Great Circle Associates Firewalls
(December 1992)
 

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Subject: Firewalls Digest V1 #48
From: phr @ napa . Telebit . COM (Paul Rubin)
Date: Sat, 12 Dec 92 02:13:23 PST
To: Firewalls @ GreatCircle . COM
Cc: Firewalls-Digest @ GreatCircle . COM
In-reply-to: Firewalls-Digest-Owner @ GreatCircle . COM's message of Sat, 12 Dec 92 01:00:06 PST <9212120900 . AA12995 @ mycroft . GreatCircle . COM>

>From: Brent Chapman <brent @
 GreatCircle .
 COM>
>Date: Fri, 11 Dec 92 10:17:37 -0800
>Subject: Re: Firewalls Digest V1 #42 
>
>phr @
 napa .
 Telebit .
 COM (Paul Rubin) writes:
>
># I hope this list's readers don't mind my plugging the product I work
># on, but the Telebit NetBlazer can filter on all these parameters
># except for source port.  We will probably add a source port parameter
># to a future release.  We *do* listen to what users ask for.
>
>AND except for the fact that the NetBlazer reorders and recombines the
>rules in the filters something awful.  In every release I've tried so
>far, there have been bugs in this procedure, and the NetBlazer has
>converted what should be a working rule set into an not-working pile
>of spaghetti.

I hope this doesn't turn out to be a case of "open mouth-insert
foot", but I believe that the current implementation works correctly.
Previous versions were unclearly specified and the implementation was
more complicated than the current one.

I still don't understand why anyone would want to change the order of
the filters to something other than most-specific-first.  By
comparison, the routing tables are most-specific-first and nobody has
complained.  The example in "Network (In)security..." can easily be
done correctly with most-specific-first order.

I don't think anyone here would oppose adding an option to let the
admin change the filter ordering if there was a good reason to add
such an option.  But I think most of the gripes I've heard have been
due to confusion that will hopefully be cleaned up by the new
Netblazer software and manuals.


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