Networking Working Group J. Martocci, Ed.
Internet-Draft Johnson Controls Inc.
Intended status: Informational Pieter De Mil
Expires: August 3, 2009 Ghent University IBCN
W. Vermeylen
Arts Centre Vooruit
Nicolas Riou
Schneider Electric
February 3, 2009
Building Automation Routing Requirements in Low Power and Lossy
Networks
draft-ietf-roll-building-routing-reqs-05
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Abstract
The Routing Over Low power and Lossy network (ROLL) Working Group has
been chartered to work on routing solutions for Low Power and Lossy
networks (LLN) in various markets: Industrial, Commercial (Building),
Home and Urban. Pursuant to this effort, this document defines the
routing requirements for building automation.
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 [RFC2119].
Table of Contents
1. Terminology....................................................4
2. Introduction...................................................4
3. Facility Management System (FMS) Topology......................5
3.1. Introduction..............................................5
3.2. Sensors/Actuators.........................................7
3.3. Area Controllers..........................................7
3.4. Zone Controllers..........................................7
4. Installation Methods...........................................7
4.1. Wired Communication Media.................................7
4.2. Device Density............................................8
4.2.1. HVAC Device Density..................................8
4.2.2. Fire Device Density..................................9
4.2.3. Lighting Device Density..............................9
4.2.4. Physical Security Device Density.....................9
4.3. Installation Procedure....................................9
5. Building Automation Routing Requirements......................10
5.1. Installation.............................................10
5.1.1. Zero-Configuration Installation.....................11
5.1.2. Sleeping Devices....................................11
5.1.3. Local Testing.......................................11
5.1.4. Device Replacement..................................12
5.2. Scalability..............................................12
5.2.1. Network Domain......................................12
5.2.2. Peer-to-Peer Communication..........................12
5.3. Mobility.................................................13
5.3.1. Mobile Device Requirements..........................13
5.4. Resource Constrained Devices.............................14
5.4.1. Limited Processing Power for Non-routing Devices....14
5.4.2. Limited Processing Power for Routing Devices........14
5.5. Addressing...............................................14
5.5.1. Unicast/Multicast/Anycast...........................14
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5.6. Manageability............................................14
5.6.1. Diagnostics.........................................15
5.6.2. Route Tracking......................................15
5.7. Route Selection..........................................15
5.7.1. Path Cost...........................................15
5.7.2. Path Adaptation.....................................15
5.7.3. Route Redundancy....................................16
5.7.4. Route Discovery Time................................16
5.7.5. Route Preference....................................16
6. Traffic Pattern...............................................16
7. Security Considerations.......................................17
7.1. Security Requirements....................................17
7.1.1. Authentication......................................17
7.1.2. Encryption..........................................18
7.1.3. Disparate Security Policies.........................18
7.1.4. Routing Security Policies To Sleeping Devices.......18
8. IANA Considerations...........................................19
9. Acknowledgments...............................................19
10. References...................................................19
10.1. Normative References....................................19
10.2. Informative References..................................19
11. Appendix A: Additional Building Requirements.................20
11.1. Additional Commercial Product Requirements..............20
11.1.1. Cost...............................................20
11.1.2. Wired and Wireless Implementations.................20
11.1.3. World-wide Applicability...........................20
11.1.4. Support of Application Layer Protocols.............20
11.1.5. Use of Constrained Devices.........................21
11.2. Additional Installation and Commissioning Requirements..21
11.2.1. Device Setup Time..................................21
11.2.2. Unavailability of an IP network....................21
11.3. Additional Network Requirements.........................21
11.3.1. TCP/UDP............................................21
11.3.2. Interference Mitigation............................21
11.3.3. Real-time Performance Measures.....................21
11.3.4. Packet Reliability.................................22
11.3.5. Merging Commissioned Islands.......................22
11.3.6. Adjustable System Table Sizes......................22
11.3.7. Communication Distance.............................22
11.3.8. Automatic Gain Control.............................22
11.3.9. IPv4 Compatibility.................................23
11.3.10. Proxying for Sleeping Devices.....................23
11.3.11. Device and Network Integrity......................23
11.4. Additional Performance Requirements.....................23
11.4.1. Data Rate Performance..............................23
11.4.2. Firmware Upgrades..................................23
11.4.3. Prioritized Routing................................23
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11.4.4. Path Persistence...................................24
11.5. Additional Network Security Requirements................24
11.5.1. Encryption Levels..................................24
11.5.2. Security Policy Flexibility........................24
12. Appendix B: FMS Use-Cases....................................24
12.1. Locking and Unlocking the Building......................25
12.2. Building Energy Conservation............................25
12.3. Inventory and Remote Diagnosis of Safety Equipment......25
12.4. Life Cycle of Field Devices.............................26
12.5. Surveillance............................................26
12.6. Emergency...............................................26
12.7. Public Address..........................................27
1. Terminology
For description of the terminology used in this specification, please
see [I-D.ietf-roll-terminology].
