Connection to Rockwell PLC is cyclically opened and closed (error code 0x203)

Connection to Rockwell PLC is cyclically opened and closed (error code 0x203). What could be the problem?

One possible reason could be that the Rockwell controller firmware does not support the QoS (Quality of Service) functionality.

In an ethernet frame, QoS uses the DSCP field in the IP header for priorization. If your EtherNet/IP device supports the CIP QoS object (Class ID 0x48) this DSCP field for I/O frames is unequal to zero. A number of Rockwell Automation Ethernet modules with older firmware discard I/O packets that have been marked in this way, causing the EtherNet/IP I/O connection to time out with error code 16#0203 shortly after it is established.

This issue is already known and solved by Rockwell.The following link gives more information on how to solve this and all affected PLC firmware versions.

http://forum.deltamotion.com/viewtopic.php?f=12&t=158