Cloud Computing - Unit 2

Unit II: Service Delivery and Deployment Models: Service Models

(XaaS): Infrastructure as a Service (IaaS) - Platform as a Service (PaaS)
- Software as a Service(SaaS) - Deployment Models: Types of cloud -
Public cloud - Private cloud - Hybrid cloud – Service level agreements -
Types of SLA – Lifecycle of SLA- SLA Management.

Cloud Service Models

There are the following three types of cloud service models -

1. Infrastructure as a Service (IaaS)

2. Platform as a Service (PaaS)
3. Software as a Service (SaaS)

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Infrastructure as a Service (IaaS)

IaaS is also known as Hardware as a Service (HaaS). It is a computing

infrastructure managed over the internet. The main advantage of using
IaaS is that it helps users to avoid the cost and complexity of purchasing
and managing the physical servers.

Characteristics of IaaS

There are the following characteristics of IaaS -

● Resources are available as a service

● Services are highly scalable
● Dynamic and flexible
● GUI and API-based access
● Automated administrative tasks

Example: DigitalOcean, Linode, Amazon Web Services (AWS), Microsoft

Azure, Google Compute Engine (GCE), Rackspace, and Cisco Metacloud.

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Infrastructure as a Service | IaaS

 Iaas is also known as Hardware as a Service (HaaS). It is one of

the layers of the cloud computing platform.

 It allows customers to outsource their IT infrastructures such as

servers, networking, processing, storage, virtual machines,
and other resources. Customers access these resources on the
Internet using a pay-as-per use model

 In traditional hosting services, IT infrastructure was rented out for a

specific period of time, with pre-determined hardware configuration.
The client paid for the configuration and time, regardless of the
actual use. With the help of the IaaS cloud computing platform
layer, clients can dynamically scale the configuration to meet
changing requirements and are billed only for the services
actually used.

 IaaS cloud computing platform layer eliminates the need for every
organization to maintain the IT infrastructure.

 IaaS is offered in three models: public, private, and hybrid

cloud.

 The private cloud implies that the infrastructure resides at the

customer-premise.

 In the case of public cloud, it is located at the cloud computing

platform vendor's data center.

 The hybrid cloud is a combination of the two in which the customer

selects the best of both public cloud or private cloud.

All the physical resources or hardware—like laptops, desktops,

cables, switches, routers, data centers, and storage devices—are
a part of infrastructure. In cloud computing, all the infrastructure is
virtualized and provided to consumers as a service. This is called IaaS.

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IaaS provider provides the following services -

1. Compute: Computing as a Service includes virtual central

processing units and virtual main memory for the VMS that is
provisioned to the end- users.
2. Storage: IaaS provider provides back-end storage for storing
files.
3. Network: Network as a Service (NaaS) provides networking
components such as routers, switches, and bridges for the Vms.
4. Load balancers: It provides load balancing capability at the
infrastructure layer.

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Basic architecture of IaaS with the fundamental components, i.e. storage,
compute, network, virtualization

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 Example IaaS architecture with basic components and additional
offerings

Virtualization technology

 Virtualization of resources can be done using a hypervisor.

 A hypervisor is a software product that shares one physical resource

with multiple virtual machines.

 A cloud provider uses network protocols like fiber channel, iSCSI,

and NFS to split a physical network into logical partitions (or views).

 For example, the hypervisor can provide networking as a service to

the virtual machines using routing, bridging, or network address
translation.

 Some popular hypervisors are Microsoft Hyper-V and VMware

vSphere.

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Advantages of IaaS cloud computing layer

There are the following advantages of IaaS computing layer -

1. Shared infrastructure

IaaS allows multiple users to share the same physical

infrastructure.

2. Web access to the resources

Iaas allows IT users to access resources over the internet.

3. Pay-as-per-use model

IaaS providers provide services based on the pay-as-per-use basis. The

users are required to pay for what they have used.

4. Focus on the core business

IaaS providers focus on the organization's core business rather than

on IT infrastructure.

