draft-ietf-roll-routing-metrics-12.txt   draft-ietf-roll-routing-metrics-13.txt 
Networking Working Group JP. Vasseur, Ed. Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc Internet-Draft Cisco Systems, Inc
Intended status: Standards Track M. Kim, Ed. Intended status: Standards Track M. Kim, Ed.
Expires: May 12, 2011 Corporate Technology Group, KT Expires: June 5, 2011 Corporate Technology Group, KT
K. Pister K. Pister
Dust Networks Dust Networks
N. Dejean N. Dejean
Coronis SAS Coronis SAS
D. Barthel D. Barthel
France Telecom Orange France Telecom Orange
November 8, 2010 December 6, 2010
Routing Metrics used for Path Calculation in Low Power and Lossy Routing Metrics used for Path Calculation in Low Power and Lossy
Networks Networks
draft-ietf-roll-routing-metrics-12 draft-ietf-roll-routing-metrics-13
Abstract Abstract
Low power and Lossy Networks (LLNs) have unique characteristics Low power and Lossy Networks (LLNs) have unique characteristics
compared with traditional wired and ad-hoc networks that require the compared with traditional wired and ad-hoc networks that require the
specification of new routing metrics and constraints. By contrast specification of new routing metrics and constraints. By contrast
with typical Interior Gateway Protocol (IGP) routing metrics using with typical Interior Gateway Protocol (IGP) routing metrics using
hop counts or link metrics, this document specifies a set of link and hop counts or link metrics, this document specifies a set of link and
node routing metrics and constraints suitable to LLNs to be used by node routing metrics and constraints suitable to LLNs to be used by
the Routing for Low Power and lossy networks (RPL) routing protocol. the Routing for Low Power and lossy networks (RPL) routing protocol.
skipping to change at page 2, line 4 skipping to change at page 2, line 4
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This Internet-Draft will expire on May 12, 2011. This Internet-Draft will expire on June 5, 2011.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Object formats . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Object Formats . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1. DAG Metric Container format . . . . . . . . . . . . . . . 7 2.1. DAG Metric Container Format . . . . . . . . . . . . . . . 7
2.2. Use of multiple DAG Metric Containers . . . . . . . . . . 10 2.2. Use of Multiple DAG Metric Containers . . . . . . . . . . 10
2.3. Metric usage . . . . . . . . . . . . . . . . . . . . . . . 10 2.3. Metric Usage . . . . . . . . . . . . . . . . . . . . . . . 10
3. Node Metric/Constraint objects . . . . . . . . . . . . . . . . 11 3. Node Metric/Constraint Objects . . . . . . . . . . . . . . . . 11
3.1. Node State and Attributes object . . . . . . . . . . . . . 11 3.1. Node State and Attributes Object . . . . . . . . . . . . . 11
3.2. Node Energy object . . . . . . . . . . . . . . . . . . . . 12 3.2. Node Energy Object . . . . . . . . . . . . . . . . . . . . 13
3.3. Hop-Count object . . . . . . . . . . . . . . . . . . . . . 16 3.3. Hop-Count Object . . . . . . . . . . . . . . . . . . . . . 16
4. Link Metric/Constraint objects . . . . . . . . . . . . . . . . 16 4. Link Metric/Constraint Objects . . . . . . . . . . . . . . . . 17
4.1. Throughput . . . . . . . . . . . . . . . . . . . . . . . . 17 4.1. Throughput . . . . . . . . . . . . . . . . . . . . . . . . 17
4.2. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2. Latency . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3. Link reliability . . . . . . . . . . . . . . . . . . . . . 19 4.3. Link Reliability . . . . . . . . . . . . . . . . . . . . . 19
4.3.1. The Link Quality Level reliability metric . . . . . . 20 4.3.1. The Link Quality Level Reliability Metric . . . . . . 20
4.3.2. The Expected Transmission Count (ETX) reliability 4.3.2. The Expected Transmission Count (ETX) reliability
object . . . . . . . . . . . . . . . . . . . . . . . . 21 object . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4. Link Color object . . . . . . . . . . . . . . . . . . . . 23 4.4. Link Color Object . . . . . . . . . . . . . . . . . . . . 23
4.4.1. Link Color object description . . . . . . . . . . . . 23 4.4.1. Link Color Object Description . . . . . . . . . . . . 23
4.4.2. Mode of operation . . . . . . . . . . . . . . . . . . 24 4.4.2. Mode of operation . . . . . . . . . . . . . . . . . . 25
5. Computation of dynamic metrics and attributes . . . . . . . . 25 5. Computation of Dynamic Metrics and Attributes . . . . . . . . 25
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6.1. Routing Metric/Constraint type . . . . . . . . . . . . . . 26 6.1. Routing Metric/Constraint Type . . . . . . . . . . . . . . 26
6.2. Routing Metric/Constraint common header . . . . . . . . . 26 6.2. Routing Metric/Constraint TLV . . . . . . . . . . . . . . 26
6.3. NSA object . . . . . . . . . . . . . . . . . . . . . . . . 27 6.3. Routing Metric/Constraint Common Header . . . . . . . . . 26
6.4. Hop-Count object . . . . . . . . . . . . . . . . . . . . . 27 6.4. NSA Object . . . . . . . . . . . . . . . . . . . . . . . . 27
7. Security considerations . . . . . . . . . . . . . . . . . . . 28 6.5. Hop-Count Object . . . . . . . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
9.1. Normative references . . . . . . . . . . . . . . . . . . . 28 9.1. Normative references . . . . . . . . . . . . . . . . . . . 28
9.2. Informative references . . . . . . . . . . . . . . . . . . 28 9.2. Informative references . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
This document makes use of the terminology defined in This document makes use of the terminology defined in
[I-D.ietf-roll-terminology]. [I-D.ietf-roll-terminology].
Low power and Lossy Networks (LLNs) have specific routing Low power and Lossy Networks (LLNs) have specific routing
characteristics compared with traditional wired or ad-hoc networks characteristics compared with traditional wired or ad-hoc networks
that have been spelled out in [RFC5548], [RFC5673], [RFC5826] and that have been spelled out in [RFC5548], [RFC5673], [RFC5826] and
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Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) (see Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) (see
[RFC2702] and [RFC3209]) make use of other link attributes such as [RFC2702] and [RFC3209]) make use of other link attributes such as
the available reserved bandwidth (dynamic) or link affinities (most the available reserved bandwidth (dynamic) or link affinities (most
of the time static) to compute constrained shortest paths for Traffic of the time static) to compute constrained shortest paths for Traffic
Engineering Label Switched Paths (TE LSPs). Engineering Label Switched Paths (TE LSPs).
This document specifies routing metrics and constraints to be used in This document specifies routing metrics and constraints to be used in
path calculation by the Routing Protocol for Low Power and Lossy path calculation by the Routing Protocol for Low Power and Lossy
Networks (RPL) specified in [I-D.ietf-roll-rpl]. Networks (RPL) specified in [I-D.ietf-roll-rpl].
One of the prime objectives of this document is to propose a flexible One of the prime objectives of this document is to define a flexible
mechanism for the advertisement of routing metrics and constraints mechanism for the advertisement of routing metrics and constraints
used by RPL. Some RPL implementations may elect to adopt an used by RPL. Some RPL implementations may elect to adopt an
extremely simple approach based on the use of a single metric with no extremely simple approach based on the use of a single metric with no
constraint whereas other implementations may use a larger set of link constraint whereas other implementations may use a larger set of link
and node routing metrics and constraints. This specification and node routing metrics and constraints. This specification
provides a high degree of flexibility and a set of routing metrics provides a high degree of flexibility and a set of routing metrics
and constraints. New routing metrics and constraints could be and constraints. New routing metrics and constraints could be
defined in the future, as needed. defined in the future, as needed.
RPL is a distance vector routing protocol variant that builds RPL is a distance vector routing protocol variant that builds
Directed Acyclic Graphs (DAGs) based on routing metrics and Directed Acyclic Graphs (DAGs) based on routing metrics and
constraints. DAG formation rules are defined in [I-D.ietf-roll-rpl]: constraints. DAG formation rules are defined in [I-D.ietf-roll-rpl]:
o The DODAG root as defined in [I-D.ietf-roll-rpl] may advertise a o The Destination Oriented Directed Acyclic Graph (DODAG) root as
routing constraint used as a "filter" to prune links and nodes defined in [I-D.ietf-roll-rpl] may advertise a routing constraint
that do not satisfy specific properties. For example, it may be used as a "filter" to prune links and nodes that do not satisfy
required for the path to only traverse nodes that are mains specific properties. For example, it may be required for the path
powered or links that have at least a minimum reliability or a to only traverse nodes that are mains powered or links that have
specific "color" reflecting a user defined link characteristic at least a minimum reliability or a specific "color" reflecting a
(e.g the link layer supports encryption). user defined link characteristic (e.g the link layer supports
encryption).
o A routing metric is a quantitative value that is used to evaluate o A routing metric is a quantitative value that is used to evaluate
the path cost. Link and node metrics are usually (but not always) the path cost. Link and node metrics are usually (but not always)
additive. additive.
