Transport Layer

Today single device can run multiple applications and provide multiple services such as email, web, video, audio and instant messaging. Data from each of these applications are packaged, transported and delivered to the right application on the destination device

 The transport layer (Layer 4) of the OSI model accepts data from the application layer and prepare it for addressing at the network layer. A sending device communicates with a receiving device to make a decision how to split data into segments, how to make possible data sending without losing any segment, how to confirm all the segments arrived at receiving the device.

The transport layer is responsible for end-to-end communication over a network. It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components.

Functions of the Transport Layer

Following are the functions of the transport layers.

• Connection management


• Segmentation


• Reliable and unreliable data delivery


• Flow control


• Connection multiplexing


• It makes possible to allow multiple applications work at the same time send and receive data.


• Data transmission method can be connection-oriented or connectionless according to requirement. Connectionless uses UDP and connection-oriented uses TCP.


• The sequence numbers and acknowledgments (ACKs) are used for reliability.


• Reliable connection controls flow through the uses of windowing or acknowledgments.

In the next, lesson we will discuss the above functions in depth.