wdiff draft-brandt-roll-rpl-applicability-home-building-02.txt draft-brandt-roll-rpl-applicability-home-building-03.txt

Roll A. Brandt
Internet-Draft Sigma Designs
Intended status: Informational E. Baccelli
Expires: November 30, 2012 August 9, 2013 INRIA
R. Cragie
Gridmerge
May 29, 2012
February 5, 2013

Applicability Statement: The use of RPL RPL-P2P in Building and Home
Environments
draft-brandt-roll-rpl-applicability-home-building-02 and Building Control
draft-brandt-roll-rpl-applicability-home-building-03

Abstract

The purpose of this document is to to provide guidance in the use of
RPL
RPL-P2P to provide implement the features required in building or home
environments, two application spaces which share a substantial number
of requirements. Note that this document refers to a specific
revision of the RPL draft, and thus, a new revision of the RPL draft
will likely necessitate a new revision of this document. home
environments.

Status of this Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on November 30, 2012. August 9, 2013.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement 4
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Overview of requirements . . . . . . 3
2.1. Risk of undesired long P2P routes . . . . . . . . . . . 4
1.3. Out of scope requirements . . . . . 3
2.1.1. Traffic concentration at the root . . . . . . . . . . . 4
2.1.2. Excessive battery consumption in source nodes
2. Deployment Scenario . . . . . . . . . . . . . . . . . . . . . 4
2.1. Network Topologies . . . . . . . . . . . . . . . . . . . . 5
2.2. Risk of delayed route repair Traffic Characteristics . . . . . . . . . . . . . . . 4 . . 5
2.2.1. Broken service Human user responsiveness . . . . . . . . . . . . . . 5
2.2.2. Source-sink (SS) communication paradigm . . . . . . 4 . 6
2.2.3. Peer-to-peer (P2P) communication paradigm . . . . . . 6
2.2.4. Peer-to-multipeer (P2MP) communication paradigm . . . 6
2.3. Link layer applicability . . . . . . . . . . . . . . . . . 6
3. IANA Using RPL-P2P to meet requirements . . . . . . . . . . . . . . 7
4. RPL Profile for RPL-P2P . . . . . . . . . . . . . . . . . . . 7
4.1. RPL Features . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. RPL Instances . . . . . . . . . . . . . . . . . . . . 7
4.1.2. Non-Storing Mode . . . . . . . . . . . . . . . . . . . 7
4.1.3. DAO Policy . . . . . . . . . . . . . . . . . . . . . . 8
4.1.4. Path Metrics . . . . . . . . . . . . . . . . . . . . . 8
4.1.5. Objective Function . . . . . . . . . . . . . . . . . . 8
4.1.6. DODAG Repair . . . . . . . . . . . . . . . . . . . . . 8
4.1.7. Multicast . . . . . . . . . . . . . . . . . . . . . . 8
4.1.8. Security . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.9. P2P communications . . . . . . . . . . . . . . . . . . 8
4.2. Layer 2 features . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Security functions provided by layer-2 . . . . . . . . 8
4.2.2. 6LowPAN options assumed . . . . . . . . . . . . . . . 9
4.2.3. MLE and other things . . . . . . . . . . . . . . . . . 9
4.3. Recommended Configuration Defaults and Ranges . . . . . . 9
5. Manageability Considerations . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . 5
4. . . . . . . . . . . . . 9
6.1. Security Considerations during initial deployment . . . . 9
6.2. Security Considerations during incremental deployment . . 9
7. Other related protocols . . . . . . . . . . . . . . 5
5. Informative . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . 5 . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgements RPL shortcomings in home and building deployments . . 11
A.1. Risk of undesired long P2P routes . . . . . . . . . . . . 11
A.1.1. Traffic concentration at the root . . . . . 5 . . . . . 12
A.1.2. Excessive battery consumption in source nodes . . . . 12
A.2. Risk of delayed route repair . . . . . . . . . . . . . . . 12
A.2.1. Broken service . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 13

1. Introduction

Home automation and building control application spaces share a
substantial number of properties. The purpose of this document is to to provide
give guidance in the use of
RPL [RPL-15] RPL-P2P to provide the features required both
by [HOME-REQ] the requirements documents "Home Automation Routing Requirements
in Low-Power and
by [BUILDING-REQ] , as these two application spaces share a
substantial number of requirements. Note that Lossy Networks" [RFC5826] and "Building Automation
Routing Requirements in Low-Power and Lossy Networks" [RFC5867].