2. Introduction
Commercial buildings have been fitted with pneumatic and subsequently
electronic communication pathways connecting sensors to their
controllers for over one hundred years. Recent economic and
technical advances in wireless communication allow facilities to
increasingly utilize a wireless solution in lieu of a wired solution;
thereby reducing installation costs while maintaining highly reliant
communication.
The cost benefits and ease of installation of wireless sensors allow
customers to further instrument their facilities with additional
sensors; providing tighter control while yielding increased energy
savings.
Wireless solutions will be adapted from their existing wired
counterparts in many of the building applications including, but not
limited to Heating, Ventilation, and Air Conditioning (HVAC),
Lighting, Physical Security, Fire, and Elevator systems. These
devices will be developed to reduce installation costs; while
increasing installation and retrofit flexibility, as well as
increasing the sensing fidelity to improve efficiency and building
service quality.
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Sensing devices may be battery-less; battery or mains powered.
Actuators and area controllers will be mains powered. Due to
building code and/or device density (e.g. equipment room), it is
envisioned that a mix of wired and wireless sensors and actuators
will be deployed within a building.
Facility Management Systems (FMS) are deployed in a large set of
vertical markets including universities; hospitals; government
facilities; Kindergarten through High School (K-12); pharmaceutical
manufacturing facilities; and single-tenant or multi-tenant office
buildings. These buildings range in size from 100K sqft structures (5
story office buildings), to 1M sqft skyscrapers (100 story
skyscrapers) to complex government facilities such as the Pentagon.
The described topology is meant to be the model to be used in all
these types of environments, but clearly must be tailored to the
building class, building tenant and vertical market being served.
The following sections describe the sensor, actuator, area controller
and zone controller layers of the topology. (NOTE: The Building
Controller and Enterprise layers of the FMS are excluded from this
discussion since they typically deal in communication rates requiring
LAN/WLAN communication technologies).
Section 3 describes FMS architectures commonly installed in
commercial buildings. Section 4 describes installation methods
deployed for new and remodeled construction. Appendix A documents
important commercial building requirements that are out of scope for
routing yet will be essential to the final acceptance of the
protocols used within the building. Appendix B describes various FMS
use-cases and the interaction with humans for energy conservation and
life-safety applications.
Sections 3, 4, Appendix A and Appendix B are mainly included for
educational purposes. The aim of this document is to provide the set
of IPv6 routing requirements for LLNs in buildings as described in
Section 5.
3. Facility Management System (FMS) Topology
3.1. Introduction
To understand the network systems requirements of a facility
management system in a commercial building, this document uses a
framework to describe the basic functions and composition of the
system. An FMS is a hierarchical system of sensors, actuators,
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controllers and user interface devices based on spatial extent.
Additionally, an FMS may also be divided functionally across alike,
but different building subsystems such as HVAC, Fire, Security,
Lighting, Shutters and Elevator control systems as denoted in Figure
1.
Much of the makeup of an FMS is optional and installed at the behest
of the customer. Sensors and actuators have no standalone
functionality. All other devices support partial or complete
standalone functionality. These devices can optionally be tethered
to form a more cohesive system. The customer requirements dictate
the level of integration within the facility. This architecture
provides excellent fault tolerance since each node is designed to
operate in an independent mode if the higher layers are unavailable.
+------+ +-----+ +------+ +------+ +------+ +------+
Bldg App'ns | | | | | | | | | | | |
| | | | | | | | | | | |
Building Cntl | | | | | S | | L | | S | | E |
| | | | | E | | I | | H | | L |
Area Control | H | | F | | C | | G | | U | | E |
| V | | I | | U | | H | | T | | V |
Zone Control | A | | R | | R | | T | | T | | A |
| C | | E | | I | | I | | E | | T |
Actuators | | | | | T | | N | | R | | O |
| | | | | Y | | G | | S | | R |
Sensors | | | | | | | | | | | |
+------+ +-----+ +------+ +------+ +------+ +------+
Figure 1: Building Systems and Devices
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3.2. Sensors/Actuators
As Figure 1 indicates an FMS may be composed of many functional
stacks or silos that are interoperably woven together via Building
Applications. Each silo has an array of sensors that monitor the
environment and actuators that effect the environment as determined
by the upper layers of the FMS topology. The sensors typically are
the fringe of the network structure providing environmental data into
the system. The actuators are the sensor's counterparts modifying
the characteristics of the system based on the input sensor data and
the applications deployed.
3.3. Area Controllers
An area describes a small physical locale within a building,
typically a room. HVAC (temperature and humidity) and Lighting (room
lighting, shades, solar loads) vendors oft times deploy area
controllers. Area controls are fed by sensor inputs that monitor the
environmental conditions within the room. Common sensors found in
many rooms that feed the area controllers include temperature,
occupancy, lighting load, solar load and relative humidity. Sensors
found in specialized rooms (such as chemistry labs) might include air
flow, pressure, CO2 and CO particle sensors. Room actuation includes
temperature setpoint, lights and blinds/curtains.
