Bumpless Operation With Mrp - GE PACSystems RX3i User Manual

Chapter 6. Redundant Media
6.1.2

Bumpless Operation with MRP

The PROFINET Controller supports bumpless operation with GE PROFINET I/O Devices if and only if
specific conditions are met. Bumpless operation means that a single break in an MRP ring will not
cause the PROFINET connection to be lost and there is no observed loss and addition of PROFINET
I/O Devices while the ring network recovers.
Without bumpless MRP, when a device is lost, it must be re-acquired by the I/O Controller; a typical
recovery time is on the order of seconds.
There are two ways an MRM detects a break in the ring:
•
A message from an MRC that provides LinkUp/LinkDown detection
•
Use of a test packet timeout interval
A network using Media Redundancy Protocol recovers from a ring failure within 80 milliseconds
when running at 100/1000 Mbps full duplex with default Media Redundant Manager (MRM) test
packet values. Actual failover time depends on the device responsiveness to network disconnection
and reconnection, number of devices in the ring, media speed, length of media, and frequency of
sending test frames over the network. Network recovery time is shorter with fewer devices, faster
media speed, and shorter media lengths. Third-party devices in the MRP ring may introduce
additional network recovery time. Network recovery time is limited by the ring participant with the
slowest ring failure recovery time. Devices that do not provide LinkUp/LinkDown detection should be
taken into account when calculating network recovery time.
For bumpless network recovery (without disturbing IO communications to an I/O-Device), the I/O
Update Rate for the I/O-Device should be configured to be greater than 1/2 of the network recovery
time. This permits the ring to be disconnected or reconnected without timing out the communication
connection between the I/O Device and its I/O-Controller.
In order to insure correct MRP operation, it is important to connect the correct Ethernet ports of the
PROFINET Controller and devices to the MRP ring. The ports connected to the ring must be the same
ports configured as MRP Ring Ports. Failure to connect the configured ports will prevent the
PROFINET Controller and devices from correctly participating in the MRP ring.
Disclaimer: Pulling a fiber SFP cable out of the SFP cage (as opposed to cutting a fiber cable), can
have unpredictable performance (and may lose devices in a properly configured MRP ring) due to the
fact that the light is still seen by the SFP as the cable is being removed so that data is lost
significantly before the SFP can detect that the connection has been lost.
130 PACSystems* RX3i & RSTi-EP PROFINET IO-Controller User Manual GFK-2571N