Third Edition
Priscilla Oppenheimer
Cisco Press
800 East 96th Street Indianapolis, IN 46240
vi Тор-Down Network Design
Contents at a Glance
Introduction xxiiPart I Identifying Your Customer's Needs and Goals 1
Chapter 1 Analyzing Business Goals and Constraints 3 Chapter 2 Analyzing Technical Goals and Tradeoffs 25 Chapter 3 Characterizing the Existing Internetwork 59 Chapter 4 Characterizing Network Traffic 87
Part II Logical Network Design 117
Chapter 5 Designing a Network Topology 119
Chapter 6 Designing Models for Addressing and Numbering 167 Chapter 7 Selecting Switching and Routing Protocols 199 Chapter 8 Developing Network Security Strategies 233 Chapter 9 Developing Network Management Strategies 263
Part III Physical Network Design 281
Chapter 10 Selecting Technologies and Devices for Campus Networks 283 Chapter 11 Selecting Technologies and Devices for Enterprise Networks 319
Part IV Testing, Optimizing, and Documenting Your Network Design 351
Chapter 12 Testing Your Network Design 353 Chapter 13 Optimizing Your Network Design 367 Chapter 14 Documenting Your Network Design 393
Glossary 407 Index 435
Introduction xxii
Part I Identifying Your Customer's Needs and Goals 1
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 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
Тор-Down Network Design
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 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
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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
Controiled-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 Que stions 114 Design Scenario 115 Summary for Part I 115
Part II Logical Network Design 117
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
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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
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 Тор-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
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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 22 9
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 281
Chapter 10 Selecting Technologies and Devices for Campus Networks 283
LAN Cabling Plant Design 284 Cabling Topologies 284
xvi Тор-Down Network Design
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
Re view Que stions 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
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
xviii Тор-Down Network Design
Part IV Testing, Optimizing, and Documenting Your Network Design 351
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
NetlQ 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
xx Тор-Down Network Design
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