Question 1: Create a post which compares and contrasts SaaS, PaaS, and IaaS, and provide an example of each.
Question 2:
– Respond to at least two peers’ posts. Responses should be substantiative and clear and further the conversation by stating what you learned from the post and asking questions. Minimum is 150 words per response.
Required Reading:
1. Jamsa – Chapter 1
2. Erl – Chapter 3 (Section 3.1 Only)
3. Jamsa – Chapter 2
4. Erl – Chapter 4 (Sections 4.1 and 4.2 Only)
References:
Erl, T., Mahmood, Z., & Puttini, R. (2014). Cloud computing: concepts, technology, & architecture. Upper Saddle River, NJ: Prentice Hall.
Jamsa, K. A. (2013). Cloud computing: SaaS, PaaS, IaaS, virtualization, business models, mobile, security and more. Burlington, MA: Jones & Bartlett Learning.
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2
Cloud Computing
Concepts, Technology & Architecture
Thomas Erl,
Zaigham Mahmood,
and Ricardo Puttini
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Praise for this Book
“Cloud computing, more than most disciplines in IT, suffers from too much talk and not enough
practice. Thomas Erl has written a timely book that condenses the theory and buttresses it with realworld examples that demystify this important technology. An important guidebook for your journey
into the cloud.”
—Scott Morrison, Chief Technology Officer, Layer 7 Technologies
“An excellent, extremely well-written, lucid book that provides a comprehensive picture of cloud
computing, covering multiple dimensions of the subject. The case studies presented in the book
provide a real-world, practical perspective on leveraging cloud computing in an organization. The
book covers a wide range of topics, from technology aspects to the business value provided by cloud
computing. This is the best, most comprehensive book on the subject—a must-read for any cloud
computing practitioner or anyone who wants to get an in-depth picture of cloud computing concepts
and practical implementation.”
—Suzanne D’Souza, SOA/BPM Practice Lead, KBACE Technologies
“This book offers a thorough and detailed description of cloud computing concepts, architectures,
and technologies. It serves as a great reference for both newcomers and experts and is a must-read for
any IT professional interested in cloud computing.”
—Andre Tost, Senior Technical Staff Member, IBM Software Group
“This is a great book on the topic of cloud computing. It is impressive how the content spans from
taxonomy, technology, and architectural concepts to important business considerations for cloud
adoption. It really does provide a holistic view to this technology paradigm.”
—Kapil Bakshi, Architecture and Strategy, Cisco Systems Inc.
“I have read every book written by Thomas Erl and Cloud Computing is another excellent publication
and demonstration of Thomas Erl’s rare ability to take the most complex topics and provide critical
core concepts and technical information in a logical and understandable way.”
—Melanie A. Allison, Principal, Healthcare Technology Practice, Integrated Consulting Services
“Companies looking to migrate applications or infrastructure to the cloud are often misled by
buzzwords and industry hype. This work cuts through the hype and provides a detailed look, from
investigation to contract to implementation to termination, at what it takes for an organization to
engage with cloud service providers. This book really lays out the benefits and struggles with getting
a company to an IaaS, PaaS, or SaaS solution.”
—Kevin Davis, Ph.D., Solutions Architect
7
“Thomas, in his own distinct and erudite style, provides a comprehensive and a definitive book on
cloud computing. Just like his previous masterpiece, Service-Oriented Architecture: Concepts,
Technology, and Design, this book is sure to engage CxOs, cloud architects, and the developer
community involved in delivering software assets on the cloud. Thomas and his authoring team have
taken great pains in providing great clarity and detail in documenting cloud architectures, cloud
delivery models, cloud governance, and economics of cloud, without forgetting to explain the core of
cloud computing that revolves around Internet architecture and virtualization. As a reviewer for this
outstanding book, I must admit I have learned quite a lot while reviewing the material. A ‘must have’
book that should adorn everybody’s desk!”
—Vijay Srinivasan, Chief Architect – Technology, Cognizant Technology Solutions
“This book provides comprehensive and descriptive vendor-neutral coverage of cloud computing
technology, from both technical and business aspects. It provides a deep-down analysis of cloud
architectures and mechanisms that capture the real-world moving parts of cloud platforms. Business
aspects are elaborated on to give readers a broader perspective on choosing and defining basic cloud
computing business models. Thomas Erl’s Cloud Computing: Concepts, Technology & Architecture is an
excellent source of knowledge of fundamental and in-depth coverage of cloud computing.”
—Masykur Marhendra Sukmanegara, Communication Media & Technology, Consulting Workforce
Accenture
“The richness and depth of the topics discussed are incredibly impressive. The depth and breadth of
the subject matter are such that a reader could become an expert in a short amount of time.”
—Jamie Ryan, Solutions Architect, Layer 7 Technologies
“Demystification, rationalization, and structuring of implementation approaches have always been
strong parts in each and every one of Thomas Erl’s books. This book is no exception. It provides the
definitive, essential coverage of cloud computing and, most importantly, presents this content in a
very comprehensive manner. Best of all, this book follows the conventions of the previous service
technology series titles, making it read like a natural extension of the library. I strongly believe that
this will be another bestseller from one of the top-selling IT authors of the past decade.”
—Sergey Popov, Senior Enterprise Architect SOA/Security, Liberty Global International
“A must-read for anyone involved in cloud design and decision making! This insightful book
provides in-depth, objective, vendor-neutral coverage of cloud computing concepts, architecture
models, and technologies. It will prove very valuable to anyone who needs to gain a solid
understanding of how cloud environments work and how to design and migrate solutions to clouds.”
—Gijs in ’t Veld, Chief Architect, Motion10
“A reference book covering a wide range of aspects related to cloud providers and cloud consumers. If
you would like to provide or consume a cloud service and need to know how, this is your book. The
8
book has a clear structure to facilitate a good understanding of the various concepts of cloud.”
—Roger Stoffers, Solution Architect
“Cloud computing has been around for a few years, yet there is still a lot of confusion around the
term and what it can bring to developers and deployers alike. This book is a great way of finding out
what’s behind the cloud, and not in an abstract or high-level manner: It dives into all of the details
that you’d need to know in order to plan for developing applications on cloud and what to look for
when using applications or services hosted on a cloud. There are very few books that manage to
capture this level of detail about the evolving cloud paradigm as this one does. It’s a must for
architects and developers alike.”
—Dr. Mark Little, Vice President, Red Hat
“This book provides a comprehensive exploration of the concepts and mechanics behind clouds. It’s
written for anyone interested in delving into the details of how cloud environments function, how
they are architected, and how they can impact business. This is the book for any organization
seriously considering adopting cloud computing. It will pave the way to establishing your cloud
computing roadmap.”
—Damian Maschek, SOA Architect, Deutsche Bahn
“One of the best books on cloud computing I have ever read. It is complete yet vendor technology
neutral and successfully explains the major concepts in a well-structured and disciplined way. It goes
through all the definitions and provides many hints for organizations or professionals who are
approaching and/or assessing cloud solutions. This book gives a complete list of topics playing
fundamental roles in the cloud computing discipline. It goes through a full list of definitions very
clearly stated. Diagrams are simple to understand and self-contained. Readers with different skill sets,
expertise, and backgrounds will be able to understand the concepts seamlessly.”
—Antonio Bruno, Infrastructure and Estate Manager, UBS AG
“Cloud Computing: Concepts, Technology & Architecture is a comprehensive book that focuses on what
cloud computing is really all about…. This book will become the foundation on which many
organizations will build successful cloud adoption projects. It is a must-read reference for both IT
infrastructure and application architects interested in cloud computing or involved in cloud adoption
projects. It contains extremely useful and comprehensive information for those who need to build
cloud-based architectures or need to explain it to customers thinking about adopting cloud
computing technology in their organization.”
—Johan Kumps, SOA Architect, RealDolmen
“This book defines the basic terminology and patterns for the topic—a useful reference for the cloud
practitioner. Concepts from multitenancy to hypervisor are presented in a succinct and clear manner.
The underlying case studies provide wonderful real-worldness.”
9
—Dr. Thomas Rischbeck, Principal Architect, ipt
“The book provides a good foundation to cloud services and issues in cloud service design. Chapters
highlight key issues that need to be considered in learning how to think in cloud technology terms;
this is highly important in today’s business and technology environments where cloud computing
plays a central role in connecting user services with virtualized resources and applications.”
—Mark Skilton, Director, Office of Strategy and Technology, Global Infrastructure Services, Capgemini
“The book is well organized and covers basic concepts, technologies, and business models about cloud
computing. It defines and explains a comprehensive list of terminologies and glossaries about cloud
computing so cloud computing experts can speak and communicate with the same set of standardized
language. The book is easy to understand and consistent with early published books from Thomas
Erl…. It is a must-read for both beginners and experienced professionals.”
—Jian “Jeff” Zhong, Chief Technology Officer (Acting) and Chief Architect for SOA and Cloud
Computing, Futrend Technology Inc.
“Students of the related specialties can fulfill their educational process with very easily understood
materials that are broadly illustrated and clearly described. Professors of different disciplines, from
business analysis to IT implementation—even legal and financial monitoring—can use the book as an
on-table lecturing manual. IT specialists of all ranks and fields of application will find the book as a
practical and useful support for sketching solutions unbound to any particular vendor or brand.”
—Alexander Gromoff, Director of Science & Education, Center of Information Control Technologies,
Chairman of BPM Chair in Business Informatics Department, National Research University “Higher
School of Economics”
“Cloud Computing: Concepts, Technology & Architecture is a comprehensive compendium of all the
relevant information about the transformative cloud technology. Erl’s latest title concisely and clearly
illustrates the origins and positioning of the cloud paradigm as the next-generation computing
model. All the chapters are carefully written and arranged in an easy-to-understand manner. This
book will be immeasurably beneficial for business and IT professionals. It is set to shake up and help
organize the world of cloud computing.”
—Pethuru Raj, Ph.D., Enterprise Architecture Consultant, Wipro
“A cloud computing book that will stand out and survive the test of time, even in one of the fastest
evolving areas of technology. This book does a great job breaking down the high level of complexity
of cloud computing into easy-to-understand pieces. It goes beyond the basic, often repeated,
explanations. It examines the fundamental concepts and the components, as well as the mechanisms
and architectures that make up cloud computing environments. The approach gradually builds the
reader’s understanding from the ground up.
