Networking Working Group J. Martocci, Ed.
Internet-Draft Johnson Controls Inc.
Intended status: Informational Pieter De Mil
Expires: February 7, 2010 Ghent University IBCN
W. Vermeylen
Arts Centre Vooruit
Nicolas Riou
Schneider Electric
August 7, 2009
Building Automation Routing Requirements in Low Power and Lossy
Networks
draft-ietf-roll-building-routing-reqs-06
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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 networks. Pursuant to this effort, this document
defines the IPv6 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. Overview of Building Automation Networks.......................5
3.1. Introduction..............................................5
3.2. Building Systems Equipment................................6
3.2.1. Sensors/Actuators....................................6
3.2.2. Area Controllers.....................................7
3.2.3. Zone Controllers.....................................7
3.3. Equipment Installation Methods............................7
3.4. Device Density............................................8
3.4.1. HVAC Device Density..................................8
3.4.2. Fire Device Density..................................9
3.4.3. Lighting Device Density..............................9
3.4.4. Physical Security Device Density.....................9
4. Traffic Pattern................................................9
5. Building Automation Routing Requirements......................11
5.1. Device and Network Commissioning.........................11
5.1.1. Zero-Configuration Installation.....................12
5.1.2. Local Testing.......................................12
5.1.3. Device Replacement..................................12
5.2. Scalability..............................................12
5.2.1. Network Domain......................................13
5.2.2. Peer-to-Peer Communication..........................13
5.3. Mobility.................................................13
5.3.1. Mobile Device Requirements..........................13
5.4. Resource Constrained Devices.............................14
5.4.1. Limited memory footprint on host devices............14
5.4.2. Limited Processing Power for routers................14
5.4.3. Sleeping Devices....................................14
5.5. Addressing...............................................15
5.6. Manageability............................................15
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5.6.1. Diagnostics.........................................15
5.6.2. Route Tracking......................................16
5.7. Route Selection..........................................16
5.7.1. Route Cost..........................................16
5.7.2. Route Adaptation....................................16
5.7.3. Route Redundancy....................................16
5.7.4. Route Discovery Time................................16
5.7.5. Route Preference....................................17
5.7.6. Real-time Performance Measures......................17
5.7.7. Prioritized Routing.................................17
5.8. Security Requirements....................................17
5.8.1. Authentication......................................18
5.8.2. Encryption..........................................18
5.8.3. Disparate Security Policies.........................18
5.8.4. Routing Security Policies To Sleeping Devices.......18
6. IANA Considerations...........................................19
7. Acknowledgments...............................................19
8. References....................................................19
8.1. Normative References.....................................19
8.2. Informative References...................................19
9. Appendix A: Additional Building Requirements..................19
9.1. Additional Commercial Product Requirements...............20
9.1.1. Wired and Wireless Implementations..................20
9.1.2. World-wide Applicability............................20
9.2. Additional Installation and Commissioning Requirements...20
9.2.1. Unavailability of an IP network.....................20
9.3. Additional Network Requirements..........................20
9.3.1. TCP/UDP.............................................20
9.3.2. Interference Mitigation.............................20
9.3.3. Packet Reliability..................................20
9.3.4. Merging Commissioned Islands........................21
9.3.5. Adjustable Routing Table Sizes......................21
9.3.6. Automatic Gain Control..............................21
9.3.7. Device and Network Integrity........................21
9.4. Additional Performance Requirements......................21
9.4.1. Data Rate Performance...............................21
9.4.2. Firmware Upgrades...................................22
9.4.3. Route Persistence...................................22
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1. Terminology
For description of the terminology used in this specification, please
see [I-D.ietf-roll-terminology].
2. Introduction
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 networks. Pursuant to this effort, this document
defines the IPv6 routing requirements for building automation.
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.
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
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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.
Section 3 describes the necessary background to understand the
context of building automation including the sensor, actuator, area
controller and zone controller layers of the topology; typical device
density; and installation practices.
Section 4 defines the traffic flow of the aforementioned sensors,
actuators and controllers in commercial buildings.
Section 5 defines the full set of IPv6 routing requirements for
commercial buildings.
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.
Sections 3 and Appendix A are mainly included for educational
purposes.
The expressed aim of this document is to provide the set of IPv6
routing requirements for LLNs in buildings as described in Section 5.
3. Overview of Building Automation Networks
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,
controllers and user interface devices that interoperate to provide a
safe and comfortable environment while constraining energy costs.
An FMS may is divided functionally across alike, but different
building subsystems such as heating, ventilation and air conditioning
(HVAC); Fire; Security; Lighting; Shutters and Elevator control
systems as denoted in Figure 1.
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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
3.2. Building Systems Equipment
3.2.1. Sensors/Actuators
As Figure 1 indicates an FMS may be composed of many functional
stacks or silos that are interoperably woven together via Building
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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
at the edge of the network structure providing environmental data
into the system. The actuators are the sensors' counterparts
modifying the characteristics of the system based on the sensor data
and the applications deployed.
3.2.2. 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.
