Art of Network Architecture, The: Business-Driven Design

Cisco Press
Russ White / Denise Donohue  
Total pages
April 2014
Related Titles

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Art of Network Architecture, The: Business-Driven Design
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The Art of Network Architecture is the first book that places business needs and capabilities at the center of the process of architecting and evolving networks, where it belongs. Three pioneering network architects show how to evaluate both business and application requirements from a network designer’s perspective, identifying crucial upfront questions that can help the reader shape networks that support current business strategy and provide flexibility for the future.


  • The first business-centered, business-driven guide to architecting and evolving networks
  • Teaches to ask the right business questions upfront, to evaluate business and application requirements from a network designer’s perspective
  • Three chapter-length case studies: designing an L3VPN core, outsourcing to cloud services, and supporting BYOD
  • Written by three of the world’s most experienced and successful network architects
  • This book will come with power points of the book's figures to assist in classroom use.

Table of Contents

Introduction xx

Part I Framing the Problem

Chapter 1 Business and Technology 1

Business Drives Technology 2

The Business Environment 2

 The Big Picture 3

 The Competition 4

The Business Side of the Network 5

 Technologies and Applications 5

 Network Evaluation 6

The Network’s Customers 6

 Internal Users 7

 External Users 8

 Guest Users 9

Technology Drives Business 9

Part II Business-Driven Design

Chapter 2 Designing for Change 11

Organic Growth and Decline 12

Mergers, Acquisitions, and Divestments 14

Centralizing Versus Decentralizing 15

Chapter 3 Improving Business Operations 19

Workflow 19

Matching Data Flow and Network Design 20

 Person-to-Person Communication 21

 Person-to-Machine Communication 21

 Machine-to-Machine Communication 22

 Bringing It All Together 23


BYOD Options 24

BYOD Design Considerations 27

BYOD Policy 28

Business Continuity 29

Business Continuity Versus Disaster Recovery 29

Business Continuity Planning 30

Business Continuity Design Considerations 31

Summary 33

Part III Tools of the Trade

Chapter 4 Models 35

The Seven-Layer Model 36

Problems with the Seven-Layer Model 38

The Four-Layer Model 38

Iterative Layering Model 39

Connection-Oriented and Connectionless 41

A Hybrid Model 42

The Control Plane 43

 What Am I Trying to Reach? 43

 Where Is It? 44

 How Do I Get There? 45

 Other Network Metadata 46

Control Plane Relationships 46

 Routing 46

 Quality of Service 48

 Network Measurement and Management 49

 Interaction Between Control Planes 49

Reactive and Proactive 51

The Waterfall Model 53

Places in the Network 54

Summary 56

Chapter 5 Underlying Support 57

Questions You Should Ask 57

What Happens When the Link Fails? 57

What Types of Virtualization Can Be Run Over This Link? 58

How Does the Link Support Quality of Service? 59

 Marking Packets 59

 Queues and Rate Limiters 59

 Speeds and Feeds Versus Quality of Service 60

Spanning Tree 61


TRILL Operation 62

TRILL in the Design Landscape 64

TRILL and the Fabrics 65

Final Thoughts on the Physical Layer 65

Chapter 6 Principles of Modularity 67

Why Modularize? 68

Machine Level Information Overload 68

 Machine Level Information Overload Defined 69

 Reducing Machine Information Level Overload 71

 Separating Complexity from Complexity 72

Human Level Information Overload 73

 Clearly Assigned Functionality 74

 Repeatable Configurations 75

Mean Time to Repair and Modularization 75

How Do You Modularize? 77

Topology and Reachability 77

 Aggregating Topology Information at Router B 78

 Aggregating Reachability Information at Router B 78

 Filtering Routing Information at Router B 79

Splitting Failure Domains Horizontally and Vertically 79

Modularization and Optimization 81

Summary 82

Chapter 7 Applying Modularity 83

What Is Hierarchical Design? 83

A Hub-and-Spoke Design Pattern 84

An Architectural Methodology 85

