Time
The FireBrick does not have an internal clock, but tracks time while powered
up. To keep time it uses an internet time server.
Any major changes are logged (i.e. more than a 1 second correction).
Two time server addresses are defined, with the second being used if the
first does not respond.
Setting the clock
Time requests are sent using UDP port 37 (timed), allowing the clock to
be set to the nearest second. The time is set approximately every hour,
and tried for several minutes. If no reply, the internal time is clocked
anyway, but may drift by a few seconds a day if no time server responds.
On power up the time is not set, and some functions do not operate or operate
differently if the time is not set.
Note, some versions of linux (e.g. Red Hat 6) have a broken UDP port
37 time server giving a time that is about 8 years fast. The two time servers
pre-programmed are time-a.nist.gov and time-b.nist.gov, which are two US
public time servers.
In order to set the clock, the FireBrick must be able to route packets
to the internet. A simple WAN subnet and gateway is normally all that is
needed, but if operating in a full stealth mode, then a WAN stealth address
will be needed as well as a gateway. Once these are set the clock is normally
picked up automatically. It can however be set by selecting the Set button
on the time setup page.
Note that if the clock is set, it is likely to log you off if logged
in as you will suddenly have been logged in for many years !
Every hour
The clock is set at least once per hour, but not on the hour. This is deliberate,
as public time servers would be overloaded if everyone set the time on
the hour. You can also restrict the time setting using a profile, so that
it is only set at certain times - e.g. once a day, once a week, only during
the day, etc. This profile only applies once the clock is set!
Time server
The FireBrick is a time server for UDP port 37 and TCP port 37 (timed)
only, and normally provides time to within 2 second. No response is sent
if the clock is not set. (2 seconds, as the reply is only to the second,
and the time was only set to the second).
Time zones
The time is kept internally in UTC, but a time zone from -11 to +12 hours
can be configured. In addition, a one hour offset can also be applied for
"summer time". This is automatically adjusted in the early hours of two
Sundays in the year. Automatic adjustment can be disabled by setting either
of the dates for changes to "Manual". You can configure the summer time
to start after the winter time in the year for southern hemisphere operation
if required.
All displays and logs and time profiles are based on local time.