#82 BACnet BBMD vs Foreign Device

[Prasad Kulkarni]

H Steve,

As a protocol revision 19 device, it seems either BBMD or Non-BBMD with Normal and Foreign Mode are mandatory to have.

If the BACnet device is not a router, is it still mandatory to have these modes?
If yes, can we have Normal and Foreign Mode operations only as a Non-BBMD device?

What steps we need to enable in the stack to have the Foreign Mode functionality and does that require a timer to be maintained on device's side if majority of the work is done by BBMD devices for which we will be registering as a foreign device?

Many Thanks,
Prasad

[Steve Karg]

For BACnet/IP, it is required (by BTL) that at least non-BBMD and Foreign Mode are supported so that any IP device can be used on any IP subnet - alone - and be able to communicate with the rest of the BACnet/IP network. If the BACnet/IP device didn't support BBMD or Foreign Mode, it would require another BACnet/IP device that supports BBMD.

There is an example of using the defines to build the example client and server applications with different BBMD configurations. The non-BBMD and Foreign Mode is 'client':

ifeq (${BBMD},none)
BBMD_DEFINE = -DBBMD_ENABLED=0
endif
ifeq (${BBMD},server)
BBMD_DEFINE = -DBBMD_ENABLED=1
endif
ifeq (${BBMD},client)
BBMD_DEFINE = -DBBMD_ENABLED=0 -DBBMD_CLIENT_ENABLED
endif
ifeq (${BBMD},full)
BBMD_DEFINE = -DBBMD_ENABLED=1 -DBBMD_CLIENT_ENABLED
endif

Yes, a maintenance timer is needed to keep registering as a Foreign Device. The example for this timer function is in the dlenv.c module for the example applications.

[Prasad Kulkarni]

Thanks Steve!

Prasad.

On Mon, 10 Jun 2024 at 17:46, Steve Karg skarg@users.sourceforge.net
wrote:

For BACnet/IP, it is required (by BTL) that at least non-BBMD and Foreign
Mode are supported so that any IP device can be used on any IP subnet -
alone - and be able to communicate with the rest of the BACnet/IP network.
If the BACnet/IP device didn't support BBMD or Foreign Mode, it would
require another BACnet/IP device that supports BBMD.

There is an example of using the defines to build the example client and
server applications with different BBMD configurations. The non-BBMD and
Foreign Mode is 'client':

ifeq (${BBMD},none)
BBMD_DEFINE = -DBBMD_ENABLED=0
endif
ifeq (${BBMD},server)
BBMD_DEFINE = -DBBMD_ENABLED=1
endif
ifeq (${BBMD},client)
BBMD_DEFINE = -DBBMD_ENABLED=0 -DBBMD_CLIENT_ENABLED
endif
ifeq (${BBMD},full)
BBMD_DEFINE = -DBBMD_ENABLED=1 -DBBMD_CLIENT_ENABLED
endif

Yes, a maintenance timer is needed to keep registering as a Foreign
Device. The example for this timer function is in the dlenv.c module for
the example applications.

---

[support-requests:#82]
https://sourceforge.net/p/bacnet/support-requests/82/ BACnet BBMD vs
Foreign Device

Status: open
Group: release
Created: Mon Jun 10, 2024 06:22 AM UTC by Prasad Kulkarni
Last Updated: Mon Jun 10, 2024 06:22 AM UTC
Owner: nobody

H Steve,

As a protocol revision 19 device, it seems either BBMD or Non-BBMD with
Normal and Foreign Mode are mandatory to have.

If the BACnet device is not a router, is it still mandatory to have these
modes?
If yes, can we have Normal and Foreign Mode operations only as a Non-BBMD
device?

What steps we need to enable in the stack to have the Foreign Mode
functionality and does that require a timer to be maintained on device's
side if majority of the work is done by BBMD devices for which we will be
registering as a foreign device?

Many Thanks,
Prasad

---

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[Prasad Kulkarni]

Hi Steve,

A device having B-ASC profile for a specific application can have BBMD mode alongside Foreign Device Registration Support or BBMD is generally a device like mostly routers / networking devices who manages the tables, traffic, etc?

[Steve Karg]

BBMD table support in a device depends on how you want to bring your device to your customer market and your device available RAM and non-volatile storage resources.

The BACnet/IP devices I've developed typically only included Foreign Device Registration because the additional RAM and non-volatile storage used by BBMD tables was scarce and would make the product cost more.