3.4. Zone Controllers
Zone Control supports a similar set of characteristics as the Area
Control albeit to an extended space. A zone is normally a logical
grouping or functional division of a commercial building. A zone may
also coincidentally map to a physical locale such as a floor.
Zone Control may have direct sensor inputs (smoke detectors for
fire), controller inputs (room controllers for air-handlers in HVAC)
or both (door controllers and tamper sensors for security). Like
area/room controllers, zone controllers are standalone devices that
operate independently or may be attached to the larger network for
more synergistic control.
4. Installation Methods
4.1. Wired Communication Media
Commercial controllers are traditionally deployed in a facility using
twisted pair serial media following the EIA-485 electrical standard
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operating nominally at 38400 to 76800 baud. This allows runs to 5000
ft without a repeater. With the maximum of three repeaters, a single
communication trunk can serpentine 15000 ft. EIA-485 is a multi-drop
media allowing upwards to 255 devices to be connected to a single
trunk.
Most sensors and virtually all actuators currently used in
commercial buildings are "dumb", non-communicating hardwired devices.
However, sensor buses are beginning to be deployed by vendors which
are used for smart sensors and point multiplexing. The Fire
industry deploys addressable fire devices, which usually use some
form of proprietary communication wiring driven by fire codes.
4.2. Device Density
Device density differs depending on the application and as dictated
by the local building code requirements. The following sections
detail typical installation densities for different applications.
4.2.1. HVAC Device Density
HVAC room applications typically have sensors/actuators and
controllers spaced about 50ft apart. In most cases there is a 3:1
ratio of sensors/actuators to controllers. That is, for each room
there is an installed temperature sensor, flow sensor and damper
actuator for the associated room controller.
HVAC equipment room applications are quite different. An air handler
system may have a single controller with upwards to 25 sensors and
actuators within 50 ft of the air handler. A chiller or boiler is
also controlled with a single equipment controller instrumented with
25 sensors and actuators. Each of these devices would be
individually addressed since the devices are mandated or optional as
defined by the specified HVAC application. Air handlers typically
serve one or two floors of the building. Chillers and boilers may be
installed per floor, but many times service a wing, building or the
entire complex via a central plant.
These numbers are typical. In special cases, such as clean rooms,
operating rooms, pharmaceuticals and labs, the ratio of sensors to
controllers can increase by a factor of three. Tenant installations
such as malls would opt for packaged units where much of the sensing
and actuation is integrated into the unit. Here a single device
address would serve the entire unit.
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4.2.2. Fire Device Density
Fire systems are much more uniformly installed with smoke detectors
installed about every 50 feet. This is dictated by local building
codes. Fire pull boxes are installed uniformly about every 150 feet.
A fire controller will service a floor or wing. The fireman's fire
panel will service the entire building and typically is installed in
the atrium.
4.2.3. Lighting Device Density
Lighting is also very uniformly installed with ballasts installed
approximately every 10 feet. A lighting panel typically serves 48 to
64 zones. Wired systems tether many lights together into a single
zone. Wireless systems configure each fixture independently to
increase flexibility and reduce installation costs.
4.2.4. Physical Security Device Density
Security systems are non-uniformly oriented with heavy density near
doors and windows and lighter density in the building interior space.
The recent influx of interior and perimeter camera systems is
increasing the security footprint. These cameras are atypical
endpoints requiring upwards to 1 megabit/second (Mbit/s) data rates
per camera as contrasted by the few Kbits/s needed by most other FMS
sensing equipment. Previously, camera systems had been deployed on
proprietary wired high speed network. More recent implementations
utilize wired or wireless IP cameras integrated to the enterprise
LAN.
4.3. Installation Procedure
Wired FMS installation is a multifaceted procedure depending on the
extent of the system and the software interoperability requirement.
However, at the sensor/actuator and controller level, the procedure
is typically a two or three step process.
Most FMS equipment will utilize 24 VAC power sources that can be
installed by a low-voltage electrician. He/she arrives on-site
during the construction of the building prior to drywall and ceiling
installation. This allows him/her to allocate wall space, easily
land the equipment and run the wired controller and sensor networks.
The Building Controllers and Enterprise network are not normally
installed until months later. The electrician completes his task by
running a wire verification procedure that shows proper continuity
between the devices and proper local operation of the devices.
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Later in the installation cycle, the higher order controllers are
installed, programmed and commissioned together with the previously
installed sensors, actuators and controllers. In most cases the IP
network is still not operable. The Building Controllers are
completely commissioned using a crossover cable or a temporary IP
switch together with static IP addresses.
Once the IP network is operational, the FMS may optionally be added
to the enterprise network. The wireless installation process must
follow the same work flow. The electrician installs the products as
before and executes local functional tests between the wireless
device to assure operation before leaving the job. The electrician
does not carry a laptop so the commissioning must be built into the
device operation.
