DYNAMIC NETWORKS

• HTTP & FTP PROXY SERVERS

• Group 20:• AMEET G• BHUJANG R• KAUSHIK N• PRAMOD M

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CONTENTSIntroduction to proxy servers – Ameet G

(Slides 3 to 12)

FTP and FTP proxy servers – Pramod M

(Slides 13 to 23)

HTTP and HTTP proxy servers – BhujangR

(Slides 24 to 30)

Demo – Kaushik - AllegroSurf

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PROXY SERVER

WHAT IS PROXY SERVER??• The word proxy means "to act on behalf of

another" and a proxy server acts on behalf of the user.

• All requests from clients to the Internet go to the proxy server where it evaluates the request, and if allowed, re-establishes it on the outbound side to the Internet.

• Both client and server think they are communicating with one another, but, in fact, are dealing only with the proxy.

Proxy server layout

How proxy server works?

Aims of proxy server Privacy – It hides the ip of the client and

shows the ip of the proxy server. Caching of requests. Bypassing content blocks –Client can

get around the blocked sites by admin. Web browsing access. Usage monitoring – The proxy detects

the traffic occurring in it and monitor’s the clients.

Snippets Proxy Servers are in the format xxx.xxx.xxx.xxx:xxx where xxx is any numeric digit. They are in the form of an IP with a Port.

Also if your Internet Service Provider has blocked any sites like Orkut or MySpace you can bypass the firewall using proxy servers.

Proxy servers help hop over your local or wireless network restrictions.

Types of proxy servers(based on function) Cache proxy – Speed up internet access. Web proxy – To connect user to server and

use internet. Anonymizing proxy – To spoof your ip

address and surf. Forced proxy – Force the user to go through

proxy (used in companies). Transparent & Non-transparent proxy.

Caching in case of dynamic-web pages

• Web pages maybe static or dynamic.

• In case of dynamic pages we add headers which contain time and date of the page and re-request if necessary.

• Another is add a max time in the header till which the page is valid and re-request the server.

Load Balancing• Load balancing helps

make networks more efficient by distributing the processing and traffic evenly across network, making sure no single device is overwhelmed.

• Increased scalability• High performance• High availability and

disaster recovery

Disadvantage of using proxy! Proxy service lag sometimes behind the

non- proxied services. Proxy services may require different

servers for each service. Proxy services require certain

modifications to be made on clients. Proxy servers do not protect from

protocol weakness.

FTP and FTP PROXY SERVERS

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WHAT IS FTP?? FTP refers to a network protocol responsible for

transferring files from one computer to another over a TCP computer network or the Internet.

FTP helps users to upload web page files (simple text files, images, multi-media files, etc.) from their personal computers to the server.

A FTP is a client-server model type.

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AIMS of FTP

The aim of FTP protocol is to: Allow file sharing between remote

machines thus promoting indirectly ‘remote login’.

Allow independence between client and server machine system files.

Enable efficient data transfer.

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HOW DOES FTP WORK ?

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•The File Transfer Protocol (FTP) is defined by the RFC959 based on the FTP Model as illustrated. •The FTP uses two TCP/IP connection channel, i.e., control connection and data connection between the User and the Server.

CONTROL & DATA CONNECTIONS

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•The control connection is a full duplex communication path between Server and User for exchanging commands and replies . •The FTP uses the Telnet protocol for the control connection

•Data connection is a full duplex communication link through which data (file) are transferred between Server and User on a specified type and mode. •The data connection is established for dataor file transfer on demand temporally

CONTINUED…

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•There are two modes of operation namely Active mode and Passive mode.•FTP handles two types of data conversions and representations namely ASCII and Binary data.•FTP has a number of commands for transferring the files.

More about FTP….• Ftp uses port 20 for data and port 21 for

control connections respectively.• It was implemented first in 1971 in MIT then

defined in RFC141 now defined by RFC959.• FTP is an indirect use of network application.• Improved versions of FTP are FTPS, TFTP,

SFTP, FXP.• Web browsers utilize FTP protocol to talk to

FTP servers directly. A CERN-type proxy avoids the complexities of proxying the FTP protocol by talking to a Web browser via HTTP while talking to an FTP server via FTP.

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Security concerns.. Filter the IP address

of the unregistered users.

Use the alias technique to prevent login by others.

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FTP servers• Fig- Reverse FTP

proxy.• FTP servers host the

files which are necessary for clients.

• Clients are those who request for files by their identity to the server through application programs installed in them.

• Now browsers connect to servers via URL’s also.

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FTP via proxy servers

The client sends authentication information first to the proxy, tell the ftp server name and then the proxy connects the FTP server and resends the login information to the FTP server.

Another way is the CERN server talking both the languages of http to client and ftp to the server.

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Disadvantages of FTP• Passwords and file contents are sent in

clear text over the Internet.• It is hard to filter FTP traffic using a firewall

since the data connection is made to an arbitrary port on a client computer.

• It is possible to tell a server to send data to an arbitrary port of a third computer.

Despite these disadvantages, the FTP is and will likely remain one of the most popular protocols on the Internet.

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HYPER TEXT TRANSFER PROTOCOL

(HTTP)HTTP – A medium of communication between a

client and server for mutual exchange of resources.

Versions – HTTP 1.0 HTTP 1.1HTTP deals with the transfer of data contained in

files along with resources* to and from the server and client.

HTTP Client – Web BrowserHTTP Server – Web ServerStandard Port - 80

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Like the FTP model the HTTP also follows the client-server model.The HTTP client requests a method to be catered to and the HTTP server replies with the resources , requested. Once this single cycle is completed the process comes to an end.The format of request and response messages are similar and comprise of :1)Initial Line2)Header Line/s3)Blank Line4)Message Body

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CONTINUED

Initial Request Line - The request usually comprises of the GET method (Get a resource).

It comprises of the path to the URL or the request URI followed by the HTTP version x.x

It is also called as the status line.Header Line – The header contains more

information about the request and response ie the object being sent in the message body.

Message Body – Comprises of the data requested for transfer or a suitable message.

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HTTP 1.1

HTTP 1.1 is an upgrade to 1.0 Some of the upgraded features

(1) Faster in terms of response time.

(2) Reliable.

(3) 100 continue response.

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HTTP PROXY SERVER

Deals about the proxy settings for a HTTP protocol.

Not realized at the operating system level.

Processes have to be manipulated to employ the principles of proxy.

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GOALS

A proxy server designed to handle HTTP protocols are called HTTP PROXY SERVERS

The meta data involved in the tranfer of HTML pages are handled.

Step up in the speed of transmission.

Authentication via SSL methods.

Reduces redundancy in data transmission

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BUILDING PROXY SERVERS

Multithreaded proxy servers are by far the latest form of a proxy server.

Question ? What are/is the function of a proxy server.

~END~

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THANK YOU

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