draft-ietf-roll-of0-03.txt   draft-ietf-roll-of0-04.txt 
ROLL P. Thubert, Ed. ROLL P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Standards Track July 29, 2010 Intended status: Standards Track December 8, 2010
Expires: January 30, 2011 Expires: June 11, 2011
RPL Objective Function 0 RPL Objective Function 0
draft-ietf-roll-of0-03 draft-ietf-roll-of0-04
Abstract Abstract
The Routing Protocol for Low Power and Lossy Networks (RPL) defines a The Routing Protocol for Low Power and Lossy Networks (RPL) defines a
generic Distance Vector protocol for Low Power and Lossy Networks generic Distance Vector protocol for Low Power and Lossy Networks
(LLNs). RPL is instantiated to honor a particular routing objective/ (LLNs). RPL is instantiated to honor a particular routing objective/
constraint by the adding a specific Objective Function (OF) that is constraint by the adding a specific Objective Function (OF) that is
designed to solve that problem. This specification defines a basic designed to solve that problem. This specification defines a basic
OF, OF0, that uses only the abstract properties exposed in RPL OF, OF0, that uses only the abstract properties exposed in RPL
messages to maximize connectivity. messages to maximize connectivity.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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."
This Internet-Draft will expire on January 30, 2011. This Internet-Draft will expire on June 11, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 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. Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Selection of the Preferred Parent . . . . . . . . . . . . . . . 5 4. Selection of the Preferred Parent . . . . . . . . . . . . . . . 5
5. Selection of the Backup next_hop . . . . . . . . . . . . . . . 6 5. Selection of the Backup next_hop . . . . . . . . . . . . . . . 6
6. Abstract Interface with RPL core . . . . . . . . . . . . . . . 6 6. Abstract Interface with RPL core . . . . . . . . . . . . . . . 6
7. OF0 Constants and Variables . . . . . . . . . . . . . . . . . . 7 7. OF0 Constants and Variables . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . . 8 11.1. Normative References . . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . . 8 11.2. Informative References . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
The IETF ROLL Working Group has defined application-specific routing The IETF ROLL Working Group has defined application-specific routing
requirements for a Low Power and Lossy Network (LLN) routing requirements for a Low Power and Lossy Network (LLN) routing
protocol, specified in [I-D.ietf-roll-building-routing-reqs], protocol, specified in [I-D.ietf-roll-building-routing-reqs],
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connectivity to a specific set of nodes or to a larger routing connectivity to a specific set of nodes or to a larger routing
infrastructure. For the purpose of OF0, Grounded thus means that the infrastructure. For the purpose of OF0, Grounded thus means that the
root provides such connectivity. How that connectivity is asserted root provides such connectivity. How that connectivity is asserted
and maintained is out of scope. and maintained is out of scope.
Objective Function 0 is designed to find the nearest Grounded root. Objective Function 0 is designed to find the nearest Grounded root.
In the absence of a Grounded root, LLN inner connectivity is still In the absence of a Grounded root, LLN inner connectivity is still
desirable and floating DAGs will form, rooted at the nodes with the desirable and floating DAGs will form, rooted at the nodes with the
highest administrative preference. highest administrative preference.
The metric used in OF0 is the RPL Rank, as defined in The metric used in OF0 is an administratively defined scalar cost
[I-D.ietf-roll-rpl]. Using a metric that in essence is similar to that is trivially added up along a path to compute the RPL Rank, as
hop count implies that the quality of the connectivity should be defined in [I-D.ietf-roll-rpl]. As a result, the Rank if a node is
asserted so that only neighbors with a good enough connectivity are analogous to a weighted hop count of the path to the root. Using a
presented to the OF. How that connectivity is asserted and metric that in essence is similar to hop count implies that the
maintained is out of scope. quality of the connectivity should be asserted so that only neighbors
with a good enough connectivity are presented to the OF. How that
connectivity is asserted and maintained is out of scope.
