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rfc:rfc5826

Internet Engineering Task Force (IETF) A. Brandt Request for Comments: 5826 J. Buron Category: Informational Sigma Designs, Inc. ISSN: 2070-1721 G. Porcu

                                                        Telecom Italia
                                                            April 2010
Home Automation Routing Requirements in Low-Power and Lossy Networks

Abstract

 This document presents requirements specific to home control and
 automation applications for Routing Over Low power and Lossy (ROLL)
 networks.  In the near future, many homes will contain high numbers
 of wireless devices for a wide set of purposes.  Examples include
 actuators (relay, light dimmer, heating valve), sensors (wall switch,
 water leak, blood pressure), and advanced controllers (radio-
 frequency-based AV remote control, central server for light and heat
 control).  Because such devices only cover a limited radio range,
 routing is 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.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 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/rfc5286.

Brandt, et al. Informational [Page 1] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

Copyright Notice

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 document authors.  All rights reserved.
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 Provisions Relating to IETF Documents
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 Contributions published or made publicly available before November
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 material may not have granted the IETF Trust the right to allow
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 Without obtaining an adequate license from the person(s) controlling
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 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Brandt, et al. Informational [Page 2] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

Table of Contents

 1. Introduction ....................................................3
    1.1. Terminology ................................................4
    1.2. Requirements Language ......................................6
 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 .................................................9
         2.7.1. At-Home Health Reporting ...........................10
         2.7.2. At-Home Health Monitoring ..........................10
    2.8. Alarm Systems .............................................10
 3. Unique Routing Requirements of Home Automation Applications ....11
    3.1. Constraint-Based Routing ..................................12
    3.2. Support of Mobility .......................................12
    3.3. Scalability ...............................................13
    3.4. Convergence Time ..........................................13
    3.5. Manageability .............................................14
    3.6. Stability .................................................14
 4. Traffic Pattern ................................................14
 5. Security Considerations ........................................15
 6. Acknowledgments ................................................16
 7. References .....................................................16
    7.1. Normative References ......................................16
    7.2. Informative References ....................................17

1. Introduction

 This document presents requirements specific to home control and
 automation applications for Routing Over Low power and Lossy (ROLL)
 networks.  In the near future, many homes will contain high numbers
 of wireless devices 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 homes.  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 sensors.

Brandt, et al. Informational [Page 3] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 Because ROLL nodes only cover a limited radio range, routing is often
 required.  These devices are usually highly constrained in terms 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 become reusable
 again, thus the term "lossy".  All traffic in a ROLL network is
 carried as IPv6 packets.
 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 battery-operated, 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.
 Although this document focuses its text on radio-based wireless
 networks, home-automation networks may also operate using a variety
 of links, such as IEEE 802.15.4, Bluetooth, Low-Power WiFi, wired or
 other low-power PLC (Power-Line Communication) links.  Many such low-
 power link technologies share similar characteristics with low-power
 wireless and this document should be regarded as applying equally to
 all such links.
 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
 presented in [BUILDING-REQS], [RFC5673], and [RFC5548].
 A full list of requirements documents may be found in Section 7.

1.1. Terminology

 ROLL:          Routing Over Low-power and Lossy networks.  A ROLL
                node may be classified as a sensor, actuator, or
                controller.
 Actuator:      Network node that performs some physical action.
                Dimmers and relays are examples of actuators.  If
                sufficiently powered, actuator nodes may participate
                in routing network messages.

Brandt, et al. Informational [Page 4] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 Border router: Infrastructure device that connects a ROLL network to
                the Internet or some backbone network.
 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 the 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.
 LLNs:          Low-Power and Lossy Networks.
 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
                computer.
 PLC            Power-Line Communication.
 RAM            Random Access Memory.
 Sensor:        Network node that measures some physical parameter
                and/or detects an event.  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 device.

Brandt, et al. Informational [Page 5] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 Refer to the ROLL terminology reference document [ROLL-TERM] for a
 full list of terms used in the IETF ROLL WG.

1.2. Requirements Language

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

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 homes 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 places.

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 homes as existing wiring is not prepared for
 automation.
 One event may cause many actuators to be activated at the same time.
 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.

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 nighttime.

Brandt, et al. Informational [Page 6] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 The power grid may experience periods where more wind-generated power
 is produced than is needed.  Typically this may happen during night
 hours.
 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 application.
 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 itself.
 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 the assignment of a unique node ID.  Inclusion should
 be completed within a few seconds.

Brandt, et al. Informational [Page 7] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 For ease of use in a consumer application space such as home control,
 nodes may be included without having to type in special codes before
 inclusion.  One way to achieve an acceptable balance between security
 and convenience is to block inclusion during normal operation,
 explicitly enable inclusion support just before adding a new module,
 and disable it again just after adding a new module.
 For security considerations, refer to Section 5.
 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.