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document refers are to be interpreted as described in RFC 2119.

1.2. Overview of requirements

Applicable requirements are described in [RFC5826] and [RFC5867].

1.3. Out of scope requirements

The considered network diameter is limited to a specific revision max diameter of the RPL draft, 10
hops and thus, a new revision typical diameter of 5 hops, which captures the RPL draft will likely necessitate most common
cases in home automation and building control networks.

This document does not consider the applicability of RPL-related
specifications for urban and industrial applications [RFC5548],
[RFC5673], which may exhibit significantly larger network diameters.

2. Deployment Scenario

A typical home automation network is less than 100 nodes. Large
building deployments may span 10,000 nodes but to ensure
uninterrupted service of light and air conditioning systems in
individual zones of the building, nodes are organized in subnetworks.
Each subnetwork in a new revision building automation deployment is typically less
than 200 nodes and rarely more than 500 nodes.

The main purpose of this
document. RPL provides multipoint-to-point (MP2P) paths from the network is to provide control over light and
heating/cooling resources. User intervention may be enabled via wall
controllers combined with movement, light and temperature sensors to
enable automatic adjustment of window blinds, reduction of room
temperature, etc.

Alarm systems are also important applications in home and building
networks.

2.1. Network Topologies

The typical home automation network or building control subnetwork is
a sink, along mesh network with a DAG; an advanced tree structure for organising border router located at a convenient place in
the home. In a building control network nodes there may be several
redundant border routers. The network often consists in a loop-free topology with backup number of
overlapping wireless subnetworks. Two types of routing topologies
may exist in each subnetwork (i) a tree-shaped collection of routes
spanning from a central building controller via the border router, on
to destination nodes in the subnetwork, and/or (ii) a flat, un-
directed collection of intra-network routes between arbitrary nodes
in the subnetwork.

Nodes in Home and
potential support Building automation networks are typically
inexpensive devices with extremely low memory capacities, such as
individual wall switches. Only a few nodes (such as multi-purpose
remote controls for policy-based routing. instance) are more expensive devices, which can
afford more memory capacity.

2.2. Traffic Characteristics

Traffic may enter the network from a central controller or it may
originate from an intra-network node, such as a wall switch. The root
majority of the DAG traffic is light-weight point-to-point control style;
e.g. Put-Ack or Get-Response. There are however exceptions. Bulk
data transfer is used for firmware update and logging. Multicast is
used for service discovery or to control groups of nodes, such as
light fixtures. Firmware updates enter the sink, network while logs leave
the network.

2.2.1. Human user responsiveness

While airconditioning and sensors discover other environmental-control applications
may accept certain response delays, alarm and maintain light control
applications may be regarded as soft real-time systems. A slight
delay is acceptable, but the DAG via perceived quality of service degrades
significantly if response times exceed 250 msec. If the light does
not turn on at short notice, a user will activate the
dissemination controls again,
causing a sequence of DIO signaling, initiated commands such as Light{on,off,on,off,..} or
Volume{up,up,up,up,up,...}.

The reactive discovery features of RPL-P2P ensures that commands are
normally delivered within the 250msec time window and when
connectivity needs to be restored, it is typically completed within
seconds.

2.2.2. Source-sink (SS) communication paradigm

Source-sink (SS) traffic is a common traffic type in home and
building networks. The traffic is generated by environmental sensors
which push periodic readings to a central server. The readings may
be used for pure logging, or more often, to adjust light, heating and
ventilation. Alarm sensors also generate SS style traffic.

With regards to message latency, most SS transmissions can tolerate
worst-case delays measured in tens of seconds. Alarm sensors,
however, represent one exception.

2.2.3. Peer-to-peer (P2P) communication paradigm

Peer-to-peer (P2P) traffic is a common traffic type in home networks.
Some building networks also rely on P2P traffic while others send all
control traffic to a local controller box for advanced scene and
group control; thus generating more SS and P2MP traffic.

