Cisco press top down network design 2nd ed

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Top-Down Network Design Second Edition
By Priscilla Oppenheimer

Publisher: Cisco Press
Pub Date: May 27, 2004
ISBN: 1-58705-152-4
Table of
•
Contents
• Index

Pages: 600

A systems analysis approach to enterprise network design
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•

•
•
•

Master techniques for checking the health of an existing network
to develop a baseline for measuring performance of a new
network design
Explore solutions for meeting QoS requirements, including ATM
traffic management, IETF controlled-load and guaranteed
services, IP multicast, and advanced switching, queuing, and
routing algorithms
Develop network designs that provide the high bandwidth and

low delay required for real-time applications such as multimedia,
distance learning, and videoconferencing
Identify the advantages and disadvantages of various switching
and routing protocols, including transparent bridging, InterSwitch Link (ISL), IEEE 802.1Q, IGRP, EIGRP, OSPF, and BGP4
Effectively incorporate new technologies into enterprise network
designs, including VPNs, wireless networking, and IP Telephony

Top-Down Network Design, Second Edition, is a practical and
comprehensive guide to designing enterprise networks that are reliable,
secure, and manageable. Using illustrations and real-world examples, it
teaches a systematic method for network design that can be applied to
campus LANs, remote-access networks, WAN links, and large-scale
internetworks.
You will learn to analyze business and technical requirements, examine
traffic flow and QoS requirements, and select protocols and technologies
based on performance goals. You will also develop an understanding of
network performance factors such as network utilization, throughput,
accuracy, efficiency, delay, and jitter. Several charts and job aids will
help you apply a top-down approach to network design.
This Second Edition has been revised to include new and updated
material on wireless networks, virtual private networks (VPNs), network
security, network redundancy, modularity in network designs, dynamic
addressing for IPv4 and IPv6, new network design and management


tools, Ethernet scalability options (including 10-Gbps Ethernet, Metro
Ethernet, and Long-Reach Ethernet), and networks that carry voice and
data traffic.
Top-Down Network Design, Second Edition, has a companion website at
, which includes updates to the book,

links to white papers, and supplemental information about design
resources.
This book is part of the Networking Technology Series from Cisco Press,
which offers networking professionals valuable information for
constructing efficient networks, understanding new technologies, and
building successful careers.
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Copyright
About the Author
About the Technical Reviewers
Acknowledgments
Icons Used in This Book
Command Syntax Conventions
Introduction
Changes for the Second Edition
Objectives
Audience
Organization
Part I: Identifying Your Customer's Needs and Goals
Part II: Logical Network Design
Part III: Physical Network Design
Part IV: Testing, Optimizing, and Documenting Your Network Design
Companion Website
Part I. Identifying Your Customer's Needs and Goals
Chapter 1. Analyzing Business Goals and Constraints
Using a Top-Down Network Design Methodology

Analyzing Business Goals
Analyzing Business Constraints
Business Goals Checklist
Summary
Chapter 2. Analyzing Technical Goals and Tradeoffs
Scalability
Availability
Network Performance
Security
Manageability
Usability
Adaptability
Affordability
Making Network Design Tradeoffs
Technical Goals Checklist
Summary
Chapter 3. Characterizing the Existing Internetwork
Characterizing the Network Infrastructure
Checking the Health of the Existing Internetwork
Tools for Characterizing the Existing Internetwork
Network Health Checklist
Summary
Chapter 4. Characterizing Network Traffic


Characterizing Traffic Flow
Characterizing Traffic Load
Characterizing Traffic Behavior
Characterizing Quality of Service Requirements
Network Traffic Checklist

Summary
Summary for Part I
Part II. Logical Network Design
Chapter 5. Designing a Network Topology
Hierarchical Network Design
Redundant Network Design Topologies
Modular Network Design
Designing a Campus Network Design Topology
Designing the Enterprise Edge Topology
Secure Network Design Topologies
Summary
Chapter 6. Designing Models for Addressing and Naming
Guidelines for Assigning Network Layer Addresses
Using a Hierarchical Model for Assigning Addresses
Designing a Model for Naming
Summary
Chapter 7. Selecting Switching and Routing Protocols
Making Decisions as Part of the Top-Down Network Design Process
Selecting Bridging and Switching Protocols
Selecting Routing Protocols
A Summary of IP, AppleTalk, and IPX Routing Protocols
Summary
Chapter 8. Developing Network Security Strategies
Network Security Design
Security Mechanisms
Modularizing Security Design
Summary
Chapter 9. Developing Network Management Strategies
Network Management Design
Network Management Processes

