Fundamental Concepts-and-Models Cloud Computing

Fundamental
Concepts and Models
Mohammed Sajjad Ali
PMP, CCNP, E-commerce
Place photo here
“Reference: Cloud Computing Concepts, Technology & Architecture.
Thomas Erl, Zaigham Mahmood and Richardo Puttini.”
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Sartaj Fatima
Lecturer,

Contents :
4.1 Roles and Boundaries
4.2 Cloud Characteristics
4.3 Cloud Delivery Models
4.4 Cloud Deployment Models
Fundamental Concepts and Models
“The upcoming sections cover introductory topic areas pertaining to the fundamental
models used to categorize and define clouds and their most common service offerings,
along with definitions of organizational roles and the specific set of characteristics that
collectively distinguish a cloud.”
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4.1. Roles and Boundaries
Organizations and humans can assume different types of pre-defined roles
depending on how they relate to and/or interact with a cloud and its hosted IT
resources.
Each of the upcoming roles participates in and carries out responsibilities in
relation to cloud-based activity. The following sections define these roles and
identify their main interactions.
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Cloud Provider
The organization that provides cloud-based IT resources is the cloud provider. When
assuming the role of cloud provider, an organization is responsible for making cloud
services available to cloud consumers, as per agreed upon SLA guarantees. The cloud
provider is further tasked with any required management and administrative duties to
ensure the on-going operation of the overall cloud infrastructure.
Cloud providers normally own the IT resources that are made available for lease by cloud
consumers; however, some cloud providers also “resell” IT resources leased from other
cloud providers.
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Cloud Consumer
A cloud consumer is an organization (or a human) that has a formal contract or
arrangement with a cloud provider to use IT resources made available by the cloud
provider. Specifically, the cloud consumer uses a cloud service consumer to access a
cloud service (Figure 4.1).
Figure 4.1. A cloud consumer (Organization A) interacts with a cloud service
from a cloud provider (that owns Cloud A). Within Organization A, the cloud
service consumer is being used to access the cloud service.
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Cloud Service Owner
 The person or organization that legally owns a cloud service is called a cloud
service owner.
 The cloud service owner can be the cloud consumer, or the cloud provider that
owns the cloud within which the cloud service resides.
 For example, either the cloud consumer of Cloud X or the cloud provider of
Cloud X could own Cloud Service A (Figures 4.2 and 4.3).
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Figure 4.2. A cloud consumer can be a cloud
service owner when it deploys its own service in
a cloud.
Figure 4.3. A cloud provider becomes a cloud
service owner if it deploys its own cloud service,
typically for other cloud consumers to use.
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Cloud Resource Administrator
A cloud resource administrator is the person or organization responsible for
administering a cloud-based IT resource (including cloud services).
The cloud resource administrator can be (or belong to) the cloud consumer or
cloud provider of the cloud within which the cloud service resides.
 Alternatively, it can be (or belong to) a third-party organization contracted to
administer the cloud-based IT resource.
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For example, a cloud service owner can contract a cloud resource administrator to
administer a cloud service (Figures 4.4 and 4.5).
Figure 4.4. A cloud resource administrator can be with a cloud consumer
organization and administer remotely accessible IT resources that belong
to the cloud consumer.
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Figure 4.5. A cloud resource administrator can be with a cloud provider organization for which
it can administer the cloud provider’s internally and externally available IT resources.
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Additional Roles
 Cloud Auditor – A third-party (often accredited) that conducts independent
assessments of cloud environments assumes the role of the cloud auditor. The
typical responsibilities associated with this role include the evaluation of security
controls, privacy impacts, and performance. The main purpose of the cloud auditor
role is to provide an unbiased assessment (and possible endorsement) of a cloud
environment to help strengthen the trust relationship between cloud consumers and
cloud providers.
 Cloud Broker – This role is assumed by a party that assumes the responsibility of
managing and negotiating the usage of cloud services between cloud consumers
and cloud providers. Mediation services provided by cloud brokers include service
intermediation, aggregation, and arbitrage.
