Data communications refers to 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,,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. For example, let us assume that video packets are sent every
30ms. If some of the packets arrive with 30ms delay and others with 40ms delay, an uneven
quality in the video is the result.
Components of a data communications system
A data communications system has five components:
Message: The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
Receiver: The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
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.
Protocol: A protocol is a set of rules that govern data communications. It represents an
agreement between the communicating devices. Without a protocol, two devices may be
connected but not communicating, just as a person speaking French cannot be understood by a
person who speaks only Japanese.
fig: model of data communication system
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,,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. For example, let us assume that video packets are sent every
30ms. If some of the packets arrive with 30ms delay and others with 40ms delay, an uneven
quality in the video is the result.
Components of a data communications system
A data communications system has five components:
Message: The message is the information (data) to be communicated. Popular forms of
information include text, numbers, pictures, audio, and video.
Sender: The sender is the device that sends the data message. It can be a computer,
workstation, telephone handset, video camera, and so on.Receiver: The receiver is the device that receives the message. It can be a computer,
workstation, telephone handset, television, and so on.
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.
Protocol: A protocol is a set of rules that govern data communications. It represents an
agreement between the communicating devices. Without a protocol, two devices may be
connected but not communicating, just as a person speaking French cannot be understood by a
person who speaks only Japanese.
fig: model of data communication system
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