Application Layer - Seventh Layer in OSI Reference Model

Application Layer is the seventh layer in Open System Interconnection (OSI) Reference Model. The function of the Application layer is to present data to users by enabling direct interaction between user and software applications. In simple words, the major function of the Application layer in the OSI Reference Model is to provide a user interface. The user interface can be either a command line based or GUI based. GUI based user interface is used in a web browser and Command Line Interface(CLI) is used in Routers and Switches (IOS high-end Routers and Switches).


A set of protocols are working on the application layer. These application layer protocols are classified into two.

1. Common Application Specific Elements (CASE)
2. Specific Application Specific Elements (SASE)

The major Application Layer protocols are:

1. Telnet
2. File Transfer Protocol (FTP)
3. Simple Mail Transfer Protocol (SMTP)
4. FTAM
5. HTTP
6. DHCP
7. NFS
8. POP3
9. NNTP
10. IRC

1. Physical layer
   
   
2. Data link layer
   
   
3. Network layer
   
   
4. Transport layer
   
   
5. Session layer
   
   
6. Presentation layer
   
   
7. Application layer

The major Application Layer utilities are.

1. Address Resolution Protocol (ARP)
   
   
2. Netstat
   
   Netstat works in the application layer. To learn more about this application layer utility, visit the link below.
   Netstat -A Command Line Tool
   
   
3. Ping
   
   
4. Tracert
   
   
5. FTP and TFTP
   
   
6. Hostname
   
   
7. Whois

Technology Guide