The best path is the path with the lowest cost with respect to some The best path is the path that satisfies all supplied constraints (if
metrics that satisfies all constraints (if any). It is also called any) and that has the lowest cost with respect to some specified
the shortest constrained path (in the presence of constraints). metrics. It is also called the shortest constrained path (in the
presence of constraints).
Routing metrics falls into the following sets of characteristics: Routing metrics may be categorized according to the following
characteristics:
o Link versus Node metrics o Link versus Node metrics
o Qualitative versus quantitative o Qualitative versus quantitative
o Dynamic versus static o Dynamic versus static
Routing requirements documents (see [RFC5673], [RFC5826] [RFC5548] Routing requirements documents (see [RFC5673], [RFC5826] [RFC5548]
and [RFC5867]) observe that it must be possible to take into account and [RFC5867]) observe that it must be possible to take into account
a variety of node constraints/metrics during path computation. a variety of node constraints/metrics during path computation.
Some link or node characteristics (e.g. link reliability flag, Some link or node characteristics (e.g. link reliability, remaining
remaining energy on the node) may either be used by RPL either as energy on the node) may be used by RPL either as routing constraints
routing constraints or metrics. For example, the path may be or as metrics. For example, the path may be computed to avoid links
computed to avoid links that do not provide a sufficient level of that do not provide a sufficient level of reliability (use as a
reliability (use as a constraint) or as the path offering most links constraint) or as the path offering most links with a specified
with a specified reliability level (use as a metric). This document reliability level (use as a metric). This document provides the
provides the flexibility to use link and node characterisics either flexibility to use link and node characterisics either as constraints
as constraints and/or metrics. and/or metrics.
The use of link and node routing metrics and constraints is not The use of link and node routing metrics and constraints is not
exclusive (e.g. it is for example possible to advertise a "hop count" exclusive (e.g. it is possible to advertise a "hop count" both as a
both as a metric to optimize the computed path and as a constraint metric to optimize the computed path and as a constraint (e.g. "Path
(e.g. "Path should not exceed n hops")). should not exceed n hops")).
Links in LLN commonly have rapidly changing node and link Links in LLN commonly have rapidly changing node and link
characteristics: thus routing metrics must be dynamic and techniques characteristics: thus routing metrics must be dynamic and techniques
must be used to smooth out the dynimicity of these metrics so as to must be used to smooth out the dynamicity of these metrics so as to
avoid routing oscillations. For instance, in addition to the dynamic avoid routing oscillations. For instance, in addition to the dynamic
nature of some links (e.g. wireless but also Powerline Communication nature of some links (e.g. wireless but also Powerline Communication
(PLC) links), nodes' resources such as residual energy are changing (PLC) links), nodes' resources such as residual energy are changing
continuously and may have to be taken into account during the path continuously and may have to be taken into account during the path
computation. computation.
It must be noted that the use of dynamic metrics is not new and has It must be noted that the use of dynamic metrics is not new and has
been experimented in ARPANET 2. The use of dynamic metrics is not been experimented in ARPANET 2 (see [[Khanna1989J]). The use of
trivial and great care must be given to the use of dynamic metrics dynamic metrics is not trivial and great care must be given to the
since it may lead to potential routing instabilities. That being use of dynamic metrics since it may lead to potential routing
said, lots of experience has been gained over the years on the use of instabilities. That being said, lots of experience has been gained
dynamic routing metrics, which have been deployed in a number of (non over the years on the use of dynamic routing metrics, which have been
IP) networks. deployed in a number of (non IP) networks.
Very careful attention must be given to the pace at which routing Very careful attention must be given to the pace at which routing
metrics and attributes values change in order to preserve routing metrics and attributes values change in order to preserve routing
stability. When using a dynamic routing metric, a RPL implementation stability. When using a dynamic routing metric, a RPL implementation
SHOULD make use of a multi-threshold scheme rather than fine granular should make use of a multi-threshold scheme rather than fine granular
metric updates reflecting each individual change to avoid spurious metric updates reflecting each individual change to avoid spurious
and unneccessary routing changes. and unneccessary routing changes.
The requirements on reporting frequency may differ among metrics, The requirements on reporting frequency may differ among metrics,
thus different reporting rates may be used for each metric. thus different reporting rates may be used for each metric.
The set of routing metrics and constraints used by an RPL deployment The set of routing metrics and constraints used by an RPL deployment
is signaled along the Directed Acyclic Graph (DAG) that is built is signaled along the DAG that is built according to the Objective
according to the Objective Function (rules governing how to build a Function (rules governing how to build a DAG) and the routing metrics
DAG) and the routing metrics and constraints are advertised in the and constraints are advertised in the DAG Information Option (DIO)
DAG Information Option (DIO) message specified in message specified in [I-D.ietf-roll-rpl]. RPL may be used to build
[I-D.ietf-roll-rpl]. RPL may be used to build DAGs with different DAGs with different characteristics. For example, it may be
characteristics. For example, it may be desirable to build a DAG desirable to build a DAG with the goal to maximize reliability by
with the goal to maximize reliability by using the link reliability using the link reliability metric to compute the "best" path.
metric to compute the "best" path. Another example might be to use Another example might be to use the energy node characteristic (e.g.
the energy node characteristic (e.g. mains powered versus battery mains powered versus battery operated) as a node constraint when
operated) as a node constraint when building the DAG so as to avoid building the DAG so as to avoid battery powered nodes in the DAG
battery powered nodes in the DAG while optimizing the link while optimizing the link throughput.
throughput.
The specification of objective functions used to compute the DAG The specification of objective functions used to compute the DAG
built by RPL is out of the scope of this document. This document built by RPL is out of the scope of this document. This document
defines routing metrics and constraints that are decoupled from the defines routing metrics and constraints that are decoupled from the
objective function. So a generic objective function could for objective function. So a generic objective function could for
example specify the rules to select the best parents in the DAG, the example specify the rules to select the best parents in the DAG, the
number of backup parents, etc and could be used with any routing number of backup parents, etc and could be used with any routing
metrics and/or constraints such as the ones specified in this metrics and/or constraints such as the ones specified in this
document. document.
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of parents, a node might decide according to the OF and local policy of parents, a node might decide according to the OF and local policy
which node to choose as a parent based on the maximum number of links which node to choose as a parent based on the maximum number of links
with a specific link reliability level, for example. with a specific link reliability level, for example.
Note that the routing metrics and constraints specified in this Note that the routing metrics and constraints specified in this
document are not specific to any particular link layer. An internal document are not specific to any particular link layer. An internal
API between the MAC layer and RPL may be used to accurately reflect API between the MAC layer and RPL may be used to accurately reflect
the metrics values of the link (wireless, wired, PLC). the metrics values of the link (wireless, wired, PLC).
Since a set of metrics and constraints will be used for links and Since a set of metrics and constraints will be used for links and
nodes in LLN, it is particularly critical to ensure the use of nodes in LLN, it is critical to ensure the use of consistent metric
consistent metric calculation mechanisms for all links and nodes in calculation mechanisms for all links and nodes in the network,
the network, similarly to the case of inter-domain IP routing. similarly to the case of inter-domain IP routing.
2. Object formats 2. Object Formats
2.1. DAG Metric Container format 2.1. DAG Metric Container Format
Routing metrics and constraints are carried within the DAG Metric Routing metrics and constraints are carried within the DAG Metric
Container object defined in [I-D.ietf-roll-rpl]. Should multiple Container object defined in [I-D.ietf-roll-rpl]. Should multiple
metrics and/or constraints be present in the DAG Metric Container, metrics and/or constraints be present in the DAG Metric Container,
their use to determine the "best" path can be defined by an Objective their use to determine the "best" path can be defined by an Objective
Function. Function.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
| Type=2 | Option Len |Routing Metric/Constraint objects | Type=2 | Option Len |Routing Metric/Constraint objects
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
Figure 1: DAG Metric Container format Figure 1: DAG Metric Container format
The Routing Metric/Constraint objects represent a metric or a The Routing Metric/Constraint objects represent a metric or a
constraint of a particular type. They may appear in any order in the constraint of a particular type. They may appear in any order in the
DAG Metric Container. They have a common format consisting of one or DAG Metric Container. They have a common format consisting of one or
more bytes with a common header: more bytes with a common header:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Routing-MC-Type| Flags |P|C|O|R| A | Prec | Length (bytes)| |Routing-MC-Type| Flags |P|C|O|R| A | Prec | Length (bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// (object body) // // (object body) //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Routing Metric/Constraint object generic format Figure 2: Routing Metric/Constraint object generic format
The object body carries one or more sub-objects defined later in this The object body carries one or more sub-objects defined later in this
document. document. Note that an object may carry TLV, which may itself
comprise other TLVs. A TLV carried within a TLV is called a TLV in
this specification.
Routing-MC-Type (Routing Metric/Constraint Type - 8 bits): the Routing-MC-Type (Routing Metric/Constraint Type - 8 bits): the
Routing Metric/Constraint Type field uniquely identifies each Routing Routing Metric/Constraint Type field uniquely identifies each Routing
Metric/Constraint object and is managed by IANA. Metric/Constraint object and is managed by IANA.