Network Management Architectures
Selecting Protocols for Network Management
Selecting Tools for Network Management
Summary
Summary for Part II
Part III. Physical Network Design
Chapter 10. Selecting Technologies and Devices for Campus Networks
LAN Cabling Plant Design
LAN Technologies
Selecting Internetworking Devices for a Campus Network Design
An Example of a Campus Network Design
Summary
Chapter 11. Selecting Technologies and Devices for Enterprise Networks


Remote-Access Technologies
Selecting Remote-Access Devices for an Enterprise Network Design
WAN Technologies
An Example of a WAN Design
Summary
Summary for Part III
Part IV. Testing, Optimizing, and Documenting Your Network Design
Chapter 12. Testing Your Network Design
Using Industry Tests
Building and Testing a Prototype Network System
Tools for Testing a Network Design
An Example of a Network Design Testing Scenario
Summary
Chapter 13. Optimizing Your Network Design
Optimizing Bandwidth Usage with IP Multicast Technologies

Reducing Serialization Delay
Optimizing Network Performance to Meet Quality of Service Requirements
Cisco Internetwork Operating System Features for Optimizing Network Performance
Summary
Chapter 14. Documenting Your Network Design
Responding to a Customer's Request for Proposal
Contents of a Network Design Document
Summary
Appendix A. Characterizing Network Traffic When Workstations Boot
Novell NetWare Packets
AppleTalk Packets
TCP/IP Packets
TCP/IP DHCP Packets
NetBIOS (NetBEUI) Packets
NetBIOS with WINS Packets
SNA Packets
Appendix B. References and Recommended Reading
Glossary
A
B
C
D
E
F
G-H
I
J-K-L
M
N
O-P

Q-R
S
T


U
V
W
X-Z
Index
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Copyright
Copyright © 2004 Cisco Systems, Inc.
Published by:
Cisco Press
800 East 96th Street
Indianapolis, IN 46240 USA
All rights reserved. No part of this book may be reproduced or transmitted in any
form or by any means, electronic or mechanical, including photocopying, recording,
or by any information storage and retrieval system, without written permission from
the 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 0
First Printing June 2004
Library of Congress Cataloging-in-Publication Number: 2003107988

Trademark Acknowledgments

All terms mentioned in this book that are known to be trademarks or service marks
have been appropriately capitalized. Cisco Press or Cisco Systems, Inc. cannot attest
to the accuracy of this information. Use of a term in this book should not be regarded
as affecting the validity of any trademark or service mark.

Warning and Disclaimer
This book is designed to provide information about top-down network design. Every
effort has been made to make this book as complete and as accurate as possible, but
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The opinions expressed in this book belong to the author and are not necessarily
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Credits
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Editor-in-Chief

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Cisco Representative

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Manager, Marketing Communications Production Manager Patrick Kanouse
Development Editor

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Keith Cline

Technical Editors

Matthew H. Birkner
Blair Buchanan
Dr. Peter J. Welcher

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Composition

Octal Publishing, Inc.

Indexer

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Dedications
To my parents, Dr. Stephen T. Worland, Ph.D., and Mrs. Roberta Worland, M.S. They
gave me an appreciation for knowledge, logic, and analysis, and taught me that
"where there's a will, there's a way."
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About the Author
Priscilla Oppenheimer has been developing data communications and networking
systems since 1980 when she earned her master's degree in information science
from the University of Michigan. After many years as a software developer, she
became a technical instructor and training developer and taught more than 2000
network engineers from most of the Fortune 500 companies. Her employment at
such companies as Apple Computer, Network General, and Cisco Systems gave her a
chance to troubleshoot real-world network design problems and the opportunity to
develop a practical methodology for enterprise network design. Priscilla was one of
the developers of the Cisco Internetwork Design course and the creator of the
Designing Cisco Networks course, and is a CCNP and CCDP. Priscilla currently
teaches computer networking at Southern Oregon University.
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About the Technical Reviewers
Matthew H. Birkner, CCIE No. 3719, is a Technical Advisor at Cisco Systems,
where he specializes in IP, MPLS, and QoS network design. He has influenced many
large carrier and enterprise network designs worldwide. Matt has spoken on MPLS at
the United States and EMEA Cisco Networkers over the past few years. Matt, a
double CCIE, wrote the Cisco Press book Cisco Internetwork Design. Matt holds a
bachelor's of science in electrical engineering from Tufts University.
Blair Buchanan, CCIE No. 1427, is a senior technical architect and convergence
strategist with Sherwood Cameron Associates Limited, in Ottawa, Canada. He has 28
years experience in the communications business where he began his career as a
software developer for real-time data communications in process-control
applications. Blair has participated in ISO standards development and taken lead
roles in internetwork design for large enterprise and service provider businesses in
Canada and the United States. He is currently involved in planning and designing
internetworks for converged services. Blair holds a bachelor's degree in computer
science and mathematics from the University of Western Ontario (1975). He began
teaching Cisco courses in 1992 and maintains his Cisco Routing and Switching CCIE
certification.
Dr. Peter J. Welcher, CCIE No. 1773, CCIP, CCSI, has a Ph.D. in math from MIT.
He started out teaching math at the U.S. Naval Academy while simultaneously
buying and maintaining UNIX systems, writing a book, and writing a major computer
program in C. He saw the light in 1993, and then taught a wide variety of the Cisco
courses for Mentor Technologies, formerly Chesapeake Computer Consultants, while
also doing network consulting whenever possible. Pete is now doing high-level
network consulting with Chesapeake Netcraftsmen, with tasks including network
design, security, QoS, and IP telephony for several major enterprise customers. He

