Internet Application-Level Protocols

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TCP/IP implements higher-level Internet protocols at the application program level.

Figure 1. Application layer of the TCP/IP Suite of Protocols
Application layer of the TCP/IP Suite of Protocols
This illustration shows the various layers of the TCP/IP Suite of Protocols. From the top, the application layer consists of the application. The transport layer contains UDP and TCP. The network layer contains the network (hardware) interface. And finally, the hardware layer contains the physical network.

When an application needs to send data to another application on another host, the applications send the information down to the transport level protocols to prepare the information for transmission.

The official Internet application-level protocols include:

  • Domain Name Protocol
  • Exterior Gateway Protocol
  • File Transfer Protocol
  • Name/Finger Protocol
  • Telnet Protocol
  • Trivial File Transfer Protocol

TCP/IP implements other higher-level protocols that are not official Internet protocols but are commonly used in the Internet community at the application program level. These protocols include:

  • Distributed Computer Network (DCN) Local-Network Protocol
  • Remote Command Execution Protocol
  • Remote Login Protocol
  • Remote Shell Protocol
  • Wake On LAN Protocol
  • Routing Information Protocol
  • Time Server Protocol

TCP/IP does not provide APIs to any of these application-level protocols.