The Application Layer ( Layer 7 )

____________________________________________
This is the layer where the end users themselves interact with the network. Authentication services also run at Layer 7, but encryption runs at the next layer down.

The application layer ensures that the remote communication partner is available, that needed communication resources exist ( a modem, for example ). and that both ends of the communication agree on procedures involving data integrity, privacy and error recovery.

When trying to decide if a protocol is an Application layer protocol, just remember that protocols that require the end user to enter a request are Application layer protocols. Firewalls, devices intended to keep network intruders out, operate at L7.

Protocols and services that run at L7 include:
-  Email protocols SMTP ( Simple Mail Transfer Protocol ) and POP3 ( Post Office Protocol )
- Telnet
- HTTP
- File Transfer Protocol (FTP)
- Trivial File Transfer Protocol (TFTP)
- Simple Network Management Protocol (SNMP) - allows us to gather network information and analysis, particularly for CISCO switches GUI
____________________________________________