[alto] Robert Wilton's Discuss on draft-ietf-alto-cost-mode-03: (with DISCUSS)

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

Robert Wilton has entered the following ballot position for
draft-ietf-alto-cost-mode-03: Discuss

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DISCUSS:
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Hi,

This is a "discuss" discuss, as in I'm not sure the document is wrong, but I
thought that it would be helpful to flag this for further discussion.

In RFC 7285, cost-mode is defined as a field that MUST take one of two string
values, either "numerical" or "ordinal".  I'm not really familiar with RFC
7285, and in particular, whether a receiver is required to explicitly check
that the received data must take one of these two values, or whether a
reasonable implementation could check for a single value, and if doesn't match
that value assume that it must be the other value (since there are only two
allowed values).  Obviously, moving to more than two values could then cause
this assumption to break in existing implementations.  Was this issue
considered and discussed by the WG?  It looks like alto does support a
versioning mechanism (i.e., by defining new media types) that might allow the
definition of this field to be upgraded in a safer way.  Was that approach
considered?

Regards,
Rob