“In a rapidly evolving area like cloud computing, it’s easy to focus on details and miss the big picture.
10
The focus on concepts and architectural models instead of vendor-specific details allows readers to
quickly gain essential knowledge of complex topics. The concepts come together in the last part of
the book, which should be required reading for any decision maker evaluating when and how to start
a transition to cloud computing. Its thorough, comprehensive coverage of fundamentals and
advanced topics makes the book a valuable resource to keep on your desk or your eBook reader,
regardless if you’re new to the topic or you already have cloud experience.
“I highly recommend the book to those looking to implement or evaluate cloud environments, or
simply looking to educate themselves in a field that will shape IT over the next decade.”
—Christoph Schittko, Principal Technology Strategist & Cloud Solution Director, Microsoft
“Cloud Computing: Concepts, Technology & Architecture is an excellent resource for IT professionals and
managers who want to learn and understand cloud computing, and who need to select or build cloud
systems and solutions. It lays the foundation for cloud concepts, models, technologies, and
mechanisms. As the book is vendor-neutral, it will remain valid for many years. We will recommend
this book to Oracle customers, partners, and users for their journey toward cloud computing. This
book has the potential to become the basis for a cloud computing manifesto, comparable to what was
accomplished with the SOA manifesto.”
—Jürgen Kress, Fusion Middleware Partner Adoption, Oracle EMEA
11
To my family and friends
—Thomas Erl
To Zoya, Hanya, and Ozair with love
—Zaigham Mahmood
To Silvia, Luiza, Isadora, and Lucas
—Ricardo Puttini
Current Printing: 2019
12
Contents at a Glance
Foreword
CHAPTER 1: Introduction
CHAPTER 2: Case Study Background
PART I: FUNDAMENTAL CLOUD COMPUTING
CHAPTER 3: Understanding Cloud Computing
CHAPTER 4: Fundamental Concepts and Models
CHAPTER 5: Cloud-Enabling Technology
CHAPTER 6: Fundamental Cloud Security
PART II: CLOUD COMPUTING MECHANISMS
CHAPTER 7: Cloud Infrastructure Mechanisms
CHAPTER 8: Specialized Cloud Mechanisms
CHAPTER 9: Cloud Management Mechanisms
CHAPTER 10: Cloud Security Mechanisms
PART III: CLOUD COMPUTING ARCHITECTURE
CHAPTER 11: Fundamental Cloud Architectures
CHAPTER 12: Advanced Cloud Architectures
CHAPTER 13: Specialized Cloud Architectures
PART IV: WORKING WITH CLOUDS
CHAPTER 14: Cloud Delivery Model Considerations
CHAPTER 15: Cost Metrics and Pricing Models
CHAPTER 16: Service Quality Metrics and SLAs
PART V: APPENDICES
APPENDIX A: Case Study Conclusions
APPENDIX B: Industry Standards Organizations
13
APPENDIX C: Mapping Mechanisms to Characteristics
APPENDIX D: Data Center Facilities (TIA-942)
APPENDIX E: Cloud-Adapted Risk Management Framework
APPENDIX F: Cloud Provisioning Contracts
APPENDIX G: Cloud Business Case Template
About the Authors
About the Contributors
Index
14
Contents
Foreword
Acknowledgments
CHAPTER 1: Introduction
1.1 Objectives of This Book
1.2 What This Book Does Not Cover
1.3 Who This Book Is For
1.4 How This Book Is Organized
Part I: Fundamental Cloud Computing
Chapter 3: Understanding Cloud Computing
Chapter 4: Fundamental Concepts and Models
Chapter 5: Cloud-Enabling Technology
Chapter 6: Fundamental Cloud Security
Part II: Cloud Computing Mechanisms
Chapter 7: Cloud Infrastructure Mechanisms
Chapter 8: Specialized Cloud Mechanisms
Chapter 9: Cloud Management Mechanisms
Chapter 10: Cloud Security Mechanisms
Part III: Cloud Computing Architecture
Chapter 11: Fundamental Cloud Architectures
Chapter 12: Advanced Cloud Architectures
Chapter 13: Specialized Cloud Architectures
Part IV: Working with Clouds
Chapter 14: Cloud Delivery Model Considerations
Chapter 15: Cost Metrics and Pricing Models
Chapter 16: Service Quality Metrics and SLAs
Part V: Appendices
Appendix A: Case Study Conclusions
Appendix B: Industry Standards Organizations
Appendix C: Mapping Mechanisms to Characteristics
Appendix D: Data Center Facilities (TIA-942)
Appendix E: Emerging Technologies
15
Appendix F: Cloud Provisioning Contracts
Appendix G: Cloud Business Case Template
1.5 Conventions
Symbols and Figures
Summary of Key Points
1.6 Additional Information
Updates, Errata, and Resources
Visio Stencil and Symbol Legend
Patterns, Mechanisms and Metrics
Social Media
Cloud Certified Professional (CCP) Program
CHAPTER 2: Case Study Background
2.1 Case Study #1: ATN
Technical Infrastructure and Environment
Business Goals and New Strategy
Roadmap and Implementation Strategy
2.2 Case Study #2: DTGOV
Technical Infrastructure and Environment
Business Goals and New Strategy
Roadmap and Implementation Strategy
2.3 Case Study #3: Innovartus Technologies Inc.
Technical Infrastructure and Environment
Business Goals and Strategy
Roadmap and Implementation Strategy
PART I: FUNDAMENTAL CLOUD COMPUTING
CHAPTER 3: Understanding Cloud Computing
3.1 Origins and Influences
A Brief History
Definitions
Business Drivers
Capacity Planning
Cost Reduction
16
Organizational Agility
Technology Innovations
Clustering
Grid Computing
Virtualization
Technology Innovations vs. Enabling Technologies
3.2 Basic Concepts and Terminology
Cloud
IT Resource
On-Premise
Cloud Consumers and Cloud Providers
Scaling
Horizontal Scaling
Vertical Scaling
Cloud Service
Cloud Service Consumer
3.3 Goals and Benefits
Reduced Investments and Proportional Costs
Increased Scalability
Increased Availability and Reliability
3.4 Risks and Challenges
Increased Security Vulnerabilities
Reduced Operational Governance Control
Limited Portability Between Cloud Providers
Multi-Regional Compliance and Legal Issues
CHAPTER 4: Fundamental Concepts and Models
4.1 Roles and Boundaries
Cloud Provider
Cloud Consumer
Cloud Service Owner
Cloud Resource Administrator
Additional Roles
Organizational Boundary
17
Trust Boundary
4.2 Cloud Characteristics
On-Demand Usage
Ubiquitous Access
Multitenancy (and Resource Pooling)
Elasticity
Measured Usage
Resiliency
4.3 Cloud Delivery Models
Infrastructure-as-a-Service (IaaS)
Platform-as-a-Service (PaaS)
Software-as-a-Service (SaaS)
Comparing Cloud Delivery Models
Combining Cloud Delivery Models
IaaS + PaaS
IaaS + PaaS + SaaS
4.4 Cloud Deployment Models
Public Clouds
Community Clouds
Private Clouds
Hybrid Clouds
Other Cloud Deployment Models
CHAPTER 5: Cloud-Enabling Technology
5.1 Broadband Networks and Internet Architecture
Internet Service Providers (ISPs)
Connectionless Packet Switching (Datagram Networks)
Router-Based Interconnectivity
Physical Network
Transport Layer Protocol
Application Layer Protocol
Technical and Business Considerations
Connectivity Issues
Network Bandwidth and Latency Issues
18
Cloud Carrier and Cloud Provider Selection
5.2 Data Center Technology
Virtualization
Standardization and Modularity
Automation
Remote Operation and Management
High Availability
Security-Aware Design, Operation, and Management
Facilities
Computing Hardware
Storage Hardware
Network Hardware
Carrier and External Networks Interconnection
Web-Tier Load Balancing and Acceleration
LAN Fabric
SAN Fabric
NAS Gateways
Other Considerations
5.3 Virtualization Technology
Hardware Independence
Server Consolidation
Resource Replication
Operating System-Based Virtualization
Hardware-Based Virtualization
Virtualization Management
Other Considerations
5.4 Web Technology
Basic Web Technology
Web Applications
5.5 Multitenant Technology
5.6 Containerization
Containerization vs. Virtualization
Benefits of Containers
19
Container Hosting and Pods
Fundamental Container Architecture Elements
Container Engine
Container Build File
Container Image
Container
Networking Address
Storage Device
5.7 Case Study Example
CHAPTER 6: Fundamental Cloud Security
6.1 Basic Terms and Concepts
Confidentiality
Integrity
Authenticity
Availability
Threat
Vulnerability
Risk
Security Controls
Security Mechanisms
Security Policies
6.2 Threat Agents
Anonymous Attacker
Malicious Service Agent
Trusted Attacker
Malicious Insider
6.3 Cloud Security Threats
Traffic Eavesdropping
Malicious Intermediary
Denial of Service
Insufficient Authorization
Virtualization Attack
Overlapping Trust Boundaries
20
Container Attack
6.4 Additional Considerations
Flawed Implementations
Security Policy Disparity
Contracts
Risk Management
6.5 Case Study Example
PART II: CLOUD COMPUTING MECHANISMS
CHAPTER 7: Cloud Infrastructure Mechanisms
7.1 Logical Network Perimeter
Case Study Example
7.2 Virtual Server
Case Study Example
7.3 Cloud Storage Device
Cloud Storage Levels
Network Storage Interfaces
Object Storage Interfaces
Database Storage Interfaces
Relational Data Storage
Non-Relational Data Storage
Case Study Example
7.4 Cloud Usage Monitor
Monitoring Agent
Resource Agent
Polling Agent
Case Study Example
7.5 Resource Replication
Case Study Example
7.6 Ready-Made Environment
Case Study Example
7.7 Container
CHAPTER 8: Specialized Cloud Mechanisms
21
8.1 Automated Scaling Listener
Case Study Example
8.2 Load Balancer
Case Study Example
8.3 SLA Monitor
Case Study Example
SLA Monitor Polling Agent
SLA Monitoring Agent
8.4 Pay-Per-Use Monitor
Case Study Example
8.5 Audit Monitor
Case Study Example
8.6 Failover System
Active-Active
Active-Passive
Case Study Example
8.7 Hypervisor
Case Study Example
8.8 Resource Cluster
Case Study Example
8.9 Multi-Device Broker
Case Study Example
8.10 State Management Database
Case Study Example
CHAPTER 9: Cloud Management Mechanisms
9.1 Remote Administration System
Case Study Example
9.2 Resource Management System