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 delivered.

2.6. Remote Video Surveillance

 Remote video surveillance is a fairly classic application for home
 networking.  It provides 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 a sensor to a sink and vice versa,
 this scenario implicates a direct inter-device communication between
 ROLL devices.

Brandt, et al. Informational [Page 8] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

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 that
 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 they are manually activated, they leave all processing to the
 receiving data sink.
 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.
 Since wireless and battery operated systems may never reach 100%
 guaranteed operational time, healthcare and security systems will
 need a management layer implementing alarm mechanisms for low
 battery, report activity, etc.
 For instance, if a blood pressure sensor did not report a new
 measurement, say five minutes after the scheduled time, some
 responsible person must be notified.
 The structure and performance of such a management layer is outside
 the scope of the routing requirements listed in this document.

Brandt, et al. Informational [Page 9] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

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 Section 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 intervals.

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
 timeliness.
 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, 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 a lot of
 safety.  Also, it may be inconvenient to change the batteries in a
 smoke alarm.

Brandt, et al. Informational [Page 10] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 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 the 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:
 +------------------------------+-----------------------------+
 | Use case                     | Requirement                 |
 +------------------------------+-----------------------------+
 |2.1. Lighting Application in  |3.2. Support of Mobility     |
 |Action                        |3.3. Scalability             |
 +------------------------------+-----------------------------+
 |2.2. Energy Conservation and  |3.1. Constraint-Based Routing|
 |Optimizing Energy Consumption |                             |
 +------------------------------+-----------------------------+
 |2.3. Moving a Remote Control  |3.2. Support of Mobility     |
 |Around                        |3.4. Convergence Time        |
 +------------------------------+-----------------------------+
 |2.4. Adding a New Module to   |3.4. Convergence Time        |
 |the System                    |3.5. Manageability           |
 +------------------------------+-----------------------------+
 |2.7. Healthcare               |3.1. Constraint-Based Routing|
 |                              |3.2. Support of Mobility     |
 |                              |3.4. Convergence Time        |
 +------------------------------+-----------------------------+
 |2.8. Alarm Systems            |3.3. Scalability             |
 |                              |3.4. Convergence Time        |
 +------------------------------+-----------------------------+

Brandt, et al. Informational [Page 11] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

3.1. 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
 button.
 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 with such nodes may at best require a 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).

3.2. 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
 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.
 On more rare occasions, receiving nodes may also have moved.
 Examples include a safety-off switch in a clothes iron, a vacuum
 cleaner robot, or the wireless chime of doorbell set.

Brandt, et al. Informational [Page 12] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 Refer to Section 3.4 for routing protocol convergence times.
 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.

3.3. Scalability

 Looking at the number of wall switches, power outlets, sensors of
 various natures, video equipment, and so on in a modern house, it
 seems quite realistic that hundreds of devices may form a home-
 automation network in a fully populated "smart" home, and a large
 proportion of those may be low-power devices.  Moving towards
 professional-building automation, the number of such devices may be
 in the order of several thousands.
 The routing protocol needs to be able to support a basic home
 deployment and so MUST be able to support at least 250 devices in the
 network.  Furthermore, the protocol SHOULD be extensible to support
 more sophisticated and future deployments with a larger number of
 devices.

3.4. Convergence Time

 A wireless home automation network is subject to various
 instabilities due to signal strength variation, moving persons, and
 the like.
 Measured from the transmission of a packet, the following convergence
 time requirements apply.
 The routing protocol MUST converge within 0.5 seconds if no nodes
 have moved (see Section 3.2 for motivation).
 The routing protocol MUST converge within four seconds if nodes have
 moved to re-establish connectivity within a time that a human
 operator would find tolerable as, for example, when moving a remote
 control unit.
 In both cases, "converge" means "the originator node has received a
 response from the destination node".  The above-mentioned convergence
 time requirements apply to a home control network environment of up
 to 250 nodes with up to four repeating nodes between source and
 destination.

Brandt, et al. Informational [Page 13] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

3.5. 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,
 almost without human intervention.

3.6. Stability

 If a node is found to fail often compared to the rest of the network,
 this node SHOULD NOT be the first choice for routing of traffic.

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 one to ten times per hour.
 Remote controls have a similar transmit pattern to wall switches but
 may be activated more frequently in some deployments.
 Temperature/air and 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 five 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.

