DISTRIBUTED SYSTEMS

Distributed systems & Distributed computing

A distributed system is a network that consists of autonomous computers that are connected using a distribution middleware. They help in sharing different resources and capabilities to provide users with a single and integrated coherent network.

Distributed computing also refers to the use of distributed systems to solve computational problems. In distributed computing, a problem is divided into many tasks, each of which is solved by one or more computers, which communicate with each other via message passing.

Standalone systems vs Distributed systems

Example for standalone systems: A fax machine is a stand-alone device because it does not require a computer, printer, modem, or other device. A printer, on the other hand, is not a stand-alone device because it requires a computer to feed it data.

Example for distributed systems:
Intranets, Internet, WWW, email.
Telecommunication networks: Telephone networks and Cellular networks.
Network of branch office computers -Information system to handle automatic processing of orders,
Real-time process control: Aircraft control systems,
Electronic banking,
Airline reservation systems,
Sensor networks,
Mobile and Pervasive Computing systems.

Elements of distributed systems

The elements of a distribution system include distribution mains, arterial mains, storage reservoirs, and system accessories (including booster stations, valves, hydrants, main-line meters, service connections, and backflow preventers).

• Distribution mains are the pipelines that make up the distribution system. Their function is to carry water from the water source or treatment works to users.

• Arterial mains are large-size distribution mains. They are interconnected with smaller distribution mains to form a complete gridiron system.

• Storage reservoirs are structured to store water. They may serve to equalize the supply or pressure in the distribution system.

• System accessories include the following:

• Booster stations that pump water from storage or a relatively low-pressure main to the distribution system, or it may serve a portion of the system that is at a higher elevation.

• Valves that serve to control the flow of water in the distribution system by isolating areas for repair or by regulating system flow or pressure.

• Hydrants that are designed to allow water from the distribution system to be used for fire-fighting purposes.

• Main-line meters that serve to record the flow of water in a part of the distribution system.

• Service connections that connect either an individual building or other plumbing system to the distribution-system mains.

• Backflow preventers that protect the water source from contamination.

Different types of services, which can be gained from distributed systems

There are various types of services, which can be gained from distributed systems

Mail service - SMTP, POP3, IMAP  

File transferring and sharing - FTP  

Remote logging - telnet  

Games and multimedia - RTP, SIP, H.26x  

Web – HTTP 

Types of Web-based Systems

• Web sites

• Web applications

• Web services and client apps

• Rich Internet Applications (RIAs)/Rich Webbased Applications (RiWAs)