has reviewed a large number of books for Cisco Press and other publishers, and has
authored or managed development of several courses for Cisco and others. Pete
writes articles for Enterprise Networking Magazine. He can also sometimes be found
presenting his own seminars at East Coast Cisco offices, on topics ranging from
campus design to WLAN security. The articles and seminars can be found at
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Acknowledgments
I would like to thank the staff and contractors at Cisco Press for their hard work on
this book project. I am also grateful for the hard work of the technical reviewers,
Matthew Birkner, Blair Buchanan, and Dr. Peter Welcher. They read the entire
manuscript and made many helpful suggestions. I take responsibility for any errors
and for my decision to retain more legacy material than the reviewers advised. I also
wish to thank the technical reviewers for the first edition, Dr. Alex Cannara, David
Jansson, and Hank Mauldin. Their terrific contributions are still evident in the second
edition.
I was remiss in not acknowledging Howard Berkowitz in the first edition and I am
glad to have the opportunity to remedy that now. I have learned an enormous
amount from Howard since I first met him in 1995 when he reviewed my work on the
Cisco Internetwork Design course. I have remained a fan ever since and
acknowledge his influence on many of the concepts in this book.
I would also like to thank other gurus with whom I have worked over the years,
including Joseph Bardwell and Anita Lenk from Connect802, and my colleagues on
the Group Study discussion group who have answered many technical questions.
This includes, but is not limited to, Paul Borghese (the moderator), Marty Adkins,
Ken Chipps, Daniel Cotts, Annlee Hines, Chuck Larrieu, Larry Letterman, Tom Lisa,
David Madland, Jenny McLeod, John Neiberger, Fred Reimer, Peter van Oene, Scott

Vermillion, Alaerte Vidali, and Cyrus Wekesa.
I am grateful for my colleagues and students at Southern Oregon University who
have engaged me in many interesting technical dialogues. This includes, but is not
limited to, Dr. Dan Wilson, Dr. Lynn Ackler, Louis Kowolowski, Jason Moreland (Little
Jason), and Jason Winters (Big Jason).
Finally, I would like to thank Alan Oppenheimer who throughout this project acted as
my agent, technical advisor, therapist, chef, and best friend. Please don't blame him
for the AppleTalk examples in the book. As mentioned, I take responsibility for my
decision to retain legacy material where I thought it would help the reader
understand protocol behavior and development.
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Icons Used in This Book
[View full size image]

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Command Syntax Conventions
The conventions used to present command syntax in this book are the same
conventions used in the IOS Command Reference. The Command Reference
describes these conventions as follows:
•

•

•
•
•
•

Boldface indicates commands and keywords that are entered literally as
shown. In actual configuration examples and output (not general command
syntax), boldface indicates commands 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.
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Introduction
New business practices are driving changes in enterprise networks. The transition
from an industrial to an information economy has changed how employees do their
jobs, and the emergence of a global economy of unprecedented competitiveness has
accelerated the speed at which companies must adapt to technological and financial
changes.
To reduce the time to develop and market products, companies are empowering
employees to make strategic decisions that require access to sales, marketing,
financial, and engineering data. Employees at corporate headquarters and in
worldwide field offices, as well as telecommuters in home offices, need immediate

access to data, regardless of whether the data is on centralized or departmental
servers.
To develop, sell, and distribute products into domestic and foreign markets,
businesses are forming alliances with local and international partners. Businesses are
carefully planning their network designs to meet security goals while also offering
network access to resellers, vendors, customers, prospective customers, and
contract workers located all over the world.
To accommodate increasing requirements for remote access, security, bandwidth,
scalability, and reliability, vendors and standards bodies introduce new protocols and
technologies at a rapid rate. Network designers are challenged to develop state-ofthe-art networks even though the state of the art is continually changing.
Whether you are a novice network designer or a seasoned network architect, you
probably have concerns about how to design a network that can keep pace with the
accelerating changes in the internetworking industry. The goal of this book is to
teach a systematic design methodology that can help you meet an organization's
requirements, regardless of the newness or complexity of applications and
technologies.
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Changes for the Second Edition
The first edition of Top-Down Network Design taught a classic method for network
design that is still relevant today. A top-down process focuses on requirements
analysis and architectural design, which should be completed before the selection of
specific network components. A top-down process can be applied to networks of all
sorts, including old-fashioned networks with 10-Mbps Ethernet or Token Ring, as well
as modern networks with Gigabit Ethernet, Synchronous Optical Network (SONET),
and wireless networking.
Despite the timeless nature of the top-down process, some adjustments must be

