Internet Engineering Task Force M. Ersue, Ed.
Internet-Draft Nokia Siemens Networks
Intended status: Informational D. Romascanu, Ed.
Expires: August 18, 2013 Avaya
J. Schoenwaelder, Ed.
Jacobs University Bremen
February 14, 2013
Management of Networks with Constrained Devices: Problem Statement, Use
Cases and Requirements
draft-ersue-constrained-mgmt-03
Abstract
This document provides a problem statement and discusses the use
cases and requirements for the management of networks with
constrained devices.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Class of Networks in Focus . . . . . . . . . . . . . . . . 7
1.4. Constrained Device Deployment Options . . . . . . . . . . 10
1.5. Management Topology Options . . . . . . . . . . . . . . . 11
1.6. Managing the Constrainedness of a Device or Network . . . 11
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 15
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. Environmental Monitoring . . . . . . . . . . . . . . . . . 17
3.2. Medical Applications . . . . . . . . . . . . . . . . . . . 17
3.3. Industrial Applications . . . . . . . . . . . . . . . . . 18
3.4. Home Automation . . . . . . . . . . . . . . . . . . . . . 19
3.5. Building Automation . . . . . . . . . . . . . . . . . . . 20
3.6. Energy Management . . . . . . . . . . . . . . . . . . . . 22
3.7. Transport Applications . . . . . . . . . . . . . . . . . . 23
3.8. Infrastructure Monitoring . . . . . . . . . . . . . . . . 24
3.9. Community Network Applications . . . . . . . . . . . . . . 25
3.10. Mobile Applications . . . . . . . . . . . . . . . . . . . 27
3.11. Automated Metering Infrastructure (AMI) . . . . . . . . . 29
3.12. MANET Concept of Operations (CONOPS) in Military . . . . . 31
4. Requirements on the Management of Networks with
Constrained Devices . . . . . . . . . . . . . . . . . . . . . 36
4.1. Management Architecture/System . . . . . . . . . . . . . . 36
4.2. Management protocols and data model . . . . . . . . . . . 41
4.3. Configuration management . . . . . . . . . . . . . . . . . 44
4.4. Monitoring functionality . . . . . . . . . . . . . . . . . 46
4.5. Self-management . . . . . . . . . . . . . . . . . . . . . 51
4.6. Security and Access Control . . . . . . . . . . . . . . . 52
4.7. Energy Management . . . . . . . . . . . . . . . . . . . . 54
4.8. SW Distribution . . . . . . . . . . . . . . . . . . . . . 56
4.9. Traffic management . . . . . . . . . . . . . . . . . . . . 56
4.10. Transport Layer . . . . . . . . . . . . . . . . . . . . . 57
4.11. Implementation Requirements . . . . . . . . . . . . . . . 59
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 61
6. Security Considerations . . . . . . . . . . . . . . . . . . . 62
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 63
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 64
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9.1. Normative References . . . . . . . . . . . . . . . . . . . 65
9.2. Informative References . . . . . . . . . . . . . . . . . . 65
Appendix A. Related Development in other Bodies . . . . . . . . . 67
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A.1. ETSI TC M2M . . . . . . . . . . . . . . . . . . . . . . . 67
A.2. OASIS . . . . . . . . . . . . . . . . . . . . . . . . . . 68
A.3. OMA . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
A.4. IPSO Alliance . . . . . . . . . . . . . . . . . . . . . . 69
Appendix B. Related Research Projects . . . . . . . . . . . . . . 71
Appendix C. Open issues . . . . . . . . . . . . . . . . . . . . . 72
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 73
D.1. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 73
D.2. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 74
D.3. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 76
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1. Introduction
1.1. Overview
Small devices with limited CPU, memory, and power resources, so
called constrained devices (aka. sensor, smart object, or smart
device) can constitute a network. Such a network of constrained
devices itself may be constrained or challenged, e.g. with unreliable
or lossy channels, wireless technologies with limited bandwidth and a
dynamic topology, needing the service of a gateway or proxy to
connect to the Internet. In other scenarios, the constrained devices
can be connected to a non-constrained network using off-the-shelf
protocol stacks.
Constrained devices might be in charge of gathering information in
diverse settings including natural ecosystems, buildings, and
factories and send the information to one or more server stations.
Constrained devices may work under severe resource constraints such
as limited battery and computing power, little memory and
insufficient wireless bandwidth, and communication capabilities. A
central entity, e.g., a base station or controlling server, might
have more computational and communication resources and can act as a
gateway between the constrained devices and the application logic in
the core network.
Today diverse size of small devices with different resources and
capabilities are becoming connected. Mobile personal gadgets,
building-automation devices, cellular phones, Machine-to-machine
(M2M) devices, etc. benefit from interacting with other "things" in
the near or somewhere in the Internet. With this the Internet of
Things (IoT) becomes a reality build up of uniquely identifiable
objects (things). And over the next decade, this could grow to
trillions of constrained devices and will greatly increase the
Internet's size and scope.
