BS EN 62439-7:2012 pdf download

BS EN 62439-7:2012 pdf download.Industrial communication networks —- High availability automation networks Part 7: Ring-based Redundancy Protocol (RRP).
4.7 Network recovery
When link failure or device failure is detected in a RRP ring network, the topology changes and the link status information is automatically broadcast to every device on the network. After broadcasting topology change information, every device on a network starts to update its own path table and tries to find new paths to other devices on the network. This process is operated in protocol machine and changing the blocking point of the network, Thus, devices can transmit messages to their destinations, while they are updating their NMIB.
4.8 Automatic network configuration
RRP supports automatic network configuration. When the network topology changes, the RRP protocol machine of every device shares the changed network information, and then every device updates its own NMIB. RNMs or LNMs are automatically selected on the network according to the device UID and connection status
When a device joins to a RRP network, the device broadcasts a NCMT message with its network information. Other devices in a RRP network receive the NCMT message then update their NMIB and reply to a new device. Thus NMIB is updated automatically through a joining process,
Similarly when a device detects any fault conditions, the device broadcasts a NCMT message to other devices in the network. So that network information is managed automatically by NCMT messages.
4.9 RRP basic operating prInciple
The RRP network is established by following steps:
• power On (Initialization);
• establishment of line network:
• extension of line network;
• establishment of ring network;
• change topology from ring network to line network.
In the initialization phase, a RRP device becomes a stand-alone device. The device tries to find valid RRP connections on its ports. Figure 6 shows that Devicel is initialized and remained stand-alone device. In this phase, the device is In SA state.
When a new link is established between two end nodes in a line network, the network is automatically reconfigured as a ring network. Two RNMs are automatically selected to prevent the infinite circulahon of any frame In a ring network. However, when a link failure is detected in the ring network, the ring network managers (RNMs) change their internal state to convert network topology from a ring to a line network. RNM could send NCMT message periodically to other RNM though the network to examine of the network integrity.
5.2 Network recovery in ring network
5.2.1 General
The RRP network recovery process is simple and is handled within the protocol machine to provide fast recovery time upon network topology changes When a link failure is detected in a ring network, the network is reconfigured automatically as a line network, A topology change from a ring to a line network occurs En the following three cases:
• link fault with the neighbouring device;
• link fault of the remote device;
• local device fault.
If a link failure occurs, the two devices nearest the fault point enter the LNM state and broadcast the NCMT message NCM_LINE_START. When a device receives NCM_LINE_START, it checks its connection status and changes its state to GD or LNM.
A cable break or power failure is treated in the same way as a link fault. A device fault also
takes the same time to recover. Redundancy recovery time is determined from the lime when
a link fault occurs to the time when the path is recovered in a new direction.
The RRP specifies recovery times ton the transition from a ring to a line network. Table 1
shows the parameter set for worst case RRP recovery times when the network parameter Is
set as Table 2.