Top-Down Network Design

• Copyright 2011
• Dimensions: 7-3/8" x 9-1/8"
• Edition: 1st

• eBook
• ISBN-10: 0-13-343498-2
• ISBN-13: 978-0-13-343498-9

Objectives

The purpose of Top-Down Network Design, Third 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.

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, Third Edition, an approachable introduction to the engineering and business issues related to developing real-world networks that solve typical business problems.

Changes for the Third Edition

Networks have changed in many ways since the second edition was published. Many legacy technologies have disappeared and are no longer covered in the book. In addition, modern networks have become multifaceted, providing support for numerous bandwidth-hungry applications and a variety of devices, ranging from smart phones to tablet PCs to high-end servers. Modern users expect the network to be available all the time, from any device, and to let them securely collaborate with coworkers, friends, and family. Networks today support voice, video, high-definition TV, desktop sharing, virtual meetings, online training, virtual reality, and applications that we can’t even imagine that brilliant college students are busily creating in their dorm rooms.

As applications rapidly change and put more demand on networks, the need to teach a systematic approach to network design is even more important than ever. With that need in mind, the third edition has been retooled to make it an ideal textbook for college students. The third edition features review questions and design scenarios at the end of each chapter to help students learn top-down network design.

To address new demands on modern networks, the third edition of Top-Down Network Design also has updated material on the following topics:

¿ Network redundancy

¿ Modularity in network designs

¿ The Cisco SAFE security reference architecture

¿ The Rapid Spanning Tree Protocol (RSTP)

¿ Internet Protocol version 6 (IPv6)