Network management is characterized by monitoring network status,
detecting faults, and inferring their causes, setting network
parameters, and carrying out actions to remove faults, maintain
normal operation, and improve network efficiency and application
performance. The traditional network management application
periodically collects information from a set of elements that are
needed to manage, processes the data, and presents them to the
network management users. Constrained devices, however, often have
limited power, low transmission range, and might be unreliable. They
might also need to work in hostile environments with advanced
security requirements or need to be used in harsh environments for a
long time without supervision. Due to such constraints, the
management of a network with constrained devices offers different
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type of challenges compared to the management of a traditional IP
network.
The IETF has already done a lot of standardization work to enable the
communication in IP networks and to manage such networks as well as
the manifold type of nodes in these networks [RFC6632]. However, the
IETF so far has not developed any specific technologies for the
management of constrained devices and the networks comprised by
constrained devices. IP-based sensors or constrained devices in such
an environment, i.e., devices with very limited memory and CPU
resources, use today application-layer protocols in an ad-hoc manner
to do simple resource management and monitoring.
This document raises the questions on and aims to understand the use
cases and requirements for the management of a network with
constrained devices. The document especially aims to avoid
recommending any particular solutions. Section 1.3 and Section 1.5
describe different topology options for the networking and management
of constrained devices. Section 1.4 explains different deployment
options for the networking of constrained devices. Section 2
provides a problem statement on the issue of the management of
networked constrained devices. Section 3 lists diverse use cases and
scenarios for the management from the network as well as from the
application point of view. Section 4 lists requirements on the
management of applications and networks with constrained devices.
Note that the requirements in Section 4 need to be seen as standalone
requirements. As of today this document does not recommend the
realization of a profile of requirements.
1.2. Terminology
Concerning constrained devices and networks this document generally
builds on the terminology defined in [LWIG-TERMS]. As such the terms
like Constrained Device, Constrained Network, etc. are defined in
[LWIG-TERMS].
The following terms are additionally used throughout this
documentation:
AMI: (Advanced Metering Infrastructure) A system including hardware,
software, and networking technologies that measures, collects, and
analyzes energy usage, and communicates with a hierarchically
deployed network of metering devices, either on request or on a
schedule.
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C0: Class 0 constrained device as defined in Section 3. of [LWIG-
TERMS].
C1: Class 1 constrained device as defined in Section 3. of [LWIG-
TERMS].
C2: Class 2 constrained device as defined in Section 3. of [LWIG-
TERMS].
Client: The originating endpoint of a request; the destination
endpoint of a response.
Intermediary entity: As defined in the CoAP document an intermediary
entity can be a CoAP endpoint that acts both as a server and as a
client towards (possibly via further intermediaries) an origin
server. An intermediary entity can be used to support
hierarchical management.
Network of Constrained Devices: A network to which constrained
devices are connected. It may or may not be a Constrained Network
(see [LWIG-TERMS] for the definition of the term Constrained
Network).
M2M: (Machine to Machine) stands for the automatic data transfer
between devices of different kind. In M2M scenarios a device
(such as a sensor or meter) captures an event, which is relayed
through a network (wireless, wired or hybrid) to an application.
MANET: Mobile Ad-hoc Networks, a self-configuring and
infrastructureless network of mobile devices connected by wireless
technologies.
Mote: A sensor node in a wireless network that is capable of
performing some limited processing, gathering sensory information
and communicating with other connected nodes in the network.
Server: The destination endpoint of a request; the originating
endpoint of a response.
Smart Grid: An electrical grid that uses communication technologies
to gather and act on information in an automated fashion to
improve the efficiency, reliability and sustainability of the
production and distribution of electricity.
Smart Meter: An electrical meter (in the context of a Smart Grid)
that records consumption of electric energy in intervals of an
hour or less and communicates that information at least daily back
to the utility network for monitoring and billing purposes.
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For a detailed discussion on the constrained networks as well as
classes of constrained devices and their capabilities please see
[LWIG-TERMS].
1.3. Class of Networks in Focus
In this document we differentiate following type of networks
concerning their transport and communication technologies:
(Note that a network in general can involve constrained and non-
constrained devices.)
o Wireline non-constrained networks (CN0), e.g. an Ethernet-LAN with
non-constrained and constrained devices involved.
o A combination of wireline and wireless networks (CN1), which may
or may not be mesh-based but have a multi-hop connectivity between
constrained devices, utilizing dynamic routing in both the
wireless and wireline portions of the network. CN1 usually
support highly distributed applications with many nodes (e.g.
environmental monitoring). CN1 tend to deal with large-scale
multipoint-to-point systems with massive data flows. Wireless
Mesh Networks (WMN), as a specific type of CN1 networks, use off-
the-shelf radio technology such as Wi-Fi, WiMax, and cellular
3G/4G. WMNs are reliable based on the redundancy they offer and
have often a more planned deployment to provide dynamic and cost
effective connectivity over a certain geographic area.
o A combination of wireline and wireless networks with point-to-
point or point-to-multipoint communication (CN2) generally with
single-hop connectivity to constrained devices, utilizing static
routing over the wireless network. CN2 support short-range,
point-to-point, low-data-rate, source-to-sink type of applications
such as RFID systems, light switches, fire and smoke detectors,
and home appliances. CN2 usually support confined short-range
spaces such as a home, a factory, a building, or the human body.
