Re: Unknown mechanisms

On 2 September 2011 20:12, Murray S. Kucherawy wrote:

>> If an unknown mechanism is encountered, the correct result is
>> permerror.

> Fair enough.

There is no such thing as an "unknown mechanism".  The <mechanism>
syntax is a finite enumeration of known mechanisms.  Anything else
could be anything, a broken modifier, a funny TXT record unrelated
to v=spf1, or nobody knows what, except that it's no valid v=spf1.

> I'd like that to be explicit.  As it is now an implementer could
> decide that ignoring unknown mechanisms is simplest (and a common
> practice, such as in DKIM and its friends), leaving the remaining
> record parsable and usable.

I don't recall any DKIM syntax details, but I'd bet that it also
does not explicitly say that syntactical garbage cannot be parsed.

It would be odd to discuss IPv4 octets 256 or greater in prose, so
why would you wish to discuss non-existing mechanisms in prose?

I've never heard of any difficulties with this aspect of RFC 4408,
after all it was published when the proposals for other mechanisms
were long dead (for the reason stated by Scott).  IIRC you would
find some erroneous "unknown mechanism" syntax in old SPF drafts.

-Frank