Brandt, et al. Informational [Page 14] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

5. Security Considerations

 As is the case with every network, LLNs are exposed to routing
 security threats that need to be addressed.  The wireless and
 distributed nature of these networks increases the spectrum of
 potential routing security threats.  This is further amplified by the
 resource constraints of the nodes, thereby preventing resource-
 intensive routing security approaches from being deployed.  A viable
 routing security approach SHOULD be sufficiently lightweight that it
 may be implemented across all nodes in a LLN.  These issues require
 special attention during the design process, so as to facilitate a
 commercially attractive deployment.
 An attacker can snoop, replay, or originate arbitrary messages to a
 node in an attempt to manipulate or disable the routing function.
 To mitigate this, the LLN MUST be able to authenticate a new node
 prior to allowing it to participate in the routing decision process.
 The routing protocol MUST support message integrity.
 A further example of routing security issues that may arise is the
 abnormal behavior of nodes that exhibit an egoistic conduct, such as
 not obeying network rules or forwarding no or false packets.
 Other important issues may arise in the context of denial-of-service
 (DoS) attacks, malicious address space allocations, advertisement of
 variable addresses, a wrong neighborhood, etc.  The routing
 protocol(s) SHOULD support defense against DoS attacks and other
 attempts to maliciously or inadvertently cause the mechanisms of the
 routing protocol(s) to over-consume the limited resources of LLN
 nodes, e.g., by constructing forwarding loops or causing excessive
 routing protocol overhead traffic, etc.
 The properties of self-configuration and self-organization that are
 desirable in a LLN introduce additional routing security
 considerations.  Mechanisms MUST be in place to deny any node that
 attempts to take malicious advantage of self-configuration and self-
 organization procedures.  Such attacks may attempt, for example, to
 cause DoS, drain the energy of power-constrained devices, or to
 hijack the routing mechanism.  A node MUST authenticate itself to a
 trusted node that is already associated with the LLN before the
 former can take part in self-configuration or self-organization.  A
 node that has already authenticated and associated with the LLN MUST
 deny, to the maximum extent possible, the allocation of resources to
 any unauthenticated peer.  The routing protocol(s) MUST deny service
 to any node that has not clearly established trust with the HC-LLN.

Brandt, et al. Informational [Page 15] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

 In a home-control environment, it is considered unlikely that a
 network is constantly being snooped and at the same time, ease of use
 is important.  As a consequence, the network key MAY be exposed for
 short periods during inclusion of new nodes.
 Electronic door locks and other critical applications SHOULD apply
 end-to-end application security on top of the network transport
 security.
 If connected to a backbone network, the LLN SHOULD be capable of
 limiting the resources utilized by nodes in said backbone network so
 as not to be vulnerable to DoS.  This should typically be handled by
 border routers providing access from a backbone network to resources
 in the LLN.
 With low-computation power and scarce energy resources, LLNs' nodes
 may not be able to resist any attack from high-power malicious nodes
 (e.g., laptops and strong radios).  However, the amount of damage
 generated to the whole network SHOULD be commensurate with the number
 of nodes physically compromised.  For example, an intruder taking
 control over a single node SHOULD NOT be able to completely deny
 service to the whole network.
 In general, the routing protocol(s) SHOULD support the implementation
 of routing security best practices across the LLN.  Such an
 implementation ought to include defense against, for example,
 eavesdropping, replay, message insertion, modification, and man-in-
 the-middle attacks.
 The choice of the routing security solutions will have an impact on
 the routing protocol(s).  To this end, routing protocol(s) proposed
 in the context of LLNs MUST support authentication and integrity
 measures and SHOULD support confidentiality (routing security)
 measures.

6. Acknowledgments

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

7. References

7.1. Normative References

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

Brandt, et al. Informational [Page 16] RFC 5826 Home Automation Routing Requirements in LLNs April 2010

7.2. Informative References

 [BUILDING-REQS] Martocci, J., Ed., De Mil, P., Vermeylen, W., and N.
                 Riou, "Building Automation Routing Requirements in
                 Low Power and Lossy Networks", Work in Progress,
                 January 2010.
 [RFC5548]       Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed.,
                 and D. Barthel, Ed., "Routing Requirements for Urban
                 Low-Power and Lossy Networks", RFC 5548, May 2009.
 [RFC5673]       Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
                 Phinney, "Industrial Routing Requirements in Low-
                 Power and Lossy Networks", RFC 5673, October 2009.
 [ROLL-TERM]     Vasseur, JP. "Terminology in Low power And Lossy
                 Networks", Work in Progress, October 2009.

Authors' Addresses

 Anders Brandt
 Sigma Designs, Inc.
 Emdrupvej 26
 Copenhagen, DK-2100
 Denmark
 EMail: abr@sdesigns.dk
 Jakob Buron
 Sigma Designs, Inc.
 Emdrupvej 26
 Copenhagen, DK-2100
 Denmark
 EMail: jbu@sdesigns.dk
 Giorgio Porcu
 Telecom Italia
 Piazza degli Affari, 2
 20123 Milan
 Italy
 EMail: gporcu@gmail.com

Brandt, et al. Informational [Page 17]

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