Keep internationalization and application identity separate
05Internationalized Domain Names in Applications (IDNA) connects permitted Unicode labels and their ASCII-compatible DNS representation. That application-level work differs from the DNS byte-comparison rule.
Separate local example: the application token KeyA differs from keya under its explicitly case-sensitive policy. Stop the proposal to fold this token using DNS rules. Name equality alone also does not grant access.
Source for this drawing: RFC 4343 · Read RFC section 5 ↗
New to this? Start hereA quick picture + helpful background
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.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
The official index records an IDNA definitions update. This guide separates current A-label/U-label equivalence from DNS ASCII folding and does not implement the historical Nameprep procedure.
Read the updated RFC section ↗ASCII DNS equality does not authorize general Unicode lowercasing, password changes or access decisions.
- RFC 4343’s original §5 cites the older IDNA2003 documents. The RFC Editor index records RFC 5890 as an update; use its IDNA2008 terminology and equivalence rules rather than teaching the older conversion procedure as current.
- RFC 5890 distinguishes Unicode U-labels from ASCII A-labels and defines their valid relationship. An xn-- prefix alone does not prove a valid A-label. This guide does not perform Punycode conversion, label validation or arbitrary Unicode matching.
- RFC 5890 §2.3.2.4 compares valid A-labels with normal DNS case-insensitive rules. It does not define equivalence by applying a general Unicode lowercase function to arbitrary raw label bytes.
- A domain name used as an application database key, file-system index or integrity input needs that context’s defined representation. A case-sensitive application token such as KeyA is a separate object; do not change its comparison rule merely because DNS names are case insensitive.
The IDNA stages are conceptual; validity is assumed, not computed by the page. Held technical erratum 7290 flags the dated §5 discussion and is not itself an accepted replacement algorithm. The final token and access gate are local application examples, not new RFC authorization requirements.
Read the RFC section ↗