159RE: [bacnet-oswg] CLB-013 - Network Port Object
- May 26, 2011
Thanks for the feedback. The first 3 points are cut and dried and will be addressed prior to Montreal.
As far as the 4th point...
I loathe to re-open this can of worms because it's going to be a big discussion no matter how we slice it.
The following is from an email from David Fisher on 7-Sep-2010. I believe this points to the requirement of a single home for devices in clause 5.1.
For those of you wanting to know where the standard defines this binding idea it is
described in detail at the end of 5.1 (since the first 1995 standard):
A "BACnetDevice" is any device, real or virtual, that supports digital communication
using the BACnet protocol. Each BACnet Device contains exactly one Device Object,
as defined in 12.10. A BACnet Device is uniquely located by an NSAP, which consists
of a network number and a MAC address.
But, as Bill Swan points out on 20-Jan-2011:
The phrase says “located” and not “homed.” A multi-homed router can still be uniquely
“located” (found) at a single address by some other device, no matter where that
device is in the system. Two devices in different locations have different NSAPs for
the target device in their tables, but the system still works.
As you pointed out, also on 20-Jan-2011:
In post meeting discussions, Bill and I agreed that the issue has little impact on
real interoperability as shown by numerous real-world installations that show no ill effects
I agree with your point about interoperability. It shouldn't matter one way or another to the rest of the network whether the binding looks like it's a routed address or not -- assuming the routing information is correct.
Frankly, I don't care either way and I really don't want to hold this proposal up because of this ages long argument.
So, how about a "straw poll" for one of the following 2 options:
1) The property is marked as required currently. How about if we just make it optional? Then those who use the "single homed" approach can use it, and those who use the "multi homed" approach won't.
2) Remove it entirely. I can make an argument for this, because how is it used anyway? What's the use case for this property?
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