Welcome to using M$ software through a firewall ;-)  It depends on what
the service is that's causing the problem.  For some services (like the
command port on FTP) you might be able to fix it by using a larger
timeout value for the service, so long file transfers complete before
the command channel times out at the default of 1 hour.  Same for long
database queries that don't send any data while waiting for the request
to complete.  Depending on your control of the devices involved, you
might also be able to change the settings to send TCP keep-alives, so
the connection passes data to keep it active in the state table without
timing out.  The defaults for Windows are usually too high, and I've set
some to start sending a keep-alive packet every 15 minutes to keep it in
the state table, which might work for you.  The MS knowledge base has
the registry changes to do that for your OS version if you're able to.

If you wind up chasing the timeout higher and higher, and trying to
define too many services with large 24 hour timeouts and such, keep in
mind the impact on the size of the state table for sessions that don't
end cleanly, and will stick in the state table sucking up space for all
that time before being cleared out.  Long database queries with no
keep-alives are a prime candidate for users to get frustrated after 5
minutes and just drop the connection and try again, leading to both a
bloated memory state table on the firewall, and a DB server on it's
knees looking up requests from users that aren't there to get the
results anyway.  Fixing the application problem (DB performance tuning),
using keep-alives, or redesigning the architecture (where possible) are
better ways to make it reliable than cranking up the timeout values or
turning off checks for traffic not in the state table, which defeats a
lot of what you installed that firewall in the first place for.

 

-----Original Message-----
From: Mailing list for discussion of Firewall-1
[mailto:[EMAIL PROTECTED] On Behalf Of Tucker,
Fredrik M
Sent: Thursday, February 09, 2006 15:06
To: [email protected]
Subject: Re: [FW-1] drop out of state tcp?

Exactly, the connection is timing out on the firewall before it times
out at the endpoints and several sources I have found explain this
common issue occurs from Microsoft's loose adherence to RFC793.  However
many explanations exist, I have yet to find an acceptable solution!

The option doesn't exist for me to allow out of state TCP from specific
hosts, only as a global setting.  I've been told the problem needs to be
approached differently but how?

Thanks!
fred

-----Original Message-----
From: Mailing list for discussion of Firewall-1
[mailto:[EMAIL PROTECTED] On Behalf Of Mark
Senior
Sent: Thursday, February 09, 2006 2:43 PM
To: [email protected]
Subject: Re: [FW-1] drop out of state tcp?

If they really are violating TCP standards, i.e. sending unsolicited
ACKs, then they won't be able to communicate anyway, as the other side
won't have an allocated socket.

A more likely explanation might be that the connection is timing out on
the firewall before it times out at the endpoints.  Then they start
talking again, but the firewall's forgotten about the conversation.

Regards
Mark  

-----Original Message-----
From: Mailing list for discussion of Firewall-1
[mailto:[EMAIL PROTECTED] On Behalf Of Tucker,
Fredrik M
Sent: 8 February, 2006 14:50
To: [email protected]
Subject: [FW-1] drop out of state tcp?

Checkpoint FW-1 NG R55

Is there a "more restrictive" alternative to un-checking "drop out of
state TCP" in the Global Properties?

Specifically dealing with a handful of Microsoft boxes on either side
that seem to violate TCP standards.

Can an exception be made per rule?

More specifics:

Dropped... TCP packet out of state; First packet isn't SYN;
tcp_flags:ACK

Thanks!

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