John Levine wrote:
"ADSP records always start with 'dkim=', syntax:
There aren't enough bulldozers in the world to drain this swamp.
with the real problem: "Depending on the size of all wildcard TXT
records combined the DNS reply won't fit into an UDP datagram, and
might not make it to the party interested in the ADSP TXT record."
No kidding. The IETF has so far carefully avoided the disreputable
practice of inventing faux record types by subtyping TXT with a prefix
string. (SPF and Sender-ID don't count, being experimental.) It's an
awful idea for a variety of reasons, starting with the non-existence
of a prefix registry and most importantly that every newly defined
prefix would increase the chance of overflow, thereby breaking the
users of existing prefixes.
I agree that subtyping is something to be avoided; it's one of the
reasons that ADSP records go into the _adsp._domainkey subdomain of the
subject domain. But wildcard TXT records do exist, and we have seen
them (typically wildcard SPF records) returned in response to DKIM key
queries and we will get them in response to ADSP queries for
non-existent domains as well.
That being the case, requiring that ADSP records always start with
something distinctive such as 'dkim=' would allow an ADSP checker to
quickly ignore an unintended TXT record.
Doesn't it make sense to add the requirement for efficiency, not for
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