This document discusses cloud computing concepts including definitions, essential characteristics of abstraction and virtualization, benefits such as on-demand access and elastic resources, and how virtualization enables key attributes like scalability. It provides examples of Google, Microsoft Azure, and Amazon Web Services cloud platforms. Load balancing is described as a way to distribute requests across virtualized resources to optimize performance and avoid overloads. More advanced load balancers can monitor resource health and workload to intelligently assign tasks.

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Chapter – I
Introduction
 Essentials
 Benefits
 Business and IT Perspective
 Cloud and Virtualization
 Cloud Service Requirements
 Cloud and Dynamic Infrastructure
 Cloud Computing Characteristics
 Cloud Adoption
 Cloud Models
 Measured Service
 Security

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 Cloud Computing refers to applications
and services that run on a distributed
network using virtualized resources and
accessed by common Internet protocols
and networking standards. It is
distinguished by the notion that
resources are virtual and limitless and
that details of the physical systems on
which software runs are abstracted from
the user.

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Defining Cloud Computing
Cloud computing takes the technology,
services and applications that are similar
to those on the Internet and turns them
into a self-service utility. The use of the
word cloud makes reference to the two
essential concepts.

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Essentials
Abstraction: cloud computing abstracts the
details of system implementation from
users and developers. Applications run
on physical systems that aren’t specified,
data is stored in locations that are
unknown, administration of systems is
outsourced to others and access by users
is ubiquitous.

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Essentials
Virtualization: Cloud computing
virtualizes systems by pooling and
sharing resources. Systems and storage
can be provisioned as needed from a
centralized infrastructure, costs are
assessed on a metered basis, multi-
tenancy is enabled, and resources are
scalable with agility.

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To help clarify how cloud computing has
changed the nature of commercial system
deployment, consider these three
examples:

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Google: In the previous decade, Google
has built a worldwide network of
datacenters to service it search engine. In
doing so Google has captured a
substantial portion of the world’s
advertising revenue. That revenue has
enabled Google to offer free software to
users based on that infrastructure and
has changed the market for user-facing
software. This is the classic Software as a
Service case.

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Azure Platform: By contrast, Microsoft
is creating the Azure Platform. It enables
.NET Framework applications to run
over the Internet as an alternate platform
for Microsoft developer software running
on desktops.

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Amazon Web Services: One of the most
successful cloud-based businesses is
Amazon Web Services, which is an
Infrastructure as a Service offering that
lets you rent virtual computers on
Amazon’s own infrastructure.

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These new capabilities enable applications
to be written and deployed with minimal
expense and to be rapidly scaled and
made available worldwide as business
conditions permit. This is truly a
revolutionary change in the way
enterprise computing is created and
deployed.

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Benefits of Cloud Computing
On-demand self-service: A client can
provision computer resource without the
need for interaction with cloud-service
provider personnel.
Broad network access: Access to
resources in the cloud is available over
the network using standard methods in a
manner that provides platform-
independent access to clients of all
types.

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Benefits of Cloud Computing
Resource pooling: a cloud service provider
creates resources that are pooled together in
a system that supports multi-tenant usage.
Physical and virtual systems are dynamically
allocated or reallocated as needed. Intrinsic
in this concept of pooling is the idea of
abstraction that hides the location of
resources such vm, memory, processing,
storage, network and connectivity.

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Benefits of Cloud Computing
Rapid elasticity: Resources can be rapidly
and elastically provisioned.
The system can add resources by either
scaling up systems (more powerful
computers) or scaling out systems. From the
standpoint of client, cloud computing
resources should look limitless and can be
purchased at any time and in any quantity.

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Benefits of Cloud Computing
Measured service: The use of cloud system
resources is measured, audited and reported
to the customer based on a metered system.
A client can be charged based on a known
metric such as amount of storage used,
number of transactions, network I/O or
bandwidth, amount of processing power
used and so forth. A client is charged based
on the level of services provided.

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Advantages
• Ease of utilization
• Lower costs
• Quality of service
• Reliability
• Outsourced IT management
• Simplified maintenance and upgrade
• Lower barrier to entry

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Cloud and Virtualization
When you use cloud computing, you are accessing pooled
resources using a technique called virtualization.
Virtualization assigns a logical name for a physical
resource and then provides a pointer to that physical
resource when a request is made. Virtualization
provides a means to manage resources effectively
because the mapping of virtual resources to physical
resources can be both dynamic and facile.
Virtualization is dynamic in that the mapping can be
assigned based on rapidly changing conditions and it is
facile because changes to a mapping assignment can be
nearly instantaneous.

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These are among the different types of
virtualization that are characteristics of cloud
computing:
Access: A client can request access to a cloud service
from any location.
Application: A cloud has multiple application instances
and directs requests to an instance based on
conditions.
CPU: Computers can be partitioned into a set of virtual
machines with each machine being assigned a
workload. Alternatively, systems can be virtualized
through load-balancing technologies.
Storage: Data is stored across storage devices and often
replicated for redundancy.

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To enable these characteristics, resources must be highly
configurable and flexible. You can define the features in software
and hardware that enable this flexibility as conforming to one or
more of the following mobility patterns:
P2V: Physical to Virtual
V2V: Virtual to Virtual
V2P: Virtual to Physical
P2P: Physical to Physical
D2C: Datacenter to Cloud
C2C: Cloud to Cloud
C2D: Cloud to Datacenter
D2D: Datacenter to Datacenter

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Virtualization is a key enabler of the first four of five key attributes of
cloud computing:
Service-based: A service-based architecture is
where clients are abstracted from service providers
through service interfaces.
Scalable and elastic: Services can be altered to
affect capacity and performance on demand.
Shared services: Resources are pooled in order to
create greater efficiencies.
Metered usage: Services are billed on a usage
basis.
Internet delivery: The services provided by cloud
computing are based on Internet protocols and
formats.

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Load Balancing and Virtualization:
One characteristic of cloud computing is virtualized network
access to a service. No matter where you access the service,
you are directed to the available resources. The technology
used to distribute service requests to resources is referred to
as load balancing. Load balancing is an optimization
technique; it can be used to increase utilization and
throughput, lower latency, reduce response time and avoid
system overload.
The following network resources can be load balanced:
• Network interfaces and services such as DNS, FTP and
HTTP
• Connections through intelligent switches
• Processing through computer system assignment
• Storage resources
• Access to application instances

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Without load balancing, cloud computing would be very
difficult to manage. Load balancing provides the necessary
redundancy to make an intrinsically unreliable system
reliable through managed redirection. It also provides fault
tolerance when coupled with a failover mechanism. Load
balancing is nearly always a feature of server farms and
computer clusters and for high availability applications.
Load balancer uses:
• Round robin scheduling algorithms to handle the
service request queues.
• Session ticket to maintain subsequent related traffic
from the client that is part of that session can be
properly routed to the same resource.
• Persistent session data
• Client-side cookies.

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Advanced Load Balancing:
The more sophisticated load balancers are workload
managers. They determine the current utilization of the
resources in their pool, the response time, the work queue
length, connection latency and capacity, and other factors in
order to assign task to each resource. Among the features
you find in load balancers are polling resources for their
health, the ability to bring standby servers online, workload
weighing based on a resource’s capacity, HTTP traffic
compression, TCP offload and buffering, security and
authentication, and packet shaping using content filtering
and priority queuing.
An Application Delivery Controller (ADC) is a combination of
load balancer and application server that is a server placed
between a firewall or router and a server farm providing web
services. An ADC is assigned a virtual IP address VIP that it
maps to a pool of servers based on application specific criteria.