Re: Introducing an FT_OUI type, should it be an integer or bytes?

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

On Aug 19, 2017, at 4:18 PM, Richard Sharpe <realrichardsharpe () gmail com> wrote:

> I have a change up for review that introduces a new type, FT_OUI.
>
> It works. However, the big question is that it changes the current
> practice from the OUI being an INT24 to being BYTES.
>
> This breaks backward compatibility I imagine.
>
> Is this a big issue?

Some issues I see are:

        1) Filter expressions that compare an OUI field against a 24-bit integral value might become invalid - but you 
might be able to make that work by allowing FT_OUI be represented, in filters, either as an integral value or as 3 
octets (allowing 0C0102, 0C:01:02, etc.).

        2) OUIs are used in the 802.2 LLC dissector when processing the SNAP header; a dissector can register a field 
to use for the PID for a given OUI, and a dissector table to be used for the PID's value, passing llc_add_oui() an 
integral value for the OUI.  We could continue to allow that, and just convert the 3-octet value to an integral value 
in the 802.2 dissector and use that integral value to look up the registered information.
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