Re: [Pce] Eric Rescorla's Discuss on draft-ietf-pce-pcep-exp-codepoints-04: (with DISCUSS)

["Adrian Farrel" <[e-mail]>]

Hi Eric,

> What happens when two deployments independently select the same
> experiment code point with different semantics? Is there some way to
> detect that, or do they just get confused? This seems like it it's fine in a
> closed environment, but unless I'm missing something, there's nothing
> in this text that actually requires that.

You might spend some time reading about experimental codepoints and the
experiments they are used for in BCP 82 (specifically RFC 3692).

There it says...

   Numbers in the experimentation range are similar to those called
   "Private Use" in RFC 2434 [IANA-CONSIDERATIONS].  They are not
   intended to be used in general deployments or be enabled by default
   in products or other general releases.  In those cases where a
   product or release makes use of an experimental number, the end user
   must be required to explicitly enable the experimental feature and
   likewise have the ability to chose [sic] and assign which number from the
   experimental range will be used for a specific purpose (i.e., so the
   end user can ensure that use of a particular number doesn't conflict
   with other on-going uses).  Shipping a product with a specific value
   pre-enabled would be inappropriate and can lead to interoperability
   problems when the chosen value collides with a different usage, as it
   someday surely will.

...and further...

   By definition, experimental numbers are not guaranteed to be
   unique in any environment other than one where the local system
   administrator has chosen to use a particular number for a particular
   purpose and can ensure that a particular value is not already in use
   for some other purpose.

This document makes clear reference to 3692 from the introduction suggesting
that readers look there for an explanation of Experimental codepoints.

The purpose of this document is to adjust the registries to allow
experimentation, not to redefine or refine the meaning of Experimental
codepoints.

We do draw out the security concern that we think 3692 glossed over, but this is
a reminder to protocol specs or implementers that they must watch out. This is
not a protocol spec and doesn't need to describe how implementations handle
conflicts.

Ciao,
Adrian