5. On-demand scalability

On-demand scalability is one of the biggest advantages of IaaS. Using

IaaS, users do not worry about to upgrade software and troubleshoot
the issues related to hardware components.
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Disadvantages of IaaS cloud computing layer

1. Security

Security is one of the biggest issues in IaaS. Most of the IaaS providers are
not able to provide 100% security.

2. Maintenance & Upgrade

Although IaaS service providers maintain the software, but they do not
upgrade the software for some organizations.

3. Interoperability issues

It is difficult to migrate VM from one IaaS provider to the other, so the

customers might face problem related to vendor lock-in.

Some important point about IaaS cloud computing layer

 IaaS cloud computing platform cannot replace the traditional

hosting method, but it provides more than that, and each resource
which are used are predictable as per the usage.

 IaaS cloud computing platform may not eliminate the need for an in-
house IT department. It will be needed to monitor or control the IaaS
setup. IT salary expenditure might not reduce significantly, but
other IT expenses can be reduced.

 Breakdowns at the IaaS cloud computing platform vendor's can

bring your business to the halt stage. Assess the IaaS cloud
computing platform vendor's stability and finances. Make sure that
SLAs (i.e., Service Level Agreement) provide backups for data,
hardware, network, and application failures. Image portability and
third-party support is a plus point.

 The IaaS cloud computing platform vendor can get access to your
sensitive data. So, engage with credible companies or organizations.
Study their security policies and precautions.

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Platform as a Service (PaaS)

PaaS cloud computing platform is created for the programmer to

develop, test, run, and manage the applications.

Characteristics of PaaS

There are the following characteristics of PaaS -

● Accessible to various users via the same development

application.
● Integrates with web services and databases.
● Builds on virtualization technology, so resources can easily be
scaled up or down as per the organization's need.
● Support multiple languages and frameworks.
● Provides an ability to "Auto-scale".

Example: AWS Elastic Beanstalk, Windows Azure, Heroku, Force.com,

Google App Engine, Apache Stratos, Magento Commerce Cloud, and
OpenShift.

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Platform as a Service | PaaS

Platform as a Service (PaaS) provides a runtime environment. It allows

programmers to easily create, test, run, and deploy web
applications. You can purchase these applications from a cloud service
provider on a pay-as-per use basis and access them using the Internet
connection.

In PaaS, back end scalability is managed by the cloud service

provider, so end- users do not need to worry about managing the
infrastructure.

PaaS includes infrastructure (servers, storage, and networking) and

platform (middleware, development tools, database management
systems, business intelligence, and more) to support the web
application life cycle.

Example: Google App Engine, Force.com, Joyent, Azure.

PaaS providers provide the Programming languages, Application

frameworks, Databases, and Other tools:

1. Programming languages

PaaS providers provide various programming languages for the

developers to develop the applications. Some popular programming
languages provided by PaaS providers are Java, PHP, Ruby, Perl, and
Go.

2. Application frameworks

PaaS providers provide application frameworks to easily understand

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the application development. Some popular application frameworks
provided by PaaS providers are Node.js, Drupal, Joomla, WordPress,
Spring, Play, Rack, and Zend.

3. Databases

PaaS providers provide various databases such as ClearDB,

PostgreSQL, MongoDB, and Redis to communicate with the
applications.

4. Other tools

PaaS providers provide various other tools that are required to develop,
test, and deploy the applications.

Advantages of PaaS

There are the following advantages of PaaS -

1) Simplified Development

PaaS allows developers to focus on development and innovation

without worrying about infrastructure management.

2) Lower risk

No need for up-front investment in hardware and software.

Developers only need a PC and an internet connection to start building
applications.

3) Prebuilt business functionality

Some PaaS vendors also provide already defined business

functionality so that users can avoid building everything from very
scratch and hence can directly start the projects only.

4) Instant community

PaaS vendors frequently provide online communities where the

developer can get the ideas to share experiences and seek advice
from others.

5) Scalability

Applications deployed can scale from one to thousands of users

without any changes to the applications.

