What B-DAP Is
A BACnet device profile is a standardized capability level: a checklist of things a device must be able to do before it can wear the label. B-DAP (BACnet Device Address Proxy) is defined in Annex L of ANSI/ASHRAE 135-2024 (clause L.7.7) as a router that provides device address proxying: it answers discovery on behalf of devices on its directly connected networks that cannot or do not respond for themselves.
It is a Miscellaneous-family profile, so a device can claim it alongside a profile from another family. The checklist items are BACnet Interoperability Building Blocks (BIBBs); a device documents its claim in its PICS (Protocol Implementation Conformance Statement).
Where It’s Used
B-DAP fits a router or gateway that speaks for quiet devices behind it.
- Proxying for sleeping devices. Answering Who-Is with I-Am on behalf of low-power or intermittently connected devices that would otherwise miss the discovery.
- Bridging constrained segments. Presenting devices on a slow or constrained network so a client on the backbone can discover them promptly.
- A proxy built into a router. A device carrying the proxy function alongside its routing role, driven by the
Device_Address_Proxy_Enableproperty of its Network Port objects.
Required Services
The table below is the exhaustive service set required by the B-DAP BIBBs. Initiates means the device sends the request or notification; Executes means the device receives and acts on it (responding, for confirmed services). BIBB codes encode the same split: a -A BIBB is the initiating side, a -B BIBB the executing side. A - means the profile does not require that direction; a device may still support it.
| Capability area | Service | Required by BIBB | Initiates | Executes |
|---|---|---|---|---|
| Data sharing | ReadProperty | DS-RP-B, DM-DAP-B | Yes | Yes |
| Data sharing | WriteProperty | DS-WP-B, DM-DAP-B | Yes | Yes |
| Data sharing | ReadRange | DM-DAP-B | Yes | - |
| Data sharing | AddListElement | DM-DAP-B | Yes | - |
| Data sharing | RemoveListElement | DM-DAP-B | Yes | - |
| Device and network management | Who-Is | DM-DDB-B, DM-DAP-B | - | Yes |
| Device and network management | I-Am | DM-DDB-B, DM-DAP-B | Yes | - |
| Device and network management | Who-Has | DM-DOB-B | - | Yes |
| Device and network management | I-Have | DM-DOB-B | Yes | - |
The defining behavior is proxied discovery. The DM-DAP-B requirement means the device answers Who-Is and sends I-Am on behalf of the devices it proxies, and it maintains the proxy state using the initiating services above. Proxying is enabled per network through the Device_Address_Proxy_Enable property of the Network Port object.
Related Profiles
| Profile | How it relates to B-DAP |
|---|---|
| B-RTR | Router: the base routing role; a B-DAP is a router that adds proxying |
| B-BBMD | Broadcast Management Device: another network-infrastructure Miscellaneous profile |
| B-GW | Gateway: presents non-BACnet systems, a different infrastructure job |
What Chipkin Provides
The CAS BACnet Stack implements device address proxying (DM-DAP-B) and the data-sharing and discovery services the B-DAP profile requires. Talk to us about building or integrating a B-DAP device on the stack.