IEEE 802.15.1 (Bluetooth) and IEEE 802.15.4 are well-known
examples of applicable standards for CN2 networks.
o Mobile Adhoc networks (MANET) are self-configuring
_infrastructureless_ networks of mobile devices connected by
wireless technologies. MANETs are based on point-to-point
communications of devices moving independently in any direction
and changing the links to other devices frequently. MANET devices
do act as a router to forward traffic unrelated to their own use.
A CN0 is used for specific applications like Building Automation or
Infrastructure Monitoring. However, CN1 and CN2 networks are
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especially in the interest of the analysis on the management of
constrained devices in this document.
Furthermore different network characteristics are determined by
multiple dimensions: dynamicity of the topology, bandwidth, and loss
rate. In the following, each dimension is explained, and networks in
scope for this document are outlined:
Network Topology:
The topology of a network can be represented as a graph, with edges
(i.e., links) and vertices (routers and hosts). Examples of
different topologies include "star" topologies (with one central node
and multiple nodes in one hop distance), tree structures (with each
node having exactly one parent), directed acyclic graphs (with each
node having one or more parents), clustered topologies (where one or
more "cluster heads" are responsible for a certain area of the
network), mesh topologies (fully distributed), etc.
Management protocols may take advantage of specific network
topologies, for example by distributing large-scale management tasks
amongst multiple distributed network management stations (e.g., in
case of a mesh topology), or by using a hierarchical management
approach (e.g., in case of a tree topology). These different
management topology options are described in Section 1.6.
Note that in certain network deployments, such as community ad hoc
networks (as described in Section 3.9, the topology is not pre-
planned, and thus may be unknown for management purposes. In other
use cases, such as industrial applications (as described in
Section 3.3, the topology may be designed in advance and therefore
taken advantage of when managing the network.
Dynamicity of the network topology:
The dynamicity of the network topology determines the rate of change
of the graph per time. Such changes can occur due to different
factors, such as mobility of nodes (e.g., in MANETs or cellular
networks), duty cycles (for low-power devices enabling their network
interface only periodically to transmit or receive packets), or
unstable links (in particular wireless links with strongly
fluctuating link quality).
Examples of different levels of dynamicity of the topology are
Ethernets (with typically a very static topology) on the one side,
and low-power and lossy networks (LLNs) on the other side. LLNs
nodes often using duty cycles, operate on unreliable wireless links
and are potentially mobile (e.g. for sensor networks).
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The more the topology is dynamic, the more routing, transport and
application layer protocols have to cope with interrupted
connectivity and/or longer delays. For example, management protocols
(with a given underlying transport protocol) that expect continuous
session flows without changes of routes during a communication flow,
may fail to operate.
Networks with a very low dynamicity (e.g. Ethernet) with no or
infrequent topology changes (e.g. less than once every 30 minutes),
are in-scope of this document if they are used with constrained
devices (see e.g. the use case "Building Automation" in Section 3.5).
Traffic flows:
The traffic flow in a network determines from which sources data
traffic is sent to which destinations in the network. Several
different traffic flows are defined in [I-D.ietf-roll-terminology],
including "point-to-point" (P2P), "multipoint-to-point" (MP2P), and
"point-to-multipoint" (P2MP) flows as:
o P2P: Point To Point. This refers to traffic exchanged between two
nodes (regardless of the number of hops between the two nodes).
o P2MP: Point-to-Multipoint traffic refers to traffic between one
node and a set of nodes. This is similar to the P2MP concept in
Multicast or MPLS Traffic Engineering.
o MP2P: Multipoint-to-Point is used to describe a particular traffic
pattern (e.g. MP2P flows collecting information from many nodes
flowing inwards towards a collecting sink).
If one of these traffic patterns is predominant in a network,
protocols (routing, transport, application) may be optimized for the
specific traffic flow. For example, in a network with a tree
topology and MP2P traffic, collection tree protocols are efficient to
send data from the leaves of the tree to the root of the tree, via
each node's parent.
Bandwidth:
The bandwidth of the network is the amount of data that can be sent
per time between two communication end-points. It is usually
determined by the link with the minimum bandwidth on the path from
the source to the destination of data packets. The bandwidth in
networks can range from a few Kilobytes per second (such as on some
802.15.4 link layers) to many Gigabytes per second (e.g., on fiber
optics).
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For management purposes, the management protocol typically requires
to send information between the network management station and the
clients, for monitoring or control purposes. If the available
bandwidth is insufficient for the management protocol, packets will
be buffered and eventually dropped, and thus management is not
possible with such a protocol.
Networks without bandwidth limitation (e.g. Ethernet) are in-scope
of this document if they are used with constrained devices (see the
use case "Building Automation" in Section 3.5).
Loss rate:
The loss rate (or bit error rate) is the number of bit errors divided
by the total number of bits transmitted. For wired networks, loss
rates are typically extremely low, e.g. around 10^-12 or 10^-13 for
the latest 10Gbit Ethernet. For wireless networks, such as 802.15.4,
the bit error rate can be as high as 10^-1 to 10^-0 in case of
interferences.Even when using a reliable transport protocol,
management operations can fail if the loss rate is too high, unless
they are specifically designed to cope with these situations.
Note: The discussion on the management requirements of MANETs is
currently not in the focus of this document. The use case in
Section 3.4 has been provided to make it clear how a MANET-based
application differs from others.