5. Building Automation Routing Requirements
Following are the building automation routing requirements for a
network used to integrate building sensor, actuator and control
products. These requirements have been limited to routing
requirements only. These requirements are written not presuming any
preordained network topology, physical media (wired) or radio
technology (wireless). See Appendix A for additional requirements
that have been deemed outside the scope of this document yet will
pertain to the successful deployment of building automation systems.
5.1. Installation
Building control systems typically are installed and tested by
electricians having little computer knowledge and no network
knowledge whatsoever. These systems are often installed during the
building construction phase before the drywall and ceilings are in
place. For new construction projects, the building enterprise IP
network is not in place during installation of the building control
system. For retrofit applications, the installer will still operate
independently from the IP network so as not to affect network
operations during the installation phase.
Local (ad hoc) testing of sensors and room controllers must be
completed before the tradesperson can complete his/her work. This
testing allows the tradesperson to verify correct client (e.g. light
switch) and server (e.g. light ballast) before leaving the jobsite.
In traditional wired systems correct operation of a light
switch/ballast pair was as simple as flipping on the light switch.
In wireless applications, the tradesperson has to assure the same
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operation, yet be sure the operation of the light switch is
associated to the proper ballast.
System level commissioning will later be deployed using a more
computer savvy person with access to a commissioning device (e.g. a
laptop computer). The completely installed and commissioned
enterprise IP network may or may not be in place at this time.
Following are the installation routing requirements.
5.1.1. Zero-Configuration Installation
It MUST be possible to fully commission network devices without
requiring any additional commissioning device (e.g. laptop).
5.1.2. Sleeping Devices
Sensing devices will, in some cases, utilize battery power or energy
harvesting techniques for power and will operate mostly in a sleep
mode to maintain power consumption within a modest budget. The
routing protocol MUST take into account device characteristics such
as power budget. If such devices provide routing, rather than merely
host connectivity, the energy costs associated with such routing
needs to fit within the power budget. If the mechanisms for duty
cycling dictate very long response times or specific temporal
scheduling, routing will need to take such constraints into account.
Typically, batteries need to be operational for at least 5 years when
the sensing device is transmitting its data(e.g. 64 octets) once per
minute. This requires that sleeping devices MUST have minimal link
on time when they awake and transmit onto the network. Moreover,
maintaining the ability to receive inbound data MUST be accomplished
with minimal link on time.
Proxies with unconstrained power budgets oft times are used to cache
the inbound data for a sleeping device until the device awakens. In
such cases, the routing protocol MUST discover the capability of a
node to act as a proxy during path calculation; then deliver the
packet to the assigned proxy for later delivery to the sleeping
device upon its next awakened cycle.
5.1.3. Local Testing
The local sensors and requisite actuators and controllers must be
testable within the locale (e.g. room) to assure communication
connectivity and local operation without requiring other systemic
devices. Routing should allow for temporary ad hoc paths to be
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established that are updated as the network physically and
functionally expands.
5.1.4. Device Replacement
Replacement devices need to be plug-and-play with no additional setup
compared to what is normally required for a new device. Devices
referencing data in the replaced device MUST be able to reference
data in its replacement without being reconfigured to refer to the
new device. Thus, such a reference cannot be a hardware identifier,
such as the MAC address, nor a hard-coded route. If such a reference
is an IP address, the replacement device MUST be assigned the IP
addressed previously bound to the replaced device. Or if the logical
equivalent of a hostname is used for the reference, it must be
translated to the replacement IP address.
5.2. Scalability
Building control systems are designed for facilities from 50000 sq.
ft. to 1M+ sq. ft. The networks that support these systems must
cost-effectively scale accordingly. In larger facilities
installation may occur simultaneously on various wings or floors, yet
the end system must seamlessly merge. Following are the scalability
requirements.
5.2.1. Network Domain
The routing protocol MUST be able to support networks with at least
2000 nodes supporting at least 1000 routing devices and 1000 non-
routing device. Subnetworks (e.g. rooms, primary equipment) within
the network must support upwards to 255 sensors and/or actuators.
5.2.2. Peer-to-Peer Communication
The data domain for commercial FMS systems may sprawl across a vast
portion of the physical domain. For example, a chiller may reside in
the facility's basement due to its size, yet the associated cooling
towers will reside on the roof. The cold-water supply and return
pipes serpentine through all the intervening floors. The feedback
control loops for these systems require data from across the
facility.
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A network device MUST be able to communicate in a peer-to-peer manner
with any other device on the network. Thus, the routing protocol MUST
provide routes between arbitrary hosts within the appropriate
administrative domain.
5.3. Mobility
Most devices are affixed to walls or installed on ceilings within
buildings. Hence the mobility requirements for commercial buildings
are few. However, in wireless environments location tracking of
occupants and assets is gaining favor. Asset tracking applications
require monitoring movement with granularity of a minute. This soft
real-time performance requirement is reflected in the performance
requirements below.
5.3.1. Mobile Device Requirements
To minimize network dynamics, mobile devices SHOULD not be allowed to
act as forwarding devices (routers) for other devices in the LLN.