¿ Ethernet scalability options, including 10-Gbps Ethernet and Metro Ethernet

¿ Network design and management tools

Table of Contents

Introduction

Part I Identifying Your Customer’s Needs and Goals

Chapter 1 Analyzing Business Goals and Constraints 3

Using a Top-Down Network Design Methodology 3

    Using a Structured Network Design Process 5

    Systems Development Life Cycles 6

    Plan Design Implement Operate Optimize (PDIOO) Network Life Cycle 7

Analyzing Business Goals 8

    Working with Your Client 8

    Changes in Enterprise Networks 10

        Networks Must Make Business Sense 10

        Networks Offer a Service 11

        The Need to Support Mobile Users 12

        The Importance of Network Security and Resiliency 12

    Typical Network Design Business Goals 13

    Identifying the Scope of a Network Design Project 14

    Identifying a Customer’s Network Applications 16

Analyzing Business Constraints 19

    Politics and Policies 19

    Budgetary and Staffing Constraints 20

    Project Scheduling 21

Business Goals Checklist 22

Summary 23

Review Questions 23

Design Scenario 24

Chapter 2 Analyzing Technical Goals and Tradeoffs 25

Scalability 25

    Planning for Expansion 26

    Expanding Access to Data 26

    Constraints on Scalability 27

Availability 27

    Disaster Recovery 28

    Specifying Availability Requirements 29

        Five Nines Availability 30

        The Cost of Downtime 31

        Mean Time Between Failure and Mean Time to Repair 31

Network Performance 32

    Network Performance Definitions 33

    Optimum Network Utilization 34

    Throughput 35

        Throughput of Internetworking Devices 36

        Application Layer Throughput 37

    Accuracy 38

    Efficiency 39

    Delay and Delay Variation 40

        Causes of Delay 41

        Delay Variation 43

    Response Time 44

Security 44

    Identifying Network Assets 45

    Analyzing Security Risks 46

        Reconnaissance Attacks 47

        Denial-of-Service Attacks 48

    Developing Security Requirements 48

Manageability 49

Usability 50

Adaptability 50

Affordability 51

Making Network Design Tradeoffs 52

Technical Goals Checklist 54

Summary 55

Review Questions 56

Design Scenario 56

Chapter 3 Characterizing the Existing Internetwork 59

Characterizing the Network Infrastructure 59

    Developing a Network Map 60

        Characterizing Large Internetworks 60

        Characterizing the Logical Architecture 62

        Developing a Modular Block Diagram 64

    Characterizing Network Addressing and Naming 64

    Characterizing Wiring and Media 65

    Checking Architectural and Environmental Constraints 68

        Checking a Site for a Wireless Installation 69

        Performing a Wireless Site Survey 70

Checking the Health of the Existing Internetwork 71

    Developing a Baseline of Network Performance 72

    Analyzing Network Availability 73

    Analyzing Network Utilization 73

        Measuring Bandwidth Utilization by Protocol 75

    Analyzing Network Accuracy 76

        Analyzing Errors on Switched Ethernet Networks 77

    Analyzing Network Efficiency 79

    Analyzing Delay and Response Time 80

    Checking the Status of Major Routers, Switches, and Firewalls 82

Network Health Checklist 83

Summary 84

Review Questions 84

Hands-On Project 85

Design Scenario 85

Chapter 4 Characterizing Network Traffic 87

Characterizing Traffic Flow 87

    Identifying Major Traffic Sources and Stores 87

    Documenting Traffic Flow on the Existing Network 89

    Characterizing Types of Traffic Flow for New Network Applications 90

        Terminal/Host Traffic Flow 91

        Client/Server Traffic Flow 91

        Peer-to-Peer Traffic Flow 93

        Server/Server Traffic Flow 94

        Distributed Computing Traffic Flow 94

        Traffic Flow in Voice over IP Networks 94

    Documenting Traffic Flow for New and Existing Network Applications 95

Characterizing Traffic Load 96

    Calculating Theoretical Traffic Load 97

    Documenting Application-Usage Patterns 99

    Refining Estimates of Traffic Load Caused by Applications 99

    Estimating Traffic Load Caused by Routing Protocols 101

Characterizing Traffic Behavior 101

    Broadcast/Multicast Behavior 101

    Network Efficiency 102

        Frame Size 103

        Windowing and Flow Control 103

        Error-Recovery Mechanisms 104

Characterizing Quality of Service Requirements 105

    ATM QoS Specifications 106

        Constant Bit Rate Service Category 107

        Real-time Variable Bit Rate Service Category 107

        Non-real-time Variable Bit Rate Service Category 107

        Unspecified Bit Rate Service Category 108