Length: this field defines the length of the object body, in bytes. Length: this field defines the length of the object body, in bytes.
The Flag field of the Routing Metric/Constraint object is managed by Flag field of the Routing Metric/Constraint object:
IANA. Unassigned bits are considered as reserved. They MUST be set
to zero on transmission and MUST be ignored on receipt. o P flag: the P field is only used for recorded metrics. When
cleared, all nodes along the path successfully recorded the
corresponding metric. When set, this indicates than one or
several nodes along the path could not record the metric of
interest (either because of lack of knowledge or because this was
prevented by policy).
o C Flag. When set, this indicates that the Routing Metric/ o C Flag. When set, this indicates that the Routing Metric/
Constraint object refers to a routing constraint. When cleared, Constraint object refers to a routing constraint. When cleared,
the routing object refers to a routing metric. the routing object refers to a routing metric.
o O Flag: The O flag is used exclusively for routing constraints (C o O Flag: The O flag is used exclusively for routing constraints (C
flag is set). When set, this indicates that the constraint flag is set). When set, this indicates that the constraint
specified in the body of the object is optional. When cleared, specified in the body of the object is optional. When cleared,
the constraint is mandatory. If the C flag is zero, the O flag the constraint is mandatory. If the C flag is zero, the O flag
MUST be set to zero on transmission and ignored on reception. MUST be set to zero on transmission and ignored on reception.
o R Flag: The R Flag is only relevant for routing metric (C=0) and o R Flag: The R Flag is only relevant for routing metric (C=0) and
MUST be cleared for C=1. When set, this indicates that the MUST be cleared for C=1. When set, this indicates that the
routing metric is recorded along the path. Conversely, when routing metric is recorded along the path. Conversely, when
cleared, the routing metric is aggregated. cleared, the routing metric is aggregated.
o A Field: The A field is only relevant for metrics and is used to The Flag field of the Routing Metric/Constraint object is managed by
indicate whether the aggregated routing metric is additive, IANA. Unassigned bits are considered as reserved. They MUST be set
multiplicative, reports a maximum or a minimum. to zero on transmission and MUST be ignored on receipt.
* A=0x00: The routing metric is additive A Field: The A field is only relevant for metrics and is used to
indicate whether the aggregated routing metric is additive,
multiplicative, reports a maximum or a minimum.
* A=0x01: The routing metric reports a maximum o A=0x00: The routing metric is additive
* A=0x02: The routing metric reports a minimum
* A=0x03: The routing metric is multiplicative o A=0x01: The routing metric reports a maximum
The A field has no meaning when the C Flag is set (i.e. when the o A=0x02: The routing metric reports a minimum
Routing Metric/Constraint object refers to a routing constraint)
and MUST be written to 0x00.
o Prec field: The Prec field indicates the precedence of this o A=0x03: The routing metric is multiplicative
Routing Metric/Constraint object relative to other objects in the
container. This is useful when a DAG Metric Container contains
several Routing Metric objects. The value 0 means the highest
precedence.
o P field: the P field is only used for recorded metrics. When The A field has no meaning when the C Flag is set (i.e. when the
cleared, all nodes along the path successfully recorded the Routing Metric/Constraint object refers to a routing constraint) and
corresponding metric. When set, this indicates than one or he only valid when the R bit is cleared. Otherwise, the A field MUST
several nodes along the path could not record the metric of be set to 0x00 and MUST be ignored on receipt.
interest (either because of lack of knowledge or because this was
prevented by policy). Prec field: The Prec field indicates the precedence of this Routing
Metric/Constraint object relative to other objects in the container.
This is useful when a DAG Metric Container contains several Routing
Metric objects. The value 0 means the highest precedence.
Example 1: A DAG formed by RPL where all nodes must be mains-powered Example 1: A DAG formed by RPL where all nodes must be mains-powered
and the best path is the one with lower aggregated ETX. In this case and the best path is the one with lower aggregated ETX. In this case
the DAG Metric container carries two Routing Metric/Constraint the DAG Metric container carries two Routing Metric/Constraint
objects: one is an ETX metric object with header (C=0, O=0, A=00, objects: one is an ETX metric object with header (C=0, O=0, A=00,
R=0) and the second one is a Node Energy constraint object with R=0) and the second one is a Node Energy constraint object with
header (C=1, O=0, A=00, R=0). Note that a RPL instance may use the header (C=1, O=0, A=00, R=0). Note that a RPL instance may use the
metric object to report a maximum (A=0x01) or a minimum (A=0x02). metric object to report a maximum (A=0x01) or a minimum (A=0x02).
If, for example, the best path is characterized by the path avoiding If, for example, the best path is characterized by the path avoiding
low quality links, then the path metric reports a maximum (A=0x01) low quality links, then the path metric reports a maximum (A=0x01)
skipping to change at page 10, line 13 skipping to change at page 10, line 17
Metric/Constraint TLV has the same structure: Metric/Constraint TLV has the same structure:
Type: 1 byte Type: 1 byte
Length: 1 byte Length: 1 byte
Value: variable Value: variable
A Routing Metric/Constraint TLV is comprised of 1 byte for the type, A Routing Metric/Constraint TLV is comprised of 1 byte for the type,
1 byte specifying the TLV length, and a value field. The TLV length 1 byte specifying the TLV length, and a value field. The TLV length
field defines the length of the value field in bytes. field defines the length of the value field in bytes.
Unrecognized TLVs MUST be ignored. Unrecognized TLVs MUST be silently ignored while still being
propagated in DIO generated by receiving node.
IANA manages the codepoints for all TLV carried in routing
constraint/metric objects.
IANA management of the Routing Metric/Constraint objects identifier IANA management of the Routing Metric/Constraint objects identifier
codespace is described in Section 6. codespace is described in Section 6.
2.2. Use of multiple DAG Metric Containers 2.2. Use of Multiple DAG Metric Containers
Since the length of RPL options is encoded using 1 octet, they cannot Since the length of RPL options is encoded using 1 octet, they cannot
exceed 255 bytes, which also applies to the DAG Metric Container. In exceed 255 bytes, which also applies to the DAG Metric Container. In
the vast majority of cases, the advertised routing metrics and the vast majority of cases, the advertised routing metrics and
constraints will not require that much space. However, there might constraints will not require that much space. However, there might
be circumstances where larger space is required, should for example a be circumstances where larger space is required, should for example a
set of routing metrics be recorded along a long path. In this case, set of routing metrics be recorded along a long path. In this case,
as specified in [I-D.ietf-roll-rpl], routing metrics will be carried in order to avoid overflow, as specified in [I-D.ietf-roll-rpl],
using multiple DAG Metric Containers objects. routing metrics will be carried using multiple DAG Metric Containers
objects.
In the rest of this document, this use of multiple DAG Metric In the rest of this document, this use of multiple DAG Metric
Containers objects will be considered as if they were actually just Containers objects will be considered as if they were actually just
one long DAG Metric Container object. one long DAG Metric Container object.
2.3. Metric usage 2.3. Metric Usage
When the DAG Metric Container contains a single aggregated metric When the DAG Metric Container contains a single aggregated metric
(scalar value), the order relation to select the best path is (scalar value), the order relation to select the best path is
implicitly derived from the metric type. For example, lower is implicitly derived from the metric type. For example, lower is
better for Hop Count, Link Latency and ETX. Conversely, for Node better for Hop Count, Link Latency and ETX. Conversely, for Node
Energy or Throughput, higher is better. Energy or Throughput, higher is better.
An example of using such a single aggregated metric is optimizing An example of using such a single aggregated metric is optimizing
routing for node energy. The Node Energy metric (E-E field) defined routing for node energy. The Node Energy metric (E-E field) defined
in Section 3.2 is aggregated along paths with an explicit min in Section 3.2 is aggregated along paths with an explicit min
skipping to change at page 11, line 12 skipping to change at page 11, line 21
An example of such use of multiple aggregated metrics is the An example of such use of multiple aggregated metrics is the
following: Hop-Count as the primary criterion, LQL as the secondary following: Hop-Count as the primary criterion, LQL as the secondary
criterion and Node Energy as the ultimate tie-breaker. In such a criterion and Node Energy as the ultimate tie-breaker. In such a
case, the Hop-Count, LQL and Node Energy metric objects' Prec fields case, the Hop-Count, LQL and Node Energy metric objects' Prec fields
should bear strictly increasing values such as 0, 1 and 2, should bear strictly increasing values such as 0, 1 and 2,
respectively. respectively.
If several aggregated metrics happen to bear the same Prec value, the If several aggregated metrics happen to bear the same Prec value, the
behavior is implementation-dependant. behavior is implementation-dependant.
3. Node Metric/Constraint objects 3. Node Metric/Constraint Objects
3.1. Node State and Attributes object The sections 3. and 4. specify several link and node metric/
constraint objects. In some cases it is stated that there must not
be more than one object of a specific type. In that case, if an RPL
implementation receives more than one objet of that type, the second
objet MUST silently be ignored.
3.1. Node State and Attributes Object
The Node State and Attribute (NSA) object is used to provide The Node State and Attribute (NSA) object is used to provide
information on node's characteristics. information on node characteristics.