Disadvantages of PaaS cloud computing layer

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1) Vendor lock-in

One has to write the applications according to the platform provided

by the PaaS vendor, so the migration of an application to another
PaaS vendor would be a problem.

2) Data Privacy

Corporate data, whether it can be critical or not, will be private, so if it

is not located within the walls of the company, there can be a risk in
terms of privacy of data.

3) Integration with the rest of the systems applications

It may happen that some applications are local, and some are in the
cloud. So there will be chances of increased complexity when we
want to use data which in the cloud with the local data.

Popular PaaS Providers

The below table shows some popular PaaS providers and services that are
provided by them -

Providers Services

Google App App Identity, URL Fetch, Cloud storage client library,

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Engine (GAE) Logservice

Salesforce.com Faster implementation, Rapid scalability, CRM

Services, Sales cloud, Mobile connectivity, Chatter.

Windows Azure Compute, security, IoT, Data Storage.

AppFog Justcloud.com, SkyDrive, GoogleDocs

Openshift RedHat, Microsoft Azure.

Cloud Foundry Data, Messaging, and other services.

from VMware

Software as a Service | SaaS

SaaS is also known as "On-Demand Software". It is a software

distribution model in which services are hosted by a cloud service
provider. These services are available to end-users over the internet
so, the end-users do not need to install any software on their devices to
access these services.

There are the following services provided by SaaS providers -

Business Services - SaaS Provider provides various business services to

start-up the business. The SaaS business services include ERP (Enterprise
Resource Planning), CRM (Customer Relationship Management), billing,
and sales.

Document Management - SaaS document management is a software

application offered by a third party (SaaS providers) to create,
manage, and track electronic documents.

Example: Slack, Samepage, Box, and Zoho Forms.

Social Networks - As we all know, social networking sites are used by

the general public, so social networking service providers use SaaS for
their convenience and handle the general public's information.

Mail Services - To handle the unpredictable number of users and

load on e-mail services, many e-mail providers offering their services
using SaaS.

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Advantages of SaaS cloud computing layer

1) SaaS is easy to buy

SaaS pricing is based on a monthly fee or annual fee subscription,

so it allows organizations to access business functionality at a low cost,
which is less than licensed applications.

Unlike traditional software, which is sold as a licensed based with an up-

front cost (and often an optional ongoing support fee), SaaS
providers are generally pricing the applications using a subscription
fee, most commonly a monthly or annually fee.

2. One to Many

SaaS services are offered as a one-to-many model means a single

instance of the application is shared by multiple users.

3. Less hardware required for SaaS

The software is hosted remotely, so organizations do not need to

invest in additional hardware.

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4. Low maintenance required for SaaS

Software as a service removes the need for installation, set-up, and

daily maintenance for the organizations. The initial set-up cost for
SaaS is typically less than the enterprise software. SaaS vendors are
pricing their applications based on some usage parameters, such as
a number of users using the application. So SaaS does easy to monitor
and automatic updates.

5. No special software or hardware versions required

All users will have the same version of the software and typically
access it through the web browser. SaaS reduces IT support costs by
outsourcing hardware and software maintenance and support to the IaaS
provider.

6. Multidevice support

SaaS services can be accessed from any device such as desktops,

laptops, tablets, phones, and thin clients.

7. API Integration

SaaS services easily integrate with other software or services through

standard APIs.

8. No client-side installation

SaaS services are accessed directly from the service provider using
the internet connection, so do not need to require any software
installation.

Disadvantages of SaaS cloud computing layer

1) Security

Actually, data is stored in the cloud, so security may be an issue for some
users. However, cloud computing is not more secure than in-house
deployment.

2) Latency issue

Since data and applications are stored in the cloud at a variable

distance from the end-user, there is a possibility that there may be
greater latency when interacting with the application compared to local
deployment. Therefore, the SaaS model is not suitable for applications
whose demand response time is in milliseconds.

3) Total Dependency on Internet

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Without an internet connection, most SaaS applications are not usable.

4) Switching between SaaS vendors is difficult

Switching SaaS vendors involves the difficult and slow task of transferring
the very large data files over the internet and then converting and
importing them into another SaaS also.