1.4. Constrained Device Deployment Options
We differentiate following Deployment options for the constrained
devices:
o a network of constrained devices, which communicate with each
other,
o Constrained devices, which are connected directly to the Internet
or an IP network
o A network of constrained devices which communicate with a gateway
or proxy with more communication capabilities acting possibly as a
representative of the device to entities in the non-constrained
network
o Constrained devices, which are connected to the Internet or an IP
network via a gateway/proxy
o A hierarchy of constrained devices, e.g., a network of C0 devices
connected to one or more C1 devices - connected to one or more C2
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devices - connected to one or more gateways - connected to some
application servers or NMS system
o The possibility of device grouping (possibly in a dynamic manner)
such as that the grouped devices can act as one logical device at
the edge of the network and one device in this group can act as
the managing entity
1.5. Management Topology Options
We differentiate following options for the management of networks of
constrained devices:
o A network of constrained devices managed by one central manager.
A logically centralized management might be implemented in a
hierarchical fashion for scalability and robustness reasons. The
manager and the management application logic might have a gateway/
proxy in between or might be on different nodes in different
networks, e.g., management application running on a cloud server.
o Distributed management, where a constrained network is managed by
more than one manager. Each manager controls a subnetwork and may
communicate directly with other manager stations in a cooperative
fashion. The distributed management may be weakly distributed,
where functions are broken down and assigned to many managers
dynamically, or strongly distributed, where almost all managed
things have embedded management functionality and explicit
management disappears, which usually comes with the price that the
strongly distributed management logic now needs to be managed.
o Hierarchical management, where a hierarchy of constrained networks
are managed by the managers at their corresponding hierarchy
level. I.e. each manager is responsible for managing the nodes in
its sub-network. It passes information from its sub-network to
its higher-level manager, and disseminates management functions
received from the higher-level manager to its sub-network.
Hierarchical management is essentially a scalability mechanism,
logically the decision-making may be still centralized.
1.6. Managing the Constrainedness of a Device or Network
The capabilities of a constrained device or network and the
constrainedness thereof influence and have an impact on the
requirements for the management of such network or devices.
A constrained device:
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o might only support an unreliable radio with lossy links, i.e. the
client and server of a management protocol need to gracefully
ignore incomplete commands or repeat commands as necessary.
o might only be able to go online from time-to-time, where it is
reachable, i.e. a command might be necessary to repeat after a
longer timeout or the timeout value with which one endpoint waits
on a response needs to be sufficiently high.
o might only be able to support a limited operating time (e.g. based
on the available battery), i.e. the devices need to economize
their energy usage with suitable mechanisms and the managing
entity needs to monitor and control the energy status of the
constrained devices it manages.
o might only be able to support one simple communication protocol,
i.e. the management protocol needs to be possible to downscale
from constrained (C2) to very constrained (C0) devices with
modular implementation and a very basic version with just a few
simple commands.
o might only be able to support limited or no user and/or transport
security, i.e. the management system needs to support a less-
costly and simple but sufficiently secure authentication
mechanism.
o might not be able to support compression and decompression of
exchanged data based on limited CPU power, i.e. an intermediary
entity which is capable of data compression should be able to
communicate with both, devices, which support data compression
(e.g. C2) and devices, which do not support data compression
(e.g. C1 and C0).
o might only be able to support very simple encryption, i.e. it
would be efficient if the devices use cryptographic algorithms
that are supported in hardware.
o might only be able to communicate with one single managing entity
and cannot support the parallel access of many managing entities.
o might depend on a self-configuration feature, i.e. the managing
entity might not know all devices in a network and the device
needs to be able to initiate connection setup for the device
configuration.
o might depend on self- or neighbor-monitoring feature, i.e. the
managing entity might not be able to monitor all devices in a
network continuously.
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o might only be able to communicate with its neighbors, i.e. the
device should be able to get its configuration from a neighbor.
o might only be able to support parsing of data models with limited
size, i.e. the device data models need to be compact containing
the most necessary data and if possible parsable as a stream.
o might only be able to support a limited or no failure detection,
i.e. the managing entity needs to handle the situation, where a
failure does not get detected or gets detected late gracefully
e.g. with asking repeatedly.
o might only be able to support the reporting of just one or a
limited set failure types.
o might only be able to support a limited set of notifications,
possible only an "I-am-alive" message.
o might only be able to support a soft-reset from failure recovery.
o might possibly generate a huge amount of redundant reporting data,
i.e. the intermediary management entity should be able to filter
and aggregate redundant data.
A constrained network:
o might only support an unreliable radio with lossy links, i.e. the
client and server of a management protocol need to repeat commands
as necessary or gracefully ignore incomplete commands.
o might be necessary to manage based on multicast communication,
i.e. the managing entity needs to be prepared to configure many
devices at once based on the same data model.
o might have a very large topology supporting 10.000 or more nodes
for some applications and as such node naming is a specific issue
for constrained networks.
o must be able to self-organize, i.e. given the large number of
nodes and their potential placement in hostile locations and
frequently changing topology, manual configuration is typically
not feasible. As such the network must be able to reconfigure
itself so that it can continue to operate properly and support
reliable connectivity.
o needs a management solution, which is energy-efficient, using as
little wireless bandwidth as possible since communication is
highly energy demanding.