The NSA object MAY be present in the DAG Metric Container. There The NSA object MAY be present in the DAG Metric Container. There
MUST be no more than one NSA object as a constraint per DAG Metric MUST NOT be more than one NSA object as a constraint per DAG Metric
Container, and no more than one NSA object as a metric per DAG Metric Container, and there MUST NOT be more than one NSA object as a metric
Container. per DAG Metric Container.
The NSA object may also contain a set of TLVs used to convey various The NSA object may also contain a set of TLVs used to convey various
node characteristics. No TLV is currently defined. node characteristics. No TLV is currently defined.
The NSA Routing Metric/Constraint Type is to be assigned by IANA The NSA Routing Metric/Constraint Type is to be assigned by IANA
(recommended value=1). (recommended value=1).
The format of the NSA object body is as follows: The format of the NSA object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| Res | Flags |A|O| Optional TLVs | Res | Flags |A|O| Optional TLVs
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 3: NSA object format Figure 3: NSA object body format
'O' flag: node workload may be hard to determine and express in some
scalar form. However, node workload could be a useful metric to
consider during path calculation, in particular when queuing delays
must be minimized for highly sensitive traffic considering Medium
Access Control (MAC) layer delay. Node workload MAY be set upon CPU
overload, lack of memory or any other node related conditions. Using
a simple 1-bit flag to characterize the node workload provides a
sufficient level of granularity, similarly to the "overload" bit used
in routing protocols such as IS-IS. Algorithms used to set the
overload bit and to compute paths to potentially avoid nodes with
their overload bit set are outside the scope of this document, but it
is RECOMMENDED to avoid frequent changes of this bit to avoid routing
oscillations.
'A' flag: data Aggregation Attribute: data fusion involves more Res flags (8 bits): Reserved field. This field MUST be set to zero
complicated processing to improve the accuracy of the output data, on transmission and MUST be ignored on receipt.
while data aggregation mostly aims at reducing the amount of data.
This is listed as a requirement in Section 6.2 of [RFC5548]. Some
applications may make use of the aggregation node attribute in their
routing decision so as to minimize the amount of traffic on the
network, thus potentially increasing its lifetime in battery operated
environments. Applications where highly directional data flow is
expected on a regular basis may take advantage of data aggregation
supported routing.
The following two bits of the NSA object are currently defined: The following two bits of the NSA object are currently defined:
o A Flag: When set, this indicates that the node can act as a o A Flag: data Aggregation Attribute. Data fusion involves more
traffic aggregator. An implementation MAY decide to add optional complicated processing to improve the accuracy of the output data,
TLVs (not currently defined) to further describe the node traffic while data aggregation mostly aims at reducing the amount of data.
aggregator functionality. This is listed as a requirement in Section 6.2 of [RFC5548]. Some
applications may make use of the aggregation node attribute in
their routing decision so as to minimize the amount of traffic on
the network, thus potentially increasing its lifetime in battery
operated environments. Applications where highly directional data
flow is expected on a regular basis may take advantage of data
aggregation supported routing. When set, this indicates that the
node can act as a traffic aggregator. An implementation MAY
decide to add optional TLVs (not currently defined) to further
describe the node traffic aggregator functionality.
o O Flag: When set, this indicates that the node is overloaded and o O Flag: node workload may be hard to determine and express in some
may not be able to process traffic. scalar form. However, node workload could be a useful metric to
consider during path calculation, in particular when queuing
delays must be minimized for highly sensitive traffic considering
Medium Access Control (MAC) layer delay. Node workload MAY be set
upon CPU overload, lack of memory or any other node related
conditions. Using a simple 1-bit flag to characterize the node
workload provides a sufficient level of granularity, similarly to
the "overload" bit used in routing protocols such as IS-IS.
Algorithms used to set the overload bit and to compute paths to
potentially avoid nodes with their overload bit set are outside
the scope of this document, but it is RECOMMENDED to avoid
frequent changes of this bit to avoid routing oscillations. When
set, this indicates that the node is overloaded and may not be
able to process traffic.
They MUST be set to zero on transmission and MUST be ignored on
receipt.
The Flag field of the NSA Routing Metric/Constraint object is managed The Flag field of the NSA Routing Metric/Constraint object is managed
by IANA. Unassigned bits are considered as reserved. They MUST be by IANA. Unassigned bits are considered as reserved.
set to zero on transmission and MUST be ignored on receipt.
3.2. Node Energy object 3.2. Node Energy Object
Whenever possible, a node with low residual energy should not be It may sometimes be desirable to avoid selecting a node with low
selected as a router, thus the support for constraint-based routing residual energy as a router, thus the support for constraint-based
is needed. In such cases, the routing protocol engine may compute a routing is needed. In such cases, the routing protocol engine may
longer path (constraint based) for some traffic in order to increase compute a longer path (constraint based) for some traffic in order to
the network life duration. increase the network life duration.
Power and energy are clearly critical resources in most LLNs. As yet Power and energy are clearly critical resources in most LLNs. As yet
there is no simple abstraction which adequately covers the broad there is no simple abstraction which adequately covers the broad
range of power sources and energy storage devices used in existing range of power sources and energy storage devices used in existing
LLN nodes. These include mains-powered, primary batteries, energy LLN nodes. These include mains-powered, primary batteries, energy
scavengers, and a variety of secondary storage mechanisms. scavengers, and a variety of secondary storage mechanisms.
Scavengers may provide a reliable low level of power, such as might Scavengers may provide a reliable low level of power, such as might
be available from a 4-20mA loop; a reliable but periodic stream of be available from a 4-20mA loop; a reliable but periodic stream of
power, such as provided by a well-positioned solar cell; or power, such as provided by a well-positioned solar cell; or
unpredictable power, such as might be provided by a vibrational unpredictable power, such as might be provided by a vibrational
skipping to change at page 13, line 28 skipping to change at page 13, line 52
milliseconds, seconds, and hours/years. milliseconds, seconds, and hours/years.
Raw power and energy values are meaningless without knowledge of the Raw power and energy values are meaningless without knowledge of the
energy cost of sending and receiving packets, and lifetime estimates energy cost of sending and receiving packets, and lifetime estimates
have no value without some higher-level constraint on the lifetime have no value without some higher-level constraint on the lifetime
required of a device. In some cases the path that exhausts the required of a device. In some cases the path that exhausts the
battery of a node on the bed table in a month may be preferable to a battery of a node on the bed table in a month may be preferable to a
route that reduces the lifetime of a node in the wall to a decade. route that reduces the lifetime of a node in the wall to a decade.
Given the complexity of trying to address such a broad collection of Given the complexity of trying to address such a broad collection of
constraints, this document defines three levels of fidelity in the constraints, this document defines two levels of fidelity in the
solution. solution.
The simplest solution relies on a 2-bit field encoding three types of The simplest solution relies on a 2-bit field encoding three types of
power sources: "powered", "battery", "scavenger". This simple power sources: "powered", "battery", "scavenger". This simple
approach may be sufficient for many applications. approach may be sufficient for many applications.
The mid-complexity solution is a single parameter that can be used to The mid-complexity solution is a single parameter that can be used to
encode the energetic happiness of both battery powered and scavenging encode the energetic happiness of both battery powered and scavenging
nodes. For scavenging nodes, the 8 bit quantity is the power nodes. For scavenging nodes, the 8 bit quantity is the power
provided by the scavenger divided by the power consumed by the provided by the scavenger divided by the power consumed by the
application, H=P_in/P_out, in units of percent. Nodes which are application, E-E=P_in/P_out, in units of percent. Nodes which are
scavenging more power than they are consuming will register above scavenging more power than they are consuming will register above
100. A good time period for averaging power in this calculation may 100. A good time period for averaging power in this calculation may
be related to the discharge time of the energy storage device on the be related to the discharge time of the energy storage device on the
node, but specifying this is out of the scope of this document. For node, but specifying this is out of the scope of this document. For
battery powered devices, H is the current expected lifetime divided battery powered devices, E-E is the current expected lifetime divided
by the desired minimum lifetime. The estimation of remaining battery by the desired minimum lifetime, in units of percent. The estimation
energy and actual power consumption can be difficult, and the of remaining battery energy and actual power consumption can be
specifics of this calculation are out of scope of this document, but difficult, and the specifics of this calculation are out of scope of
two examples are presented. If the node can measure its average this document, but two examples are presented. If the node can
power consumption, then H can be calculated as the ratio of desired measure its average power consumption, then H can be calculated as
max power (initial energy E_0 divided by desired lifetime T) to the ratio of desired max power (initial energy E_0 divided by desired
actual power, H=P_max/P_now. Alternatively, if the energy in the lifetime T) to actual power, E-E=P_max/P_now. Alternatively, if the
battery E_bat can be estimated, and the total elapsed lifetime, t, is energy in the battery E_bat can be estimated, and the total elapsed
available, then H can be calculated as the total stored energy lifetime, t, is available, then H can be calculated as the total
remaining versus the target energy remaining: H= E_bat / [E_0 stored energy remaining versus the target energy remaining: E-E=
(T-t)/T]. E_bat / [E_0 (T-t)/T].
