Incorrect Statement: FTP sends its control information in-band

Explanation:

FTP (File Transfer Protocol) is a standard network protocol used to transfer files between a client and a server on a computer network. It operates on the application layer of the TCP/IP protocol stack, which allows for the reliable transfer of files over the network.

FTP uses two parallel TCP connections:
FTP uses two parallel TCP connections during a session: a control connection and a data connection. The control connection is established between the client and the server to send commands and responses for controlling the file transfer process. The control connection uses port 21 by default.

The data connection, on the other hand, is used to transfer the actual file data. It is established dynamically during the file transfer process and uses a separate port (usually port 20 for active mode or a random port in passive mode). This separation of control and data connections allows for flexibility and efficient file transfers.

FTP sends exactly one file over the data connection:
FTP is capable of transferring multiple files over the data connection. It supports various commands to navigate through directories, upload files from the client to the server, download files from the server to the client, delete files, rename files, and perform other file-related operations.

FTP sends its control information out-of-band:
The incorrect statement is that "FTP sends its control information in-band." In-band refers to sending control information within the same data stream as the file data. However, FTP sends its control information out-of-band, separate from the data connection, over the control connection. This allows for the control information to be reliably transmitted and interpreted by the client and server.

Sending control information out-of-band ensures that the commands and responses related to the file transfer process are not mixed with the file data. This separation allows for better control of the transfer process and reduces the chances of errors or confusion during the file transfer.

In conclusion, the incorrect statement is that FTP sends its control information in-band. FTP actually sends its control information out-of-band over the control connection, while the data connection is used to transfer the actual file data.