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o needs to support localization schemes to determine the location of
devices since the devices might be moving and location information
is important for some applications.
o needs a management solution, which is scalable as the network may
consist of thousands of nodes and may need to be extended
continuously.
o needs to provide fault tolerance. Faults in network operation
including hardware and software errors, failures detected by the
transport protocol and other self-monitoring mechanisms can be
used to provide fault tolerance.
o might require new management capabilities: for example, network
coverage information and a constrained device power-distribution-
map.
o might require a new management function for data management, since
the type and amount of data collected in constrained networks is
different from those of the traditional networks.
o might also need energy-efficient key management algorithms for
security.
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2. Problem Statement
The terminology for the "Internet of Things" is still nascent, and
depending on the network type or layer in focus diverse technologies
and terms are in use. Common to all these considerations is the
"Things" or "Objects" are supposed to have physical or virtual
identities using interfaces to communicate. In this context, we need
to differentiate between the Constrained and Smart Devices identified
by an IP address compared to virtual entities such as Smart Objects,
which can be identified as a resource or a virtual object by using a
unique identifier. Furthermore, the smart devices usually have a
limited memory and CPU power as well as aim to be self-configuring
and easy to deploy.
However, the tininess of the network nodes requires a rethinking of
the protocol characteristics concerning power consumption,
performance, memory, and CPU usage. As such, there is a demand for
protocol simplification, energy-efficient communication, less CPU
usage and small memory footprint.
On the application layer the IETF is already developing protocols
like the Constrained Application Protocol (CoAP) [I-D.ietf-core-coap]
supporting constrained devices and networks e.g., for smart energy
applications or home automation environments. The deployment of such
an environment involves in fact many, in some scenarios up to million
small devices (e.g. smart meters), which produce a huge amount of
data. This data needs to be collected, filtered, and pre-processed
for further use in diverse services.
Considering the high number of nodes to deploy, one has to think on
the manageability aspects of the smart devices and plan for easy
deployment, configuration, and management of the networks of
constrained devices as well as the devices themselves. Consequently,
seamless monitoring and self-configuration of such network nodes
becomes more and more imperative. Self-configuration and self-
management is already a reality in the standards of some of the
bodies such as 3GPP. To introduce self-configuration of smart
devices successfully a device-initiated connection establishment is
required.
A simple application layer protocol, such as CoAP, is essential to
address the issue of efficient object-to-object communication and
information exchange. Such an information exchange should be done
based on interoperable data models to enable the exchange and
interpretation of diverse application and management related data.
In an ideal world, we would have only one network management protocol
for monitoring, configuration, and exchanging management data,
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independently of the type of the network (e.g., Smart Grid, wireless
access, or core network). Furthermore, it would be desirable to
derive the basic data models for constrained devices from the core
models used today to enable reuse of functionality and end-to-end
information exchange. However, the current management protocols seem
to be too heavyweight compared to the capabilities the constrained
devices have and are not applicable directly for the use in a network
of constrained devices. Furthermore, the data models addressing the
requirements of such smart devices need yet to be designed.
The IETF so far has not developed any specific technologies for the
management of constrained devices and the networks comprised by
constrained devices. IP-based sensors or constrained devices in such
an environment, i.e., devices with very limited memory and CPU
resources, use today, e.g., application-layer protocols to do simple
resource management and monitoring. This might be sufficient for
some basic cases, however, there is a need to reconsider the network
management mechanisms based on the new, changed, as well as reduced
requirements coming from smart devices and the network of such
constrained devices. Albeit it is questionable whether we can take
the same comprehensive approach we use in an IP network also for the
management of constrained devices. Hence, the management of a
network with constrained devices might become necessary to design as
much as possible simplified and less complex.
As the Section 1.6 highlights, there are diverse characterists of
constrained devices or networks, which stem from their constraindness
and therefor have an impact on the requirements for the management of
such a network with constrained devices. The use cases discussed in
Section 3 show that the requirements on constrained networks are
manifold and need to be analyzed from different angles, e.g.
concerning the design of the management architecture, the selection
of the appropriate protocol features as well as the specific issues
which are new in the context of constrained devices. Examples of
such issues are e.g. the careful management of the scarce energy
resources, the necessity for self-organization and self-management of
such devices but also the implementation considerations to enable the
use of common communication technologies on a constrained hardware in
an efficient manner. For an exhaustive list of issues and
requirements, which need to be addressed for the management of a
network with constrained devices please see Section 1.6 and
Section 4.
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3. Use Cases
This section discusses some application scenarios where networks of
constrained devices are expected to be deployed. For each
application scenario, we first briefly describe the characteristics
followed by a discussion how network management can be provided, who
is likely going to be responsible for it, and on which time-scale
management operations are likely to be carried out.
3.1. Environmental Monitoring
Environmental monitoring applications are characterized by the
deployment of a number of sensors to monitor emissions, water
quality, or even the movements and habits of wildlife. Other
applications in this category include earthquake or tsunami early-
warning systems. The sensors often span a large geographic area,
they can be mobile, and they are often difficult to replace.
Furthermore, the sensors are usually not protected against tampering.
