Networking Working Group                                      A. Brandt
Internet Draft                                             Zensys, Inc.
Intended status: Informational                                 G. Porcu
Expires: January 2009                                    Telecom Italia
                                                     September 11, 2008

       Home Automation Routing Requirement in Low Power and Lossy

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Copyright Notice

   Copyright (C) The IETF Trust (2008).


   This document presents home control and automation application
   specific requirements for Routing Over Low power and Lossy
   networks (ROLL). In a modern home, a high number of wireless
   devices are used for a wide set of purposes. Examples include
   actuators (relay, light dimmer, heating valve), sensors (wall
   switch, water leak, blood pressure) and advanced controllers.
   Because such devices only cover a limited radio range, routing is

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   often required. The aim of this document is to specify the routing
   requirements for networks comprising such constrained devices in a
   home control and automation environment.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   in this document are to be interpreted as described in RFC-2119

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Table of Contents

   1. Introduction..................................................5
   2. Home Automation Applications..................................6
      2.1. Lighting Application In Action...........................6
      2.2. Energy Conservation and Optimizing Energy Consumption....6
      2.3. Moving a Remote Control Around...........................7
      2.4. Adding A New Module To The System........................7
      2.5. Controlling Battery Operated Window Shades...............8
      2.6. Remote Video Surveillance................................8
      2.7. Healthcare...............................................8
         2.7.1. At-home Health Reporting............................9
         2.7.2. At-home Health Monitoring...........................9
      2.8. Alarm Systems............................................9
   3. Unique Routing Requirements of Home Automation Applications..10
      3.1. Support of Groupcast....................................11
      3.2. Constraint-based Routing................................12
      3.3. Support of Mobility.....................................12
      3.4. Sleeping Nodes..........................................13
      3.5. Healthcare Routing......................................13
      3.6. Scalability.............................................13
      3.7. Convergence Time........................................14
      3.8. Manageability...........................................14
      3.9. Stability...............................................14
   4. Traffic Pattern..............................................14
   5. Open Issues..................................................15
   6. Security Considerations......................................15
   7. IANA Considerations..........................................15
   8. Acknowledgments..............................................15
   9. References...................................................16
      9.1. Normative References....................................16
      9.2. Informative References..................................17
   Disclaimer of Validity..........................................18


   ROLL:        Routing Over Low-power and Lossy networks
                  A ROLL node may be classified as sensor, actuator
                  or controller.

   Access Point: The access point is an infrastructure device that
                  connects a ROLL network to the Internet or some
                  backbone network.

   Actuator:     Network node which performs some physical action.
                  Dimmers and relays are examples of actuators.

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                  If sufficiently powered, actuator nodes may
                  participate in routing network messages.

   Channel:      Radio frequency band used to carry network packets.

   Controller:   Network node that controls actuators. Control
                  decisions may be based on sensor readings, sensor
                  events, scheduled actions or incoming commands from
                  the Internet or other backbone networks.
                  If sufficiently powered, controller nodes may
                  participate in routing network messages.

   Downstream:   Data direction traveling from a Local Area Network
                  (LAN) to a Personal Area Network (PAN) device.

   DR:          Demand-Response
                  The mechanism of users adjusting their power
                  consumption in response to actual pricing of power.

   DSM:         Demand Side Management
                  Process allowing power utilities to enable and
                  disable loads in consumer premises. Where DR relies
                  on voluntary action from users, DSM may be based on
                  enrollment in a formal program.

   LAN:         Local Area Network.

   PAN:         Personal Area Network.
                  A geographically limited wireless network based on
                  e.g. 802.15.4 or Z-Wave radio.

   PDA          Personal Digital Assistant. A small, handheld

   PLC          Power Line Communication

   RAM          Random Access Memory

   Sensor:      Network node that measures data and/or detects an
                  The sensor may generate a trap message to notify a
                  controller or directly activate an actuator.
                  If sufficiently powered, sensor nodes may
                  participate in routing network messages.