An example of optimized route is max(min(H)) for all battery operated An example of optimized route is max(min(H)) for all battery operated
nodes along the route, subject to the constraint that H>=100 for all nodes along the route, subject to the constraint that E-E>=100 for
scavengers along the route. all scavengers along the route.
Note that the estimated percentage of remaining energy indicated in Note that the estimated percentage of remaining energy indicated in
the E-E field may not be useful in the presence of nodes powered by the E-E field may not be useful in the presence of nodes powered by
battery or energy scavengers when the amount of energy accumulated by battery or energy scavengers when the amount of energy accumulated by
the device significantly differ. Indeed, X% of remaining energy on a the device significantly differ. Indeed, X% of remaining energy on a
node that can store a large amount of energy cannot be easily node that can store a large amount of energy cannot be easily
compared to the same percentage of remaining energy on a node powered compared to the same percentage of remaining energy on a node powered
by a tiny source of energy. That being said, in networks where nodes by a tiny source of energy. That being said, in networks where nodes
have relatively close energy storage, such a percentage of remaining have relatively close energy storage, such a percentage of remaining
energy is useful. energy is useful.
The Node Energy (NE) object is used to provide information related to The Node Energy (NE) object is used to provide information related to
node energy and may be used as a metric or as constraint. node energy and may be used as a metric or as constraint.
The NE object MAY be present in the DAG Metric Container. There MUST The NE object MAY be present in the DAG Metric Container. There MUST
be no more than one NE object as a constraint per DAG Metric NOT be more than one NE object as a constraint per DAG Metric
Container, and no more than one NE object as a metric per DAG Metric Container, and there MUST NOT be more than one NE object as a metric
Container. per DAG Metric Container.
The NE object Type is to be assigned by IANA (recommended value=2). The NE object Type is to be assigned by IANA (recommended value=2).
The format of the NE object body is as follows: The format of the NE object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| NE Sub-objects | NE Sub-objects
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 4: NE object format Figure 4: NE sub-object format
The format of the NE sub-object body is as follows: The format of the NE sub-object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| Flags |I| T |E| E-E | Optional TLVs | Flags |I| T |E| E-E | Optional TLVs
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 5: NE sub-object format Figure 5: NE sub-object format
The NE sub-object may also contain a set of TLVs used to convey The NE sub-object may also contain a set of TLVs used to convey
various nodes' characteristics. various nodes' characteristics.
skipping to change at page 15, line 29 skipping to change at page 15, line 42
o I (Included): the I bit is only relevant when the node type is o I (Included): the I bit is only relevant when the node type is
used as a constraint. For example, the path must only traverse used as a constraint. For example, the path must only traverse
mains-powered nodes. Conversely, battery operated nodes must be mains-powered nodes. Conversely, battery operated nodes must be
excluded. The I bit is used to stipulate inclusion versus excluded. The I bit is used to stipulate inclusion versus
exclusion. When set, this indicates that nodes of the type exclusion. When set, this indicates that nodes of the type
specified in the node type field MUST be included. Conversely, specified in the node type field MUST be included. Conversely,
when cleared, this indicates that nodes of type specified in the when cleared, this indicates that nodes of type specified in the
node type field MUST be excluded. node type field MUST be excluded.
o T (node Type): 2-bit field indicating the node type. E=0x00 o T (node Type): 2-bit field indicating the node type. T=0x00
designates a mains-powered node, E=0x01 a battery-powered node and designates a mains-powered node, T=0x01 a battery-powered node and
E=0x02 a node powered by an energy scavenger. T=0x02 a node powered by an energy scavenger.
o E (Estimation): when the E bit is set for a metric, the estimated o E (Estimation): when the E bit is set for a metric, the estimated
percentage of remaining energy on the node is indicated in the E-E percentage of remaining energy on the node is indicated in the E-E
8-bit field. When cleared, the estimated percentage of remaining 8-bit field. When cleared, the estimated percentage of remaining
energy is not provided. When the E bit is set for a constraint, energy is not provided. When the E bit is set for a constraint,
the E-E field defines a threshold for the inclusion/exclusion: if the E-E field defines a threshold for the inclusion/exclusion: if
an inclusion, nodes with values higher than the threshold are to an inclusion, nodes with values higher than the threshold are to
be included; if an exclusion, nodes with values lower than the be included; if an exclusion, nodes with values lower than the
threshold are to be excluded. threshold are to be excluded.
E-E (Estimated-Energy): 8-bit unsigned integer field indicating an E-E (Estimated-Energy): 8-bit unsigned integer field indicating an
estimated percentage of remaining energy. The E-E field is only estimated percentage of remaining energy. The E-E field is only
relevant when the E flag is set, and MUST be set to 0 when the E flag relevant when the E flag is set, and MUST be set to 0 when the E flag
is cleared. is cleared.
If the NE object comprises several sub-objects when used as a If the NE object comprises several sub-objects when used as a
constraint, each sub-object adds or subtracts node subsets as the constraint, each sub-object adds or subtracts node subsets as the
sub-objects are parsed in order. The initial set (full or empty) is sub-objects are parsed in order. The initial set (full or empty) is
defined by the I bit of the first sub-object: full if that I bit is defined by the I bit of the first sub-object: full if that I bit is
an exclusion, empty is that I bit is an inclusion. an exclusion, empty if that I bit is an inclusion.
No TLV is currently defined. No TLV is currently defined.
Future addenda to this document may include more complex solutions Future documents may define more complex solutions involving TLV
involving a half dozen TLV parameters representing energy storage, parameters representing energy storage, consumption, and generation
consumption, and generation capabilities of the node, as well as capabilities of the node, as well as desired lifetime.
desired lifetime.
3.3. Hop-Count object 3.3. Hop-Count Object
The HoP-Count (HP) object is used to report the number of traversed The HoP-Count (HP) object is used to report the number of traversed
nodes along the path. nodes along the path.
The HP object MAY be present in the DAG Metric Container. There MUST The HP object MAY be present in the DAG Metric Container. There MUST
be no more than one HP object as a constraint per DAG Metric NOT be more than one HP object as a constraint per DAG Metric
Container, and no more than one HP object as a metric per DAG Metric Container, and there MUST NOT be more than one HP object as a metric
Container. per DAG Metric Container.
The HP object may also contain a set of TLVs used to convey various The HP object may also contain a set of TLVs used to convey various
node characteristics. No TLV is currently defined. node characteristics. No TLV is currently defined.
The HP routing metric object Type is to be assigned by IANA The HP routing metric object Type is to be assigned by IANA
(recommended value=3) (recommended value=3)
The format of the Hop Count object body is as follows: The format of the Hop Count object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| Res | Flags | Hop Count | Optional TLVs | Res | Flags | Hop Count | Optional TLVs
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 6: Hop Count object format Figure 6: Hop Count object body format
No Flag is currently defined. Res flags (4 bits): Reserved field. This field MUST be set to zero
on transmission and MUST be ignored on receipt.
No Flag is currently defined. Unassigned bits are considered as
reserved. They MUST be set to zero on transmission and MUST be
ignored on receipt.
The HP object may be used as a constraint or a metric. When used as The HP object may be used as a constraint or a metric. When used as
a constraint, the DAG root indicates the maximum number of hops that a constraint, the DAG root indicates the maximum number of hops that
a path may traverse. When that number is reached, no other node can a path may traverse. When that number is reached, no other node can
join that path. When used as a metric, each visited node simply join that path. When used as a metric, each visited node simply
increments the Hop Count field. increments the Hop Count field.
4. Link Metric/Constraint objects Note that the first node along a path inserting a Hop-count object
MUST set the Hop Count field value to 1.
4. Link Metric/Constraint Objects
4.1. Throughput 4.1. Throughput
Many LLNs support a wide range of throughputs. For some links, this Many LLNs support a wide range of throughputs. For some links, this
may be due to variable coding. For the deeply duty-cycled links may be due to variable coding. For the deeply duty-cycled links
found in many LLNs, the variability comes as a result of trading found in many LLNs, the variability comes as a result of trading
power consumption for bit rate. There are several MAC layer power consumption for bit rate. There are several MAC layer
protocols which allow for the effective bit rate and power protocols which allow for the effective bit rate of a link to vary
consumption of a link to vary over more than three orders of over more than three orders of magnitude with a corresponding change
magnitude, with a corresponding change in power consumption. For in power consumption. For efficient operation, it may be desirable
efficient operation, it may be desirable for nodes to report the for nodes to report the range of throughput that their links can
range of throughput that their links can handle in addition to the handle in addition to the currently available throughput.
currently available throughput.
The Throughput object MAY be present in the DAG Metric Container. The Throughput object MAY be present in the DAG Metric Container.
There MUST be no more than one Throughput object as a constraint per There MUST NOT be more than one Throughput object as a constraint per
DAG Metric Container, and no more than one Throughput object as a DAG Metric Container, and there MUST NOT be more than one Throughput
metric per DAG Metric Container. object as a metric per DAG Metric Container.
