File Transfer Protocol

[seminar class]

[attachment=10808]
File Transfer Protocol
INTRODUCTION
 What is FTP?
 Network Protocol
 Exchange files over any network that supports the TCP/IP protocol
 Client-Server Architecture
 Separate Data and Control connections
 User based password authentication or anonymous user access
 PROTOCOL OVERVIEW
PROTOCOL OVERVIEW
 Client to Server on TCP Port 21 – Control Connection
 Commands
 Identifications
 Passwords
 Interrupt Messages
 Client to Server or vice-versa on TCP Port 20 – Data Connection
 Actual File Transfer
 Out-of-Bound Protocol
CONTROL CONNECTION
 Bi-directional
 Initiated by Client
 DATA CONNECTION
 Uni-directional
 Can be initiated by both client and server
 PROTOCOL OVERVIEW
 FTP uses TCP as a Transport Protocol
 The FTP Server, running FTP Server software, listens on the network
 The Client computer, running FTP Client software, initiates connection
 FTP only opens a data connection when a client issues a command requiring a data transfer
 Possible for an entire FTP session to open and close without a data connection ever having been opened.
CONNECTION MODES
 Active Mode
 Client sends Server the IP Address & Port Number
 Passive Mode
 Client is behind firewall
 Server sends client an IP Address and Port Number
 Active mode
• Passive mode
FILE STRUCTURE
 OS stores files in different structures
 FTP defines file structures for different files
 File F Unstructured, sequence of bytes
 Record R Series of records
 Page P Series of data blocks (pages)
 Default File Structure is F
 Specified using STRU command
TRANSMISSION MODES
 Stream Mode
 Data sent as a continuous stream
 All processing left to TCP
 End-of-File Indicator not required
 Blocked Mode
 FTP breaks data into several blocks
 Compressed Mode
 Data compressed using a single algorithm