Great Circle Associates Firewalls
(December 1995)
 

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Subject: Filtering fragmented IP frames
From: Patrick Drolet <pdrolet @ CyberSecure . Com>
Date: Mon, 04 Dec 1995 16:18:05 -0500
To: firewalls @ greatcircle . com

Filtering IP frames is quite simple.
Filtering UDP/IP or TCP/IP frames seems quite simple...

The problem filtering TCP/IP is fragmentation; How does a firewall (or even a
Cisco Secure Router) manage to filter fragmented IP frames knowing that the
TCP or UDP header is only on the first frame ? 

Patrick.
.-------------.
| CyberSecure |
|-----------------------------------------------------------.
| Patrick Drolet, eng.   |                                  |
| pdrolet @
 cybesecure .
 com | Can your network keep a secret ? |
| (514) 289-8520         |                                  |
`-----------------------------------------------------------'




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