BROCADE IP PRIMER

The Application Layer (Layer 7)This kind of communication is often diagrammed in this way:ApplicationApplicationdatadataPresentationPresentationdatadataSessionSessiondatadataTransportTransportsegmentssegmentsNetworkNetworkpacketspacketsData LinkData LinkframesframesPhysicalPhysicalbitsbits011011110001010101101Here you can see how the data flows, but you can also see how each layer onlycommunicates with its own layer. Physical Layer communicates with PhysicalLayer. Data Link Layer communicates with Data Link Layer, and so forth.Now that we know how the communication flows, let's get to know the individuallayers a little better.The Application Layer (Layer 7)This layer is one of the most recognized layers in all of the OSI ReferenceModel. Why? It's the layer that communicates with the users. Remember thathumans use these machines. “Computers talking to other computers” is agreat notion, but if, in the end, they don't make it possible for humans to shareinformation with other humans, it's pretty pointless.The Application Layer is where the data is created. Let's say, for example, thatyou want to send an e-mail. You would use an e-mail program to create an e-mail message and send it. The program takes that data (the e-mail message),and uses a Layer 7 protocol called Simple Mail Transfer Protocol (SMTP) tosend the message. It will take its journey down the other six layers and back upagain, but the Application Layer is SMTP.Brocade IP Primer 9