Making the BACnet-N2 Router Smarter

It seems like a broken record but I have to say it again - it’s been a very busy year at S4. Our integration partners have been taking on larger and more complex projects, and deploying BACnet applications that are more demanding in terms of the number of points and the frequency of access.

Smart Data Points

In an earlier article, I shared the new capabilities introduced by our Smart Data Points and how they enable N2 devices to masquerade as other manufacturers’ devices. This capability has been extensively used and, in the process, has made the integrator’s task much less labor intensive because they can now make use of their native graphics, applications, and navigation structure. In addition, the user experience became consistent across interfaces for all devices.

Isolating the N2 Field Bus

The S4 Open: BACnet-N2 Router and OPC-N2 Router have always included algorithms to protect the N2 bus from excessive utilization. The BACnet-N2 Router was designed as a passive actor in the network responding to transactions from a BACnet/IP client and performing the protocol and data translations on the fly to make the downstream legacy protocol transparent to the requesting upstream protocol. Algorithms have been in place since day one to throttle the demand so that the N2 field bus does not exceed its capacity and that all upstream interfaces receive equal access to the field bus. We often describe this capability as acting as the gatekeeper for access to the N2 bus.

To keep up with the increasing demands for data we needed to decouple the upstream interfaces from direct reliance on access to the downstream (field bus) interfaces by adding a caching service to the core services of the appliance. Adding this service impacted every other service and capability in the system. This required an extensive development and test effort. In the process we improved the portability of the code, system performance, and overall reliability of the system.

rotocols, providing a balance between response time, data aging, and protecting the N2 bus from excessive utilization. The cache also isolates the upstream protocols from the latency of the slow legacy N2 bus as some client environments mistakenly interpret this natural latency as timeout problems. With the cache enabled the upstream clients see instantaneous responses to their transactions after initialization of the caching service on first use.

BACnet COV Services

Support for both confirmed and unconfirmed COV has been frequently requested and was closely related to work we were doing with caching. These enhancements remove the responsibility of periodically polling for data updates from the BACnet client.

The BACnet-N2 Router takes on the responsibility of monitoring data points for changes and asynchronously notifies the BACnet client when changes occur. As with all advanced BACnet services, we leave it to the integrator to control if these services are available for their project.

COV services can be used natively against the N2 points or in conjunction with the transparent caching service described above. In cases where the BACnet client does not support COV subscription, the BACnet-N2 Router can significantly improve the performance of the integration utilizing the transparent caching service.

BACnet Enterprise Networking Support

In order to keep pace with these larger, more sophisticated projects we added support for BACnet BBMD services and Foreign Device Registration services. The BACnet-N2 Router is capable of acting as either the provider or the consumer of these services.

These capabilities enable the integrator to build complex BACnet Intranets with the BACnet-N2 Router, without having to add additional hardware for the sole purpose of providing BBMD services. An example would be installing a S4 Open: BACnet-N2 Router at an elementary school in which the IT department had allocated a separate IP subnet to each building in the school district. Naturally, the BACnet-N2 Router will provide its primary service of presenting each N2 device and its associated points as an emulated BACnet device on a virtual BACnet network. But, in addition, it can become a player in the larger BACnet Intranet serving the entire school district utilizing either BBMD or Foreign Device Registration capabilities.

S4 Open Management Console Enhancements

All of the above enhancements involved huge amounts of development and testing. However, sometimes smaller incremental amounts of effort at the right time result in great benefits for the integrator or building owner. That is the case with this enhancement to the S4 Open Management Console. We have had frequent requests to add the BACnet object type, instance number, and present value or points to the detail pane in the Building Control Network folder. The Caching and COV enhancements described above laid the groundwork for us to add this enhancement in a way that does not impact the primary mission of the system, that is serving up data to BACnet clients.

Some Pain, Lots of Gain

All of this gain was not without some pain. Because we were working at the core of the system for many of these enhancements, the changes impacted almost every function and service in the system and mandated a larger than anticipated investment in Q/A testing in the S4 test lab. The final testing happened at our early adopter sites where the systems were exposed to real world situations. Some of the enhancements required a signifcant amount of additional development to make sure that they worked properly in all situations. Our thanks go out to the S4 Integration Partners and building owners who supported these efforts. It’s been a great year from the standpoint of what we accomplished. But, we simply had to put the development effort for multiple new integrations on hold to focus on what we had to get done for our flagship product and existing customers.

Some of these enhancements are installed at production sites for early adopters. Others are in various stages of Q/A test, customer field test, and joint testing with some of our largest partners. They will all be delivered with the next production release of the system. Current customers who have active Software Assurance agreements are eligible to upgrade their systems to take advantage of these great improvements in system capability.