Case Study Example
9.3 SLA Management System
Case Study Example
9.4 Billing Management System
Case Study Example
22
CHAPTER 10: Cloud Security Mechanisms
10.1 Encryption
Symmetric Encryption
Asymmetric Encryption
Case Study Example
10.2 Hashing
Case Study Example
10.3 Digital Signature
Case Study Example
10.4 Public Key Infrastructure (PKI)
Case Study Example
10.5 Identity and Access Management (IAM)
Case Study Example
10.6 Single Sign-On (SSO)
Case Study Example
10.7 Cloud-Based Security Groups
Case Study Example
10.8 Hardened Virtual Server Images
Case Study Example
PART III: CLOUD COMPUTING ARCHITECTURE
CHAPTER 11: Fundamental Cloud Architectures
11.1 Workload Distribution Architecture
11.2 Resource Pooling Architecture
11.3 Dynamic Scalability Architecture
11.4 Elastic Resource Capacity Architecture
11.5 Service Load Balancing Architecture
11.6 Cloud Bursting Architecture
11.7 Elastic Disk Provisioning Architecture
11.8 Redundant Storage Architecture
11.9 Case Study Example
CHAPTER 12: Advanced Cloud Architectures
12.1 Hypervisor Clustering Architecture
23
12.2 Load Balanced Virtual Server Instances Architecture
12.3 Non-Disruptive Service Relocation Architecture
12.4 Zero Downtime Architecture
12.5 Cloud Balancing Architecture
12.6 Resource Reservation Architecture
12.7 Dynamic Failure Detection and Recovery Architecture
12.8 Bare-Metal Provisioning Architecture
12.9 Rapid Provisioning Architecture
12.10 Storage Workload Management Architecture
12.11 Case Study Example
CHAPTER 13: Specialized Cloud Architectures
13.1 Direct I/O Access Architecture
13.2 Direct LUN Access Architecture
13.3 Dynamic Data Normalization Architecture
13.4 Elastic Network Capacity Architecture
13.5 Cross-Storage Device Vertical Tiering Architecture
13.6 Intra-Storage Device Vertical Data Tiering Architecture
13.7 Load Balanced Virtual Switches Architecture
13.8 Multipath Resource Access Architecture
13.9 Persistent Virtual Network Configuration Architecture
13.10 Redundant Physical Connection for Virtual Servers Architecture
13.11 Storage Maintenance Window Architecture
PART IV: WORKING WITH CLOUDS
CHAPTER 14: Cloud Delivery Model Considerations
14.1 Cloud Delivery Models: The Cloud Provider Perspective
Building IaaS Environments
Data Centers
Scalability and Reliability
Monitoring
Security
Equipping PaaS Environments
Scalability and Reliability
24
Monitoring
Security
Optimizing SaaS Environments
Security
14.2 Cloud Delivery Models: The Cloud Consumer Perspective
Working with IaaS Environments
IT Resource Provisioning Considerations
Working with PaaS Environments
IT Resource Provisioning Considerations
Working with SaaS Services
14.3 Case Study Example
CHAPTER 15: Cost Metrics and Pricing Models
15.1 Business Cost Metrics
Up-Front and On-Going Costs
Additional Costs
Case Study Example
Product Catalog Browser
On-Premise Up-Front Costs
On-Premise On-Going Costs
Cloud-Based Up-Front Costs
Cloud-Based On-Going Costs
Client Database
On-Premise Up-Front Costs
On-Premise On-Going Costs
Cloud-Based Up-Front Costs
Cloud-Based On-Going Costs
15.2 Cloud Usage Cost Metrics
Network Usage
Inbound Network Usage Metric
Outbound Network Usage Metric
Intra-Cloud WAN Usage Metric
Server Usage
On-Demand Virtual Machine Instance Allocation Metric
25
Reserved Virtual Machine Instance Allocation Metric
Cloud Storage Device Usage
On-Demand Storage Space Allocation Metric
I/O Data Transferred Metric
Cloud Service Usage
Application Subscription Duration Metric
Number of Nominated Users Metric
Number of Transactions Users Metric
15.3 Cost Management Considerations
Pricing Models
Additional Considerations
Case Study Example
Virtual Server On-Demand Instance Allocation
Virtual Server Reserved Instance Allocation
Cloud Storage Device
WAN Traffic
CHAPTER 16: Service Quality Metrics and SLAs
16.1 Service Quality Metrics
Service Availability Metrics
Availability Rate Metric
Outage Duration Metric
Service Reliability Metrics
Mean-Time Between Failures (MTBF) Metric
Reliability Rate Metric
Service Performance Metrics
Network Capacity Metric
Storage Device Capacity Metric
Server Capacity Metric
Web Application Capacity Metric
Instance Starting Time Metric
Response Time Metric
Completion Time Metric
Service Scalability Metrics
26
Storage Scalability (Horizontal) Metric
Server Scalability (Horizontal) Metric
Server Scalability (Vertical) Metric
Service Resiliency Metrics
Mean-Time to Switchover (MTSO) Metric
Mean-Time System Recovery (MTSR) Metric
16.2 Case Study Example
16.3 SLA Guidelines
16.4 Case Study Example
Scope and Applicability
Service Quality Guarantees
Definitions
Usage of Financial Credits
SLA Exclusions
PART V: APPENDICES
Appendix A: Case Study Conclusions
A.1 ATN
A.2 DTGOV
A.3 Innovartus
Appendix B: Industry Standards Organizations
B.1 National Institute of Standards and Technology (NIST)
B.2 Cloud Security Alliance (CSA)
B.3 Distributed Management Task Force (DMTF)
B.4 Storage Networking Industry Association (SNIA)
B.5 Organization for the Advancement of Structured Information Standards (OASIS)
B.6 The Open Group
B.7 Open Cloud Consortium (OCC)
B.8 European Telecommunications Standards Institute (ETSI)
B.9 Telecommunications Industry Association (TIA)
B.10 Liberty Alliance
B.11 Open Grid Forum (OGF)
27
Appendix C: Mapping Mechanisms to Characteristics
Appendix D: Data Center Facilities (TIA-942)
D.1 Primary Rooms
Electrical Room
Mechanical Room
Storage and Staging
Offices, Operations Center, and Support
Telecommunications Entrance
Computer Room
D.2 Environmental Controls
External Electrical Power Provider Interconnection
Power Distribution
Uninterruptible Power Source (UPS)
Power Engine-Generator
D.3 Infrastructure Redundancy Summary
Appendix E: Cloud-Adapted Risk Management Framework
E.1 Security Conservation Principle
E.2 The Risk Management Framework
Appendix F: Cloud Provisioning Contracts
F.1 Cloud Provisioning Contract Structure
Terms of Service
Service Usage Policy
Security and Privacy Policy
Warranties and Liabilities
Rights and Responsibilities
Termination and Renewal
Specifications and SLAs
Pricing and Billing
Other Issues
Legal and Compliance Issues
Auditability and Accountability
Changes in the Contract Terms and Conditions
28
F.2 Cloud Provider Selection Guidelines
Cloud Provider Viability
Appendix G: Cloud Business Case Template
G.1 Business Case Identification
G.2 Business Needs
G.3 Target Cloud Environment
G.4 Technical Issues
G.5 Economic Factors
About the Authors
Thomas Erl
Zaigham Mahmood
Ricardo Puttini
About the Contributors
Pamela J. Wise-Martinez, MSc
Gustavo Azzolin, BSc, MSc
Dr. Michaela Iorga, Ph.D.
Amin Naserpour
Vinícius Pacheco, MSc
Matthias Ziegler
Index
29
Foreword by Pamela J. Wise-Martinez
The idea of cloud computing isn’t new, or overly complicated from a technology resources and
internetworking perspective. What’s new is the growth and maturity of cloud computing methods, and
strategies that enable the goals of business agility.
Looking back, the phrase “utility computing” didn’t captivate or create the stir in the information industry as
the term “cloud computing” has in recent years. Nevertheless, appreciation of readily available resources has
arrived and the utilitarian or servicing features are what are at the heart of outsourcing the access of information
technology resources and services. In this light, cloud computing represents a flexible, cost-effective, and
proven delivery platform for business and consumer information services over the Internet. Cloud computing
has become an industry game changer as businesses and information technology leaders realize the potential in
combining and sharing computing resources as opposed to building and maintaining them.
There’s seemingly no shortage of views regarding the benefits of cloud computing nor is there a shortage of
vendors willing to offer services in either open source or promising commercial solutions. Beyond the hype,
there are many aspects of the cloud that have earned new consideration due to their increased service
capability and potential efficiencies. The ability to demonstrate transforming results in cloud computing to
resolve traditional business problems using information technology management best practices now exists. In
the case of economic impacts, the principle of pay-as-you-go and computer agnostic services are concepts ready
for prime time. We can measure performance as well as calculate the economic and environmental effects of
cloud computing today.
The architectural change from client-server to service orientation led to an evolution of composable and
reusable code; though the practice had been around for many years, it is now the de facto approach used to
lower cost and identify best practices and patterns for increasing business agility. This has advanced the
computer software industry’s design methods, components, and engineering. Comparatively, the wide
acceptance and adoption of cloud computing is revolutionizing information and technology resource
management. We now have the ability to outsource hardware and software capabilities on a large-scale to
fulfill end-to-end business automation requirements. Marks and Lozano understood this emergence and the
need for better software design: “…we now have the ability to collect, transport, process, store, and access data nearly
anywhere in nearly arbitrary volume.” The limitations depend largely on how “cloudy” or cloud-aware the
service/component is, and hence the need for better software architecture. (Eric A. Marks and Roberto
Lozano [Executive Guide to Cloud Computing]).
