How do session layers manage communication in networks?

Session layers manage communication in networks by establishing, managing, and terminating connections between applications.

The session layer, also known as layer 5 of the Open Systems Interconnection (OSI) model, plays a crucial role in the communication system of networks. It is responsible for setting up, coordinating, and terminating conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.

The session layer provides its services to the presentation layer above it and uses the services of the transport layer below it. It establishes a connection, or session, between processes running on different stations in the network. This session allows for data exchange and communication to take place. The session layer is responsible for setting up the conditions for communication, synchronising the data exchange, and managing the data transfer rate.

One of the key functions of the session layer is to manage the dialogue control. It keeps track of which device is speaking and which is listening. This can be in the form of a two-way simultaneous (full duplex), two-way alternate (half duplex), or one-way (simplex) communication.

Another important function is synchronisation. During long communication sessions, there may be a need for checkpoints, or synchronisation points, to avoid having to retransmit all the data if a failure occurs. The session layer can insert these checkpoints into the data stream and restart communication from a checkpoint if necessary.

The session layer also manages the termination of sessions. This could be due to a successful completion of data exchange, an error condition, or the session being idle for a long period. The session layer ensures that sessions are properly closed, with all data transmitted and none left pending.

In summary, the session layer in the OSI model plays a vital role in managing communication in networks. It establishes, manages, and terminates sessions between applications, ensuring smooth and efficient data exchange.