A mobile device that moves within an LLN SHOULD reestablish end-to-
end communication to a fixed device also in the LLN within 2 seconds.
The network convergence time should be less than 5 seconds once the
mobile device stops moving.
A mobile device that moves outside of an LLN SHOULD reestablish end-
to-end communication to a fixed device in the new LLN within 5
seconds. The network convergence time should be less than 5 seconds
once the mobile device stops moving.
A mobile device that moves outside of one LLN into another LLN SHOULD
reestablish end-to-end communication to a fixed device in the old LLN
within 10 seconds. The network convergence time should be less than
10 seconds once the mobile device stops.
A mobile device that moves outside of one LLN into another LLN SHOULD
reestablish end-to-end communication to another mobile device in the
new LLN within 20 seconds. The network convergence time should be
less than 30 seconds once the mobile devices stop moving.
A mobile device that moves outside of one LLN into another LLN SHOULD
reestablish end-to-end communication to a mobile device in the old
LLN within 30 seconds. The network convergence time should be less
than 30 seconds once the mobile devices stop moving.
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5.4. Resource Constrained Devices
Sensing and actuator device processing power and memory may be 4
orders of magnitude less (i.e. 10,000x) than many more traditional
client devices on an IP network. The routing mechanisms must
therefore be tailored to fit these resource constrained devices.
5.4.1. Limited Processing Power for Non-routing Devices.
The software size requirement for non-routing devices (e.g. sleeping
sensors and actuators) SHOULD be implementable in 8-bit devices with
no more than 128KB of memory.
5.4.2. Limited Processing Power for Routing Devices
The software size requirements for routing devices (e.g. room
controllers) SHOULD be implementable in 8-bit devices with no more
than 256KB of flash memory.
5.5. Addressing
Facility Management systems require different communication schemes
to solicit or post network information. Broadcasts or anycasts need
be used to resolve unresolved references within a device when the
device first joins the network.
As with any network communication, broadcasting should be minimized.
This is especially a problem for small embedded devices with limited
network bandwidth. In many cases a global broadcast could be
replaced with a multicast since the application knows the application
domain. Broadcasts and multicasts are typically used for network
joins and application binding in embedded systems.
5.5.1. Unicast/Multicast/Anycast
Routing MUST support anycast, unicast, and multicast.
5.6. Manageability
In addition to the initial installation of the system (see Section
5.1), it is equally important for the ongoing maintenance of the
system to be simple and inexpensive.
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5.6.1. Diagnostics
To improve diagnostics, the network layer SHOULD be able to be placed
in and out of 'verbose' mode. Verbose mode is a temporary debugging
mode that provides additional communication information including at
least total number of routed packets sent and received, number of
routing failures (no route available), neighbor table members, and
routing table entries.
5.6.2. Route Tracking
Route diagnostics SHOULD be supported providing information such as
path quality; number of hops; available alternate active paths with
associated costs. Path quality is the relative measure of 'goodness'
of the selected source to destination path as compared to alternate
paths. This composite value may be measured as a function of hop
count, signal strength, available power, existing active paths or any
other criteria deemed by ROLL as the path cost differentiator.
5.7. Route Selection
Route selection determines reliability and quality of the
communication paths among the devices. Optimizing the routes over
time resolve any nuances developed at system startup when nodes are
asynchronously adding themselves to the network. Path adaptation
will reduce latency if the path costs consider hop count as a cost
attribute.
5.7.1. Path Cost
The routing protocol MUST support a metric of route quality and
optimize path selection according to such metrics within constraints
established for links along the paths. These metrics SHOULD reflect
metrics such as signal strength, available bandwidth, hop count,
energy availability and communication error rates.
5.7.2. Path Adaptation
Communication paths MUST adapt toward the chosen metric(s) (e.g.
signal quality) optimality in time.
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5.7.3. Route Redundancy
The routing layer SHOULD be configurable to allow secondary and
tertiary paths to be established and used upon failure of the primary
path.
5.7.4. Route Discovery Time
Mission critical commercial applications (e.g. Fire, Security)
require reliable communication and guaranteed end-to-end delivery of
all messages in a timely fashion. Application layer time-outs must
be selected judiciously to cover anomalous conditions such as lost
packets and/or path discoveries; yet not be set too large to over
damp the network response. If route discovery occurs during packet
transmission time, it SHOULD NOT add more than 120ms of latency to
the packet delivery time.
5.7.5. Route Preference
Route cost algorithms SHOULD allow the installer to optionally select
'preferred' paths based on the known spatial layout of the
communicating devices.
6. Traffic Pattern
The independent nature of the automation systems within a building
plays heavy onto the network traffic patterns. Much of the real-time
sensor data stays within the local environment. Alarming and other
event data will percolate to higher layers.
Systemic data may be either polled or event based. Polled data
systems will generate a uniform packet load on the network. This
architecture has proven not scalable. Most vendors have developed
event based systems which pass data on event. These systems are
highly scalable and generate low data on the network at quiescence.
