LECTURE 2

Dear students and readers in last lecture we studied about the introduction of cloud and cloud computing ,in lecture 2 we try to understand it more simply-


"Cloud Computing refers to the computing on internet as opposed to computing on a desktop."

So cloud computing just means Web-based software, right? Well,no. Truth be told, a lot of major software vendors are saying “We do cloud computing too!” simply because their software works over the Internet.

Web-enabled software is wonderful and very useful - but it has also been around for a long time. It’s nothing new in itself.

In reality, cloud computing encompasses other forms of computing beyond software, including the underlying hardware (infrastructure) and platforms. In many ways, cloud computing is strikingly similar to desktop computing in that it encompasses the same three basic elements: hardware

(infrastructure), operating systems (platforms), and software. 

The main difference is that, with cloud computing, all three elements are "rented" over the Internet, rather than being managed locally.

Let’s take a closer look at the definition above:

“…computing on the Internet, as opposed to computing on a desktop.”

What does it mean to say "computing on the Internet"? We simply mean that you can log onto a website to do whatever you might normally do on a PC or local server. For example, you can “rent” and manage all your hardware over the Internet, configure computing environments and/or run software. 
Cloud computing lets us do all of our computing on the Internet as a viable alternative to buying, installing, upgrading, uploading, downloading, backing up and otherwise managing physical hardware, operating systems and software. It doesn’t require a big upfront investment, because you “rent” only what you need, and as much as you need. With cloud computing, your PC is mainly used as a way to run a Web browser. The actual processing and computing is done by remote servers (or virtual servers) and software that may be scattered across the Internet, thus the word “cloud.”

DEFINITIONS OF CLOUD COMPUTING

There are many definitions of CC given by cloud experts and organizations, such as the following:

“George Reese”- "Cloud is where you go to use technology when you need it, for as long as you need it, and not a minute more." There is no installation being done in the desktop and payment for the technology is not made when it is not in use.

“451 Group”- The cloud is IT as a service, delivered by IT resources that are independent of location.

“Gartner”- Cloud computing is a style of computing where massively scalable IT-related capabilities are provided as a service across the Internet to multiple external customers.

“IBM” - A cloud computing platform dynamically provides, configures, reconfigures, and deprivations servers as needed. Cloud applications use large data centers and powerful servers that host web applications and web services. 

NIST DEFINITION OF CLOUD COMPUTING 

Cloud computing is a model for enabling 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 promotes availability and is composed of five essential characteristics, three service models, and four deployment models.

Let’s go with the definition and understand first the,

CHARACTERISTICS OF CLOUD COMPUTING                 

• On-demand self-service: On-demand self service means that customers (usually organizations) can demand and control their own computing resources. Computer services such as email, applications, network or server service can be provided without requiring human interaction with each service provider. Cloud service providers providing on demand self services include Amazon Web Services (AWS), Microsoft, Google, IBM and Salesforce.com. New York Times and NASDAQ are examples of companies using AWS (NIST). Gartner describes this characteristic as service based.
• Broad network access: Broad network access allows services to be offered over the Internet or private networks. Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, laptops, and PDAs).
• Location independent resource pooling: Pooled resources means that customers draw from a pool of computing resources, usually in remote data centres. The customer generally has no control or knowledge over the exact location of the provided resources. Services can be scaled larger or smaller; and use of a service is measured and customers are billed accordingly.
• Rapid elasticity: Capabilities can be rapidly and elastically provisioned to quickly scale up and rapidly released to quickly scale down. To the consumer, the capabilities available for rent often appear to be infinite and can be purchased in any quantity at any time.
• Pay per use: Capabilities are charged using a metered, fee-for-service, or advertising based billing model to promote optimization of resource use. Examples are measuring the storage, bandwidth, and computing resources consumed and charging for the number of active user accounts per month. Clouds within an organization accrue cost between business units and may or may not use actual currency.