SilentKnight VisorALARM High Availability Receivers - Manual (Page 5)

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IPDACT-2/2UD keeps supervising the link to the main VisorALARM receiver so it can
switch back to Normal Operation as soon as the main link is recovered.
The backup switching, as well as the main link recovery process is automated, so no user
interaction is required.
VisorALARM Data Base synchronization
Since each VisorALARM keeps its own Data Base with the IPDACT-2/2UD accounts on
field, the main VisorALARM and the backup Data Bases must be synchronized at all
times, so the backup VisorALARM can keep the update of new IPDACT-2/2UD’s and
then serve them in emergency conditions.
The Data Base update process is sensitive to the internal time clocks of each
VisorALARM receiver. In fact, both VisorALARM units must synchronize their clocks
with a Network Time Protocol Server – NTP server. This clock server can be of private
use, as shown in Figure 1 or can be a public server located in the Internet.
The Data Base synchronization is carried out periodically and involves two additional
communication flows between both receivers:
• Polling: The backup VisorALARM polls the main one periodically for Data Base
updates.
• Update: If there has been any change between the two Data Bases, they are
synchronized.
2. The traffic pattern charts
The CMS network depicted in Figure 1 has been simplified for a better understanding of
the system backup performance. In real scenarios, the CMS network can be of diverse
complexity and will, of course, include Firewalls to increase the security.
As defined in the previous section, there are different communication flows that must be
allowed along the IP network for the backup system to work properly.
2.1 IP traffic flows between the IPDACT-2/2UD and the VisorALARM’s
All the communication flows between the IPDACT-2/2UD and the currently active
VisorALARM – either the main or the backup one – is of type UDP and they have the
following pattern: