IEC 62439-2:2010 pdf – Industrial communication networks – High availability automation networks -Part 2: Media Redundancy Protocol(MRP).
The MRM shall indicate changes in the ring state to the MRCs by means of MRP_TopologyChange frames.
The MRM shall not forward NRP specific frames (NRP_Test frames, MRP_TopologyChange frames, NRP,LinkChange frames) between its ring ports.
If the MRM receives an NRP_llnkUp or MRP_LlnkDown frame, then the MRM shall reduce its test monitoring time according to Table 33 to accelerate the detection of the open ring. When the open ring is detected then the MRM shall send the NRP_TopologyChange frames through both its ring ports.
Optionally the MRM shall send the MRP_TopologyChange frames through its ring ports. This option is selected by setting the parameter REACT_ON_LINK_CHANGE, see Table 26.
The MRM shall send to the MRCs an MRP_TopologyChange frame with the delay, after which the ring topology change will be performed. The parameter carrying this delay is called MRP_Interval, When this time has expired, all MRCs shall clear their filtering database (FOB),
Each NRC shall send the configured delay in MRP_lnterval to the MRM in the MRPLinkL,Jp and MRP_LinkDown frames to tell the MRM after which time the NRC will change its port state from BLOCKED to FORWARDING (NRP_LinkUp frame) or to DISABLED (MRPLinkDown frame).
Measures shall be Included to prevent the MRM from remaining stuck In the closed state in case of node failure.
5.3 Media Redundancy Client (MRC)
Each MRC shall forward MRP_Test frames received on one ring port to the other ring port and vice versa.
If the MRC detects a failure or recovery of a ring port link, the MRC may optionally notify the change by sending MRP_LinkChange frames through both of Its ring ports. Each NRC shall forward MRP_LlnkChange frames received on one ring port to the other ring port and vice versa.
Each NRC shall forward MRP_TopologyChange frames received on one ring port to the other ring port and vice versa, Each NRC shall process these frames. It shall clear its FOB if requested by an MRP_Topologychange frame in a given time interval (see Table 33. MRP_TOPchgT).
5.4 Redundancy domain
The redundancy domain represents a ring. By default, all NRN and MRCs belong to the default domain. A unique domain ID can be allocated as a key attribute, especially If an MRM or an NRC is member of multiple rings. A node shall assign exactly two unique ring ports per redundancy domain.
NOTE I A d.vic.. may hay. otti.r p0415 th.n he two assign.d to MRP Th.s. oth.r ports ire not influ.nc.d by MRP
NOTE 2 MRP ports should behave as If RSTP is disabled.
5.5 Usage with diagnosis and alarms
If the attribute Check Media Redundancy has the value TRUE, media redundancy events shall cause diagnosis events and alarm notifications,
5.6Ring diagnosis
ln a redundancy domain the following diagnosis events handling shall be implemented byeach MRM.
.lf a device is configured as MRM,but not operating in the manager role, it shall signal a
“MANAGER_ROLE_FAIL”diagnosis event and suspend reporting of all other mediaredundancy diagnosis events while not in the manager role.
lf a device is operating in manager role and this device detects another active MRM，itshall signal the “MULTiPLE_MANAGERSTevent.This event can occur concurrently withthe ring state eventRING_OPEN”.
lf a device is operating in manager role and detects an open ring，it shall signal the“RING_OPEN” event.
These events shall be signalled by using the State Change service see 7.3.
NOTE The presence of MRP_Test frames enables the checking of the existence of an MRM.5.7Multiple MRM in a single ring
There shall be only one active MRM in the ring even if several nodes have this ability.NOTE Multiple active MRMs cause the ring to divide itself into several segments,
As an option, in case of more than one node having the ability to become an MRM in the ring.an enhanced protocol not specified in this International Standard may be used to decidewhich of these nodes shall become the MRM,while the other nodes take over the MRC roleas shown in Figure 4.To this effect the nodes with the MRM ability have different prioritiesthat shall be conveyed in the MRP_Prio field of the MRP_Test frame.
lf an optional protocol for multiple MRM in a single ring is used then all MRM in the ring shallsupport the same protocol.The vendor shall specify the supported protocols.