   Upstream:     Data direction traveling from a PAN to a LAN

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1. Introduction

   This document presents home control and automation application
   specific requirements for Routing Over Low power and Lossy
   networks (ROLL). In a modern home, a high number of wireless
   devices are used for a wide set of purposes. Examples include
   actuators (relay, light dimmer, heating valve), sensors (wall
   switch, water leak, blood pressure) and advanced controllers.
   Basic home control modules such as wall switches and plug-in
   modules may be turned into an advanced home automation solution
   via the use of an IP-enabled application responding to events
   generated by wall switches, motion sensors, light sensors, rain
   sensors, and so on.

   Network nodes may be sensors and actuators at the same time. An
   example is a wall switch for replacement in existing buildings.
   The push buttons may generate events for a controller node or for
   activating other actuator nodes. At the same time, a built-in
   relay may act as actuator for a controller or other remote

   Because ROLL nodes only cover a limited radio range, routing is
   often required. These devices are usually highly constrained in
   term of resources such as battery and memory and operate in
   unstable environments. Persons moving around in a house, opening
   or closing a door or starting a microwave oven affect the
   reception of weak radio signals. Reflection and absorption may
   cause a reliable radio link to turn unreliable for a period of
   time and then being reusable again, thus the term "lossy".

   Unlike other categories of PANs, the connected home area is very
   much consumer-oriented. The implication on network nodes is that
   devices are very cost sensitive, which leads to resource-
   constrained environments having slow CPUs and small memory
   footprints. At the same time, nodes have to be physically small
   which puts a limit to the physical size of the battery; and thus,
   the battery capacity. As a result, it is common for low-power
   sensor-style nodes to shut down radio and CPU resources for most
   of the time. The radio tends to use the same power for listening
   as for transmitting

   Section 2 describes a few typical use cases for home automation
   applications. Section 3 discusses the routing requirements for
   networks comprising such constrained devices in a home network
   environment. These requirements may be overlapping requirements
   derived from other application-specific routing requirements. A
   full list of requirements documents may be found in the end of the

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2. Home Automation Applications

   Home automation applications represent a special segment of
   networked devices with its unique set of requirements.
   Historically, such applications used wired networks or power line
   communication (PLC), but wireless solutions have emerged; allowing
   existing buildings to be upgraded more easily.

   To facilitate the requirements discussion in Section 3, this
   section lists a few typical use cases of home automation
   applications. New applications are being developed at a high pace
   and this section does not mean to be exhaustive. Most home
   automation applications tend to be running some kind of
   command/response protocol. The command may come from several

2.1. Lighting Application In Action

   A lamp may be turned on, not only by a wall switch but also by a
   movement sensor. The wall switch module may itself be a push-
   button sensor and an actuator at the same time. This will often be
   the case when upgrading existing buildings as existing wiring is
   not prepared for automation.

   One event may cause many actuators to be activated at the same
   Using the direct analogy to an electronic car key, a house owner
   may activate the "leaving home" function from an electronic house
   key, mobile phone, etc. For the sake of visual impression, all
   lights should turn off at the same time. At least, it should
   appear to happen at the same time. A well-known problem in
   wireless home automation is the "popcorn effect": Lamps are turned
   on one at a time, at a rate so slow that it is clearly visible.
   Some existing home automation solutions use a clever mix of a
   "subnet groupcast" message in direct range with no acknowledgement
   before sending acknowledged singlecast messages to each device.

   The controller forms the group and decides which nodes should
   receive a message.

2.2. Energy Conservation and Optimizing Energy Consumption

   In order to save energy, air conditioning, central heating, window
   shades etc. may be controlled by timers, motion sensors or
   remotely via internet or cell. Central heating may also be set to
   a reduced temperature during night time.

   The power grid may experience periods where more wind-generated
   power is produced than is needed. Typically this may happen during
   night hours.