 Cloud Carrier – The party responsible for providing the wire-level connectivity
between cloud consumers and cloud providers assumes the role of the cloud
carrier. This role is often assumed by network and telecommunication providers.
While each is legitimate, most architectural scenarios covered in this book do not
include these roles.
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Organizational Boundary
 An organizational boundary represents the physical perimeter that surrounds a set
of IT resources that are owned and governed by an organization. The
organizational boundary does not represent the boundary of an actual
organization, only an organizational set of IT assets and IT resources. Similarly, clouds
have an organizational boundary (Figure 4.6).
Figure 4.6. Organizational boundaries of a cloud consumer (left), and a
cloud provider (right), represented by a broken line notation.
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Trust Boundary
When an organization assumes the role of cloud consumer to access cloud-based
IT resources, it needs to extend its trust beyond the physical boundary of the
organization to include parts of the cloud environment.
A trust boundary is a logical perimeter that typically spans beyond physical
boundaries to represent the extent to which IT resources are trusted (Figure 4.7).
Figure 4.7. An extended trust boundary encompasses the organizational
boundaries of the cloud provider and the cloud consumer.
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4.2. Cloud Characteristics
An IT environment requires a specific set of characteristics to enable the remote
provisioning of scalable and measured IT resources in an effective manner.
These characteristics need to exist to a meaningful extent for the IT environment
to be considered an effective cloud.
The following six specific characteristics are common to the majority of cloud
environments:
• On-demand usage
• Ubiquitous access
• Multitenancy (and resource pooling)
• Elasticity
• Measured usage
• Resiliency
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On-Demand Usage
A cloud consumer can unilaterally access cloud-based IT resources giving the cloud
consumer the freedom to self-provision these IT resources. Once configured, usage
of the self-provisioned IT resources can be automated, requiring no further human
involvement by the cloud consumer or cloud provider. This results in an on-demand
usage environment. Also known as “on-demand self-service usage,” this
characteristic enables the service-based and usage-driven features found in
mainstream clouds.
Ubiquitous Access
Ubiquitous access represents the ability for a cloud service to be widely accessible.
Establishing ubiquitous access for a cloud service can require support for a range of
devices, transport protocols, interfaces, and security technologies. To enable this
level of access generally requires that the cloud service architecture be tailored to
the particular needs of different cloud service consumers.
Multitenancy (and Resource Pooling)
Resource pooling allows cloud providers to pool large-scale IT resources to serve
multiple cloud consumers. Different physical and virtual IT resources are dynamically
assigned and reassigned according to cloud consumer demand, typically followed
by execution through statistical multiplexing. Resource pooling is commonly
achieved through multitenancy technology, and therefore encompassed by this
multitenancy characteristic.
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Figure 4.8. In a single-tenant environment, each cloud
consumer has a separate IT resource instance.
Figure 4.9. In a multitenant environment, a single instance of
an IT resource, such as a cloud storage device, serves
multiple consumers.
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Elasticity
Elasticity is the automated ability of a cloud to transparently scale IT resources, as required in
response to runtime conditions or as pre-determined by the cloud consumer or cloud
provider. Elasticity is often considered a core justification for the adoption of cloud
computing, primarily due to the fact that it is closely associated with the Reduced
Investment and Proportional Costs benefit. Cloud providers with vast IT resources can offer
the greatest range of elasticity.
Measured Usage
The measured usage characteristic represents the ability of a cloud platform to keep track
of the usage of its IT resources, primarily by cloud consumers. Based on what is measured,
the cloud provider can charge a cloud consumer only for the IT resources actually used
and/or for the timeframe during which access to the IT resources was granted. In this
context, measured usage is closely related to the on-demand characteristic. Measured
usage is not limited to tracking statistics for billing purposes. It also encompasses the general
monitoring of IT resources and related usage reporting (for both cloud provider and cloud
consumers). Therefore, measured usage is also relevant to clouds that do not charge for
usage (which may be applicable to the private cloud deployment model described in the
upcoming Cloud Deployment Models section).
