Re: [Bacnet-developers] Multi device support using the gateway demo

[Steve K. <st...@ka...>]

Hi Derek,

To add to what Edward stated: the gateway example in the open source stack
was contributed long before BACnet had standardized what a virtual network
gateway could and could not do and has not been updated to meet the current
requirements.  See Addenda 135-2012al:
http://www.bacnet.org/Addenda/Add-135-2012al.pdf

A gateway can also use the "all gateway objects in a single device" model
and doesn't have to implement the virtual network. I use this technique in
many gateway products and hotel number the objects from devices behind the
gateway (i.e. hotel floor 1 room 1 = room 101, so device 1 property 1 =
object 101 or some other such number scheme).

Best Regards,

Steve


On Mon, Aug 13, 2018 at 11:37 AM, Edward Hague <ed...@ba...> wrote:

> Derek
>
> You are on the right track. Be aware that the stack can support multiple
> datalinks, but as it stands, only one at a time.
> The gateway model is sufficient to "pretend" that the multiple virtual
> devices are on a virtual network with a Network Number behind a virtual
> router sufficiently well to pass e.g. BTL with this approach.
> However, to do so, you will need to add an Application Entity to the
> virtual router to respond to a "Who-Is" and present a Device Object.
> Also you will need to allow the user to configure the Virtual Network's
> Network Number.
> And you will not be able to support NAT with this approach. To support NAT
> you will need to add a fully implemented Virtual Router. But this is a
> corner case, but will be needed to support e.g. VPNs that filter broadcasts
> (most of them). _This_ is not trivial.
> Ed
>
>
> On Sat, Aug 11, 2018 at 6:47 AM, Derek Noffke <de...@pu...>
> wrote:
>
>> I have been looking at the gateway code to see how it can be used to
>> support multiple device objects.
>> It seems that the incoming requests are passed down to the usual single
>> device request handlers such as ai.c for example.
>>
>> The code in ai.c can then be changed to first query the target device ID
>> via a call to Routed_Device_Object_Instance_Number() to select which
>> device the ai object_instance belongs to.
>>
>>
>>
>> 1)      Am I correct so far?
>>
>> 2)      Is there more that needs to be addressed?
>>
>>
>>
>> Regards,
>>
>>
>>
>> Derek
>>
>>
>>
>>
>>
>>
>>
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>
>
> --
>
>
>
>
> *Edward Hague*(650) 924 1395
> *BACnet Interoperability Testing Services, Inc*
> 809 B Cuesta Drive, Suite 2180
> Mountain View, CA 94040-3667
> www.bac-test.com
> ed...@ba...
>
>
>
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