Unfortunately, the systems will generate a heavy load on startup
since all the initial data must migrate to the controller level.
They also will generate a temporary but heavy load during firmware
upgrades. This latter load can normally be mitigated by performing
these downloads during off-peak hours.
Devices will need to reference peers occasionally for sensor data or
to coordinate across systems. Normally, though, data will migrate
from the sensor level upwards through the local, area then
supervisory level. Bottlenecks will typically form at the funnel
point from the area controllers to the supervisory controllers.
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Initial system startup after a controlled outage or unexpected power
failure puts tremendous stress on the network and on the routing
algorithms. An FMS system is comprised of a myriad of control
algorithms at the room, area, zone, and enterprise layers. When
these control algorithms are at quiescence, the real-time data
changes are small and the network will not saturate. However, upon
any power loss, the control loops and real-time data quickly atrophy.
A ten minute outage may take many hours to regain control.
Upon restart all lines-powered devices power-on instantaneously.
However due to application startup and self tests, these devices will
attempt to join the network randomly. Empirical testing indicates
that routing paths acquired during startup will tend to be very
oblique since the available neighbor lists are incomplete. This
demands an adaptive routing protocol to allow for path optimization
as the network stabilizes.
7. Security Considerations
Security policies, especially wireless encryption and device
authentication needs to be considered, especially with concern to the
impact on the processing capabilities and additional latency incurred
on the sensors, actuators and controllers.
FMS systems are typically highly configurable in the field and hence
the security policy is most often dictated by the type of building to
which the FMS is being installed. Single tenant owner occupied
office buildings installing lighting or HVAC control are candidates
for implementing low or even no security on the LLN. Antithetically,
military or pharmaceutical facilities require strong security
policies. As noted in the installation procedures above, security
policies must be facile to allow no security during the installation
phase (prior to building occupancy), yet easily raise the security
level network wide during the commissioning phase of the system.
7.1. Security Requirements
7.1.1. Authentication
Authentication SHOULD be optional on the LLN. Authentication SHOULD
be fully configurable on-site. Authentication policy and updates MUST
be routable over-the-air. Authentication SHOULD occur upon joining
or rejoining a network. However, once authenticated devices SHOULD
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NOT need to reauthenticate with any other devices in the LLN.
Packets may need authentication at the source and destination nodes,
however, packets routed through intermediate hops should not need
reauthentication at each hop.
7.1.2. Encryption
7.1.2.1. Encryption Types
Data encryption of packets MUST optionally be supported by use of
either a network wide key and/or application key. The network key
would apply to all devices in the LLN. The application key would
apply to a subset of devices on the LLN.
The network key and application keys would be mutually exclusive.
The routing protocol MUST allow routing a packet encrypted with an
application key through forwarding devices that without requiring
each node in the path have the application key.
7.1.2.2. Packet Encryption
The encryption policy MUST support encryption of the payload only or
the entire packet. Payload only encryption would eliminate the
decryption/re-encryption overhead at every hop providing more real-
time performance.
7.1.3. Disparate Security Policies
Due to the limited resources of an LLN, the security policy defined
within the LLN MUST be able to differ from that of the rest of the IP
network within the facility yet packets MUST still be able to route
to or through the LLN from/to these networks.
7.1.4. Routing Security Policies To Sleeping Devices
The routing protocol MUST gracefully handle routing temporal security
updates (e.g. dynamic keys) to sleeping devices on their 'awake'
cycle to assure that sleeping devices can readily and efficiently
access then network.
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8. IANA Considerations
This document includes no request to IANA.
9. Acknowledgments
In addition to the authors, J. P. Vasseur, David Culler, Ted Humpal
and Zach Shelby are gratefully acknowledged for their contributions
to this document.
This document was prepared using 2-Word-v2.0.template.dot.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[I-D.ietf-roll-terminology] Vasseur, J., "Terminology in Low
power And Lossy Networks", draft-ietf-roll-terminology-00 (work
in progress), October 2008.
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11. Appendix A: Additional Building Requirements
Appendix A contains additional building requirements that were deemed
out of scope for ROLL, yet provided ancillary substance for the
reader.
11.1. Additional Commercial Product Requirements
11.1.1. Cost
The total installed infrastructure cost including but not limited to
the media, required infrastructure devices (amortized across the
number of devices); labor to install and commission the network must
not exceed $1.00/foot for wired implementations.
Wireless implementations (total installed cost) must cost no more
than 80% of wired implementations.
11.1.2. Wired and Wireless Implementations
Vendors will likely not develop a separate product line for both
wired and wireless networks. Hence, the solutions set forth must
support both wired and wireless implementations.
11.1.3. World-wide Applicability
Wireless devices must be supportable at the 2.4Ghz ISM band.
Wireless devices should be supportable at the 900 and 868 ISM bands
as well.