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   In periods where electricity demands exceed available supply,
   appliances such as air conditioning, climate control systems,
   washing machines etc. can be turned off to avoid overloading the
   power grid.
   This is known as Demand-Side Management (DSM).
   Remote control of household appliances is well-suited for this

   The start/stop decision for the appliances can also be regulated
   by dynamic power pricing information obtained from the electricity
   utility companies. This method called Demand-Response (DR) works
   by motivation of users via pricing, bonus points, etc. For
   example, the washing machine and dish washer may just as well work
   while power is cheap. The electric car should also charge its
   batteries on cheap power.

   In order to achieve effective electricity savings, the energy
   monitoring application must guarantee that the power consumption
   of the ROLL devices is much lower than that of the appliance

   Most of these appliances are mains powered and are thus ideal for
   providing reliable, always-on routing resources. Battery-powered
   nodes, by comparison, are constrained routing resources and may
   only provide reliable routing under some circumstances.

2.3. Moving a Remote Control Around

   A remote control is a typical example of a mobile device in a home
   automation network. An advanced remote control may be used for
   dimming the light in the dining room while eating and later on,
   turning up the music while doing the dishes in the kitchen.
   Reaction must appear to be instant (within a few hundred
   milliseconds) even when the remote control has moved to a new
   location. The remote control may be communicating to either a
   central home automation controller or directly to the lamps and
   the media center.

2.4. Adding A New Module To The System

   Small-size, low-cost modules may have no user interface except for
   a single button. Thus, an automated inclusion process is needed
   for controllers to find new modules. Inclusion covers the
   detection of neighbors and assignment of a unique node ID.
   Inclusion should be completed within a few seconds.

   If assignment of unique addresses is performed by a central
   controller, it must be possible to route the inclusion request
   from the joining node to the central controller before the joining
   node has been included in the network.

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2.5. Controlling Battery Operated Window Shades

   In consumer premises, window shades are often battery-powered as
   there is no access to mains power over the windows. For battery
   conservation purposes, such an actuator node is sleeping most of
   the time. A controller sending commands to a sleeping actuator
   node via ROLL devices will have no problems delivering the packet
   to the nearest powered router, but that router may experience a
   delay until the next wake-up time before the command can be

2.6. Remote Video Surveillance

   Remote video surveillance is a fairly classic application for Home
   networking providing the ability for the end user to get a video
   stream from a Web Cam reached via the Internet. The video stream
   may be triggered by the end-user after receiving an alarm from a
   sensor (movement or smoke detector) or the user simply wants to
   check the home status via video.
   Note that in the former case, more than likely, there will be a
   form of inter-device communication: Upon detecting some movement
   in the home, the movement sensor may send a request to the light
   controller to turn on the lights, to the Web Cam to start a video
   stream that would then be directed to the end user's cell phone or
   Personal Digital Assistant (PDA) via the Internet.
   In contrast to other applications, e.g. industrial sensors, where
   data would mainly be originated by sensor to a sink and vice
   versa, this scenario implicates a direct inter-device
   communication between ROLL devices.

2.7. Healthcare

   By adding communication capability to devices, patients and
   elderly citizens may be able to do simple measurements at home.
   Thanks to online devices, a doctor can keep an eye on the
   patient's health and receive warnings if a new trend is discovered
   by automated filters.

   Fine-grained daily measurements presented in proper ways may allow
   the doctor to establish a more precise diagnosis.

   Such applications may be realized as wearable products which
   frequently do a measurement and automatically deliver the result
   to a data sink locally or over the Internet.

   Applications falling in this category are referred to as at-home
   health reporting. Whether measurements are done in a fixed
   interval or if they are manually activated, they leave all
   processing to the receiving data sink.

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   A more active category of applications may send an alarm if some
   alarm condition is triggered. This category of applications is
   referred to as at-home health monitoring. Measurements are
   interpreted in the device and may cause reporting of an event if
   an alarm is triggered.

   Many implementations may overlap both categories.

