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proxy firewall and this scenario from Forouzan Book


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#1 zillah

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Posted 06 June 2006 - 12:39 PM

I have got this scenario from Forouzan Book "Data Communications and Networking" 3ed

CODE
http://highered.mcgraw-hill.com/sites/0072515848/student_view0/chapter31/powerpoint_slides.html


He says in page 851 :

"When the user client process sends a message, the proxy firewall runs a server process to receive the request. The server (I said it is the HTTP proxy )opens the packet at the application level and finds out if the request is ligitimate. If it is, the server acts as a client process and sends the message to the real server (I said it is the HTTP Sever) in the corporation. If it is not, the message is dropped and an error message is sent to the external user. Figure 31.11 shows a proxy firewall implementation".

CODE
http://img234.imageshack.us/img234/1307/proxyfirewallforouzanch310bc.jpg





1- Is the proxy firewall always standalone device ?

2- If the proxy firewall can investigate (check ) the application layer by itself , why do I need to send the packet to the HTTP proxy ?

Edited by zillah, 07 June 2006 - 07:58 AM.


#2 Nebon

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Posted 07 June 2006 - 06:25 AM

To answer your first question:

QUOTE
A proxy device (running either on dedicated hardware or as software on a general-purpose machine) may act as a firewall by responding to input packets (connection requests, for example) in the manner of an application, whilst blocking other packets.


As you can see it can be software aswell as hardware.

#3 zillah

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Posted 07 June 2006 - 07:49 AM

Thanks Nebon

QUOTE
To answer your first question:

What about second question
QUOTE
2- If the proxy firewall can invistage (check ) the application layer by itself , why do I need to send the packet to the HTTP proxy ?


#4 Nebon

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Posted 17 June 2006 - 08:26 AM

Im not so sure on that, maybe we will wait for an expert to come along.