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The Session layer and Its Role

The session layer is the fifth layer in the OSI reference model. It responds to service requests from the Presentation layer and issues service requests to the Transport layer. This tutorial explains the role of the Session layer in a network and its critical functions.



Where is The Session Layer?

The session layer is between the Transport and Presentation layers in the OSI reference model.


You cannot find a session layer in the TCP/IP model.


If someone asks where is the Session layer in a TCP/IP model, answer them there is no separate session layer in that model. The Application layer in the TCP/IP model handles the role of the session layer.



What Does The Session Layer Do?

The primary function of the Session layer is to create, maintain, and terminate sessions. The session layer is also responsible for finding and sending data across the correct connection.


The Session layer communicates with the Transport layer to set up and tear down the connection.


We will learn more about the importance and working of the Session layer by studying its functions. The functions of the Session layer are listed below.



The Functions of the Session Layer are:


  1. It starts and ends a session across a network.

  2. Allows applications to share information.

  3. Ensures that information is flowing to the right place.

  4. Communicate to the presentation layer and Transport layer.

Another question you may hear is about the maximum number of sessions supported by the Session layer in a network. The answer is simple. A session layer is there because it handles multiple sessions at a time.


We can have multiple sessions on a network due to the Session layer.


Let me explain it with a practical example. We are seeing a movie where sound and sight both should match. It is one of the applications of the Session layer.


  1. What is an OSI Reference Model?
  2. The Functions of MAC Sublayer ( IEEE 802.3)
  3. IEEE 802.11 WiFi Standards Backward Compatibility Checker
  4. How to Fix The Ping Request Timed Out Error?

You have learned about the working and functions of the Session layer. We will complete this tutorial by providing the list of protocols in this layer.




List of Session layer protocols

  1. AppleTalk Data Stream Protocol (ADSP)
  2. AppleTalk Session Protocol (ASP)
  3. Call Control Protocol for Multimedia Communication
  4. Internet Storage Name Service
  5. Network Basic Input Output (NetBIOS)
  6. Password Authentication Protocol (PAP)
  7. Point-to-Point Tunneling Protocol (PPTP)
  8. Remote Procedure Call Protocol (RPC)
  9. Short Message Peer-to-Peer (SMPP)
  10. Secure Shell (SSH)

Suggested Readings

  1. Physical layer

  2. Data link layer

  3. Network layer

  4. Transport layer

  5. Session layer

  6. Presentation layer

  7. Application layer

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