OSI Model Transport Layer

Transport Layer : OSI Model

The Transport Layer is the middle layer(4^th Layer) of the OSI Model. The Transport-Layer acts as the transition point between the functions performed by Upper layers(Application Layer, Presentation Layer, Session Layer) & Lower layers(Network Layer, Data Link Layer, Physical Layer).
This layer is responsible for end to end data transmission service using connection oriented or either through connection-less protocols.
Data received from Upper layers application are combined into data streams and are transmitted to the receivers end in exact format as it was in original.
Hiding of sensitive details of data from networks and providing data transmission in a transparent mode is also done by the transport layer itself.

Segmentation : Large data is divided into smaller segments at the senders end and then these smaller segments are recombined in exact format before it is received at receivers end.
Error Control : Distortion, Un-delivery of data packets and noise in data packets results in error and this is prevented using Transport Layer too and this feature is called Error Control.
Flow Control : Transport-Layer ensures that faster data transmission and slow data absorption or slow data transmission and faster data absorption must not occur.
Transport-Layer performs Multiplexing & De-multiplexing functions too.
Connection oriented service using TCP(Transmission Control Protocol) Protocol & Connection less service using UDP(User Data-gram Protocol) Protocol are performed by transport layer.

Transport Layer : Architecture