3.2.3. 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.
3.3. Equipment Installation Methods
Commercial controllers have been traditionally deployed in a facility
using serial media following the EIA-485 electrical standard
operating nominally at 76800 baud with distances upward to 15000
feet. EIA-485 is a multi-drop media allowing upwards to 255 devices
to be connected to a single trunk.
Wired FMS installation is a multifaceted procedure depending on the
extent of the system and the software interoperability requirement.
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However, at the sensor/actuator and controller level, the procedure
is typically a two or three step process.
The installer arrives on-site during the construction of the building
prior to drywall and ceiling installation. The installer allocates
wall space installs the controller and sensor networks. The Building
Controllers and Enterprise network are not normally installed until
months later. The electrician completes the task by running a
verification procedure that verifies proper wired or wireless
continuity between the devices.
Months later, 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
in place. The Building Controllers are completely commissioned using
a crossover cable or a temporary IP switch together with static IP
addresses.
After occupancy, when the IP network is operational, the FMS often
connects to the enterprise network. Dynamic IPs replace static IPs.
VLANs oft time segregate the facility and IT systems. For multi-
building multi-site facilities VPNs, NATs and firewalls are also
introduced.
3.4. 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.
3.4.1. 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
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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.
3.4.2. 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.
3.4.3. 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.
3.4.4. 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. Traffic Pattern
The independent nature of the automation subsystems within a building
plays heavy onto the network traffic patterns. Much of the real-time
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sensor environmental data and actuator control stays within the local
LLN environment; while alarming and other event data will percolate
to higher layers.
Each sensor in the LLN unicasts P2P about 200 bytes of sensor data to
its associated controller each minute and expects an application
acknowledgement unicast returned from the destination. Each
controller unicasts messages at a nominal rate of 6kB/min to peer or
supervisory controllers. 30% of each node's packets are destined for
other nodes within the LLN. 70% of each node's packets are destined
for an aggregation device (MP2P)and routed off the LLN. These
messages also require a unicast acknowledgement from the destination.
The above values assume direct node-to-node communication; meshing
and error retransmissions are not considered.
Multicasts (P2MP) to all nodes in the LLN occur for node and object
discovery when the network is first commissioned. This data is
typically a one-time bind that is henceforth persisted. Lighting
systems will also readily use multicasting during normal operations
to turn banks of lights 'on' and 'off' simultaneously.
FMS systems may be either polled or event based. Polled data systems
will generate a uniform and constant packet load on the network.
Polled architectures, however have proven not scalable. Today, 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 initial sensor 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 also need to reference peers periodically for sensor
data or to coordinate operation across systems. Normally, though,
data will migrate from the sensor level upwards through the local,
area then supervisory level. Traffic bottlenecks will typically form
at the funnel point from the area controllers to the supervisory
controllers.
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 rate
is small and the network will not saturate. An overall network
traffic load of 6KBps is typical at quiescence. However, upon any
power loss, the control loops and real-time data quickly atrophy. A
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ten minute power outage may require many hours to regain building
control. Traffic flow may increase ten-fold until the building
control stabilizes.
Power disruptions are unexpected and in most cases will immediately
impact lines-powered devices. Power disruptions however, are
transparent to battery powered devices. These devices will continue
to attempt to access the LLN during the outage. Battery powered
devices designed to buffer data that has not been delivered will
further stress the network operation when power returns.
Upon restart, lines-powered devices will naturally dither due to
primary equipment delays or variance in the device self-tests.
However, most lines-powered devices will be ready to access the LLN
network within 10 seconds of power up. Empirical testing indicates
that routes 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 route optimization as the
network stabilizes.
5. Building Automation Routing Requirements
Following are the building automation routing requirements for
networks used to integrate building sensor, actuator and control
products. These requirements are written not presuming any
preordained network topology, physical media (wired) or radio
technology (wireless).
5.1. Device and Network Commissioning
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.
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
operation, yet be sure the operation of the light switch is
associated to the proper ballast.
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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. 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.
LLN nodes SHOULD be testable for end-to-end link connectivity and
application conformance without requiring other network
infrastructure.
5.1.3. 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 requiring reconfiguration. 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.
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5.2.1. Network Domain
The routing protocol MUST be able to support networks with at least
2000 nodes where 1000 nodes would act as routers and the other 1000
nodes would be hosts. 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.
A network device MUST be able to communicate in a point-to-point
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,
such as tracking capital equipment (e.g. wheel chairs) in medical
facilities, 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.
Network configuration should allow devices to be configured as
routers or hosts.
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5.3.1.1. Device Mobility within the LLN
An LLN typically spans a single floor in a commercial building.
Mobile devices may move within this LLN. For example, a wheel chair
may be moved from one room on the floor to another room on the same
floor.
A mobile LLN device that moves within the confines of the same LLN
SHOULD reestablish end-to-end communication to a fixed device also in
the LLN within 5 seconds after it ceases movement. The LLN network
convergence time should be less than 10 seconds once the mobile
device stops moving.
