Hi!

draft-ietf-dnsop-caching-resolution-failures
Review type:	intdir - Telechat review
Reviewer:	Carlos Pignataro 

I find this a complete and well written document. Only some minimal nits for your consideration:

2.  Conditions That Lead To DNS Resolution Failures

CMP> "to"               ^^^^


3.2.  Caching

   Resolvers SHOULD employ an exponential or linear backoff algorithm to
   increase the cache duration for persistent resolution failures.  For
   example, the initial time for negatively caching a resolution failure
   might be set to 5 seconds, and increased after each retry that
   results in another resolution failure, up to a configurable maximum,
   not to exceed the 5 minute upper limit.

CMP> "5-minute"


3.3.  Requerying Delegation Information

   The problem of aggressive requerying to parent zones is not limited
   to queries of type NS.  This document updates the requirement from
   section 2.1.1 of [RFC4697] to apply more generally: Upon encountering
   a zone whose name servers are all non-responsive, a resolver MUST
   cache the resolution failure.  Furthermore, the resolver MUST limit
   queries to the non-responsive zone's parent zone (and other ancestor
   zones) just as it would limit subsequent queries to the non-
   responsive zone.

CMP> "(and *to* other ancestor"


1.2.  Related Work

   An expired Internet Draft describes "The DNS thundering herd problem"

and

10.2.  Informative References

   [thundering-herd]
              Sivaraman, M. and C. Liu, "The DNS thundering herd problem
              (expired Internet Draft)", June 2020,


CMP> s/Internet Draft/Internet-Draft/g?

Thanks again!

Carlos.