2.7.1. At-home Health Reporting

   Applications might include:

   o  Temperature
   o  Weight
   o  Blood pressure
   o  Insulin level

   Measurements may be stored for long term statistics. At the same
   time, a critically high blood pressure may cause the generation of
   an alarm report. Refer to 2.7.2.

   To avoid a high number of request messages, nodes may be
   configured to autonomously do a measurement and send a report in

2.7.2. At-home Health Monitoring

   An alarm event may become active e.g. if the measured blood
   pressure exceeds a threshold or if a person falls to the ground.
   Alarm conditions must be reported with the highest priority and

   Applications might include:

   o  Temperature
   o  Weight
   o  Blood pressure
   o  Insulin level
   o  Electrocardiogram (ECG)
   o  Position tracker

2.8. Alarm Systems

   A home security alarm system is comprised of various sensors
   (vibration, fire or carbon monoxide, door/window, glass-break,
   presence, panic button, etc.).

   Some smoke alarms are battery powered and at the same time mounted
   in a high place. Battery-powered safety devices should only be
   used for routing if no other alternatives exist to avoid draining
   the battery. A smoke alarm with a drained battery does not provide

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   a lot of safety. Also, it may be inconvenient to exchange battery
   in a smoke alarm.

   Alarm system applications may have both a synchronous and an
   asynchronous behavior; i.e. they may be periodically queried by a
   central control application (e.g. for a periodical refreshment of
   the network state), or send a message to the control application
   on their own initiative.

   When a node (or a group of nodes) identifies a risk situation
   (e.g. intrusion, smoke, fire), it sends an alarm message to a
   central controller that could autonomously forward it via Internet
   or interact with other network nodes (e.g. try to obtain more
   detailed information or ask other nodes close to the alarm event).

   Finally, routing via battery-powered nodes may be very slow if the
   nodes are sleeping most of the time (they could appear
   unresponsive to the alarm detection). To ensure fast message
   delivery and avoid battery drain, routing should be avoided via
   sleeping devices.

3. Unique Routing Requirements of Home Automation Applications

   Home automation applications have a number of specific routing
   requirements related to the set of home networking applications
   and the perceived operation of the system.

   The relations of use cases to requirements are outlined in the
   table below:

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   +------------------------------- +-----------------------------+
   | Use case                       | Requirement                 |
   +------------------------------- +-----------------------------+
   |2.1. Lighting Application In    |3.1. Support of Groupcast    |
   |Action                          |3.3. Support of Mobility     |
   |                                |3.6. Scalability             |
   +------------------------------- +-----------------------------+
   |2.2. Energy Conservation and    |3.2. Constraint-based Routing|
   |Optimizing Energy Consumption   |                             |
   +------------------------------- +-----------------------------+
   |2.3. Moving a Remote Control    |3.3. Support of Mobility     |
   |Around                          |3.7. Convergence Time        |
   +------------------------------- +-----------------------------+
   |2.4. Adding A New Module To The |3.7. Convergence Time        |
   |System                          |3.8. Manageability           |
   +------------------------------- +-----------------------------+
   |2.5. Controlling Battery        |3.4. Sleeping Nodes          |
   |Operated Window Shades          |                             |
   +------------------------------- +-----------------------------+
   |2.7. Healthcare                 |3.2. Constraint-based Routing|
   |                                |3.3. Support of Mobility     |
   |                                |3.5. Healthcare Routing      |
   |                                |3.7. Convergence Time        |
   +------------------------------- +-----------------------------+
   |2.8. Alarm Systems              |3.6. Scalability             |
   |                                |3.7. Convergence Time        |
   +------------------------------- +-----------------------------+

3.1. Support of Groupcast

   | Author's note:                                           |
   | The support of groupcast only has implication on the     |
   | addressing scheme and as such, it is outside the scope   |
   | of this document that focuses on routing requirements.   |
   | Nevertheless, it is an important parameter for the       |
   | definition of the ROLL layer interface towards various   |
   | layer two technologies for home control.                 |
   |                                                          |
   | Should a dedicated application-specific document be      |
   | created for such details?                                |

   Groupcast, in the context of home automation, is defined as the
   ability to simultaneously transmit a message to a group of
   recipients without prior interaction with the group members (i.e.
   group setup). A use-case for groupcast is given in Section 2.1.

