MIS 430 PART TWO: Network Fundamentals

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Oct 31, 2013 (3 years and 9 months ago)

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Chapter 2

1

MIS 430

PART 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 3
rd

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?

Host
Based

Client
Based

Client
Server

Infrastructure
$

High

Medium

Low*

Development
$

Low*

Medium

High

Scalability

Low

Medium

High*

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

1.
User types URL: protocol, server, and file name

2.
Browser sends HTTP request (request line,
header, body); fig 2
-
9

3.
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


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-
5


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29 Aug 01 09:14:38 utc
-
5


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(Microsoft Exchange Internet Mail Service Version 5.5.2653.13)



id RSJPP6DP; Wed, 29 Aug 2001 08:14:11
-
0600


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-
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


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MIMEOLE: Produced By Microsoft MimeOLE V5.50.4133.2400


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-
Mailer: Microsoft Outlook Express 5.50.4133.2400


Content
-
type: multipart/alternative;



boundary="
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-
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