draft-ietf-roll-applicability-home-building-12.txt   rfc7733.txt 
Roll A. Brandt Internet Engineering Task Force (IETF) A. Brandt
Internet-Draft Sigma Designs Request for Comments: 7733 Sigma Designs
Intended status: Standards Track E. Baccelli Category: Standards Track E. Baccelli
Expires: January 22, 2016 INRIA ISSN: 2070-1721 INRIA
R. Cragie R. Cragie
ARM Ltd. ARM Ltd.
P. van der Stok P. van der Stok
Consultant Consultant
July 21, 2015 February 2016
Applicability Statement: The use of the RPL protocol suite in Home Applicability Statement: The Use of the Routing Protocol
Automation and Building Control for Low-Power and Lossy Networks (RPL) Protocol Suite
draft-ietf-roll-applicability-home-building-12 in Home Automation and Building Control
Abstract Abstract
The purpose of this document is to provide guidance in the selection The purpose of this document is to provide guidance in the selection
and use of protocols from the RPL protocol suite to implement the and use of protocols from the Routing Protocol for Low-Power and
features required for control in building and home environments. Lossy Networks (RPL) protocol suite to implement the features
required for control in building and home environments.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79.
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Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on January 22, 2016. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7733.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................4
1.1. Relationship to other documents . . . . . . . . . . . . . 4 1.1. Relationship to Other Documents ............................5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology ................................................6
1.3. Required Reading . . . . . . . . . . . . . . . . . . . . 5 1.3. Required Reading ...........................................6
1.4. Out of scope requirements . . . . . . . . . . . . . . . . 5 1.4. Requirements That Are Out of Scope .........................6
2. Deployment Scenario . . . . . . . . . . . . . . . . . . . . . 5 2. Deployment Scenario .............................................6
2.1. Network Topologies . . . . . . . . . . . . . . . . . . . 6 2.1. Network Topologies .........................................7
2.2. Traffic Characteristics . . . . . . . . . . . . . . . . . 7 2.2. Traffic Characteristics ....................................8
2.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.1. General .............................................9
2.2.2. Source-sink (SS) communication paradigm . . . . . . . 8 2.2.2. Source-Sink (SS) Communication Paradigm ............10
2.2.3. Publish-subscribe (PS, or pub/sub)) communication 2.2.3. Publish-Subscribe (PS, or Pub/Sub)
paradigm . . . . . . . . . . . . . . . . . . . . . . 9 Communication Paradigm .............................10
2.2.4. Peer-to-peer (P2P) communication paradigm . . . . . . 9 2.2.4. Peer-to-Peer (P2P) Communication Paradigm ..........10
2.2.5. Peer-to-multipeer (P2MP) communication paradigm . . . 10 2.2.5. Peer-to-Multipeer (P2MP) Communication Paradigm ....11
2.2.6. Additional considerations: Duocast and N-cast . . . . 10 2.2.6. Additional Considerations: Duocast and N-Cast ......11
2.2.7. RPL applicability per communication paradigm . . . . 10 2.2.7. RPL Applicability per Communication Paradigm .......11
2.3. Layer-2 applicability . . . . . . . . . . . . . . . . . . 11 2.3. Layer 2 Applicability .....................................13
3. Using RPL to meet Functional Requirements . . . . . . . . . . 12 3. Using RPL to Meet Functional Requirements ......................13
4. RPL Profile . . . . . . . . . . . . . . . . . . . . . . . . . 13 4. RPL Profile ....................................................14
4.1. RPL Features . . . . . . . . . . . . . . . . . . . . . . 13 4.1. RPL Features ..............................................14
4.1.1. RPL Instances . . . . . . . . . . . . . . . . . . . . 13 4.1.1. RPL Instances ......................................15
4.1.2. Storing vs. Non-Storing Mode . . . . . . . . . . . . 14 4.1.2. Storing vs. Non-Storing Mode .......................15
4.1.3. DAO Policy . . . . . . . . . . . . . . . . . . . . . 14 4.1.3. DAO Policy .........................................15
4.1.4. Path Metrics . . . . . . . . . . . . . . . . . . . . 14 4.1.4. Path Metrics .......................................15
4.1.5. Objective Function . . . . . . . . . . . . . . . . . 14 4.1.5. Objective Function .................................16
4.1.6. DODAG Repair . . . . . . . . . . . . . . . . . . . . 14 4.1.6. DODAG Repair .......................................16
4.1.7. Multicast . . . . . . . . . . . . . . . . . . . . . . 15 4.1.7. Multicast ..........................................16
4.1.8. Security . . . . . . . . . . . . . . . . . . . . . . 16 4.1.8. Security ...........................................17
4.1.9. P2P communications . . . . . . . . . . . . . . . . . 19 4.1.9. P2P Communications .................................21
4.1.10. IPv6 address configuration . . . . . . . . . . . . . 19 4.1.10. IPv6 Address Configuration ........................21
4.2. Layer 2 features . . . . . . . . . . . . . . . . . . . . 19 4.2. Layer 2 Features ..........................................21
4.2.1. Specifics about layer-2 . . . . . . . . . . . . . . . 19 4.2.1. Specifics about Layer 2 ............................21
4.2.2. Services provided at layer-2 . . . . . . . . . . . . 19 4.2.2. Services Provided at Layer 2 .......................21
4.2.3. 6LowPAN options assumed . . . . . . . . . . . . . . . 20 4.2.3. IPv6 over Low-Power Wireless Personal Area
4.2.4. Mesh Link Establishment (MLE) and other things . . . 20 Network (6LoWPAN) Options Assumed ..................21
4.3. Recommended Configuration Defaults and Ranges . . . . . . 20 4.2.4. Mesh Link Establishment (MLE) and Other Things .....21
4.3.1. Trickle parameters . . . . . . . . . . . . . . . . . 20 4.3. Recommended Configuration Defaults and Ranges .............21
4.3.2. Other Parameters . . . . . . . . . . . . . . . . . . 20 4.3.1. Trickle Parameters .................................22
5. MPL Profile . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.3.2. Other Parameters ...................................22
5.1. Recommended configuration Defaults and Ranges . . . . . . 21 5. MPL Profile ....................................................23
5.1.1. Real-Time optimizations . . . . . . . . . . . . . . . 21 5.1. Recommended Configuration Defaults and Ranges .............23
5.1.2. Trickle parameters . . . . . . . . . . . . . . . . . 21 5.1.1. Real-Time Optimizations ............................23
5.1.3. Other parameters . . . . . . . . . . . . . . . . . . 22 5.1.2. Trickle Parameters .................................23
6. Manageability Considerations . . . . . . . . . . . . . . . . 23 5.1.3. Other Parameters ...................................24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 6. Manageability Considerations ...................................25
7.1. Security considerations during initial deployment . . . . 23 7. Security Considerations ........................................25
7.2. Security Considerations during incremental deployment . . 24 7.1. Security Considerations during Initial Deployment .........26
7.3. Security Considerations for P2P uses . . . . . . . . . . 25 7.2. Security Considerations during Incremental Deployment .....27
7.4. MPL routing . . . . . . . . . . . . . . . . . . . . . . . 25 7.3. Security Considerations for P2P Implementations ...........27
7.5. RPL Security features . . . . . . . . . . . . . . . . . . 25 7.4. MPL Routing ...............................................27
8. Other related protocols . . . . . . . . . . . . . . . . . . . 25 7.5. RPL Security Features .....................................27
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 8. Other Related Protocols ........................................28
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 9. References .....................................................28
11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.1. Normative References ......................................28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 9.2. Informative References ....................................32
12.1. Normative References . . . . . . . . . . . . . . . . . . 28 Appendix A. RPL Shortcomings in Home and Building Deployments .....35
12.2. Informative References . . . . . . . . . . . . . . . . . 32 A.1. Risk of Undesirable Long P2P Routes ........................35
Appendix A. RPL shortcomings in home and building deployments . 33 A.1.1. Traffic Concentration at the Root ......................35
A.1. Risk of undesired long P2P routes . . . . . . . . . . . . 33 A.1.2. Excessive Battery Consumption in Source Nodes ..........35
A.1.1. Traffic concentration at the root . . . . . . . . . . 34 A.2. Risk of Delayed Route Repair ...............................35
A.1.2. Excessive battery consumption in source nodes . . . . 34 A.2.1. Broken Service .........................................36
A.2. Risk of delayed route repair . . . . . . . . . . . . . . 34 Appendix B. Communication Failures ................................36
A.2.1. Broken service . . . . . . . . . . . . . . . . . . . 34 Acknowledgements ..................................................38
Appendix B. Communication failures . . . . . . . . . . . . . . . 35 Authors' Addresses ................................................38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction 1. Introduction
The primary purpose of this document is to give guidance in the use The primary purpose of this document is to give guidance in the use
of the Routing Protocol for Low power and lossy networks (RPL) of the Routing Protocol for Low-Power and Lossy Networks (RPL)
protocol suite in two application domains: protocol suite in two application domains:
o Home automation o Home automation
o Building automation o Building automation
The guidance is based on the features required by the requirements The guidance is based on the features required by the requirements
documents "Home Automation Routing Requirements in Low-Power and documents "Home Automation Routing Requirements in Low-Power and
Lossy Networks" [RFC5826] and "Building Automation Routing Lossy Networks" [RFC5826] and "Building Automation Routing
Requirements in Low-Power and Lossy Networks" [RFC5867] respectively. Requirements in Low-Power and Lossy Networks" [RFC5867],
The Advanced Metering Infrastructure is also considered where respectively. The Advanced Metering Infrastructure is also
appropriate. The applicability domains distinguish themselves in the considered where appropriate. The applicability domains distinguish
way they are operated, their performance requirements, and the most themselves in the way they are operated, their performance
likely network structures. An abstract set of distinct communication requirements, and the most likely network structures. An abstract
paradigms is then used to frame the applicability domains. set of distinct communication paradigms is then used to frame the
applicability domains.
Home automation and building automation application domains share a Home automation and building automation application domains share a
substantial number of properties: substantial number of properties:
o In both domains, the network can be disconnected from the ISP and o In both domains, the network can be disconnected from the ISP and
must still continue to provide control to the occupants of the must still continue to provide control to the occupants of the
home/building. Routing needs to be possible independent of the home or building. Routing needs to be possible independent of the
existence of a border router existence of a border router.
o Both domains are subject to unreliable links but require instant o Both domains are subject to unreliable links but require instant
and very reliable reactions. This has impact on routing because and very reliable reactions. This has an impact on routing
of timeliness and multipath routing. because of timeliness and multipath routing.
The differences between the two application domains mostly appear in The differences between the two application domains mostly appear in
commissioning, maintenance and the user interface, which do not commissioning, maintenance, and the user interface, which do not
typically affect routing. Therefore, the focus of this applicability typically affect routing. Therefore, the focus of this applicability
document is on reliability, timeliness, and local routing. document is on reliability, timeliness, and local routing.
It should be noted that adherence to the guidance does not It should be noted that adherence to the guidance in this document
necessarily guarantee fully interoperable solutions in home does not necessarily guarantee fully interoperable solutions in home
automation networks and building control networks and that additional automation networks and building control networks and that additional
rigorous and managed programs will be needed to ensure rigorous and managed programs will be needed to ensure
interoperability. interoperability.
1.1. Relationship to other documents 1.1. Relationship to Other Documents
The Routing Over Low power and Lossy networks (ROLL) working group The Routing Over Low power and Lossy networks (ROLL) working group
has specified a set of routing protocols for Low-Power and Lossy has specified a set of routing protocols for Low-Power and Lossy
Networks (LLN) [RFC6550]. This applicability text describes a subset Networks (LLNs) [RFC6550]. This applicability text describes a
of those protocols and the conditions under which the subset is subset of those protocols and the conditions under which the subset
appropriate and provides recommendations and requirements for the is appropriate, and it provides recommendations and requirements for
accompanying parameter value ranges. the accompanying parameter value ranges.
In addition, an extension document has been produced specifically to In addition, [RFC6997] was written specifically as an extension to
provide a solution for reactive discovery of point-to-point routes in core RPL [RFC6550] and provides a solution for reactive discovery of
LLNs [RFC6997]. The present applicability document provides point-to-point routes in LLNs. The present applicability document
recommendations and requirements for the accompanying parameter value provides recommendations and requirements for the accompanying
ranges. parameter value ranges.
A common set of security threats are described in [RFC7416]. The [RFC7416] describes a common set of security threats. The
applicability statements complement the security threats document by applicability statements provided in Section 4.1.8.2.2 of this
describing preferred security settings and solutions within the document complement [RFC7416] by describing preferred security
applicability statement conditions. This applicability statement settings and solutions within the applicability statement conditions.
recommends lighter weight security solutions appropriate for home and This applicability statement recommends lighter-weight security
building environments and indicates why these solutions are solutions appropriate for home and building environments and
appropriate. indicates why these solutions are appropriate.
1.2. Terminology 1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Additionally, this document uses terminology from [RFC6997], Additionally, this document uses terminology from [RFC6997],
[I-D.ietf-roll-trickle-mcast], [RFC7102], [IEEE802.15.4], and [RFC7731], [RFC7102], [IEEE802.15.4], and [RFC6550].
[RFC6550].
1.3. Required Reading 1.3. Required Reading
Applicable requirements are described in [RFC5826] and [RFC5867]. A Applicable requirements are described in [RFC5826] and [RFC5867]. A
survey of the application field is described in [BCsurvey]. survey of the application field is described in [BC-Survey].
1.4. Out of scope requirements 1.4. Requirements That Are Out of Scope
The considered network diameter is limited to a maximum diameter of The considered network diameter is limited to a maximum diameter of
10 hops and a typical diameter of 5 hops, which captures the most 10 hops and a typical diameter of five hops; this captures the most
common cases in home automation and building control networks. common cases in home automation and building control networks.
This document does not consider the applicability of Routing Protocol This document does not consider the applicability of RPL-related
for Low-Power and Lossy Networks (RPL)-related specifications for specifications for urban and industrial applications [RFC5548]
urban and industrial applications [RFC5548], [RFC5673], which may [RFC5673], which may exhibit significantly larger network diameters.
exhibit significantly larger network diameters.
