Reference Taken: Wikipedia

1. 13/08/2014
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Website
Web-Application
Defined by its Content.
Defined by its Interaction with the User.
Website consist of static content to its all visitors.
Web-application includes interaction & requires user- input & data-processing.
e.g., News-Site
e.g., Calendar
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Q. HOW CAN V DIFFERENTIATE Website & Web- application ????
An application software that runs in Web-browser.
They are stored on Web-Servers.
Tools Used:- Database, JavaScript, PHP
Well-known Example:- Google Docs , Social n/w (Facebook)
Features:-
To submit and retrieve data to/from a database over the web
Backup and easy access from anywhere
Free, others, shareware (pay a small fee)
Require only internet access and a web browser
No need to download and install software
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
PAS Model
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
1st Layer (Presentation) On the users side and consists of a basic browser
2nd Layer (Application)
Contains a dynamic content generation tool - such as Java, active server pages, or php
3rd Layer (Storage)
The data is stored & consists of back end database software
A Proxy Server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers.
A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity.
Proxies were invented to add structure and encapsulation to distributed systems.
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
A Proxy is a host which relays web access requests from clients.
Uses:-
 Used when clients do not access the web directly
 Used for security, logging, accounting and improving performance
Content filtering , Access control, Translation
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )

2. 13/08/2014
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Q. Why Web-Caching is used in Proxy- Server???
Storing copies of recently accessed web pages
Pages are delivered from the cache when requested again
- Browser caches
- Proxy caches
Shorter response time
Reduced bandwidth requirement
Reduced load on servers
Access control and logging
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Forwarding Proxy
A forward proxy taking requests from an internal network and forwarding them to the Internet.
In these proxies , the client server names the target server to connect to.
It is an Internet-facing proxy used to retrieve from a wide range of sources anywhere on the Internet.
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Open Proxy
An open proxy forwarding requests from and to anywhere on the Internet.
It is a forwarding proxy server that is accessible by any Internet user.
An anonymous open proxy allows users to conceal their IP address while browsing the Web or using other Internet services.
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Reverse Proxy
A reverse proxy taking requests from the Internet & forwarding them to servers in an internal network.
It is a proxy server that appears to clients to be an ordinary server.
Requests are forwarded to one or more proxy servers which handle the request.
The response from the proxy server is returned as if it came directly from the origin server, leaving the client no knowledge of the origin servers.
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
They are installed in the neighborhood of one or more web servers.
All traffic coming from the Internet and with a destination of one of the neighborhood's web servers goes through the proxy server.
There are several reasons for installing reverse proxy servers:-
Encryption / SSL acceleration
Serve/cache static content
Load-balancing
Compression
Security
Spoon feeding
Extranet Publishing
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Terminates the TCP connection before relaying to target host (in and out)
Hide internal clients from external network
Blocking of dangerous URLs
Filter dangerous content
Check consistency of retrieved content
Eliminate need for transport layer routing between networks
Single point of access, control and logging
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )

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Single point of failure
◦If the proxy dies, no one can get to the external network
Client software must usually be designed to use a proxy
Proxies must exist for each service
Doesn’t protect the OS
◦Proxies run at the application level
Create a service bottleneck
◦Solved via parallelism (more proxies, and load balance)
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Different Ways
Web-Proxy Servers
SOCKS proxy
Transparent proxy
CGI proxy
Anonymous HTTPs proxy
Suffix proxy
TOR(The Onion Router) onion proxy server
I2P anonymous proxy
DNS proxy
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
Not a true application layer proxy
SOCKS protocol provides a framework for developing secure communications by easily integrating other security technologies.
SOCKS includes 2-components:-
◦SOCKS server :- implemented at the application layer
◦SOCKS client:-implemented between the application & transport layers
Purpose of the Protocol:- To enable hosts on one side of a SOCKS server to gain access to hosts on the other side of a SOCKS Server, without requiring direct IP-reachability.
Copies packet payloads through the proxy
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
SOCKS Architecture
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )
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ADVANCED INTERNET TECHNOLOGY ( Subject Code: 730202 )