From: Lsr <lsr-boun...@ietf.org> on behalf of Tony Li <tony...@tony.li>
Sent: 17 March 2021 20:56

Les,

[Les:] The question here is whether there is a qualitative difference between 
two classes of bit fields.

That is indeed the key question. IMHO, there is not.

I don’t much care if a field is updated by a bis document or a related 
document. Regardless of the cause, as soon as there is more than one source of 
truth about the field, we are
creating ambiguity and confusion.

At the same time, I see no point in a registry with contents that never change. 
Thus, I will propose an alternative: by analogy to copy-on-write shared memory 
semantics, I propose that
we apply ‘registry-on-write’ semantics.

Specifics: When a potentially shared field is created, the defining document 
speciifies the name of a future registry, but does NOT request IANA create the 
registry at this time. When any document wishes
to update the field, it requests that IANA create it and populate it with both 
legacy and updated values.

Implementors that come along either document know where the source of truth is. 
 If the registry has not been created, then there is no ambiguity. If it has 
been, then there is no ambiguity.

Thoughts?

<tp>
I keep seeing YANG modules which reference the RFC that set up the IANA 
Registry which by then is of course out-of-date as the Normative definition is 
now in the IANA Registry.  I suspect that the authors fail to notice that this 
is now an IANA registry just reading the body of the RFC.  We do hide IANA 
Considerations out of site in Section 42 or some such tucked away at the end of 
the document.

The other issue is that if you want an example of abysmal choice of an 
identifier, then the IANA Registry names provide a wealth of examples, along 
with a comprehensive set of examples of how not to structure information in a 
hierarchy (assuming, that is, that you want others to be able to find the 
information).

LSR is not bad in this regard, compared to some routing WG, but it could do 
better.  Thus I see
Sub-sub-TLV
sub-sub-TLVs
Sub-TLVs
etc
For me everyone of these is not as helpful as it could be.  What matters?  TLV 
144, so that comes first; to me, it is a no-brainer but clearly my brain is 
different.

Tom Petch

Tony


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