2. Deployment Scenario 2. Deployment Scenario
The use of communications networks in buildings is essential to The use of communications networks in buildings is essential to
satisfy energy saving regulations. Environmental conditions of satisfy energy-saving regulations. Environmental conditions of
buildings can be adapted to suit the comfort of the individuals buildings can be adapted to suit the comfort of the individuals
present inside. Consequently when no one is present, energy present inside. Consequently, when no one is present, energy
consumption can be reduced. Cost is the main driving factor behind consumption can be reduced. Cost is the main driving factor behind
deployment of wireless networking in buildings, especially in the deployment of wireless networking in buildings, especially in the
case of retrofitting, where wireless connectivity saves costs case of retrofitting, where wireless connectivity saves costs
incurred due to cabling and building modifications. incurred due to cabling and building modifications.
A typical home automation network is comprised of less than 100 A typical home automation network is comprised of less than
nodes. Large building deployments may span 10,000 nodes but to 100 nodes. Large building deployments may span 10,000 nodes, but to
ensure uninterrupted service of light and air conditioning systems in ensure uninterrupted service of light and air conditioning systems in
individual zones of the building, nodes are typically organized in individual zones of the building, nodes are typically organized in
sub-networks. Each sub-network in a building automation deployment subnetworks. Each subnetwork in a building automation deployment
typically contains tens to hundreds of nodes, and for critical typically contains tens to hundreds of nodes and, for critical
operations may operate independently from the other sub-networks. operations, may operate independently from the other subnetworks.
The main purpose of the home or building automation network is to The main purpose of the home or building automation network is to
provide control over light and heating/cooling resources. User provide control over light and heating/cooling resources. User
intervention via wall controllers is combined with movement, light intervention via wall controllers is combined with movement, light
and temperature sensors to enable automatic adjustment of window and temperature sensors to enable automatic adjustment of window
blinds, reduction of room temperature, etc. In general, the sensors blinds, reduction of room temperature, etc. In general, the sensors
and actuators in a home or building typically have fixed physical and actuators in a home or building typically have fixed physical
locations and will remain in the same home or building automation locations and will remain in the same home or building automation
network. network.
People expect an immediate and reliable response to their presence or People expect an immediate and reliable response to their presence or
actions. For example, a light not switching on after entry into a actions. For example, a light not switching on after entry into a
room may lead to confusion and a profound dissatisfaction with the room may lead to confusion and a profound dissatisfaction with the
lighting product. lighting product.
Monitoring of functional correctness is at least as important as Monitoring of functional correctness is at least as important as
timely responses. Devices typically communicate their status timely responses. Devices typically communicate their status
regularly and send alarm messages notifying a malfunction of regularly and send alarm messages to notify users or implementers
controlled equipment or network. that a malfunction of controlled equipment or a controlled network
has occurred.
In building control, the infrastructure of the building management In building control, the infrastructure of the building management
network can be shared with the security/access, the Internet Protocol network can be shared with security/access, Internet Protocol (IP)
(IP) telephony, and the fire/alarm networks. This approach has a telephony, and fire/alarm networks. This approach has a positive
positive impact on the operation and cost of the network; however, impact on the operation and cost of the network; however, care should
care should be taken to ensure that the availability of the building be taken to ensure that the availability of the building management
management network does not become compromised beyond the ability for network does not become compromised beyond the ability of critical
critical functions to perform adequately. functions to perform adequately.
In homes, the entertainment network for audio/video streaming and In homes, the entertainment network for audio/video streaming and
gaming has different requirements, where the most important gaming has different requirements, where the most important
requirement is the need for high bandwidth not typically needed for requirement is the need for high bandwidth not typically needed for
home or building control. It is therefore expected that the home or building control. It is therefore expected that the
entertainment network in the home will mostly be separate from the entertainment network in the home will mostly be separate from the
control network, which also lessens the impact on availability of the control network, as this will also lessen the impact on the
control network availability of the control network.
2.1. Network Topologies 2.1. Network Topologies
In general, the home automation network or building control network In general, the home automation network or building control network
consists of wired and wireless sub-networks. In large buildings consists of wired and wireless subnetworks. In large buildings in
especially, the wireless sub-networks can be connected to an IP particular, the wireless subnetworks can be connected to an IP
backbone network where all infrastructure services are located, such backbone network where all infrastructure services (e.g., Domain Name
as Domain Name System (DNS), automation servers, etc. System (DNS), automation servers) are located.
The wireless sub-network can be configured according to any of the The wireless subnetwork can be configured according to any of the
following topologies: following topologies:
o A stand-alone network of 10-100 nodes without border router. This o A stand-alone network of 10-100 nodes without a border router.
typically occurs in the home with a stand-alone control network, This typically occurs in the home with a stand-alone control
in low cost buildings, and during installation of high end control network, in low-cost buildings, and during installation of
systems in buildings. high-end control systems in buildings.
o A connected network with one border router. This configuration o A connected network with one border router. This configuration
will happen in homes where home appliances are controlled from will happen in homes where home appliances are controlled from
outside the home, possibly via a smart phone, and in many building outside the home, possibly via a smart phone, and in many building
control scenarios. control scenarios.
o A connected network with multiple border routers. This will o A connected network with multiple border routers. This will
typically happen in installations of large buildings. typically happen in installations of large buildings.
Many of the nodes are battery-powered and may be sleeping nodes which Many of the nodes are battery powered and may be sleeping nodes that
wake up according to clock signals or external events. wake up according to clock signals or external events.
In a building control network, for a large installation with multiple In a building control network, for a large installation with multiple
border routers, sub-networks often overlap both geographically and border routers, subnetworks often overlap both geographically and
from a wireless coverage perspective. Due to two purposes of the from a wireless coverage perspective. Due to two purposes of the
network, (i) direct control and (ii) monitoring, there may exist two network -- (i) direct control and (ii) monitoring -- there may exist
types of routing topologies in a given sub-network: (i) a tree-shaped two types of routing topologies in a given subnetwork:
collection of routes spanning from a central building controller via (i) a tree-shaped collection of routes spanning from a central
the border router, on to destination nodes in the sub-network; and/or building controller via the border router, on to destination nodes in
(ii) a flat, un-directed collection of intra-network routes between the subnetwork, and (ii) a flat, undirected collection of
functionally related nodes in the sub-network. intra-network routes between functionally related nodes in the
subnetwork.
The majority of nodes in home and building automation networks are The majority of nodes in home and building automation networks are
typically class 0 devices [RFC7228], such as individual wall typically Class 0 devices [RFC7228], such as individual wall
switches. Only a few nodes (such as multi-purpose remote controls) switches. Only a few nodes (such as multi-purpose remote controls)
are more expensive Class 1 devices, which can afford more memory are more expensive Class 1 devices, which can afford more memory
capacity. capacity.
2.2. Traffic Characteristics 2.2. Traffic Characteristics
Traffic may enter the network originating from a central controller Traffic may enter the network originating from a central controller,
or it may originate from an intra-network node. The majority of or it may originate from an intra-network node. The majority of
traffic is light-weight point-to-point control style; e.g. Put-Ack traffic is of a lightweight point-to-point control style, e.g.,
or Get-Response. There are however exceptions. Bulk data transfer Put-Ack or Get-Response. There are, however, exceptions. Bulk data
is used for firmware update and logging, where firmware updates enter transfer is used for firmware updates and logging, where firmware
the network and logs leave the network. Group communication is used updates enter the network and logs leave the network. Group
for service discovery or to control groups of nodes, such as light communication is used for service discovery or to control groups of
fixtures. nodes, such as light fixtures.
Often, there is a direct physical relation between a controlling Often, there is a direct physical relationship between a controlling
sensor and the controlled equipment. For example the temperature sensor and the controlled equipment. For example, the temperature
sensor and room controller are located in the same room sharing the sensor and room controller are located in the same room, sharing the
same climate conditions. Consequently, the bulk of senders and same climate conditions. Consequently, the bulk of senders and
receivers are separated by a distance that allows one-hop direct path receivers are separated by a distance that allows one-hop direct path
communication. A graph of the communication will show several fully communication. A graph of the communication will show several fully
connected subsets of nodes. However, due to interference, multipath connected subsets of nodes. However, due to interference, multipath
fading, reflection and other transmission mechanisms, the one-hop fading, reflection, and other transmission mechanisms, the one-hop
direct path may be temporally disconnected. For reliability direct path may be temporarily disconnected. For reliability
purposes, it is therefore essential that alternative n-hop purposes, it is therefore essential that alternative n-hop
communication routes exist for quick error recovery. (See Appendix B communication routes exist for quick error recovery. (See Appendix B
for motivation.) for motivation.)
Looking over time periods of a day, the networks are very lightly Looking over time periods of a day, the networks are very lightly
loaded. However, bursts of traffic can be generated by e.g. loaded. However, bursts of traffic can be generated by, for example,
incessant pushing of the button of a remote control, the occurrence incessant pushing of the button of a remote control, the occurrence
of a defect, and other unforeseen events. Under those conditions, of a defect, and other unforeseen events. Under those conditions,
the timeliness must nevertheless be maintained. Therefore, measures the timeliness must nevertheless be maintained. Therefore, measures
are necessary to remove any unnecessary traffic. Short routes are are necessary to remove any unnecessary traffic. Short routes are
preferred. Long multi-hop routes via the border router, should be preferred. Long multi-hop routes via the border router should be
avoided whenever possible. avoided whenever possible.
Group communication is essential for lighting control. For example, Group communication is essential for lighting control. For example,
once the presence of a person is detected in a given room, lighting once the presence of a person is detected in a given room, lighting
control applies to that room only and no other lights should be control applies to that room only, and no other lights should be
dimmed, or switched on/off. In many cases, this means that a dimmed or switched on/off. In many cases, this means that a
multicast message with a 1-hop and 2-hop radius would suffice to multicast message with a one-hop and two-hop radius would suffice to
control the required lights. The same argument holds for Heating, control the required lights. The same argument holds for Heating,
Ventilating, and Air Conditioning (HVAC) and other climate control Ventilating, and Air Conditioning (HVAC) and other climate-control
devices. To reduce network load, it is advisable that messages to devices. To reduce network load, it is advisable that messages to
the lights in a room are not distributed any further in the mesh than the lights in a room are not distributed any further in the mesh than
necessary based on intended receivers. necessary, based on intended receivers.
An example of an office surface is shown in [office-light], and the [Office-Light] provides an example of an office space, and
current use of wireless lighting control products is shown in [OccuSwitch] describes the current use of wireless lighting control
[occuswitch]. products.
2.2.1. General 2.2.1. General
Whilst air conditioning and other environmental-control applications Although air conditioning and other environmental-control
may accept response delays of tens of seconds or longer, alarm and applications may accept response delays of tens of seconds or longer,
light control applications may be regarded as soft real-time systems. alarm and light control applications may be regarded as soft
A slight delay is acceptable, but the perceived quality of service real-time systems. A slight delay is acceptable, but the perceived
degrades significantly if response times exceed 250 ms. If the light quality of service degrades significantly if response times exceed
does not turn on at short notice, a user may activate the controls 250 ms. If the light does not turn on at short notice, a user may
again, thus causing a sequence of commands such as activate the controls again, thus causing a sequence of commands such
Light{on,off,on,off,..} or Volume{up,up,up,up,up,...}. In addition as Light{on,off,on,off,...} or Volume{up,up,up,up,up,...}. In
the repetitive sending of commands creates an unnecessary loading of addition, the repetitive sending of commands creates an unnecessary
the network, which in turn increases the bad responsiveness of the loading of the network, which in turn increases the poor
network. responsiveness of the network.
2.2.2. Source-sink (SS) communication paradigm 2.2.2. Source-Sink (SS) Communication Paradigm
This paradigm translates to many sources sending messages to the same This paradigm translates to many sources sending messages to the same
sink, sometimes reachable via the border router. As such, source- sink, sometimes reachable via the border router. As such,
sink (SS) traffic can be present in home and building networks. The Source-Sink (SS) traffic can be present in home and building
traffic may be generated by environmental sensors (often present in a networks. The traffic may be generated by environmental sensors
wireless sub-network) which push periodic readings to a central (often present in a wireless subnetwork) that push periodic readings
server. The readings may be used for pure logging, or more often, to a central server. The readings may be used for pure logging or,
processed to adjust light, heating and ventilation. Alarm sensors more often, processed to adjust light, heating, and ventilation.
may also generate SS style traffic. The central server in a home Alarm sensors may also generate SS-style traffic. The central server
automation network will be connected mostly to a wired network in a home automation network will be connected mostly to a wired
segment of the home network, although it is likely that cloud network segment of the home network, although it is likely that cloud
services will also be used. The central server in a building services will also be used. The central server in a building
automation network may be connected to a backbone or be placed automation network may be connected to a backbone or placed outside
outside the building. the building.
With regards to message latency, most SS transmissions can tolerate With regard to message latency, most SS transmissions can tolerate
worst-case delays measured in tens of seconds. Fire detectors, worst-case delays measured in tens of seconds. Fire detectors,
however, represent an exception; For example, special provisions with however, represent an exception; for example, special provisions with
respect to the location of the Fire detectors and the smoke dampers respect to the location of the fire detectors and smoke dampers need
need to be put in place to meet the stringent delay requirements to be put in place to meet stringent delay requirements that are
measured in seconds. measured in seconds.
2.2.3. Publish-subscribe (PS, or pub/sub)) communication paradigm 2.2.3. Publish-Subscribe (PS, or Pub/Sub) Communication Paradigm
This paradigm translates to a number of devices expressing their This paradigm translates to a number of devices expressing their
interest for a service provided by a server device. For example, a interest in a service provided by a server device. For example, a
server device can be a sensor delivering temperature readings on the server device can be a sensor delivering temperature readings on the
basis of delivery criteria, like changes in acquisition value or age basis of delivery criteria, like changes in acquisition value or age
of the latest acquisition. In building automation networks, this of the latest acquisition. In building automation networks, this
paradigm may be closely related to the SS paradigm given that paradigm may be closely related to the SS paradigm, given that
servers, which are connected to the backbone or outside the building, servers, which are connected to the backbone or outside the building,
can subscribe to data collectors that are present at strategic places can subscribe to data collectors that are present at strategic places
in the building automation network. The use of PS will probably in the building automation network. The use of PS will probably
differ significantly from installation to installation. differ significantly from installation to installation.
