Ftp control connection

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

An FTP control connection is the TCP connection through which an FTP client authenticates and sends commands to an FTP server.

An FTP control connection is the first TCP connection in an FTP exchange. After the TCP three-way handshake, the server authenticates the client, and the client sends commands through this connection. section 8.2.1

Operational facts:

• FTP servers listen for control connections on TCP port 21. section 8.2.1
• The control connection carries authentication and commands such as RETR, but not the transferred file. section 8.2.1
• A separate FTP data connection carries the actual file exchange, allowing multiple data transfers through one control connection. section 8.2.1

Retrieving a file

After authentication succeeds, a Cisco device can send a RETR command for a server file. The command travels over the control connection; the file contents travel over the separate data connection. section 8.2.1

Figure 8.4 An FTP exchange involves two TCP connections: an FTP control connection, and an FTP data connection.

Follow the exchange diagram to distinguish the control connection’s handshake and command phase from the later data connection. section 8.2.1

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes

Explains TCP establishment, authentication, commands, port 21, and separation from the data connection.

Examples

Uses the RETR command and a two-connection exchange diagram to illustrate FTP file retrieval.

What you can do after

Evaluate FTP exchanges by separating command and authentication traffic from file-transfer traffic.

How it connects

Links FTP control connection to TCP, FTP data connection, authentication, FTP commands, and RETR.

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Related concepts

• FTPpart of · FTP is an application-layer network protocol for transferring files between networked systems, typically using separate control and data connections.
• ftp data connectioncontrasts with · An FTP data connection is the separate TCP connection used to transfer file data between an FTP client and server.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.