BS EN 62439-3:2012 pdf download

BS EN 62439-3:2012 pdf download.Industrial communication networks-High availability automation networks Part 3: Parallel Redundancy Protocol(PRP) and High-availability Seamless Redundancy (HSR).
NOTE A VLAN-Iagged frame can pass several witch.s which may remove or insert VLAN tags It the sender observes th. ISOIEC 88023 (IEEE 8023) rule to send a minimum frame size of 68 octets for a VLANtagged trame and of 84 for a Vt.AN-untagged frame. there Should never be a siluatlon In which there Is padding before and aflr the RCT Scanning from behind is specitied as a matter 01 precaution
4.1.10.3.5 Frame size restriction
Appending the RCT could generate oversize frames that exceed the maxValidSlze foreseen
by ISO/IEC 8802-3 (IEEE 802.3).
To maintain compliance with IEEE 802.3:2005, the communication software in a DANP using duplicate discard is configured for a maximum payload size of 1 496 octets.
NOTE Longer payloads would work In most cases, but this requires previous testing. Many switches are dini.nsion.d for doubfe•VLANtagged (non•IEEE 802.3 compliantl frames that hav, a mazimum size 01 1 526 octets. Most Ethernet controllers are ce,lItled up to I 528 octets. Most switches would forward correctly frames of up to I 536 octets, but this cannot be relied upon.
4.1.10.3.6 DIscard algorithm
The following algorithm is optional, other methods such as hash table can be used.
The receiver assumes that frames coming from a DANP are sent in sequence with increasing sequence numbers. The sequence number expected br the next frame is kept in the variables ExpectedSeqA. respectively ExpectedSeqB.
At reception, the correct sequence can be checked by comparing ExpectedSeqA with the received sequence number in the RCT. CurrentSeqA. Regardless of the result, ExpectedSeqA is set to one more than CurrentSeqA to allow checking the next expected sequence number on that line. The same applies to ExpectedSeqB and CurrentSeqB on LAN B,
Both LANs thus maintain a sliding drop window 01 contiguous sequence numbers, the upper bound being ExpecledSeqA (the next expected sequence number on that LAN). excluding that value, the lower bound being StartSeqA (the lowest sequence number that leads to a discard on that LAN) as Figure 9 shows for LAN A. The same applies to ExpectedSeqB and StartSeqB on LAN B.
To this effect, all senders and receivers maintain tables of nodes with which they communicate that record the last time a frame was received from another node, the time a mullicast or broadcast frame was sent and other protocol information.
At the same time, these tables allow to establish connections to synchronize the sequence numbers and detect sequence gaps and missing nodes.
Since the protocol is loosely connection oriented, the sequence numbers corresponding to non-existent nodes are cleaned up by a low priority task after a time NodeForgetTime.
Supervision relies on each DANP sending periodically a PRP_Supervision frame that allows checking the integrity of the network and the presence of the nodes. At the same time, these frames allow checking which devices are DANP, the MAC addresses they use and which operating mode they support, duplicate accept or duplicate discard
4.1.13 Redundancy management interface
Redundant devices and links are useless without network management supervising this
redundancy and calling for maintenance actions.
The LRE presents a network management interlace that allows to track the health of each
LAN, and especially to detect failures early when the error rate increases. To this effect, the
LRE keeps for each adapter (each LAN) a counter of received messages and of messages
received with an error.
The LAN statuses appear as SNMPv1 or SNMPv2/v3 variables. This allows using the same
tools for managing the nodes and the Switches.
NOTE SNUP is part o4 the P protocol suite
4.2 PRP protocol specifications
4.2.1 InstallatIon, configuration and repair guidelines
NOTE Ttae uelre are io be toilowed at ,SiI,at.on t.me, they do hoi apply Iv u,,Iu,,n4,ke teI. vi tr devece
4.2.1.1 LANs layout
The network shall consist of two LANs that have similar properties, i.e. each one is able to carry the traffic that would exist in the absence of redundancy.
4.2.1.2 Labelling cables
The two LANs shall be labelled A and B and shall use cables distinctly identified.
4.2.1.3 LabellIng switches
Switches in the two LANs shall have a distinct label or colour for each A or B.
4.2.1.4 Independent operation
The layout of both LANs shall fulfil the assumption of fall-independence.