2.2.4. Peer-to-peer (P2P) communication paradigm 2.2.4. Peer-to-Peer (P2P) Communication Paradigm
This paradigm translates to a device transferring data to another This paradigm translates to a device transferring data to another
device often connected to the same sub-network. Peer-to-peer (P2P) device often connected to the same subnetwork. Peer-to-Peer (P2P)
traffic is a common traffic type in home automation networks. Most traffic is a common traffic type in home automation networks. Most
building automation networks rely on P2P traffic, described in the building automation networks rely on P2P traffic as described in the
next paragraph. Other building automation networks rely on P2P next paragraph. Other building automation networks rely on P2P
control traffic between controls and a local controller box for control traffic between controls and a local controller box for
advanced group control. A local controller box can be further advanced group control. A local controller box can be further
connected to service control boxes, thus generating more SS or PS connected to service control boxes, thus generating more SS or PS
traffic. traffic.
P2P traffic is typically generated by remote controls and wall P2P traffic is typically generated by remote controls and wall
controllers which push control messages directly to light or heat controllers that push Control Messages directly to light or heat
sources. P2P traffic has a stringent requirement for low latency sources. P2P traffic has a stringent requirement for low latency,
since P2P traffic often carries application messages that are invoked since P2P traffic often carries application messages that are invoked
by humans. As mentioned in Section 2.2.1, application messages by humans. As mentioned in Section 2.2.1, application messages
should be delivered within a few hundred milliseconds - even when should be delivered within a few hundred milliseconds, even when
connections fail momentarily. connections fail momentarily.
2.2.5. Peer-to-multipeer (P2MP) communication paradigm 2.2.5. Peer-to-Multipeer (P2MP) Communication Paradigm
This paradigm translates to a device sending a message as many times This paradigm translates to a device sending a message as many times
as there are destination devices. Peer-to-multipeer (P2MP) traffic as there are destination devices. Peer-to-Multipeer (P2MP) traffic
is common in home and building automation networks. Often, a is common in home and building automation networks. Often, a
thermostat in a living room responds to temperature changes by thermostat in a living room responds to temperature changes by
sending temperature acquisitions to several fans and valves sending temperature acquisitions to several fans and valves
consecutively. This paradigm is also closely related to the PS consecutively. This paradigm is also closely related to the PS
paradigm in the case where a single server device has multiple paradigm in the case where a single server device has multiple
subscribers. subscribers.
2.2.6. Additional considerations: Duocast and N-cast 2.2.6. Additional Considerations: Duocast and N-Cast
This paradigm translates to a device sending a message to many This paradigm translates to a device sending a message to many
destinations in one network transfer invocation. Multicast is well- destinations in one network transfer invocation. Multicast is well
suited for lighting where a presence sensor sends a presence message suited for lighting where a presence sensor sends a presence message
to a set of lighting devices. Multicast increases the probability to a set of lighting devices. Multicast increases the probability
that the message is delivered within the strict time constraints. that the message is delivered within strict time constraints. The
The recommended multicast algorithm (e.g. recommended multicast algorithm (e.g., [RFC7731]) provides a
[I-D.ietf-roll-trickle-mcast]) provides a mechanism for delivering mechanism for delivering messages to all intended destinations.
messages to all intended destinations.
2.2.7. RPL applicability per communication paradigm 2.2.7. RPL Applicability per Communication Paradigm
In the case of the SS paradigm applied to a wireless sub-network to a In the case of the SS paradigm applied to a wireless subnetwork to a
server reachable via a border router, the use of RPL [RFC6550] in server reachable via a border router, the use of RPL [RFC6550] in
non-storing mode is appropriate. Given the low resources of the non-storing mode is appropriate. Given the low resources of the
devices, source routing will be used from the border router to the devices, source routing will be used from the border router to the
destination in the wireless sub-network for messages generated destination in the wireless subnetwork for messages generated outside
outside the mesh network. No specific timing constraints are the mesh network. No specific timing constraints are associated with
associated with the SS type messages so network repair does not the SS-type messages, so network repair does not violate the
violate the operational constraints. When no SS traffic takes place, operational constraints. When no SS traffic takes place, it is good
it is good practice to load only RPL code enabling P2P mode of practice to load only RPL code that enables the P2P mode of operation
operation [RFC6997] to reduce the code size and satisfy memory [RFC6997] to reduce the code size and satisfy memory requirements.
requirements.
P2P-RPL [RFC6997] is required for all P2P and P2MP traffic taking To assure responsiveness, P2P-RPL [RFC6997] is required for all P2P
place between nodes within a wireless sub-network (excluding the and P2MP traffic taking place between nodes within a wireless
border router) to assure responsiveness. Source and destination subnetwork (excluding the border router). Source and destination
devices are typically physically close based on room layout. devices are typically physically close, based on room layout.
Consequently, most P2P and P2MP traffic is 1-hop or 2-hop traffic. Consequently, most P2P and P2MP traffic is one-hop or two-hop
Appendix A explains why P2P-RPL is preferable to RPL for this type of traffic. Appendix A identifies shortcomings of using RPL for this
communication. Appendix B explains why reliability measures such as type of communication; these shortcomings are counteracted through
multi-path routing are necessary even when 1-hop communication the use of P2P-RPL. Appendix B explains why reliability measures
dominates. such as multipath routing are necessary even when one-hop
communication dominates.
Additional advantages of P2P-RPL for home and building automation Examples of additional advantages of P2P-RPL for home and building
networks are, for example: automation networks are as follows:
o Individual wall switches are typically inexpensive class 0 devices o Individual wall switches are typically inexpensive Class 0 devices
[RFC7228] with extremely low memory capacities. Multi-purpose [RFC7228] with extremely low memory capacities. Multi-purpose
remote controls for use in a home environment typically have more remote controls for use in a home environment typically have more
memory but such devices are asleep when there is no user activity. memory, but such devices are asleep when there is no user
P2P-RPL reactive discovery allows a node to wake up and find new activity. P2P-RPL reactive discovery allows a node to wake up and
routes within a few seconds while memory constrained nodes only find new routes within a few seconds, while memory-constrained
have to keep routes to relevant targets. nodes only have to keep routes to relevant targets.
o The reactive discovery features of P2P-RPL ensure that commands o The reactive discovery features of P2P-RPL ensure that commands
are normally delivered within the 250 ms time window. When are normally delivered within the 250 ms time window. When
connectivity needs to be restored, discovery is typically connectivity needs to be restored, discovery is typically
completed within seconds. In most cases, an alternative (earlier completed within seconds. In most cases, an alternative route (a
discovered) route will work and route rediscovery is not route that was discovered earlier) will work and route rediscovery
necessary. is not necessary.
o Broadcast storms typically associated with route discovery for Ad o Broadcast storms typically associated with route discovery for the
hoc On-Demand Distance Vector (AODV) [RFC3561] are less disruptive Ad hoc On-Demand Distance Vector (AODV) [RFC3561] are less
for P2P-RPL. P2P-RPL has a "STOP" bit which is set by the target disruptive for P2P-RPL. P2P-RPL has a "Stop" bit, which is set by
of a route discovery to notify all other nodes that no more the target of a route discovery to notify all other nodes that no
Directed Acyclic Graph (DAG) Information Option (DIO) messages more Destination-Oriented Directed Acyclic Graph (DODAG)
should be forwarded for this temporary DAG. Something looking Information Object (DIO) messages should be forwarded for this
like a broadcast storm may happen when no target is responding temporary DAG. Something that looks like a broadcast storm may
however, in this case, the Trickle suppression mechanism kicks in, happen when no target is responding; however, in this case, the
limiting the number of DIO forwards in dense networks. Trickle suppression mechanism kicks in, limiting the number of DIO
forwards in dense networks.
Due to the limited memory of the majority of devices, P2P-RPL SHOULD Due to the limited memory of the majority of devices, P2P-RPL SHOULD
be deployed with source routing in non-storing mode as explained in be deployed with source routing in non-storing mode, as explained in
Section 4.1.2. Section 4.1.2.
Multicast with Multicast Protocol for Low power and Lossy Networks Multicast with the Multicast Protocol for Low-Power and Lossy
(MPL) [I-D.ietf-roll-trickle-mcast] is preferably deployed for N-cast Networks (MPL) [RFC7731] is preferably deployed for N-cast over the
over the wireless network. Configuration constraints that are wireless network. Configuration constraints that are necessary to
necessary to meet reliability and timeliness with MPL are discussed meet reliability and timeliness with MPL are discussed in
in Section 4.1.7. Section 4.1.7.
2.3. Layer-2 applicability 2.3. Layer 2 Applicability
This document applies to [IEEE802.15.4] and [G.9959] which are This document applies to [IEEE802.15.4] and [G.9959], which are
adapted to IPv6 by the adaption layers [RFC4944] and [RFC7428]. adapted to IPv6 by the adaptation layers [RFC4944] and [RFC7428].
Other layer-2 technologies, accompanied by an "IP over Foo" Other Layer 2 technologies, accompanied by an "IP-over-Foo"
specification, are also relevant provided there is no frame size specification, are also relevant, provided there is no frame size
issue, and there are link layer acknowledgements. issue and there are link-layer acknowledgements.
The above mentioned adaptation layers leverage on the compression The above-mentioned adaptation layers leverage on the compression
capabilities of [RFC6554] and [RFC6282]. Header compression allows capabilities of [RFC6554] and [RFC6282]. Header compression allows
small IP packets to fit into a single layer 2 frame even when source small IP packets to fit into a single Layer 2 frame, even when source
routing is used. A network diameter limited to 5 hops helps to routing is used. A network diameter limited to five hops helps to
achieve this even while using source routing. achieve this, even while using source routing.
Dropped packets are often experienced in the targeted environments. Dropped packets are often experienced in the targeted environments.
Internet Control Message Protocol (ICMP), User Datagram Protocol Internet Control Message Protocol (ICMP), User Datagram Protocol
(UDP) and even Transmission Control Protocol (TCP) flows may benefit (UDP), and even Transmission Control Protocol (TCP) flows may benefit
from link layer unicast acknowledgments and retransmissions. Link from link-layer unicast acknowledgements and retransmissions.
layer unicast acknowledgments SHOULD be enabled when [IEEE802.15.4] Link-layer unicast acknowledgements SHOULD be enabled when
or [G.9959] is used with RPL and P2P-RPL. [IEEE802.15.4] or [G.9959] is used with RPL and P2P-RPL.
3. Using RPL to meet Functional Requirements 3. Using RPL to Meet Functional Requirements
Several features required by [RFC5826], [RFC5867] challenge the P2P Several features required by [RFC5826] and [RFC5867] challenge the
paths provided by RPL. Appendix A reviews these challenges. In some P2P paths provided by RPL. Appendix A reviews these challenges. In
cases, a node may need to spontaneously initiate the discovery of a some cases, a node may need to spontaneously initiate the discovery
path towards a desired destination that is neither the root of a DAG, of a path towards a desired destination that is neither the root of a
nor a destination originating Destination Advertisement Object (DAO) DAG nor a destination originating Destination Advertisement Object
signalling. Furthermore, P2P paths provided by RPL are not (DAO) signaling. Furthermore, P2P paths provided by RPL are not
satisfactory in all cases because they involve too many intermediate satisfactory in all cases because they involve too many intermediate
nodes before reaching the destination. nodes before reaching the destination.
P2P-RPL [RFC6997] SHOULD be used in home automation and building P2P-RPL [RFC6997] SHOULD be used in home automation and building
control networks, as point-to-point style traffic is substantial and control networks, as traffic of a point-to-point style is substantial
route repair needs to be completed within seconds. P2P-RPL provides and route repair needs to be completed within seconds. P2P-RPL
a reactive mechanism for quick, efficient and root-independent route provides a reactive mechanism for quick, efficient, and root-
discovery/repair. The use of P2P-RPL furthermore allows data traffic independent route discovery/repair. The use of P2P-RPL furthermore
to avoid having to go through a central region around the root of the allows data traffic to avoid having to go through a central region
tree, and drastically reduces path length [SOFT11] [INTEROP12]. around the root of the tree and drastically reduces path length
These characteristics are desirable in home and building automation [SOFT11] [INTEROP12]. These characteristics are desirable in home
networks because they substantially decrease unnecessary network and building automation networks because they substantially decrease
congestion around the root of the tree. unnecessary network congestion around the root of the tree.
When more reliability is required, P2P-RPL enables the establishment When more reliability is required, P2P-RPL enables the establishment
of multiple independent paths. For 1-hop destinations this means of multiple independent paths. For one-hop destinations, this means
that one 1-hop communication and a second 2-hop communication take that one one-hop communication and a second two-hop communication
place via a neighbouring node. Such a pair of redundant take place via a neighboring node. Such a pair of redundant
communication paths can be achieved by using MPL where the source is communication paths can be achieved by using MPL, where the source is
a MPL forwarder, while a second MPL forwarder is 1 hop away from both an MPL Forwarder while a second MPL Forwarder is one hop away from
the source and the destination node. When the source multicasts the both the source and the destination node. When the source multicasts
message, it may be received by both the destination and the 2nd the message, it may be received by both the destination and the
forwarder. The 2nd forwarder forwards the message to the second MPL Forwarder. The second MPL Forwarder forwards the message
destination, thus providing two routes from sender to destination. to the destination, thus providing two routes from sender to
destination.
To provide more reliability with multiple paths, P2P-RPL can maintain To provide more reliability with multiple paths, P2P-RPL can maintain
two independent P2P source routes per destination, at the source. two independent P2P source routes per destination, at the source.
Good practice is to use the paths alternately to assess their Good practice is to use the paths alternately to assess their
existence. When one P2P path has failed (possibly only temporarily), existence. When one P2P path has failed (possibly only temporarily),
as described in Appendix B, the alternative P2P path can be used as described in Appendix B, the alternative P2P path can be used
without discarding the failed path. The failed P2P path, unless without discarding the failed path. The failed P2P path, unless
proven to work again, can be safely discarded after a timeout proven to work again, can be safely discarded after a timeout
(typically 15 minutes). A new route discovery is done when the (typically 15 minutes). A new route discovery is done when the
number of P2P paths is exhausted due to persistent link failures. number of P2P paths is exhausted due to persistent link failures.
