Vendor-Specific Implementation; Dnp3 Link Modes; Dnp3 Tcp/Ip Mode - Hitachi Relion 670 Series Communication Protocol Manual

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Table Of Contents

Table of Contents

1MRK511391-UUS Rev. L

Section 3

3.1

DNP3 link modes

3.1.1

DNP3 TCP/IP mode

DNP3 TCP/IP link mode is supported by the IED. This implementation supports up to four different

masters communicating simultaneously with the IED. The IED is a listening endpoint implementation and

listens for connections from DNP3 masters on a configurable port, TCPIPLisPort. The IED does not

connect to masters, meaning that it is not a dual-endpoint implementation.

It is possible to use both the connection establishment method based on the master IP address, and the

connection establishment method based on the port number. The identification and association of the

master is based both on the IP address of the master and the port number it connects to. It is essential to

make sure that the parameters TCPIPLisPort, MasterIP-Addr, MasterIPNetMask, SlaveAddress and

MasterAddress uniquely identifies one master from the other masters.

The above is an important concept to grasp during commissioning so that no conflicts occur. Therefore, it

is strongly recommended not to change the MasterIPNetMask parameter to anything else than its default

255.255.255.255 unless necessary. The parameter should not be mixed up with the subnet mask of the

IP configuration. The MasterIPNetMask can be used to allow to accept connections from masters that do

have dynamic IP addresses within a known range.

For example, if a master changes its IP address dynamically in the range of 10.10.10.1 and

10.10.10.254, the MasterIPNetMask could be set to 255.255.255.0 to allow for connections from this

range. If two masters share this dynamic range or share the same IP address, it is necessary to separate

them by having them connect to separate ports, for example, 20000 and 20001 respectively.

Also, SlaveAddress and MasterAddress must be correctly configured for each master. Otherwise, the

previously accepted connection is closed upon the reception of the first DNP3 message.

The IED supports the requirements of the standard to receive UDP broadcast messages on the ports

configured by UDPPortAccData.

As a default, the IED sends a keep-alive message in every 10 seconds according to the value of the

tKeepAliveT parameter. The time can be changed, and setting it to zero means that no keep-alive

messages are sent. It is important to know the hazards of disabling the keep-alive, and it is not

recommended to do so unless necessary. If the keep-alive messages are unwanted, it is better to

increase the value of tKeepAliveT so that it exceeds the master's poll rate.

If a master crashes or the communication links are broken and the master restarts, the TCP/IP makes

the IED believe that the connection still exists. Since the IED conforms to the recommendations of the

standard not to accept new connections when a connection already exists to the particular master, the

master will never be allowed to connect again. Another parameter that concerns the TCP/IP connection

status is tBrokenConTout. It determines how long a session is active after a TCP/IP connection has been

broken. After the time period, the session becomes inactive and events are not stored. If the parameter is

set to 0, events are stored until the sequential buffers overflow. Note that if the parameter is set to zero,

all events from start-up until the sequential buffers overflow are saved even though no connection would

have been established.

Further documentation concerning DNP3 TCP/IP communication is available in the IP Networking

document Volume 7, from www.dnp.org.

DNP, 670 series

Communication protocol manual