Data communications & networking

DATA COMMUNICATIONS AND NETWORKING

Data Communication:

When we communicate, we are sharing information. This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance. The term telecommunication, which includes telephony, telegraphy and television, means communication at a distance.

The word data refers to facts, concepts and instructions presented in whatever form is agreed upon by the parties creating and using data. In the context of computer information systems, data are presented by binary information units produced and consumed in the form of 0’s and 1’s.

Data communication is the exchange of data between two devices and some form of transmission medium. Data communication is considered local if the communicating devices are in the same building or a
Similarly restricted geographical area, and is considered remote if the devices are farther apart.

For Data communication to occur, the communicating devices must be part of a communication system made up of a combination of hardware and software. The effectiveness of a data communication system depends on three fundamental characteristics:

Delivery: The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.

Accuracy: The system must deliver data accurately. Data that have been altered in transmission and left uncorrected are unusable.

Timeliness: The system must deliver data in a timely manner. In case of video, audio and voice data, timely delivery means delivering data as they are produced, in the same order that they are produced and without significant delay. This time of delivery is called real-time transmission.

Networks:

The network is the set of devices connected by media links. A node can be a computer, printer or any other devices capable of sending and receiving data generated by other nodes on the network. The links connecting the devices are often called communication channels.

Distributed processing:

Networks use distributed processing, in which a task is divided among multiple computers. Instead of a single large machines being responsible for all aspects of a process, each separate computer handles a subset.

Advantages of distributed processing include the following:

Security/Encapsulation: A system designer can limit the kinds of interactions that a given user can have with the entire system, for ex: a bank can allow users access to their own accounts through an automated teller machine (ATM) without allowing them access to the bank’s entire database.

Distributed databases: No one system needs to provide storage capacity for the entire database. For ex, the World Wide Web gives users access to information that may be actually stored and manipulated anywhere on the internet.

Faster problem solving: Multiple computers working on parts of a problem con-currently often can solve the problem faster than a single machine working alone. For ex, network of pc’s have broken encryption codes that were presumed to be unbreakable because of the amount of time it would take a single computer to crack them.

Security through redundancy: Multiple computers running the same program at the same time can provide security through redundancy. For ex: in the space shuttle three computers run the same program so that if one has a hardware error, the other two can override it.

Collaborative processing: Both multiple computers & multiple users may interact on the task. For ex: in multiple user network games, the actions of each player are visible to and affect all the others.