Session Layer

The Open Systems Interconnect Model deals with the communication of different computers and devices on a network. The fifth layer of this seven-layer model is known as the session layer. This layer performs important functions in regard to the establishment of communication between two different computers or devices on a network. So, how does the session layer work?

What are some ways to better understand the workings of the session layer and how it affects nearly everything that we do on our computers?

First, let’s try to put this in concrete, real terms. When speaking in networking terms, it can be confusing to keep track of what is what because many of the terms we deal with come from abstract concepts. An example often used to describe the session layer is of receiving a phone call.

Let’s break down this example below, paying close attention to how it relates to the session layer.

The session layer deals with the creation, maintenance, and closing of “sessions” of communication.

Let’s take a look at our phone call example:

1- You receive a phone call. When you answer the phone, the first thing you do is identify the person who has called you. Once this has been done, you being the real conversation. This is very similar to how the session layer establishes a connection for communication across a network. Using ports to make identification, session layer protocols establish a connection between two computers on a network.

2- It’s possible that you may have to speak to someone on the phone and someone close to you at the same time. Computers run in a similar manner, as they may perform multiple tasks–multiple sessions–at the same time. The session layer uses port numbers to establish and maintain each and every one of these sessions.

3- When you have finished your conversation, you close the call with a farewell, and the person to whom you are speaking also agrees to end the call. On computers, the session layer performs this important task. After both computers signal through their protocols that they are ready to close communication, the session layer ends that particular communication between computers on a network.

Some important protocols in the session layer are NetBIOS and PPTP. These two protocols aid in the functions of the session layer, and give you the ability to make establish and close contact and communication with other computers.