 Assign Each Module One Function 85

 All Modules at a Given Level Should Share Common Functionality 86

 Build Solid Redundancy at the Intermodule Level 87

 Hide Information at Module Edges 88

Typical Hierarchical Design Patterns 89

Virtualization 90

What Is Virtualization? 90

 Virtualization as Vertical Hierarchy 93

Why We Virtualize 93

 Communities of Interest 94

 Network Desegmentation 94

 Separation of Failure Domains 94

Consequences of Network Virtualization 95

Final Thoughts on Applying Modularity 96

Chapter 8 Weathering Storms 97

Redundancy as Resilience 98

Network Availability Basics 98

Adding Redundancy 99

MTTR, Resilience, and Redundancy 100

Limits on Control Plane Convergence 100

Feedback Loops 102

The Interaction Between MTTR and Redundancy 103

Fast Convergence Techniques 104

Detecting the Topology Change 104

Propagating Information About the Change 105

Calculating the New Best Path 106

Switching to the New Best Path 107

The Impact of Fast Convergence 107

Fast Reroute 108

P/Q Space 109

Loop-Free Alternates 110

Remote Loop-Free Alternates 110

Not-Via Fast Reroute 111

Maximally Redundant Trees 113

Final Thoughts on Fast Reroute 115

The Human Side of Resilience 115

Chapter 9 Securing the Premises 117

The OODA Loop 118

Observe 119

Orient 122

Decide 124

Act 125

Brittleness 125

Building Defense In 126

Modularization 128

 Modularity, Failure Domains, and Security 128

 Modularity, Complexity, and Security 128

 Modularity, Functionality, and Security 129

Resilience 129

Some Practical Considerations 129

Close a Door, Open a Door 129

Beware of Virtualization 131

Social Engineering 131

Summary 132

Chapter 10 Measure Twice 133

Why Manage? 133

Justifying the Cost of the Network 134

Planning 135

Decreasing the Mean Time to Repair 136

Increasing the Mean Time Between Mistakes 136

Management Models 137

Fault, Configuration, Accounting, Performance, and Security 137

Observe, Orient, Decide, and Act (OODA) 138

Deploying Management 140

Loosen the Connection Between Collection and Management 140

Sampling Considerations 141

Where and What 142

 End-to-End/Network 142

 Interface/Transport 143

 Failure Domain/Control Plane 143

Bare Necessities 144

Summary 145

Part IV Choosing Materials

Chapter 11 The Floor Plan 147

Rings 147

Scaling Characteristics 147

Resilience Characteristics 149

Convergence Characteristics 151

Generalizing Ring Convergence 154

Final Thoughts on Ring Topologies 155

Full Mesh 155

Clos Networks 157

Clos and the Control Plane 159

Clos and Capacity Planning 160

Partial Mesh 161

Disjoint Parallel Planes 162

Advantages of Disjoint Topologies 163

Added Complexity 164

The Bottom Line 164

Divergent Data Planes 165

Cubes 166

Toroid Topologies 167

Summary 169

Chapter 12 Building the Second Floor 171

What Is a Tunnel? 171

Is MPLS Tunneling? 173

Fundamental Virtualization Questions 175

Data Plane Interaction 176

Control Plane Considerations 177

 Control Plane Interaction 177

 Scaling 178

Multicast 179

Security in a Virtual Topology 180

MPLS-Based L3VPNs 182

Operational Overview 182

Fundamental Questions 185

The Maximum Transmission Unit 185

Quality of Service 186

Control Plane Interaction 186

Scaling 187

Multicast 188

Security in MPLS-Based L3VPNs 188

MPLS-Based L3VPN Summary 188


Operational Overview 189

Fundamental Questions 190

Control Plane Interaction 190

Scaling 190

VXLAN Summary 191

Summary 191

Chapter 13 Routing Choices 193

Which Routing Protocol? 194

How Fast Does the Routing Protocol Converge? 194

Is the Routing Protocol Proprietary? 196

How Easy Is the Routing Protocol to Configure and Troubleshoot? 197

Which Protocol Degrades in a Way That Works with the Business? 198

Which Protocol Works Best on the Topology the Business Usually Builds? 199

Which Protocol is Right? 200

IPv6 Considerations 202

What Is the Shape of the Deployment? 202

How Does Your Deployment Grow? 202

 Topological Deployment 203

 Virtual Topology Deployment 203

Where Are the Policy Edges? 203

Routing Protocol Interaction with IPv6 204

 IS-IS Interaction with IPv6 204

 OSPF Interaction with IPv6 205

 EIGRP Interaction with IPv6 206

Deploying BGP 206

Why Deploy BGP? 207