Resiliency
Resilient computing is a form of failover that distributes redundant implementations of IT
resources across physical locations. IT resources can be pre-configured so that if one
becomes deficient, processing is automatically handed over to another redundant
implementation. Within cloud computing, the characteristic of resiliency can refer to
redundant IT resources within the same cloud (but in different physical locations) or across
multiple clouds. Cloud consumers can increase both the reliability and availability of their
applications by leveraging the resiliency of cloud-based IT resources (Figure 4.10). 17

Figure 4.10. A resilient system in which Cloud B hosts a
redundant implementation of Cloud Service A to provide
failover in case Cloud Service A on Cloud A becomes
unavailable.
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4.3. Cloud Delivery Models
A cloud delivery model represents a specific, pre-packaged combination of IT
resources offered by a cloud provider. Three common cloud delivery models
have become widely established and formalized:
• Infrastructure-as-a-Service (IaaS)
• Platform-as-a-Service (PaaS)
• Software-as-a-Service (SaaS)
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Infrastructure-as-a-Service (IaaS)
The IaaS delivery model represents a self-contained IT environment comprised of
infrastructure-centric IT resources that can be accessed and managed via cloud
service-based interfaces and tools.
This environment can include hardware, network, connectivity, operating systems,
and other “raw” IT resources. In contrast to traditional hosting or outsourcing
environments, with IaaS, IT resources are typically virtualized and packaged into
bundles that simplify up-front runtime scaling and customization of the
infrastructure.
Figure 4.11. A cloud consumer is using a virtual server within an IaaS environment. Cloud
consumers are provided with a range of contractual guarantees by the cloud provider,
pertaining to characteristics such as capacity, performance, and availability.
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Platform-as-a-Service (PaaS)
The PaaS delivery model represents a pre-defined “ready-to-use” environment
typically comprised of already deployed and configured IT resources. Specifically,
PaaS relies on (and is primarily defined by) the usage of a ready-made environment
that establishes a set of pre-packaged products and tools used to support the
entire delivery lifecycle of custom applications.
Common reasons a cloud consumer would use and invest in a PaaS environment
include:
• The cloud consumer wants to extend on-premise environments into the cloud for
scalability and economic purposes.
• The cloud consumer uses the ready-made environment to entirely substitute an
on-premise environment.
• The cloud consumer wants to become a cloud provider and deploys its own
cloud services to be made available to other external cloud consumers.
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Figure 4.12. A cloud consumer is accessing a ready-made PaaS environment.
The question mark indicates that the cloud consumer is intentionally shielded
from the implementation details of the platform.
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Software-as-a-Service (SaaS)
A software program positioned as a shared cloud service and made available as a
“product” or generic utility represents the typical profile of a SaaS offering. The SaaS
delivery model is typically used to make a reusable cloud service widely available
(often commercially) to a range of cloud consumers. An entire marketplace exists
around SaaS products that can be leased and used for different purposes and via
different terms (Figure 4.13).
Figure 4.13. The cloud service consumer is given access the cloud
service contract, but not to any underlying IT resources or
implementation details. 23

Comparing Cloud Delivery Models
Provided in this section are three tables that compare different aspects of cloud
delivery model usage and implementation. Table 4.1 contrasts control levels and
Table 4.2 compares typical responsibilities and usage.
Table 4.1. A comparison of typical cloud delivery model control levels.
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Table 4.2. Typical activities carried out by cloud consumers and cloud providers in relation
to the cloud delivery models.
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IaaS + PaaS
A PaaS environment will be built upon an underlying infrastructure comparable to
the physical and virtual servers and other IT resources provided in an IaaS
environment. Figure 4.14 shows how these two models can conceptually be
combined into a simple layered architecture.
Figure 4.14. A PaaS environment based on the IT resources
provided by an underlying IaaS environment.
