Physical Model

A physical model represents the underlying hardware elements of a distributed system. It encompasses the hardware composition of a distributed system in terms of computers and other devices and their interconnections. It is primarily used to design, manage, implement, and determine the performance of a distributed system.

A physical model majorly consists of the following components:

1. Nodes

Nodes are the end devices that can process data, execute tasks, and communicate with the other nodes. These end devices are generally the computers at the user end or can be servers, workstations, etc.

• Nodes provision the distributed system with an interface in the presentation layer that enables the user to interact with other back-end devices, or nodes, that can be used for storage and database services, processing, web browsing, etc.
• Each node has an Operating System, execution environment, and different middleware requirements that facilitate communication and other vital tasks.,

2. Links

Links are the communication channels between different nodes and intermediate devices. These may be wired or wireless. Wired links or physical media are implemented using copper wires, fiber optic cables, etc. The choice of the medium depends on the environmental conditions and the requirements. Generally, physical links are required for high-performance and real-time computing. Different connection types that can be implemented are as follows:

• Point-to-point links: Establish a connection and allow data transfer between only two nodes.
• Broadcast links: It enables a single node to transmit data to multiple nodes simultaneously.
• Multi-Access links: Multiple nodes share the same communication channel to transfer data. Requires protocols to avoid interference while transmission.

3. Middleware

These are the softwares installed and executed on the nodes. By running middleware on each node, the distributed computing system achieves a decentralised control and decision-making. It handles various tasks like communication with other nodes, resource management, fault tolerance, synchronisation of different nodes and security to prevent malicious and unauthorised access.

4. Network Topology

This defines the arrangement of nodes and links in the distributed computing system. The most common network topologies that are implemented are bus, star, mesh, ring or hybrid. Choice of topology is done by determining the exact use cases and the requirements.

5. Communication Protocols

Communication protocols are the set rules and procedures for transmitting data from in the links. Examples of these protocols include TCP, UDP, HTTPS, MQTT etc. These allow the nodes to communicate and interpret the data.

Distributed computing is a system where processing and data storage is distributed across multiple devices or systems, rather than handled by a single central device. In this article, we will see Distributed Computing System Models.