[netmod] mapping to snmp strings [Was: AD review of draft-ietf-netmod-system-mgmt]

[Martin Bjorklund <[e-mail]>]

Hi,

I am starting a new thread for this issue.  We need to resolve this
pretty soon.

We have a couple of YANG leafs that the current documents (interface
and system) specify that an implementation MAY map to corresponding
SMIv2 objects.  The YANG leafs allow XML 1.0 characters (unicode w/
exceptions), and have no hard length limits, whereas the SMIv2 objects
are DisplayStrings - nvt-ascii of size max 255.

The current documents say that if an implementation map the YANG leaf
to the SMIv2 object, it MUST restrict the YANG values to match the
SMIv2 restrictions.

One (theoretical?) problem that is not handled in the documents is
that some C0 control codes are valid in DisplayStrings but not valid
in a YANG string (e.g. BEL and VT).

The mappings are:

   /interfaces/interface/description - ifAlias
   /interfaces-state/interface/name  - ifName
   /system/contact                   - sysContact
   /system/location                  - sysLocation

Note that the interfaces document is in IETF Last Call.

Here are some options:

  1.  Do nothing; keep current text.

      NOTE: not clear how we handle DisplayString characters
      that are not legal YANG string characters.

  2.  Say that implementations MAY map, but that they need to do some
      vendor-specific translation procedure to handle the difference
      in character sets and lengths.

  3.  Like 2 + add an additional config false leaf in the YANG model
      to inform the YANG client about the resulting value.  (NOTE:
      this value is of course already available over SNMP).

  4.  Make the YANG leafs and SMIv2 objects separate, i.e., do not
      specify that there is a mapping between them.

Comments?

My preference is 4, followed by 2.


/martin