11.1.4. Support of Application Layer Protocols
11.1.4.1. BACnet Building Protocol
BACnet is an ISO world-wide application layer IP protocol. Devices
implementing ROLL routing protocol should support the BACnet
protocol.
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11.1.5. Use of Constrained Devices
The network may be composed of a heterogeneous mix of full, battery
and energy harvested powered devices. The routing protocol must
support these constrained devices.
11.1.5.1. Energy Harvested Sensors
Devices utilizing available ambient energy (e.g. solar, air flow,
temperature differential)for sensing and communicating should be
supported by the solution set.
11.2. Additional Installation and Commissioning Requirements
11.2.1. Device Setup Time
Device and Network setup by the installer must take no longer than 20
seconds per device installed.
11.2.2. Unavailability of an IP network
Product commissioning must be performed by an application engineer
prior to the installation of the IP network (e.g. switches, routers,
DHCP, DNS).
11.3. Additional Network Requirements
11.3.1. TCP/UDP
Connection based and connectionless services must be supported
11.3.2. Interference Mitigation
The network must automatically detect interference and seamlessly
migrate the network hosts channel to improve communication. Channel
changes and nodes response to the channel change must occur within 60
seconds.
11.3.3. Real-time Performance Measures
A node transmitting a 'request with expected reply' to another node
must send the message to the destination and receive the response in
not more than 120 msec. This response time should be achievable with
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5 or less hops in each direction. This requirement assumes network
quiescence and a negligible turnaround time at the destination node.
11.3.4. Packet Reliability
Reliability must meet the following minimum criteria :
< 1% MAC layer errors on all messages; After no more than three
retries
< .1% Network layer errors on all messages;
After no more than three additional retries;
< 0.01% Application layer errors on all messages.
Therefore application layer messages will fail no more than once
every 100,000 messages.
11.3.5. Merging Commissioned Islands
Subsystems are commissioned by various vendors at various times
during building construction. These subnetworks must seamlessly
merge into networks and networks must seamlessly merge into
internetworks since the end user wants a holistic view of the system.
11.3.6. Adjustable System Table Sizes
Routing must support adjustable router table entry sizes on a per
node basis to maximize limited RAM in the devices.
11.3.7. Communication Distance
A source device may be upwards to 1000 feet from its destination.
Communication may need to be established between these devices
without needing to install other intermediate 'communication only'
devices such as repeaters.
11.3.8. Automatic Gain Control
For wireless implementations, the device radios should incorporate
automatic transmit power regulation to maximize packet transfer and
minimize network interference regardless of network size or density.
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11.3.9. IPv4 Compatibility
The routing protocol must support cost-effective intercommunication
among IPv4 and IPv6 devices.
11.3.10. Proxying for Sleeping Devices
Routing must support in-bound packet caches for low-power (battery
and energy harvested) devices when these devices are not accessible
on the network.
These devices must have a designated powered proxying device to which
packets will be temporarily routed and cached until the constrained
device accesses the network.
11.3.11. Device and Network Integrity
Commercial Building devices must all be periodically scanned to
assure that the device is viable and can communicate data and alarm
information as needed. Network routers should maintain previous
packet flow information temporally to minimize overall network
overhead.
11.4. Additional Performance Requirements
11.4.1. Data Rate Performance
An effective data rate of 20kbits/s is the lowest acceptable
operational data rate acceptable on the network.
11.4.2. Firmware Upgrades
To support high speed code downloads, routing MUST support transports
that provide parallel downloads to targeted devices yet guarantee
packet delivery. In cases where the spatial position of the devices
requires multiple hops, the algorithm must recurse through the
network until all targeted devices have been serviced. Devices
receiving a download MAY cease normal operation, but upon completion
of the download must automatically resume normal operation.
11.4.3. Prioritized Routing
Network and application routing prioritization is required to assure
that mission critical applications (e.g. Fire Detection) cannot be
deferred while less critical application access the network.
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11.4.4. Path Persistence
To eliminate high network traffic in power-fail or brown-out
conditions previously established routes SHOULD be remembered and
invoked prior to establishing new routes for those devices reentering
the network.
11.5. Additional Network Security Requirements
11.5.1. Encryption Levels
Encryption SHOULD be optional on the LLN. Encryption SHOULD be fully
configurable on-site. Encryption policy and updates SHOULD be
transmittable over-the-air and in-the-clear.
11.5.2. Security Policy Flexibility
In most facilities authentication and encryption will be turned off
during installation.
More complex encryption policies might be put in force at
commissioning time. New encryption policies MUST be allowed to be
presented to all devices in the LLN over the network without needing
to visit each device.
12. Appendix B: FMS Use-Cases
Appendix B contains FMS use-cases that describes the use of sensors
and controllers for various applications with a commercial building
and how they interplay with energy conservation and life-safety
applications.
The Vooruit arts centre is a restored monument which dates from 1913.
This complex monument consists of over 350 different rooms including
a meeting rooms, large public halls and theaters serving as many as
2500 guests. A number of use cases regarding Vooruit are described
in the following text. The situations and needs described in these
use cases can also be found in all automated large buildings, such as
airports and hospitals.
