Date Code 20210715 SEL-2890 Instruction Manual
Settings and Commands
Settings
3.5
Commanded mode tunneling allows the user to Telnet into the Console and issue a
tunnel command followed by an IP address and Telnet port. For example, entering the
command TUN 192.168.0.11:3001 <Enter> will direct the SEL-2890 to establish a
Telnet tunnel with IP address 192.168.0.11 and Telnet port 3001. The receiving device
may be a port server set in slave mode, a PC, an SEL-2890, or an SEL-2701.
In Telnet tunnel mode, a transceiver will try to establish a Telnet tunnel with another
transceiver, port server, PC, or SEL-2701 card. If the transceiver fails to open a
connection, it will wait and listen for someone trying to establish a Telnet tunnel with
it. The transceiver will toggle between master mode and slave mode until a Telnet
tunnel is established. The Ethernet connection for a Telnet tunnel is maintained after it
is established. This is the major difference between a Telnet mode or Commanded
mode tunnel and a TCP tunnel. The Telnet tunnel is primarily used for point-to-point
serial communications that do not often change.
A TCP tunnel operates identically to the Telnet tunnel with one exception: the TCP
tunnel will establish an Ethernet connection when needed and will then close the
connection when it is finished. The advantage of this is that a transceiver can be set up
to broadcast messages and then close the connection and wait for another transceiver to
answer and establish an Ethernet connection.
The BTCP tunnel mode is designed for tunneling serial protocols on an Ethernet
network including Modbus and DNP3. See BTCP Tunnel on page 1.7 for a description
of this mode of operation. For best BTCP tunnel performance, use the same serial port
bps speed for both master and slave connections. Figure 1.3 shows the physical
connection required for this mode of operation.
All other functions such as email, Telnet access to the serial port, HTTP access to the
serial port, and serial routing are disabled if serial tunneling is enabled. Telnet access
to the console session is still enabled. The HTTP server is not allowed to access the
serial port when serial tunneling is enabled.
Unsolicited Detection Delay
The UDDELAY time is used to qualify the end response from the serial device in an
HTTP session. Unsolicited message processing is suspended when a Telnet session is
active and does not use the UDDELAY setting. The UDDELAY should be set longer
than the response time of the connected IED.
Message Timeout Delay
The MTDELAY time is used to determine the difference between one or multiple
messages. The MTDELAY acts similarly to an intercharacter time-out timer. When a
message is being transmitted from an IED through an SEL-2890, the transceiver will
examine the delays between characters in the serial data stream. The data stream and its
message will be broken into two or more messages if there is an intercharacter delay
that is greater than the MTDELAY time. The subsequent messages will still be
considered solicited unless the delay also exceeds the UDDELAY time.
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