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What's the difference between proxy and firewall? And can we integrate a nat or pat into a proxy or firewall?

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A Proxy Server is a device that:

acts as an intermediary for requests from clients seeking resources from other servers.

A Firewall is a device that is:

designed to permit or deny network transmissions based upon a set of rules

The former just lets all traffic through regardless of source or destination and is a way of routing requests through known gateways and is often used to allow companies to log network traffic for example.

A proxy may include a firewall as part of it's functionality but it doesn't have to.

I would expect that Network Address Translation (NAT) and Port Address Translation (PAT) - which is basically the same thing - would be functionality that could be built in, but NAPT is more used on routers etc. to:

However it is common to hide an entire IP address space, usually consisting of private IP addresses, behind a single IP address (or in some cases a small group of IP addresses) in another (usually public) address space.

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ok! can we integrate a nat/pat into a proxy or firewall? – samia May 9 '11 at 20:59
@samia - probably, but I'm not sure what "pat" stands for. – ChrisF May 9 '11 at 21:00
@Chris - pat is port address translation. – Matt May 9 '11 at 21:04
@Matt - cheers. – ChrisF May 9 '11 at 21:04
@Chrisf (Port Adress Translation) like a nat(Network @ Transltion) used to associate a public adress to private ones to allow access on internet! becoz in our machines we have private @ and to access internet we need a public one!!! That's why a nat/pat are used for ;) – samia May 9 '11 at 21:05
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Proxies are used explicitly, for example a browser is configured to forward http requests to a proxy. A firewall is used implicitly, for example to drop some network connections. NAT works at the network level. NAT uses the same mechanisms as a stateful firewall to let a few machines appear with a single external IP address. Conceptually that makes NAT closer to a firewall. On the other hand the fact that a NAT rewrites packets (changing ports and addresses) is similar to a proxy changing ports and addresses and adjusting headers before relaying a request.

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thank u! How to make an internal or a private network more secure, efficient and functional? Do we have to configurate all these equipmnt : PAT/NAT,Proxy,Firewall...??? – samia May 9 '11 at 21:32
Not all proxies are explicit. Consider the transparent proxy. Clients are not configured to use it, but their traffic is routed through it. – Xenoactive May 10 '11 at 2:50
@Xenoactive This kind of thing needs a different name. The HTTP spec defines proxies as used explicitly, and transparent proxies as proxies that don't alter the requests at all. – Tobu May 10 '11 at 7:53
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And can we integrate a nat or pat into a proxy or firewall?

Yes, Microsoft's Threat Management Gateway (TMG) is an example of a proxy & firewall wrapped into one.

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Hi uSlackr - could you revise answer to explain the differences? – Matt May 9 '11 at 21:03
My answer is to the second part of his question. They can be integrated. – uSlackr May 10 '11 at 0:33
good point, I will change the vote. – Matt May 10 '11 at 17:09

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