Popular SaaS Providers

The below table shows some popular SaaS providers and services that are
provided by them -

Provider Services

Salseforce.co On-demand CRM solutions

m

Microsoft Online office suite

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Office 365

Google Apps Gmail, Google Calendar, Docs, and sites

NetSuite ERP, accounting, order management, CRM, Professionals

Services Automation (PSA), and e-commerce
applications.

GoToMeeting Online meeting and video-conferencing software

Constant E-mail marketing, online survey, and event marketing

Contact

Oracle CRM CRM applications

Workday, Inc Human capital management, payroll, and financial

management.

Deployment Models: Types of cloud - Public cloud

- Private cloud - Hybrid cloud

In cloud computing, we have access to a shared pool of computer

resources (servers, storage, programs, and so on) in the cloud. You
simply need to request additional resources when you require them.

Getting resources up and running quickly is a breeze thanks to the

clouds. It is possible to release resources that are no longer
necessary. This method allows you to just pay for what you use.

Your cloud provider is in charge of all upkeep. It functions as a

virtual computing environment with a deployment architecture
that varies depending on the amount of data you want to store and
who has access to the infrastructure.

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Deployment Models

The cloud deployment model identifies the specific type of cloud

environment based on ownership, scale, and access, as well as
the cloud’s nature and purpose.

The location of the servers you’re utilizing and who controls

them are defined by a cloud deployment model.

It specifies how your cloud infrastructure will look, what you can
change, and whether you will be given services or will have to
create everything yourself. Relationships between the
infrastructure and your users are also defined by cloud
deployment types.

Different types of cloud computing deployment models are:

 Public cloud
 Private cloud
 Hybrid cloud
 Community cloud
 Multi-cloud

Public Cloud:

 The public cloud makes it possible for anybody to access

systems and services.
 The public cloud may be less secure as it is open to everyone.
 The public cloud is one in which cloud infrastructure services are
provided over the internet to the general people or major
industry groups.
 The infrastructure in this cloud model is owned by the entity
that delivers the cloud services, not by the consumer.
 It is a type of cloud hosting that allows customers and users to
easily access systems and services.
 This form of cloud computing is an excellent example of cloud
hosting, in which service providers supply services to a variety
of customers.
 In this arrangement, storage backup and retrieval services are
given for free, as a subscription, or on a per-user basis.
Example: Google App Engine etc.
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Advantages of Public Cloud Model:

 Minimal Investment: Because it is a pay-per-use service,

there is no substantial upfront fee, making it excellent for
enterprises that require immediate access to resources.
 No setup cost: The entire infrastructure is fully
subsidized by the cloud service providers, thus there is no
need to set up any hardware.

 Infrastructure Management is not required: Using the

public cloud does not necessitate infrastructure management.
 No maintenance: The maintenance work is done by the
service provider (Not users).
 Dynamic Scalability: To fulfill your company’s needs, on-
demand resources are accessible.

Disadvantages of Public Cloud Model:

 Less secure: Public cloud is less secure as resources are public

so there is no guarantee of high-level security.

 Low customization: It is accessed by many public so it can’t

be customized according to personal requirements.

Private Cloud

 The private cloud deployment model is the exact opposite of the

public cloud deployment model. It’s a one-on-one environment
for a single user (customer). There is no need to share your
hardware with anyone else.
 The distinction between private and public clouds is in how you
handle all of the hardware. It is also called the “internal cloud” &
it refers to the ability to access systems and services within a
given border or organization.
 The cloud platform is implemented in a cloud-based secure
environment that is protected by powerful firewalls and under
the supervision of an organization’s IT department. The
private cloud gives greater flexibility of control over cloud
resources.

Advantages of Private Cloud Model:

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  Better Control: You are the sole owner of the property. You
gain complete command over service integration, IT operations,
policies, and user behavior.
 Data Security and Privacy: It’s suitable for storing corporate
information to which only authorized staff have access. By
segmenting resources within the same infrastructure,
improved access and security can be achieved.
 Supports Legacy Systems: This approach is designed to work
with legacy systems that are unable to access the public
cloud.
 Customization: Unlike a public cloud deployment, a private
cloud allows a company to tailor its solution to meet its
specific needs.

