In this tutorial, we will learn about transport layer in OSI model.

The fourth layer from the top is the transport layer. It’s primary function is to provide direct communication services to application processes running on various hosts. This layer allows application processes running on separate hosts to communicate logically. Despite the fact that application processes on separate hosts have no physical connection, application processes use the transport layer’s logical communication to deliver messages to one another.

Services Provided by Transport Layer in OSI Model :

End-to-end delivery : 

The transport layer generally sends the full message to its intended recipient. As a result, it assures that a whole message goes from source to destination.

Addressing : 

The system has the ability to run multiple programs at the same time. As a result, a form of address known as service point address or port must be there in the header. Each packet goes to the correct computer via the network layer, while the transport layer gets the entire message and restores the process on that machine.

Reliable delivery :

By re-transmitting missing and broken packets, the transport layer provides reliability services. Generally error control, sequence control, loss control, and duplication control are four components of dependable delivery.

Flow Control :

Flow control helps to keep the sender from sending too much data to the recipient. When a receiver is overwhelmed with data, it discards packets and requests that they be retransmitted. As a result, network congestion grows, lowering system performance. the transport layer handles flow control.

Multiplexing :

It is used by the transport layer to improve transmission efficiency. Multiplexing can take place in following two ways:

Multiple transport layer connections using the same network connection is known as upward multiplexing.

Downward multiplexing refers to the utilization of numerous network connections by one transport layer link.

Protocols for the Transport Layer in OSI Model :

TCP and UDP are the two protocols that make up the transport layer.

Transmission Control Protocol (TCP) is basically an acronym for Transmission Control Protocol. It provides apps with full transport layer services. It is a connection-oriented protocol. TCP establishes a connection between both transmission endpoints.

The User Datagram Protocol (UDP) stands for User Datagram Protocol. UDP is a straightforward protocol that allows for non-sequential transport. It’s a protocol that doesn’t require any connections.