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   Broadcast and groupcast in home automation MAY be used to achieve
   simultaneous reaction from a group of nodes.

   It SHOULD be to possible to address a group of receivers known by
   the sender even if the receivers do not know that they have been
   grouped by the sender.

3.2. Constraint-based Routing

   For convenience and low operational costs, power consumption of
   consumer products must be kept at a very low level to achieve a
   long battery lifetime. One implication of this fact is that Random
   Access Memory (RAM) is limited and it may even be powered down;
   leaving only a few 100 bytes of RAM alive during the sleep phase.

   The use of battery powered devices reduces installation costs and
   does enable installation of devices even where main power lines
   are not available. On the other hand, in order to be cost
   effective and efficient, the devices have to maximize the sleep
   phase with a duty cycle lower than 1%.

   Some devices only wake up in response to an event, e.g. a push

   Simple battery-powered nodes such as movement sensors on garage
   doors and rain sensors may not be able to assist in routing.
   Depending on the node type, the node never listens at all, listens
   rarely or makes contact on demand to a pre-configured target node.
   Attempting to communicate to such nodes may at best require long
   time before getting a response.

   Other battery-powered nodes may have the capability to participate
   in routing. The routing protocol SHOULD route via mains-powered
   nodes if possible.

   The routing protocol MUST support constraint-based routing taking
   into account node properties (CPU, memory, level of energy, sleep
   intervals, safety/convenience of changing battery).

3.3. Support of Mobility

   In a home environment, although the majority of devices are fixed
   devices, there is still a variety of mobile devices: for example a
   multi-purpose remote control is likely to move. Another example of
   mobile devices is wearable healthcare devices.

   While healthcare devices delivering measurement results can
   tolerate route discovery times measured in seconds, a remote
   control appears unresponsive if using more than 0.5 seconds to
   e.g. pause the music.

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   While, in theory, all battery-powered devices and mains-powered
   plug-in modules may be moved, the predominant case is that the
   sending node has moved while the rest of the network has not

   The routing protocol MUST provide mobility with convergence time
   below 0.5 second if only the sender has moved.

   A non-responsive node can either be caused by 1) a failure in the
   node, 2) a failed link on the path to the node or 3) a moved node.
   In the first two cases, the node can be expected to reappear at
   roughly the same location in the network, whereas it can return
   anywhere in the network in the latter case.

3.4. Sleeping Nodes

   Sleeping nodes may appear to be non-responsive. The routing
   protocol MUST take into account the delivery time to a sleeping
   target node.

   The wake-up interval of a sleeping node MUST be less than one

3.5. Healthcare Routing

   Because most health care applications may run on battery, this
   leads to specific requirements for the routing protocol. Most
   health care applications may also be portable and therefore need
   to locate a new neighbor router on a frequent basis.
   Not being powered most of the time, the nodes should not be used
   as routing nodes. However, battery-powered nodes may be involved
   in routing. Examples include cases where a person falls during a
   power blackout. In that case it may be that no mains-powered
   routers are available for forwarding the alarm message to a
   (battery-backed) internet gateway located out of direct range.

   Delivery of measurement data has a more relaxed requirement for
   route discovery time compared to a remote control. On the other
   hand, it is critical that a "person fell" alarm is actually

3.6. Scalability

   Looking at the number of wall switches, power outlets, sensors of
   various nature, video equipment and so on in a modern house, it
   seems quite realistic that hundreds of low power devices may form
   a home automation network in a fully populated "smart" home.
   Moving towards professional building automation, the number of
   such devices may be in the order of several thousands.

