Telecommunications Management 273-436/635

1. Telecommunications Management273-436/635 Lecture 9: Distributed Applications: E-mail, EDI, WWW

2. Distributed Applications • Distributed applications - becoming more widespread • Most distributed applications are proprietary • They are developed for in-company purposes, e.g. distributed databases containing sales or product info. • Growing need for organizations to communicate and share information • A number of applications conforming to certain standards have been developed to permit electronic communication between organizations Grant

3. Important Distributed Applications • Electronic mail (E-Mail) • Electronic data interchange (EDI) • World Wide Web applications (WWW) Grant

4. Electronic Mail • A facility that allows users at workstations and terminals to compose and exchange messages • E-mail facility can reside on • A single computer • An internal network of computers • A public network Grant

5. Electronic Mail • Public email services • Provided by third party vendor • Bell Sympatico • America on Line • CompuServe • MCI, etc. • Private email services • Intra-organizational communication • Supported by proprietary or generalized email packages - e.g. FirstMail, cc:Mail, etc. Grant

6. Common Electronic Mail Facilities • Message Preparation • Word processing - creating and editing a message • Annotation - such as when replying to a message • Message sending • User directory - Address book • Timed delivery - set time for delivery • Multiple addressing - TO: CC: BCC: Distribution lists • Message priority • Status information - receipts, queues • Interface to other facilities - telex, fax, etc. Grant

7. Common Electronic Mail Facilities • Message Receiving • Mailbox scanning - display contents of maibox • Message selection - for display, printing, storing, deleting • Message notification - “beeping”, “Dialog box”, etc • Message reply - • Message rerouting - forward Grant

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10. Logical Components of an Email System • Hardware • Server • Client • Communication link ( Network, modem, etc.) • Software • Client application (user agent) - for managing email (creating, reading, sending, deleting, etc) • Server application (message transfer agent) -for file management and communications Grant

11. Single or Multiple-Computer Email • Single-system facility • Each user registered with a user name e.g. Grant • Each user has a private mailbox • Each user logs on to the system using a mail “client” application. • Retrieves email from his mailbox onto his desktop • Can store messages for reading later Grant

12. Single or Multiple-Computer Email • Distributed mail system facility • A number of mail servers connect over WAN • Messages are transferred over the network by the server software. • Offered by many vendors Grant

13. Some Email Standards - Protocols • TCP/IP [Transmission Control Protocol / Internet Protocol] - (transport)- Internet • SMTP [Simple Mail Transport Protocol] - (inter-system delivery) - Internet • MIME [Multipurpose Internet Mail Extensions] - ( for file attachments) - Internet • IMAP [Internet Message Access Protocol]- (client and server mail interaction/storage) - Internet Grant

14. Some Email Standards - Protocols • MAPI [Mail Application Programming Interface] - (application interface) - Microsoft • X.500 - (Directory service)- ISO • LDAP [Lightweight Directory Access Protocol] (Directory Service) - Internet Grant

15. Email Standards - Clients • OS Clients • UNIX - SUN, SGI, AIX, et al • PC - Windows 3.1, Windows 95, Windows NT • Apple - MAC/OS, Newton • Others over time Grant

16. IMAP - Internet Mail Access Protocol • The newer type of Internet mail server. It allows connected stations to first view message headers and choose which, of the mail messages for them, they wish to receive. (The others remain stored on the mail server.) • Can work with the older POP2 and POP3 mail servers, only offering the POP functionality (for example, you need to accept all mail messages once a connection is established to the mail server). Grant

17. POP - Post Office Protocol • The older type of Internet mail server. • Most new servers are IMAP. POP downloads all mail to a user as soon as the user connect to the mail server. Grant

18. Single-Systems Email Grant

19. Network of Email Systems Grant

20. Simple Mail Transfer Protocol • Protocol used in TCP/IP networks for transferring electronic messages between end user computers and mail servers • IT is defined by RFC (request for comments) 821. • SMTP is not concerned with the message format • Message formats are defined by RFC 8222 Grant

21. SMTP - Outgoing mail Grant

22. SMTP - Incoming mail Grant

23. SMTP Transfer process • User initiates mail procedure (e.g. send) • Sender SMTP establishes two-way connection with receiver-SMTP • SMTP commands are generated by the sender and sent to the receiver • SMTP replies are sent from the receiver to the sender Grant

