Each layer here interacts only with the layer above and below it.
But there must be some external interaction with the stacks here.
So here I draw some diagrams that will show you two external connections and the link layer interacts
with the physical network connections, transmitting the data in a physical medium.
Right?
So such as a process of electricity or light and the application layer interacts with the other application.
And an application is a collection of related functionality that provides a service to a user.
And in this figure you are seeing an example of an application that processes an email.
And the service provided by the email application is sending and receiving of messages over a network.
And here typically applications contains these components, which is the network communication.
Uh, this component communicates over the network and processes incoming and outgoing data for a email
application.
The network communication is most likely standard protocol such as SMTP, POP3, IMAP or others.
And we also have the content parsers here.
Oops.
Actually we are here.
Content parsers.
So data transferred over a network usually contains content that must be extracted and processed.
So content might include textual data such as the body of an email, or it might be pictures or video.
And we also have the user interface and this is the user interface that user interacts to it.
So the UI allows the user to we received emails and, and to create a new emails for transmission In
an email application.
The UI might display emails using the HTML in a web browser and then I will also notify you that the
user interacting with the UI doesn't have to be a human being.
It could be another application that automates the sending and receiving of emails through a command
line tool.