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Web Architecture. Server responds. Client makes requests. Client-Server Model. CLIENT (Often a Web browser ). SERVER. INTERNET. TIER 2: SERVER. TIER 1: CLIENT. Server performs all processing. Web Server Application Server Database Server. Two-Tier Architecture.

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client server model

Server responds

Client makes requests

Client-Server Model

CLIENT

(Often a Web browser)

SERVER

INTERNET

two tier architecture

TIER 2:

SERVER

TIER 1:

CLIENT

Server performs

all processing

Web Server

Application Server

Database Server

Two-Tier Architecture

This architecture is obsolete. Server does too much work.

SOURCE: FOURNIER

three tier architecture
Three-Tier Architecture

TIER 3:

BACKEND

TIER 2:

SERVER

TIER 1:

CLIENT

Application server

offloads processing

to tier 3

Web Server +

Application Server

Note: Using 2 computers instead of 1 can result in a huge increase in

simultaneous clients. Depends on % of CPU time spent on database access.

SOURCE: FOURNIER

n tier architecture
N-Tier Architecture

Optimized for

web page

delivery

Coded for

specific

application

Managed and

tuned by DBA

Achieves full separation of function and administration

Huge number of simultaneous clients

SOURCE: FOURNIER

intershop architecture
InterShop Architecture

SOURCE: INTERSHOP

connecting to legacy systems by wrapping

Wrapper

Middleware

Connecting to Legacy Systemsby “Wrapping”

“WRAPPER”

Web Server

MAINFRAME

Web

App

Legacy

App

connecting to legacy systems
Connecting to Legacy Systems

The “screen scraper”

Legacy system(mainframe)

Terminalscreen data

HTML data

HTMLdata

Screen scraper

Existing application

Legacy database

Web server

Client

SOURCE: WIM GEVERS

screen scraping
Screen Scraping
  • Some systems produce as their only output commands to 80 x 24 display terminals
  • Sequences of characters telling the terminal to move its cursor and display data, e.g. ^M0238Jan. ^M024416, ^M02482000displays “Jan. 16, 2000” in row 2, starting at col. 38
  • Screen scraping involves virtual simulation of the display terminal to retrieve the data
  • Vendors
    • Intelligent Environments
portal architecture

ERP

Client

CRM

Client

Office

Tool

Groupware

Client

Query

Tool

Web

Browser

Embedded Services

Partners

Employees

Customers

Content Directory

Applications

Web Tools

Text

Metadata

Client

Information

System

EnterpriseSystem

Document Repository

Groupware Database

DataWarehouse

Internet & Web

Portal Architecture

E N T E R P R I S E P O R T A L

SOURCE: PLUMTREE

portal architecture11
Portal Architecture

LOB = “LINE OF BUSINESS”

SOURCE: MIKE CRANDALL, GATES FOUNDATION

server farms

Router

Router

Web Servers

Server Farms
  • To serve many clients, one server is not enough
  • How do multiple servers cooperate?

Network Switch

Network Switch

Internet Firewall

Intranet Firewall

DB Servers

App Servers

SOURCE: ATESTO

server cluster server farm

Internet

Server Cluster (Server Farm)

Clients

HTTP request

Router

Request

Routing

Communication

Server farm

System

Management

SOURCE: CHU-SING YANG

server selection problem
Server Selection Problem

Server Farm A

Server Farm B

Which server?

  • Avoid scalabilityproblems of central servers bydistributing load

Which network site?

“Contact the weather service.”

