I have understood that Yoshiaiki Isobe contacted Harald Alvestrand
and Thomas Narten about this topic in December 2006; at that time,
Harald provided advice similar to the following.
RFC 4366 Section 5 defines the procedures for assigning a new TLS
extension type. TLS extension types are assigned to
Internet-Drafts that have been approved by the IESG.
So, you need to publish your extension as an Internet-Draft and
seek review of your draft. Once you have built a sufficient
consensus behind your draft, you can propose that your draft be
adopted by the TLS working group or published as an Area Director
(AD) sponsored submission. Sections 3.2 and 4 of RFC 4775 provide
more details on the procedures for an SDO working with the IETF to
extend an IETF protocol in this way. Note that because of the
requirements of RFC 4366, only the first option discussed in
Section 4 is available in this instance.
The TLS working group chairs and security ADs will be happy to
answer any process questions you may have as you attempt to build
consensus behind your draft.
TLS working group co-chair