Top-Down Network Design, 3rd edition
Published by Cisco Press (August 24, 2010) © 2011
- Priscilla Oppenheimer
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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
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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 has taught more than 3000 network engineers from most of the Fortune 500 companies. Her employment at such companies as Apple Computer, Network General, and Cisco 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. Priscilla teaches network design, configuration, and troubleshooting around the world and practices what she preaches in her network consulting business.
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