Re: C-Bus encapsulation type

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

On Jun 26, 2017, at 7:35 PM, Daniel O'Connor <Daniel.O'Connor () schneider-electric com> wrote:

> > On 7 Jun 2017, at 17:32, Guy Harris <guy () alum mit edu> wrote:
> >
> > On Jun 6, 2017, at 8:51 PM, Daniel O'Connor <Daniel.O'Connor () schneider-electric com> wrote:
> > > I work for Clipsal (part of Schneider Electric) and have been developing a capture program and dissector for the 
> > > C-Bus protocol - https://en.wikipedia.org/wiki/C-Bus_(protocol)
> > >
> > > Can we get a link layer header type assigned for this?
> >
> > Yes, if we can get a specification for what the packets look like. :-)
>
> There's the rub the format is internal :(
>
> > Where is the format of the packets that would appear with this link-layer header type documented?
>
> It is mostly documented at http://training.clipsal.com/downloads/OpenCBus/Serial%20Interface%20User%20Guide.pdf
>
> Although the format is slightly different (hence the internal stuff).

If the capture program and dissector are solely for the use of Schneider and, possibly, its customers, and the 
dissector won't be open-source (which means "not a Wireshark dissector", given that Wireshark plugins have to be GPLed, 
unless the dissector is solely for use within Schneider), then a LINKTYPE_n/DLT_USERn value would be best.  I don't 
want to assign LINKTYPE_/DLT_ values to formats for which there isn't sufficient documentation for somebody to write 
code to parse the format (neither a tcpdump nor a Wireshark dissector counts as "documentation").

If the dissector will be open-source, then there's no reason not to have a publicly-available specification for the 
message format.
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