4. RPL Profile 4. RPL Profile
P2P-RPL SHOULD be used in home automation and building control P2P-RPL SHOULD be used in home automation and building control
networks. Its reactive discovery allows for low application response networks. Its reactive discovery allows for low application response
times even when on-the-fly route repair is needed. Non-storing mode times, even when on-the-fly route repair is needed. Non-storing mode
SHOULD be used to reduce memory consumption in repeaters with SHOULD be used to reduce memory consumption in repeaters with
constrained memory when source routing is used. constrained memory when source routing is used.
4.1. RPL Features 4.1. RPL Features
An important constraint on the application of RPL is the presence of An important constraint on the application of RPL is the presence of
sleeping nodes. sleeping nodes.
For example, in a stand-alone network, the master node (or For example, in a stand-alone network, the master node (or
coordinator) providing the logical layer-2 identifier and unique node coordinator) providing the logical Layer 2 identifier and unique node
identifiers to connected nodes may be a remote control which returns identifiers to connected nodes may be a remote control that returns
to sleep once new nodes have been added. Due to the absence of the to sleep once new nodes have been added. Due to the absence of the
border router, there may be no global routable prefixes at all. border router, there may be no global routable prefixes at all.
Likewise, there may be no authoritative always-on root node since Likewise, there may be no authoritative always-on root node, since
there is no border router to host this function. there is no border router to host this function.
In a network with a border router and many sleeping nodes, there may In a network with a border router and many sleeping nodes, there may
be battery powered sensors and wall controllers configured to contact be battery-powered sensors and wall controllers configured to contact
other nodes in response to events and then return to sleep. Such other nodes in response to events and then return to sleep. Such
nodes may never detect the announcement of new prefixes via nodes may never detect the announcement of new prefixes via
multicast. multicast.
In each of the above mentioned constrained deployments, a link layer In each of the above-mentioned constrained deployments, a link-layer
node (e.g. coordinator or master) SHOULD assume the role of node (e.g., coordinator or master) SHOULD assume the role of an
authoritative root node, transmitting unicast Router Advertisement authoritative root node, transmitting unicast Router Advertisement
(RA) messages with a Unique Local Address (ULA) prefix information (RA) messages with a Unique Local Address (ULA) prefix information
option to nodes during the joining process to prepare the nodes for a option to nodes during the joining process to prepare the nodes for a
later operational phase, where a border router is added. later operational phase, where a border router is added.
A border router SHOULD be designed to be aware of sleeping nodes in A border router SHOULD be designed to be aware of sleeping nodes in
order to support the distribution of updated global prefixes to such order to support the distribution of updated global prefixes to such
sleeping nodes. sleeping nodes.
4.1.1. RPL Instances 4.1.1. RPL Instances
When operating P2P-RPL on a stand-alone basis, there is no When operating P2P-RPL on a stand-alone basis, there is no
authoritative root node maintaining a permanent RPL Direction- authoritative root node maintaining a permanent RPL DODAG. A node
Oriented Directed Acyclic Graph (DODAG). A node MUST be able to join MUST be able to join at least one RPL Instance, as a new, temporary
at least one RPL instance, as a new, temporary instance is created instance is created during each P2P-RPL route discovery operation. A
during each P2P-RPL route discovery operation. A node MAY be node MAY be designed to join multiple RPL Instances.
designed to join multiple RPL instances.
4.1.2. Storing vs. Non-Storing Mode 4.1.2. Storing vs. Non-Storing Mode
Non-storing mode MUST be used to cope with the extremely constrained Non-storing mode MUST be used to cope with the extremely constrained
memory of a majority of nodes in the network (such as individual memory of a majority of nodes in the network (such as individual
light switches). light switches).
4.1.3. DAO Policy 4.1.3. DAO Policy
Nodes send DAO messages to establish downward paths from the root to Nodes send DAO messages to establish downward paths from the root to
themselves. DAO messages are not acknowledged in networks composed themselves. In order to minimize the power consumption overhead
of battery operated field devices in order to minimize the power associated with path discovery, DAO messages are not acknowledged in
consumption overhead associated with path discovery. The DAO networks composed of battery-operated field devices. The DAO
messages build up a source route because the nodes MUST be in non- messages build up a source route because the nodes MUST be in
storing mode. non-storing mode.
If devices in LLNs participate in multiple RPL instances and DODAGs, If devices in LLNs participate in multiple RPL Instances and DODAGs,
both the RPLInstance ID and the DODAGID SHOULD be included in the both the RPLInstance ID and the DODAGID SHOULD be included in
DAO. the DAO.
4.1.4. Path Metrics 4.1.4. Path Metrics
Expected Transmission Count (ETX) is the RECOMMENDED metric. Expected Transmission Count (ETX) is the RECOMMENDED metric.
[RFC6551] provides other options. [RFC6551] provides other options.
Packets from asymmetric and/or unstable links SHOULD be deleted at Packets from asymmetric and/or unstable links SHOULD be deleted at
layer 2. Layer 2.
4.1.5. Objective Function 4.1.5. Objective Function
Objective Function 0 (OF0) MUST be the Objective Function. Other Objective Function Zero (OF0) [RFC6552] MUST be the Objective
Objective Functions MAY be used when dictated by circumstances. Function. Other Objective Functions MAY be used when dictated by
circumstances.
4.1.6. DODAG Repair 4.1.6. DODAG Repair
Since P2P-RPL only creates DODAGs on a temporary basis during route Since P2P-RPL only creates DODAGs on a temporary basis during route
repair or route discovery, there is no need to repair DODAGs. repair or route discovery, there is no need to repair DODAGs.
For SS traffic, local repair is sufficient. The accompanying process For SS traffic, local repair is sufficient. The accompanying process
is known as poisoning and is described in Section 8.2.2.5 of is known as "poisoning" and is described in Section 8.2.2.5 of
[RFC6550]. Given that the majority of nodes in the building do not [RFC6550]. Given that the majority of nodes in the building do not
physically move around, creating new DODAGs should not happen physically move around, creating new DODAGs should not happen
frequently. frequently.
4.1.7. Multicast 4.1.7. Multicast
Commercial lighting deployments may have a need for multicast to Commercial lighting deployments may have a need for multicast to
distribute commands to a group of lights in a timely fashion. distribute commands to a group of lights in a timely fashion.
Several mechanisms exist for achieving such functionality; Several mechanisms exist for achieving such functionality; [RFC7731]
[I-D.ietf-roll-trickle-mcast] is the RECOMMENDED protocol for home is the RECOMMENDED protocol for home and building deployments. This
and building deployments. This section relies heavily on the section relies heavily on the conclusions of [RT-MPL].
conclusions of [RT-MPL].
At reception of a packet, the MPL forwarder starts a series of At reception of a packet, the MPL Forwarder starts a series of
consecutive trickle timer intervals, where the first interval has a consecutive Trickle timer intervals, where the first interval has a
minimum size of Imin. Each consecutive interval is twice as long as minimum size of Imin. Each consecutive interval is twice as long as
the former with a maximum value of Imax. There is a maximum number the former, with a maximum value of Imax. There is a maximum number
of intervals given by max_expiration. For each interval of length I, of intervals given by max_expiration. For each interval of length I,
a time t is randomly chosen in the period [I/2, I]. For a given a time t is randomly chosen in the period [I/2, I]. For a given
packet, p, MPL counts the number of times it receives p during the packet, p, MPL counts the number of times it receives p during the
period [0, t] in a counter c. At time t, MPL re-broadcasts p when c period [0, t] in a counter c. At time t, MPL rebroadcasts p when
< k, where k is a predefined constant with a value k > 0. c < k, where k is a predefined constant with a value k > 0.
The density of forwarders and the frequency of message generation are The density of forwarders and the frequency of message generation are
important aspects to obtain timeliness during control operations. A important aspects to obtain timeliness during control operations.
high frequency of message generation can be expected when a remote A high frequency of message generation can be expected when a
control button is incessantly pressed, or when alarm situations remote-control button is incessantly pressed or when alarm situations
arise. arise.
Guaranteeing timeliness is intimately related to the density of the Guaranteeing timeliness is intimately related to the density of the
MPL routers. In ideal circumstances the message is propagated as a MPL routers. In ideal circumstances, the message is propagated as a
single wave through the network, such that the maximum delay is single wave through the network, such that the maximum delay is
related to the number of hops times the smallest repetition interval related to the number of hops times the smallest repetition interval
of MPL. Each forwarder that receives the message passes the message of MPL. Each forwarder that receives the message passes the message
on to the next hop by repeating the message. When several copies of on to the next hop by repeating the message. When several copies of
a message reach the forwarder, it is specified that the copy need not a message reach the forwarder, it is specified that the copy need not
be repeated. Repetition of the message can be inhibited by a small be repeated. Repetition of the message can be inhibited by a small
value of k. To assure timeliness, the value of k should be chosen value of k. To assure timeliness, the chosen value of k should be
high enough to make sure that messages are repeated at the first high enough to make sure that messages are repeated at the first
arrival of the message in the forwarder. However, a network that is arrival of the message in the forwarder. However, a network that is
too dense leads to a saturation of the medium that can only be too dense leads to a saturation of the medium that can only be
prevented by selecting a low value of k. Consequently, timeliness is prevented by selecting a low value of k. Consequently, timeliness is
assured by choosing a relatively high value of k but assuring at the assured by choosing a relatively high value of k but assuring at the
same time a low enough density of forwarders to reduce the risk of same time a low enough density of forwarders to reduce the risk of
medium saturation. Depending on the reliability of the network medium saturation. Depending on the reliability of the network
links, it is advisable to choose the network such that at least 2 links, it is advisable to configure the density of the network such
forwarders per hop repeat messages to the same set of destinations. that at least two forwarders per hop repeat messages to the same set
of destinations.
There are no rules about selecting forwarders for MPL. In buildings There are no rules about selecting forwarders for MPL. In buildings
with central management tools, the forwarders can be selected, but in with central management tools, the forwarders can be selected, but at
the home is not possible to automatically configure the forwarder the time of this writing it is not possible to automatically
topology at the time of writing this document. configure the forwarder topology in the home.
4.1.8. Security 4.1.8. Security
RPL MAY use unsecured RPL messages to reduce message size. If there RPL MAY use unsecured RPL messages to reduce message size. If there
is a single node that uses unsecured RPL messages, link-layer is a single node that uses unsecured RPL messages, link-layer
security MUST be used on all nodes. Therefore all RPL messages MUST security MUST be used on all nodes. Therefore, all RPL messages MUST
be secured using either: be secured using:
o RPL message security, or o RPL message security, or
o Link-layer security, or o Link-layer security, or
o Both RPL message security and link-layer security o Both RPL message security and link-layer security
A symmetric key is used to secure a RPL message using either RPL A symmetric key is used to secure a RPL message using either RPL
message security or link-layer security. The symmetric key MUST be message security or link-layer security. The symmetric key MUST be
distributed or established in a secure fashion. There may be more distributed or established in a secure fashion. There may be more
than one symmetric key in use by any node at any one time. The same than one symmetric key in use by any node at any one time. The same
symmetric key MUST NOT be used for both RPL message security and symmetric key MUST NOT be used for both RPL message security and
link-layer security between two peer nodes. link-layer security between two peer nodes.
4.1.8.1. Symmetric key distribution 4.1.8.1. Symmetric Key Distribution
The scope of symmetric key distribution MUST be no greater than the The scope of symmetric key distribution MUST be no greater than the
network itself, i.e. a group key. This document describes what needs network itself, i.e., a group key. This document describes what
to be implemented to meet this requirement. The scope of symmetric needs to be implemented to meet this requirement. The scope of
key distribution MAY be smaller than the network, for example: symmetric key distribution MAY be smaller than the network -- for
example:
o A pairwise symmetric key between two peers. o A pairwise symmetric key between two peers.
o A group key shared between a subset of nodes in the network. o A group key shared between a subset of nodes in the network.
4.1.8.2. Symmetric key distribution mechanism 4.1.8.2. Symmetric Key Distribution Mechanism
The authentication mechanism as described in Section 6.9 of The authentication mechanism as described in Section 6.9 of
[ZigBeeIP] SHALL be used to securely distribute a network-wide [ZigBeeIP] SHALL be used to securely distribute a network-wide
symmetric key. symmetric key.
The purpose of the authentication procedure is to provide mutual The purpose of the authentication procedure is to provide mutual
authentication resulting in: authentication resulting in:
o Preventing untrusted nodes without appropriate credentials from o Preventing untrusted nodes without appropriate credentials from
joining the trusted network. joining the trusted network.
o Preventing trusted nodes with appropriate credentials from joining o Preventing trusted nodes with appropriate credentials from joining
an untrusted network. an untrusted network.
There is an Authentication Server, which is responsible for There is an Authentication Server, which is responsible for
authenticating the nodes on the network. If the authentication is authenticating the nodes on the network. If the authentication is
successful, the Authentication Server sends the network security successful, the Authentication Server sends the network security
material to the joining node through the PANA protocol ([RFC5191], material to the joining node through the Protocol for Carrying
[RFC6345]). The joining node becomes a full participating node in Authentication for Network Access (PANA) [RFC5191] [RFC6345]. The
the network and is able to apply layer 2 security to RPL messages joining node becomes a full participating node in the network and is
using the distributed network key. able to apply Layer 2 security to RPL messages using the distributed
network key.
The joining node does not initially have access to the network The joining node does not initially have access to the network
security material. Therefore, it is not able to apply layer 2 security material. Therefore, it is not able to apply Layer 2
security for the packets exchanged during the authentication process. security to the packets exchanged during the authentication process.
The enforcement point rules at the edge of the network ensure that The enforcement point rules at the edge of the network ensure that
the packets involved in the PANA authentication are processed even the packets involved in PANA authentication are processed even though
though they are unsecured at MAC layer. The rules also ensure that they are unsecured at the Medium Access Control (MAC) layer. The
any other incoming traffic that is not secured at the MAC layer is rules also ensure that any other incoming traffic that is not secured
discarded and is not forwarded. at the MAC layer is discarded and is not forwarded.