The Throughput object is made of throughput sub-objects and MUST at The Throughput object is made of throughput sub-objects and MUST at
least comprise one Throughput sub-object. The first Throughput sub- least comprise one Throughput sub-object. The first Throughput sub-
object MUST be the most recently estimated actual throughput. The object MUST be the most recently estimated actual throughput. The
actual estimation of the throughput is outside the scope of this actual estimation of the throughput is outside the scope of this
document. document.
Each Throughput sub-object has a fixed length of 4 bytes. Each Throughput sub-object has a fixed length of 4 bytes.
The Throughput object does not contain any additional TLV. The Throughput object does not contain any additional TLV.
The Throughput object Type is to be assigned by IANA (recommended The Throughput object Type is to be assigned by IANA (recommended
value=4) value=4)
The format of the Throughput object body is as follows: The format of the Throughput object body is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (sub-object) ..... | (sub-object) .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Throughput object body format Figure 8: Throughput object body format
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Throughput | | Throughput |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Throughput sub-object format Figure 9: Throughput sub-object format
Throughput: 32 bits. The Throughput is encoded in 32 bits in Throughput: 32 bits. The Throughput is encoded in 32 bits in
unsigned integer format, expressed in bytes per second. unsigned integer format, expressed in bytes per second.
4.2. Latency 4.2. Latency
Similarly to throughput, the latency of many LLN MAC sub-layers can Similarly to throughput, the latency of many LLN MAC sub-layers can
vary over many orders of magnitude, again with a corresponding change vary over many orders of magnitude, again with a corresponding change
in current consumption. Some LLN MAC link layers will allow the in power consumption. Some LLN MAC link layers will allow the
latency to be adjusted globally on the subnet, on a link-by-link latency to be adjusted globally on the subnet, on a link-by-link
basis, or not at all. Some will insist that it be fixed for a given basis, or not at all. Some will insist that it be fixed for a given
link, but allow it to be variable from link to link. link, but allow it to be variable from link to link.
The Latency object MAY be present in the DAG Metric Container. There The Latency object MAY be present in the DAG Metric Container. There
MUST be no more than one Latency object as a constraint per DAG MUST NOT be more than one Latency object as a constraint per DAG
Metric Container, and no more than one Latency object as a metric per Metric Container, and there MUST NOT be more than one Latency object
DAG Metric Container. as a metric per DAG Metric Container.
The Latency object is made of Latency sub-objects and MUST at least The Latency object is made of Latency sub-objects and MUST at least
comprise one Latency sub-object. Each Latency sub-object has a fixed comprise one Latency sub-object. Each Latency sub-object has a fixed
length of 4 bytes. length of 4 bytes.
The Latency object does not contain any additional TLV. The Latency object does not contain any additional TLV.
The Latency object Type is to be assigned by IANA (recommended The Latency object Type is to be assigned by IANA (recommended
value=5) value=5)
The Latency object is a metric or constraint. The Latency object is a metric or constraint.
The format of the Latency object body is as follows: The format of the Latency object body is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (sub-object) ..... | (sub-object) .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Latency object body format Figure 10: Latency object body format
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latency | | Latency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Latency sub-object format Figure 11: Latency sub-object format
Latency: 32 bits. The Latency is encoded in 32 bits in unsigned Latency: 32 bits. The Latency is encoded in 32 bits in unsigned
integer format, expressed in microseconds. integer format, expressed in microseconds.
The Latency object may be used as a constraint or a path metric. For The Latency object may be used as a constraint or a path metric. For
example, one may want the latency not to exceed some value. In this example, one may want the latency not to exceed some value. In this
case, the Latency object common header indicates that the provided case, the Latency object common header indicates that the provided
value relates to a constraint. In another example, the Latency value relates to a constraint. In another example, the Latency
object may be used as an aggregated additive metric where the value object may be used as an aggregated additive metric where the value
is updated along the path to reflect the path latency. is updated along the path to reflect the path latency.
4.3. Link reliability 4.3. Link Reliability
In LLNs, link reliability is degraded by external interference and In LLNs, link reliability is degraded by external interference and
multi-path interference (wireless links). Multipath typically multi-path interference (wireless links). Multipath typically
affects both directions on the link equally, whereas external affects both directions on the link equally, whereas external
interference is sometimes unidirectional. Time scales vary from interference is sometimes unidirectional. Time scales vary from
milliseconds to days, and are often periodic and linked to human milliseconds to days, and are often periodic and linked to human
activity. Packet error rates can generally be measured directly, and activity. Packet error rates can generally be measured directly, and
other metrics (e.g. bit error rate, mean time between failures) are other metrics (e.g. bit error rate, mean time between failures) are
typically derived from that. Note that such variability is not typically derived from that. Note that such variability is not
specific to wireless link but also applies to PLC links. specific to wireless link but also applies to PLC links.
skipping to change at page 20, line 8 skipping to change at page 20, line 8
quality may be taken into account as a critical routing metric. quality may be taken into account as a critical routing metric.
A number of link reliability metrics could be defined reflecting A number of link reliability metrics could be defined reflecting
several reliability aspects. Two link reliability metrics are several reliability aspects. Two link reliability metrics are
defined in this document: the Link Quality Level (LQL) and the defined in this document: the Link Quality Level (LQL) and the
Expected Transmission count Metric (ETX). Expected Transmission count Metric (ETX).
Note that an RPL implementation MAY either use the LQL, the ETX or Note that an RPL implementation MAY either use the LQL, the ETX or
both. both.
4.3.1. The Link Quality Level reliability metric 4.3.1. The Link Quality Level Reliability Metric
The Link Quality Level (LQL) object is used to quantify the link The Link Quality Level (LQL) object is used to quantify the link
reliability using a discrete value, from 0 to 7 where 0 indicates reliability using a discrete value, from 0 to 7 where 0 indicates
that the link quality level is unknown and 1 reports the highest link that the link quality level is unknown and 1 reports the highest link
quality level. The mechanisms and algorithms used to compute the LQL quality level. The mechanisms and algorithms used to compute the LQL
are implementation specific and outside of the scope of this are implementation specific and outside of the scope of this
document. document.
The LQL can either be used as a metric or a constraint. When used as The LQL can either be used as a metric or a constraint. When used as
a metric, the LQL metric can be recorded or aggregated. For example, a metric, the LQL metric can be recorded or aggregated. For example,
skipping to change at page 20, line 33 skipping to change at page 20, line 33
a LQL value of 3 or less"). By contrast, the LQL link metric may be a LQL value of 3 or less"). By contrast, the LQL link metric may be
aggregated, in which case the sum of all LQLs may be reported aggregated, in which case the sum of all LQLs may be reported
(additive metric) or the minimum value may be reported along the (additive metric) or the minimum value may be reported along the
path. path.
When used as a recorded metric, counters are used to compress the When used as a recorded metric, counters are used to compress the
information: for each encountered LQL value, only the number of information: for each encountered LQL value, only the number of
matching links is reported. matching links is reported.
The LQL object MAY be present in the DAG Metric Container. There The LQL object MAY be present in the DAG Metric Container. There
MUST be no more than one LQL object as a constraint per DAG Metric MUST NOT be more than one LQL object as a constraint per DAG Metric
Container, and no more than one LQL object as a metric per DAG Metric Container, and there MUST NOT be more than one LQL object as a metric
Container. per DAG Metric Container.
The LQL object MUST contain one or more sub-object used to report the The LQL object MUST contain one or more sub-object used to report the
number of links along with their LQL. number of links along with their LQL.
The LQL object Type is to be assigned by IANA (recommended value=6) The LQL object Type is to be assigned by IANA (recommended value=6)
The format of the LQL object body is as follows: The format of the LQL object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| Res | LQL sub-object | Res | LQL sub-object
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 12: LQL object format Figure 12: LQL object body format
Res flags (8 bits): Reserved field. This field MUST be set to zero
on transmission and MUST be ignored on receipt.
When the LQL metric is recorded, the LQL object body comprises one or When the LQL metric is recorded, the LQL object body comprises one or
more LQL Type 1 sub-object. more LQL Type 1 sub-object.
The format of the LQL Type 1 sub-object is as follows The format of the LQL Type 1 sub-object is as follows
0 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| Val | Counter | | Val | Counter |
skipping to change at page 21, line 26 skipping to change at page 21, line 29
Val: LQL value from 0 to 7 where 0 means undetermined and 1 indicates Val: LQL value from 0 to 7 where 0 means undetermined and 1 indicates
the highest link quality. the highest link quality.
Counter: number of links with that value. Counter: number of links with that value.
