The IETF must have change control over the technology described in
any standards track IETF Documents in order to fix problems that may
be discovered or to produce other derivative works.
In some cases the developer of patented or otherwise controlled
technology may decide to hand over to the IETF the right to evolve
the technology (a.k.a., "change control"). The implementation of an
agreement between the IETF and the developer of the technology can be
complex. (See [RFC1790] and [RFC2339] for examples.)
Note that there is no inherent prohibition against a standards track
IETF Document making a normative reference to proprietary technology.
For example, a number of IETF Standards support proprietary
cryptographic transforms.
