The Transport Layer

The Transport Layer is responsible for delivering the data to the appropriate application on the host computer. Since a single server can have multiple applications running on different ports, it is necessary to send the data to the right port, for example:

• SMTP is bound to port 25
• HTTP is bound to port 80

We don't want the HTTP traffic to be sent to SMTP. This is one of the reasons why Source port and Destination port is an integral part of this layer.

Along with this, in order to make sure that the data is transmitted and that it is in a proper sequence, there are various important parameters, such as Sequence number and Acknowledgment number:

The core protocols in this layer are TCP and UDP.