Station Manager Lockout Under Heavy Load; Ping Restrictions; Srtp And Modbus/Tcp Connection Timeout - GE RX3i User Manual

Station Manager Lockout under Heavy Load

Sustained heavy EGD and/or SRTP Server load can utilize all processing resources within the Ethernet interface,
effectively locking out the Station Manager function. The Station Manager appears inoperative under either
local or remote operation. The Ethernet interface always gives higher priority to data communication functions
than to the Station Manager. When the processing load is reduced, the Station Manager becomes operative
once again.
This condition is not reported to the Controller Fault Table or Ethernet exception log.

PING Restrictions

To conserve network data buffer resources, the CPU process only one ICMP control message at a time. An ICMP
Echo (ping) request that arrives while the CPU is processing another ICMP control message is discarded. When
multiple remote hosts attempt to ping the CPU at the same time, some individual ping requests may be ignored
depending upon the timing of the ping requests on the network.
The CPU may initiate ping requests to another host on the network via the "ping" Station Manager command.
The ping request sequence is restricted to one remote host at a time.
Discarded ping requests are not reported to the Controller Fault Table or Ethernet exception log.

SRTP and Modbus/TCP Connection Timeout

When the Ethernet Interface is abruptly disconnected from a remote SRTP or Modbus/TCP device (for example,
by disconnecting the Ethernet cable), the underlying TCP connection attempts to re-establish communication.
By default, the underlying TCP connection in the Ethernet Interface remains open for 7 minutes while TCP
attempts to reconnect. During this interval, the SRTP or Modbus/TCP connection is unavailable. If all the SRTP or
Modbus/TCP connections in the Ethernet Interface are in use or otherwise unavailable, a new SRTP or
Modbus/TCP server connection must wait until an existing SRTP or Modbus/TCP connection times out. If the
SRTP server connection was used by the Programmer, any new Programmer connection is restricted to Monitor
operation until the previous connection times out and is cleaned up.
Release 6.00 of the Ethernet Interface introduces the SRTP Inactivity Timeout. This feature reduces the amount
of time required to terminate and clean up an SRTP programmer connection to 20 – 30 seconds. The SRTP
inactivity timeout is initially set by the "vconn_tout" AUP parameter for programmer connections. Revision 6.00
and higher of the PME programmer can override this initial value. See "SRTP Inactivity Timeout" in Chapter 1 for
details.
If desired, the TCP connection timeout duration may be adjusted via AUP parameters. See Appendix A to
configure and use AUP parameters. The TCP connection timeout interval (in seconds) is calculated as:
TimeoutSeconds = wkal_idle + ( (wkal_cnt + 1) × wkal_intvl )
For example, the following set of AUP parameters will establish the TCP connection timeout as 25 seconds:
wkal_idle = 10
wkal_cnt = 2
wkal_intvl = 5
Note that the TCP connection timeout interval applies to all TCP-based connections at this Ethernet interface.
This includes all SRTP, Modbus/TCP, FTP, and (where supported) web sever communications. To allow for
normal TCP reconnection, any adjusted TCP connection timeout must exceed the longest application data
transfer interval.
The underlying TCP connection timeout is normal expected behavior, and is consistent with our other PLC
products.
GFK-2224Q January 2017
Chapter 12. Diagnostics
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