Document introduction - Metasys - LIT-12012458 - Field Device - 13.0

Metasys IP Networks for BACnet/IP Controllers Technical Bulletin

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Technical Bulletin
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The Metasys BACnet/IP Controllers, including the CVE controllers designed for variable air volume (VAV) box application, the CGE general purpose application controllers, Advanced Application Field Equipment Controllers (FAC) and Variable Air Volume Modular Assembly (VMA) Controllers , greatly increase the number of Building Automation System (BAS) devices that can connect to IP networks. In planning an IP-based system, one approach is to engage the IT department, the traditional owner of a building's IP network. The IT department may be able to supply the large number of network switch ports and IP addresses that an all-IP BAS network needs. The cost of leasing these resources may be appreciable. Some IT departments may be unfamiliar with BACnet®. Previously, many broadcasts were limited to MS/TP trunks. IP broadcast messages are required for the Network Engines (network engines) BACnet Router to discover the BACnet/IP and other controllers connected directly to the BACnet/IP network. These broadcasts can put a burden on an IT network if the IT department has not had experience with BACnet/IP.

Another approach to meeting the need for more network switch ports and IP addresses is to develop an operational technology (OT) network. The distinction between IT and OT exists because IT departments are staffed to handle things like enterprise applications, office computing, email, telephony (voice and video), server rooms, and cyber security. OT is mostly interested in connecting machines. Some IT departments will be interested in OT networking and will work closely with Johnson Controls® on the building automation system. Sometimes there is no IT department at all, and Johnson Controls has to build a complete network.

This document looks at IT/OT networking broadly. It starts with topologies for connecting end devices to the network. Then it looks at network architectures that unite the end devices into a system. Several architectures are introduced, spanning varying degrees of IT/OT integration. Along the way, it raises issues, discusses how the system designer can manage them, and provides examples of network designs. Networking in general is a broad subject. For some of the architectures described in this document, the IP Network Wizard turns a plan into an implementation. This tool does not support BACnet/SC at this release. The IP Network Wizard will help you design networks like the ones shown in the examples. For designs that do not conform to the architectures given in this document, you either need experience with IP network design or consultations with someone who has experience with IP network design.

From Release 12.0 or later, the IP equipment controllers that are mentioned in this document can use the BACnet/IP or the BACnet/SC protocol. BACnet Secure Connect (BACnet/SC) is a new BACnet datalink ASHRAE 135-2020 Annex AB that provides secure message transport by using the standard IP application protocol, Secure WebSocket, which is an extension to HTTPS and runs over Transport Layer Security (TLS). For more information about the BACnet/SC protocol, refer to the BACnet/SC Workflow Technical Bulletin (LIT-12013959) .

A few words have particular meaning in this document:

describes the network in terms of the physical connections.
describes the network in terms of its logical connections and the relationships between its parts.
is an activity on paper that applies a network architecture to a specific network.
is an activity that takes the plan and specifies the details of its implementation. An engineering design tool, the IP Network Wizard, has been developed to help with this step of the process.
is the activity of implementing an element of the design in a piece of hardware. For example, we configure controllers, engines, switches, and switch ports. By extension, individual properties are configured as well.