The PC will now send a message to the AKC unit which is addressed 5:2.
The datagram is fi rst sent to the PC gateway which checks in its router table to see where the
datagram has to go.
In checking the router table the PC gateway will look for the line in the table where the receiver’s
network are contained. This requirement has been fulfi lled by line 2, as it indicates the network No. 5.
After the “Port No.” fi eld has been read, the datagram is directed out of gate 1 which is DANBUSS.
After furthermore having read the “Address” fi eld, it will be seen that the datagram is to be sent to
address 125 which in this case is a modem gateway.
The modem gateway receives the datagram and checks its router table. Line 2 here indicates the
network 5. By reading the “Port No.” fi eld, the datagram is directed out of gate 2 which is the modem.
By furthermore reading the “Address” fi eld it will be seen that a telephone number will have to be
called.
Modem gateway (2:125) transmits the datagram to modem gateway (5:125) in the other network. This
will now check its router table and fi nd that it is on its own network. The datagram is now transmitted
straight to the AKC controller for which it was intended.
For answers use the router lines again. But now from the other side.
The router tables need not be changed, until a new network has to be included.
When a gateway checks its router table, it will always look from line 1 and downward. The fi rst line
containing a usable network for a given receiver system address will be used. Subsequent lines that
may contain the same receiver system address will not be detected.
As router tables in several gateways have to co-operate on the conveyance of messages in a DANBUSS
system, there must be care taken in the setup of these. Errors resulting in datagrams not reaching the
correct receivers will not trigger an alarm.
Make sure that you have an easily legible list of addresses and network numbers on all relevant
gateways and PC’s before establish ment of router lines is commenced!
Don’t forget that messages are also returned in the system.!
Appendix A - continued
36
Manual RS8DT102 © Danfoss 09/2004
AKA
245
