Distributed Systems

Introduction
A system in which hardware or software components located at networked computers communicate and coordinate their actions only by passing messages.
To understand the nature of distributed systems, we will therefore first take a
look at operating systems in relation to distributed computers. Operating systems for distributed computers can be roughly divided into two categories:

• Tightly coupled systems : The operating system essentially tries to maintain a single, global view of the resources it manages.

Loosely coupled systems : Loosely-coupled systems can be thought of as a collection of computers each running their own operating system. However, these operating systems work together to make their own services and resources available to the others.

A tightlycoupled operating system is generally referred to as a distributed operating system (DOS), and is used for managing multiprocessors and homogeneous multicomputers. Like traditional uniprocessor operating systems, the main goal of a distributed operating system is to hide the intricacies of managing the underlying hardware such that it can be shared by multiple processes.
The loosely-coupled network operating system (NOS) is used for heterogeneous multicomputer systems. Although managing the underlying hardware is an important issue for a NOS, the distinction from traditional operating systems comes from the fact local services are made available to remote clients. Network operating Systems are usually workstations and file servers on a Lan and each machine of them is autonomous.

True distributed systems is a system which is,

• Tightly coupled software on loosely coupled hardware
• Appear to users to be a single computer

Single-system image

Virtual uniprocessor

• Same kernel runs on each machine

Prime Motivation for Distributed Systems: Resource sharing

• Resource: File, database, data object, program, cpu-time, disk, memory, printer, scanner, ...
• Service: Collection of related resources, e.g. file-service, web-service, email-service, ...
• Interface: Well defined set of operators the service exports.
• Remote Invocation: Request an operation of a remote service.
• Client/server: Active and passive role in a remote invocation.

Grid Computing

Introduction

Grid computing is increasingly being viewed as the next phase of distributed computing. Built on pervasive Internet standards, grid computing enables organizations to share computing and information resources across department and organizational boundaries in a secure, highly efficient manner.

The key to realizing the benefits of grid computing is standardization, so that the diverse resources that make up a modern computing environment can be discovered, accessed, allocated, monitored, and in general managed as a single virtual system—even when provided by different vendors and/or operated by different organizations.

Definition

Grid computing is an emerging computing model that provides the ability to perform higher throughput computing by taking advantage of many networked computers to model a virtual computer architecture that is able to distribute process execution across a parallel infrastructure.

IBM says, "Grid is the ability, using a set of open standards and protocols, to gain access to applications and data, processing power, storage capacity and a vast array of other computing resources over the Internet. A Grid is a type of parallel and distributed system that enables the sharing, selection, and aggregation of resources distributed across multiple administrative domains based on the resources availability, capacity, performance, cost and users' quality-of-service requirements"

CERN, one of the largest users of Grid technology, talk of The Grid: "a service for sharing computer power and data storage capacity over the Internet."

Benefits of Grid Computing

Grid computing provides the following benefits:
· Flexibility to meet changing business needs
· Highest quality of service at the lowest cost
· Investment protection and rapid return


Wireless Application Protocol
Remote sensing Instruments
Advantages of E-commerce

Advantages of E-commerce

Electronic commerce abbreviated E-commerce “is the buying and selling of goods, services and information on the Internet, especially the World Wide Web. Sometimes used interchangeably with e-business” (whatis.com). In simple words-commerce conducted on Internet.

Advantages of E-commerce
E-commerce can drive productivity and be a source of innovation within organizations. It offers following advantages to business:

• Improved customer service: With the most basic use of e-mail a business has a fast and reliable way to communicate with suppliers or to receive and respond to customer requirements.
  
• Better business hours: Operating 24 hours and seven days is possible without the traditional overheads.
  
• Reduced inventories: With shorter, faster supply chains, physical warehousing of inventory can be reduced or even in some cases removed.
  
• An easier and cheaper way of doing business: Orders can be accepted, confirmed, processed, and increasingly, paid for in an online environment and can provide real cost reductions over telephone, fax or paper-based transactions.
  
• A new way of doing business: E-commerce creates new opportunities for innovation and value creation in all sectors of the economy.
  
• Access to worldwide markets: E-commerce is open to anyone. So business gets access to worldwide markets.
  
• Can track purchases and use data to recommend other items to the customer: Previous purchase orders can be tracked and seller can recommend new items which are coming in market to those customers and that is without much cost.

Mobile Commerce
Wireless Application Protocol
Remote sensing Instruments
Grid Computing