Thanks for this well-written document

ART topics:

The document does not touch on any of the typical ART review issues; times are relative in well understood units, and versioning, formal language (ASN.1, which is outside of my experience to check) and encoding infrastructure (struct) follows TLS practices.

General comments:

* The introduction of this mechanism gives the impression of a band-aid applied to a PKI ecosystem that has accumulated many limitations as outlined in section 3.1. The present solution appears good, but if there is ongoing work on the underlying issues (even experimentally), I'd appreciate a careful reference to it.

* Section 7.6 hints at the front end querying the back-end for creation of new DCs -- other than that, DC distribution (neither push- nor pull-based) is discussed. If there are any mechanisms brewing, I'd appreciate a reference as well.

Please check:

* The IANA considerations list "delegated_credential" for CH, CR and CT messages. I did not find a reference in the text for Ct, only for CH and CR.

Editorial comments:

* (p5) "result for the peer.." -- extraneous period.
* (p9, p15, p16) The "7 days" are introduced as the default for a profilable prarameter, but later used without further comment.