client-server architecture and the web -...
TRANSCRIPT
Client-server architecture
and the Web
Laura Farinetti
Dipartimento di Automatica e Informatica
Politecnico di Torino
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Web general architecture
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Internet
LAN
Client
Web & authentication server(s)
Transaction server(s)
Database server(s)
ISP
ISP
Distributed systems
Software systems in which components located on networked computers communicate and coordinate their actions by passing messages ◦ The components interact with each other in order
to achieve a common goal
◦ Three significant characteristics are: concurrency of components, lack of a global clock, and independent failure of components
Two main models ◦ Client-server architectures
◦ Peer-to-peer architectures
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Distributed systems
Originally referred computer networks where individual computers were physically distributed within a geographical area
Today used in a much wider sense, even referring to autonomous processes that run on the same physical computer and interact with each other by message passing
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node
applications local
archives
users
node
applications node
applications
Client-server model
Distributed application structure that assigns tasks or workloads between
◦ The providers of a resource or service, called servers
◦ The service requesters, called clients
Servers are classified by the services they provide
◦ E.g., a web server serves web pages, a file server serves computer files
Clients and servers exchange messages in a request-response messaging pattern
◦ The client sends a request, and the server returns a response
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Client-server vs peer-to-peer
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Three-tier architecture
Client–server architecture in which
◦ user interface
◦ functional process logic ("business rules")
◦ computer data storage and data access
are developed and maintained as independent modules, most often on separate platforms
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Web applications workflow
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User
User interface
+ client-side processing
Server-side
processing
Data
source
User sends a
request through a
user interface
The request is
sent to the
server
The application replies
to the request (possibly)
using the data source
The data source
returns the request
result
The server-side
application returns
the request result
The request result
is shown to the
user
Interaction example
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User interface
Result
Static transaction
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Client
Web
server Internet
URL http request
HTML
files
http response display
page
TCP/IP
path
browser server file system
HTML
send
Static transaction: timeline
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Browser
Web
server
Disk
access
t0
t1
t2
t3
t4
t6
t7
t8
t9
t5
t’0
t’1
total response time
server response time user think time
network transfer time
Dynamic transaction
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Client
Web
server Internet
URL http request
& POST data
http response display
page
TCP/IP
com-
mand
browser server application
HTML
send
Application
para-
meters
logic
Dynamic transaction: timeline
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Browser
Web
server
Application
server
t0
t1
t2
t3
t5
t6
t7
t8
t9
t4
total response time
application time
total server time
t’0
t’1
Database transaction
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Client
Web
server Internet
URL http
& POST
http display
page
TCP/IP
com-
mand
browser server application
HTML
send
Application
para-
meters
database
data
Database
query
Database transaction: timeline
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Browser
Web
server
Application
server
Database
server
t0
t1
t2
t3
t5
t6
t7
t8
t9
t4
t’0
t’1
total response time
application time
total server time
database time
Web technologies and languages
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Client-side technologies
Server-side technologies
Web technologies and languages
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HTML + CSS (static pages only)
+ JavaScript
Ruby on Rails
SQL
Example: EasyPHP
EasyPHP is a WAMP package including ◦ the web server Apache
◦ a the server-side PHP interpreter
◦ the SQL server MySQL
◦ development tools such as the database manager PhpMyAdmin
WAMP = Windows, Apache, MySQL, and PHP
EasyPHP installs all sotware required to develop a web site locally (no internet connection required) ◦ the PC becomes client and server
◦ virtual domain (localhost) -> http://127.0.0.1
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Web technologies and languages
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HTML + CSS (static pages only)
+ JavaScript
PHP
MySQL
EasyPHP
Licenza d’uso
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