

Basic Instructions for Using the CD

Chapter by Chapter Contents

Using the SHARC Spreadsheet

System Configuration Worksheet Procedure

Index

## Reading Group Guide

Part I Introduction to Availability

Chapter 1

Introduction to High Availability Networking

Why Do We Need High Availability?

What Is High Availability?

Attracting and Keeping Internet Customers

High Availability and Government Regulation

Presenting and Describing High Availability Measurements

The Percentage Method

The Defects per Million Method

MTBF, MTTR, and Availability

Relating the Percentage and DPM Methods

Additional Considerations in Measuring Availability

Analyzing Time Spent in Network Outages

Chapter 2

The Basic Mathematics of High Availability

Determining the Availability of Network Device Components

Estimating MTTR of a Network

The Availability Equation and Network Device Components

Availability and Uptime/Downtime

Determining the Availability of a Single Component

Determining the Availability of Multiple Components

Serial Availability

Simple Parallel Availability

N + 1 Parallel Availability

Serial/Parallel Availability

Determining Data Flow in a Network: Path Analysis

Using Reliability Block Diagrams for Path Analysis

Chapter 3

Network Topology Fundamentals

Serial Topology

Parallel Topology

Serial/Parallel Topology

Summary

Part II Predicting Availability

Chapter 4

Factors That Affect Availability

Predicting Hardware Availability

MTBF and MTTR

Calculating the Availability of a Simple Network Device

Calculating the Availability of a Redundant Single System

Calculating the Availability of a Network Segment

Predicting Software Availability

Calculating Software MTBF

Examples of Including Software Availability

Predicting Availability Considering the Environment

MTBF and MTTR for Electrical Power

Mitigating Power Loss

Power Loss Summary

Including Human Error and Process in Availability Calculations

Historical Downtime Due to Human Error and Process

Creating a Map of Downtimes Caused by Process Issues

Incorporating Process Issues in Network Availability Predictions

Mitigating Human Error Through Operations Process

Human Error and Operation Process Summary

Network Design

Load Sharing Redundant Fail-over Mechanisms

Standby Redundant Fail-over Mechanisms

Examples of Fail-over Mechanism Calculations

Summary

References Used in This Chapter

Chapter 5

Predicting End-to-End Network Availability: The Divide-and-Conquer Method

The Divide-and-Conquer Steps

A VoIP Network Example

Step 1: Determine Scenarios and RBDs

Step 2: Calculate the Availability of the Network Components

Step 3: Scenario-by-Scenario Redundancy Computations

Step 4: End-to-End Availability Calculations for Each Scenario

Section Summary: The End-to-End Network Availability Results

Designing Networks for Availability Goals

Summary

Part III Examples of Analyzing Real-World Availability

Chapter 6

Three Cisco Products:An Availability Analysis

Cisco uBR 924 Availability Calculations

Cisco uBR 7246 Availability Calculations

Cisco 12000 Availability Calculations

Chapter 7

A Small ISP Network: An Availability Analysis

The Small Internet Service Provider Network

Scenario 1 of The Small ISP Example

System Level Calculations for Scenario 1

The Network Availability for Scenario 1

Summary of Scenario 1

Scenario 2 of The Small ISP Example

System Level Calculations for Scenario 2

The Network Availability for Scenario 2

Summary

Chapter 8

An Enterprise Network: An Availability Analysis

System Level Calculations for an Enterprise Network

The Cisco 3600 Availability Calculations

The Cisco 1538 Availability Calculations

The Downtime from Lost Power for an Enterprise Network

Network Calculations for an Enterprise Network

The Parallel Component Calculations

The Serial Availability Calculations

Human Error and Process Contribution to Downtime in an Enterprise Network

Summary

Chapter 9

A Large VoIP Network: An Availability Analysis

A VoIP over Cable Network

The Availability Scenarios of VoIP over HFC

Scenario 1: Data to the Internet

Scenario 2: On Net Local Calling

Scenario 3: Off Net Local Calling

Scenario 4: Off Net Long Distance Calling

A Final Note About Scenarios

The System Level Calculations for VoIP over HFC

The CPE Router System Level Calculations

The Head-end Router System Level Calculations

The Backbone Router System Level Calculations

The Switch (8540) System Level Calculations

The PSTN Gateway System Level Calculations

The Assumed Availability Figures

Network Level Availability Calculations

Calculating Smaller Redundant Segments

Small Serial Network Component Calculations

Major Network Service Construct Availability

The Internet Access Service Availability

The Network Control Service Availability

Power Contribution to Downtime

PSTN Gateway Services Availability Computations

Calculating Scenario Availability

The Scenario 1 Calculations

The Scenario 2 Calculations

The Scenario 3 and 4 Calculations

Summary

Appendix A

The Contents of the CD

Computer Requirements

Basic Instructions for Using the CD

Chapter by Chapter Contents

Using the SHARC Spreadsheet

System Configuration Worksheet Procedure

Index

## Interviews

Part I Introduction to Availability

Chapter 1

Introduction to High Availability Networking

Why Do We Need High Availability?