5.3.1.2. Device Mobility across LLNs
A mobile device may move across LLNs, such as a wheel chair being
moved to a different floor.
A mobile device that moves outside its original LLN SHOULD
reestablish end-to-end communication to a fixed device also in the
new LLN within 10 seconds after the mobile device ceases movement.
The network convergence time should be less than 20 seconds once the
mobile device stops moving.
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 memory footprint on host 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 routers
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.
5.4.3. Sleeping Devices
Sensing devices will, in some cases, utilize battery power or energy
harvesting techniques for power and will operate mostly in a sleep
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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, battery life (2000mah) needs to extend for at least 5
years when the sensing device is transmitting its data(200 octets)
once per minute over a low power transceiver (25ma). This requires
that sleeping devices MUST upon awakening route its data to its
destination and receive an ACK from the destination within 20msec.
Additionally, awakened sleepy devices MUST be able to receive
awaiting inbound data within 20msec.
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 route calculation; then deliver the
packet to the assigned proxy for later delivery to the sleeping
device upon its next awakened cycle.
5.5. Addressing
Facility Management systems require different communication schemes
to solicit or post network information. Multicasts or anycasts need
be used to resolve unresolved references within a device when the
device first joins the network.
As with any network communication, multicasting should be minimized.
This is especially a problem for small embedded devices with limited
network bandwidth. Multicasts are typically used for network joins
and application binding in embedded systems. Routing MUST support
anycast, unicast, and multicast.
5.6. Manageability
In addition to the initial installation of the system, it is equally
important for the ongoing maintenance of the system to be simple and
inexpensive.
5.6.1. Diagnostics
To improve diagnostics, the routing protocol SHOULD be able to be
placed in and out of 'verbose' mode. Verbose mode is a temporary
debugging mode that provides additional communication information
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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
route quality; number of hops; available alternate active routes with
associated costs. Route 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
routes or any other criteria deemed by ROLL as the route cost
differentiator.
5.7. Route Selection
Route selection determines reliability and quality of the
communication paths among the devices by optimizing routes over time
and resolving any nuances developed at system startup when nodes are
asynchronously adding themselves to the network.
5.7.1. Route 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 routes. These metrics SHOULD reflect
metrics such as signal strength, available bandwidth, hop count,
energy availability and communication error rates.
5.7.2. Route Adaptation
Communication routes MUST adapt toward the chosen metric(s) (e.g.
signal quality) optimality in time.
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
route.
5.7.4. Route Discovery Time
Mission critical commercial applications (e.g. Fire, Security)
require reliable communication and guaranteed end-to-end delivery of
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all messages in a timely fashion. Application layer time-outs must
be selected judiciously to cover anomalous conditions such as lost
packets and/or route discoveries; yet not be set too large to over
damp the network response. If route discovery occurs during packet
transmission time (proactive routing), it SHOULD NOT add more than
120ms of latency to the packet delivery time.
5.7.5. Route Preference
The routing protocol SHOULD allow for the support of manually
configured static preferred routes.
5.7.6. 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
5 or less hops in each direction. This requirement assumes network
quiescence and a negligible turnaround time at the destination node.
5.7.7. Prioritized Routing
Network and application packet routing prioritization MUST be
supported to assure that mission critical applications (e.g. Fire
Detection) cannot be deferred while less critical applications access
the network.
5.8. Security Requirements
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, security policies
must be facile to allow for no security policy during the
installation phase (prior to building occupancy), yet easily raise
the security level network wide during the commissioning phase of the
system.
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5.8.1. 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
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.
5.8.2. Encryption
5.8.2.1. 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 route to have the application key.
5.8.2.2. 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.
5.8.3. 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.
5.8.4. 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'
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cycle to assure that sleeping devices can readily and efficiently
access then network.
6. IANA Considerations
This document includes no request to IANA.
7. 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.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. 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.
9. 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.
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9.1. Additional Commercial Product Requirements
9.1.1. 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.
9.1.2. 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.
9.2. Additional Installation and Commissioning Requirements
9.2.1. 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).
9.3. Additional Network Requirements
9.3.1. TCP/UDP
Connection based and connectionless services must be supported
9.3.2. 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.
9.3.3. Packet Reliability
In building automation, it is required for the network to meet the
following minimum criteria :
< 1% MAC layer errors on all messages; After no more than three
retries
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< .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.
9.3.4. 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.
9.3.5. Adjustable Routing Table Sizes
The routing protocol must allow constrained nodes to hold an
abbreviated set of routes. That is, the protocol should not mandate
that the node routing tables be exhaustive.
9.3.6. 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.
9.3.7. 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. Router should maintain previous packet flow
information temporally to minimize overall network overhead.
9.4. Additional Performance Requirements
9.4.1. Data Rate Performance
An effective data rate of 20kbits/s is the lowest acceptable
operational data rate acceptable on the network.
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9.4.2. Firmware Upgrades
To support high speed code downloads, routing should 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 should 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.
9.4.3. Route 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.
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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: ???
Email: wouter@vooruit.be
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