Management of environmental monitoring applications is largely
concerned with the monitoring whether the system is still functional
and the roll-out of new constrained devices in case the system looses
too much of its structure. The constrained devices themselves need
to be able to establish connectivity (auto-configuration) and they
need to be able to deal with events such as loosing neighbors or
being moved to other locations.
Management responsibility typically rests with the organization
running the environmental monitoring application. Since these
monitoring applications must be designed to tolerate a number of
failures, the time scale for detecting and recording failures is for
some of these applications likely measured in hours and repairs might
easily take days. However, for certain environmental monitoring
applications, much tighter time scales may exist and might be
enforced by regulations (e.g., monitoring of nuclear radiation).
3.2. Medical Applications
Constrained devices can be seen as an enabling technology for
advanced and possibly remote health monitoring and emergency
notification systems, ranging from blood pressure and heart rate
monitors to advanced devices capable to monitor implanted
technologies, such as pacemakers or advanced hearing aids. Medical
sensors may not only be attached to human bodies, they might also
exist in the infrastructure used by humans such as bathrooms or
kitchens. Medical applications will also be used to ensure
treatments are being applied properly and they might guide people
losing orientation. Fitness and wellness applications, such as
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connected scales or wearable heart monitors, encourage consumers to
exercise and empower self-monitoring of key fitness indicators.
Different applications use Bluetooth, Wi-Fi or Zigbee connections to
access the patient's smartphone or home cellular connection to access
the Internet.
Constrained devices that are part of medical applications are managed
either by the users of those devices or by an organization providing
medical (monitoring) services for physicians. In the first case,
management must be automatic and or easy to install and setup by
average people. In the second case, it can be expected that devices
be controlled by specially trained people. In both cases, however,
it is crucial to protect the privacy of the people to which medical
devices are attached. Even though the data collected by a heart beat
monitor might be protected, the pure fact that someone carries such a
device may need protection. As such, certain medical appliances may
not want to participate in discovery and self-configuration protocols
in order to remain invisible.
Many medical devices are likely to be used (and relied upon) to
provide data to physicians in critical situations since the biggest
market is likely elderly and handicapped people. As such, fault
detection of the communication network or the constrained devices
becomes a crucial function that must be carried out with high
reliability and, depending on the medical appliance and its
application, within seconds.
3.3. Industrial Applications
Industrial Applications and smart manufacturing refer not only to
production equipment, but also to a factory that carries out
centralized control of energy, HVAC (heating, ventilation, and air
conditioning), lighting, access control, etc. via a network. For the
management of a factory it is becoming essential to implement smart
capabilities. From an engineering standpoint, industrial
applications are intelligent systems enabling rapid manufacturing of
new products, dynamic response to product demand, and real-time
optimization of manufacturing production and supply chain networks.
Potential industrial applications e.g. for smart factories and smart
manufacturing are:
o Digital control systems with embedded, automated process controls,
operator tools, as well as service information systems optimizing
plant operations and safety.
o Asset management using predictive maintenance tools, statistical
evaluation, and measurements maximizing plant reliability.
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o Smart sensors detecting anomalies to avoid abnormal or
catastrophic events.
o Smart systems integrated within the industrial energy management
system and externally with the smart grid enabling real-time
energy optimization.
Sensor networks are an essential technology used for smart
manufacturing. Measurements, automated controls, plant optimization,
health and safety management, and other functions are provided by a
large number of networked sectors. Data interoperability and
seamless exchange of product, process, and project data are enabled
through interoperable data systems used by collaborating divisions or
business systems. Intelligent automation and learning systems are
vital to smart manufacturing but must be effectively integrated with
the decision environment. Wireless sensor networks (WSN) have been
developed for machinery Condition-based Maintenance (CBM) as they
offer significant cost savings and enable new functionalities.
Inaccessible locations, rotating machinery, hazardous areas, and
mobile assets can be reached with wireless sensors. WSNs can provide
today wireless link reliability, real-time capabilities, and quality-
of-service and enable industrial and related wireless sense and
control applications.
Management of industrial and factory applications is largely focused
on the monitoring whether the system is still functional, real-time
continuous performance monitoring, and optimization as necessary.
The factory network might be part of a campus network or connected to
the Internet. The constrained devices in such a network need to be
able to establish configuration themselves (auto-configuration) and
might need to deal with error conditions as much as possible locally.
Access control has to be provided with multi-level administrative
access and security. Support and diagnostics can be provided through
remote monitoring access centralized outside of the factory.
Management responsibility is typically owned by the organization
running the industrial application. Since the monitoring
applications must handle a potentially large number of failures, the
time scale for detecting and recording failures is for some of these
applications likely measured in minutes. However, for certain
industrial applications, much tighter time scales may exist, e.g. in
real-time, which might be enforced by the manufacturing process or
the use of critical material.
3.4. Home Automation
Home automation includes the control of lighting, heating,
ventilation, air conditioning, appliances, and entertainment devices
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to improve convenience, comfort, energy efficiency, and security. It
can be seen as a residential extension of building automation.
