What is the transport layer?

The transport layer is essential for the source to deliver a complete message. The network layer is answerable for the end-to-end delivery of single packets.

The transport layer obtains the messages of self-assertive length from the session layer, and divides them into packets. It also endures them to the network layer for communication, and completely reassembles the destination's packets.

The transport layer data is an order number in every packet and helps the order numbers to identify the lost packets. Additionally, it ensures that the messages are regenerated in the proper order.

The functioning of the transport layer is depicted in the diagram below −

Functions of transport layer

The functions of transport layer are explained below −

  • Service Point Addressing: The system can run various programs at the equivalent time. For this reason, the header, therefore, must contain a type of address known as service point address or port. The Network layer is taken as each packet to the correct computer, whereas the transport layer receives the entire message to restore the process on that computer.

  • Segmentation and reassembly: The message is split into several packets. Each packet has its sequence number. The transport layer reassembles the message correctly according to the order number and identifies those lost.

  • Connection Control: This layer can be connection-oriented or connectionless. The connectionless transport layer treats each packet as independent and produces it to the destination. But, the connection-oriented transport layer first makes the connection and then provides the respective data.

  • Flow Control: It is also responsible for flow control implemented end to end instead of across an individual link.

  • Error Control: The transport layer can support error control. The error control at the transport layer is implemented end to end instead of across an individual link. Error correction is frequently completed by retransmission.