What Is High Availability?

Attracting and Keeping Internet Customers

High Availability and Government Regulation

Presenting and Describing High Availability Measurements

The Percentage Method

The Defects per Million Method

MTBF, MTTR, and Availability

Relating the Percentage and DPM Methods

Additional Considerations in Measuring Availability

Analyzing Time Spent in Network Outages

Chapter 2

The Basic Mathematics of High Availability

Determining the Availability of Network Device Components

Estimating MTTR of a Network

The Availability Equation and Network Device Components

Availability and Uptime/Downtime

Determining the Availability of a Single Component

Determining the Availability of Multiple Components

Serial Availability

Simple Parallel Availability

N + 1 Parallel Availability

Serial/Parallel Availability

Determining Data Flow in a Network: Path Analysis

Using Reliability Block Diagrams for Path Analysis

Chapter 3

Network Topology Fundamentals

Serial Topology

Parallel Topology

Serial/Parallel Topology

Summary

Part II Predicting Availability

Chapter 4

Factors That Affect Availability

Predicting Hardware Availability

MTBF and MTTR

Calculating the Availability of a Simple Network Device

Calculating the Availability of a Redundant Single System

Calculating the Availability of a Network Segment

Predicting Software Availability

Calculating Software MTBF

Examples of Including Software Availability

Predicting Availability Considering the Environment

MTBF and MTTR for Electrical Power

Mitigating Power Loss

Power Loss Summary

Including Human Error and Process in Availability Calculations

Historical Downtime Due to Human Error and Process

Creating a Map of Downtimes Caused by Process Issues

Incorporating Process Issues in Network Availability Predictions

Mitigating Human Error Through Operations Process

Human Error and Operation Process Summary

Network Design

Load Sharing Redundant Fail-over Mechanisms

Standby Redundant Fail-over Mechanisms

Examples of Fail-over Mechanism Calculations

Summary

References Used in This Chapter

Chapter 5

Predicting End-to-End Network Availability: The Divide-and-Conquer Method

The Divide-and-Conquer Steps

A VoIP Network Example

Step 1: Determine Scenarios and RBDs

Step 2: Calculate the Availability of the Network Components

Step 3: Scenario-by-Scenario Redundancy Computations

Step 4: End-to-End Availability Calculations for Each Scenario

Section Summary: The End-to-End Network Availability Results

Designing Networks for Availability Goals

Summary

Part III Examples of Analyzing Real-World Availability

Chapter 6

Three Cisco Products:An Availability Analysis

Cisco uBR 924 Availability Calculations

Cisco uBR 7246 Availability Calculations

Cisco 12000 Availability Calculations

Chapter 7

A Small ISP Network: An Availability Analysis

The Small Internet Service Provider Network

Scenario 1 of The Small ISP Example

System Level Calculations for Scenario 1

The Network Availability for Scenario 1

Summary of Scenario 1

Scenario 2 of The Small ISP Example

System Level Calculations for Scenario 2

The Network Availability for Scenario 2

Summary

Chapter 8

An Enterprise Network: An Availability Analysis

System Level Calculations for an Enterprise Network

The Cisco 3600 Availability Calculations

The Cisco 1538 Availability Calculations

The Downtime from Lost Power for an Enterprise Network

Network Calculations for an Enterprise Network

The Parallel Component Calculations

The Serial Availability Calculations

Human Error and Process Contribution to Downtime in an Enterprise Network

Summary

Chapter 9

A Large VoIP Network: An Availability Analysis

A VoIP over Cable Network

The Availability Scenarios of VoIP over HFC

Scenario 1: Data to the Internet

Scenario 2: On Net Local Calling

Scenario 3: Off Net Local Calling

Scenario 4: Off Net Long Distance Calling

A Final Note About Scenarios

The System Level Calculations for VoIP over HFC

The CPE Router System Level Calculations

The Head-end Router System Level Calculations

The Backbone Router System Level Calculations

The Switch (8540) System Level Calculations

The PSTN Gateway System Level Calculations

The Assumed Availability Figures

Network Level Availability Calculations

Calculating Smaller Redundant Segments

Small Serial Network Component Calculations

Major Network Service Construct Availability

The Internet Access Service Availability

The Network Control Service Availability

Power Contribution to Downtime

PSTN Gateway Services Availability Computations

Calculating Scenario Availability

The Scenario 1 Calculations

The Scenario 2 Calculations

The Scenario 3 and 4 Calculations

Summary

Appendix A

The Contents of the CD

Computer Requirements

Basic Instructions for Using the CD

Chapter by Chapter Contents

Using the SHARC Spreadsheet

System Configuration Worksheet Procedure

Index

## Recipe

Part I Introduction to Availability

Chapter 1

Introduction to High Availability Networking

Why Do We Need High Availability?