P2P traffic is typically generated by remote controls and wall
controllers which push control messages directly to light or heat
sources. P2P traffic has a strong requirement for low latency since
P2P traffic often carries application messages that are invoked by
humans. As mentioned in Section 2.2.1 application messages need to
be delivered within less than a second - even when a route repair is
needed before the root. Conversely,
RPL provides point-to-multippoint message can be delivered.

2.2.4. Peer-to-multipeer (P2MP) paths from the root communication paradigm

Peer-to-multipeer (P2MP) traffic is common in home and building
networks. Often, a wall switch in a living room responds to user
activation by sending commands to a number of light sources
simultaneously.

Individual wall switches are typically inexpensive devices with
extremely low memory capacities. Multi-purpose remote controls for
use in a home environment typically have more memory but such devices
are asleep when there is no user activity. RPL-P2P reactive
discovery allows a node to wake up and find new routes within a few
seconds while memory constrained nodes
along only have to keep routes to
relevant targets.

2.3. Link layer applicability

This document applies to [IEEE802.15.4] and [G.9959] which are
adapted to IPv6 by the same DAG. RPL also provide point-to-point (P2P) paths from
node adaption layers [RFC4944] and [I-D.lowpanz].

Due to node, through the first ancestor along limited memory of a majority of devices (such as
individual light-switches) RPL-P2P MUST be used with source routing
in non-storing mode. The abovementioned adaptation layers leverage
on the DAG, that is
common compression capabilities of [RFC6554] and [RFC6282]. Header
compression allows small IP packets to both fit into a single layer 2
frame even when source routing is used. A network diameter limited
to 5 hops helps achieving this.

Packet drops are often experienced in the targeted environments.
ICMP, UDP and destination nodes. Such paths even TCP flows may benefit from link layer unicast
acknowledgments and retransmissions. Link layer unicast
acknowledgments MUST be enabled when [IEEE802.15.4] or [G.9959] is
used with RPL-P2P.

3. Using RPL-P2P to meet requirements

RPL-P2P MUST be used in home and building networks, as P2P traffic is
substantial and route repair must be completed within seconds. RPL-
P2P provides a reactive mechanism for quick, efficient and root-
independent route discovery/repair. The use of RPL-P2P furthermore
allows data traffic to avoid having to go through a central region
around the root of the tree, and drastically reduces path length
[SOFT11] [INTEROP12]. These characteristics are
discovered desirable in home
and maintained via building automation networks because they substantially decrease
unnecessary network congestion around the tree's root.

4. RPL Profile for RPL-P2P

RPL-P2P MUST be used in home and building networks. Non-storing mode
allows for constrained memory in repeaters when source routing is
used. Reactive discovery allows for low application response times
even when on-the-fly route repair is needed.

4.1. RPL Features

4.1.1. RPL Instances

TBD.

4.1.2. Non-Storing Mode

Non-storing mode MUST be used to cope with the extremely constrained
memory of a majority of nodes in the network (such as individual
light switches).

4.1.3. DAO signaling, initiated Policy

TBD.

4.1.4. Path Metrics

TBD.

4.1.5. Objective Function

OF0 MUST be supported and is the RECOMMENDED OF to use. Other
Objective Functions MAY be used as well.

4.1.6. DODAG Repair

Since RPL-P2P only creates DODAGs on a temporary basis during route
repair, there is no need to repair DODAGs.

4.1.7. Multicast

TBD.

4.1.8. Security

TBD.

4.1.9. P2P communications

RPL-P2P [RPL-P2P] MUST be used to accomodate P2P traffic, which is
typically substantial in home and building automation networks.

4.2. Layer 2 features

Security MUST be applied at layer 2 for [IEEE802.15.4] and [G.9959].
Residential light control can accept a lower security level than
other contexts (e.g. a nuclear research lab). Safety critical
devices like electronic door locks SHOULD employ additional higher-
layer security while light and heating devices may be sufficiently
protected by a single network key. The border router MAY enforce
access policies to limit access to the
destination node.

