Re: [libpcap] New DLT value Request - Wattstopper DLM (#401)

[Guy Harris <guy () alum mit edu>]

On Jan 9, 2015, at 8:08 AM, Steve Karg <skarg () users sourceforge net> wrote:

> Hello Guy,
>
> > > The Family/Address/IR field contains 3-bits of family code, 2-bits of
> > > address mode, 2-bits of IR (infrared) routing, and 1-bit unused.
> > > The 8 Legrand NITOO families are 000=CAD Filaire, 001=TopDog, 010=CAD RF,
> > > 011=CAD PLC, 100=CAD IR, 101=DLM, 111=escape, and 111=DLM Bootloader).
> > > This document only describes the DLM family.
> >
> > Are the fields following the Family/Address/IR field dependent on the family code?  Or can the rest of the packet, 
> > with the possible exception of the opcode and payload, be parsed the same way regardless of the family code?
>
> Yes, the fields following the Family code are dependent on the Family code.

I.e., following the Family/Address/IR field, other families might not have the Sequence ID, Source and Destination MAC 
addresses, Opcode, and Payload Length followed by Payload?

Is the checksum family-code independent or might packets with other family codes not have it (or calculate the checksum 
differently)?

> > Are the family codes dependent on the hardware being used?
>
> Yes, the Family codes are dependent on the hardware.  The WattStopper
> DLM hardware uses a USB interface:
> http://www.wattstopper.com/products/digital-lighting-management/configuration-tools/dlm-computer-interface-tools-and-software.aspx
> and also tunnels the DLM packets in BACnet messages.
>
> Another Family is CAD PLC, part of Open-NITOO, but I don't know the
> hardware interface:
> http://www.myopen-legrandgroup.com/cfs-filesystemfile.ashx/__key/telligent-evolution-components-attachments/00-212-01-00-00-03-46-60/U3838B_5F00_Specifications.pdf

What I meant was that you said "The 8 Legrand NITOO families are ..." - is this a protocol used only by Legrand, so 
that those are the only family codes used, or are there other vendors who might have their own set of families and 
family codes, different from the Legrand ones?

> The LRC does not cover the Dongle Code or Packet Delay or Preamble.

I.e., it checksums packet data starting at the Family/Address/IR field and continuing through the end of the Payload 
field?
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