4.1.8.2.1. Authentication Stack 4.1.8.2.1. Authentication Stack
Authentication can be viewed as a protocol stack as a layer Authentication can be viewed as a protocol stack as a layer
encapsulates the layers above it. encapsulates the layers above it.
o TLS [RFC5246] MUST be used at the highest layer of the o Transport Layer Security (TLS) [RFC5246] MUST be used at the
authentication stack and carries the authentication exchange. highest layer of the authentication stack and carries the
There is one cipher suite based on pre-shared key [RFC6655] and authentication exchange. There is one cipher suite based on a
one cipher suite based on ECC [RFC7251]. Pre-Shared Key (PSK) [RFC6655] and one cipher suite based on
Elliptic Curve Cryptography (ECC) [RFC7251].
o EAP-TLS [RFC5216] MUST be used at the next layer to carry the TLS o Extensible Authentication Protocol-TLS (EAP-TLS) [RFC5216] MUST be
records for the authentication protocol. used at the next layer to carry the TLS records for the
authentication protocol.
o The Extensible Authentication Protocol [RFC3748] MUST be used to o EAP [RFC3748] MUST be used to provide the mechanisms for mutual
provide the mechanisms for mutual authentication. EAP requires a authentication. EAP requires a way to transport EAP packets
way to transport EAP packets between the joining node and the node between the joining node and the node on which the Authentication
on which the Authentication Server resides. These nodes are not Server resides. These nodes are not necessarily in radio range of
necessarily in radio range of each other, so it is necessary to each other, so it is necessary to have multi-hop support in the
have multi-hop support in the EAP transport method. The PANA EAP transport method. PANA [RFC5191] [RFC6345], which operates
protocol [RFC5191], [RFC6345], which operates over UDP, MUST be over UDP, MUST be used for this purpose. [RFC3748] specifies the
used for this purpose. [RFC3748] specifies the derivation of a derivation of a session key using the EAP key hierarchy; only the
session key using the EAP key hierarchy; only the EAP Master EAP Master Session Key shall be derived, as [RFC5191] specifies
Session Key shall be derived, as [RFC5191] specifies that it is that it is used to set up keys for PANA authentication and
used to set up keys for PANA authentication and encryption. encryption.
o PANA [RFC5191] and PANA relay [RFC6345] MUST be used at the next o PANA [RFC5191] and a PANA relay [RFC6345] MUST be used at the next
layer: layer:
* The joining node MUST act as the PANA Client (PaC) * The joining node MUST act as the PANA Client (PaC).
* The parent edge router node MUST act as a PANA relay (PRE) * The parent edge router node MUST act as a PANA Relay Element
according to [RFC6345], unless it is also the Authentication (PRE) according to [RFC6345], unless it is also the
Server. All routers at the edge of the network MUST be capable Authentication Server. All routers at the edge of the network
of functioning in the PRE role. MUST be capable of functioning in the PRE role.
* The Authentication Server node MUST act as the PANA * The Authentication Server node MUST act as the PANA
Authentication Agent (PAA). The Authentication Server MUST be Authentication Agent (PAA). The Authentication Server MUST be
able to handle packets relayed according to [RFC6345]. able to handle packets relayed according to [RFC6345].
This network authentication process uses link-local IPv6 addresses This network authentication process uses link-local IPv6 addresses
for transport between the new node and its parent. If the parent is for transport between the new node and its parent. If the parent is
not the Authentication Server, it MUST then relay packets from the not the Authentication Server, it MUST then relay packets from the
joining node to the Authentication Server and vice-versa using PANA joining node to the Authentication Server and vice versa, using the
relay mechanism [RFC6345]. The joining node MUST use a link-local PANA relay mechanism [RFC6345]. The joining node MUST use a
address based on its EUI-64 as the source address for initial PANA link-local address based on its EUI-64 as the source address for
authentication message exchanges. initial PANA authentication message exchanges.
4.1.8.2.2. Applicability Statements 4.1.8.2.2. Applicability Statements
The applicability statements describe the relationship between the The following applicability statements describe the relationship
various specifications. between the various specifications.
4.1.8.2.2.1. Applicability Statement for PSK TLS 4.1.8.2.2.1. Applicability Statement for PSK TLS
[RFC6655] contains AEAD TLS cipher suites that are very similar to [RFC6655] contains Authenticated Encryption with Associated Data
[RFC5487] whose AEAD part is detailed in [RFC5116]. [RFC5487] (AEAD) TLS cipher suites that are very similar to [RFC5487], whose
references both [RFC5288] and the original PSK cipher suite document AEAD part is detailed in [RFC5116]. [RFC5487] references both
[RFC4279], which references [RFC5246], which defines the TLS 1.2 [RFC5288] and the original PSK cipher suite document [RFC4279], which
messages. references RFC 2246, which was eventually replaced by [RFC5246],
which defines the TLS 1.2 messages.
4.1.8.2.2.2. Applicability Statement for ECC TLS 4.1.8.2.2.2. Applicability Statement for ECC TLS
[RFC7251] contains AEAD TLS cipher suites that are very similar to [RFC7251] contains AEAD TLS cipher suites that are very similar to
[RFC5289] whose AEAD part is detailed in [RFC5116]. [RFC5289] [RFC5289], whose AEAD part is detailed in [RFC5116]. [RFC5289]
references the original ECC cipher suite document [RFC4492], which references the original ECC cipher suite document [RFC4492], which
references [RFC5246], which defines the TLS 1.2 messages. references RFC 2246, which was eventually replaced by [RFC5246],
which defines the TLS 1.2 messages.
4.1.8.2.2.3. Applicability Statement for EAP-TLS and PANA 4.1.8.2.2.3. Applicability Statement for EAP-TLS and PANA
[RFC5216] specifies how [RFC3748] is used to package [RFC5246] TLS [RFC5216] specifies how [RFC3748] is used to package [RFC5246] TLS
records into EAP packets. [RFC5191] provides transportation for the records into EAP packets. [RFC5191] provides transportation for the
EAP packets and the network-wide key carried in an encrypted AVP EAP packets and the network-wide key carried in an encrypted
specified in [RFC6786]. The proposed PRF and AUTH hashes based on Attribute-Value Pair (AVP) as specified in [RFC6786]. The proposed
SHA-256 are represented as in [RFC5996] and detailed in [RFC4868]. Pseudorandom Function (PRF) and authentication (AUTH) hashes based on
SHA-256 are represented as specified in [RFC7296] and detailed in
[RFC4868].
4.1.8.2.3. Security using RPL message security 4.1.8.2.3. Security Using RPL Message Security
If RPL is used with secured messages [RFC6550], the following RPL If RPL is used with secured messages [RFC6550], the following RPL
security parameter values SHOULD be used: security parameter values SHOULD be used:
o Counter Time Flag (T) = 0: Do not use timestamp in the Counter o Counter is Time (T) flag = 0: Do not use the timestamp in the
Field. Counters based on timestamps are typically more applicable Counter field. Counters based on timestamps are typically more
to industrial networks where strict timing synchronization between applicable to industrial networks, where strict timing
nodes is often implemented. Home and building networks typically synchronization between nodes is often implemented. Home and
do not implement such strict timing synchronization therefore a building networks typically do not implement such strict timing
monotonically increasing counter is more appropriate. synchronization; therefore, a monotonically increasing counter is
more appropriate.
o Algorithm = 0: Use Counter with Cipher Block Chaining Message o Algorithm = 0: Use Counter with the Cipher Block Chaining Message
Authentication Code (CBC-MAC Mode) (CCM) with Advanced Encryption Authentication Code (CBC-MAC Mode) (CCM) with AES-128. This is
Standard (AES)-128. This is the only assigned mode at present. the only assigned mode at present.
o Key Identifier Mode (KIM) = 10: Use group key, Key Source present, o Key Identifier Mode (KIM) = 10: Use a group key, Key Source
Key Index present. Given the relatively confined perimeter of a present, and Key Index present. Given the relatively confined
home or building network, a group key is usually sufficient to perimeter of a home or building network, a group key is usually
protect RPL messages sent between nodes. The use of the Key sufficient to protect RPL messages sent between nodes. The use of
Source field allows multiple group keys to be used within the the Key Source field allows multiple group keys to be used within
network. the network.
o Security Level (LVL) = 0: Use MAC-32. This is recommended as o Security Level (LVL) = 0: Use MAC-32. This is recommended, as
integrity protection for RPL messages is the basic requirement. integrity protection for RPL messages is the basic requirement.
Encryption is unlikely to be necessary given the relatively non- Encryption is unlikely to be necessary, given the relatively
confidential nature of RPL message payloads. non-confidential nature of RPL message payloads.
4.1.9. P2P communications 4.1.9. P2P Communications
[RFC6997] MUST be used to accommodate P2P traffic, which is typically [RFC6997] MUST be used to accommodate P2P traffic, which is typically
substantial in home and building automation networks. substantial in home and building automation networks.
4.1.10. IPv6 address configuration 4.1.10. IPv6 Address Configuration
Assigned IP addresses MUST be routable and unique within the routing Assigned IP addresses MUST be routable and unique within the routing
domain [RFC5889]. domain [RFC5889].
4.2. Layer 2 features 4.2. Layer 2 Features
No particular requirements exist for layer 2 but for the ones cited No particular requirements exist for Layer 2, except for those cited
in the IP over Foo RFCs (see Section 2.3). in the "IP-over-Foo" RFCs (see Section 2.3).
4.2.1. Specifics about layer-2 4.2.1. Specifics about Layer 2
Not applicable Not applicable
4.2.2. Services provided at layer-2 4.2.2. Services Provided at Layer 2
Not applicable Not applicable
4.2.3. 6LowPAN options assumed 4.2.3. IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN)
Options Assumed
Not applicable Not applicable
4.2.4. Mesh Link Establishment (MLE) and other things 4.2.4. Mesh Link Establishment (MLE) and Other Things
Not applicable Not applicable
4.3. Recommended Configuration Defaults and Ranges 4.3. Recommended Configuration Defaults and Ranges
The following sections describe the recommended parameter values for The following sections describe the recommended parameter values for
P2P-RPL and Trickle. P2P-RPL and Trickle.
4.3.1. Trickle parameters 4.3.1. Trickle Parameters
Trickle is used to distribute network parameter values to all nodes Trickle is used to distribute network parameter values to all nodes
without stringent time restrictions. The recommended Trickle without stringent time restrictions. The recommended Trickle
parameter values are: parameter values are:
o DIOIntervalMin 4 = 16 ms o DIOIntervalMin 4, which translates to 16 ms
o DIOIntervalDoublings 14 o DIOIntervalDoublings 14
o DIORedundancyConstant 1 o DIORedundancyConstant 1
When a node sends a changed DIO, this is an inconsistency and forces When a node sends a changed DIO, this is an inconsistency and forces
the receiving node to respond within Imin. So when something happens the receiving node to respond within Imin. So, when something
which affects the DIO, the change is ideally communicated to a node, happens that affects the DIO, the change is ideally communicated to a
n hops away, within n times Imin. Often, dependent on the node node that is n hops away, within n times Imin. Often, depending on
density, packets are lost, or not sent, leading to larger delays. the node density, packets are lost or are not sent, leading to larger
delays.
In general we can expect DIO changes to propagate within 1 to 3 In general, we can expect DIO changes to propagate within 1 to
seconds within the envisaged networks. 3 seconds within the envisaged networks.
When nothing happens, the DIO sending interval increases to 4.37 When nothing happens, the DIO sending interval increases to
minutes, thus drastically reducing the network load. When a node 4.37 minutes, thus drastically reducing the network load. When a
does not receive DIO messages during more than 10 minutes it can node does not receive DIO messages for more than 10 minutes, it can
safely conclude the connection with other nodes has been lost. safely conclude that the connection with other nodes has been lost.
4.3.2. Other Parameters 4.3.2. Other Parameters
This section discusses the P2P-RPL parameters. This section discusses the P2P-RPL parameters.
P2P-RPL [RFC6997] provides the features requested by [RFC5826] and P2P-RPL [RFC6997] provides the features requested by [RFC5826] and
[RFC5867]. P2P-RPL uses a subset of the frame formats and features [RFC5867]. P2P-RPL uses a subset of the frame formats and features
defined for RPL [RFC6550] but may be combined with RPL frame flows in defined for RPL [RFC6550] but may be combined with RPL frame flows in
advanced deployments. advanced deployments.
The recommended parameter values for P2P-RPL are: The recommended parameter values for P2P-RPL are:
o MinHopRankIncrease 1 o MinHopRankIncrease 1
o MaxRankIncrease 0 o MaxRankIncrease 0
o MaxRank 6 o MaxRank 6
o Objective function: OF0 o Objective Function: OF0
5. MPL Profile 5. MPL Profile
MPL is used to distribute values to groups of devices. Using MPL, MPL is used to distribute values to groups of devices. Using MPL,
based on the Trickle algorithm, timeliness should also be guaranteed. based on the Trickle algorithm, timeliness should also be guaranteed.
A deadline of 200 ms needs to be met when human action is followed by A deadline of 200 ms needs to be met when human action is followed by
an immediately observable action such as switching on lights. The an immediately observable action such as switching on lights. The
deadline needs to be met in a building where the number of hops from deadline needs to be met in a building where the number of hops from
seed to destination varies between 1 and 10. seed to destination varies between 1 and 10.
5.1. Recommended configuration Defaults and Ranges 5.1. Recommended Configuration Defaults and Ranges
5.1.1. Real-Time optimizations 5.1.1. Real-Time Optimizations
When the network is heavily loaded, MAC delays contribute When the network is heavily loaded, MAC delays contribute
significantly to the end to end delays when MPL intervals between 10 significantly to the end-to-end delays when MPL intervals between 10
to 100 ms are used to meet the 200 ms deadline. It is possible to and 100 ms are used to meet the 200 ms deadline. It is possible to
set the number of buffers in the MAC to 1 and set the number of Back- set the number of buffers in the MAC to 1 and set the number of
off repetitions to 1. The number of MPL repetitions compensates for back-off repetitions to 1. The number of MPL repetitions compensates
the reduced probability of transmission per MAC invocation [RT-MPL]. for the reduced probability of transmission per MAC invocation
[RT-MPL].
