[DNSOP] DELEXT: Proposed Delegation Type Ranges

Hi all,

After the discussions over the past few weeks, the authors of DELEG and DELEXT have converged on two additional ranges (Ranges 2 and 3) of Delegation Types, distinguished by how they affect the contents of a referral:

Range 1: NS-Omitting Delegation Types
Range 2: NS-Preserving Delegation Types
Range 3: On-Demand Delegation Types
Range 4: Private Delegation Types

Range 1: NS-Omitting Delegation Types
A Delegation Type in this range causes the NS RRset to be omitted from a referral. When a delegation contains Delegation Types from this range, an authoritative server MUST NOT include the NS RRset in a referral, even if it exists at that delegation point.

Note that the DELEG record will be allocated from this range (Range 1).

Range 2: NS-Preserving Delegation Types
A Delegation Type in this range does not alter the inclusion of the NS RRset in a referral. When a delegation contains Delegation Types from this range, and none from Range 1, an authoritative server MUST include the NS RRset in the referral, together with the Delegation Type RRsets. If a delegation also contains Delegation Types from Range 1, the Range 1 rule takes precedence: the authoritative server MUST NOT include the NS RRset in the referral.

Note that Delegation Types from Range 1 and Range 2 are included in a referral when the DE bit is set to 1.

Range 3: On-Demand Delegation Types
Delegation Types in this range are not included in referrals. An authoritative server MUST NOT include Delegation Types from this range in a referral. Delegation Types in this range MUST be explicitly queried.

Range 4: Private Delegation Types
Private Use in accordance with RFC 8126. Delegation Types from this range follow the rules for Range 3. 

This seems to capture the distinction we have converged on without assigning semantics to individual Delegation Types beyond their interaction with referrals.

We believe this four-range approach provides a good balance between usefulness, avoiding redundant information in referrals, and deployability, while retaining sufficient flexibility to accommodate future Delegation Types and delegation mechanisms that we cannot anticipate today.

Subsequently, the DELEXT draft will read:

Decimal  Hex      Registration Procedures   Note

61440-   0xF000-  Expert Review or          NS-Omitting delegation TYPEs
61567    0xF07F   Standards Action

61568-   0xF080-  Expert Review or          NS-Preserving delegation TYPEs
61695    0xF0FF   Standards Action

61696-   0xF100-  Expert Review or          On-Demand delegation TYPEs
61935    0xF1EF   Standards Action

61936-   0xF1F0-  Private Use               Private delegation TYPEs
61951    0xF1FF

Speaking for the authors of both DELEG and DELEXT, we seek input from the WG on this design.

Roy
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