It is the process of managing the rate of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred. Error control
It is the process of detecting and correcting both the bit level and packet level errors. The network is responsible for transmission of data from one device to another device. The end to end transfer of data from a transmitting application to a receiving application involves many steps, each subject to error. With the error control process, we can be confident that the transmitted and received data are identical. Data can be corrupted during transmission. For reliable communication, error must be detected and corrected. b.
Description of the following errors in data communication i.
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals. ii.
Cross talk is a noise that is caused by the inductive coupling between two wires that are closed to each other. Sometime when talking on the telephone, you can hear another conversation in the background. That is cross talk
It is the loss of energy as the signal propagates outward. The amount of energy depends on the frequency. If the attenuation is too much, the receiver may not be able to detect the signal at all, or the signal may fall below the noise level. For reliable communication, the attenuation and delay over the range of frequencies of transmission should be constant.. iv.
Like cross-talk, it is formed when conflicting data communications are merged together. However, echo is usually from a single transmission line where multiple computer ports are sending data communications through at once. Someone's data communication would echo into another's, resulting in a corruption of data.
The movement of digital data from one location to another can result in transmission errors, the receiver not receiving the same signal as transmitted by the transmitter as a result of electrical noise in the transmission process. Sometimes a noise pulse may be large enough to alter the logic level of the signal. For example, the transmitted sequence 1001 may be incorrectly received as 1101. In order to detect such errors a parity bit is often used. A parity bit is an extra 0 or 1 bit attached to a code group at transmission. In the even parity method the value of the bit is chosen so that the total number of 1s in the code group, including the parity bit, is an even number. For example, in transmitting 1001 the parity bit used would be 0 to give 01001, and thus an even number of 1s. In transmitting 1101 the parity bit used would be 1 to give 11101, and thus an even number of 1s. With odd parity the parity bit is chosen so that the total number of 1s, including the parity bit, is odd. Thus if at the receiver the number of 1s in a code group does not give the required parity, the receiver will know that there is an error and can request that the code group be retransmitted.
A checksum is a simple type of redundancy check that is used to detect errors in data. Errors frequently occur in data when it is written to a disk, transmitted across a network or otherwise manipulated. The errors are typically very small, for example, a single incorrect bit, but even such small errors can greatly affect the quality of data, and even make it useless. In its simplest form, a checksum is created by...
References: 1. Types of Errors in Data Communication | eHow.com http://www.ehow.com/info_8769397_types-errors-data-communication.html#ixzz2LASvEanG
2. W. Bolton, Mechatronics: Electronic Control Systems in Mechanical and Electrical Engineering (2nd Edition), Longman, New York, 1999.
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