In addition, end to end delays and message losses are reduced, by In addition, end-to-end delays and message losses are reduced by
adding a real-time layer between MPL and MAC to throw away the adding a real-time layer between MPL and MAC to throw away the
earliest messages (exploiting the MPL message numbering) and favour earliest messages (exploiting the MPL message numbering) and favor
the most recent ones. the most recent ones.
5.1.2. Trickle parameters 5.1.2. Trickle Parameters
This section proposes values for the Trickle parameters used by MPL This section proposes values for the Trickle parameters used by MPL
for the distribution of packets that need to meet a 200 ms deadline. for the distribution of packets that need to meet a 200 ms deadline.
The probability of meeting the deadline is increased by (1) choosing The probability of meeting the deadline is increased by (1) choosing
a small Imin value,(2) reducing the number of MPL intervals thus a small Imin value, (2) reducing the number of MPL intervals, thus
reducing the load, and (3) reducing the number of MPL forwarders to reducing the load, and (3) reducing the number of MPL Forwarders to
also reduce the load. also reduce the load.
The consequence of this approach is that the value of k can be larger The consequence of this approach is that the value of k can be larger
than 1 because network load reduction is already guaranteed by the than 1 because network load reduction is already guaranteed by the
network configuration. network configuration.
Under the condition that the density of MPL repeaters can be limited, Under the condition that the density of MPL repeaters can be limited,
it is possible to choose low MPL repeat intervals (Imin) connected to it is possible to choose low MPL repeat intervals (Imin) connected to
k values such that k>1. The minimum value of k is related to: k values such that k > 1. The minimum value of k is related to:
o Value of Imin. The length of Imin determines the number of o The value of Imin. The length of Imin determines the number of
packets that can be received within the listening period of Imin. packets that can be received within the listening period of Imin.
o Number of repeaters receiving the broadcast message from the same o The number of repeaters receiving the broadcast message from the
forwarder or seed. These repeaters repeat within the same Imin same forwarder or seed. These repeaters repeat within the same
interval, thus increasing the c counter. Imin interval, thus increasing the c counter.
Within the first MPL interval a limited number, q, of messages can be Within the first MPL interval, a limited number, q, of messages can
transmitted. Assuming a 3 ms transmission interval, q is given by q be transmitted. Assuming a 3 ms transmission interval, q is given by
= Imin/3. Assuming that at most q message copies can reach a given q = Imin / 3. Assuming that at most q message copies can reach a
forwarder within the first repeat interval of length Imin, the given forwarder within the first repeat interval of length Imin, the
related MPL parameter values are suggested in the following sections. related MPL parameter values are suggested in the following sections.
5.1.2.1. Imin 5.1.2.1. Imin
The recommended value is Imin = 10 to 50 ms. The recommended value is Imin = 10 to 50 ms.
When Imin is chosen much smaller, the interference between the copies When the chosen Imin value is much smaller, the interference between
leads to significant losses given that q is much smaller than the the copies leads to significant losses, given that q is much smaller
number of repeated packets. With much larger intervals the than the number of repeated packets. With much larger intervals, the
probability that the deadline will be met decreases with increasing probability that the deadline will be met decreases with increasing
hop count. hop count.
5.1.2.2. Imax 5.1.2.2. Imax
The recommended value is Imax = 100 to 400 ms. The recommended value is Imax = 100 to 400 ms.
The value of Imax is less important than the value of max_expiration. The value of Imax is less important than the value of max_expiration.
Given an Imin value of 10 ms, the 3rd MPL interval has a value of Given an Imin value of 10 ms, the third MPL interval has a value of
10*2*2 = 40 ms. When Imin has a value of 40 ms, the 3rd interval has 10 * 2 * 2 = 40 ms. When Imin has a value of 40 ms, the third
a value of 160 ms. Given that more than 3 intervals are unnecessary, interval has a value of 160 ms. Given that more than three intervals
the Imax does not contribute much to the performance. are unnecessary, Imax does not contribute much to performance.
5.1.3. Other parameters 5.1.3. Other Parameters
Other parameters are the k parameter and the max_expiration Other parameters are the k parameter and the max_expiration
parameter. parameter.
k > q (see condition above). Under this condition and for small k > q (see condition above). Under this condition, and for a small
Imin, a value of k=2 or k=3 is usually sufficient to minimize the Imin value, a value of k = 2 or k = 3 is usually sufficient to
losses of packets in the first repeat interval. minimize the losses of packets in the first repeat interval.
max_expiration = 2 - 4. Higher values lead to more network load max_expiration = 2 - 4. Higher values lead to more network load
while generating copies which will probably not meet their deadline. while generating copies that will probably not meet their deadline.
6. Manageability Considerations 6. Manageability Considerations
At this moment it is not clear how homenets will be managed. At this time, it is not clear how homenets will be managed.
Consequently it is not clear which tools will be used and which Consequently, it is not clear which tools will be used and which
parameters must be exposed for management. parameters must be visible for management.
In building control, management is mandatory. It is expected that In building control, management is mandatory. It is expected that
installations will be managed using the set of currently available installations will be managed using the set of currently available
tools(including IETF tools like Management Information Base (MIB) tools (including IETF tools like Management Information Base (MIB)
modules, NETCONF modules, Dynamic Host Configuration Protocol (DHCP) modules, Network Configuration Protocol (NETCONF) modules, Dynamic
and others) with large differences between the ways an installation Host Configuration Protocol (DHCP), and others), with large
is managed. differences between the ways an installation is managed.
7. Security Considerations 7. Security Considerations
This section refers to the security considerations of [RFC6997], This section refers to the security considerations of [RFC6997],
[RFC6550], [I-D.ietf-roll-trickle-mcast], and the counter measures [RFC6550], and [RFC7731], as well as some attacks and countermeasures
discussed in sections 6 and 7 of [RFC7416]. as discussed in Sections 6 and 7, respectively, of [RFC7416].
Communications network security is based on providing integrity Communications network security is based on providing integrity
protection and encryption to messages. This can be applied at protection and encryption to messages. This can be applied at
various layers in the network protocol stack based on using various various layers in the network protocol stack, based on using various
credentials and a network identity. credentials and a network identity.
The credentials which are relevant in the case of RPL are: (i) the The credentials that are relevant in the case of RPL are (i) the
credential used at the link layer in the case where link layer credential used at the link layer in the case where link-layer
security is applied (see Section 7.1) or (ii) the credential used for security is applied (see Section 7.1) or (ii) the credential used for
securing RPL messages. In both cases, the assumption is that the securing RPL messages. In both cases, the assumption is that the
credential is a shared key. Therefore, there MUST be a mechanism in credential is a shared key. Therefore, there MUST be a mechanism in
place which allows secure distribution of a shared key and place that allows secure distribution of a shared key and
configuration of network identity. Both MAY be done using: (i) pre- configuration of a network identity. Both MAY be done using
installation using an out-of-band method, (ii) delivered securely (i) pre-installation using an out-of-band method, (ii) secure
when a device is introduced into the network or (iii) delivered delivery when a device is introduced into the network, or
securely by a trusted neighbouring device as described in (iii) secure delivery by a trusted neighboring device, as described
Section 4.1.8.1. The shared key MUST be stored in a secure fashion in Section 4.1.8.1. The shared key MUST be stored in a secure
which makes it difficult to be read by an unauthorized party. fashion that will make it difficult to be read by an unauthorized
party.
This document mandates that a layer-2 mechanism be used during This document mandates that a Layer 2 mechanism be used during
initial and incremental deployment. Please see the following initial and incremental deployment. Please see the following
sections. sections.
7.1. Security considerations during initial deployment 7.1. Security Considerations during Initial Deployment
Wireless mesh networks are typically secured at the link layer in Wireless mesh networks are typically secured at the link layer in
order to prevent unauthorized parties from accessing the information order to prevent unauthorized parties from accessing the information
exchanged over the links. It is a basic practice to create a network exchanged over the links. It is a basic practice to create a network
of nodes which share the same keys for link layer security and of nodes that share the same keys for link-layer security and exclude
exclude nodes sending unsecured messages. With per-message data nodes sending unsecured messages. With per-message data origin
origin authentication, it is possible to prevent unauthorized nodes authentication, it is possible to prevent unauthorized nodes from
joining the mesh. joining the mesh.
At initial deployment the network is secured by consecutively At initial deployment, the network is secured by consecutively
securing nodes at the link layer, thus building a network of secured securing nodes at the link layer, thus building a network of secured
nodes. Section 4.1.8.2 describes a mechanism for building a network nodes. Section 4.1.8.2 describes a mechanism for building a network
of secured nodes. of secured nodes.
This document does not specify a multicast security solution. This document does not specify a multicast security solution.
Networks deployed with this specification will depend upon layer-2 Networks deployed with this specification will depend upon Layer 2
security to prevent outsiders from sending multicast traffic. It is security to prevent outsiders from sending multicast traffic. It is
recognized that this does not protect this control traffic from recognized that this does not protect this control traffic from
impersonation by already trusted devices. This is an area for a impersonation by already-trusted devices. This is an area for a
future specification. future specification.
For building control an installer will use an installation tool that For building control, an installer will use an installation tool that
establishes a secure communication path with the joining node. It is establishes a secure communication path with the joining node. It is
recognized that the recommendations for initial deployment of recognized that the recommendations for initial deployment as
Section 7 and Section 7.1 do not cover all building requirements such discussed in this section do not cover all building requirements,
as selecting the node-to-secure independent of network topology. such as selecting -- independent of network topology -- the node to
be secured.
It is expected that a set of protocol combinations will evolve within It is expected that a set of protocol combinations will evolve within
currently existing alliances of building control manufacturers. Each currently existing alliances of building control manufacturers. Each
set satisfies the installation requirements of installers, operators, set satisfies the installation requirements of installers, operators,
and manufacturers of building control networks in a given and manufacturers of building control networks in a given
installation context, e.g lighting deployment in offices, HVAC installation context, e.g., lighting deployment in offices, HVAC
installation, incremental addition of equipment in homes, and others. installation, incremental addition of equipment in homes, and others.
In the home, nodes can be visually inspected by the home owner and a In the home, nodes can be visually inspected by the home owner.
simple procedure, e.g. pushing buttons simultaneously on an already Also, a simple procedure, e.g., pushing buttons simultaneously on an
secured device and an unsecured joining device is usually sufficient already-secured device and an unsecured joining device, is usually
to ensure that the unsecured joining device is authenticated and sufficient to ensure that the unsecured joining device is
configured securely, and paired appropriately. authenticated securely, configured securely, and paired
appropriately.
This recommendation is in line with the countermeasures described in This recommendation is in line with the countermeasures described in
section 6.1.1 of [RFC7416]. Section 7.1 of [RFC7416].
7.2. Security Considerations during incremental deployment 7.2. Security Considerations during Incremental Deployment
Once a network is operational, new nodes need to be added, or nodes Once a network is operational, new nodes need to be added, or nodes
fail and need to be replaced. When a new node needs to be added to fail and need to be replaced. When a new node needs to be added to
the network, the new node is joined to the network via an assisting the network, the new node is added to the network via an assisting
node in the manner described in Section 7.1. node in the manner described in Section 7.1.
On detection of a compromised node, all trusted nodes need to have On detection of a compromised node, all trusted nodes need to have
their symmetric keys known to be shared with the compromised node re- their symmetric keys that are known to be shared with the compromised
keyed, and the trusted network is built up as described in node rekeyed, and the trusted network is built up as described in
Section 7.1. Section 7.1.
7.3. Security Considerations for P2P uses 7.3. Security Considerations for P2P Implementations
Refer to the security considerations of [RFC6997]. Refer to the security considerations of [RFC6997].
7.4. MPL routing 7.4. MPL Routing
The routing of MPL is determined by the enabling of the interfaces The routing of MPL is determined by the enabling of the interfaces
for specified Multicast addresses. The specification of these for specified multicast addresses. The specification of these
addresses can be done via a Constrained Application Protocol (CoAP) addresses can be done via a Constrained Application Protocol (CoAP)
application as specified in [RFC7390]. An alternative is the application as specified in [RFC7390]. An alternative is the
creation of a MPL MIB and use of Simple Network Management Protocol creation of an MPL MIB and the use of the Simple Network Management
(SNMP)v3 [RFC3411] or equivalent techniques to specify the Multicast Protocol (SNMPv3) [RFC3411] or equivalent techniques to specify the
addresses in the MIB. For secure dissemination of MPL packets, layer multicast addresses in the MIB. For secure dissemination of MPL
2 security SHOULD be used and the configuration of multicast packets, Layer 2 security SHOULD be used, and the configuration of
addresses as described in this section MUST be secure. multicast addresses as described in this section MUST be secure.
7.5. RPL Security features 7.5. RPL Security Features
This section follows the structure of section 8, "RPL security This section refers to the structure of Section 8 ("RPL Security
features" of [RFC7416]. [RFC7416] provides a thorough analysis of Features") of [RFC7416]. [RFC7416] provides a thorough analysis of
security threats and proposed counter measures relevant to RPL and security threats and proposed countermeasures relevant to RPL
MPL. and MPL.
In accordance with section 8.1 of [RFC7416], "Confidentiality In accordance with Section 8.1 ("Confidentiality Features") of
features", RPL message security implements payload protection, as [RFC7416], RPL message security implements payload protection, as
explained in Section 7 of this document. The attributes key-length explained in Section 7 of this document. The attributes for key
and life-time of the keys depend on operational conditions, length and lifetime of the keys depend on operational conditions,
maintenance and installation procedures. maintenance, and installation procedures.
Section 7.1 and Section 7.2 of this document recommend link-layer Sections 7.1 and 7.2 of this document recommend link-layer security
security to assure integrity in accordance with section 8.2 of to assure integrity in accordance with Section 8.2 ("Integrity
[RFC7416], "Integrity features". Features") of [RFC7416].
