NSEC and NSEC3: TTLs and Aggressive Use
draft-ietf-dnsop-nsec-ttl-05

Please make RFC 8174 a normative reference rather than an informative one.  (RFC 2119 already is, but the two documents together make up BCP 14, so I don't think you can split them as was done here.)

Thank to Tiru Reddy for the SECDIR review.

Thanks for addressing my COMMENT feedback.

I put a (small) handful of editorial suggestions up at
https://github.com/PowerDNS/draft-dnsop-nsec-ttl/pull/11 .

Section 3.1, etc.

   |  The TTL of the NSEC RR that is returned MUST be the lesser of the
   |  MINIMUM field of the SOA record and the TTL of the SOA itself.
   |  This matches the definition of the TTL for negative responses in
   |  [RFC2308].  A signer MAY cause the TTL of the NSEC RR to have a
   |  deviating value after the SOA record has been updated, to allow
   |  for an incremental update of the NSEC chain.

I don't think I understand what a "deviating value" would be (and in
which direction it would deviate).

Section 3.4

   |  A resolver that supports aggressive use of NSEC and NSEC3 MAY
   |  limit the TTL of NSEC and NSEC3 records to the lesser of the
   |  SOA.MINIMUM field and the TTL of the SOA in a response, if
   |  present.  It MAY also use a previously cached SOA for a zone to
   |  find these values.

The original 8198 has "SHOULD reduce", but now we only have "MAY limit".
Why should the requirements level be weaker for the new, more-correct,
guidance?

Section 4

   If signers & DNS servers for a zone cannot immediately be updated to
   conform to this document, zone operators are encouraged to consider
   setting their SOA record TTL and the SOA MINIMUM field to the same
   value.  That way, the TTL used for aggressive NSEC and NSEC3 use
   matches the SOA TTL for negative responses.

Are there any negative consequences of such a move that would need to be
weighed against the stated benefits?

Section 8

Why is RFC 8174 only an informative reference?  Shouldn't it be given
the same treatment as RFC 2119?

No need for a response on these:

Please expand TTL and SOA on first use.

Hi,

Thanks for this document.

Regarding:

3.4.  Updates to RFC8198

   [RFC8198] section 5.4 (Consideration on TTL) is completely replaced
   by the following text:

   |  The TTL value of negative information is especially important,
   |  because newly added domain names cannot be used while the negative
   |  information is effective.
   |  
   |  Section 5 of [RFC2308] suggests a maximum default negative cache
   |  TTL value of 3 hours (10800).  It is RECOMMENDED that validating
   |  resolvers limit the maximum effective TTL value of negative
   |  responses (NSEC/NSEC3 RRs) to this same value.
   |  
   |  A resolver that supports aggressive use of NSEC and NSEC3 MAY
   |  limit the TTL of NSEC and NSEC3 records to the lesser of the
   |  SOA.MINIMUM field and the TTL of the SOA in a response, if
   |  present.  It MAY also use a previously cached SOA for a zone to
   |  find these values.

I'm not a DNS expert, and this is just a non binding comment, but I was wondering why it is only "MAY" limit the TTL on NSEC and NSEC3 records to the lesser of the SOA.MINIMUM field and the TTL of the SOA in a response rather than a "SHOULD".

Regards,
Rob