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Chapter 8

Chapter 8. File Transfer Protocol – Simple Mail Transfer Protocol. Objectives. Configuring a Web Service Infrastructure FTP SMTP. Configuring FTP. Definition : provides a method by which users can upload and download data through web pages or networks. Versions : FTP 6 FTP 7 RFC 959

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Chapter 8

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  1. Chapter 8 File Transfer Protocol – Simple Mail Transfer Protocol Lecturer : Ms.Trần Thị Ngọc Hoa

  2. Objectives • Configuring a Web Service Infrastructure • FTP • SMTP Lecturer : Ms.Trần Thị Ngọc Hoa

  3. Configuring FTP • Definition : provides a method by which users can upload and download data through web pages or networks. • Versions : • FTP 6 • FTP 7 • RFC 959 • uses two TCP Ports • one for control • one for data transfers • command-response protocol Lecturer : Ms.Trần Thị Ngọc Hoa

  4. FTP Commands • Due to multiple hardware types and operating systems file are converted to four environmentally neutral data type for transport and the converted to local types at the destination • ASCII A NVT-ASCII • EBCDIC E EBCDIC Text • IMAGE I Raw binary, series of octets • LOCAL L Raw binary using a variable byte size • Client responsibility to tell server data type to use • Default data type, unless otherwise specified is ASCII Lecturer : Ms.Trần Thị Ngọc Hoa

  5. FTP Commands • USER R User name, userid for access control • PASS O Password for access control • ACCT O Account info • CWD O Change working directory • CDUP O Change to parent directory • SMNT O Structure mount, mount a different file system • QUIT R informs server that client wants out • REIN O restarts session at authentication phase • PORT R Host addr and data port to use Lecturer : Ms.Trần Thị Ngọc Hoa

  6. FTP Commands • PASV O Passive; informs server that client will contact to set up data connections, ask server to sent port info • TYPE R Data type, type of subsequent transfers • STRU R File structure • MODE R Transfer mode • RETR R Retrieve, download the file from server • STOR R Store, upload the specified to server • STOU O Store unique, same as store but server picks unique file name Lecturer : Ms.Trần Thị Ngọc Hoa

  7. Understanding SMTP • Jane invokes her e-mail service on her local machine. • Jane supplies Elvis’s e-mail address, composes a message, and instructs the SMTP user agent (e-mail service) to send the message. • The message is sent to Jane’s mail server and placed in a queue. • The client side of SMTP, running on Jane’s mail server, uses DNS to locate the destination mail server. • Jane’s mail server opens a TCP connection to the SMTP server at the destination. Jane’s SMTP client sends the message into the TCP connection. • Elvis’s SMTP server receives the message and places it in Elvis’s mailbox. • An Elvis impersonator reads the message at his convenience. Lecturer : Ms.Trần Thị Ngọc Hoa

  8. IP header SMTP agent SMTP (client) SMTP (server) TCP header SMTP header TCP TCP TO: elvis@graceland.com Dear Elvis, I don’t believe you’re really dead. Please reply. Love, Jane Doe Text of Message IP IP Understanding SMTP Jane’s Local Host Jane’s Mail Server Elvis’s Mail Server 1. Jane invokes her local SMTP agent 6. Elvis’s Mail Server receives e-mail and puts it in his mailbox 2. Jane constructs e-mail message 3. Jane sends e-mail to her mail server for delivery 4. Jane’s Mail Server establishes a TCP connection with Elvis’s 7. TCP Connection is terminated 5. Mail is delivered via a sequence of TCP packets exchanges Lecturer : Ms.Trần Thị Ngọc Hoa

  9. Understanding SMTP Exchange of SMTP messages after an initial TCP handshake Sender: Client (Jane’s Mail Server) MAIL FROM: <jane.doe@marist.edu> Sender’s e-mail address is supplied Server (Elvis’s Mail Server) 250 Hello marist.edu SMTP Connection message acknowledged Client (Jane’s Mail Server) . Period on separate line signifies the end of message Client (Jane’s Mail Server) I can’t believe you’re really dead. Please reply. Love, Jane Doe Client (Jane’s Mail Server) DATA Ready to send data • Server (Elvis’s Mail Server) • elvis@graceland.com …Recipient ok • Acknowledges previous message and indicates a valid recipient on this mail server Client (Jane’s Mail Server) RCPT TO: elvis@graceland.com Identifies the Receiver’s URL Server (Elvis’s Mail Server) 354 Enter mail, end with “.” on sep. line Ready to receive message Server (Elvis’s Mail Server) 250 Message accepted for delivery Acknowledges receipt of the e-mail Server (Elvis’s Mail Server) 221 graceland.com closing connection SMTP connection with indicated MS closed Client (Alice’s Mail Server) QUIT Indicates no more e-mails to transmit • Server (Elvis’s Mail Server) • jane.doe@marist.edu • Sender’s URL Received ok Client (Jane’s Mail Server) HELO marist.edu SMTP Connect from (Mail Server ID) Server (Elvis’s Mail Server) Message: 220 graceland.com Meaning: Connection established with mail server ID Lecturer : Ms.Trần Thị Ngọc Hoa

  10. Lab Demo Lecturer : Ms.Trần Thị Ngọc Hoa

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