Home automation networks need a certain amount of configuration
(associating switches or sensors to actors) that is either provided
by electricians deploying home automation solutions or done by
residents by using the application user interface to configure (parts
of) the home automation solution. Similarly, failures may be
reported via suitable interfaces to residents or they might be
recorded and made available to electricians in charge of the
maintenance of the home automation infrastructure.
The management responsibility lies either with the residents or it
may be outsourced to electricians providing management of home
automation solutions as a service. The time scale for failure
detection and resolution is in many cases likely counted in hours to
days.
3.5. Building Automation
Building automation comprises the distributed systems designed and
deployed to monitor and control the mechanical, electrical and
electronic systems inside buildings with various destinations (e.g.,
public and private, industrial, institutions, or residential).
Advanced Building Automation Systems (BAS) may be deployed
concentrating the various functions of safety, environmental control,
occupancy, security. More and more the deployment of the various
functional systems is connected to the same communication
infrastructure (possibly Internet Protocol based), which may involve
wired or wireless communications networks inside the building.
Building automation requires the deployment of a large number (10-
100.000) of sensors that monitor the status of devices, and
parameters inside the building and controllers with different
specialized functionality for areas within the building or the
totality of the building. Inter-node distances between neighboring
nodes vary between 1 to 20 meters. Contrary to home automation in
building management all devices are known to a set of commissioning
tools and a data storage, such that every connected device has a
known origin. The management includes verifying the presence of the
expected devices and detecting the presence of unwanted devices.
Examples of functions performed by such controllers are regulating
the quality, humidity, and temperature of the air inside the building
and lighting. Other systems may report the status of the machinery
inside the building like elevators, or inside the rooms like
projectors in meeting rooms. Security cameras and sensors may be
deployed and operated on separate dedicated infrastructures connected
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to the common backbone. The deployment area of a BAS is typically
inside one building (or part of it) or several buildings
geographically grouped in a campus. A building network can be
composed of subnets, where a subnet covers a floor, an area on the
floor, or a given functionality (e.g. security cameras).
Some of the sensors in Building Automation Systems (for example fire
alarms or security systems) register, record and transfer critical
alarm information and therefore must be resilient to events like loss
of power or security attacks. This leads to the need that some
components and subsystems operate in constrained conditions and are
separately certified. Also in some environments, the malfunctioning
of a control system (like temperature control) needs to be reported
in the shortest possible time. Complex control systems can
misbehave, and their critical status reporting and safety algorithms
need to be basic and robust and perform even in critical conditions.
Building Automation solutions are deployed in some cases in newly
designed buildings, in other cases it might be over existing
infrastructures. In the first case, there is a broader range of
possible solutions, which can be planned for the infrastructure of
the building. In the second case the solution needs to be deployed
over an existing structure taking into account factors like existing
wiring, distance limitations, the propagation of radio signals over
walls and floors. As a result, some of the existing WLAN solutions
(e.g. IEEE 802.11 or IEEE 802.15) may be deployed. In mission-
critical or security sensitive environments and in cases where link
failures happen often, topologies that allow for reconfiguration of
the network and connection continuity may be required. Some of the
sensors deployed in building automation may be very simple
constrained devices for which class 0 or class 1 may be assumed.
For lighting applications, groups of lights must be defined and
managed. Commands to a group of light must arrive within 200 ms at
all destinations. The installation and operation of a building
network has different requirements. During the installation, many
stand-alone networks of a few to 100 nodes co-exist without a
connection to the backbone. During this phase, the nodes are
identified with a network identifier related to their physical
location. Devices are accessed from an installation tool to connect
them to the network in a secure fashion. During installation, the
setting of parameters to common values to enable interoperability may
occur (e.g. Trickle parameter values). During operation, the
networks are connected to the backbone while maintaining the network
identifier to physical location relation. Network parameters like
address and name are stored in DNS. The names can assist in
determining the physical location of the device.
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3.6. Energy Management
EMAN working group developed [I-D.ietf-eman-framework], which defines
a framework for providing Energy Management for devices within or
connected to communication networks. This document observes that one
of the challenges of energy management is that a power distribution
network is responsible for the supply of energy to various devices
and components, while a separate communication network is typically
used to monitor and control the power distribution network. Devices
that have energy management capability are defined as Energy Devices
and identified components within a device (Energy Device Components)
can be monitored for parameters like Power, Energy, Demand and Power
Quality. If a device contains batteries, they can be also monitored
and managed.
Energy devices differ in complexity and may include basic sensors or
switches, specialized electrical meters, or power distribution units
(PDU), and subsystems inside the network devices (routers, network
switches) or home or industrial appliances. An Energy Management
System is a combination of hardware and software used to administer a
network with the primary purpose being Energy Management. The
operators of such a system are either the utility providers or
customers that aim to control and reduce the energy consumption and
the associated costs. The topology in use differs and the deployment
can cover areas from small surfaces (individual homes) to large
geographical areas. EMAN requirements document
[I-D.ietf-eman-requirements] discusses the requirements for energy
management concerning monitoring and control functions.
It is assumed that Energy Management will apply to a large range of
devices of all classes and networks topologies. Specific resource
monitoring like battery utilization and availability may be specific
to devices with lower physical resources (device classes C0 or C1).