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Figure 4.15. An example of a contract
between Cloud Providers X and Y, in
which services offered by Cloud Provider X
are physically hosted on virtual servers
belonging to Cloud Provider Y. Sensitive
data that is legally required to stay in a
specific region is physically kept in Cloud
B, which is physically located in that
region.
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IaaS + PaaS + SaaS
All three cloud delivery models can be combined to establish layers of IT resources
that build upon each other. For example, by adding on to the preceding layered
architecture shown in Figure 4.15.
The ready-made environment provided by the PaaS environment can be used by
the cloud consumer organization to develop and deploy its own SaaS cloud
services that it can then make available as commercial products (Figure 4.16).
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Figure 4.16. A simple layered view of
an architecture comprised of IaaS
and PaaS environments hosting three
SaaS cloud service implementations.
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4.4. Cloud Deployment Models
A cloud deployment model represents a specific type of cloud environment,
primarily distinguished by ownership, size, and access.
There are four common cloud deployment models:
• Public cloud
• Community cloud
• Private cloud
• Hybrid cloud
The following sections describe each.
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Public Clouds
A public cloud is a publicly accessible cloud environment owned by a third-party
cloud provider. The IT resources on public clouds are usually provisioned via the
previously described cloud delivery models and are generally offered to cloud
consumers at a cost or are commercialized via other avenues (such as
advertisement).
The cloud provider is responsible for the creation and on-going maintenance of the
public cloud and its IT resources. Many of the scenarios and architectures explored
in upcoming chapters involve public clouds and the relationship between the
providers and consumers of IT resources via public clouds.
Figure 4.17 shows a partial view of the public cloud landscape, highlighting some of
the primary vendors in the marketplace.
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Figure 4.17. Organizations act as cloud
consumers when accessing cloud
services and IT resources made
available by different cloud providers.
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Community Clouds
A community cloud is similar to a public cloud except that its access is limited to a
specific community of cloud consumers. The community cloud may be jointly
owned by the community members or by a third-party cloud provider that
provisions a public cloud with limited access. The member cloud consumers of the
community typically share the responsibility for defining and evolving the
community cloud (Figure 4.18).
Figure 4.18. An example of a “community” of
organizations accessing IT resources from a
community cloud.
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Private Clouds
A private cloud is owned by a single organization. Private clouds enable an
organization to use cloud computing technology as a means of centralizing access
to IT resources by different parts, locations, or departments of the organization.
The use of a private cloud can change how organizational and trust boundaries
are defined and applied. The actual administration of a private cloud environment
may be carried out by internal or outsourced staff.
With a private cloud, the same organization is technically both the cloud consumer
and cloud provider (Figure 4.19). In order to differentiate these roles:
• a separate organizational department typically assumes the responsibility for
provisioning the cloud (and therefore assumes the cloud provider role)
• departments requiring access to the private cloud assume the cloud consumer
role
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Figure 4.19. A cloud service consumer in the organization’s on-premise
environment accesses a cloud service hosted on the same organization’s
private cloud via a virtual private network. 35

Hybrid Clouds
A hybrid cloud is a cloud environment comprised
of two or more different cloud deployment
models. For example, a cloud consumer may
choose to deploy cloud services processing
sensitive data to a private cloud and other, less
sensitive cloud services to a public cloud. The
result of this combination is a hybrid deployment
model (Figure 4.20).
Figure 4.20. An organization using a hybrid cloud
architecture that utilizes both a private and public cloud.
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Other Cloud Deployment Models
Additional variations of the four base cloud deployment models can exist. Examples
include:
• Virtual Private Cloud – Also known as a “dedicated cloud” or “hosted cloud,” this
model results in a self-contained cloud environment hosted and managed by a
public cloud provider, and made available to a cloud consumer.
• Inter-Cloud – This model is based on an architecture comprised of two or more
inter-connected clouds.
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Hope this is been informative and I would like to thank you for viewing.
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Fundamental Concepts-and-Models Cloud Computing

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