made to accommodate modern business practices. Business goals fluctuate with
political and economic changes. Business goals also evolve as Human Resources
(HR) policies change. Network design must evolve with these changes.
In the past few years, the following business goals and concerns have emerged or
re-emerged as top-priority requirements for network designs:
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•
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•
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A need to support mobile and remote users
An increased need for network security
An increased need for resilient networks
An increased need for manageable networks
A renewed recognition that network projects must be prioritized based on
fiscal goals
A renewed focus on the economic benefits of merging voice and data
networks

To address these business requirements, the second edition of Top-Down Network
Design has new and updated material on the following topics:
•
•
•
•
•
•
•

•
•

Wireless networks
Virtual private networks (VPNs)
Network security
Network redundancy
Modularity in network designs
Dynamic addressing for IPv4 and IPv6
New network design and management tools
Ethernet scalability options, including 10-Gbps Ethernet, Metro Ethernet, and
Long-Reach Ethernet
Designing networks that can carry voice and data traffic
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Objectives
The purpose of Top-Down Network Design, Second Edition is to help you design
networks that meet a customer's business and technical goals. Whether your
customer is another department within your own company or an external client, this
book provides you with tested processes and tools to help you understand traffic
flow, protocol behavior, and internetworking technologies. After completing this
book, you will be equipped to design enterprise networks that meet a customer's
requirements for functionality, capacity, performance, availability, scalability,
affordability, security, and manageability.
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Audience
This book is for you if you are an internetworking professional responsible for
designing and maintaining medium- to large-sized enterprise networks. If you are a
network engineer, architect, or technician who has a working knowledge of network
protocols and technologies, this book will provide you with practical advice on
applying your knowledge to internetwork design.
This book also includes useful information for consultants, systems engineers, and
sales engineers who design corporate networks for clients. In the fast-paced presales
environment of many systems engineers, it often is difficult to slow down and insist
on a top-down, structured systems analysis approach. Wherever possible, this book
includes shortcuts and assumptions that can be made to speed up the network
design process.
Finally, this book is useful for undergraduate and graduate students in computer
science and information technology disciplines. Students who have taken one or two
courses in networking theory will find Top-Down Network Design, Second Edition an
approachable introduction to the engineering and business issues related to
developing real-world networks that solve typical business problems.
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Organization
This book is built around the steps for top-down network design. It is organized into
four parts that correspond to the major phases of network design.
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Part I: Identifying Your Customer's Needs and
Goals
Part I covers the requirements analysis phase. This phase starts with identifying
business goals and technical requirements. The task of characterizing the existing
network, including the architecture and performance of major network segments and
devices, follows. The last step in this phase is to analyze network traffic, including
traffic flow and load, protocol behavior, and quality of service (QoS) requirements.
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Part II: Logical Network Design
During the logical network design phase, the network designer develops a network
topology. Depending on the size of the network and traffic characteristics, the
topology can range from simple to complex, requiring hierarchy and modularity.
During this phase, the network designer also devises a network layer addressing
model, and selects switching and routing protocols. Logical design also includes
security planning, network management design, and the initial investigation into
which service providers can meet wide-area networking (WAN) and remote-access
requirements.
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Part III: Physical Network Design
During the physical design phase, specific technologies and products to realize the

logical design are selected. Physical network design starts with the selection of
technologies and devices for campus networks, including cabling, Ethernet switches,
wireless access points, wireless bridges, and routers. Selecting technologies and
devices for remote-access and WAN needs follows. Also, the investigation into
service providers, which began during the logical design phase, must be completed
during this phase.
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Part IV: Testing, Optimizing, and Documenting
Your Network Design
The final steps in top-down network design are to write and implement a test plan,
build a prototype or pilot, optimize the network design, and document your work
with a network design proposal. If your test results indicate any performance
problems, then during this phase you should update your design to include such
optimization features as traffic shaping and advanced router queuing and switching
mechanisms.
Appendix A characterizes network traffic when network stations boot. It provides
information for IP, AppleTalk, NetWare, NetBIOS, and Systems Network Architecture
(SNA) sessions. Appendix B is a list of references and recommended reading. A
glossary of networking terms follows Appendix B.
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Companion Website
Top-Down Network Design, Second Edition has a companion website at

www.topdownbook.com. The companion website includes updates to the book, links
to white papers, and supplemental information about design resources.
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