Separate lookup equality from stored spelling
03Names that compare equal can arrive with different capitalization. Input case and output case are separate from the question of which records the lookup finds.
Separate first-case and latest-case storage examples display Lab.Example. or LAB.example. Either query capitalization retrieves both 192.0.2.10 and 192.0.2.11. No record is lost because its owner was spelled differently.
Source for this drawing: RFC 4343 · Read RFC section 4.2 ↗
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A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
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Changing the stored spelling must not split one case-equivalent name into separate record inventories.
- When an input creates a node, no case conversion is done. When a label for an existing node arrives in another case, implementations may keep the first case, let new input override it, or preserve separate copies.
- Two A records loaded under owner names differing only in case remain retrievable under either capitalization. These choices affect displayed case, not the number or completeness of the returned resource record set.
- Case MUST be preserved on output as described in §4, with the name-compression exception in §4.1. This is not a guarantee that a response always echoes query capitalization or always shows a particular administrator-preferred spelling.
The local merge example assumes the same Internet class and A address-record type and two fictional addresses. First-case and latest-case storage are separate permitted implementation examples, not required storage algorithms. Held erratum 6361 identifies clarity concerns about whose case is preserved; it supplies no normative replacement.
Read the RFC section ↗