Question

How data are shifted in computer network?

Answer 1

Data communications are the exchange of data between two devices via some form of
transmission medium such as a wire cable. For data communications to occur, the
communicating devices must be part of a communication system made up of a combination of
hardware (physical equipment) and software (programs). The effectiveness of a data
communications system depends on four fundamental characteristics: delivery, accuracy,
timeliness, and jitter.
1. 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.
2. Accuracy. The system must deliver the data accurately. Data that have been altered in
transmission and left uncorrected are unusable.
3. Timeliness. The system must deliver data in a timely manner. Data delivered late are useless.
In the case of video and audio, timely delivery means delivering data as they are produced, in the
same order that they are produced, and without significant delay. This kind of delivery is called
real-time transmission.
4. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the
delivery of audio or video packets.
Components:
A data communications system has five components.
1. Message. The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
2. Sender. The sender is the device that sends the data message. It can be a computer,
workstation, telephone handset, video camera, and so on.
3. Receiver. The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
4. Transmission medium. The transmission medium is the physical path by which a message
travels from sender to receiver. Some examples of transmission media include twisted-pair wire,
coaxial cable, fiber-optic cable, and radio waves
5. Protocol. A protocol is a set of rules that govern data communications. It represents an
agreement between the communicating devices.
DATA TRANSMISSION MODES
Communication between two devices can be simplex, half-duplex, or full-duplex.
Simplex:
In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the
two devices on a link can transmit; the other can only receive. Keyboards and traditional
monitors are examples of simplex devices. The keyboard can only introduce input; the monitor
can only accept output. The simplex mode can use the entire capacity of the channel to send data
in one direction.
Half-Duplex:
In half-duplex mode, each station can both transmit and receive, but not at the same time. When
one device is sending, the other can only receive, and vice versa. In a half-duplex transmission,
the entire capacity of a channel is taken over by whichever of the two devices is transmitting at
the time. Walkie-talkies and CB (citizens band) radios are both half-duplex systems. The half-
duplex mode is used in cases where there is no need for communication in both directions at the
same time; the entire capacity of the channel can be utilized for each direction.


Full-Duplex:
In full-duplex both stations can transmit and receive simultaneously. The full-duplex mode is
like a two way street with traffic flowing in both directions at the same time. In full-duplex
mode, signals going in one direction share the capacity of the link: with signals going in the other
direction. One common example of full-duplex communication is the telephone network. When
two people are communicating by a telephone line, both can talk and listen at the same time. The
full-duplex mode is used when communication in both directions is required all the time. The
capacity of the channel, however, must be divided between the two directions.