Firewalls: High Port No's

Firewalls
(April 1995)

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Subject:	High Port No's
From:	Paul Crossley <paul @ toploguk . co . uk>
Date:	Tue, 11 Apr 1995 15:41:22 +0100 (BST)
To:	firewalls @ greatcircle . com

I still seem to have a bit of a hole in my understanding of how TCP/UDP
port No's are used.

I have been selectively filtering certain protocols such that I am allowing
replies to ports 1024-5999 whenever the source port is OK.

I have now discovered that netscape on SUN's will generate a random port
such as 33675 - rather above my accepted range.

Can some kind subscriber give me the official line on how these ports
are generated (I assume there must be guidelines that developers should
adhere to) so that I can modify my filtering strategy.

I guess there must be an RFC for this somewhere.

 
Regards
P Crossley


-------------------------------------------------------------------------

Paul Crossley            (paul @
 toploguk .
 co .
 uk)      
Senior Consultant              SCO ACE               
TopLog Limited                                        
TopLog House, Knaves Beech Business Centre, Loudwater, Bucks. HP10 9QY
Phone (01628) 819444  Fax (01628) 819356
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