The reusable evolution through service architecture reinforces a focus on business objectives as opposed to the
number of computing platforms to support. As a viable resource management alternative, cloud computing is
fundamentally changing the way we think about computing solutions in retail, education, and public sectors.
The use of cloud computing architecture and standards are driving unique ways in which computing solutions
are delivered, as well as platform diversity to meet bottom-line business objectives.
Thomas Erl’s body of work on service technology guided the technology industry through eloquent
illustrations and literature over the past decade. Thomas’ brilliant efforts on principles, concepts, patterns, and
30
expressions gave the information technology community an evolved software architecture approach that now
forms a foundation for cloud computing goals to be successfully fulfilled in practice. This is a key assertion, as
cloud computing is no longer a far-reaching concept of the future, but rather a dominant information
technology service option and resource delivery presence.
Thomas’ Cloud Computing: Concepts, Technology & Architecture takes the industry beyond the definitions of
cloud computing and juxtaposes virtualization, grid, and sustainment strategies as contrasted in day to day
operations. Thomas and his team of authors take the reader from beginning to end with the essential elements
of cloud computing, its history, innovation, and demand. Through case studies and architectural models they
articulate service requirements, infrastructure, security, and outsourcing of salient computing resources.
Thomas again enlightens the industry with poignant analysis and reliable architecture-driven practices and
principles. No matter the level of interest or experience, the reader will find clear value in this in-depth,
vendor-neutral study of cloud computing.
Pamela J. Wise-Martinez,
Inventor and Chief Architect
Department of Energy, National Nuclear Security Administration
(Disclaimer: The views expressed are the personal views of the author and are not intended to reflect either the views
of the U.S. Government, the U.S. Department of Energy, or the National Nuclear Security Administration.)
31
Acknowledgments
In alphabetical order by last name:
• Ahmed Aamer, AlFaisaliah Group
• Randy Adkins, Modus21
• Melanie Allison, Integrated Consulting Services
• Gabriela Inacio Alves, University of Brasilia
• Marcelo Ancelmo, IBM Rational Software Services
• Kapil Bakshi, Cisco Systems
• Toufic Boubez, Metafor Software
• Antonio Bruno, UBS AG
• Dr. Paul Buhler, Modus21
• Pethuru Raj Cheliah, Wipro
• Kevin Davis, Ph.D.
• Suzanne D’Souza, KBACE Technologies
• Yili Gong, Wuhan University
• Alexander Gromoff, Center of Information Control Technologies
• Chris Haddad, WSO2
• Richard Hill, University of Derby
• Michaela Iorga, Ph.D.
• Johan Kumps, RealDolmen
• Gijs in ’t Veld, Motion10
• Masykur Marhendra, Consulting Workforce Accenture
• Damian Maschek, Deutshe Bahn
• Claynor Mazzarolo, IBTI
• Charlie Mead, W3C
• Steve Millidge, C2B2
• Jorge Minguez, Thales Deutschland
• Scott Morrison, Layer 7
• Amin Naserpour, HP
• Vicente Navarro, European Space Agency
• Laura Olson, IBM WebSphere
• Tony Pallas, Intel
• Cesare Pautasso, University of Lugano
32
• Sergey Popov, Liberty Global International
• Olivier Poupeney, Dreamface Interactive
• Alex Rankov, EMC
• Dan Rosanova, West Monroe Partners
• Jaime Ryan, Layer 7
• Filippos Santas, Credit Suisse
• Christoph Schittko, Microsoft
• Guido Schmutz, Trivadis
• Mark Skilton, Capgemini
• Gary Smith, CloudComputingArchitect.com
• Kevin Spiess
• Vijay Srinivasan, Cognizant
• Daniel Starcevich, Raytheon
• Roger Stoffers, HP
• Andre Toffanello, IBTI
• Andre Tost, IBM Software Group
• Bernd Trops, talend
• Clemens Utschig, Boehringer Ingelheim Pharma
• Ignaz Wanders, Archimiddle
• Philip Wik, Redflex
• Jorge Williams, Rackspace
• Dr. Johannes Maria Zaha
• Jeff Zhong, Futrend Technologies
Special thanks to the CloudSchool.com research and development team that produced the CCP course
modules upon which this book is based.
33
Chapter 1. Introduction
1.1 Objectives of This Book
1.2 What This Book Does Not Cover
1.3 Who This Book Is For
1.4 How This Book Is Organized
1.5 Conventions
1.6 Additional Information
The past couple of decades saw the business-centric concept of outsourcing services and the technologycentric notion of utility computing evolve along relatively parallel streams. When they finally met to form a
technology landscape with a compelling business case and seismic impacts on the IT industry as a whole, it
became evident that what resultantly was termed and branded as “cloud computing” was more than just
another IT trend. It had become an opportunity to further align and advance the goals of the business with
the capabilities of technology.
Those who understand this opportunity can seize it to leverage proven and mature components of cloud
platforms to not only fulfill existing strategic business goals, but to even inspire businesses to set new
objectives and directions based on the extent to which cloud-driven innovation can further help optimize
business operations.
The first step to succeeding is education. Cloud computing adoption is not trivial. The cloud computing
marketplace is unregulated. And, not all products and technologies branded with “cloud” are, in fact,
sufficiently mature to realize or even supportive of realizing actual cloud computing benefits. To add to the
confusion, there are different definitions and interpretations of cloud-based models and frameworks floating
34
around IT literature and the IT media space, which leads to different IT professionals acquiring different
types of cloud computing expertise.
And then, of course, there is the fact that cloud computing is, at its essence, a form of service provisioning. As
with any type of service we intend to hire or outsource (IT-related or otherwise), it is commonly understood
that we will be confronted with a marketplace comprised of service providers of varying quality and reliability.
Some may offer attractive rates and terms, but may have unproven business histories or highly proprietary
environments. Others may have a solid business background, but may demand higher rates and less flexible
terms. Others yet, may simply be insincere or temporary business ventures that unexpectedly disappear or are
acquired within a short period of time.
Back to the importance of getting educated. There is no greater danger to a business than approaching cloud
computing adoption with ignorance. The magnitude of a failed adoption effort not only correspondingly
impacts IT departments, but can actually regress a business to a point where it finds itself steps behind from
where it was prior to the adoption—and, perhaps, even more steps behind competitors that have been
successful at achieving their goals in the meantime.
Cloud computing has much to offer but its roadmap is riddled with pitfalls, ambiguities, and mistruths. The
best way to navigate this landscape is to chart each part of the journey by making educated decisions about
how and to what extent your project should proceed. The scope of an adoption is equally important to its
approach, and both of these aspects need to be determined by business requirements. Not by a product
vendor, not by a cloud vendor, and not by self-proclaimed cloud experts. Your organization’s business goals
must be fulfilled in a concrete and measurable manner with each completed phase of the adoption. This
validates your scope, your approach, and the overall direction of the project. In other words, it keeps your
project aligned.
Gaining a vendor-neutral understanding of cloud computing from an industry perspective empowers you with
the clarity necessary to determine what is factually cloud-related and what is not, as well as what is relevant to
your business requirements and what is not. With this information you can establish criteria that will allow
you to filter out the parts of the cloud computing product and service provider marketplaces to focus on what
has the most potential to help you and your business to succeed. We developed this book to assist you with
this goal.
—Thomas Erl
1.1. Objectives of This Book
This book is the result of more than two years of research and analysis of the commercial cloud computing
industry, cloud computing vendor platforms, and further innovation and contributions made by cloud
computing industry standards organizations and practitioners. The purpose of this book is to break down
proven and mature cloud computing technologies and practices into a series of well-defined concepts, models,
and technology mechanisms and architectures. The resulting chapters establish concrete, academic coverage of
fundamental aspects of cloud computing concepts and technologies. The range of topics covered is
documented using vendor-neutral terms and descriptions, carefully defined to ensure full alignment with the
cloud computing industry as a whole.
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1.2. What This Book Does Not Cover
Due to the vendor-neutral basis of this book, it does not contain any significant coverage of cloud computing
vendor products, services, or technologies. This book is complementary to other titles that provide productspecific coverage and to vendor product literature itself. If you are new to the commercial cloud computing
landscape, you are encouraged to use this book as a starting point before proceeding to books and courses that
are proprietary to vendor product lines.
1.3. Who This Book Is For
This book is aimed at the following target audience:
• IT practitioners and professionals who require vendor-neutral coverage of cloud computing
technologies, concepts, mechanisms, and models
• IT managers and decision makers who seek clarity regarding the business and technological
implications of cloud computing
• professors and students and educational institutions that require well-researched and well-defined
academic coverage of fundamental cloud computing topics
• business managers who need to assess the potential economic gains and viability of adopting cloud
computing resources
• technology architects and developers who want to understand the different moving parts that comprise
contemporary cloud platforms
1.4. How This Book Is Organized
The book begins with Chapters 1 and 2 providing introductory content and background information for the
case studies. All subsequent chapters are organized into the following parts:
• Part I: Fundamental Cloud Computing
• Part II: Cloud Computing Mechanisms
• Part III: Cloud Computing Architecture
• Part IV: Working with Clouds
• Part V: Appendices
Part I: Fundamental Cloud Computing
The four chapters in this part cover introductory topics in preparation for all subsequent chapters. Note that
Chapters 3 and 4 do not contain case study content.
Chapter 3: Understanding Cloud Computing
Following a brief history of cloud computing and a discussion of business drivers and technology innovations,
basic terminology and concepts are introduced, along with descriptions of common benefits and challenges of
cloud computing adoption.
Chapter 4: Fundamental Concepts and Models
Cloud delivery and cloud deployment models are discussed in detail, following sections that establish common
36
cloud characteristics and roles and boundaries.
Chapter 5: Cloud-Enabling Technology
Contemporary technologies that realize modern-day cloud computing platforms and innovations are
discussed, including data centers, virtualization, containerization, and Web-based technologies.