Hop count used in wireless networks will tend to favor paths with Hop count used in wireless networks will tend to favor paths with
long distance links and non optimal connectivity properties. As a long distance links and non optimal connectivity properties. As a
result, the link selection must be very conservative, and the result, the link selection must be very conservative, and the
available link set is thus constrained. In some situations, this available link set is thus constrained. In some situations, this
might end up partitioning the network. For those reasons, the use of might end up partitioning the network. For those reasons, though it
hop count only is generally not recommended in wireless networks. can be used on wired links and wired link emulations such as WIFI
infrastructure mode, OF0 is generally not recommended for wireless
networks.
The default step of Rank is DEFAULT_RANK_INCREMENT for each hop. An The default step of Rank is DEFAULT_RANK_INCREMENT for each hop. An
implementation MAY allow a step between MINIMUM_RANK_INCREMENT and implementation MAY allow a step between MINIMUM_RANK_INCREMENT and
MAXIMUM_RANK_INCREMENT to reflect a large variation of link quality MAXIMUM_RANK_INCREMENT to reflect a large variation of link quality
by units of MINIMUM_RANK_INCREMENT. In other words, the least by units of MINIMUM_RANK_INCREMENT. In other words, the least
significant octet in the Rank is not used. significant octet in the Rank is not used.
It MAY stretch its step of Rank by up to MAXIMUM_RANK_STRETCH in It MAY stretch its step of Rank by up to MAXIMUM_RANK_STRETCH in
order to enable the selection of a sibling when only one parent is order to enable the selection of a sibling when only one parent is
available. For instance, say that a node computes a step of Rank of available. For instance, say that a node computes a step of Rank of
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Lossy Networks", draft-ietf-roll-building-routing-reqs-07 Lossy Networks", draft-ietf-roll-building-routing-reqs-07
(work in progress), September 2009. (work in progress), September 2009.
[I-D.ietf-roll-home-routing-reqs] [I-D.ietf-roll-home-routing-reqs]
Brandt, A., Buron, J., and G. Porcu, "Home Automation Brandt, A., Buron, J., and G. Porcu, "Home Automation
Routing Requirements in Low Power and Lossy Networks", Routing Requirements in Low Power and Lossy Networks",
draft-ietf-roll-home-routing-reqs-08 (work in progress), draft-ietf-roll-home-routing-reqs-08 (work in progress),
September 2009. September 2009.
[I-D.ietf-roll-routing-metrics] [I-D.ietf-roll-routing-metrics]
Vasseur, J., Kim, M., Networks, D., Dejean, N., and D. Vasseur, J., Kim, M., Pister, K., Dejean, N., and D.
Barthel, "Routing Metrics used for Path Calculation in Low Barthel, "Routing Metrics used for Path Calculation in Low
Power and Lossy Networks", Power and Lossy Networks",
draft-ietf-roll-routing-metrics-08 (work in progress), draft-ietf-roll-routing-metrics-13 (work in progress),
July 2010. December 2010.
[I-D.ietf-roll-rpl] [I-D.ietf-roll-rpl]
Winter, T., Thubert, P., and R. Team, "RPL: IPv6 Routing Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
Protocol for Low power and Lossy Networks", Kelsey, R., Levis, P., Pister, K., Struik, R., and J.
draft-ietf-roll-rpl-10 (work in progress), June 2010. Vasseur, "RPL: IPv6 Routing Protocol for Low power and
Lossy Networks", draft-ietf-roll-rpl-15 (work in
progress), November 2010.
[I-D.ietf-roll-terminology] [I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-03 (work in Networks", draft-ietf-roll-terminology-04 (work in
progress), March 2010. progress), September 2010.
[I-D.tsao-roll-security-framework] [I-D.tsao-roll-security-framework]
Tsao, T., Alexander, R., Daza, V., and A. Lozano, "A Tsao, T., Alexander, R., Daza, V., and A. Lozano, "A
Security Framework for Routing over Low Power and Lossy Security Framework for Routing over Low Power and Lossy
Networks", draft-tsao-roll-security-framework-02 (work in Networks", draft-tsao-roll-security-framework-02 (work in
progress), March 2010. progress), March 2010.
[RFC5548] Dohler, M., Watteyne, T., Winter, T., and D. Barthel, [RFC5548] Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
"Routing Requirements for Urban Low-Power and Lossy "Routing Requirements for Urban Low-Power and Lossy
Networks", RFC 5548, May 2009. Networks", RFC 5548, May 2009.
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