The TCP/IP Transport Layer
October 27th, 2009 by BobThe TCP/IP transport layer consists of two main protocol options:
the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
TCP/IP needs a mechanism to guarantee delivery of data across a network and the transport layer handles this. In short the transport layer provides a service to the layer above it, the application layer.
The benefits of TCP error recovery cannot be seen unless the data is lost. Let’s say Bob’s web browser was to request information from Larry’s server, if either transmission were lost (Bob’s request to Larry or Larry’s response to Bob), HTTP would not take any direct action, but TCP would resend the data and ensure that it was received successfully.
In the above example demonstrates a function called adjacent-layer interaction, which defines the concepts of how adjacent layers in a networking model, on the same computer, work together. The
higher-layer protocol (HTTP) needs to do something it cannot do (error recovery). So, the higher layer asks for the next lower-layer protocol (TCP) to perform the service, and the next lower layer performs the service. The lower layer provides a service to the layer above it.
| Concept | Description |
|---|---|
| Same-layer interaction on different computers | The two computers use a protocol to communicate with the same layer on another computer. The protocol defined by each layer uses a header that is transmitted between the computers, to communicate what each computer wants to do. |
| Adjacent-layer interaction on the same computer | On a single computer, one layer provides a service to a higher layer. The software or hardware that implements the higher layer request that the next lower layer perform the needed function. |