Application layer protocol functions

Shirshendu De

While studying CCNA R&S I have come across a sentence which states that ''Application layer protocols are used to exchange data between programs running on the source and destination hosts''. What are these programs? Can anyone provide some examples.

clarson

The application layer is the seventh layer of the OSI model and the only one that directly interacts with the end user.
The application layer provides many services, including:

• Simple Mail Transfer Protocol
• File transfer
• Web surfing
• Web chat
• Email clients
• Network data sharing
• Virtual terminals
• Various file and data operations

Shirshendu De

So is it that the points which you have written in bullet points are the programs. Just check whether my example is correct or not. Say, I am typing something in word and then there is a language compiler to convert it into some logical data understood by the computer. So this is interacting with the language compiler of the destination device. May be many exchanges with different programs taking place. Here, can I take ''language compiler' as an example of a program.

kaiju

An article on Techopedia does a good job of explaining the protocols for every layer (scroll down for the other layers).

albinorhino187

Shirshendu, in your own example, that's all existing within the same machine. Using clarson's bullets, think about file transfer say with FTP. Your computer is acting as the FTP client, and then you're going to copy a file to another device acting as an FTP server. Both your machine and the server are running FTP application software, which creates the data to be encapsulated and passed down the OSI stack until it's at the physical layer and sent accross the wire.

When the server receives those signals, it passes it back up the OSI stack, de-encapsulating each layer, until it reaches the FTP application data which it will correctly be able to interpret and handle since it's running compatible FTP program software just like your machine.