What Is High Availability?

Attracting and Keeping Internet Customers

High Availability and Government Regulation

Presenting and Describing High Availability Measurements

The Percentage Method

The Defects per Million Method

MTBF, MTTR, and Availability

Relating the Percentage and DPM Methods

Additional Considerations in Measuring Availability

Analyzing Time Spent in Network Outages

Chapter 2

The Basic Mathematics of High Availability

Determining the Availability of Network Device Components

Estimating MTTR of a Network

The Availability Equation and Network Device Components

Availability and Uptime/Downtime

Determining the Availability of a Single Component

Determining the Availability of Multiple Components

Serial Availability

Simple Parallel Availability

N + 1 Parallel Availability

Serial/Parallel Availability

Determining Data Flow in a Network: Path Analysis

Using Reliability Block Diagrams for Path Analysis

Chapter 3

Network Topology Fundamentals

Serial Topology

Parallel Topology

Serial/Parallel Topology

Summary

Part II Predicting Availability

Chapter 4

Factors That Affect Availability

Predicting Hardware Availability

MTBF and MTTR

Calculating the Availability of a Simple Network Device

Calculating the Availability of a Redundant Single System

Calculating the Availability of a Network Segment

Predicting Software Availability

Calculating Software MTBF

Examples of Including Software Availability

Predicting Availability Considering the Environment

MTBF and MTTR for Electrical Power

Mitigating Power Loss

Power Loss Summary

Including Human Error and Process in Availability Calculations

Historical Downtime Due to Human Error and Process

Creating a Map of Downtimes Caused by Process Issues

Incorporating Process Issues in Network Availability Predictions

Mitigating Human Error Through Operations Process

Human Error and Operation Process Summary

Network Design

Load Sharing Redundant Fail-over Mechanisms

Standby Redundant Fail-over Mechanisms

Examples of Fail-over Mechanism Calculations

Summary

References Used in This Chapter

Chapter 5

Predicting End-to-End Network Availability: The Divide-and-Conquer Method

The Divide-and-Conquer Steps

A VoIP Network Example

Step 1: Determine Scenarios and RBDs

Step 2: Calculate the Availability of the Network Components

Step 3: Scenario-by-Scenario Redundancy Computations

Step 4: End-to-End Availability Calculations for Each Scenario

Section Summary: The End-to-End Network Availability Results

Designing Networks for Availability Goals

Summary

Part III Examples of Analyzing Real-World Availability

Chapter 6

Three Cisco Products:An Availability Analysis

Cisco uBR 924 Availability Calculations

Cisco uBR 7246 Availability Calculations

Cisco 12000 Availability Calculations

Chapter 7

A Small ISP Network: An Availability Analysis

The Small Internet Service Provider Network

Scenario 1 of The Small ISP Example

System Level Calculations for Scenario 1

The Network Availability for Scenario 1

Summary of Scenario 1

Scenario 2 of The Small ISP Example

System Level Calculations for Scenario 2

The Network Availability for Scenario 2

Summary

Chapter 8

An Enterprise Network: An Availability Analysis

System Level Calculations for an Enterprise Network

The Cisco 3600 Availability Calculations

The Cisco 1538 Availability Calculations

The Downtime from Lost Power for an Enterprise Network

Network Calculations for an Enterprise Network

The Parallel Component Calculations

The Serial Availability Calculations

Human Error and Process Contribution to Downtime in an Enterprise Network

Summary

Chapter 9

A Large VoIP Network: An Availability Analysis

A VoIP over Cable Network

The Availability Scenarios of VoIP over HFC

Scenario 1: Data to the Internet

Scenario 2: On Net Local Calling

Scenario 3: Off Net Local Calling

Scenario 4: Off Net Long Distance Calling

A Final Note About Scenarios

The System Level Calculations for VoIP over HFC

The CPE Router System Level Calculations

The Head-end Router System Level Calculations

The Backbone Router System Level Calculations

The Switch (8540) System Level Calculations

The PSTN Gateway System Level Calculations

The Assumed Availability Figures

Network Level Availability Calculations

Calculating Smaller Redundant Segments

Small Serial Network Component Calculations

Major Network Service Construct Availability

The Internet Access Service Availability

The Network Control Service Availability

Power Contribution to Downtime

PSTN Gateway Services Availability Computations

Calculating Scenario Availability

The Scenario 1 Calculations

The Scenario 2 Calculations

The Scenario 3 and 4 Calculations

Summary

Appendix A

The Contents of the CD

Computer Requirements

Basic Instructions for Using the CD

Chapter by Chapter Contents

Using the SHARC Spreadsheet

System Configuration Worksheet Procedure

Index