Disadvantages of Private Cloud Model:

 Less scalable: Private clouds are scaled within a certain range

as there is less number of clients.
 Costly: Private clouds are more costly as they provide
personalized facilities.

Hybrid Cloud

 By bridging the public and private worlds with a layer of

proprietary software, hybrid cloud computing gives the best of both
worlds.
 With a hybrid solution, you may host the app in a safe
environment while taking advantage of the public cloud’s cost
savings.
 Organizations can move data and applications between
different clouds using a combination of two or more cloud
deployment methods, depending on their needs.

Advantages of Hybrid Cloud Model:

 Flexibility and control: Businesses with more flexibility can

design personalized solutions that meet their particular needs.
 Cost: Because public clouds provide scalability, you’ll only be
responsible for paying for the extra capacity if you require it.
 Security: Because data is properly separated, the chances of
data theft by attackers are considerably reduced.
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Disadvantages of Hybrid Cloud Model:

 Difficult to manage: Hybrid clouds are difficult to manage as it

is a combination of both public and private cloud. So, it is
complex.
 Slow data transmission: Data transmission in the hybrid
cloud takes place through the public cloud so latency occurs.

Community Cloud

It allows systems and services to be accessible by a group

of organizations. It is a distributed system that is created by
integrating the services of different clouds to address the specific
needs of a community, industry, or business.

The infrastructure of the community could be shared

between the organization which has shared concerns or tasks. It is
generally managed by a third party or by the combination of one or
more organizations in the community.

Advantages of Community Cloud Model:

 Cost Effective: It is cost-effective because the cloud is shared

by multiple organizations or communities.
 Security: Community cloud provides better security.
 Shared resources: It allows you to share resources,
infrastructure, etc. with multiple organizations.
 Collaboration and data sharing: It is suitable for both
collaboration and data sharing.

Disadvantages of Community Cloud Model:

 Limited Scalability: Community cloud is relatively less

scalable as many organizations share the same resources
according to their collaborative interests.
 Rigid in customization: As the data and resources are
shared among different organizations according to their mutual
interests if an organization wants some changes according to
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 their needs they cannot do so because it will have an impact
on other organizations.

Service level agreements

A Service Level Agreement (SLA) is the bond for performance

negotiated between the cloud services provider and the client.

Earlier, in cloud computing all Service Level Agreements were negotiated

between a client and the service consumer.

Nowadays, with the initiation of large utility-like cloud computing

providers, most Service Level Agreements are standardized until a
client becomes a large consumer of cloud services. Service level
agreements are also defined at different levels which are mentioned
below:

● Customer-based SLA
● Service-based SLA
● Multilevel SLA

Few Service Level Agreements are enforceable as contracts, but

mostly are agreements or contracts which are more along the lines of an
Operating Level Agreement (OLA) and may not have the restriction
of law. It is fine to have an attorney review the documents before making
a major agreement to the cloud service provider.

Service Level Agreements usually specify some parameters which are

mentioned below:

1. Availability of the Service (uptime)

2. Latency or the response time
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 3. Service components reliability
4. Each party accountability
5. Warranties

In any case, if a cloud service provider fails to meet the stated

targets of minimums then the provider has to pay the penalty to
the cloud service consumer as per the agreement.

So, Service Level Agreements are like insurance policies in which the
corporation has to pay as per the agreements if any casualty occurs.

Microsoft publishes the Service Level Agreements linked with the

Windows Azure Platform components, which is demonstrative of industry
practice for cloud service vendors. Each individual component has its own
Service Level Agreements.

Below are two major Service Level Agreements (SLA) described:

1. Windows Azure SLA – Window Azure has different SLA’s for

compute and storage.
 For compute, there is a guarantee that when a client deploys
two or more role instances in separate fault and upgrade
domains, client’s internet facing roles will have external
connectivity minimum 99.95% of the time.
 Moreover, all of the role instances of the client are
monitored and there is guarantee of detection 99.9% of the
time when a role instance’s process is not runs and
initiates properly.
2. SQL Azure SLA – SQL Azure clients will have connectivity
between the database and internet gateway of SQL Azure.

