Non-existent result code in Section 6 of draft-ietf-ancp-mc-extensions-06.txt

Section 6 of draft-ietf-ancp-mc-extensions-06.txt refers to the 
following result code:

84 "TLV or value not supported by negotiated
    capability set"

This was not defined in the base document (RFC 6320). Something of the 
sort, but perhaps more general, should have been defined there, 
something like:

0x54 "Not supported by negotiated set of capabilities"

Should we write a separate draft updating RFC 6320 and adding this new 
value (setting a precedent for other general error codes), or just go 
ahead and define it in draft-ietf-ancp-mc-extensions? The amount of 
explanation goes beyond one paragraph, because handling of unsupported 
messages has to be described too.

Comments?

Tom Taylor