[mpls] Robert Wilton's Discuss on draft-ietf-mpls-lsp-ping-registries-update-08: (with DISCUSS)

[Robert Wilton via Datatracker <[e-mail]>]

Robert Wilton has entered the following ballot position for
draft-ietf-mpls-lsp-ping-registries-update-08: Discuss

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DISCUSS:
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Hi,

I have a couple of concerns regarding the change from part of the registry from
"Private Use" to "FCFS":

(1) Am I right in thinking that this could, at least in theory, break existing
deployments?  E.g., two separate implementations could both be using TLV value
31744 under "private use", whereas now they would both be expected to register
that TLV with IANA under FCFS, and obviously only one of them would be able to
get the registration?  Are the authors/WG/ADs aware with high confidence that
no such deployments exist?

(2) I find the "updates" tag for RFCs to be somewhat ambiguous as to what it
means.  Specifically, is someone who implements RFC 8611 obliged to also
implement draft-ietf-mpls-lsp-ping-registries-update when this becomes an RFC? 
Or are they allowed to take the previous interpretation of the "private use" in
the IANA registries?  Probably too late to change this now, but I wonder if it
would have been better to bis RFC 8611 instead so that RFC 8611 could have been
formally obsoleted by draft-ietf-mpls-lsp-ping-registries-update instead.

An alternative solution would be to keep the "Private Use" space as defined in
RFC 8611, and allocate new space for FCFS (24 entries) from the 15,000 entry
"RFC Required" section of the TLV Id space instead.  These would seem to make
the new allocation scheme in draft-ietf-mpls-lsp-ping-registries-update
entirely backwards compatible with any existing deployments.  Was this approach
considered and dismissed for some reason?

Regards,
Rob