Chapter 6: Fundamental Cloud Security
Security topics and concepts relevant and distinct to cloud computing are introduced, including descriptions
of common cloud security threats and attacks.
Part II: Cloud Computing Mechanisms
Technology mechanisms represent well-defined IT artifacts that are established within an IT industry and
commonly distinct to a certain computing model or platform. The technology-centric nature of cloud
computing requires the establishment of a formal level of mechanisms to be able to explore how solutions can
be assembled via different combinations of mechanism implementations.
This part formally documents 20 technology mechanisms that are used within cloud environments to enable
generic and specialized forms of functionality. Each mechanism description is accompanied by a case study
example that demonstrates its usage. The utilization of the mechanisms is further explored throughout the
technology architectures covered in Part III.
Chapter 7: Cloud Infrastructure Mechanisms
Technology mechanisms foundational to cloud platforms are covered, including Logical Network Perimeter,
Virtual Server, Cloud Storage Device, Cloud Usage Monitor, Resource Replication, Ready-Made
Environment and Container.
Chapter 8: Specialized Cloud Mechanisms
A range of specialized technology mechanisms is described, including Automated Scaling Listener, Load
Balancer, SLA Monitor, Pay-Per-Use Monitor, Audit Monitor, Failover System, Hypervisor, Resource
Cluster, Multi-Device Broker, and State Management Database.
Chapter 9: Cloud Management Mechanisms
Mechanisms that enable the hands-on administration and management of cloud-based IT resources are
explained, including Remote Administration System, Resource Management System, SLA Management
System, and Billing Management System.
Chapter 10: Cloud Security Mechanisms
Security mechanisms that can be used to counter and prevent the threats described in Chapter 6 are covered,
including Encryption, Hashing, Digital Signatures, Public Key Infrastructures (PKI), Identity and Access
Management (IAM) Systems, Single Sign-On (SSO), Cloud-Based Security Groups, and Hardened Virtual
Server Images.
Part III: Cloud Computing Architecture
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Technology architecture within the realm of cloud computing introduces requirements and considerations
that manifest themselves in broadly scoped architectural layers and numerous distinct architectural models.
This set of chapters builds upon the coverage of cloud computing mechanisms from Part II by formally
documenting 29 cloud-based technology architectures and scenarios in which different combinations of the
mechanisms are documented in relation to fundamental, advanced, and specialized cloud architectures.
Chapter 11: Fundamental Cloud Architectures
Fundamental cloud architectural models establish baseline functions and capabilities. The architectures
covered in this chapter are Workload Distribution, Resource Pooling, Dynamic Scalability, Elastic Resource
Capacity, Service Load Balancing, Cloud Bursting, Elastic Disk Provisioning, and Redundant Storage.
Chapter 12: Advanced Cloud Architectures
Advanced cloud architectural models establish sophisticated and complex environments, several of which
directly build upon fundamental models. The architectures covered in this chapter are Hypervisor Clustering,
Load Balanced Virtual Server Instances, Non-Disruptive Service Relocation, Zero Downtime, Cloud
Balancing, Resource Reservation, Dynamic Failure Detection and Recovery, Bare-Metal Provisioning, Rapid
Provisioning, and Storage Workload Management.
Chapter 13: Specialized Cloud Architectures
Specialized cloud architectural models address distinct functional areas. The architectures covered in this
chapter are Direct I/O Access, Direct LUN Access, Dynamic Data Normalization, Elastic Network Capacity,
Cross-Storage Device Vertical Tiering, Intra-Storage Device Vertical Data Tiering, Load-Balanced Virtual
Switches, Multipath Resource Access, Persistent Virtual Network Configuration, Redundant Physical
Connection for Virtual Servers, and Storage Maintenance Window. Note that this chapter does not contain a
case study example.
Part IV: Working with Clouds
Cloud computing technologies and environments can be adopted to varying extents. An organization can
migrate select IT resources to a cloud, while keeping all other IT resources on-premise—or it can form
significant dependencies on a cloud platform by migrating larger amounts of IT resources or even using the
cloud environment to create them.
For any organization, it is important to assess a potential adoption from a practical and business-centric
perspective in order to pinpoint the most common factors that pertain to financial investments, business
impact, and various legal considerations. This set of chapters explores these and other topics related to the
real-world considerations of working with cloud-based environments.
Chapter 14: Cloud Delivery Model Considerations
Cloud environments need to be built and evolved by cloud providers in response to cloud consumer
requirements. Cloud consumers can use clouds to create or migrate IT resources to, subsequent to their
assuming administrative responsibilities. This chapter provides a technical understanding of cloud delivery
models from both the provider and consumer perspectives, each of which offers revealing insights into the
38
inner workings and architectural layers of cloud environments.
Chapter 15: Cost Metrics and Pricing Models
Cost metrics for network, server, storage, and software usage are described, along with various formulas for
calculating integration and ownership costs related to cloud environments. The chapter concludes with a
discussion of cost management topics as they relate to common business terms used by cloud provider
vendors.
Chapter 16: Service Quality Metrics and SLAs
Service level agreements establish the guarantees and usage terms for cloud services and are often determined
by the business terms agreed upon by cloud consumers and cloud providers. This chapter provides detailed
insight into how cloud provider guarantees are expressed and structured via SLAs, along with metrics and
formulas for calculating common SLA values, such as availability, reliability, performance, scalability, and
resiliency.
Part V: Appendices
Appendix A: Case Study Conclusions
The individual storylines of the case studies are concluded and the results of each organization’s cloud
computing adoption efforts are summarized.
Appendix B: Industry Standards Organizations
This appendix describes industry standards organizations and efforts in support of the cloud computing
industry.
Appendix C: Mapping Mechanisms to Characteristics
A table is provided, mapping cloud characteristics to the cloud computing mechanisms that can help realize
the characteristics.
Appendix D: Data Center Facilities (TIA-942)
A brief overview and breakdown of common data center facilities in reference to the TIA-942
Telecommunications Infrastructure Standard for Data Centers.
Appendix E: Cloud-Adapted Risk Management Framework
An overview of the Cloud-Adapted Risk Management Framework (CRMF) that is part of the NIST Cloud
Computing Security Reference Architecture.
Appendix F: Cloud Provisioning Contracts
The actual agreements signed between cloud provider vendors and cloud consumer organizations are distinct
legal contracts that encompass a range of specific terms and considerations. This appendix highlights the
typical parts of a cloud provisioning contract, and provides further guidelines.
Appendix G: Cloud Business Case Template
39
This appendix provides a checklist of items that can be used as a starting point for assembling a business case
for the adoption of cloud computing.
1.5. Conventions
Symbols and Figures
This book contains a series of diagrams that are referred to as figures. The primary symbols used throughout
the figures are individually described in the symbol legend located on the inside of the book cover. Full-color,
high-resolution versions of all figures in this book can be viewed and downloaded at
www.servicetechbooks.com/cloud/figures and www.informit.com/title/9780133387520.
Summary of Key Points
For quick reference purposes, each of the sections within Chapters 3 through 6 in Part I, “Fundamental Cloud
Computing,” concludes with a Summary of Key Points sub-section that concisely highlights the primary
statements made within the section, in bullet list format.
1.6. Additional Information
These sections provide supplementary information and resources.
Updates, Errata, and Resources
Information about other series titles and various supporting resources can be found at
www.arcitura.com/books.
Visio Stencil and Symbol Legend
Visit www.arcitura.com/notation to download a symbol legend and a Visio stencil with many of the symbols
from the figures in this book.
Patterns, Mechanisms and Metrics
Access online content dedicated to technology mechanisms, design patterns and associated metrics and
concepts at patterns.arcitura.com. Also, join the Patterns, Mechanisms and Metrics LinkedIn Group for
regular updates.
Social Media
Connect with the Prentice Hall Service Technology Series from Thomas Erl via Facebook, Twitter and
LinkedIn. Visit www.arcitura.com/community for more information.
Cloud Certified Professional (CCP) Program
This text book is an official part of the Cloud Certified Professional (CCP) curriculum from Arcitura
Education. Learn more at www.arcitura.com/ccp.
40
Chapter 2. Case Study Background
2.1 Case Study #1: ATN
2.2 Case Study #2: DTGOV
2.3 Case Study #3: Innovartus Technologies Inc.
Case study examples provide scenarios in which organizations assess, use, and manage cloud computing
models and technologies. Three organizations from different industries are presented for analysis in this book,
each of which has distinctive business, technological, and architectural objectives that are introduced in this
chapter.
The organizations presented for case study are:
• Advanced Telecom Networks (ATN) – a global company that supplies network equipment to the
telecommunications industry
• DTGOV – a public organization that specializes in IT infrastructure and technology services for public
sector organizations
• Innovartus Technologies Inc. – a medium-sized company that develops virtual toys and educational
entertainment products for children
Most chapters after Part I include one or more Case Study Example sections. A conclusion to the storylines is
provided in Appendix A.
2.1. Case Study #1: ATN
ATN is a company that provides network equipment to telecommunications industries across the globe. Over
the years, ATN has grown considerably and their product portfolio has expanded to accommodate several
acquisitions, including companies that specialize in infrastructure components for Internet, GSM, and cellular
41
providers. ATN is now a leading supplier of a diverse range of telecommunications infrastructure.
In recent years, market pressure has been increasing. ATN has begun looking for ways to increase its
competitiveness and efficiency by taking advantage of new technologies, especially those that can assist in cost
reduction.
Technical Infrastructure and Environment
ATN’s various acquisitions have resulted in a highly complex and heterogeneous IT landscape. A cohesive
consolidation program was not applied to the IT environment after each acquisition round, resulting in similar
applications running concurrently and an increase in maintenance costs. In 2010, ATN merged with a major
European telecommunications supplier, adding another applications portfolio to its inventory. The IT
complexity snowballed into a serious obstruction and became a source of critical concern to ATN’s board of
directors.
Business Goals and New Strategy
ATN management decided to pursue a consolidation initiative and outsource applications maintenance and
operations overseas. This lowered costs but unfortunately did not address their overall operational inefficiency.
