draft-ietf-roll-minrank-hysteresis-of-02.txt   draft-ietf-roll-minrank-hysteresis-of-03.txt 
Networking Working Group O. Gnawali Networking Working Group O. Gnawali
Internet-Draft P. Levis Internet-Draft P. Levis
Intended status: Standards Track Stanford University Intended status: Standards Track Stanford University
Expires: October 29, 2011 April 27, 2011 Expires: November 4, 2011 May 03, 2011
The Minimum Rank Objective Function with Hysteresis The Minimum Rank Objective Function with Hysteresis
draft-ietf-roll-minrank-hysteresis-of-02 draft-ietf-roll-minrank-hysteresis-of-03
Abstract Abstract
The Routing Protocol for Low Power and Lossy Networks (RPL) uses The Routing Protocol for Low Power and Lossy Networks (RPL) uses
objective functions to construct routes that optimize or constrain objective functions to construct routes that optimize or constrain
the routes it selects and uses. This specification describes the the routes it selects and uses. This specification describes the
Minimum Rank Objective Function with Hysteresis (MRHOF), an objective Minimum Rank Objective Function with Hysteresis (MRHOF), an objective
function that selects routes that minimize a metric, while using function that selects routes that minimize a metric, while using
hysteresis to reduce churn in response to small metric changes. hysteresis to reduce churn in response to small metric changes.
MRHOF works with metrics that are additive along a route, and the MRHOF works with metrics that are additive along a route, and the
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 29, 2011. This Internet-Draft will expire on November 4, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The Minimum Rank Objective Function with Hysteresis . . . . . 4 3. The Minimum Rank Objective Function with Hysteresis . . . . . 4
3.1. Computing the Path cost . . . . . . . . . . . . . . . . . 4 3.1. Computing the Path cost . . . . . . . . . . . . . . . . . 4
3.2. Parent Selection . . . . . . . . . . . . . . . . . . . . . 5 3.2. Parent Selection . . . . . . . . . . . . . . . . . . . . . 5
3.3. Computing Rank . . . . . . . . . . . . . . . . . . . . . . 6 3.3. Computing Rank . . . . . . . . . . . . . . . . . . . . . . 6
3.4. Advertising the Path Cost . . . . . . . . . . . . . . . . 7 3.4. Advertising the Path Cost . . . . . . . . . . . . . . . . 7
3.5. Working Without Metric Containers . . . . . . . . . . . . 7 3.5. Working Without Metric Containers . . . . . . . . . . . . 7
4. Using MRHOF for Metric Maximization . . . . . . . . . . . . . 7 4. Using MRHOF for Metric Maximization . . . . . . . . . . . . . 7
5. Settings of RPL parameters . . . . . . . . . . . . . . . . . . 8 5. MRHOF Variables and Parameters . . . . . . . . . . . . . . . . 8
6. MRHOF Variables and Parameters . . . . . . . . . . . . . . . . 8 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
An objective function specifies how RPL [I-D.ietf-roll-rpl] selects An objective function specifies how RPL [I-D.ietf-roll-rpl] selects
paths. Objective functions can choose paths based on routing metrics paths. Objective functions can choose paths based on routing metrics
or constraints. For example, if an RPL instance uses an objective or constraints. For example, if an RPL instance uses an objective
function that minimizes hop-count, RPL will select paths with minimum function that minimizes hop-count, RPL will select paths with minimum
hop count. hop count.
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to the best path. This is the path cost for the DAG root. to the best path. This is the path cost for the DAG root.
Example, the best link reliability has a value of 1. Example, the best link reliability has a value of 1.
Metrics are all positive. Example, link reliability is always Metrics are all positive. Example, link reliability is always
positive. positive.
For metrics meeting the above conditions, the problem of maximizing For metrics meeting the above conditions, the problem of maximizing
the metric value is equivalent to minimizing the negative of the the metric value is equivalent to minimizing the negative of the
metric value. MRHOF is not required to work with these metrics. metric value. MRHOF is not required to work with these metrics.
5. Settings of RPL parameters 5. MRHOF Variables and Parameters
The MinHopRankIncrease parameter MUST be set to 1.
6. MRHOF Variables and Parameters
MRHOF uses the following variable: MRHOF uses the following variable:
cur_min_path_cost: The cost of the path from a node through its cur_min_path_cost: The cost of the path from a node through its
preferred parent to the root computed at the last parent preferred parent to the root computed at the last parent
selection. selection.
MRHOF uses the following parameters: MRHOF uses the following parameters:
MAX_LINK_METRIC: Maximum allowed value for the selected link MAX_LINK_METRIC: Maximum allowed value for the selected link
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MIN_PATH_COST: 0. At root, the expected transmission count is 0. MIN_PATH_COST: 0. At root, the expected transmission count is 0.
PARENT_SWITCH_THRESHOLD: 1.5. Switch to a new path only if it is PARENT_SWITCH_THRESHOLD: 1.5. Switch to a new path only if it is
expected to require at least 1.5 fewer transmission than the expected to require at least 1.5 fewer transmission than the
current path. current path.
PARENT_SET_SIZE: 3. If the preferred parent is not available, two PARENT_SET_SIZE: 3. If the preferred parent is not available, two
candidate parents are still available without triggering a new candidate parents are still available without triggering a new
round of route discovery. round of route discovery.
7. Acknowledgements 6. Acknowledgements
Thanks to Antonio Grilo, Nicolas Tsiftes, Matteo Paris, JP Vasseur, Thanks to Antonio Grilo, Nicolas Tsiftes, Matteo Paris, JP Vasseur,
and Phoebus Chen for their comments. and Phoebus Chen for their comments.
8. IANA Considerations 7. IANA Considerations
This specification requires an allocated OCP. A value of 1 is This specification requires an allocated OCP. A value of 1 is
requested. requested.
9. Security Considerations 8. Security Considerations
Security considerations to be developed in accordance to the output Security considerations to be developed in accordance to the output
of the WG. of the WG.
10. References 9. References
10.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References 9.2. Informative References
[I-D.ietf-roll-routing-metrics] [I-D.ietf-roll-routing-metrics]
Vasseur, J. and D. Networks, "Routing Metrics used for Vasseur, J. and D. Networks, "Routing Metrics used for
Path Calculation in Low Power and Lossy Networks", Path Calculation in Low Power and Lossy Networks",
draft-ietf-roll-routing-metrics-01 (work in progress), draft-ietf-roll-routing-metrics-01 (work in progress),
October 2009. October 2009.
[I-D.ietf-roll-rpl] [I-D.ietf-roll-rpl]
Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing
Protocol for Low power and Lossy Networks", Protocol for Low power and Lossy Networks",
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