File Transfer Protocol (FTP) operates at the Application layer of the OSI model.
The Application layer is the highest layer in the OSI (Open Systems Interconnection) model. It provides network services directly to end-user applications. Protocols at this layer handle issues such as file transfer, email services, and web browsing, interacting directly with software applications used by the user.
As the name suggests, FTP's primary purpose is file transfer. It allows clients to download files from a server, upload files to a server, delete files, rename files, and perform other file management tasks. These are high-level services provided directly to the user or application, which is characteristic of protocols residing at the Application layer.
According to the reference provided:
| Purpose | File transfer |
|---|---|
| OSI layer | Application layer |
| Port(s) | 21 for control, 20 for data transfer |
FTP utilizes separate connections for control information (commands and responses) and data transfer. The control connection typically uses port 21, while data transfer often uses port 20 (for active mode). This separation of control and data channels is a unique characteristic of FTP among common Application layer protocols.
Understanding which layer a protocol operates at is crucial for comprehending how network communication functions and how different protocols interact within the network stack. FTP relies on lower-layer protocols, like TCP (Transmission Control Protocol) at the Transport layer, to ensure reliable delivery of its data and control information.