Applications still had overlapping functions that could not be easily consolidated. It eventually became
apparent that outsourcing was insufficient as consolidation became a possibility only if the architecture of the
entire IT landscape changed.
As a result, ATN decided to explore the potential of adopting cloud computing. However, subsequent to their
initial inquiries they became overwhelmed by the plenitude of cloud providers and cloud-based products.
Roadmap and Implementation Strategy
ATN is unsure of how to choose the right set of cloud computing technologies and vendors—many solutions
appear to still be immature and new cloud-based offerings continue to emerge in the market.
A preliminary cloud computing adoption roadmap is discussed to address a number of key points:
• IT Strategy – The adoption of cloud computing needs to promote optimization of the current IT
framework, and produce both lower short-term investments and consistent long-term cost reduction.
• Business Benefits – ATN needs to evaluate which of the current applications and IT infrastructure can
leverage cloud computing technology to achieve the desired optimization and cost reductions.
Additional cloud computing benefits such as greater business agility, scalability, and reliability need to
be realized to promote business value.
• Technology Considerations – Criteria need to be established to help choose the most appropriate cloud
delivery and deployment models and cloud vendors and products.
• Cloud Security – The risks associated with migrating applications and data to the cloud must be
determined.
ATN fears that they might lose control over their applications and data if entrusted to cloud providers,
leading to incompliance with internal policies and telecom market regulations. They also wonder how their
existing legacy applications would be integrated into the new cloud-based domain.
To define a succinct plan of action, ATN hires an independent IT consulting company called CloudEnhance,
42
who are well recognized for their technology architecture expertise in the transition and integration of cloud
computing IT resources. CloudEnhance consultants begin by suggesting an appraisal process comprised of
five steps:
1. A brief evaluation of existing applications to measures factors, such as complexity, business-criticality,
usage frequency, and number of active users. The identified factors are then placed in a hierarchy of
priority to help determine the most suitable candidate applications for migration to a cloud
environment.
2. A more detailed evaluation of each selected application using a proprietary assessment tool.
3. The development of a target application architecture that exhibits the interaction between cloud-based
applications, their integration with ATN’s existing infrastructure and legacy systems, and their
development and deployment processes.
4. The authoring of a preliminary business case that documents projected cost savings based on
performance indicators, such as cost of cloud readiness, effort for application transformation and
interaction, ease of migration and implementation, and various potential long-term benefits.
5. The development of a detailed project plan for a pilot application.
ATN proceeds with the process and resultantly builds its first prototype by focusing on an application that
automates a low-risk business area. During this project ATN ports several of the business area’s smaller
applications that were running on different technologies over to a PaaS platform. Based on positive results and
feedback received for the prototype project, ATN decides to embark on a strategic initiative to garner similar
benefits for other areas of the company.
2.2. Case Study #2: DTGOV
DTGOV is a public company that was created in the early 1980s by the Ministry of Social Security. The
decentralization of the ministry’s IT operations to a public company under private law gave DTGOV an
autonomous management structure with significant flexibility to govern and evolve its IT enterprise.
At the time of its creation, DTGOV had approximately 1,000 employees, operational branches in 60 localities
nation-wide, and operated two mainframe-based data centers. Over time, DTGOV has expanded to more
than 3,000 employees and branch offices in more than 300 localities, with three data centers running both
mainframe and low-level platform environments. Its main services are related to processing social security
benefits across the country.
DTGOV has enlarged its customer portfolio in the last two decades. It now serves other public-sector
organizations and provides basic IT infrastructure and services, such as server hosting and server colocation.
Some of its customers have also outsourced the operation, maintenance, and development of applications to
DTGOV.
DTGOV has sizable customer contracts that encompass various IT resources and services. However, these
contracts, services, and associated service levels are not standardized—negotiated service provisioning
conditions are typically customized for each customer individually. DTGOV’s operations are resultantly
becoming increasingly complex and difficult to manage, which has led to inefficiencies and inflated costs.
43
The DTGOV board realized, some time ago, that the overall company structure could be improved by
standardizing its services portfolio, which implies the reengineering of both IT operational and management
models. This process has started with the standardization of the hardware platform through the creation of a
clearly defined technological lifecycle, a consolidated procurement policy, and the establishment of new
acquisition practices.
Technical Infrastructure and Environment
DTGOV operates three data centers: one is exclusively dedicated to low-level platform servers while the other
two have both mainframe and low-level platforms. The mainframe systems are reserved for the Ministry of
Social Security and therefore not available for outsourcing.
The data center infrastructure occupies approximately 20,000 square feet of computer room space and hosts
more than 100,000 servers with different hardware configurations. The total storage capacity is approximately
10,000 terabytes. DTGOV’s network has redundant high-speed data links connecting the data centers in a
full mesh topology. Their Internet connectivity is considered to be provider-independent since their network
interconnects all of the major national telecom carriers.
Server consolidation and virtualization projects have been in place for five years, considerably decreasing the
diversity of hardware platforms. As a result, systematic tracking of the investments and operational costs
related to the hardware platform has revealed significant improvement. However, there is still remarkable
diversity in their software platforms and configurations due to customer service customization requirements.
Business Goals and New Strategy
A chief strategic objective of the standardization of DTGOV’s service portfolio is to achieve increased levels
of cost effectiveness and operational optimization. An internal executive-level commission was established to
define the directions, goals, and strategic roadmap for this initiative. The commission has identified cloud
computing as a guidance option and an opportunity for further diversification and improvement of services
and customer portfolios.
The roadmap addresses the following key points:
• Business Benefits – Concrete business benefits associated with the standardization of service portfolios
under the umbrella of cloud computing delivery models need to be defined. For example, how can the
optimization of IT infrastructure and operational models result in direct and measurable cost
reductions?
• Service Portfolio – Which services should become cloud-based, and which customers should they be
extended to?
• Technical Challenges – The limitations of the current technology infrastructure in relation to the
runtime processing requirements of cloud computing models must be understood and documented.
Existing infrastructure must be leveraged to whatever extent possible to optimize up-front costs
assumed by the development of the cloud-based service offerings.
• Pricing and SLAs – An appropriate contract, pricing, and service quality strategy needs to be defined.
Suitable pricing and service-level agreements (SLAs) must be determined to support the initiative.
44
One outstanding concern relates to changes to the current format of contracts and how they may impact
business. Many customers may not want to—or may not be prepared to—adopt cloud contracting and service
delivery models. This becomes even more critical when considering the fact that 90% of DTGOV’s current
customer portfolio is comprised of public organizations that typically do not have the autonomy or the agility
to switch operating methods on such short notice. Therefore, the migration process is expected to be long
term, which may become risky if the roadmap is not properly and clearly defined. A further outstanding issue
pertains to IT contract regulations in the public sector—existing regulations may become irrelevant or unclear
when applied to cloud technologies.
Roadmap and Implementation Strategy
Several assessment activities were initiated to address the aforementioned issues. The first was a survey of
existing customers to probe their level of understanding, on-going initiatives, and plans regarding cloud
computing. Most of the respondents were aware of and knowledgeable about cloud computing trends, which
was considered a positive finding.
An investigation of the service portfolio revealed clearly identified infrastructure services relating to hosting
and colocation. Technical expertise and infrastructure were also evaluated, determining that data center
operation and management are key areas of expertise of DTGOV IT staff.
With these findings, the commission decided to:
1. choose IaaS as the target delivery platform to start the cloud computing provisioning initiative
2. hire a consulting firm with sufficient cloud provider expertise and experience to correctly identify and
rectify any business and technical issues that may afflict the initiative
3. deploy new hardware resources with a uniform platform into two different data centers, aiming to
establish a new, reliable environment to use for the provisioning of initial IaaS-hosted services
4. identify three customers that plan to acquire cloud-based services in order to establish pilot projects
and define contractual conditions, pricing, and service-level policies and models
5. evaluate service provisioning of the three chosen customers for the initial period of six months before
publicly offering the service to other customers
As the pilot project proceeds, a new Web-based management environment is released to allow for the selfprovisioning of virtual servers, as well as SLA and financial tracking functionality in realtime. The pilot
projects are considered highly successful, leading to the next step of opening the cloud-based services to other
customers.
2.3. Case Study #3: Innovartus Technologies Inc.
The primary business line of Innovartus Technologies Inc. is the development of virtual toys and educational
entertainment products for children. These services are provided through a Web portal that employs a roleplaying model to create customized virtual games for PCs and mobile devices. The games allow users to create
and manipulate virtual toys (cars, dolls, pets) that can be outfitted with virtual accessories that are obtained by
completing simple educational quests. The main demographic is children under 12 years. Innovartus further
has a social network environment that enables users to exchange items and collaborate with others. All of
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these activities can be monitored and tracked by the parents, who can also participate in a game by creating
specific quests for their children.
The most valuable and revolutionary feature of Innovartus’ applications is an experimental end-user interface
that is based on natural interface concepts. Users can interact via voice commands, simple gestures that are
captured with a Webcam, and directly by touching tablet screens.
The Innovartus portal has always been cloud-based. It was originally developed via a PaaS platform and has
been hosted by the same cloud provider ever since. However, recently this environment has revealed several
technical limitations that impact features of Innovartus’ user interface programming frameworks.
Technical Infrastructure and Environment
Many of Innovartus’ other office automation solutions, such as shared file repositories and various productivity
tools, are also cloud-based. The on-premise corporate IT environment is relatively small, comprised mainly of
work area devices, laptops, and graphic design workstations.
Business Goals and Strategy
Innovartus has been diversifying the functionality of the IT resources that are used for their Web-based and
mobile applications. The company has also increased efforts to internationalize their applications; both the
Web site and the mobile applications are currently offered in five different languages.
Roadmap and Implementation Strategy
Innovartus intends to continue building upon its cloud-based solutions; however, the current cloud hosting
environment has limitations that need to be overcome:
• scalability needs to be improved to accommodate increased and less predictable cloud consumer
interaction
• service levels need to be improved to avoid outages that are currently more frequent than expected
• cost effectiveness needs to be improved, as leasing rates are higher with the current cloud provider
when compared to others
These and other factors have led Innovartus to decide to migrate to a larger, more globally established cloud
provider.
