This registry lists identifiers for extensions to the MLS protocol. The extension type field is two bytes wide, so valid extension type values are in the range 0x0000 to 0xffff.
New extensions are supposed to be added to the EXISTING IANA registries.
The extensions draft IANA section begins:
This is contradictory to the clear language in the IANA considerations of the MLS protocol spec (example quoted from Section 17.2):
New extensions are supposed to be added to the EXISTING IANA registries.