When the LQL metric is aggregated, the LQL object body comprises one When the LQL metric is aggregated, the LQL object body comprises one
LQL Type 2 sub-object: LQL Type 2 sub-object:
The format of the LQL Type 2 sub-object is as follows The format of the LQL Type 2 sub-object is as follows
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Aggregated LQL Value | | Aggregated LQL Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: LQL Type 2 sub-object format Figure 14: LQL Type 2 sub-object format
Aggregated LQL Value: when used as an additive metric (A=0x00), the Aggregated LQL Value: when used as an additive metric (A=0x00), the
aggregated LQL value reports the sum of all the LQL values for all aggregated LQL value reports the sum of all the LQL values for all
links along the path. When used to report a minimum (A=0x02), the links along the path. When used to report a minimum (A=0x02), the
skipping to change at page 22, line 11 skipping to change at page 22, line 14
successfully deliver a packet. In contrast with the LQL routing successfully deliver a packet. In contrast with the LQL routing
metric, the ETX provides a discrete value (wich may not be an metric, the ETX provides a discrete value (wich may not be an
integer) computed according to a specific formula: for example, an integer) computed according to a specific formula: for example, an
implementation may use the following formula: ETX= 1 / (Df * Dr) implementation may use the following formula: ETX= 1 / (Df * Dr)
where Df is the measured probability that a packet is received by the where Df is the measured probability that a packet is received by the
neighbor and Dr is the measured probability that the acknowledgment neighbor and Dr is the measured probability that the acknowledgment
packet is successfully received. This document does not mandate the packet is successfully received. This document does not mandate the
use of a specific formula to compute the ETX value. use of a specific formula to compute the ETX value.
The ETX object MAY be present in the DAG Metric Container. There The ETX object MAY be present in the DAG Metric Container. There
MUST be no more than one ETX object as a constraint per DAG Metric MUST NOT be more than one ETX object as a constraint per DAG Metric
Container, and no more than one ETX object as a metric per DAG Metric Container, and there MUST NOT be more than one ETX object as a metric
Container. per DAG Metric Container.
The ETX object is made of ETX sub-objects and MUST at least comprise The ETX object is made of ETX sub-objects and MUST at least comprise
one ETX sub-object. Each ETX sub-object has a fixed length of 8 one ETX sub-object. Each ETX sub-object has a fixed length of 8
bits. bits.
The ETX object does not contain any additional TLV. The ETX object does not contain any additional TLV.
The ETX object Type is to be assigned by IANA (recommended value=7) The ETX object Type is to be assigned by IANA (recommended value=7)
The format of the ETX object body is as follows: The format of the ETX object body is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (sub-object) ..... | (sub-object) .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: ETX object body format Figure 15: ETX object body format
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ETX | | ETX |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: ETX sub-object format Figure 16: ETX sub-object format
ETX: 16 bits. The ETX * 128 is encoded using 16 bits in unsigned ETX: 16 bits. The ETX * 128 is encoded using 16 bits in unsigned
integer format, rounded off to the nearest whole number. For integer format, rounded off to the nearest whole number. For
example, if ETX = 3.569, the object value will be 457. If ETX > example, if ETX = 3.569, the object value will be 457. If ETX >
skipping to change at page 23, line 13 skipping to change at page 23, line 16
example, the ETX object may be used as an aggregated additive metric example, the ETX object may be used as an aggregated additive metric
where the value is updated along the path to reflect the path where the value is updated along the path to reflect the path
quality: when a node receives the aggregated additive ETX value of quality: when a node receives the aggregated additive ETX value of
the path (cummulative path ETX calculated as the sum of the link ETX the path (cummulative path ETX calculated as the sum of the link ETX
of all of the traversed links from the advertising node to the DAG of all of the traversed links from the advertising node to the DAG
root), if it selects that node as its preferred parent, the node root), if it selects that node as its preferred parent, the node
updates the path ETX by adding the ETX of the local link between updates the path ETX by adding the ETX of the local link between
itself and the preferred parent to the received path cost (path ETX) itself and the preferred parent to the received path cost (path ETX)
before potentially advertising itself the new path ETX. before potentially advertising itself the new path ETX.
4.4. Link Color object 4.4. Link Color Object
4.4.1. Link Color object description 4.4.1. Link Color Object Description
The Link Color (LC) object is an administrative 10-bit link The Link Color (LC) object is an administrative 10-bit link
constraint (which may either be static or dynamically adjusted) used constraint (which may either be static or dynamically adjusted) used
to avoid or attract specific links for specific traffic types. to avoid or attract specific links for specific traffic types.
The LC object can either be used as a metric or as a constraint. The LC object can either be used as a metric or as a constraint.
When used as a metric, the LC metric can only be recorded. For When used as a metric, the LC metric can only be recorded. For
example, the DAG may require recording the link colors for all example, the DAG may require recording the link colors for all
traversed links. Each node can then use the LC to select the parent traversed links. A color is defined as a specific set of bit values:
based on user defined rules (e.g. "select the path with the maximum in other words, that 10-bit field is a flag field, and not a scalar
number of links having their first bit set 1 (e.g. encrypted value. Each node can then use the LC to select the parent based on
links)"). The LC object may also be used as a constraint. user defined rules (e.g. "select the path with the maximum number of
links having their first bit set 1 (e.g. encrypted links)"). The LC
object may also be used as a constraint.
When used as a recorded metric, a counter is used to compress the When used as a recorded metric, a counter is used to compress the
information where the number of links for each Link Color is information where the number of links for each Link Color is
reported. reported.
The Link Color (LC) object MAY be present in the DAG Metric The Link Color (LC) object MAY be present in the DAG Metric
Container. There MUST be no more than one LC object as a constraint Container. There MUST NOT be more than one LC object as a constraint
per DAG Metric Container, and no more than one LC object as a metric per DAG Metric Container, and there MUST NOT be more than one LC
per DAG Metric Container. object as a metric per DAG Metric Container.
There MUST be a at least one LC sub-object per LC object. There MUST be a at least one LC sub-object per LC object.
The LC object does not contain any additional TLV. The LC object does not contain any additional TLV.
The LC object Type is to be assigned by IANA (recommended value=8) The LC object Type is to be assigned by IANA (recommended value=8)
The format of the LC object body is as follows: The format of the LC object body is as follows:
0 1 2 3 0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
| Res | LC sub-objects | Res | LC sub-objects
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 17: LC object format Figure 17: LC object format
Res flags (8 bits): Reserved field. This field MUST be set to zero
on transmission and MUST be ignored on receipt.
When the LC object is used as a recorded metric, the LC object body When the LC object is used as a recorded metric, the LC object body
comprises one or more LC Type 1 sub-objects. comprises one or more LC Type 1 sub-objects.
The format of the LC Type 1 sub-object body is as follows: The format of the LC Type 1 sub-object body is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Color | Counter | | Link Color | Counter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: LC Type 1 sub-object format Figure 18: LC Type 1 sub-object format
When the LC object is used as a constraint, the LC object body When the LC object is used as a constraint, the LC object body
comprises one or more LC Type 2 sub-objects. comprises one or more LC Type 2 sub-objects.
The format of the LC Type 2 sub-object body is as follows: The format of the LC Type 2 sub-object body is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Color |I| | Link Color |Reserved |I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: LC Type 2 sub-object format Figure 19: LC Type 2 sub-object format
Res flags (7 bits): Reserved field. This field MUST be set to zero
on transmission and MUST be ignored on receipt.
I Bit: The I bit is only relevant when the Link Color is used as a I Bit: The I bit is only relevant when the Link Color is used as a
constraint. When cleared, this indicates that links with the constraint. When cleared, this indicates that links with the
specified color must be included. When set, this indicates that specified color must be included. When set, this indicates that
links with the specified color must be excluded. links with the specified color must be excluded.
The use of the LC object is outside the scope of this document. It is left to the implementer to define the meaning of each bit of
the 10-bit Link Color Flag field.
4.4.2. Mode of operation 4.4.2. Mode of operation
The link color may be used as a constraint or a metric. The link color may be used as a constraint or a metric.
o When used as constraint, the LC object may be inserted in the DAG o When used as constraint, the LC object may be inserted in the DAG
Metric Container to indicate that links with a specific color Metric Container to indicate that links with a specific color
should be included or excluded from the computed path. should be included or excluded from the computed path.
o When used as recorded metric, each node along the path may insert o When used as recorded metric, each node along the path may insert
a LC object in the DAG Metric Container to report the color of the a LC object in the DAG Metric Container to report the color of the
local link. If there is already a LC object reporting a similar local link. If there is already a LC object reporting a similar
color, the node MUST NOT add another identical LC sub-object and color, the node MUST NOT add another identical LC sub-object and
MUST increment the counter field. MUST increment the counter field.
5. Computation of dynamic metrics and attributes 5. Computation of Dynamic Metrics and Attributes
As already pointed out, dynamically calculated metrics are of the As already pointed out, dynamically calculated metrics are of the
utmost importance in many circumstances in LLNs. This is mainly utmost importance in many circumstances in LLNs. This is mainly
because a variety of metrics change on a frequent basis, thus because a variety of metrics change on a frequent basis, thus
implying the need to adapt the routing decisions. That being said, implying the need to adapt the routing decisions. That being said,
care must be given to the pace at which changes are reported in the care must be given to the pace at which changes are reported in the
network. The attributes will change according to their own time network. The attributes will change according to their own time
scales. RPL controls the reporting rate. scales. RPL controls the reporting rate.
To minimize metric updates, multi-threshold algorithms MAY be used to To minimize metric updates, multi-threshold algorithms MAY be used to
skipping to change at page 26, line 6 skipping to change at page 26, line 12
IANA is requested to establish a new top-level registry to contain IANA is requested to establish a new top-level registry to contain
all Routing Metric/Constraint objects codepoints and sub-registries. all Routing Metric/Constraint objects codepoints and sub-registries.