The roadmap for this migration project includes:
• a technical and economic report about the risks and impacts of the planned migration
• a decision tree and a rigorous study initiative focused on the criteria for selecting the new cloud
provider
• portability assessments of applications to determine how much of each existing cloud service
architecture is proprietary to the current cloud provider’s environment
Innovartus is further concerned about how and to what extent the current cloud provider will support and
cooperate with the migration process.
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Part I: Fundamental Cloud Computing
Chapter 3: Understanding Cloud Computing
Chapter 4: Fundamental Concepts and Models
Chapter 5: Cloud-Enabling Technology
Chapter 6: Fundamental Cloud Security
The upcoming chapters establish concepts and terminology that are referenced throughout subsequent
chapters and parts in this book. It is recommended that Chapters 3 and 4 be reviewed, even for those already
familiar with cloud computing fundamentals. Sections in Chapters 5 and 6 can be selectively skipped by those
already familiar with the corresponding technology and security topics.
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Chapter 3. Understanding Cloud Computing
3.1 Origins and Influences
3.2 Basic Concepts and Terminology
3.3 Goals and Benefits
3.4 Risks and Challenges
This is the first of two chapters that provide an overview of introductory cloud computing topics. It begins
with a brief history of cloud computing along with short descriptions of its business and technology drivers.
This is followed by definitions of basic concepts and terminology, in addition to explanations of the primary
benefits and challenges of cloud computing adoption.
3.1. Origins and Influences
A Brief History
The idea of computing in a “cloud” traces back to the origins of utility computing, a concept that computer
scientist John McCarthy publicly proposed in 1961:
“If computers of the kind I have advocated become the computers of the future, then computing may someday be
organized as a public utility just as the telephone system is a public utility. … The computer utility could become
the basis of a new and important industry.”
In 1969, Leonard Kleinrock, a chief scientist of the Advanced Research Projects Agency Network or
ARPANET project that seeded the Internet, stated:
“As of now, computer networks are still in their infancy, but as they grow up and become sophisticated, we will
probably see the spread of ‘computer utilities’ …”.
The general public has been leveraging forms of Internet-based computer utilities since the mid-1990s
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through various incarnations of search engines (Yahoo!, Google), e-mail services (Hotmail, Gmail), open
publishing platforms (MySpace, Facebook, YouTube), and other types of social media (Twitter, LinkedIn).
Though consumer-centric, these services popularized and validated core concepts that form the basis of
modern-day cloud computing.
In the late 1990s, Salesforce.com pioneered the notion of bringing remotely provisioned services into the
enterprise. In 2002, Amazon.com launched the Amazon Web Services (AWS) platform, a suite of enterpriseoriented services that provide remotely provisioned storage, computing resources, and business functionality.
A slightly different evocation of the term “Network Cloud” or “Cloud” was introduced in the early 1990s
throughout the networking industry. It referred to an abstraction layer derived in the delivery methods of data
across heterogeneous public and semi-public networks that were primarily packet-switched, although cellular
networks used the “Cloud” term as well. The networking method at this point supported the transmission of
data from one end-point (local network) to the “Cloud” (wide area network) and then further decomposed to
another intended end-point. This is relevant, as the networking industry still references the use of this term,
and is considered an early adopter of the concepts that underlie utility computing.
It wasn’t until 2006 that the term “cloud computing” emerged in the commercial arena. It was during this
time that Amazon launched its Elastic Compute Cloud (EC2) services that enabled organizations to “lease”
computing capacity and processing power to run their enterprise applications. Google Apps also began
providing browser-based enterprise applications in the same year, and three years later, the Google App
Engine became another historic milestone.
Definitions
A Gartner report listing cloud computing at the top of its strategic technology areas further reaffirmed its
prominence as an industry trend by announcing its formal definition as:
“…a style of computing in which scalable and elastic IT-enabled capabilities are delivered as a service to external
customers using Internet technologies.”
This is a slight revision of Gartner’s original definition from 2008, in which “massively scalable” was used
instead of “scalable and elastic.” This acknowledges the importance of scalability in relation to the ability to
scale vertically and not just to enormous proportions.
Forrester Research provided its own definition of cloud computing as:
“…a standardized IT capability (services, software, or infrastructure) delivered via Internet technologies in a
pay-per-use, self-service way.”
The definition that received industry-wide acceptance was composed by the National Institute of Standards
and Technology (NIST). NIST published its original definition back in 2009, followed by a revised version
after further review and industry input that was published in September of 2011:
“Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of
configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly
provisioned and released with minimal management effort or service provider interaction. This cloud model is
composed of five essential characteristics, three service models, and four deployment models.”
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This book provides a more concise definition:
“Cloud computing is a specialized form of distributed computing that introduces utilization models for remotely
provisioning scalable and measured resources.”
This simplified definition is in line with all of the preceding definition variations that were put forth by other
organizations within the cloud computing industry. The characteristics, service models, and deployment
models referenced in the NIST definition are further covered in Chapter 4.
Business Drivers
Before delving into the layers of technologies that underlie clouds, the motivations that led to their creation by
industry leaders must first be understood. Several of the primary business drivers that fostered modern cloudbased technology are presented in this section.
The origins and inspirations of many of the characteristics, models, and mechanisms covered throughout
subsequent chapters can be traced back to the upcoming business drivers. It is important to note that these
influences shaped clouds and the overall cloud computing market from both ends. They have motivated
organizations to adopt cloud computing in support of their business automation requirements. They have
correspondingly motivated other organizations to become providers of cloud environments and cloud
technology vendors in order to create and meet the demand to fulfill consumer needs.
Capacity Planning
Capacity planning is the process of determining and fulfilling future demands of an organization’s IT
resources, products, and services. Within this context, capacity represents the maximum amount of work that
an IT resource is capable of delivering in a given period of time. A discrepancy between the capacity of an IT
resource and its demand can result in a system becoming either inefficient (over-provisioning) or unable to
fulfill user needs (under-provisioning). Capacity planning is focused on minimizing this discrepancy to
achieve predictable efficiency and performance.
Different capacity planning strategies exist:
• Lead Strategy – adding capacity to an IT resource in anticipation of demand
• Lag Strategy – adding capacity when the IT resource reaches its full capacity
• Match Strategy – adding IT resource capacity in small increments, as demand increases
Planning for capacity can be challenging because it requires estimating usage load fluctuations. There is a
constant need to balance peak usage requirements without unnecessary over-expenditure on infrastructure. An
example is outfitting IT infrastructure to accommodate maximum usage loads which can impose unreasonable
financial investments. In such cases, moderating investments can result in under-provisioning, leading to
transaction losses and other usage limitations from lowered usage thresholds.
Cost Reduction
A direct alignment between IT costs and business performance can be difficult to maintain. The growth of IT
environments often corresponds to the assessment of their maximum usage requirements. This can make the
support of new and expanded business automations an ever-increasing investment. Much of this required
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investment is funneled into infrastructure expansion because the usage potential of a given automation
solution will always be limited by the processing power of its underlying infrastructure.
Two costs need to be accounted for: the cost of acquiring new infrastructure, and the cost of its ongoing
ownership. Operational overhead represents a considerable share of IT budgets, often exceeding up-front
investment costs.
Common forms of infrastructure-related operating overhead include the following:
• technical personnel required to keep the environment operational
• upgrades and patches that introduce additional testing and deployment cycles
• utility bills and capital expense investments for power and cooling
• security and access control measures that need to be maintained and enforced to protect infrastructure
resources
• administrative and accounts staff that may be required to keep track of licenses and support
arrangements
The on-going ownership of internal technology infrastructure can encompass burdensome responsibilities that
impose compound impacts on corporate budgets. An IT department can consequently become a significant—
and at times overwhelming—drain on the business, potentially inhibiting its responsiveness, profitability, and
overall evolution.
Organizational Agility
Businesses need the ability to adapt and evolve to successfully face change caused by both internal and external
factors. Organizational agility is the measure of an organization’s responsiveness to change.
An IT enterprise often needs to respond to business change by scaling its IT resources beyond the scope of
what was previously predicted or planned for. For example, infrastructure may be subject to limitations that
prevent the organization from responding to usage fluctuations—even when anticipated—if previous capacity
planning efforts were restricted by inadequate budgets.
In other cases, changing business needs and priorities may require IT resources to be more available and
reliable than before. Even if sufficient infrastructure is in place for an organization to support anticipated
usage volumes, the nature of the usage may generate runtime exceptions that bring down hosting servers. Due
to a lack of reliability controls within the infrastructure, responsiveness to consumer or customer requirements
may be reduced to a point whereby a business’ overall continuity is threatened.
On a broader scale, the up-front investments and infrastructure ownership costs that are required to enable
new or expanded business automation solutions may themselves be prohibitive enough for a business to settle
for IT infrastructure of less-than-ideal quality, thereby decreasing its ability to meet real-world requirements.
Worse yet, the business may decide against proceeding with an automation solution altogether upon review of
its infrastructure budget, because it simply cannot afford to. This form of inability to respond can inhibit an
organization from keeping up with market demands, competitive pressures, and its own strategic business
goals.
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Technology Innovations
Established technologies are often used as inspiration and, at times, the actual foundations upon which new
technology innovations are derived and built. This section briefly describes the pre-existing technologies
considered to be the primary influences on cloud computing.
Clustering
A cluster is a group of independent IT resources that are interconnected and work as a single system. System
failure rates are reduced while availability and reliability are increased, since redundancy and failover features
are inherent to the cluster.
A general prerequisite of hardware clustering is that its component systems have reasonably identical hardware
and operating systems to provide similar performance levels when one failed component is to be replaced by
another. Component devices that form a cluster are kept in synchronization through dedicated, high-speed
communication links.
The basic concept of built-in redundancy and failover is core to cloud platforms. Clustering technology is
explored further in Chapter 8 as part of the Resource Cluster mechanism description.
Grid Computing
A computing grid (or “computational grid”) provides a platform in which computing resources are organized
into one or more logical pools. These pools are collectively coordinated to provide a high performance
distributed grid, sometimes referred to as a “super virtual computer.” Grid computing differs from clustering
in that grid systems are much more loosely coupled and distributed. As a result, grid computing systems can
involve computing resources that are heterogeneous and geographically dispersed, which is generally not
possible with cluster computing-based systems.
