Data compression and the transport services, The main purpose of the transport layer is to provide services which are efficient, reliable and cost-effective. These services are processed in application layer. In order to attain the objective, the transport layer uses the services which are provided by its lower layer that is network layer. The services are accessed by the software or hardware called as transport entity, which is saved in a library package bound, an operating system kernel, a different user process or on network interface card.

Similar to the network service, transport service is also alienated into two types that is connection-oriented transport service and the connectionless transport service. Although, the functionalities of these layers are mostly similar, both of them use separate services because code of transport layer is executed on the user’s machine and the code of network layer is executed on the routers operated by the carrier.

Due to the existence of transport layer, the transport services are considered as highly-reliable services when compared with the underlying network service. The transport layer can even detect and compensate the loss of the packets during transmission.