Layer Concepts and Uses

Layer Concepts and Uses 

Many uses are derived from smaller functional divisions or so-called layers. The definite usefulness is to reduce complexity so it can be more detailed.
Examples of their usefulness include:
 Human beings can discuss and introduce about detailed ways
 Make the device a modular form, so users can only use the required modules
 Creating an interconnected environment
 Reduced complexity in the programming so as to facilitate production
 Each layer can be given opening and closing according to the layer
 To communicate can immediately use the layer below.

Application Layer
This layer is related to the computer program used by the user. A computer program that deals only with programs that access the network, but if that does not mean it's not related to OSI. Example: The word processing application, this application is used for text processing so the program is not related to OSI. But if this program added network functionality such as email delivery, then the new layer application is here.

so the image follows the application layer

Presentation Layers 
In this layer, it is important to take care of the data formats that can be understood by various media. In addition, this layer can also convert the data format, so the next layer can understand the format needed for communication.
Examples of data formats supported by the presentation layer include Text, Data, Graphics, Visual Image, Sound, Video. Can be described as in Fig.

image Format the data at the presentation layer.

The Session Layer

Session layer defines how to start, control and end a conversation (called a session). Session layer example: NFS, SQL, RPC, ASP, SCP

image Coordinate various applications when interacting with computers

Transport Layer

In layer 4 it can be selected whether to use protocols that support error-recovery or not. Multiplexing against incoming data, sorting incoming data when not in sequence.

In this layer also end-to-end communication is arranged in several ways, so the affairs of the data are much influenced by this layer.

image Transport layer function

Functions provided by the transport layer: 

 Segmenting the top layer 

 Connecting end-to-end 

 Sending segments from 1 host to another host 

 Ensuring data reliability

Layer network

layer is addressing and routing. Addressing on the network layer is a logical addressing, Example of the use of IP address as in the following figure.

image Logic and physical addressing

Routing is used to route packet data path to be sent. Where routing there are 2 kinds of Routed and Routing Protocol.

image To go to another destination using Routing

Data Link Layer 

The functions provided in the data link layer include: Arbitration, physical media selection Overcoming, physical addressing Error detection, determining whether data is successfully sent Identification of Data Encapsulation, specify the header pattern on the data

See also: Understanding and Layers of OSI Layers