Grid computing has been an on-going research area in computing science since the early 1990s. The
technological advancements achieved by grid computing projects have influenced various aspects of cloud
computing platforms and mechanisms, specifically in relation to common feature-sets such as networked
access, resource pooling, and scalability and resiliency. These types of features can be established by both grid
computing and cloud computing, in their own distinctive approaches.
For example, grid computing is based on a middleware layer that is deployed on computing resources. These
IT resources participate in a grid pool that implements a series of workload distribution and coordination
functions. This middle tier can contain load balancing logic, failover controls, and autonomic configuration
management, each having previously inspired similar—and several more sophisticated—cloud computing
technologies. It is for this reason that some classify cloud computing as a descendant of earlier grid computing
initiatives.
Virtualization
Virtualization represents a technology platform used for the creation of virtual instances of IT resources. A
layer of virtualization software allows physical IT resources to provide multiple virtual images of themselves so
that their underlying processing capabilities can be shared by multiple users.
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Prior to the advent of virtualization technologies, software was limited to residing on and being coupled with
static hardware environments. The virtualization process severs this software-hardware dependency, as
hardware requirements can be simulated by emulation software running in virtualized environments.
Established virtualization technologies can be traced to several cloud characteristics and cloud computing
mechanisms, having inspired many of their core features. As cloud computing evolved, a generation of modern
virtualization technologies emerged to overcome the performance, reliability, and scalability limitations of
traditional virtualization platforms.
As a foundation of contemporary cloud technology, modern virtualization provides a variety of virtualization
types and technology layers that are discussed separately in Chapter 5.
Technology Innovations vs. Enabling Technologies
It is essential to highlight several other areas of technology that continue to contribute to modern-day cloudbased platforms. These are distinguished as cloud-enabling technologies, the following of which are covered in
Chapter 5:
• Broadband Networks and Internet Architecture
• Data Center Technology
• (Modern) Virtualization Technology
• Web Technology
• Multitenant Technology
• Service Technology
Each of these cloud-enabling technologies existed in some form prior to the formal advent of cloud
computing. Some were refined further, and on occasion even redefined, as a result of the subsequent evolution
of cloud computing.
Summary of Key Points
• The primary business drivers that exposed the need for cloud computing and led to its formation
include capacity planning, cost reduction, and organizational agility.
• The primary technology innovations that influenced and inspired key distinguishing features and
aspects of cloud computing include clustering, grid computing, and traditional forms of
virtualization.
3.2. Basic Concepts and Terminology
This section establishes a set of basic terms that represent the fundamental concepts and aspects pertaining to
the notion of a cloud and its most primitive artifacts.
Cloud
A cloud refers to a distinct IT environment that is designed for the purpose of remotely provisioning scalable
and measured IT resources. The term originated as a metaphor for the Internet which is, in essence, a
network of networks providing remote access to a set of decentralized IT resources. Prior to cloud computing
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becoming its own formalized IT industry segment, the symbol of a cloud was commonly used to represent the
Internet in a variety of specifications and mainstream documentation of Web-based architectures. This same
symbol is now used to specifically represent the boundary of a cloud environment, as shown in Figure 3.1.
Figure 3.1 The symbol used to denote the boundary of a cloud environment.
It is important to distinguish the term “cloud” and the cloud symbol from the Internet. As a specific
environment used to remotely provision IT resources, a cloud has a finite boundary. There are many
individual clouds that are accessible via the Internet. Whereas the Internet provides open access to many
Web-based IT resources, a cloud is typically privately owned and offers access to IT resources that is metered.
Much of the Internet is dedicated to the access of content-based IT resources published via the World Wide
Web. IT resources provided by cloud environments, on the other hand, are dedicated to supplying back-end
processing capabilities and user-based access to these capabilities. Another key distinction is that it is not
necessary for clouds to be Web-based even if they are commonly based on Internet protocols and
technologies. Protocols refer to standards and methods that allow computers to communicate with each other
in a pre-defined and structured manner. A cloud can be based on the use of any protocols that allow for the
remote access to its IT resources.
Note
Diagrams in this book depict the Internet using the globe symbol.
IT Resource
An IT resource is a physical or virtual IT-related artifact that can be either software-based, such as a virtual
server or a custom software program, or hardware-based, such as a physical server or a network device (Figure
3.2).
Figure 3.2 Examples of common IT resources and their corresponding symbols.
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Figure 3.3 illustrates how the cloud symbol can be used to define a boundary for a cloud-based environment
that hosts and provisions a set of IT resources. The displayed IT resources are consequently considered to be
cloud-based IT resources.
Figure 3.3 A cloud is hosting eight IT resources: three virtual servers, two cloud services, and three storage
devices.
Technology architectures and various interaction scenarios involving IT resources are illustrated in diagrams
like the one shown in Figure 3.3. It is important to note the following points when studying and working with
these diagrams:
• The IT resources shown within the boundary of a given cloud symbol usually do not represent all of the
available IT resources hosted by that cloud. Subsets of IT resources are generally highlighted to
demonstrate a particular topic.
• Focusing on the relevant aspects of a topic requires many of these diagrams to intentionally provide
abstracted views of the underlying technology architectures. This means that only a portion of the
actual technical details are shown.
Furthermore, some diagrams will display IT resources outside of the cloud symbol. This convention is used to
indicate IT resources that are not cloud-based.
Note
The virtual server IT resource displayed in Figure 3.2 is further discussed in Chapters 5 and 7.
Physical servers are sometimes referred to as physical hosts (or just hosts) in reference to the fact that
they are responsible for hosting virtual servers.
On-Premise
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As a distinct and remotely accessible environment, a cloud represents an option for the deployment of IT
resources. An IT resource that is hosted in a conventional IT enterprise within an organizational boundary
(that does not specifically represent a cloud) is considered to be located on the premises of the IT enterprise,
or on-premise for short. In other words, the term “on-premise” is another way of stating “on the premises of a
controlled IT environment that is not cloud-based.” This term is used to qualify an IT resource as an
alternative to “cloud-based.” An IT resource that is on-premise cannot be cloud-based, and vice-versa.
Note the following key points:
• An on-premise IT resource can access and interact with a cloud-based IT resource.
• An on-premise IT resource can be moved to a cloud, thereby changing it to a cloud-based IT resource.
• Redundant deployments of an IT resource can exist in both on-premise and cloud-based environments.
If the distinction between on-premise and cloud-based IT resources is confusing in relation to private clouds
(described in the Cloud Deployment Models section of Chapter 4), then an alternative qualifier can be used.
Cloud Consumers and Cloud Providers
The party that provides cloud-based IT resources is the cloud provider. The party that uses cloud-based IT
resources is the cloud consumer. These terms represent roles usually assumed by organizations in relation to
clouds and corresponding cloud provisioning contracts. These roles are formally defined in Chapter 4, as part
of the Roles and Boundaries section.
Scaling
Scaling, from an IT resource perspective, represents the ability of the IT resource to handle increased or
decreased usage demands.
The following are types of scaling:
• Horizontal Scaling – scaling out and scaling in
• Vertical Scaling – scaling up and scaling down
The next two sections briefly describe each.
Horizontal Scaling
The allocating or releasing of IT resources that are of the same type is referred to as horizontal scaling (Figure
3.4). The horizontal allocation of resources is referred to as scaling out and the horizontal releasing of resources
is referred to as scaling in. Horizontal scaling is a common form of scaling within cloud environments.
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Figure 3.4 An IT resource (Virtual Server A) is scaled out by adding more of the same IT resources (Virtual
Servers B and C).
Vertical Scaling
When an existing IT resource is replaced by another with higher or lower capacity, vertical scaling is
considered to have occurred (Figure 3.5). Specifically, the replacing of an IT resource with another that has a
higher capacity is referred to as scaling up and the replacing an IT resource with another that has a lower
capacity is considered scaling down. Vertical scaling is less common in cloud environments due to the
downtime required while the replacement is taking place.
Figure 3.5 An IT resource (a virtual server with two CPUs) is scaled up by replacing it with a more powerful
IT resource with increased capacity for data storage (a physical server with four CPUs).
Table 3.1 provides a brief overview of common pros and cons associated with horizontal and vertical scaling.
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Table 3.1 A comparison of horizontal and vertical scaling.
Cloud Service
Although a cloud is a remotely accessible environment, not all IT resources residing within a cloud can be
made available for remote access. For example, a database or a physical server deployed within a cloud may
only be accessible by other IT resources that are within the same cloud. A software program with a published
API may be deployed specifically to enable access by remote clients.
A cloud service is any IT resource that is made remotely accessible via a cloud. Unlike other IT fields that fall
under the service technology umbrella—such as service-oriented architecture—the term “service” within the
context of cloud computing is especially broad. A cloud service can exist as a simple Web-based software
program with a technical interface invoked via the use of a messaging protocol, or as a remote access point for
administrative tools or larger environments and other IT resources.
In Figure 3.6, the yellow circle symbol is used to represent the cloud service as a simple Web-based software
program. A different IT resource symbol may be used in the latter case, depending on the nature of the access
that is provided by the cloud service.
Figure 3.6 A cloud service with a published technical interface is being accessed by a consumer outside of the
cloud (left). A cloud service that exists as a virtual server is also being accessed from outside of the cloud’s
boundary (right). The cloud service on the left is likely being invoked by a consumer program that was
designed to access the cloud service’s published technical interface. The cloud service on the right may be
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accessed by a human user that has remotely logged on to the virtual server.
The driving motivation behind cloud computing is to provide IT resources as services that encapsulate other
IT resources, while offering functions for clients to use and leverage remotely. A multitude of models for
generic types of cloud services have emerged, most of which are labeled with the “as-a-service” suffix.
Note
Cloud service usage conditions are typically expressed in a service-level agreement (SLA) that is the
human-readable part of a service contract between a cloud provider and cloud consumer that describes
QoS features, behaviors, and limitations of a cloud-based service or other …