The provision of multiple paths recommended in section 8.3 The provision of multiple paths recommended in Section 8.3
"Availability features" of [RFC7416] is also recommended from a ("Availability Features") of [RFC7416] is also recommended from a
reliability point of view. Randomly choosing paths MAY be supported. reliability point of view. Randomly choosing paths MAY be supported.
A mechanism for key management, discussed in section 8.4, "Key A mechanism for key management, as discussed in Section 8.4 ("Key
Management" of [RFC7416], is provided in Section 4.1.8.2. Management") of [RFC7416], is provided in Section 4.1.8.2 of this
document.
Section 7.5, "Considerations on Matching Application Domain Needs" of
[RFC7416] applies as such.
8. Other related protocols 8. Other Related Protocols
Application and transport protocols used in home and building Application and transport protocols used in home and building
automation domains are expected to mostly consist in CoAP over UDP, automation domains are expected to mostly consist of CoAP over UDP,
or equivalents. Typically, UDP is used for IP transport to keep down or equivalents. Typically, UDP is used for IP transport to keep down
the application response time and bandwidth overhead. CoAP is used the application response time and bandwidth overhead. CoAP is used
at the application layer to reduce memory footprint and bandwidth at the application layer to reduce memory footprint and bandwidth
requirements. requirements.
9. IANA Considerations 9. References
No considerations for IANA pertain to this document.
10. Acknowledgements
This document reflects discussions and remarks from several
individuals including (in alphabetical order): Stephen Farrell, Mukul
Goyal, Sandeep Kumar, Jerry Martocci, Catherine Meadows, Yoshihira
Ohba, Charles Perkins, Yvonne-Anne Pignolet, Michael Richardson, Ines
Robles, Zach Shelby, and Meral Sherazipour.
11. Changelog
RFC editor, please delete this section before publication.
Changes from version 0 to version 1.
o Adapted section structure to template.
o Standardized the reference syntax.
o Section 2.2, moved everything concerning algorithms to section
2.2.7, and adapted text in 2.2.1-2.2.6.
o Added MPL parameter text to section 4.1.7 and section 4.3.1.
o Replaced all TODO sections with text.
o Consistent use of border router, monitoring, home- and building
network.
o Reformulated security aspects with references to other
publications.
o MPL and RPL parameter values introduced.
Changes from version 1 to version 2.
o Clarified common characteristics of control in home and building.
o Clarified failure behaviour of point to point communication in
appendix.
o Changed examples, more hvac and less lighting.
o Clarified network topologies.
o replaced reference to smart_object paper by reference to I-D.roll-
security-threats
o Added a concise definition of secure delivery and secure storage
o Text about securing network with PANA
Changes from version 2 to version 3.
o Changed security section to follow the structure of security
threats draft.
o Added text to DODAG repair sub-section
Changes from version 3 to version 4.
o Renumbered sections and moved text to conform to applicability
template
o Extended MPL parameter value text
o Added references to building control products
Changes from version 4 to version 5.
o Large editing effort to streamline text
o Rearranged Normative and Informative references
o Replaced RFC2119 terminology by non-normative terminology
o Rearranged text of section 7, 7.1, and 7.2 to agree with the
intention of section 7.2
Changes from version 5 to version 6.
o Issues #162 - #166 addressed
Changes from version 6 to version 7.
o Text of section 7.1 edited for better security coverage.
Changes from version 7 to version 8.
o Requirements language paragraph removed
o Acronyms clarified
o MPL parameters clarified
Changes from version 8 to version 9.
o More acronyms clarified
o References updated
Changes from version 9 to version 10.
o Changes due to IESG and security review
o Requirements language reinstated
o RPL security parameter selection clarified
o Removed multicast security reference
Changes from version 10 to 11.
o Further changes due to IESG and security review
o ZigBee IP authentication and key establishment specified
Changes from version 11 to 12.
o Further clarifications added
12. References
12.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<http://www.rfc-editor.org/info/rfc3748>. <http://www.rfc-editor.org/info/rfc3748>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key [RFC4279] Eronen, P., Ed., and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005, RFC 4279, DOI 10.17487/RFC4279, December 2005,
<http://www.rfc-editor.org/info/rfc4279>. <http://www.rfc-editor.org/info/rfc4279>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006, DOI 10.17487/RFC4492, May 2006,
<http://www.rfc-editor.org/info/rfc4492>. <http://www.rfc-editor.org/info/rfc4492>.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA- [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256,
384, and HMAC-SHA-512 with IPsec", RFC 4868, HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007, DOI 10.17487/RFC4868, May 2007,
<http://www.rfc-editor.org/info/rfc4868>. <http://www.rfc-editor.org/info/rfc4868>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4 "Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007, Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>. <http://www.rfc-editor.org/info/rfc4944>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
skipping to change at page 29, line 44 skipping to change at page 29, line 28
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois [RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288, Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
DOI 10.17487/RFC5288, August 2008, DOI 10.17487/RFC5288, August 2008,
<http://www.rfc-editor.org/info/rfc5288>. <http://www.rfc-editor.org/info/rfc5288>.
[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA- [RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with
256/384 and AES Galois Counter Mode (GCM)", RFC 5289, SHA-256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
DOI 10.17487/RFC5289, August 2008, DOI 10.17487/RFC5289, August 2008,
<http://www.rfc-editor.org/info/rfc5289>. <http://www.rfc-editor.org/info/rfc5289>.
[RFC5487] Badra, M., "Pre-Shared Key Cipher Suites for TLS with SHA- [RFC5487] Badra, M., "Pre-Shared Key Cipher Suites for TLS with
256/384 and AES Galois Counter Mode", RFC 5487, SHA-256/384 and AES Galois Counter Mode", RFC 5487,
DOI 10.17487/RFC5487, March 2009, DOI 10.17487/RFC5487, March 2009,
<http://www.rfc-editor.org/info/rfc5487>. <http://www.rfc-editor.org/info/rfc5487>.
[RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and [RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and
D. Barthel, Ed., "Routing Requirements for Urban Low-Power D. Barthel, Ed., "Routing Requirements for Urban Low-Power
and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548,
2009, <http://www.rfc-editor.org/info/rfc5548>. May 2009, <http://www.rfc-editor.org/info/rfc5548>.
[RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
Phinney, "Industrial Routing Requirements in Low-Power and Phinney, "Industrial Routing Requirements in Low-Power and
Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October Lossy Networks", RFC 5673, DOI 10.17487/RFC5673,
2009, <http://www.rfc-editor.org/info/rfc5673>. October 2009, <http://www.rfc-editor.org/info/rfc5673>.
[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, DOI 10.17487/RFC5826, April 2010, RFC 5826, DOI 10.17487/RFC5826, April 2010,
<http://www.rfc-editor.org/info/rfc5826>. <http://www.rfc-editor.org/info/rfc5826>.
[RFC5867] Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen, [RFC5867] Martocci, J., Ed., 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, DOI 10.17487/RFC5867, June Lossy Networks", RFC 5867, DOI 10.17487/RFC5867,
2010, <http://www.rfc-editor.org/info/rfc5867>. June 2010, <http://www.rfc-editor.org/info/rfc5867>.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, DOI 10.17487/RFC5996, September 2010,
<http://www.rfc-editor.org/info/rfc5996>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6 [RFC6282] Hui, J., Ed., and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011, DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>. <http://www.rfc-editor.org/info/rfc6282>.
[RFC6345] Duffy, P., Chakrabarti, S., Cragie, R., Ohba, Y., Ed., and [RFC6345] Duffy, P., Chakrabarti, S., Cragie, R., Ohba, Y., Ed., and
A. Yegin, "Protocol for Carrying Authentication for A. Yegin, "Protocol for Carrying Authentication for
Network Access (PANA) Relay Element", RFC 6345, Network Access (PANA) Relay Element", RFC 6345,
DOI 10.17487/RFC6345, August 2011, DOI 10.17487/RFC6345, August 2011,
<http://www.rfc-editor.org/info/rfc6345>. <http://www.rfc-editor.org/info/rfc6345>.
skipping to change at page 31, line 28 skipping to change at page 31, line 12
Attribute-Value Pairs", RFC 6786, DOI 10.17487/RFC6786, Attribute-Value Pairs", RFC 6786, DOI 10.17487/RFC6786,
November 2012, <http://www.rfc-editor.org/info/rfc6786>. November 2012, <http://www.rfc-editor.org/info/rfc6786>.
[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
J. Martocci, "Reactive Discovery of Point-to-Point Routes J. Martocci, "Reactive Discovery of Point-to-Point Routes
in Low-Power and Lossy Networks", RFC 6997, in Low-Power and Lossy Networks", RFC 6997,
DOI 10.17487/RFC6997, August 2013, DOI 10.17487/RFC6997, August 2013,
<http://www.rfc-editor.org/info/rfc6997>. <http://www.rfc-editor.org/info/rfc6997>.
[RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci, [RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci,
"A Mechanism to Measure the Routing Metrics along a Point- "A Mechanism to Measure the Routing Metrics along a
to-Point Route in a Low-Power and Lossy Network", Point-to-Point Route in a Low-Power and Lossy Network",
RFC 6998, DOI 10.17487/RFC6998, August 2013, RFC 6998, DOI 10.17487/RFC6998, August 2013,
<http://www.rfc-editor.org/info/rfc6998>. <http://www.rfc-editor.org/info/rfc6998>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January Lossy Networks", RFC 7102, DOI 10.17487/RFC7102,
2014, <http://www.rfc-editor.org/info/rfc7102>. January 2014, <http://www.rfc-editor.org/info/rfc7102>.
[RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES- [RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal,
CCM Elliptic Curve Cryptography (ECC) Cipher Suites for "AES-CCM Elliptic Curve Cryptography (ECC) Cipher Suites
TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014, for TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014,
<http://www.rfc-editor.org/info/rfc7251>. <http://www.rfc-editor.org/info/rfc7251>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296,
October 2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
and M. Richardson, Ed., "A Security Threat Analysis for and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<http://www.rfc-editor.org/info/rfc7416>. <http://www.rfc-editor.org/info/rfc7416>.
[I-D.ietf-roll-trickle-mcast] [RFC7731] Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
Hui, J. and R. Kelsey, "Multicast Protocol for Low power and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
and Lossy Networks (MPL)", draft-ietf-roll-trickle- February 2016, <http://www.rfc-editor.org/info/rfc7731>.
mcast-12 (work in progress), June 2015.
[IEEE802.15.4] [IEEE802.15.4]
"IEEE 802.15.4 - Standard for Local and metropolitan area IEEE, "IEEE Standard for Local and metropolitan area
networks -- Part 15.4: Low-Rate Wireless Personal Area networks--Part 15.4: Low-Rate Wireless Personal Area
Networks", <IEEE Standard 802.15.4>. Networks (LR-WPANs)", IEEE 802.15.4,
DOI 10.1109/ieeestd.2011.6012487,
<http://ieeexplore.ieee.org/servlet/
opac?punumber=6012485>.
[G.9959] "ITU-T G.9959 Short range narrow-band digital [G.9959] International Telecommunication Union, "Short range
radiocommunication transceivers - PHY and MAC layer narrow-band digital radiocommunication transceivers - PHY,
specifications", <ITU-T G.9959>. MAC, SAR and LLC layer specifications", ITU-T
Recommendation G.9959, January 2015,
<http://www.itu.int/rec/T-REC-G.9959>.
12.2. Informative References 9.2. Informative References
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411, Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
DOI 10.17487/RFC3411, December 2002, DOI 10.17487/RFC3411, December 2002,
<http://www.rfc-editor.org/info/rfc3411>. <http://www.rfc-editor.org/info/rfc3411>.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc
Demand Distance Vector (AODV) Routing", RFC 3561, On-Demand Distance Vector (AODV) Routing", RFC 3561,
DOI 10.17487/RFC3561, July 2003, DOI 10.17487/RFC3561, July 2003,
<http://www.rfc-editor.org/info/rfc3561>. <http://www.rfc-editor.org/info/rfc3561>.
[RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing [RFC5889] Baccelli, E., Ed., and M. Townsley, Ed., "IP Addressing
Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889, Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
September 2010, <http://www.rfc-editor.org/info/rfc5889>. September 2010, <http://www.rfc-editor.org/info/rfc5889>.
[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC 6552, DOI 10.17487/RFC6552, March 2012,
<http://www.rfc-editor.org/info/rfc6552>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014, DOI 10.17487/RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>. <http://www.rfc-editor.org/info/rfc7228>.
[RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for [RFC7390] Rahman, A., Ed., and E. Dijk, Ed., "Group Communication
the Constrained Application Protocol (CoAP)", RFC 7390, for the Constrained Application Protocol (CoAP)",
DOI 10.17487/RFC7390, October 2014, RFC 7390, DOI 10.17487/RFC7390, October 2014,
<http://www.rfc-editor.org/info/rfc7390>. <http://www.rfc-editor.org/info/rfc7390>.
[RFC7428] Brandt, A. and J. Buron, "Transmission of IPv6 Packets [RFC7428] Brandt, A. and J. Buron, "Transmission of IPv6 Packets
over ITU-T G.9959 Networks", RFC 7428, over ITU-T G.9959 Networks", RFC 7428,
DOI 10.17487/RFC7428, February 2015, DOI 10.17487/RFC7428, February 2015,
<http://www.rfc-editor.org/info/rfc7428>. <http://www.rfc-editor.org/info/rfc7428>.
[SOFT11] Baccelli, E., Phillip, M., and M. Goyal, "The P2P-RPL [SOFT11] Baccelli, E., Philipp, M., and M. Goyal, "The P2P-RPL
Routing Protocol for IPv6 Sensor Networks: Testbed Routing Protocol for IPv6 Sensor Networks: Testbed
Experiments", Proceedings of the Conference on Software Experiments", Proceedings of the 19th Annual Conference on
Telecommunications and Computer Networks, Split, Croatia,, Software Telecommunications and Computer Networks, Split,
September 2011. Croatia, September 2011.
[INTEROP12] [INTEROP12]
Baccelli, E., Phillip, M., Brandt, A., Valev , H., and J. Philipp, M., Baccelli, E., Brandt, A., Valev, H., and J.
Buron , "Report on P2P-RPL Interoperability Testing", Buron, "Report on P2P-RPL Interoperability Testing", INRIA
RR-7864 INRIA Research Report RR-7864, January 2012. Research Report RR-7864, January 2012.
