The topmost layer, Application Layer of TCP/IP protocol suit  is concerned mainly with human interaction and the implementation of software applications and related protocols.

TCP/IP protocol suit is included with a large number of applications and application protocols. Using these applications and application protocols, data can be moved between hosts, and remote users can communicate.

A user may or may not directly interacts with the applications. Application layer is where the actual communication is initiated and reflects. Because this layer is on the top of the layer stack, it does not serve any other layers.

When an application layer protocol wants to communicate with its peer application layer protocol on remote host, it hands over the data or information to the Transport layer. The transport layer does the rest with the help of all the layers below it.

Following are a partial list of applications and application protocols included with TCP/IP protocol suit and operate in the Application Layer.

• Hypertext Transfer Protocol (HTTP)
• Simple Mail Transfer Protocol (SMTP)
• Dynamic Host Configuration Protocol (DHCP)
• Domain Name System (DNS)
• Simple Network Management Protocol (SNMP)
• File Transfer Protocol (FTP)
• Trivial File Transfer Protocol (TFTP)

Functionalities provided by Application Layer

• Remote login to hosts
• File transfer
• Electronic mail transport
• Networking support
• Host initialization
• Remote host management