Introduction to Data Communication
Data communication is the exchange of data between two devices via a transmission medium such as a wire cable or wireless signal. For communication to occur, the devices must be part of a system made up of hardware and software. The effectiveness of a data communication system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter.
Components of Data Communication
A data communication system has five components. The message is the information to be communicated (text, numbers, images, audio, video). The sender is the device that sends the message. The receiver is the device that receives the message. The transmission medium is the physical path by which a message travels. The protocol is a set of rules governing data communication.
Data Flow
Communication between two devices can be simplex (one direction only, like a keyboard to monitor), half-duplex (both directions but not simultaneously, like walkie-talkies), or full-duplex (both directions simultaneously, like a telephone). Full-duplex doubles the capacity of a link.
Networks
A network is a set of devices (nodes) connected by communication links. A node can be a computer, printer, or any device capable of sending or receiving data. Networks are evaluated by performance (throughput, delay), reliability (frequency of failure, recovery time), and security.
Network Criteria and Types
Networks are categorised by size: LAN (Local Area Network) covers a building or campus, MAN (Metropolitan Area Network) spans a city, and WAN (Wide Area Network) covers countries or continents. A PAN (Personal Area Network) connects devices within an individual's workspace.
Network Topologies
Topology refers to how devices are connected. Bus topology uses a single backbone cable. Star topology connects each device to a central hub. Ring topology connects devices in a closed loop. Mesh topology provides dedicated point-to-point links between every pair of devices. Hybrid topologies combine two or more basic topologies.
Protocols and Standards
A protocol defines what is communicated, how it is communicated, and when. Key elements include syntax (structure/format), semantics (meaning of each section), and timing (when and how fast data is sent). Standards ensure interoperability; they are set by bodies like ISO, IEEE, ITU, and IETF.
The OSI Model
The OSI (Open Systems Interconnection) model is a seven-layer framework: Physical, Data Link, Network, Transport, Session, Presentation, and Application. Each layer has specific functions and communicates with its peer layer on the remote device through protocols while serving the layer above and using services of the layer below.
The TCP/IP Model
The TCP/IP model is a practical four-layer suite: Network Interface, Internet, Transport, and Application. It was developed before the OSI model and is the basis of the Internet. TCP provides reliable delivery; IP provides addressing and routing.
Summary
Data communication encompasses the components, flow modes, network types, topologies, protocols, and layered models that underpin all modern networking. Understanding these foundations is essential for studying advanced networking topics.