The Minimum Rank with Hysteresis Objective Function

Note: This ballot was opened for revision 09 and is now closed.

(Stewart Bryant) Yes

(Adrian Farrel) Yes

(Ron Bonica) No Objection

(Gonzalo Camarillo) No Objection

Benoit Claise No Objection

(Ralph Droms) (was Discuss) No Objection

Comment (2012-07-07)
Thank you for addressing my Discuss points in the most recent
rev of this document.  I've cleared my Discuss.

While these comments are non-blocking, they should be considered
carefully as they are based on implementation experience with this

1. The second component of the path cost in section 3.1:

   2.  The value of the selected metric in the metric container in the
       DIO sent by that neighbor.

is incompletely described.  While an implementor should realize from
section 3.5 that the rank advertised by the neighbor is an
approximation for ETX and should be used here, the text as written is

2. Also for completeness, the document should specify the
representation used for ETX to be used in path cost computation; e.g.,
as specified for the ETX sub-object in RFC 6551.

3. Related to point 2, explanation of the relationship between the
representation used for ETX and rank should be explained, especially
considering what I think will be unexpected side effects of the value
of DEFAULT_MIN_HOP_RANK_INCREASE defined to be 256 in RFC 6550
interacting with the (presumed) default representation of ETX as
defines in RFC 6551.

4.  In section 3.4:

   If ETX is the selected metric, a node SHOULD NOT advertise it in a
   metric container.

s/SHOULD NOT/MUST NOT/ (and this text is redundant relative to the
last sentence of section 3.5).

5. Are the parameter values in section 5 recommended only for use when
the selected metric is ETX; seems to me MAX_LINK_METRIC, MAX_PATH_COST
and PARENT_SWITCH_THRESHOLD depend on the selected metric and the
recommended values wouldn't make much sense for, e.g., hop count.

These comments are purely editorial and offered to improve the clarity
of the document.

1. The paragraph immediately following table seems superfluous.  The
list of metrics for which the rank is undefined is not complete (from
RFC 6551).  The paragraph begs the question "why would the deployment
choose a metric for which the rank is undefined?"

2. Readability would be improved by writing the details of the
special-case treatment of ETX (currently in section 3.5) to the point
at which that special-case treatment modifies other behavior specified
in the document; e.g., the second component of the path cost cited

3. The second sentence of section 6 is pretty opaque.  Is the point
that the "List of supported metrics" from section 18.2.3 need not be
supported if MRHOF is used?

4. Isn't the last paragraph of section 6.1 true for any selected metric?

(Wesley Eddy) No Objection

Comment (2012-05-09 for -10)
I support point 2 of Brian's DISCUSS.

Stephen Farrell No Objection

Comment (2012-05-09 for -10)
- Hysteresis could do with a definition - many non-native
English speakers (and native speakers!) might have to go
look it up so why not save them the trouble?

- ETX is used without expansion of reference in the intro.
Link color is used in 3.3 but not defined. It'd be good to
be clearer that those are defined in 6551.

- This smells experimental to me. I wondered if it had
already been implemented/tested. (Not a requirement
for PS, so I'm just asking.)

- You RECOMMEND use of security mechanisms if there is a
risk. Can't you be more specific on which security
mechanism you mean (e.g.  referring to the right bit of
6550, maybe 10.6)? I've not made this a discuss since I
hold one on the security framework and perhaps the
inability to pick something concrete here will be resolved
as a side-effect of that.

Brian Haberman (was Discuss) No Objection

(Russ Housley) No Objection

Comment (2012-05-06 for -10)
  Please consider the editorial issues raise in the Gen-ART Review by
  Miguel Garcia on 27-Mar-2012.  The review can be found here:

Barry Leiba No Objection

Comment (2012-04-29 for -10)
Substantive comments; please adopt or respond to these:

Nice, easy-to-read document.  Only one substantive comment, about 2119 language:

-- Section 3.2.1 --

The use of SHOULD and MAY here is inconsistent -- the MAY turns the SHOULD into something more optional than a SHOULD ought to be.  I suggest not using MAY, and rephrasing this way (unless I misunderstand the meaning here):
   If, despite the above, it is necessary to defer the parent selection
   until a later time, note that doing so can delay the use of better
   paths available in the network.

Editorial suggestions.  No need to respond to these; take them or modify them as you please:

-- Section 1 --
   Because MRHOF seeks to minimize path costs as described by metrics,
   it can only be used with additive metrics.  MRHOF ignores metrics
   that are not additive.

Is it really "ignores"?  Or "does not support"?

-- Section 2 --
         Path cost is obtained by summing up the selected metric of the
         links or nodes along the path.
         Path cost is obtained by summing up the values of the selected
         metric for the links or nodes along the path.

(Pete Resnick) No Objection

(Robert Sparks) No Objection

Comment (2012-05-07 for -10)
I made the same observations in my review that Barry reports in his comments. Please also consider clarifying that no one node sums up the values of the selected metrics in the definition of path cost - rather, each node adds to the cost reported by the parent (section 3.1) resulting in a total for the path.

Martin Stiemerling (was Discuss) No Objection

Comment (2012-07-03)
I have cleared and thank you for addressing my concerns.

(spt) No Objection