Fire-Lite IPDACT Installation Manual - Manual (Page 7)

IPDACT Module - Introduction
I-4
Doc.Dm373-I
Rev.2.0
address is given to the IPDACT and is the primary communication option.
The backup VisorALARM IP address is also configured and is used in cases
where the main device fails). If the exchange of messages does not occur
during the configured time, the IPDACT tries to resend. If, after a configurable
number of attempts, a satisfactory response is not received, the connectivity
with the main VisorALARM is presumed lost. At this point the IPDACT tries
to communicate with the backup VisorALARM, to which it will now try and
send the alarms, polls, etc. In cases where communication with this second
device also fails, the telephone line access is returned to the control panel as
if the IPDACT was not present. From this point on, the IPDACT will try to re-
establish communications both with the main Teldat VisorALARM and the
backup, communication with the main device taking priority. The moment
communications are reestablished with either of the two ARC devices, the
IPDACT intercepts the telephone line once more.
The supervision traffic is encrypted UDP. The Ethernet frame size does not
exceed 70 bytes. The monitoring interval, the number of retries and time
between retries are all configurable, and are values that must be carefully
considered. Normally the monitoring interval in the control panel is high as
this implies a telephone call. However, in the case of IPDACT, this cost is
irrelevant as it is dealing with traffic which in all likeliness is running over a flat
rate connection. In addition, a high value here is not advisable in cases where
the IPDACT connects to Internet through a router executing NAT, a very
probable situation. This is because traffic coming from the ARC towards the
IPDACT reaches this thanks to the router maintaining the entry in the NAT
table active during a period of time, the entry being refreshed with supervision
traffic. If the supervision interval is greater than the residence time for the
entry in the NAT table, communications from the ARC will not be possible.
There is no rule to say how long an entry in the NAT table must last for. In
cases of the TELDAT devices, this is around 5 minutes. A low value has the
problem that the traffic the VisorALARM must process is high, the same as
the bandwidth requirements. If ARC Internet access is ADSL, you need to
consider that the upstream channel is smaller than the downstream one and
that supervision traffic returned to the IPDACTs is slighter larger than the
incoming.
The incoming traffic to the ARC is:
mips ALIVE KEEP
N T C * * 528
−
=
The minimum supervision time can be 1 second and a VisorALARM can have
3000 IPDACTs registered that give an input traffic of 1,58 Mbps. The return
traffic is approximately 6% larger.
The Teldat VisorALARM received monitoring messages from the IPDACTs.
If these are registered, they are assumed alive and an acknowledgement
response is sent to them; if the IPDACTs are not registered, they are ignored.
Periodically the status of all the registered IPDACTs is checked and all those
which have not notified their availability (i.e. those which have not responded