Re: RE: Acqusition of time

["Paul D. Robertson" <proberts () patriot net>]

On Wed, 29 Jan 2003, Brian Monkman wrote:

> Ok - so something more specific this time.
>
> We are talking about a firewall farm. We want the time to be sync'ed 
> between all of the firewalls. Logs go to a central logging server. 
> Reason for the sync'ing, to ensure that time is accurate across all of 
> the firewalls in order to facilitate forensics and event correlation.
>
> In your opinion - should we have a battery backed-up clock on these 
> firewalls or is the network time source sufficient?

If the criterion is that the firewalls be synchronized to some standard, 
then I suppose the real issue is what happens if a single firewall is 
rebooted and unable to reach either the time server or the logging server 
(if it's syslog, you don't even know you didn't get there?)

(UDP-based syslogs were heavily affected by SQL-Slammer for instance.)
  
Battery back-up helps for the reboot instance, and (potentially, though 
not normally) for the timeserver goes down instance.  If there's defined 
behaviour for "system rebooted and couldn't reach the timeserver" and it's 
materially seperable from "just after midnight," then I don't suppose 
there's much of an issue, you can put things back together by deltaing 
once you do get reliable time information.  

Paul
-----------------------------------------------------------------------------
Paul D. Robertson      "My statements in this message are personal opinions
proberts () patriot net      which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assessment TruSecure Corporation

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