Computer Network Models

In the past couple of decades implementing the software for subsystems was based on a single, complex, unstructured program with many interacting components. Therefore software was very difficult to test and modify. To overcome such problems, the International Organization of Standardization(ISO) has started various network schemes in other words Computer Network Models. In layered principles, the networking concept is divided into several layers, and each layer is given a particular task.

Layered Architecture

• The main aim of layered architecture is to divide the model into small parts.
• Every lower layer adds its services to the higher layer to provide a full set of services.
• It provides modularity and clarity between interfaces, i.e., provides interaction between each subsystem.
• It ensures independence with each layer by providing services from lower to higher layers. Therefore, any modification in a layer will not affect the other corresponding layers.
• The number of layers, functions, contents of each layer will vary from network to network. Each layer is to provide the service from lower to a higher layer.
• Hide the details from the layers, the services are implemented.
• The basic elements of layered architecture are services, protocols, and interfaces.
  • Service: It allocates actions that a layer provides to the higher layer.
  • Protocol: It defines a set of rules that a layer uses to exchange information to another layer.
  • Interface: It is a medium through which the message is transferred from one layer to another layer.

• In the case of layered architecture, no data is transferred from the layer of one machine to the layer of another machine. Instead, each layer passes the data to the layer immediately just below it, until the lowest layer is reached.
• In a layered architecture, tasks are divided into several small and manageable tasks.
• The data is passed from the upper layer to the lower layer through an interface.
• A set of layers and protocols is known as network architecture.

Why do we require Layered architecture?

• It makes a design process in such a way that the unmanageable tasks are divided into small and manageable tasks. In another word, we can say that this approach reduces the complexity of the design.
• Layered architecture is more modular. Modularity provides independence of each layer, which is easier to understand and implement.
• It ensures the independence of layers so that implementation in one layer can be changed without affecting other layers.
• Each layer of the layered architecture can be analyzed and tested individually.

The most important reference Computer Network Models are:

1. OSI reference model.

2. TCP/IP reference model.