User manual

IEC61131 User and Reference Manual
April 22, 2008
477
SCADAPack DNP Router
All SCADAPack controllers can be configured as a DNP Router. A unique characteristic of a
SCADAPack DNP router is the ability to:
 Route (or forward) DNP messages not destined to this station, using rules defined within a
routing table.
Otherwise, a SCADAPack controller not configured for DNP routing will simply discard a message
whose DNP destination address does not match that of the controller.
A DNP router is typically used when a direct communication link between the DNP master and
outstation cannot be established, typically due to different physical layers on the two network
segments. For instance, the physical network between the DNP SCADA Host and the router could
be an Ethernet connection, while the physical layer between the router and all outstations could be a
multi-drop serial RS-485 or even an RS-232 radio connection. Given that messages are routed
directly from the DNP SCADA Host to the outstations, bandwidth limitations are dictated by the
speed of the serial multi-drop connection. On the contrary, there is no bandwidth limitation within a
DNP Mimic architecture, as the Mimic Master immediately responds to the DNP SCADA Host on
behalf of the targeted outstation. Of course, the side effect of the DNP Mimic architecture is that
polled data obtained by the DNP SCADA Host may not be very current. In either case, careful
design considerations based on these tradeoffs should be exercised.
As mentioned above, the SCADA Host has only one connection to a SCADAPack DNP Router. All
target outstations of the SCADA Host are connected down stream of the DNP Router as illustrated in
the figure below.
DNP SCADA Host
SCADAPack
DNP Router
SCADAPack
DNP Outstation B
SCADAPack
DNP Outstation C
Ethernet
Multi-drop Serial RS-485
or RS-232 data radio
Figure 0-6: SCADAPack DNP Router and multi-dropped DNP Outstations
In the above configuration the SCADAPack DNP Router (Outstation A above) manages all the
communication with the outstations. The SCADAPack DNP router receives messages from the
SCADA Host for each outstation and route or forwards the messages to the outstations, based on
routing rules established with the DNP Routing table.
DNP Messages are routed based on the following logic:
if (a message is received which needs to be retransmitted to someone else)
if (the message target is configured in our routing table)
if (the destination port is different from the incoming port)
or (routing is enabled on the incoming port)
then retransmit the message