Firewalls and Proxies Explained
Table of Contents
A Proxy is a central machine on the network that allows other machines
in that network to use a shared Internet connection. Proxy servers are
intermediate servers which accept requests from clients and forward them
to other proxy servers, a source server, or service the request from their
own cache. The proxy is also called 'server' or 'gateway'. Proxy allows
users on a network to browse the Web, send files over FTP, and work with
E-mail and other Internet services.
A Firewall Proxy provides Internet access to other computers on the
network but is mostly deployed to provide safety or security. It controls
the information going in and out the network. Firewalls are often used
to keep the network safe and free of intruders and viruses. Firewall proxy
servers filter, cache, log, and control requests coming from a client. A
firewall proxy is one that is used for restricting connections from a
proxy to the outside world or to the source server inside of the LAN. This
is different from a conventional firewall, in that a conventional firewall
restricts connections coming from the outside world.
How the Proxy Works
Simply put, proxy are gateway applications used to route Internet and
web access from within a firewall. Proxy servers work by opening a socket
on the server and allowing the connection to pass through. There is often
only one computer in a company with direct Internet connection. Other
computers have access to the Internet using that computer as gateway.
A proxy basically does the following:
- Receives a request
from a client inside the firewall
- Sends this request
to the remote server outside of the firewall
- Reads the response
- Sends it back to the
Usually, the same proxy is used by all of the clients on the network.
This enables the proxy to efficiently cache documents that are requested
by several clients.
SOCKS4 or SOCKS5 Proxy?
In a SOCKS network, all network application data flows through SOCKS,
enabling SOCKS to collect, audit, screen, filter and control the network
data, and create a network application data warehouse.
It is recommended to use SOCKS5 proxy with PostCast Server. SOCKS4 performed
three functions: connection request, proxy server setup and application
data relay. SOCKS5 brings authentication to the table. With authentication,
SOCKS5 adds two messages. SOCKS5 makes configuring clients easier and
includes support for UDP and TCP applications such as SNMP and audio/video
applications such as RealAudio. It supports communications among networks
with different IP addressing schemes, and supports authentication and
Tunneling allows users to perform various Internet tasks despite the
restrictions imposed by firewalls. This is made possible by sending data
through HTTP (port 80). Additionally, Tunneling protocol is very secure,
making it indispensable for both average and business communications.
SSL (Secure Sockets Layer) tunneling protocol allows a web proxy server
to act as a tunnel for SSL enhanced protocols. The client makes
an HTTP Request to the proxy and asks for an SSL tunnel. A Tunneling Proxy
operates on port 443.
- Microsoft's Internet
- WinGate 3.0
- Firewalls and Proxies