Proxy servers operate as an intermediary between a local network and services available on a larger network like the Internet. They improve performance by caching frequently requested web pages and filtering requests to prevent access to certain sites or protocols. The main types of proxy servers are caching proxy servers, web proxy servers, content-filtering web proxy servers, and anonymizing proxy servers.

1. Proxy Server

2. PROXY SERVER
Proxy servers operate as an intermediary between
a local network and services available on a larger
one, such as the Internet
• Proxy share a connection to others
• Proxy act as gateway
• Proxy act as Cache Server/Firewall
6

3. Purpose of Proxy server
 Improve Performance
 Act as Cache server
 Cache web pages & provide them back without requesting
the page again from website server.
Bandwidth control
 Reduces the Bandwidth requirements for an large
Organization.
Filter Requests



Prevent access to some web sites!!!
Prevent access to some protocols
Prevent access of network on Time
Basis. Surfing
Anonymously Browsing the WWW without any identification!!!  


4. TYPES OF PROXY SERVERS
4
•
•
•
•
Caching proxy server
Web proxy server
Content-filtering web proxy
Anonymizing proxy server

5. Main purpose of using proxies
 Improve Performance
 Act as Cache server
 Cache web pages & provide them back without requesting
the page again from website server.
Bandwidth control
 Reduces the Bandwidth requirements for an large
Organization.
Filter Requests



Prevent access to some web sites!!!
Prevent access to some protocols
Prevent access of network on Time
Basis. Surfing
Anonymously Browsing the WWW without any identification!!!  


6. Improving Performance
Caching can greatly speed up Internet access. If one or more Internet sites
are frequently requested, they are kept in the proxy's cache, so that when a
user requests them, they are delivered directly from the proxy's cache
instead of from the original Internet site.
Caches diminish the need for network bandwidth, typically by 35% or more,
by reducing the traffic from browsers to content servers.
 Bandwidth control
– Policy-based Bandwidth Limits
– Deny by content type
INTERNET
64
Kbps
128
Kbps
512
Kbps 1 Mbps
 Caching
 Reduces latency (Sites takes
less time to open)
Reduces Network Traffic
( Reduces Data uses)


7. MECHANISM OF PROXY
SERVER
client ISP
www.abc.com
Block
www.xyz.com
10
www.abc.com
www.xyz.com
Proxy server
www.abc.com

8. MECHANISM OF PROXY
SERVER
8
 Proxy server accepts request from client.
 It generates response based on two conditions.
 If the document exits in the local cache, proxy
server itself provides the required retrieval to the
client.

9. MECHANISM OF PROXY
SERVER
9
 If there is a cache miss then the request is been
forwarded to the original server.
 The proxy server transfers the replies to the
client and also being caches them.
 The proxy server thus acts both as the client and
the server.

10. LAN
IP : 172.16.0.1
Proxy Server
INTERNET
IP : 217.219.66.2
Gw : 217.219.66.1
IP : 172.16.0.2
Gw : 172.16.0.1
Source IP
172.16.0.2
www.yahoo.com
Dest IP
209.191.93.52

11. LAN
Proxy Server
INTERNET
IP : 217.219.66.2
Gw : 217.219.66.1
IP : 172.16.0.2
Gw : 172.16.0.1
IP : 172.16.0.1
Source IP
217.219.66.2
www.yahoo.com
Dest IP
209.191.93.52
Change Source IP Address
Source IP
172.16.0.2
www.yahoo.com
Dest IP
209.191.93.52

12. LAN
INTERNET
IP : 172.16.0.1
Proxy Server
IP : 217.219.66.2
Gw : 217.219.66.1
Source IP
209.191.93.52
Dest IP
217.219.66.2
Change Source IP Address
& Destination IP Address
IP : 172.16.0.2
Gw : 172.16.0.1