        Available Bit Rate Service Category 108

        Guaranteed Frame Rate Service Category 108

    IETF Integrated Services Working Group QoS Specifications 109

        Controlled-Load Service 110

        Guaranteed Service 110

    IETF Differentiated Services Working Group QoS Specifications 111

    Grade of Service Requirements for Voice Applications 112

    Documenting QoS Requirements 113

Network Traffic Checklist 114

Summary 114

Review Questions 114

Design Scenario 115

Summary for Part I 115

Part II Logical Network Design

Chapter 5 Designing a Network Topology 119

Hierarchical Network Design 120

    Why Use a Hierarchical Network Design Model? 121

    Flat Versus Hierarchical Topologies 122

        Flat WAN Topologies 122

        Flat LAN Topologies 123

    Mesh Versus Hierarchical-Mesh Topologies 124

    Classic Three-Layer Hierarchical Model 125

        Core Layer 127

        Distribution Layer 127

        Access Layer 128

    Guidelines for Hierarchical Network Design 128

Redundant Network Design Topologies 130

    Backup Paths 131

    Load Sharing 132

Modular Network Design 133

    Cisco SAFE Security Reference Architecture 133

Designing a Campus Network Design Topology 135

    Spanning Tree Protocol 135

        Spanning Tree Cost Values 136

        Rapid Spanning Tree Protocol 137

        RSTP Convergence and Reconvergence 138

        Selecting the Root Bridge 139

        Scaling the Spanning Tree Protocol 140

    Virtual LANs 141

        Fundamental VLAN Designs 142

    Wireless LANs 144

        Positioning an Access Point for Maximum Coverage 145

        WLANs and VLANs 146

        Redundant Wireless Access Points 146

    Redundancy and Load Sharing in Wired LANs 147

    Server Redundancy 148

    Workstation-to-Router Redundancy 150

        Hot Standby Router Protocol 152

        Gateway Load Balancing Protocol 153

Designing the Enterprise Edge Topology 153

    Redundant WAN Segments 153

        Circuit Diversity 154

    Multihoming the Internet Connection 154

    Virtual Private Networking 157

        Site-to-Site VPNs 158

        Remote-Access VPNs 159

    Service Provider Edge 160

Secure Network Design Topologies 162

    Planning for Physical Security 162

    Meeting Security Goals with Firewall Topologies 162

Summary 163

Review Questions 165

Design Scenario 165

Chapter 6 Designing Models for Addressing and Numbering 167

Guidelines for Assigning Network Layer Addresses 168

    Using a Structured Model for Network Layer Addressing 168

    Administering Addresses by a Central Authority 169

    Distributing Authority for Addressing 170

    Using Dynamic Addressing for End Systems 170

        IP Dynamic Addressing 171

        IP Version 6 Dynamic Addressing 174

        Zero Configuration Networking 175

    Using Private Addresses in an IP Environment 175

        Caveats with Private Addressing 177

        Network Address Translation 177

Using a Hierarchical Model for Assigning Addresses 178

    Why Use a Hierarchical Model for Addressing and Routing? 178

    Hierarchical Routing 179

    Classless Interdomain Routing 179

    Classless Routing Versus Classful Routing 180

    Route Summarization (Aggregation) 181

        Route Summarization Example 182

        Route Summarization Tips 183

    Discontiguous Subnets 183

    Mobile Hosts 184

    Variable-Length Subnet Masking 185

    Hierarchy in IP Version 6 Addresses 186

        Link-Local Addresses 187

        Global Unicast Addresses 188

        IPv6 Addresses with Embedded IPv4 Addresses 189

Designing a Model for Naming 189

    Distributing Authority for Naming 190

    Guidelines for Assigning Names 191

    Assigning Names in a NetBIOS Environment 192

    Assigning Names in an IP Environment 193

        The Domain Name System 193

        Dynamic DNS Names 194

        IPv6 Name Resolution 195

Summary 195

Review Questions 196

Design Scenario 197

Chapter 7 Selecting Switching and Routing Protocols 199

Making Decisions as Part of the Top-Down Network Design Process 200

Selecting Switching Protocols 201

    Switching and the OSI Layers 202

    Transparent Bridging 202

    Selecting Spanning Tree Protocol Enhancements 203

        PortFast 204

        UplinkFast and BackboneFast 204

        Unidirectional Link Detection 205

    LoopGuard 206

    Protocols for Transporting VLAN Information 207

        IEEE 802.1Q 207

        Dynamic Trunk Protocol 208

        VLAN Trunking Protocol 208

Selecting Routing Protocols 209

    Characterizing Routing Protocols 209

        Distance-Vector Routing Protocols 210

        Link-State Routing Protocols 212

