# Advance RFC 7405 to Internet Standard, add to STD68 (ABNF)

## Summary

RFC 7405 was published in 2014 to fill a gap that RFC 5234 (2008,
STD68) left: support for publishing case-sensitive protocol encodings.

At the time ABNF was originally designed (~1977, see RFC 733),
lowercase support was still optional in many applications of
computers, and protocols therefore generally were designed to be
case-insensitive.

This has no longer been the case for several decades now, and new
standards have been designed with case-sensitive matching.

Before RFC 7405 became available, case-sensitive matching had to be
expressed in ABNF with %d or %x constructs, as for
example in RFC 4997 and RFC 4627:

    false        = %d102.97.108.115.101
    true         = %d116.114.117.101

    false = %x66.61.6c.73.65   ; false
    null  = %x6e.75.6c.6c      ; null
    true  = %x74.72.75.65      ; true

RFC 7405 finally updated RFC 5234 to support the syntax %s"false" for
case-sensitive matching, but this update has not yet been advanced to
Internet Standard.
Even this decade, specification writers still sometimes hesitate to
use RFC 7405 alongside RFC 5234; RFC 9535 still says:

    true                = %x74.72.75.65                ; true
    false               = %x66.61.6c.73.65             ; false
    null                = %x6e.75.6c.6c                ; null

## RFC6410 Criteria

   (1) There are at least two independent interoperating implementations
       with widespread deployment and successful operational experience.

According to datatracker, at the time of writing (2Q2026) there are
20 RFCs employing RFC 7405 as a normative reference:

https://datatracker.ietf.org/doc/rfc7405/referencedby/

Important protocols such as HTTP 1.1 (RFC 9112, STD99) and YANG (RFC 7950)
do employ the RFC 7405 extensions to STD68 alongside traditional ABNF.

As of this decade, support for RFC 7405 is now widely implemented in
ABNF tools.
There are no known interoperability problems or diverging
interpretations of RFC 7405.
There is no known controversy around the technical choices made by
RFC 7405.

   (2) There are no errata against the specification that would cause a
       new implementation to fail to interoperate with deployed ones.

(An "errata report", EID 5334, surfaced a few years after publishing RFC 7405
that suggested instead using single-quoted strings for case-sensitive
matching.

EID 5334 was rejected.

[5334]: https://www.rfc-editor.org/errata/rfc7405

   (3) There are no unused features in the specification that greatly
       increase implementation complexity.

RFC7405 is a four-page RFC. It does one thing and does it well.

   (4) If the technology required to implement the specification
       requires patented or otherwise controlled technology, then the
       set of implementations must demonstrate at least two independent,
       separate and successful uses of the licensing process.

Not Applicable