2. Problem Statement trusted LLN domain from the
LAN.

4.2.1. Security functions provided by layer-2

TBD.

4.2.2. 6LowPAN options assumed

TBD.

4.2.3. MLE and other things

TBD.

4.3. Recommended Configuration Defaults and Ranges

TODO

5. Manageability Considerations

TODO

6. Security Considerations

TODO

6.1. Security Considerations during initial deployment

TODO: (This section explains how nodes get their initial trust
anchors, initial network keys. It explains if this happens at the
factory, in a deployment truck, if it is done in the field, perhaps
like http://www.lix.polytechnique.fr/hipercom/SmartObjectSecurity/
papers/CullenJennings.pdf)

6.2. Security Considerations during incremental deployment

TODO: (This section explains how that replaces a failed node takes on
the dead nodes' identity, or not. How are nodes retired. How are
nodes removed if they are compromised)

7. Other related protocols

Application transport protocols may be CoAP over UDP or equivalents.
Typically, UDP is used for IP transport to keep down the application
response time and bandwidth overhead.

Several features required by [HOME-REQ] and by [BUILDING-REQ] [RFC5826], [RFC5867] challenge the P2P
paths provided by RPL [RPL-15]. This section RPL. Appendix A reviews these challenges. In some
cases, a sensor node may need to spontaneously initiate the discovery and mainten of a
path towards a desired destination that is neither the root of a DAG,
nor a destination originating DAO signaling. This feature is absent from
the RPL for now. Furthermore, provided P2P paths
provided by RPL are not satisfactory in some all cases because they
involve too many intermediate
sensors nodes before reaching destination, which the destination.

RPL-P2P [RPL-P2P] provides the features requested by [RFC5826] and
[RFC5867]. RPL-P2P uses a subset of the frame formats and features
defined for RPL [RFC6550] but may be an issue in terms
of energy or delay constraints. combined with RPL does not provide a mechanism frame flows in
advanced deployments.

8. IANA Considerations

9. Acknowledgements

This document reflects discussions and remarks from several
individuals including (in alphabetical order): Michael Richardson,
Mukul Goyal, Jerry Martocci, Charles Perkins, and Zach Shelby

10. References

11. References

11.1. Normative References

[RFC5826] "Home Automation Routing Requirements in Low-Power and
Lossy Networks".

[RFC5867] "Building Automation Routing Requirements in Low-Power and
Lossy Networks".

[RFC5673] "Industrial Routing Requirements in Low-Power and Lossy
Networks".

[RFC5548] "Routing Requirements for
discovering Urban Low-Power and maintaining more efficient alternative P2P paths when
they are available. These deficiencies call Lossy
Networks".

[IEEE802.15.4]
"IEEE 802.15.4 - Standard for Local and metropolitan area
networks -- Part 15.4: Low-Rate Wireless Personal Area
Networks", <IEEE Standard 802.15.4>.

[RFC4944] "Transmission of IPv6 Packets over IEEE 802.15.4
Networks".

[G.9959] "ITU-T G.9959 Short range narrow-band digital
radiocommunication transceivers - PHY and MAC layer
specifications", <ITU-T G.9959>.

[I-D.lowpanz]
Brandt, A., "Transmission of IPv6 Packets over ITU-T
G.9959 Networks", <draft-brandt-6man-lowpanz>.

[RFC6282] Hui, J. and Thubert, P., "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC6282 ,
September 2011.

[RFC6554] Hui, J., Vasseur, JP., Culler, D., and Manral, V., "An
IPv6 Routing Header for Source Routes with the specification,
within RPL, Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC6554 , March 2012.

[RFC6550] "RPL: IPv6 Routing Protocol for Low-Power and Lossy
Networks".

[RPL-P2P] Goyal, M., Baccelli, E., Phillip, M., Brandt, A., and J.
Martocci, "Reactive Discovery of Point-to-Point Routes in
Low Power and Lossy Networks", draft-ietf-roll-p2p-rpl ,
May 2012.

11.2. Informative References

[SOFT11] Baccelli, E., Phillip, M., and M. Goyal, "The P2P-RPL
Routing Protocol for IPv6 Sensor Networks: Testbed
Experiments", Proceedings of complementary mechanisms which will help alleviate the
challenges described below.