[RT-MPL] van der Stok, P., "Real-Time multicast for wireless mesh [RT-MPL] van der Stok, P., "Real-Time multicast for wireless mesh
networks using MPL", White paper, networks using MPL", White paper, April 2014,
http://www.vanderstok.org/papers/Real-time-MPL.pdf, April <http://www.vanderstok.org/papers/Real-time-MPL.pdf>.
2014.
[occuswitch] [OccuSwitch]
Lighting, Philips., "OccuSwitch wireless", Brochure, http Philips lighting Electronics, "OccuSwitch Wireless
://www.philipslightingcontrols.com/assets/cms/uploads/file (brochure)", May 2012,
s/osw/MK_OSWNETBROC_5.pdf, May 2012. <http://www.philipslightingcontrols.com/assets/
cms/uploads/files/osw/MK_OSWNETBROC_5.pdf>.
[office-light] [Office-Light]
Clanton and Associates, ., "A Life Cycle Cost Evaluation Clanton and Associates, Inc., "Wireless Lighting Control -
of Multiple Lighting Control Strategies", Wireless A Life Cycle Cost Evaluation of Multiple Lighting Control
Lighting Control, http://www.daintree.net/wp- Strategies", February 2014, <http://www.daintree.net/
content/uploads/2014/02/ wp-content/uploads/2014/02/
clanton_lighting_control_report_0411.pdf, February 2014. clanton_lighting_control_report_0411.pdf>.
[RTN2011] Holtman, K. and P. van der Stok, "Real-time routing for [RTN2011] Holtman, K. and P. van der Stok, "Real-time routing for
low-latency 802.15.4 control networks", International low-latency 802.15.4 control networks", 23rd Euromicro
Workshop on Real-Time Networks; Euromicro Conference on Conference on Real-Time Systems, Porto, Portugal,
Real-Time Systems, July 2011. July 2011.
[MEAS] Holtman, K., "Connectivity loss in large scale IEEE [MEAS] Holtman, K., "Connectivity loss in large scale
802.15.4 network", Private Communication, November 2013. IEEE 802.15.4 network", Private Communication,
November 2013.
[BCsurvey] [BC-Survey]
Kastner, W., Neugschwandtner, G., Soucek, S., and H. Kastner, W., Neugschwandtner, G., Soucek, S., and H.
Newman, "Communication Systems for Building Automation and Newmann, "Communication Systems for Building Automation
Control", Proceedings of the IEEE Vol 93, No 6, June and Control", Proceedings of the IEEE, Vol. 93, No. 6,
2005. DOI 10.1109/JPROC.2005.849726, June 2005.
[ZigBeeIP] [ZigBeeIP]
ZigBee Alliance, ., "ZigBee IP specification", ZigBee ZigBee Alliance, "ZigBee IP specification", ZigBee
document 095023r34, March 2014. document 095023r34, March 2014, <http://www.zigbee.org/>.
Appendix A. RPL shortcomings in home and building deployments Appendix A. RPL Shortcomings in Home and Building Deployments
A.1. Risk of undesired long P2P routes A.1. Risk of Undesirable Long P2P Routes
The DAG, being a tree structure is formed from a root. If nodes The DAG, being a tree structure, is formed from a root. If nodes
residing in different branches have a need for communicating residing in different branches need to communicate internally, DAG
internally, DAG mechanisms provided in RPL [RFC6550] will propagate mechanisms provided in RPL [RFC6550] will propagate traffic towards
traffic towards the root, potentially all the way to the root, and the root, potentially all the way to the root, and down along another
down along another branch [RFC6998]. In a typical example two nodes branch [RFC6998]. In a typical example, two nodes could reach each
could reach each other via just two router nodes but in unfortunate other via only two router nodes, but in some unfortunate cases, RPL
cases, RPL may send traffic three hops up and three hops down again. may send traffic three hops up and three hops down again. This leads
This leads to several undesired phenomena described in the following to several undesirable phenomena, as described in the following
sections. sections.
A.1.1. Traffic concentration at the root A.1.1. Traffic Concentration at the Root
If many P2P data flows have to move up towards the root to get down If many P2P data flows have to move up towards the root to get down
again in another branch there is an increased risk of congestion the again in another branch, there is an increased risk of congestion the
nearer to the root of the DAG the data flows. Due to the broadcast nearer to the root of the DAG the data flows. Due to the broadcast
nature of RF systems any child node of the root is not just directing nature of radio frequency (RF) systems, any child node of the root is
RF power downwards its sub-tree but just as much upwards towards the not only directing RF power downwards in its sub-tree but just as
root; potentially jamming other MP2P traffic leaving the tree or much upwards towards the root, potentially jamming other MP2P traffic
preventing the root of the DAG from sending P2MP traffic into the DAG leaving the tree or preventing the root of the DAG from sending P2MP
because the listen-before-talk link-layer protection kicks in. traffic into the DAG because the listen-before-talk link-layer
protection kicks in.
A.1.2. Excessive battery consumption in source nodes A.1.2. Excessive Battery Consumption in Source Nodes
Battery-powered nodes originating P2P traffic depend on the route Battery-powered nodes originating P2P traffic depend on the route
length. Long routes cause source nodes to stay awake for longer length. Long routes cause source nodes to stay awake for longer
periods before returning to sleep. Thus, a longer route translates periods before returning to sleep. Thus, a longer route translates
proportionally (more or less) into higher battery consumption. proportionally (more or less) into higher battery consumption.
A.2. Risk of delayed route repair A.2. Risk of Delayed Route Repair
The RPL DAG mechanism uses DIO and DAO messages to monitor the health The RPL DAG mechanism uses DIO and DAO messages to monitor the health
of the DAG. In rare occasions, changed radio conditions may render of the DAG. On rare occasions, changed radio conditions may render
routes unusable just after a destination node has returned a DAO routes unusable just after a destination node has returned a DAO
indicating that the destination is reachable. Given enough time, the indicating that the destination is reachable. Given enough time, the
next Trickle timer-controlled DIO/DAO update will eventually repair next Trickle timer-controlled DIO/DAO update will eventually repair
the broken routes, however this may not occur in a timely manner the broken routes; however, this may not occur in a timely manner
appropriate to the application. In an apparently stable DAG, appropriate to the application. In an apparently stable DAG,
Trickle-timer dynamics may reduce the update rate to a few times Trickle timer dynamics may reduce the update rate to a few times
every hour. If a user issues an actuator command, e.g. light on in every hour. If a user issues an actuator command, e.g., light on in
the time interval between the last DAO message was issued the the time interval between the time that the last DAO message was
destination module and the time one of the parents sends the next issued the destination module and the time that one of the parents
DIO, the destination cannot be reached. There is no mechanism in RPL sends the next DIO, the destination cannot be reached. There is no
to initiate restoration of connectivity in a reactive fashion. The mechanism in RPL to initiate the restoration of connectivity in a
consequence is a broken service in home and building applications. reactive fashion. The consequence is a broken service in home and
building applications.
A.2.1. Broken service A.2.1. Broken Service
Experience from the telecom industry shows that if the voice delay Experience from the telecom industry shows that if the voice delay
exceeds 250ms, users start getting confused, frustrated and/or exceeds 250 ms, users start getting confused, frustrated, and/or
annoyed. In the same way, if the light does not turn on within the annoyed. In the same way, if the light does not turn on within the
same period of time, a home control user will activate the controls same period of time, a home control user will activate the controls
again, causing a sequence of commands such as again, causing a sequence of commands such as
Light{on,off,off,on,off,..} or Volume{up,up,up,up,up,...}. Whether Light{on,off,off,on,off,...} or Volume{up,up,up,up,up,...}. Whether
the outcome is nothing or some unintended response this is the outcome is nothing or some unintended response, this is
unacceptable. A controlling system must be able to restore unacceptable. A controlling system must be able to restore
connectivity to recover from the error situation. Waiting for an connectivity to recover from the error situation. Waiting for an
unknown period of time is not an option. While this issue was unknown period of time is not an option. Although this issue was
identified during the P2P analysis, it applies just as well to identified during the P2P analysis, it applies just as well to
application scenarios where an IP application outside the LLN application scenarios where an IP application outside the LLN
controls actuators, lights, etc. controls actuators, lights, etc.
Appendix B. Communication failures Appendix B. Communication Failures
Measurements on the connectivity between neighbouring nodes are Measurements of connectivity between neighboring nodes are discussed
discussed in [RTN2011] and [MEAS]. in [RTN2011] and [MEAS].
The work is motivated by the measurements in literature which affirm The work is motivated by the measurements in literature that affirm
that the range of an antenna is not circle symmetric but that the that the range of an antenna is not circle symmetric but that the
signal strength of a given level follows an intricate pattern around signal strength of a given level follows an intricate pattern around
the antenna, and there may be holes within the area delineated by an the antenna, and there may be holes within the area delineated by a
iso-strength line. It is reported that communication is not polar plot. It is reported that communication is not symmetric:
symmetric: reception of messages from node A by node B does not imply reception of messages from node A by node B does not imply reception
reception of messages from node B by node A. The quality of the of messages from node B by node A. The quality of the signal
signal fluctuates over time, and also the height of the antenna fluctuates over time, and also the height of the antenna within a
within a room can have consequences for the range. As function of room can have consequences for the range. As a function of the
the distance from the source, three regions are generally recognized: distance from the source, three regions are generally recognized:
(1) a clear region with excellent signal quality, (2) a region with (1) a clear region with excellent signal quality, (2) a region with
fluctuating signal quality, (3) a region without reception. In the fluctuating signal quality, and (3) a region without reception.
text below it is shown that installation of meshes with neighbours in Installation of meshes with neighbors in the clear region is not
the clear region is not sufficient. sufficient, as described below.
[RTN2011] extends existing work by: [RTN2011] extends existing work by:
o Observations over periods of at least a week, o Observations over periods of at least a week,
o Testing links that are in the clear region, o Testing links that are in the clear region,
o Observation in an office building during working hours, o Observation in an office building during working hours, and
o Concentrating on one-hop and two-hop routes. o Concentrating on one-hop and two-hop routes.
Eight nodes were distributed over a surface of 30m2. All nodes are Eight nodes were distributed over a surface of 30 square meters. All
at one hop distance from each other and are situated in the clear nodes are at a one-hop distance from each other, and all are situated
region of each other. Each node sends messages to each of its in each other's clear region. Each node sends messages to each of
neighbours, and repeats the message until it arrives. The latency of its neighbors and repeats the message until it arrives. The latency
the message was measured over periods of at least a week. It is of the message was measured over periods of at least a week. It was
noticed that latencies longer than a second occurred without apparent noticed that latencies longer than a second occurred without any
reasons, but only during working days and never in the weekends. Bad apparent reason, but only during working days and never during the
periods could last for minutes. By sending messages via two paths: weekends. Bad periods could last for minutes. By sending messages
(1) one hop path directly, and (2) two hop path via a randomly chosen via two paths -- (1) a one-hop path directly and (2) a two-hop path
neighbour, the probability of delays larger than 100 ms decreased via a randomly chosen neighbor -- the probability of delays larger
significantly. than 100 ms decreased significantly.
The conclusion is that even for 1-hop communication between not too The conclusion is that even for one-hop communication between
distant "Line of Sight" nodes, there are periods of low reception in not-too-distant "line of sight" nodes, there are periods of low
which communication deadlines of 200 ms are exceeded. It pays to reception in which communication deadlines of 200 ms are exceeded.
send a second message over a 2-hop path to increase the reliability It pays to send a second message over a two-hop path to increase the
of timely message transfer. reliability of timely message transfer.
[MEAS] confirms that temporary bad reception by close neighbours can [MEAS] confirms that temporary bad reception by close neighbors can
occur within other types of areas. Nodes were installed on the occur within other types of areas. Nodes were installed on the
ceiling in a grid with a distance of 30-50 cm between nodes. 200 ceiling in a grid with a distance of 30-50 cm between them.
nodes were distributed over an area of 10m x 5m. It clearly Two hundred nodes were distributed over an area of 10 m x 5 m. It
transpired that with increasing distance the probability of reception clearly transpired that with increasing distance the probability of
decreases. At the same time a few nodes furthest away from the reception decreased. At the same time, a few nodes furthest away
sender had a high probability of message reception, while some close from the sender had a high probability of message reception, while
neighbours of the sender did not receive messages. The patterns of some close neighbors of the sender did not receive messages. The
clear reception nodes evolved over time. patterns of nodes experiencing good reception evolved over time.
The conclusion is that even for direct neighbours reception can The conclusion here is that even for direct neighbors reception can
temporarily be bad during periods of several minutes. For a reliable temporarily be bad for periods of several minutes. For reliable and
and timely communication it is imperative to have at least two timely communication, it is imperative to have at least two
communication paths available (e.g. two hop paths next to the 1-hop communication paths available (e.g., two-hop paths next to the
path for direct neighbours). one-hop path for direct neighbors).
Acknowledgements
This document reflects discussions and remarks from several
individuals, including (in alphabetical order) Stephen Farrell, Mukul
Goyal, Sandeep Kumar, Jerry Martocci, Catherine Meadows, Yoshihiro
Ohba, Charles Perkins, Yvonne-Anne Pignolet, Michael Richardson, Ines
Robles, Zach Shelby, and Meral Sherazipour.
Authors' Addresses Authors' Addresses
Anders Brandt Anders Brandt
Sigma Designs Sigma Designs
Email: anders_Brandt@sigmadesigns.com Email: anders_Brandt@sigmadesigns.com
Emmanuel Baccelli Emmanuel Baccelli
INRIA INRIA
Email: Emmanuel.Baccelli@inria.fr Email: Emmanuel.Baccelli@inria.fr
Robert Cragie Robert Cragie
ARM Ltd. ARM Ltd.
110 Fulbourn Road 110 Fulbourn Road
Cambridge CB1 9NJ Cambridge CB1 9NJ
UK United Kingdom
Email: robert.cragie@arm.com
Email: robert.cragie@gridmerge.com
Peter van der Stok Peter van der Stok
Consultant Consultant
Email: consultancy@vanderstok.org Email: consultancy@vanderstok.org
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