Cloud infrastructure consists of networking, servers, storage, and virtualization components. Networking infrastructure includes physical wiring and routers maintained by third parties to ensure availability. Servers provide services like web hosting, file storage, and email over protocols like HTTP. Storage services allow offsite data management with providers like AWS S3 and Google Cloud Storage. Virtualization abstracts hardware resources, making computing and storage easier to access and scale.

1. Network
Cloud resources are typically delivered to users over the internet, so there is a need for
third-party service providers to build and maintain the networking infrastructure that makes
this possible. This infrastructure includes physical wiring, switches, load balancers and
routers that help ensure cloud infrastructure is always available for customers when
needed.
Servers
A server is simply a computer or device that has been programmed to provide a service to a
customer or user. There are web servers that serve HTML or PHP files using the HTTP
protocol, file servers that store large volumes of information, mail servers that send e-mail
over the internet and several other types. In private cloud deployments, organizations may
use dedicated servers to store information, while public cloud providers use the multi-
tenant model and may use the same server to provide services for more than one customer.
Storage
Cloud storage services allow organizations to store and manage data on off-site file servers
instead of building their own physical data centers. Third-party cloud storage providers like
Amazon Simple Storage Service (S3), Microsoft Azure and Google Cloud Storage can manage
and maintain data along with remote back-ups. Data that is stored in the cloud can be
accessed via the internet or queried by other applications that are deployed in the cloud.
Cold data (data that is not actively being used) can also be stored in cloud infrastructure.
Virtualization
Virtualization may be the most important aspect of cloud infrastructure. Virtualization
software abstracts the available data storage and computing power away from the actual
hardware, enabling users to interact with their cloud infrastructure through a graphical user
interface. Computing resources and data storage are often virtualized in cloud computing,
making it easier for users to leverage these resources with added simplicity and less waste.

2. Public Cloud Private Cloud
Cloud Computing infrastructure shared to public by
service provider over the internet. It supports
multiple customers i.e, enterprises.
Cloud Computing infrastructure
shared to private organisation by
service provider over the internet.
It supports one enterprise.
Multi-Tenancy i.e, Data of many enterprise are
stored in shared environment but are isolated. Data
is shared as per rule, permission and security.
Single Tenancy i.e, Data of single
enterprise is stored.
Cloud service provider provides all the possible
services and hardware as the user-base is world.
Different people and organization may need
different services and hardware. Services provided
must be versatile.
Specific hardware and hardware as
per need of enterprise are available
in private cloud.
It is hosted at Service Provider site.
It is hosted at Service Provider site
or enterprise.
It is connected to the public internet.
It only supports connectivity over
the private network.
Scalability is very high, and reliability is moderate.
Scalability is limited, and reliability
is very high.
Cloud service provider manages cloud and
customers use them.
Managed and used by single
enterprise.
It is cheaper than private cloud. It is costlier than public cloud.
Security matters and dependent on service
provider. It gives high class of security.
Performance is low to medium. Performance is high.
It has shared servers. It has dedicated servers.
Example : Amazon web service (AWS) and Google
AppEngine etc.
Example : Microsoft KVM, HP, Red
Hat & VMWare etc.

3. 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 -
o Accessible to various users via the same development application.
o Integrates with web services and databases.
o Builds on virtualization technology, so resources can easily be scaled up or down as
per the organization's need.
o Support multiple languages and frameworks.
o 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.
Software as a Service (SaaS)
SaaS is also known as "on-demand software". It is a software in which the applications are
hosted by a cloud service provider. Users can access these applications with the help of
internet connection and web browser.
Characteristics of SaaS
There are the following characteristics of SaaS -
o Managed from a central location
o Hosted on a remote server
o Accessible over the internet
o Users are not responsible for hardware and software updates. Updates are applied
automatically.
o The services are purchased on the pay-as-per-use basis
Example: BigCommerce, Google Apps, Salesforce, Dropbox, ZenDesk, Cisco WebEx,
ZenDesk, Slack, and GoToMeeting.