CA/U4 Topic 1 Data Communication Concepts
Data communications (DC) is the process of using computing and communication technologies to transfer data from one place to another, and vice versa. It enables the movement of electronic or digital data between two or more nodes, regardless of geographical location, technological medium or data contents.
Data communications incorporates several techniques and technologies with the primary objective of enabling any form of electronic communication. These technologies include telecommunications, computer networking and radio/satellite communication. Data communication usually requires existence of a transportation or communication medium between the nodes wanting to communicate with each other, such as copper wire, fiber optic cables or wireless signals.
For example, a common example of data communications is a computer connected to the Internet via a Wi-Fi connection, which uses a wireless medium to send and receive data from one or more remote servers.
Some devices/technologies used in data communications are known as data communication equipment (DCE) and data terminal equipment (DTE). DCE is used at the sending node, and DTE is used at the receiving node.
Components of data communication system
A Communication system has following components:
It is the information or data to be communicated. It can consist of text, numbers, pictures, sound or video or any combination of these.
It is the device/computer that generates and sends that message.
It is the device or computer that receives the message. The location of receiver computer is generally different from the sender computer. The distance between sender and receiver depends upon the types of network used in between.
It is the channel or physical path through which the message is carried from sender to the receiver. The medium can be wired like twisted pair wire, coaxial cable, fiber-optic cable or wireless like laser, radio waves, and microwaves.
It is a set of rules that govern the communication between the devices. Both sender and receiver follow same protocols to communicate with each other.
The effectiveness depends on four fundamental characteristics of data communications
- Delivery: The data must be deliver in correct order with correct destination.
- Accuracy: The data must be deliver accurately.
- Timeliness: The data must be deliver in a timely manner.late delivered Data useless.
- Jitter: It is the uneven delay in the packet arrival time that cause uneven quality.
A protocol performs the following functions:
- Data sequencing
It refers to breaking a long message into smaller packets of fixed size. Data sequencing rules define the method of numbering packets to detect loss or duplication of packets, and to correctly identify packets, which belong to same message.
- Data routing
Data routing defines the most efficient path between the source and destination.
- Data formatting
Data formatting rules define which group of bits or characters within packet constitute data, control, addressing, or other information.
- Flow control
A communication protocol also prevents a fast sender from overwhelming a slow receiver. It ensures resource sharing and protection against traffic congestion by regulating the flow of data on communication lines.
- Error control
These rules are designed to detect errors in messages and to ensure transmission of correct messages. The most common method is to retransmit erroneous message block. In such a case, a block having error is discarded by the receiver and is retransmitted by the sender.
- Precedence and order of transmission
These rules ensure that all the nodes get a chance to use the communication lines and other resources of the network based on the priorities assigned to them.
- Connection establishment and termination
These rules define how connections are established, maintained and terminated when two nodes of a network want to communicate with each other.
- Data security
Providing data security and privacy is also built into most communication software packages. It prevents access of data by unauthorized users.
- Log information
Several communication software are designed to develop log information, which consists of all jobs and data communications tasks that have taken place. Such information may be used for charging the users of the network based on their usage of the network resources.