In the world of smart buildings, the BACnet protocol has become the standard for ensuring interoperability between HVAC, lighting, security, and energy management systems. But within BACnet, there are different communication methods — the two most widely used being BACnet/IP and BACnet MS/TP.
Choosing between them is not always straightforward: should you favor the simplicity and lower cost of MS/TP, or the speed and scalability of BACnet/IP? The right choice depends on the project size, budget, and future growth requirements. If you are new to the BACnet standard itself, we recommend starting with our guide What is BACnet?, which explains the protocol’s foundations and why it became the reference in building automation.
Both BACnet/IP and BACnet MS/TP are transport methods defined by the BACnet protocol. They allow devices from different manufacturers to exchange building automation data, but they rely on very different physical and logical layers.
| Protocol | Main Characteristics |
|---|---|
| BACnet/IP | Fast, scalable, integrates with IT infrastructure |
| BACnet MS/TP | Low-cost, simple RS485 bus, limited speed and scalability |
RS485 is an electrical standard for serial communication that defines how devices exchange data over twisted-pair wiring. It is widely used in industrial and building automation because of its simplicity, robustness, and low cost.
Key characteristics of RS485:
| Feature | Description |
|---|---|
| Topology | Multi-drop bus (daisy chain) |
| Max distance | ~1200 meters (at lower speeds) |
| Typical speed | Up to 115.2 kbps for BACnet MS/TP |
| Use case | Backbone for BACnet MS/TP networks |
BACnet MS/TP (Master-Slave/Token-Passing) has been the backbone of many building automation projects for decades. Because it runs on RS485 wiring, it is inexpensive, simple to deploy, and still widely supported by controllers and field devices. However, it comes with speed and scalability tradeoffs.
| Benefit | Impact |
|---|---|
| Low cost | Affordable wiring and devices |
| Simplicity | Easy to install for small projects |
| Limited speed | Max ~115.2 kbps, slows with device count |
| Scalability | Best for small/medium buildings |
BACnet/IP uses standard Ethernet and IP networks, the same infrastructure as IT systems. This makes it the natural choice for large-scale or future-oriented building automation projects. It allows BACnet data to travel across LANs, WANs, and even the internet when secured properly.
| Benefit | Impact |
|---|---|
| High speed | Fast communication across Ethernet/IP |
| Scalability | Thousands of devices across large sites |
| Integration | Seamless with IT & IoT systems |
| Complexity | Higher costs and need for IT expertise |
Both protocols are widely used, but the right choice depends on your project size, performance needs, and future plans. Here’s a side-by-side breakdown:
MS/TP: RS485 serial bus
IP: Ethernet / IP networks
MS/TP: Up to 115.2 kbps
IP: Up to 1 Gbps (or higher)
MS/TP: Daisy chain (bus)
IP: Star / switched networks
MS/TP: Dozens of devices
IP: Thousands of devices
MS/TP: Lower (RS485 wiring)
IP: Higher (Ethernet infrastructure)
MS/TP: Simple, but slower
IP: Complex, requires IT expertise
MS/TP: Limited to automation devices
IP: Full IT/IoT convergence
MS/TP: Small/medium buildings
IP: Large facilities, campuses, smart cities
For a deeper dive into how BACnet communication works at different layers, you can explore our article How does BACnet work?.
The decision between BACnet/IP and BACnet MS/TP often comes down to the scale of the project and how much integration with IT infrastructure is required. Here are some typical scenarios:
As the building automation industry shifts toward greater integration with IT, many experts emphasize the long-term benefits of BACnet/IP.
“Moving to BACnet/IP is not only about speed, it’s about convergence between IT and OT worlds. This shift enables true scalability, advanced analytics, and IoT integration — paving the way for smarter, future-ready buildings.“
This perspective highlights why many organizations see BACnet/IP not just as a protocol upgrade, but as a strategic step toward digital transformation in building management.
Choosing between BACnet/IP and BACnet MS/TP depends on the balance between cost, scale, and future needs.
As Olivier Hersent noted, the move toward BACnet/IP is not just about faster communication, but about bridging IT and OT worlds. This convergence makes building automation part of the broader digital ecosystem — future-proof, data-driven, and ready for smart cities.
Ultimately, most organizations will continue to use both protocols in hybrid deployments, with MS/TP supporting legacy or localized devices, while BACnet/IP drives the backbone of modern building automation networks.
BACnet/IP uses Ethernet and IP networks, offering high speed and scalability, while BACnet MS/TP runs over RS485 serial communication, making it slower but simpler and cost-effective.
BACnet MS/TP typically supports up to 115.2 kbps, which is sufficient for small to medium installations but much slower compared to Ethernet-based BACnet/IP.
Yes. MS/TP (Master-Slave/Token-Passing) is specifically defined to run over RS485 twisted-pair wiring, which provides a reliable multi-drop bus topology.
BACnet/IP is recommended for large-scale projects with many devices, multiple buildings, or where integration with IT and cloud services is required.
Yes. BACnet/IP requires Ethernet switches, routers, and IP-capable devices, making it more expensive to deploy. However, the investment pays off with scalability and easier diagnostics.
Yes. Many gateways and routers exist to connect MS/TP networks to BACnet/IP, allowing gradual migration as systems expand or modernize.
BACnet MS/TP is best for dozens of devices. Adding too many devices slows communication due to token-passing delays. BACnet/IP scales to thousands of devices.
BACnet/IP should be secured with firewalls, VPNs, and encryption. Since it runs on standard IT infrastructure, it inherits the same cybersecurity risks as other IP systems.
About Actility
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