2.1. Conference on Software
Telecommunications and Computer Networks, Split, Croatia,
September 2011., September 2011.

[INTEROP12]
Baccelli, E., Phillip, M., Brandt, A., Valev , H., and J.
Buron , "Report on P2P-RPL Interoperability Testing", RR-
7864 INRIA Research Report RR-7864, Janurary 2012.

Appendix A. RPL shortcomings in home and building deployments

This document reflects discussions and remarks from several
individuals including (in alphabetical order): Charles Perkins, Jerry
Martocci, Michael Richardson, Mukul Goyal and Zach Shelby.

A.1. Risk of undesired long P2P routes

The DAG, being a tree structure is formed from a root. If nodes
residing in different branches have a need for communicating
internally, DAG mechanisms provided in RPL [RPL-15] [RFC6550] will propagate
traffic towards the root, potentially all the way to the root, and
down along another branch. In a typical example two nodes could
reach each other via just two router nodes but in unfortunate cases,
RPL [RPL-15] may send traffic three hops up and three hops down again. This
leads to several undesired phenomena described in the following
sections

2.1.1.

A.1.1. Traffic concentration at the root

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
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
RF power downwards its subtree but just as much upwards towards the
root; potentially jamming other MP2P traffic leaving the tree or
preventing the root of the DAG from sending P2MP traffic into the DAG
because the listen-before-talk link-layer protection kicks in.

2.1.2.

A.1.2. Excessive battery consumption in source nodes

Battery-powered nodes originating P2P traffic depend on the route
length. Long routes cause source nodes to stay awake for longer
periods before returning to sleep. Thus, a longer route translates
proportionally (more or less) into higher battery consumption.

2.2.

A.2. Risk of delayed route repair

The RPL DAG mechanism uses DIO and DAO messages to monitor the health
of the DAG. In rare occasions, changed radio conditions may render
routes unusable just after a destination node has returned a DAO
indicating that the destination is reachable. Given enough time, the
next Trickle timer-controlled DIODAO update will eventually repair
the broken routes. In a worst-case event this is however too late.
In an apparently stable DAG, 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 the time interval between the last DAO
message was issued the destination module and the time one of the
parents sends the next DIO, the destination cannot be reached.
Nothing in RPL [RPL-15] kicks in to restore connectivity in a reactive
fashion. The consequence is a broken service in home and building
applications.

2.2.1.

A.2.1. Broken service

Experience from the telecom industry shows that if the voice delay
exceeds 250ms users start getting confused, frustrated andor 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 again,
causing a sequence of commands such as Light{on,off,off,on,off,..} or
Volume{up,up,up,up,up,...} Whether the outcome is nothing or some
unintended response this is unacceptable. A controlling system must
be able to restore connectivity to recover from the error situation.
Waiting for an unknown period of time is not an option. While this
issue was identified during the P2P analysis it applies just as well
to application scenarios where an IP application outside the LLN
controls actuators, lights, etc.

3. IANA Considerations

This document has no actions for IANA.

4. Security Considerations

This document does not have to any security considerations.

5. Informative References

[HOME-REQ]
Brandt, A., Buron, J., and G. Porcu, "Home Automation
Routing Requirements in Low Power and Lossy Networks",
RFC5826 .

[BUILDING-REQ]
Martocci, J., De Mil, P., Vermeylen, W., and N. Riou,
"Building Automation Routing Requirements in Low Power and
Lossy Networks", RFC5867 .

[RPL-15] Winter, T. and P. Thubert, "RPL: IPv6 Routing Protocol for
Low power and Lossy Networks", draft-ietf-roll-rpl-15 ,
2010.

Appendix A. Acknowledgements

This document reflects discussions and remarks from several
individuals including (in alphabetical order): Mukul Goyal, Jerry
Martocci, Charles Perkins, and Zach Shelby.

Authors' Addresses

Anders Brandt
Sigma Designs

Email: abr@sdesigns.dk

Emmanuel Baccelli
INRIA

Email: Emmanuel.Baccelli@inria.fr

Robert Cragie
Gridmerge

Email: robert.cragie@gridmerge.com