Lecturer : Ms.Trần Thị Ngọc Hoa

Chapter 8Chapter 8

File Transfer Protocol – Simple File Transfer Protocol – Simple Mail Transfer ProtocolMail Transfer Protocol

Lecturer : Ms.Trần Thị Ngọc Hoa

ObjectivesObjectives

Configuring a Web Service Infrastructure FTP SMTP

Lecturer : Ms.Trần Thị Ngọc Hoa

Configuring FTPConfiguring 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

FTP CommandsFTP 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 LOCALL 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

FTP CommandsFTP 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

FTP CommandsFTP 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

Understanding SMTP Understanding SMTP

1. Jane invokes her e-mail service on her local machine.2. Jane supplies Elvis’s e-mail address, composes a message,

and instructs the SMTP user agent (e-mail service) to send the message.

3. The message is sent to Jane’s mail server and placed in a queue.

4. The client side of SMTP, running on Jane’s mail server, uses DNS to locate the destination mail server.

5. 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.

6. Elvis’s SMTP server receives the message and places it in Elvis’s mailbox.

7. An Elvis impersonator reads the message at his convenience.

Lecturer : Ms.Trần Thị Ngọc Hoa

Understanding SMTPUnderstanding SMTP

TCP

SMTP

(client)

IP

TCP

SMTP

(server)

IP

SMTP

agent

Jane’s Local Host Jane’s Mail Server Elvis’s Mail Server

1. Jane invokes her local SMTP agent2. Jane constructs e-mail message

TO: elvis@graceland.com

Dear Elvis,

I don’t believe you’re really dead. Please reply. Love, Jane Doe

3. Jane sends e-mail to her mail server for delivery4. Jane’s Mail Server establishes a TCP connection with Elvis’s5. Mail is delivered via a sequence of TCP packets exchanges

IP header

TCP header

SMTP header

Text of Message

6. Elvis’s Mail Server receives e-mail and puts it in his mailbox7. TCP Connection is terminated

Lecturer : Ms.Trần Thị Ngọc Hoa

Understanding SMTPUnderstanding SMTPExchange of SMTP messages after an initial TCP handshake

220 graceland.com

Sender:

Message:

Server (Elvis’s Mail Server)

Meaning: Connection established with mail server ID

Client (Jane’s Mail Server)

HELO marist.edu

SMTP Connect from (Mail Server ID)

Server (Elvis’s Mail Server)

250 Hello marist.edu

SMTP Connection message acknowledged

Client (Jane’s Mail Server)

MAIL FROM: <jane.doe@marist.edu>

Sender’s e-mail address is supplied

Server (Elvis’s Mail Server)

250 jane.doe@marist.edu

Sender’s URL Received ok

Client (Jane’s Mail Server)

RCPT TO: elvis@graceland.com

Identifies the Receiver’s URL

Server (Elvis’s Mail Server)

250 elvis@graceland.com …Recipient ok

Acknowledges previous message and indicates a valid recipient on this mail server

Client (Jane’s Mail Server)

DATA

Ready to send data

Server (Elvis’s Mail Server)

354 Enter mail, end with “.” on sep. line

Ready to receive message

Client (Jane’s Mail Server)

I can’t believe you’re really dead. Please reply. Love, Jane Doe

Client (Jane’s Mail Server)

.

Period on separate line signifies the end of message

Server (Elvis’s Mail Server)

250 Message accepted for delivery

Acknowledges receipt of the e-mail

Client (Alice’s Mail Server)

QUIT

Indicates no more e-mails to transmit

Server (Elvis’s Mail Server)

221 graceland.com closing connection

SMTP connection with indicated MS closed

Lecturer : Ms.Trần Thị Ngọc Hoa

Lab DemoLab Demo