RE: [bacnet-ip-wg] NPO question for consideration
That sounds like a good approach to me.
There are at least THREE options, each of which may be appropriate in different cases
1) 6-octet BVLL address is exactly what we want for the MAC_Address property. That is the address used generically and is an octet string for any datalink, and it is nobody’s business whether there IS a UDP port. On BACnetIP, MAC_Address should be read-only.
2) BACnetHostNPort is great for cases like BDTs where each entry is an IP address or host name, and may use a different UDP port
3) UDP port as its own property may be clearest way to deal with the DHCP case, where the user can assign the UDP port but NOT the address. It
might also make sense if there were multiple IP addresses that all used (and HAD to use) the same UDP port: if you used BACnetHostNPort for these addresses, you would have the annoying/odd behavior that writing to one property would change parts (ports) or other properties.
I think that this works pretty well
· MAC_Address is a read-only octet string
· IP_Address is JUST an IP address (aka octet string of length 4), read-only if DHCP is enabled, or on something like a workstation without admin rights where you CAN’T change the IP address; else writable to set the IP address.
· Subnet_mask, default_gateway etc. are also octet string of length 4
· UDP port is an edited unsigned integer
· BDT entries are BACnetHostNPort, since we want the hostname option and may need unique ports for each entry
I reviewed older versions of the NPO (when it was still a young proposal) and I can't find a version that has a separate IP Address and UDP port property.
I guess my fear about "simply" adding this properties is that it'll cause a storm of "Why aren't these properties combined and declared as BACnetHostNPort?" type discussions.
In my mind, they should be as follows:
BACnet_IP_Address OCTET STRING
BACnet_IP_UDP_Port OCTET STRING
Both of which are conveyed most significant byte first.
The bigger issue is what happens to the value of the MAC_Address property in the case of an IP device? Does this value automagically take on the combined values of the IP_Address property and the UDP_Port property? I have note that says "MAC_Address becomes read only for BACNET_IP", but is this still the direction we want to go know that it's likely to generate more comments?
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