SOURCE: JEFF CHASE

load balancing switch

subnet

subnet

Internet

Internet

Load Balancing Switch

client

http://pds.cse.nsysu.edu.tw/job/

Server Farm

Router

SVR.1

SVR.2

Web Switch

Virtual IP address

SVR.n

SOURCE: CHU-SING YANG

domain names
Domain Names
  • IP addresses are inconvenient to remember 128.2.218.2 v. euro.ecom.cmu.edu (fully qualified)
  • Domain names are alphanumeric aliases for IP addresses. They form a tree structure of FQDNs:

ROOT

.GOV .COM .MIL .NET .EDU .ORG .IT

CMU PITT MIT

AMAZON MCKINSEY YAHOO

208.216.182.15

207.237.113.94

GSIA CS ECOM HEINZ

WWW YEN EURO DOLLAR PESO

128.2.218.4

128.2.218.2

128.2.16.175

domain name system

client

Domain Name System
  • Large, distributed, worldwide database
  • Maps domain names to IP addresses

What is the IP address

of abc.foo.com?

Root DNS

202.168.14.12

.com DNS

Try .com

Try foo.com

foo.com DNS

Local DNS

Resolver

abc.foo.com is 202.168.14.12

+ Cache

SOURCE: CISCO SYSTEMS

slide18

URL-Based Load Balancing

  • Substring matching for:
    • “images”
    • “.gif”
    • “.jpg”

Load distributed within group via any standard metric or URL hashing

GET /www.foo.com/images/abc.gif

  • Substring matching for:
    • “.cgi”
    • “.bin”
    • “.exe”

GET/www.foo.com/event/reg.bin

GET /www.foo.com/product/abc.html

  • Substring matching for:
    • “.html”
  • Servers optimized for specific content-types
  • Substring match on URL directs HTTP requests to designated server farm
    • Load balancing using configured algorithm or,
    • URL Hashingforwards requests for each unique URL to same server to take advantage of server memory caching

SOURCE: SUN

dns round robin balancing
DNS Round Robin Balancing

SERVER

a

b

c

d

DNS server for

nhc.noaa.gov

“www.nhc.noaa.gov is

IP address a”

(or {b,c,d})

Idea: When an IP

address is requested

for nhc.noaa.gov,

return a different

IP address each time

CLIENT

“lookup

www.nhc.noaa.gov”

client network

DNS server

SOURCE: JEFF CHASE

slide20

Web Data Center

SOURCE: SUN

global wan architecture
Global WAN Architecture

Site II

losangeles.domain.com

Internet

Site I

newyork.domain.com

Router

DNS

BIG-IP

BIG-IP

Local DNS

GLOBAL-SITE

Webmaster

Site III

tokyo.domain.com

Server Array

User

london.domain.com

SOURCE: EDWARD CHOW

client and server side programming

Internet

Client- and Server Side Programming

Server

Client

HTML

CGI/Perl, C

Applets

ASP

ActiveX Controls

Servlet

Dynamic HTML

JSP

JavaScript

XML

SOURCE: IIT

tiers and urls
Tiers and URLs

URLs can be used for application routing

http: // 10.0.0.1 / catalog / display.asp ? pg = 1 & product = 7

Web

Server

Web app

DB

Web app

DB

Web app

Web app

SOURCE: NTOBJECTIVES.COM

php process flow
PHP Process Flow

Raw .php source

HTML is substituted for PHP code

PHP

Pre-

processor

Browser

Web

Server

HTML

.php

source

file

Internet

Request for .php file

PHP originally mean “Personal Home Page”

SOURCE: M. HAMILL

website components
Website Components

SQL Database

HTTP

request

(cleartext or SSL)

Firewall

Web

Client

Web

Server

Web app

DB

Web app

DB

Web app

Web app

HTTP reply

(HTML, Javascript, VBscript, etc)

  • Apache
  • IIS
  • Netscape
  • etc…
  • Plugins:
  • Perl
  • C/C++
  • JSP, etc
  • Database connection:
  • ADO,
  • ODBC, etc.

SOURCE: NTOBJECTIVES.COM

major ideas
Major Ideas
  • Client-server model
  • Three-tiered (n-tiered) architecture
  • Legacy connections
  • Portals
  • Server Farms
  • Web development tools
  • Client- and server-side tools
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