Rockwell Automation Ethernet Design Considerations Reference Manual - Manual (Page 46)

46 Rockwell Automation Publication ENET-RM002C-EN-P - May 2013
Chapter 3 Ethernet Infrastructure Features
QoS Guidelines
Follow these guidelines with QoS:
• Manage the output queues based on application needs. Schedule precision
and motion control packets in the highest priority queue.
• QoS gives preferential treatment to Industrial Automation and Control
System Network traffic at the expense of other network traffic.
• QoS is integrated into the Stratix 8000 and Stratix 8300 switch
configurations.
• Deploy QoS consistently throughout Industrial Automation and Control
System Network.
Resiliency A resiliency protocol maintains parallel links for redundancy while avoiding
loops. Network convergence time is a measure of how long it takes to detect a
fault, find an alternate path, and recover from the fault:
• During the network convergence time, some portion of the traffic is
dropped by the network because interconnectivity does not exist.
• Communication drops if the convergence time is longer than the Logix
connection timeout.
Time Calculations in a Logix5000 System
Network convergence must occur before the control system is impacted:
• Logix message instruction (MSG) time out (explicit, CIP Class 3)
• I/O connection timeout (implicit, CIP Class 1), 4 x RPI, 100 ms
minimum
• Logix Producer/Consumer connection timeout (implicit, CIP Class 1),
4 x RPI, 100 ms minimum
• Safety I/O connection timeout (implicit, CIP Class 1), 4 x RPI (default)