MIS 430 PART TWO: Network Fundamentals

1. MIS 430PART TWO: Network Fundamentals Chapter 2 Application Layer Chapter 2

2. Tech Focus 2-1 • Servers • Mainframe: 1,000s of users $million+ • Minicomputer: 100s of users $50k-400K • Sometimes DB servers in client-server nets • Microcomputer: 1 to many users, up to $30+K • Cluster: group of computers linked together to act as one computer • Shared resources • Load balanced • Scalable Chapter 2

3. Tech Focus 2-1, contd • Clients • Microcomputer: most common • Terminal: I/O only • Dumb: no processing of data; just KB and display • Intelligent: adds local processing, storage, printer • Workstation: CAD and technical modeling • Network computer: Java, no hard disk; limited • Transaction Terminal: specialized device like ATM, POS scanner, card swipe machine. Specific task. • Handheld – PDA or wearable (Xybernaut) Chapter 2

4. I. Application Architecture • Way functions of the applications layer are spread among servers and clients • Work functions of an application program • Data Storage DS • Data Access Logic DAL: work required to access data such as SQL queries • Application Logic AL (aka business logic) • Presentation Logic PL: formatting info to the user and accepting user commands Chapter 2

5. Host-Based Architecture • First developed in 1960s; see Fig 2-1 • Server (host) does PL, AL, DAL, and DS • Client is a terminal (or PC running terminal emulation SW) • Tight controls possible • Problems: cost is high, response can be slow, and scalability only comes in large chunks (e.g., like a mainframe) Chapter 2

6. Client-Based Architecture • LANs appeared in late 1980s; fig 2-2 • Server: DS (e.g., MISNT or Befac) • Client: PL, AL, DAL • PC-based SW is plentiful, easy to use • Problems: all data must travel from server to client, not just selected items, and controls are weak; more network traffic Chapter 2

7. Client-Server Architecture • Very common today; see fig 2-3 • Server: DAL, DS • Client: PL, AL • Server maintains the data and applications run on the client. • If you run out of capacity, get a new client • Server adjudicates requests for data • Banner is an example of this at ISU Chapter 2

8. Client-Server, contd. • Some application logic can be on server • Middleware: sits between server and client • Interprets and translates data • Manages message transfers (specific SW) • Allows multiple vendors to be involved • EX: CORBA, ODBC (Open Data Base Connectivity) to link computers Chapter 2

9. 3-Tier Client Server • Adds a 3rd application server in the middle as in fig 2-4 • Database server: DAL, DL • Applications server: AL (middle) • Client: PL • EX: DB server is mainframe holding data, AL server is a minicomputer running an app, and client is a PC Chapter 2

10. N-tier Client Server • Adds specialized servers; see fig 2-5 • DB server: DAL , DS • Application server: AL • Web server: AL • Client: PL • Requires a lot more network communications between servers • More difficult to program and test Chapter 2

11. Clients in Client-Server • Determines how much application logic is on the client end • Thin client: little or no application logic – AL resides on the server • Fat (thick) client: all or most AL on client • Thin clients are the way of the future • ASP (application service provider) • Access via browser and Java applets • Distributed computing model Chapter 2

12. Which Architecture? Chapter 2

13. II. World Wide Web • History: • CERN 1989 (hypertext concept) Angels and Demons? • Mosaic browser 1993 (U. Ill, Mark Andreessen thesis) • Netscape 1994 (left U. Ill to form this company) • Microsoft 1996 Internet Explorer • Others: Opera, Lynx (text), Web TV; embedded in printers, wireless routers, print servers, etc. Palm Tungsten C (mine!) Chapter 2

14. How the Web Works • Example of 2-tier architecture • Client needs browser (appl layer SW) • Server needs web server (IIS or Apache SW) • Process • User types URL: protocol, server, and file name • Browser sends HTTP request (request line, header, body); fig 2-9 • Server returns HTTP response (status, header, body); fig 2-10 • Status 200 means OK, 404 means Not Found • http://misnt.indstate.edu/bruce/ is not found • http://www.rexswain.com/httpview.html is a viewer of response from the web server – cool! Chapter 2

15. Web Identifying Information • This information about you appears whenever you request a web site • Your IP address • Browser and version • Date and time • Referrer URL • Destination URL • http://www.howstuffworks.com/web-server.htm Chapter 2

16. E-mail • The most heavily used Internet application! • Advantages over regular mail • Speed: seconds to a minute • Price: essentially free vs. $5+ for a letter or $15+ for overnight • Attachments are machine readable: MIME encoding • Send to multiple recipients at the same time • Disadvantages • Tacky: some don’t think it is “professional” • If one doesn’t check mail, it didn’t arrive! • Tasks longer to type than talk (but voice recognition) • Flame mail! • Easy to send something to the wrong person Chapter 2

17. How E-mail Works • www.howstuffworks.com/email.htm cool! • Outgoing mail • SMTP: Simple Mail Transport Protocol • Email client sends packet to SMTP server • Server reads destination and routes packets • Destination mail server puts in right mailbox • Incoming mail • POP: Post Office Protocol • Client requests message to be transferred to mail folders (probably on hard drive) • IMAP: Internet Message Access Protocol (GroupWise) Chapter 2

