Re: Benjamin Kaduk's Discuss on draft-ietf-bfd-yang-16: (with DISCUSS and COMMENT)

[Jeffrey Haas <[e-mail]>]

Benjamin,

On Wed, Jul 11, 2018 at 10:02:41AM -0500, Benjamin Kaduk wrote:
> "may be overkill in some circumstances" sounds exactly like an RFC 2119
> SHOULD, does it not?

Putting it slightly a different way, I am always wary of trying to embed too
much operational and security wisdom in documents for the following reasons:
- What's wise in one set of circumstances may not be in another.  By being
  proscriptive, you may lead to implementations that lack necessary
  flexibility.
- You're imposing a level of fate binding between mechanisms that may
  contravene desired behaviors from some operators that have split
  operational roles.

[...]
> To frame the same idea in a different fashion, we have this nice security
> considerations boilerplate for YANG modules, talking about how the usual
> access methods are NETCONF/RESTCONF, with MTI secure transport of ssh/TLS.
> The scheme being described here is effectively providing a new access
> mechanism (IGP) for a subset of the YANG module,

This is perhaps my personal disconnect.

Much of the point of providing a common configuration grouping for BFD for
client protocols was to encapsulate, "I'm a client of BFD, here's my
parameters".  An implementation is free to use the "please use bfd with
these parameters for my protocol" or perhaps ignore them.  But in
circumstances that an operator may wish to limit access to protocol BFD
behavior, it has the existing ability in NACM to enforce its policy on those
BFD nodes within the protocol tree.

What I feel you're saying is we need to call special attention to these
instantiations that may be imported by some module.  

What I'm confused about is why such an import is any more special than any
other import from another module.

-- Jeff