        Routing Protocol Metrics 214

        Hierarchical Versus Nonhierarchical Routing Protocols 214

        Interior Versus Exterior Routing Protocols 214

        Classful Versus Classless Routing Protocols 214

        Dynamic Versus Static and Default Routing 215

        On-Demand Routing 216

        Scalability Constraints for Routing Protocols 216

        Routing Protocol Convergence 217

    IP Routing 218

        Routing Information Protocol 218

        Enhanced Interior Gateway Routing Protocol 219

        Open Shortest Path First 221

        Intermediate System-to-Intermediate System 224

        Border Gateway Protocol 225

    Using Multiple Routing Protocols in an Internetwork 225

        Routing Protocols and the Hierarchical Design Model 226

        Redistribution Between Routing Protocols 227

        Integrated Routing and Bridging 229

A Summary of Routing Protocols 230

Summary 231

Review Questions 231

Design Scenario 232

Chapter 8 Developing Network Security Strategies 233

Network Security Design 233

    Identifying Network Assets 234

    Analyzing Security Risks 234

    Analyzing Security Requirements and Tradeoffs 235

    Developing a Security Plan 235

    Developing a Security Policy 236

        Components of a Security Policy 237

    Developing Security Procedures 237

    Maintaining Security 237

Security Mechanisms 238

    Physical Security 238

    Authentication 239

    Authorization 239

    Accounting (Auditing) 240

    Data Encryption 240

        Public/Private Key Encryption 241

    Packet Filters 243

    Firewalls 244

    Intrusion Detection and Prevention Systems 244

Modularizing Security Design 245

    Securing Internet Connections 245

        Securing Public Servers 246

        Securing E-Commerce Servers 247

    Securing Remote-Access and VPNs 248

        Securing Remote-Access Technologies 248

        Securing VPNs 249

    Securing Network Services and Network Management 250

    Securing Server Farms 251

    Securing User Services 252

    Securing Wireless Networks 253

        Authentication in Wireless Networks 254

        Data Privacy in Wireless Networks 258

Summary 261

Review Questions 261

Design Scenario 262

Chapter 9 Developing Network Management Strategies 263

Network Management Design 263

    Proactive Network Management 264

    Network Management Processes 264

        Fault Management 265

        Configuration Management 266

        Accounting Management 266

        Performance Management 266

        Security Management 268

Network Management Architectures 269

    In-Band Versus Out-of-Band Monitoring 270

    Centralized Versus Distributed Monitoring 270

Selecting Network Management Tools and Protocols 271

    Selecting Tools for Network Management 271

    Simple Network Management Protocol 271

        Management Information Bases (MIB) 272

        Remote Monitoring (RMON) 273

    Cisco Discovery Protocol 274

    Cisco NetFlow Accounting 276

    Estimating Network Traffic Caused by Network Management 276

Summary 277

Review Questions 278

Design Scenario 278

Summary for Part II 279

Part III Physical Network Design

Chapter 10 Selecting Technologies and Devices for Campus Networks 283

LAN Cabling Plant Design 284

    Cabling Topologies 284

        Building-Cabling Topologies 285

        Campus-Cabling Topologies 285

    Types of Cables 285

LAN Technologies 289

    Ethernet Basics 290

        Ethernet and IEEE 802.3 290

    Ethernet Technology Choices 291

        Half-Duplex and Full-Duplex Ethernet 292

        100-Mbps Ethernet 292

        Gigabit Ethernet 293

        10-Gbps Ethernet 295

Selecting Internetworking Devices for a Campus Network Design 299

    Criteria for Selecting Campus Internetworking Devices 300

    Optimization Features on Campus Internetworking Devices 302

Example of a Campus Network Design 303

    Background Information for the Campus Network Design Project 303

    Business Goals 304

    Technical Goals 304

    Network Applications 305

    User Communities 306

    Data Stores (Servers) 307

    Current Network at WVCC 307

        Traffic Characteristics of Network Applications 310

        Summary of Traffic Flows 311

        Performance Characteristics of the Current Network 312

    Network Redesign for WVCC 313

        Optimized IP Addressing and Routing for the Campus Backbone 313

        Wireless Network 314

        Improved Performance and Security for the Edge of the Network 315

Summary 316

Review Questions 317

Design Scenario 317

Chapter 11 Selecting Technologies and Devices for Enterprise Networks 319

Remote-Access Technologies 320

    PPP 321