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12.1. Locking and Unlocking the Building
The member of the cleaning staff arrives first in the morning
unlocking the building (or a part of it) from the control room. This
means that several doors are unlocked; the alarms are switched off;
the heating turns on; some lights switch on, etc. Similarly, the
last person leaving the building has to lock the building. This will
lock all the outer doors, turn the alarms on, switch off heating and
lights, etc.
The "building locked" or "building unlocked" event needs to be
delivered to a subset of all the sensors and actuators. It can be
beneficial if those field devices form a group (e.g. "all-sensors-
actuators-interested-in-lock/unlock-events). Alternatively, the area
and zone controllers could form a group where the arrival of such an
event results in each area and zone controller initiating unicast or
multicast within the LLN.
This use case is also described in the home automation, although the
requirement about preventing the "popcorn effect" I-D.ietf-roll-home-
routing-reqs] can be relaxed a bit in building automation. It would
be nice if lights, roll-down shutters and other actuators in the same
room or area with transparent walls execute the command around (not
'at') the same time (a tolerance of 200 ms is allowed).
12.2. Building Energy Conservation
A room that is not in use should not be heated, air conditioned or
ventilated and the lighting should be turned off or dimmed. In a
building with many rooms it can happen quite frequently that someone
forgets to switch off the HVAC and lighting, thereby wasting valuable
energy. To prevent this occurrence, the facility manager might
program the building according to the day's schedule. This way
lighting and HVAC is turned on prior to the use of a room, and turned
off afterwards. Using such a system Vooruit has realized a saving of
35% on the gas and electricity bills.
12.3. Inventory and Remote Diagnosis of Safety Equipment
Each month Vooruit is obliged to make an inventory of its safety
equipment. This task takes two working days. Each fire extinguisher
(100), fire blanket (10), fire-resistant door (120) and evacuation
plan (80) must be checked for presence and proper operation. Also
the battery and lamp of every safety lamp must be checked before each
public event (safety laws). Automating this process using asset
tracking and low-power wireless technologies would reduce a heavy
burden on working hours.
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It is important that these messages are delivered very reliably and
that the power consumption of the sensors/actuators attached to this
safety equipment is kept at a very low level.
12.4. Life Cycle of Field Devices
Some field devices (e.g. smoke detectors) are replaced periodically.
The ease by which devices are added and deleted from the network is
very important to support augmenting sensors/actuators during
construction.
A secure mechanism is needed to remove the old device and install the
new device. New devices need to be authenticated before they can
participate in the routing process of the LLN. After the
authentication, zero-configuration of the routing protocol is
necessary.
12.5. Surveillance
Ingress and egress are real-time applications needing response times
below 500msec, for example for cardkey authorization. It must be
possible to configure doors individually to restrict use on a per
person basis with respect to time-of-day and person entering. While
much of the surveillance application involves sensing and actuation
at the door and communication with the centralized security system,
other aspects, including tamper, door ajar, and forced entry
notification, are to be delivered to one or more fixed or mobile user
devices within 5 seconds.
12.6. Emergency
In case of an emergency it is very important that all the visitors be
evacuated as quickly as possible. The fire and smoke detectors set
off an alarm and alert the mobile personnel on their user device
(e.g. PDA). All emergency exits are instantly unlocked and the
emergency lighting guides the visitors to these exits. The necessary
sprinklers are activated and the electricity grid monitored if it
becomes necessary to shut down some parts of the building. Emergency
services are notified instantly.
A wireless system could bring in some extra safety features.
Locating fire fighters and guiding them through the building could be
a life-saving application.
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These life critical applications ought to take precedence over other
network traffic. Commands entered during these emergencies have to
be properly authenticated by device, user, and command request.
12.7. Public Address
It should be possible to send audio and text messages to the visitors
in the building. These messages can be very diverse, e.g. ASCII text
boards displaying the name of the event in a room, audio
announcements such as delays in the program, lost and found children,
evacuation orders, etc.
The control network is expected be able to readily sense the presence
of an audience in an area and deliver applicable message content.
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Authors' Addresses
Jerry Martocci
Johnson Control
507 E. Michigan Street
Milwaukee, Wisconsin, 53202
USA
Phone: 414.524.4010
Email: jerald.p.martocci@jci.com
Nicolas Riou
Schneider Electric
Technopole 38TEC T3
37 quai Paul Louis Merlin
38050 Grenoble Cedex 9
France
Phone: +33 4 76 57 66 15
Email: nicolas.riou@fr.schneider-electric.com
Pieter De Mil
Ghent University - IBCN
G. Crommenlaan 8 bus 201
Ghent 9050
Belgium
Phone: +32-9331-4981
Fax: +32--9331--4899
Email: pieter.demil@intec.ugent.be
Wouter Vermeylen
Arts Centre Vooruit
???
Ghent 9000
Belgium
Phone: ???
Fax: ???
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Email: wouter@vooruit.be
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