   The routing protocol MUST support 250 devices in the network.

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3.7. Convergence Time

   A wireless home automation network is subject to various
   instabilities due to signal strength variation, moving persons and
   the like. Furthermore, as the number of devices increases, the
   probability of a node failure also increases.

   Measured from the transmission of a packet, the following
   convergence time requirements apply.

   The routing protocol MUST converge within 0.5 second if no nodes
   have moved.

   The routing protocol MUST converge within 2 seconds if the
   destination node of the packet has moved.

   In both cases, "converge" means "the originator node has received
   a response from the destination node".

3.8. Manageability

   The ability of the home network to support auto-configuration is
   of the utmost importance. Indeed, most end users will not have the
   expertise and the skills to perform advanced configuration and
   troubleshooting. Thus the routing protocol designed for home
   automation networks MUST provide a set of features including zero-
   configuration of the routing protocol for a new node to be added
   to the network. From a routing perspective, zero-configuration
   means that a node can obtain an address and join the network on
   its own, without human intervention.

3.9. Stability

   The routing protocol MUST support the ability to isolate a
   misbehaving node thus preserving the correct operation of the
   overall network.

4. Traffic Pattern

   Depending on the design philosophy of the home network, wall
   switches may be configured to directly control individual lamps or
   alternatively, all wall switches send control commands to a
   central lighting control computer which again sends out control
   commands to relevant devices.

   In a distributed system, the traffic tends to be multipoint-to-
   multipoint. In a centralized system, it is a mix of multipoint-to-
   point and point-to-multipoint.

   Wall switches only generate traffic when activated, which
   typically happens from a one to tens of times per hour.

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   Remote controls have a similar transmit pattern to wall switches,
   but are activated more frequently.

   Temperature/air pressure/rain sensors send frames when queried by
   the user or can be preconfigured to send measurements at fixed
   intervals (typically minutes). Motion sensors typically send a
   frame when motion is first detected and another frame when an idle
   period with no movement has elapsed. The highest transmission
   frequency depends on the idle period used in the sensor.
   Sometimes, a timer will trigger a frame transmission when an
   extended period without status change has elapsed.

   All frames sent in the above examples are quite short, typically
   less than 5 bytes of payload. Lost frames and interference from
   other transmitters may lead to retransmissions. In all cases,
   acknowledgment frames with a size of a few bytes are used.

5. Open Issues

   Other items to be addressed in further revisions of this document

   o  Load Balancing (Symmetrical and Asymmetrical)
   o  Groupcast definition in a separate document? (TBD)
   o  Use case: Home Control Installer Scenario
   o  Security

6. Security Considerations

   Implementing security mechanisms in ROLL network devices may
   degrade energy efficiency and increase cost.

   The routing protocol chosen for ROLL MUST allow for low-power,
   low-cost network devices with limited security needs.

   Protection against unintentional inclusion in neighboring networks
   MUST be provided.

7. IANA Considerations

   This document includes no request to IANA.

8. Acknowledgments

   J. P. Vasseur, Jonathan Hui, Eunsook "Eunah" Kim, Mischa Dohler
   and Massimo Maggiorotti are gratefully acknowledged for their
   contributions to this document.

   This document was prepared using

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9. References

   As an exception, this internet draft contains references to other
   internet drafts. The reason is that the referenced internet drafts
   are developed in parallel to this document.

   When promoted to an RFC, the references MUST be updated to RFCs as
   well or removed from the references section.

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.





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9.2. Informative References

Author's Addresses

   Anders Brandt
   Zensys, Inc.
   Emdrupvej 26
   Copenhagen, DK-2100


   Jakob Buron
   Zensys, Inc.
   Emdrupvej 26
   Copenhagen, DK-2100


   Giorgio Porcu
   Telecom Italia
   Piazza degli Affari, 2
   20123 Milan


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Internet-Draft    draft-ietf-roll-home-routing-reqs      September 2008

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