        Multilink PPP and Multichassis Multilink PPP 321

        Password Authentication Protocol and Challenge Handshake

        Authentication Protocol 322

    Cable Modem Remote Access 323

        Challenges Associated with Cable Modem Systems 324

    Digital Subscriber Line Remote Access 325

        Other DSL Implementations 326

        PPP and ADSL 326

Selecting Remote-Access Devices for an Enterprise

    Network Design 327

    Selecting Devices for Remote Users 327

    Selecting Devices for the Central Site 328

WAN Technologies 328

    Systems for Provisioning WAN Bandwidth 329

    Leased Lines 330

    Synchronous Optical Network 331

    Frame Relay 332

        Frame Relay Hub-and-Spoke Topologies and Subinterfaces 333

        Frame Relay Congestion Control Mechanisms 335

        Frame Relay Traffic Control 335

        Frame Relay/ATM Interworking 336

    ATM 337

        Ethernet over ATM 337

    Metro Ethernet 338

    Selecting Routers for an Enterprise WAN Design 339

    Selecting a WAN Service Provider 340

Example of a WAN Design 341

    Background Information for the WAN Design Project 341

    Business and Technical Goals 342

    Network Applications 343

    User Communities 343

    Data Stores (Servers) 344

    Current Network 344

    Traffic Characteristics of the Existing WAN 345

    WAN Design for Klamath Paper Products 346

Summary 348

Review Questions 349

Design Scenario 349

Summary for Part III 350

Part IV Testing, Optimizing, and Documenting Your Network Design

Chapter 12 Testing Your Network Design 353

Using Industry Tests 354

Building and Testing a Prototype Network System 355

    Determining the Scope of a Prototype System 355

    Testing a Prototype on a Production Network 356

Writing and Implementing a Test Plan for Your Network Design 357

    Developing Test Objectives and Acceptance Criteria 357

    Determining the Types of Tests to Run 358

    Documenting Network Equipment and Other Resources 359

    Writing Test Scripts 360

    Documenting the Project Timeline 361

    Implementing the Test Plan 361

Tools for Testing a Network Design 362

    Types of Tools 362

    Examples of Network Testing Tools 363

        CiscoWorks Internetwork Performance Monitor 364

        WANDL Network Planning and Analysis Tools 364

        OPNET Technologies 364

        Ixia Tools 365

        NetIQ Voice and Video Management Solution 365

        NetPredict’s NetPredictor 365

Summary 366

Review Questions 366

Design Scenario 366

Chapter 13 Optimizing Your Network Design 367

Optimizing Bandwidth Usage with IP Multicast Technologies 368

    IP Multicast Addressing 369

    Internet Group Management Protocol 370

    Multicast Routing Protocols 370

        Distance Vector Multicast Routing Protocol 371

        Protocol Independent Multicast 371

Reducing Serialization Delay 372

    Link-Layer Fragmentation and Interleaving 373

    Compressed Real-Time Transport Protocol 374

Optimizing Network Performance to Meet Quality of Service Requirements 374

    IP Precedence and Type of Service 375

        IP Differentiated Services Field 376

    Resource Reservation Protocol 377

    Common Open Policy Service Protocol 379

    Classifying LAN Traffic 379

Cisco IOS Features for Optimizing Network Performance 380

    Switching Techniques 380

        Classic Methods for Layer 3 Packet Switching 381

        NetFlow Switching 382

        Cisco Express Forwarding 382

    Queuing Services 383

        First-In, First-Out Queuing 383

        Priority Queuing 384

        Custom Queuing 384

        Weighted Fair Queuing 385

        Class-Based Weighted Fair Queuing 386

        Low-Latency Queuing 387

    Random Early Detection 388

        Weighted Random Early Detection 388

    Traffic Shaping 389

    Committed Access Rate 389

Summary 389

Review Questions 390

Design Scenario 391

Chapter 14 Documenting Your Network Design 393

Responding to a Customer’s Request for Proposal 394

Contents of a Network Design Document 395

    Executive Summary 396

    Project Goal 396

    Project Scope 396

    Design Requirements 397

        Business Goals 397

        Technical Goals 398

        User Communities and Data Stores 399

        Network Applications 399

    Current State of the Network 399

    Logical Design 400

    Physical Design 400

    Results of Network Design Testing 401

    Implementation Plan 401

        Project Schedule 402

    Project Budget 403

        Return on Investment 403

    Design Document Appendix 404

Summary 404

Review Questions 405

Design Scenario 405

Glossary 407

9781587202834    TOC    8/2/2010

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