 SQL Azure will handle a “Monthly Availability” of 99.9%

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 within a month. Monthly Availability Proportion for a
particular tenant database is the ratio of the time the
database was available to customers to the total time in a
month.

 Time is measured in some intervals of minutes in a 30-day

monthly cycle. Availability is always remunerated for a
complete month. A portion of time is marked as unavailable
if the customer’s attempts to connect to a database are denied
by the SQL Azure gateway.

 Service Level Agreements are based on the usage model.

Frequently, cloud providers charge their pay-as-per-use
resources at a premium and deploy standards Service Level
Agreements only for that purpose.

 Clients can also subscribe at different levels that guarantees

access to a particular amount of purchased resources.

 The Service Level Agreements (SLAs) attached to a subscription

many times offer various terms and conditions. If client requires
access to a particular level of resources, then the client need
to subscribe to a service. A usage model may not deliver that
level of access under peak load condition.

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SLA Lifecycle

Steps in SLA Lifecycle

1. Discover service provider: This step involves identifying a

service provider that can meet the needs of the organization and
has the capability to provide the required service. This can be
done through research, requesting proposals, or reaching
out to vendors.
2. Define SLA: In this step, the service level requirements are
defined and agreed upon between the service provider and
the organization. This includes defining the service level
objectives, metrics, and targets that will be used to measure the
performance of the service provider.

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 3. Establish Agreement: After the service level requirements
have been defined, an agreement is established between the
organization and the service provider outlining the terms
and conditions of the service. This agreement should include
the SLA, any penalties for non-compliance, and the process for
monitoring and reporting on the service level objectives.
4. Monitor SLA violation: This step involves regularly
monitoring the service level objectives to ensure that the
service provider is meeting their commitments. If any
violations are identified, they should be reported and
addressed in a timely manner.
5. Terminate SLA: If the service provider is unable to meet
the service level objectives, or if the organization is not
satisfied with the service provided, the SLA can be terminated.
This can be done through mutual agreement or through the
enforcement of penalties for non-compliance.
6. Enforce penalties for SLA Violation: If the service provider is
found to be in violation of the SLA, penalties can be imposed
as outlined in the agreement. These penalties can include
financial penalties, reduced service level objectives, or
termination of the agreement.

Advantages of SLA

1. Improved communication: A better framework for

communication between the service provider and the client is
established through SLAs, which explicitly outline the degree of
service that a customer may anticipate. This can make sure that
everyone is talking about the same things when it comes to
service expectations.

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 2. Increased accountability: SLAs give customers a way to hold
service providers accountable if their services fall short of the
agreed-upon standard. They also hold service providers
responsible for delivering a specific level of service.
3. Better alignment with business goals: SLAs make sure that
the service being given is in line with the goals of the client by
laying down the performance goals and service level
requirements that the service provider must satisfy.
4. Reduced downtime: SLAs can help to limit the effects of
service disruptions by creating explicit protocols for issue
management and resolution.
5. Better cost management: By specifying the level of service
that the customer can anticipate and providing a way to track
and evaluate performance, SLAs can help to limit costs. Making
sure the consumer is getting the best value for their money can
be made easier by doing this.

Disadvantages of SLA

1. Complexity: SLAs can be complex to create and maintain, and

may require significant resources to implement and enforce.
2. Rigidity: SLAs can be rigid and may not be flexible enough to
accommodate changing business needs or service requirements.
3. Limited service options: SLAs can limit the service options
available to the customer, as the service provider may only be
able to offer the specific services outlined in the agreement.
4. Misaligned incentives: SLAs may misalign incentives between
the service provider and the customer, as the provider may focus
on meeting the agreed-upon service levels rather than on
providing the best service possible.
5. Limited liability: SLAs are not legal binding contracts and often

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 limited the liability of the service provider in case of service
failure.

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