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6. SVCB-Compatible RR Types

An RR type is called "SVCB-compatible" if it permits an implementation that is identical to SVCB in its:

  • RDATA presentation format
  • RDATA wire format
  • IANA registry used for SvcParamKeys
  • Authoritative server Additional section processing
  • Recursive resolution process
  • Relevant Class (i.e., Internet ("IN") [RFC1035])

This allows authoritative and recursive DNS servers to apply identical processing to all SVCB-compatible RR types.

All other behaviors described as applying to the SVCB RR also apply to all SVCB-compatible RR types unless explicitly stated otherwise. When following an AliasMode record (Section 2.4.2) of RR type $T, the follow-up query to the TargetName MUST also be for type $T.

This document defines one SVCB-compatible RR type (other than SVCB itself): the HTTPS RR type (Section 9), which avoids Attrleaf label prefixes [Attrleaf] in order to improve compatibility with wildcards and CNAMEs, which are widely used with HTTP.

Standards authors should consider carefully whether to use SVCB or define a new SVCB-compatible RR type, as this choice cannot easily be reversed after deployment.

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