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COS 420 DAY 25. Agenda Assignment 5 posted Chap 22-26 Due May 4 Final exam will be take home and handed out May 4 and Due May 10 Today we will discuss.

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Presentation on theme: "COS 420 DAY 25. Agenda Assignment 5 posted Chap 22-26 Due May 4 Final exam will be take home and handed out May 4 and Due May 10 Today we will discuss."— Presentation transcript:

1 COS 420 DAY 25

2 Agenda Assignment 5 posted Chap 22-26 Due May 4 Final exam will be take home and handed out May 4 and Due May 10 Today we will discuss Electronic Mail (SMTP, POP, IMAP, MIME)

3 Project 2 Grading Meeting Timelines 10% Deliverables Program requirements Due March 30 15% late Protocol Definition Due April 13 15% Better but I hope to see improvement by May1 Working Network Application Due May 4 25% Final Paper Due May 1 25% User Manual Protocol Program requirements Technical Specifications Presentation Due May 4 10%

4 Electronic Mail Among most widely used Internet services Two major components User interface Mail transfer software Paradigm: transfer is separate background activity

5 Illustration Of Email System Components

6 Mailbox Names And Aliases Email destination identified by pair ( mailbox, computer ) Aliases permitted (user enters alias that is expanded)

7 Forwarding Powerful idea Email arriving on a computer can be forwarded to an ultimate destination

8 Illustration Of Aliases And Forwarding

9 TCP/IP Standards For Email Syntax for email addresses Format of email message Protocols for email transfer and mailbox access

10 Email Address Syntax Mailbox identified by string mailbox@computer String computer is domain name of computer on which a mailbox resides String mailbox is unique mailbox name on the destination computer

11 Format Of Email Message Message consists of Header Blank line Body of message Headers have form keyword : information Standard given in RFC 2822

12 E-mail header Return-Path: Received: from granite.unet.maine.edu ([unix socket]) by granite.unet.maine.edu (Cyrus v2.2.12-Maine-RPM-2.2.12-3.RHEL4.1.um.2) with LMTPA; Fri, 28 Apr 2006 14:16:12 -0400 X-Sieve: CMU Sieve 2.2 Received: from VoisineScott (VoisineScott.umfk.maine.edu [130.111.68.129]) by granite.unet.maine.edu (8.13.1/8.13.1) with ESMTP id k3SIEdHh000307; Fri, 28 Apr 2006 14:15:06 -0400 From: "Scott Voisine" To: "Scott Voisine" Subject: EDU 405 Play Date: Fri, 28 Apr 2006 14:14:39 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0032_01C66ACE.22D15830" X-Mailer: Microsoft Office Outlook 11 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 Thread-index: AcZq75BMY/2KYcRVRGurpMOPNTltNA== X-MailScanner-Information: Please contact the ISP for more information X-MailScanner: Found to be clean X-MailScanner-From: voisine@maine.edu

13 Protocol For Email Transfer Specifies interaction between transfer components Transfer client Transfer server Standard protocol is Simple Mail Transfer Protocol (SMTP)

14 SMTP Application-level protocol Uses TCP Commands and responses encoded in ASCII

15 Example Of SMTP

16 Protocol For Mailbox Access Used when user’s mailbox resides on remote computer Especially helpful when user’s local computer is not always on-line Two protocols exist Post Office Protocol version 3 (POP3) Internet Message Access Protocol (IMAP) Each provides same basic functionality User authentication Mailbox access commands

17 Multipurpose Internet Mail Extensions (MIME) Permits nontextual data to be sent in email Graphics image Voice or video clip Sender Encodes binary item into printable characters Places in email message for transfer Receiver Receives email message containing encoded item Decodes message to extract original binary value

18 MIME Header Header in email message describes encoding used Example From: bill@acollege.edu To: john@example.com MIME-Version: 1.0 Content-Type: image/jpeg Content-Transfer-Encoding: base64...data for the image...

19 Seven Basic MIME Types

20 Example Of Mixed / Multipart Message

21 Summary Email operates at application layer Conceptual separation between User interface Mail transfer components Simple Mail Transfer Protocol (SMTP) Standard for transfer Uses ASCII encoding Post Office Protocol (POP) And Internet Mail Access Protocol (IMAP) allow access of remote mailbox. Multipurpose Internet Mail Extensions (MIME) permits transfer of nontextual information (e.g., images)


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