FTP – File Transfer Protocol

5 דברים שלא ידעתם על FTP FTP is commonly run on two ports, 20 and 21.ports FTP run exclusively over TCP.TCP FTP is separated into control and data Control – commands Data – file tranfers The control follows the same protocol as Telnet

5 דברים שלא ידעתם על FTP FTP has 3 transmission modes: Stream mode - The data is transmitted as a stream of bytes. EOF or EOR will be indicated by a two-byte control word the first byte all 1 ’ s the second byte 1 for EOR 2 for EOF 3 for both. Block mode – The data is transmitted as a series of data blocks each preceded by a header

The header has 3 bytes: First byte called Descriptor Code : 128 End of data block is EOR 64 End of data block is EOF 32 Suspected errors in data block 16 Data block is a restart marker Last two bytes are the block byte count | Descriptor | Byte Count | 8 bits | 16 bits |

Compressed mode Compressed mode has 3 type of data being sent regular Compressed Filler bytes (space)

Compressed Mode Compressed mode has 3 type of data being sent Escape sequence

Commands Various commands for your enjoyment User Pass Acct – account Cwd – change working directory Cdup Smnt – mount different directory

Commands Various commands for your enjoyment Rein – restarts connection Quit – logs out

Commands TRANSFER PARAMETER COMMANDS Port Pasv – requests the server to listen Type – ascii /image … Stru – File structure (fie/record/page) Mode – transfer mode (stream/compressed/block)

Commands FTP SERVICE COMMANDS Retr – retrieves the file Stor – tells the server to upload the file and save it Stou – same only different name Appe – append the data to the file Allo – asks the server to allocate space for the file to be uploaded And so on …