13. LAN
IP : 172.16.0.1
Proxy Server
INTERNET
IP : 217.219.66.2
Gw : 217.219.66.1
Source IP
209.191.93.52
Dest IP
217.219.66.2
Change Dest. IP Address
Source IP
209.191.93.52
Dest IP
172.16.0.2
IP : 172.16.0.2
Gw : 172.16.0.1

14. LAN
IP : 172.16.0.2
Gw : 172.16.0.1
Source IP
209.191.93.52
Dest IP
172.16.0.2
IP : 172.16.0.1
Proxy Server
INTERNET
IP : 217.219.66.2
Gw : 217.219.66.1

15. HTTP PROXY SERVERS
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 "Middlemen" between clients and servers

Proxies which process http requests are
known as http proxy servers
Proxy
Server
Looks like a server
sending responses
Looks like a client
making requests

16. KEY FEATURES OF HTTP PROXY
SERVERS
16
 It may rewrite the client’s requests
 It Provides Anonymity and Security
 It is a Caching Proxy server
 Serves as content filter

17. ADVANTAGES
OF HTTP PROXY SERVERS
17
 Better Performance
 Less trafficking
 Reduces latency
 Conserves bandwidth
 Good at logging

21. DNS

22. What DNS do?
Convert user friendly names to user-unfriendly
strings of long arbitrary number.
Simply put convert Domain names to IP addresses
and back.
http://www.bsnl.co.in.
◦ http:// - protocol that is used
◦ www – browsing service
◦ ‘.’ at the end root domain
◦ co.in - Top level domain (TLD)
◦ bsnl – second level domain

23. hosts file
Earlier the name service was done using a local file inside
every computer
◦ hosts file
◦ /etc/hosts in *nix
◦ %systemroot%system32driversetchosts in windows
It is tedious task to update this file every time a change
occurs

24. Domain Name Space Hierarchy
DNS is organized in a hierarchical tree
structure
◦ Domain Root
◦ Top-Level Domain (TLD)
◦ Second Level Domain
◦ Sub domain
◦ Host or resource

25. FQDN (Fully Qualified Domain Name)
jacob.hr.microsoft.com
◦jacob – hostname
◦hr – sub domain
◦microsoft – second level domain
◦.com-TLD

26. DNS Hierachy
Root
.com/co.
google.
Mail Drive maps
Yahoo Bsnl
Rttchyd Rttctvm Alttc
DC
.gov
kerala
.mil .edu .int .net
Root domain
TLD
Secondary
Subdomain
Host
dc.alttc.bsnl.co.in(FQDN)

27. Types of DNS servers
•Primary
•Secondary
•Cache only

29. FTP

30. FTP
FTP, short for"File Transfer Protocol," can transfer
files between any computers that are networked.
It is platform independent
Works in client server architecture
Can be Open or restricted with username and
passwords

31. Email

32. Email
Method of electronically sending messages.
Store and Forward System.
Multiple Copies on one go.
Can include acknowledgements.
Requires a mail account to operate.
Mails are available globally.

33. Email address
•Two parts
–Separated by @
–eg. username@domain-name
–Domain refers to the mail server
–Username refers to the unique ID of the user
–domain name consists of a dot (".") followed by three or
more letters (such as .com and .gov) that indicate the
top-level domain (TLD) which indicates the type of
organization or the country where the host server is
located.

35. Protocols
SMTP
◦ Simple Mail Transfer Protocol, Port No. 25
POP3
◦ Post Office Protocol version 3, Port No. 110
IMAP
◦ Internet Message Access Protocol, Port No. 143

36. POP or IMAP

37. Components of Email
• Header
– Date, Time, From, To, CC, BCC, Subject
• Body

38. HTTP server
A web server is a computer system that processes
requests via HTTP to distribute information on the
World Wide Web.
The primary function of a web server is to store,
process and deliver web pages to clients.
The Pages delivered are most frequently HTML
documents, which may include images, style sheets
and scripts in addition to text content.
Eg of http server : IIS, Apache, nginx..