18. E-mail Headers (Underneath) • Received: from mailgate.indstate.edu • by isugw; Wed, 29 Aug 2001 09:14:46 -0500 • Received: from befac.indstate.edu ([139.102.15.23]) • by mailgate.indstate.edu (8.11.2/8.11.2) with ESMTP id f7TEFnb11406 • for <mfbjm@isugw.indstate.edu>; Wed, 29 Aug 2001 09:15:49 -0500 (EST) • Received: from BEFAC/SpoolDir by befac.indstate.edu (Mercury 1.48); • 29 Aug 01 09:14:46 utc-5 • Received: from SpoolDir by BEFAC (Mercury 1.48); 29 Aug 01 09:14:44 utc-5 • Received: from gideon.gprc.ab.ca (192.139.30.4) by befac.indstate.edu (Mercury 1.48) with ESMTP; • 29 Aug 01 09:14:38 utc-5 • Received: from gprc1.icn.gprc.ab.ca (gprc1.gprc.ab.ca [172.20.253.244]) by gideon.gprc.ab.ca with SMTP (Microsoft Exchange Internet Mail Service Version 5.5.2653.13) • id RSJPP6DP; Wed, 29 Aug 2001 08:14:11 -0600 • Received: from 32377 ([172.20.7.59]) by GPRC.AB.CA (PMDF V5.2-33 #37300) • with SMTP id <01K7P6PUT8FG8WW06I@GPRC.AB.CA> for mfbjm@befac.indstate.edu; • Wed, 29 Aug 2001 08:13:14 MST • Date: Tue, 28 Aug 2001 12:05:18 -0600 • From: ww <Diane.Kinderwater@GPRC.AB.CA> • Subject: Text • To: mfbjm@befac.indstate.edu • Message-id: <000a01c13095$b77f05e0$3b0714ac@gprc.ab.ca> • MIME-version: 1.0 • X-MIMEOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 • X-Mailer: Microsoft Outlook Express 5.50.4133.2400 • Content-type: multipart/alternative; • boundary="----=_NextPart_000_0007_01C12FB9.B497FF80" • X-Priority: 3 • X-MSMail-priority: Normal Chapter 2

19. 3-Tier E-mail • Use browser to get mail; see fig 2-12 • Replace email client with web browser • Load mail web page • Request/send email • Browser sends HTTP request to middle tier web server • Web server requests info from email server • Process reverses, mail sent as HTML file Chapter 2

20. ISU E-mail Mess! • Eudora, Outlook Express, Netscape Messenger e-mail clients • HTML mail (Hotmail, Yahoo, Juno, etc) • Portal (http://myisu.indstate.edu) • Username@mymail.indstate.edu is primary student email • Username@citrine went away • GroupWise (mail,calendar,tasks,shared data) • Groupwise Client (full featured, fast) • WebAccess client (convenient, slow, few features) • Portal client => to GroupWise (compromise) • Groupware: Outlook (Exchange), Lotus Notes • Sept 1: Befac, Root, Scifac servers disappear! Chapter 2

21. Discussion Groups • E-mail based • Subscribe to discussion group • To: listproc@lists.indstate.edu • Subscribe mis430-L firstname lastname • Send mail to group • To: mis430-L@lists.indstate.edu • Redirected to all members of list • Archive history is optional to follow threads • Caution! Reply defaults to everyone in group • Hint: may need to turn off HTML e-mail & signature because of extra words that are misinterpreted as commands Chapter 2

22. Discussion Group Commands • Each list processor is different, but many use common commands to • Get information on commands (help) • Join/leave (subscribe and unsubscribe) • See who is a member of a list • See class handout for Listproc commands at ISU • http://web.indstate.edu/it/tech-supp/docs/listproc.htm Chapter 2

23. III. Other Applications • FTP – File Transport Protocol • FTP:// is similar to HTTP:// protocol • FTP client sends request to FTP server • WS_FTP, CuteFTP GUI clients • Anonymous FTP vs. closed FTP (with authentication) • SDSNT and hackers: anonymous FTP allowed initially with write access – ugh! Chapter 2

24. Other Applications, contd. • Telnet: log on as terminal over the Internet • Much less popular for end users now – more go through web pages • Experts can connect to router or switch to program it • Instant Messenger: AOL and MSN • 3-tier system: your client sends message to • IM server that redirects it to another IM client • Microsoft has its own new Live Communications Server system - is IM a legitimate corporate tool? Chapter 2

25. Other Applications • Videoconferencing (fig. 2.14) • Real-time audio and video over Internet • MS NetMeeting is popular • H.320 and H.323 protocols • Webcasting • One-way videoconferencing • RealPlayer and MS Media Viewer popular • WebEx http://webex.com/for demo • Bandwidth is key for both! • 28.8k, 56k, 128k, 300k, faster Chapter 2

26. Mgt Focus 2-3: Alabama ADRS • ADRS has 800 employees in AL serving patrons all over the state • Uses IP H.323 videoconferencing to save travel costs • Ex: Weekly 90-minute meeting attended by videoconference instead of driving 100 mi. • IP saves money over previous ISDN dialup connection Chapter 2