Layered Architecture in Computer Networks

Every network consists of a specific number of functions, layers, and tasks to perform. Layered Architecture in a computer network is defined as a model where a whole network process is divided into various smaller sub-tasks. These divided sub-tasks are then assigned to a specific layer to perform only the dedicated tasks. A single layer performs only a specific type of task. To run the application and provide all types of services to clients a lower layer adds its services to the higher layer present above it. Therefore layered architecture provides interactions between the sub-systems. If any type of modification is done in one layer it does not affect the next layer.

Layered Architecture

As shown in the above diagram, there are five different layers. Therefore, it is a five-layered architecture. Each layer performs a dedicated task. The lower-level data for example from layer 1 data is transferred to layer 2. Below all the layers Physical Medium is present. The physical medium is responsible for the actual communication to take place. For the transfer of data and communication layered architecture provides with a clean cut interface.

Features of Layered Architecture

• Use of Layered architecture in computer network provides with the feature of modularity and distinct interfaces.
• Layered architecture ensures independence between layers, by offering services to higher layers from the lower layers and without specifying how these services are implemented.
• Layered architecture segments as larger and unmanageable design into small sub tasks.
• In layer architecture every network has different number of functions, layers and content.
• In layered architecture, the physical route provides with communication which is available under the layer 1.
• In layered architecture, the implementation done by one layer can be modified by another layer.

Elements of Layered Architecture

There are three different types of elements of a layered architecture. They are described below:

• Service: Service is defined as a set of functions and tasks being provided by a lower layer to a higher layer. Each layer performs a different type of task. Therefore, actions provided by each layer are different.
• Protocol: Protocol is defined as a set rule used by the layer for exchanging and transmission of data with its peer entities. These rules can consists details regarding a type of content and their order passed from one layer to another.
• Interface: Interface is defined as a channel that allows to transmit the messages from one layer to the another.

Need of Layered Architecture

• Divide and Conquer Approach: Layered architecture supports divide and conquer approach. The unmanageable and complex task is further divided into smaller sub tasks. Each sub task is then carried out by the different layer. Therefore, using this approach reduces the complexity of the problem or design process.

• Easy to Modify: The layers are independent of each other in layered architecture. If any sudden change occurs in the implementation of one layer, it can be changed. This change does not affect the working of other layers involved in the task. Therefore, layered architectures are required to perform any sudden update or change.

• Modularity: Layered architecture is more modular as compared to other architecture models in computer network. Modularity provides with more independence between the layers and are easier to understand.

• Easy to Test: Each layer in layered architecture performs a different and dedicated task. Therefore, each layer can be analyzed and tested individually. It helps to analyze the problem and solve them more efficiently as compared to solving all the problems at a time.

Application of Layered Architecture in computer Networks

In computer networks, layered architecture is majorly used for communication. The two network models that makes use of layered architecture are:

• OSI Model
• TCP/IP Model

OSI Model

OSI stands for Open Systems Interconnection. OSI is a seven layered architecture. All these seven layers work collaboratively to transmit data from one layer to another. Below are the layers of OSI Model.

1. Physical Layer: Physical layer is the lowest layer of OSI model and is responsible for the physical connection between all the required devices. The information present in physical layer is in the form of bits. Physical layer performs various functions such as bit rate control, bit synchronization, transmission mode etc.

2. Data Link Layer: Data Link layer provides with successful delivery of message from one node to the another. It checks whether this delivery of message is error free. Other functions performed by data link layer are error control, framing, flow control etc.

3. Network Layer: Network Layer is responsible for the transmission of data from one host to another host that is connected in different network. It performs other tasks such routing and logical addressing.

4. Transport Layer: Transport Layer is defined as a layer that takes services from network layer and provides services to application layer. Other tasks performed by transport layer are service point addressing, segmentation and reassembling.

5. Session Layer: Session layer is defined as a layer that is responsible for establishing a connection, maintenance of session and to provide with security. Other functions of session Layer are to establish session, termination and synchronization.

6. Presentation Layer: The data from application layer is extracted at the presentation layer. This layer is also known as translation layer. The functions of presentation layer are encryption, decryption, compression and translation.

7. Application Layer: Application layer is the topmost layer of OSI Model. Application layer is also known as desktop layer. It provides with other functions such as directory services, mail services, network virtual terminal etc.

FAQs on Layered Architecture in Computer Networks

1. Give an example of operating system that makes use of layered architecture approach?

The Windows NT operating system is an example of operating system that makes use of layered architecture approach.

2. What is the need of layered architecture in computer network?

Layered architecture helps to divide the unmanageable and complex task into smaller sub parts and then solve it efficiently.

3. How the data is transferred from one layer to another in layered architecture?

Interface acts as a channel for transferring data from one layer to another in layered architecture.

4. Which network devices are used at the physical layer?

Hub, repeater, cables, modem are the network devices used at physical layer.