24. SMTP Procedures • MAIL <SP> FROM:<reverse-path> <CRLF> • This tells the SMTP-receiver that a new mail transaction is starting and to reset all states. It also gives the reverse-path which can be used to report errors • RCPT <SP> TO:<forward-path> <CRLF> • This give the forward-path identify the receiver • Forward path can contain more than one mailbox • DATA <CRLF> • All succeeding lines of text sent • Terminated by a period (.) Grant

25. Example of the SMTP Procedure • S: MAIL FROM:<Smith@Alpha.ARPA> • R: 250 OK • S: RCPT TO:<Jones@Beta.ARPA> • R: 250 OK • S: RCPT TO:<Green@Beta.ARPA> • R: 550 No such user here • S: RCPT TO:<Brown@Beta.ARPA> • R: 250 OK • S: DATA • R: 354 Start mail input; end with <CRLF>.<CRLF> • S: Blah blah blah... • S: ...etc. etc. etc. • S: <CRLF>.<CRLF> • R: 250 OK Grant

26. Multipurpose Internet Mail Extension (MIME) • SMTP has several limitation • Cannot transmit executable files or binary objects seamlessly • Cannot transmit text data using international character set • Servers may reject files over a certain size • Gateways may translate between ASCII and other character codes in an inconsistent manner • SMTP gateways to X.400 cannot handle non-textual data • Some non-standard implementations of SMTP Grant

27. Multipurpose Internet Mail Extension (MIME) • MIME develop to address these limitations • MIME is implemented using header fields • Five header fields • MIME-Version • Content-Type - describes the type of data in the message • Content-Transfer-Encoding - specifies the type of encoding transformation that was applied • Content-ID • Content-Description Grant

28. MIME Content Types Specifies the nature of the data in the body of an entity • Text - plain text • Multipart - Mixed, parallel, alternative, digest • Message - rfc822, partial, external (ftp, etc.) • Image - JPEG, GIF • Video - MPEG format • Audio - Basic • Application • PostScript • octet-stream - general binary data consisting of 8-bit bytes Grant

29. X.400 • This is the OSI messaging standard • Uses a hierarchical addressing scheme • C = country • A= administrative domain (service provider) • P = private domain ( message transfer agent) • O = organization • D= Domain-defined attribute (e.g. Internet address) • PN= Personal name • Sample X.400 address • C: Canada, A:Sprint, P: Internet, O: McGill, D: grant@management.mcgill.ca, PN: Gerald Grant Grant

30. Electronic Data Interchange (EDI) • Computer-to-Computer exchange of routine business documents in a standard format • Routine business documents include • purchase orders, shipping notices, invoices, etc. • EDI replaces paper formats with their electronic equivalents Grant

31. Electronic Data Interchange (EDI) • All electronic exchange of data are not EDI • EDI information flows directly from computer application to computer application • A major goal and purpose of EDI is to improve the flow and management of business information • EDI information must be exchanged in a format that can easily be understood by the computer Grant

32. Benefits of EDI • Cost savings • Speed • Reduction of errors • Lower data entry costs • Decreased mailing costs • Reduction in order time • Lower inventory • JIT • Better cash management • Security Grant

33. EDI Standards • ANSI Accredited Standards Committee (ASC) X.12 • Cross industry standard used in North America • UN/EDIFACT - EDI for Administration, Commerce and Trade • Many other standards • Proprietary - between trading partners • Industry group e.g. transportation Grant

34. Components of EDI • Standards • X.12, EDIFACT, etc. • Hardware • Workstations, servers, mainframes • Software • EDI translation software to translate between standards and data formats • Communications • LAN, WAN, dial-up network using modems, etc. Grant

35. Value-added Networks (VANs) • Third party providers of EDI service • Reduces the investment in building EDI network • Allows multi-vendor connectivity • Increases the global reach of the network • Reduce usage costs • Allows offline processing • Provides translation service • Increases flexibility Grant

36. World Wide Web • Developed by Tim Berners Lee when he was at CERN (European Laboratory for Particle Physics • Popularized with the development of Mosaic - forerunner to Netscape, IE, etc. Grant

37. WWW configuration Grant

38. WWW configuration elements Grant