11-10-2012, 05:14 PM
CS1302 COMPUTER NETWORKS
CS1302_COMPUTER_NETWORKS_complete-notes_001.doc (Size: 4.03 MB / Downloads: 70)
Need for Computer Communication over Distances
Computer communication has become essential for the following reasons:
(a) Computers can send data at a very fast speed over long distances using satellite and microwave links. Therefore, the cost of transfer of documents using computers is cheaper than
other conventional means like telegrams.
(b) Computers can have fax system integrated with them. This allows them to send pictures along with the text. Thus the newspaper reports can be prepared and sent all over the world at a very high speed by composing and publishing them from different centers.
© The time taken to transmit the messages is very small. Hence different computers can be
connected together and the users can work together as a group. Software packages have
been developed for group working in Data Base Management (DBMS) and graphic works.
(d) Different departments of an organization may be separated physically being at distant places
but their data could be stored on a central computer. This data is accessed by computers
located in different departments. The data at the central computer may be updated from time to time and accessed by all users. This prevents any bottlenecks in the smooth functioning of the organization. The latest data (say for inventory) will be easily available at all times to all the users.
(e) Fluctuations of prices in foreign exchange and shares/equities can be communicated instantaneously
using the medium of computer communications only. The transfer can be accelerated and verified at any instant of time.
Data Communication:
Data Communication is defined as the exchange of data between two devices via some form of transmission medium such as a wire cable. The communicating devices must be a part of a communication system made up of a combination of hardware ( physical equipment) and software (programs).
The three primary categories are of network are Local Area Network (LAN), Metropolitan Area Network (MAN), and Wide Area Network(WAN). The category into which a network fall is determined by its size, ownership, the distance it covers and its physical architecture.
LAN
• A LAN is usually privately owned and links the devices in a single office, building or campus.
• A LAN can be as simple as two PCs or it can extend throughout a company. LAN size is limited to a few kilometers. The most widely used LAN system is the Ethernet system developed by the Xerox Corporation.
• It is designed to allow resources (hardware , software or data) to be shared between PC’s or workstations. It may be used to provide a (shared) access to remote organizations through a router connected to a Metropolitan Area Network (MAN) or a Wide Area Network (WAN).
• One of the computers may be given a large capacity disk drive and may become a server to other clients. Software can be stored on this server and used by the whole group.
• The size of the LAN may be determined by the licensing restrictions on the numbers per copy of software. or the number of users licensed to access the operating system.
• Also differentiated from other types of network by transmission media and topology.