Re: Building control standards

[Kerry Lynn <[e-mail]>]

On Wed, May 2, 2012 at 9:55 AM, Ole Trøan <[e-mail]> wrote:

> Kerry,
>
> apologies for sending this to you direct. partially a person interest (as
> I'm refurbishing a house), but also of professional interest.
>
> with regards to the various building control system standards. are BACnet,
> instabus, EIB, KNX all basically the same, and covered by
> draft-ietf-6man-6lobac-01?
>
> cheers,
> Ole


Hi Ole,

No problem.  I am not familiar with some of the standards you mention.
The problem comes in when these "last meters" protocols develop their own
proprietary data links.  BACnet is in that camp currently with MS/TP, which
is one of several data links that it supports but the only one that does not
already have a "IPv6 over foo" RFC.  As the larger vision is to transition
BACnet to native IPv6 in the future, I believe that draft-ietf-6man-6lobac
is a necessary step on that path since it is so widely deployed in
commercial
building automation systems.  It is about a factor of 10 less costly than
ethernet per driver, can cover long distances (1000-1200 m), and has a
sufficient data rate for the BAC application (up to 115.2 kpbs).

That said, in conjunction with changes being made in parallel to the data
link (through a BACnet standard change proposal), I think that MS/TP can
fill a niche at the low end of wired data links (similar to the niche that
6LoWPAN
fills in wireless) and will transport arbitrary IPv6 packets up to 1500
octets
in length (not including the IPHC dispatch header, and depending on link
MTU setting).  To the extent that the standards you mention will exchange
their application data using standard IP transports, and the required data
rate is 115.2 kbps or less, then IPv6 over MS/TP should be a viable option.

Hope that answers your question, -K-