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The Minimum Rank with Hysteresis Objective Function
draft-ietf-roll-minrank-hysteresis-of-11

Approval Announcement

Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: RFC Editor <rfc-editor@rfc-editor.org>,
    roll mailing list <roll@ietf.org>,
    roll chair <roll-chairs@tools.ietf.org>
Subject: Protocol Action: 'The Minimum Rank with Hysteresis Objective Function' to Proposed Standard (draft-ietf-roll-minrank-hysteresis-of-11.txt)

The IESG has approved the following document:
- 'The Minimum Rank with Hysteresis Objective Function'
  (draft-ietf-roll-minrank-hysteresis-of-11.txt) as Proposed Standard

This document is the product of the Routing Over Low power and Lossy
networks Working Group.

The IESG contact persons are Adrian Farrel and Stewart Bryant.

A URL of this Internet Draft is:
http://datatracker.ietf.org/doc/draft-ietf-roll-minrank-hysteresis-of/



Technical Summary

  An objective function specifies how RPL [RFC6550] selects paths.
  Objective functions can choose paths based on routing metrics or
  constraints. For example, if an RPL instance uses an objective
  function that minimizes hop-count, RPL will select paths with minimum
  hop count.

  The nodes running RPL might use a number of metrics to describe a
  link or a node [RFC6551] and make it available for route selection. 
  These metrics are advertised in RPL Destination Information Object
  (DIO) messages using a Metric Container suboption. An objective
  function can use these metrics to choose routes. The only exception
  is the ETX metric, which is used without the metric container as
  described in Section 3.5.

  To decouple the details of an individual metric or objective function
  from forwarding and routing, RPL describes routes through a value
  called Rank. Rank, roughly speaking, corresponds to the distance
  associated with a route. An objective function is responsible for
  computing a node's advertised Rank value based on the Rank of its
  potential parents, metrics, and other network properties.

  This specification describes MRHOF, an objective function for RPL.
  MRHOF uses hysteresis while selecting the path with the smallest
  metric value. The metric that MRHOF uses is determined by the
  metrics in the DIO Metric Container. For example, the use of MRHOF
  with the latency metric allows RPL to find stable minimum-latency
  paths from the nodes to a root in the DAG instance. The use of MRHOF
  with the ETX metric allows RPL to find the stable minimum-ETX paths
  from the nodes to a root in the DAG instance.

  MRHOF can only be used with an additive metric that must be minimized
  on the paths selected for routing.

Working Group Summary

  A relatively quiet WG process with no discontent. There were several late-
  breaking review comments that caused the document to be recycled
  after WG last call, but this was not contentious.

Document Quality

  There are several known implementations of this specification. 

Personnel

  JP Vasseur (jpv@cisco.com) is the Document Shepherd.
  Adrian Farrel (adrian@olddog.co.uk) is the Responsible AD