FTP Sequence Diagrams

The diagrams below trace an FTP session across the control (port 21) and data (port 20) connections. To analyze an FTP capture of your own, VisualEther renders the Wireshark PCAP as a sequence diagram across both channels.

Here we explore the sequence of interactions in a typical FTP (File Transfer Protocol) session. Individual sequence diagrams for interactions on Port 20 and 21 are also included.

The complete sequence diagram can be divided into the following steps:

• DNS Query to obtain the IP address for the FTP Server
• FTP Telnet connection setup and login. (USER and PASS commands)
• Obtaining a directory listing (PORT and LIST command)
• Changing directory (CWD command)
• Downloading a file using FTP get (PORT and RETR command)