BACnet Passive BBMD for Automated Subnet Failure Recovery
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Solution Overview
Problem
BACnet global broadcast communication systems face reliability issues due to the lack of automated failure detection and recovery mechanisms for BACnet Broadcast Management Devices (BBMDs), leading to potential cyclic transmissions and disruptions in communication across subnets when a BBMD fails, with manual replacement being the only available method.
Innovation Solution
Enabling BIP devices to act as both active and passive BBMDs, where a passive BBMD monitors the active BBMD's status, assumes the active role upon failure, and synchronizes the broadcast distribution table (BDT) with other BBMDs, ensuring seamless communication recovery within minutes without the need for additional hardware or tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single active BBMD is used in a subnet, then cyclic transmission of broadcast messages is prevented, but the system lacks redundancy and automated failure recovery
Solution Approach 1:
A passive BBMD is pre-configured in each subnet before any failure occurs. This passive BBMD monitors the active BBMD and stands ready to take over immediately upon failure detection, eliminating the need for manual intervention and ensuring continuous broadcast communication across subnets.
Solution Approach 2:
The passive BBMD continuously monitors the health status of the active BBMD through heartbeat signals or status messages. When the active BBMD fails to respond or sends a failure indication, the passive BBMD detects this through feedback mechanisms and automatically transitions to the active role, maintaining broadcast communication reliability.
2Reliability
If manual replacement of failed BBMD is implemented, then system simplicity is maintained, but communication disruption time increases
Solution Approach 1:
The passive BBMD is pre-configured with all necessary broadcast distribution table (BDT) information and communication parameters before failure occurs. This preliminary preparation enables immediate takeover upon active BBMD failure, reducing recovery time from minutes or hours to seconds without requiring manual configuration or additional hardware.
Solution Approach 2:
The passive BBMD autonomously detects active BBMD failure through monitoring mechanisms and automatically assumes the active role without requiring manual intervention. The system performs self-healing by automatically updating its status and continuing broadcast communication, eliminating the need for human operators to detect and replace failed BBMDs.
3Extent of automation
If BIP devices are configured as passive BBMDs, then automated failure detection and recovery is enabled, but device functionality complexity increases
Solution Approach 1:
Standard BIP devices are configured to perform multiple functions: normal BACnet communication operations and passive BBMD monitoring duties. This multi-functionality allows existing devices to serve dual purposes without requiring specialized hardware, enabling automated failure recovery while utilizing universal device capabilities already present in the network.
Solution Approach 2:
The passive BBMD configuration enables BIP devices to perform more than their traditional single function by adding monitoring and failover capabilities. This partial extension of device functionality allows the same device to handle both regular communication tasks and backup BBMD responsibilities, achieving automation without proportionally increasing complexity.
Data Source
AI summary
A global broadcast communication network system having a plurality of subnets. The system may incorporate a building and automation control network (BACnet) protocol. Each subnet may have a one active BACnet broadcast management device (BBMD) for broadcasting messages to other subnets. Also, there may be BIP (BACnet over IP) devices, such as controllers, tools and stations, in the subnets. One of the BIP devices in each subnet may be configured or enabled as a passive BBMD. If there is a failure of the active BBMD in a subnet, then the passive BBMD of the same subnet may detect the failure and assume the role of the active BBMD to minimize or eliminate possible disruption of communication across the subnets. Each BBMD may have and maintain a broadcast distribution table (BDT) which contains information about BBMDs in other subnets. Each BBMD may provide updated BDT information to the other BBMDs.