The allocation policy for each new registry is by IETF Consensus: new The allocation policy for each new registry is by IETF Consensus: new
values are assigned through the IETF consensus process (see values are assigned through the IETF consensus process (see
[RFC5226]). Specifically, new assignments are made via RFCs approved [RFC5226]). Specifically, new assignments are made via RFCs approved
by the IESG. Typically, the IESG will seek input on prospective by the IESG. Typically, the IESG will seek input on prospective
assignments from appropriate persons (e.g., a relevant Working Group assignments from appropriate persons (e.g., a relevant Working Group
if one exists). if one exists).
6.1. Routing Metric/Constraint type 6.1. Routing Metric/Constraint Type
IANA is requested to create a registry for Routing Metric/Constraint IANA is requested to create a registry for Routing Metric/Constraint
objects. Each Routing Metric/Constraint object has a type value. objects. Each Routing Metric/Constraint object has a type value.
Value Meaning Reference Value Meaning Reference
1 Node State and Attribute This document 1 Node State and Attribute This document
2 Node Energy This document 2 Node Energy This document
3 Hop Count This document 3 Hop Count This document
4 Link Throughput This document 4 Link Throughput This document
5 Link Latency This document 5 Link Latency This document
6 Link Quality Level This document 6 Link Quality Level This document
7 Link ETX This document 7 Link ETX This document
8 Link Color This document 8 Link Color This document
6.2. Routing Metric/Constraint common header 6.2. Routing Metric/Constraint TLV
IANA is requested to create a registry used for all TLVs carried
within Routing Metric/Constraint objects.
6.3. Routing Metric/Constraint Common Header
IANA is requested to create a registry to manage the codespace of the IANA is requested to create a registry to manage the codespace of the
A field of the Routing Metric/Constraint common header. A field of the Routing Metric/Constraint common header.
Codespace of the A field (Routing Metric/Constraint common header) Codespace of the A field (Routing Metric/Constraint common header)
Value Meaning Reference Value Meaning Reference
0 Routing metric is additive This document 0 Routing metric is additive This document
1 Routing metric reports a maximum This document 1 Routing metric reports a maximum This document
2 Routing metric reports a minimum This document 2 Routing metric reports a minimum This document
skipping to change at page 27, line 9 skipping to change at page 27, line 15
o Defining RFC o Defining RFC
Several bits are defined for the Routing Metric/Constraint common Several bits are defined for the Routing Metric/Constraint common
header in this document. The following values have been assigned: header in this document. The following values have been assigned:
Codespace of the Flag field (Routing Metric/Constraint common header) Codespace of the Flag field (Routing Metric/Constraint common header)
Bit Description Reference Bit Description Reference
12-15 Precedence This document 12-15 Precedence This document
9-11 Additive/Max/Min/Multi This document 9-11 Additive/Max/Min/Multi This document
8 Recorded/Aggregated This document 8 Recorded/Aggregated This document
7 Optional Constraint This document 7 Optional Constraint This document
6 Constraint/Metric This document 6 Constraint/Metric This document
5 P (Partial) This document 5 P (Partial) This document
6.3. NSA object 6.4. NSA Object
IANA is requested to create a registry to manage the codespace of the IANA is requested to create a registry to manage the codespace of the
Flag field of the NSA object. Flag field of the NSA object.
New bit numbers may be allocated only by an IETF Consensus action. New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities: Each bit should be tracked with the following qualities:
o Bit number o Bit number
o Capability Description o Capability Description
skipping to change at page 27, line 38 skipping to change at page 27, line 44
Several bits are defined for the NSA object flag field in this Several bits are defined for the NSA object flag field in this
document. The following values have been assigned: document. The following values have been assigned:
Codespace of the Flag field (NSA object) Codespace of the Flag field (NSA object)
Bit Description Reference Bit Description Reference
14 Aggregator This document 14 Aggregator This document
15 Overloaded This document 15 Overloaded This document
6.4. Hop-Count object 6.5. Hop-Count Object
IANA is requested to create a registry to manage the codespace of the IANA is requested to create a registry to manage the codespace of the
Flag field of the Hop-count object. Flag field of the Hop-count object.
New bit numbers may be allocated only by an IETF Consensus action. New bit numbers may be allocated only by an IETF Consensus action.
Each bit should be tracked with the following qualities: Each bit should be tracked with the following qualities:
o Bit number o Bit number
o Capability Description o Capability Description
o Defining RFC o Defining RFC
No Flag is currently defined. No Flag is currently defined.
7. Security considerations 7. Security Considerations
Routing metrics should be handled in a secure and trustful manner. Routing metrics should be handled in a secure and trustful manner.
For instance, RPL should not allow a malicious node to falsely For instance, RPL should not allow a malicious node to falsely
advertise that it has good metrics for routing, be added as a router advertise that it has good metrics for routing, be added as a router
for other nodes' traffic and intercept packets. Since the routing for other nodes' traffic and intercept packets. Another attack may
metrics/constraints are carried within RPL message, the security consist of making intermitment attacks on a link in an attempt to
routing mechanisms defined in [I-D.ietf-roll-rpl] applies here. constantly modify the link quality and consequently the associated
routing metric, thus leading to potential fluctuation in the DAG. It
is thus RECOMMENDED for a RPL implementation to put in place
mechanism so as to stop advertising routing metrics for highly
unstable links that may be subject to attacks.
Since the routing metrics/constraints are carried within RPL message,
the security routing mechanisms defined in [I-D.ietf-roll-rpl]
applies here.
8. Acknowledgements 8. Acknowledgements
The authors would like to acknowledge the contributions of Young Jae The authors would like to acknowledge the contributions of Young Jae
Kim, Hakjin Chong, David Meyer, Mischa Dohler, Anders Brandt, Philip Kim, Hakjin Chong, David Meyer, Mischa Dohler, Anders Brandt, Philip
Levis, Pascal Thubert, Richard Kelsey, Jonathan Hui, Alexandru Levis, Pascal Thubert, Richard Kelsey, Jonathan Hui, Alexandru
Petrescu, Richard Kelsey, Mathilde Durvy, Phoebus Chen, Tim Winter, Petrescu, Richard Kelsey, Mathilde Durvy, Phoebus Chen, Tim Winter,
Mukul Goyal, Yoav Ben-Yehezkel, Matteo Paris, Omprakash Gnawali, Mads Mukul Goyal, Yoav Ben-Yehezkel, Matteo Paris, Omprakash Gnawali, Mads
Westergreen, Mukul Goyal and David Culler for their review and Westergreen, Mukul Goyal and David Culler for their review and
valuable comments. valuable comments. Special thank to Adrian Farrel for his thourough
review.
9. References 9. References
9.1. Normative references 9.1. Normative references
[I-D.ietf-roll-rpl]
Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., and J.
Vasseur, "RPL: IPv6 Routing Protocol for Low power and
Lossy Networks", draft-ietf-roll-rpl-15 (work in
progress), November 2010.
[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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
9.2. Informative references 9.2. Informative references
[I-D.ietf-roll-rpl]
Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
Kelsey, R., Levis, P., Networks, D., Struik, R., and J.
Vasseur, "RPL: IPv6 Routing Protocol for Low power and
Lossy Networks", draft-ietf-roll-rpl-14 (work in
progress), October 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-04 (work in Networks", draft-ietf-roll-terminology-04 (work in
progress), September 2010. progress), September 2010.
[Khanna1989J A. Zinky, A. Khanna, and G. Vichniac. "Performance of
the Revised Routing Metric for ARPANET and MILNET.
Submitted to MILCOM 89, March 1989
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, December 1990. dual environments", RFC 1195, December 1990.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS", McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, September 1999. RFC 2702, September 1999.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
skipping to change at page 29, line 31 skipping to change at page 30, line 5
Networks", RFC 5673, October 2009. Networks", RFC 5673, October 2009.
[RFC5826] Brandt, A., Buron, J., and G. Porcu, "Home Automation [RFC5826] 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",
RFC 5826, April 2010. RFC 5826, April 2010.
[RFC5867] Martocci, J., De Mil, P., Riou, N., and W. Vermeylen, [RFC5867] Martocci, J., De Mil, P., Riou, N., and W. Vermeylen,
"Building Automation Routing Requirements in Low-Power and "Building Automation Routing Requirements in Low-Power and
Lossy Networks", RFC 5867, June 2010. Lossy Networks", RFC 5867, June 2010.
[Khanna1989J A. Zinky, A. Khanna, and G. Vichniac. "Performance of
the Revised Routing Metric for ARPANET and MILNET.
Submitted to MILCOM 89, March 1989
Authors' Addresses Authors' Addresses
JP Vasseur (editor) JP Vasseur (editor)
Cisco Systems, Inc Cisco Systems, Inc
11, Rue Camille Desmoulins 11, Rue Camille Desmoulins
Issy Les Moulineaux, 92782 Issy Les Moulineaux, 92782
France France
Email: jpv@cisco.com Email: jpv@cisco.com
 End of changes. 107 change blocks. 
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