Mitsubishi Electric MELIPC MI5000 Series User Manual page 187

Check presence
This communications are not possible for a fixed period of time for other devices for which the connection is open, then the
product sends a presence confirmation message to the other device, and checks its presence determined by whether a
response message is received.
Item Protocols that can
be set
KeepAlive TCP/IP
UDP UDP/IP
Do not check TCP/IP,UDP/IP
presence
*1 If the other device does not support the TCP KeepAlive function (response to KeepAlive ACK message), then the connection will be
disconnected.
*2 If a module incorporating Ethernet receives a PING command echo request command, then an echo response packet will be sent in
response automatically. (Even if the connection used for data communications with the other device is closed, this will send a response
to the received PING command.)
■Check presence using KeepAlive
This sends a presence confirmation message 22 seconds after the last message is received from the other device, and
checks that there is a response from the other device. If there is no response, then presence confirmation messages are sent
in 1-second intervals. If responses cannot be confirmed after 8 seconds (30 seconds after the final message was received),
then the other device will be considered not present, and the connection will be disconnected.
■TCP retransmission processing
In TCP connections, if there is no ACK response to the transmission using the TCP protocol from the other device, then this
carries out retransmission processing using the following retransmission frequency and intervals. If there is no ACK response
to the TCP protocol 60 seconds after the last retransmission, then the other device will be considered faulty, and the
connection disconnected.
*1
• Retransmission count : 12 times
*2
: (retransmission count × retransmission count × RTO
• Retransmission interval
*1 At establishment of the connection, if 30 seconds has passed, then the connection to the other device will be considered faulty and
disconnected even if the retransmission count is 12 or less.
*2 The maximum value for retransmission period is 60 seconds.
*3 RTO (retransmission timeout) is a value that increases exponentially based upon the RTT (round-trip time).
Description
Use connections opened using the TCP/IP protocol. A presence confirmation ACK message is sent to other
devices for which communications are not possible for a fixed period of time, and its presence checked by
whether a response is received.
If open status does not continue, then the connection is automatically closed.
Use connections opened using the UDP/IP protocol. A PING command (ICMP echo request/response
function) is sent to the other devices for which communications are not possible for a fixed period of time,
and its presence checked by whether a response is received.
Does not check the presence of other devices.
*1
*2
*3
) ÷ 1024 (sec.)
17 BASIC PARAMETERS
17.4 External Device Configuration
17
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