 Complexity of Purpose 207

 Complexity of Place 208

 Complexity of Policy 208

BGP Deployment Models 209

 iBGP Edge-to-Edge (Overlay Model) 209

 iBGP Core 210

 eBGP Edge-to-Edge (Core and Aggregation Model) 211

Summary 212

Chapter 14 Considering Complexity 213

Control Plane State 213

Concepts of Control Plane State 214

Network Stretch 215

Configuration State 217

Control Plane Policy Dispersion 218

Data Plane State 220

Reaction Time 223

Managing Complexity Trade-offs 225

Part V Current and Future Trends

Chapter 15 Network in Motion 227

The Business Case for Mobility 228

A Campus Bus Service 228

A Mobile Retail Analysis Team 229

Shifting Load 230

Pinning the Hard Problems into Place 230

Mobility Requires State 231

Mobility Requires Speed 231

State Must Be Topologically Located 232

State and the Network Layers 233

IP-Centric Mobility Solutions 234

Identifier-Locator Network Protocol (ILNP) 235

Locator Identifier Separation Protocol (LISP) 237

Mobile IP 238

Host Routing 239

Mobile Ad-Hoc Networks (MANET) 240

Dynamic DNS 242

Final Thoughts on Mobility Solutions 243

Remote Access Solutions 244

Separate Network Access from Application Access 244

Consider Cloud-Based Solutions 245

Keep Flexibility as a Goal 246

Consider Total Cost 248

Consider Making Remote Access the Norm 248

What Solution Should You Deliver? 249

Chapter 16 On Psychologists, Unicorns, and Clouds 251

A Cloudy History 252

This Time It’s Different 254

What Does It Cost? 255

What Are the Risks? 256

What Problems Can Cloud Solve Well? 257

What Services Is Cloud Good at Providing? 258

Storage 258

Content Distribution 259

Database Services 260

Application Services 260

Network Services 260

Deploying Cloud 261

How Hard Is Undoing the Deployment? 261

How Will the Service Connect to My Network? 261

How Does Security Work? 262

Systemic Interactions 262

Flying Through the Cloud 262

Components 263

Looking Back Over the Clouds 264

Chapter 17 Software-Defined Networks 265

Understanding SDNs 265

A Proposed Definition 265

A Proposed Framework 266

 The Distributed Model 267

 The Augmented Model 268

 The Hybrid Model 269

 The Replace Model 271

 Offline Routing/Online Reaction 272

 OpenFlow 274

 Objections and Considerations 276

Conclusion 281

Software-Defined Network Use Cases 281

SDNs in a Data Center 281

 What OpenFlow Brings to the Table 281

 Challenges to the OpenFlow Solution 283

SDNs in a Wide-Area Core 283

Final Thoughts on SDNs 285

Chapter 18 Data Center Design 287

Data Center Spine and Leaf Fabrics 287

Understanding Spine and Leaf 288

The Border Leaf 291

Sizing a Spine and Leaf Fabric 291

 Speed of the Fabric 291

 Number of Edge Ports 292

 Total Fabric Bandwidth 293

Why No Oversubscription? 294

The Control Plane Conundrum 295

Why Not Layer 2 Alone? 295

Where Should Layer 3 Go? 296

 Software-Defined Networks as a Potential Solution 298

Network Virtualization in the Data Center 299

Thoughts on Storage 299

Modularity and the Data Center 300

Summary 301


9781587143755   TOC   3/12/2014



Russ White, CCIE No. 2635, is a principal engineer in the IPOS team at Ericsson. He has worked in routing protocols and routed network design for the past 15 years. Russ has spoken at Cisco Live, Interop, LACNOG, and other global industry venues. He is actively involved in the IETF and the ISOC, has co-authored more than 30 software patents in the area of network protocols, and has co-authored nine books in the area of network protocols, design, and architecture. He holds a Master of Information Technology in Network Design and Architecture from Capella University and a Master of Christian Ministry in Christian literature from Shepherds Theological Seminary.


Denise Donohue, CCIE No. 9566 (Routing and Switching), is a senior solutions architect with Chesapeake NetCraftsmen. Denise has worked with computer systems since the mid-1990s, focusing on network design since 2004. During that time she has designed for a wide range of networks, private and public, of all sizes, across most industries. Denise has also authored or co-authored many Cisco Press books covering data and voice networking technologies and spoken at Cisco Live and other industry events.