Proxy and Firewalls - same ?
This is a topic that often leads to a great amount of confusion, primarily because a firewall and a proxy often perform many of the same functions. For instance, they both act as network gateways, separating your Local Area Network (LAN) from the outside world. This placement allows them to examine all incoming traffic and discard any unrecognized data before it can make it onto your network, thereby protecting the network from attack. In many cases, a firewall and proxy will even reside on the same server. Yet in spite of these similarities, the roles of these two devices are actually quite different.
Basically, the primary role of a Firewall is to protect your network from unauthorized access. In order to do this, firewalls use numerous techniques to regulate which services can travel through the network. These services operate over TCP and UDP ports. The firewall uses "Rules" to open and close the ports that these services travel on. Firewalls also use of a number of different detection techniques to protect against attacks, including Network Address Translation (NAT), MAC address filtering and Stateful Packet Inspection (SPI).
Firewalls can take advantage of different encryption methods as well. This allows mobile users to tunnel into the network from remote locations through the use of secure logon procedures and authentication certificates. Firewalls have the ability to generate automatic alarms at given thresholds of attack and also have extensive logging and reporting capabilities.
One of the firewall's potential drawbacks is that it allows network users to surf the web unrestricted. Any web page that is requested by the client is automatically accessed and retrieved without regard to content or appropriateness.
This brings us to the proxy server. Unlike a firewall, the primary role of the proxy server is to limit a user's ability to access sites or materials that might be deemed inappropriate within a corporate environment. A proxy will intercept all web requests coming from network clients and check them against the contents of its Access Control List (ACL). Entries in the ACL can be in the form of domain names, individual pages, specific words, or categories (e.g. sex, violence). If the web page requested is not on the proxy server's ACL, the request is processed normally and the retrieved web page is sent back to the requesting client. If, however, the requested web page is on the ACL, it will be blocked, and the client will receive a message indicating they have tried to reach a restricted site.
Proxy servers are not foolproof, but they do provide companies with a greater level of control than that of unrestricted terminals. Proxy servers are most effective when used in conjunction with a strong Acceptable Use Policy (AUP) that addresses what material is and isn't appropriate to access, and what the consequences will be if the terms and conditions of the AUP are violated.
A proxy server can also improve your network's performance by functioning as a caching server (Definition). Proxy servers can be difficult to maintain and troubleshoot, which is why they are typically only found in large organizations with a good size IT staff.
In summary, the role of a firewall is to protect your network from unauthorized intrusion, while a proxy server has more to do with restricting the type of information that users on your network will be allowed to access. Proxy servers can also be configured to function as a firewall, but they are much more difficult to maintain. As far as which is the right choice for you, I'm afraid that you are the only one qualified to make that determination. Best of Luck!
Source : http://www.practicallynetworked.com/qa/qa20030313.shtml