Energy Management is especially relevant to Smart Grid. A Smart Grid
is an electrical grid that uses data networks to gather and act on
energy and power-related information, in an automated fashion with
the goal to improve the efficiency, reliability, economics, and
sustainability of the production and distribution of electricity. As
such Smart Grid provides sustainable and reliable generation,
transmission, distribution, storage and consumption of electrical
energy based on advanced energy and ICT solutions and as such enables
e.g. following specific application areas: Smart transmission
systems, Demand Response/Load Management, Substation Automation,
Advanced Distribution Management, Advanced Metering Infrastructure
(AMI), Smart Metering, Smart Home and Building Automation,
E-mobility, etc.
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Smart Metering is a good example of a M2M application and can be
realized as one of the vertical applications in an M2M environment.
Different types of possibly wireless small meters produce all
together a huge amount of data, which is collected by a central
entity and processed by an application server. The M2M
infrastructure can be provided by a mobile network operator as the
meters in urban areas will have most likely a cellular or WiMAX
radio.
Smart Grid is built on a distributed and heterogeneous network and
can use a combination of diverse networking technologies, such as
wireless Access Technologies (WiMAX, Cellular, etc.), wireline and
Internet Technologies (e.g., IP/MPLS, Ethernet, SDH/PDH over Fiber
optic, etc.) as well as low-power radio technologies enabling the
networking of smart meters, home appliances, and constrained devices
(e.g. BT-LE, ZigBee, Z-Wave, Wi-Fi, etc.). The operational
effectiveness of the smart grid is highly dependent on a robust, two-
way, secure, and reliable communications network with suitable
availability.
The management of a distributed system like smart grid requires an
end-to-end management of and information exchange through different
type of networks. However, as of today there is no integrated smart
grid management approach and no common smart grid information model
available. Specific smart grid applications or network islands use
their own management mechanisms. For example, the management of
smart meters depends very much on the AMI environment they have been
integrated to and the networking technologies they are using. In
general, smart meters do only need seldom reconfiguration and they
send a small amount of redundant data to a central entity. For a
discussion on the management needs of an AMI network see
Section 3.11. The management needs for Smart Home and Building
Automation are discussed in Section 3.4 and Section 3.5.
3.7. Transport Applications
Transport Application is a generic term for the integrated
application of communications, control, and information processing in
a transportation system. Transport telematics or vehicle telematics
are used as a term for the group of technologies that support
transportation systems. Transport applications running on such a
transportation system cover all modes of the transport and consider
all elements of the transportation system, i.e. the vehicle, the
infrastructure, and the driver or user, interacting together
dynamically. The overall aim is to improve decision making, often in
real time, by transport network controllers and other users, thereby
improving the operation of the entire transport system. As such,
transport applications can be seen as one of the important M2M
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service scenarios with the involvement of manifold small devices.
The definition encompasses a broad array of techniques and approaches
that may be achieved through stand-alone technological applications
or as enhancements to other transportation communication schemes.
Examples for transport applications are inter and intra vehicular
communication, smart traffic control, smart parking, electronic toll
collection systems, logistic and fleet management, vehicle control,
and safety and road assistance.
As a distributed system, transport applications require an end-to-end
management of different types of networks. It is likely that
constrained devices in a network (e.g. a moving in-car network) have
to be controlled by an application running on an application server
in the network of a service provider. Such a highly distributed
network including mobile devices on vehicles is assumed to include a
wireless access network using diverse long distance wireless
technologies such as WiMAX, 3G/LTE or satellite communication, e.g.
based on an embedded hardware module. As a result, the management of
constrained devices in the transport system might be necessary to
plan top-down and might need to use data models obliged from and
defined on the application layer. The assumed device classes in use
are mainly C2 devices. In cases, where an in-vehicle network is
involved, C1 devices with limited capabilities and a short-distance
constrained radio network, e.g. IEEE 802.15.4 might be used
additionally.
Management responsibility typically rests within the organization
running the transport application. The constrained devices in a
moving transport network might be initially configured in a factory
and a reconfiguration might be needed only rarely. New devices might
be integrated in an ad-hoc manner based on self-management and
-configuration capabilities. Monitoring and data exchange might be
necessary to do via a gateway entity connected to the back-end
transport infrastructure. The devices and entities in the transport
infrastructure need to be monitored more frequently and can be able
to communicate with a higher data rate. The connectivity of such
entities does not necessarily need to be wireless. The time scale
for detecting and recording failures in a moving transport network is
likely measured in hours and repairs might easily take days. It is
likely that a self-healing feature would be used locally.
3.8. Infrastructure Monitoring
Infrastructure monitoring is concerned with the monitoring of
infrastructures such as bridges, railway tracks, or (offshore)
windmills. The primary goal is usually to detect any events or
changes of the structural conditions that can impact the risk and
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safety of the infrastructure being monitored. Another secondary goal
is to schedule repair and maintenance activities in a cost effective
manner.
The infrastructure to monitor might be in a factory or spread over a
wider area but difficult to access. As such, the network in use
might be based on a combination of fixed and wireless technologies,
which use robust networking equipment and support reliable
communication. It is likely that constrained devices in such a
network are mainly C2 devices and have to be controlled centrally by
an application running on a server. In case such a distributed
network is widely spread, the wireless devices might use diverse
long-distance wireless technologies such as WiMAX, or 3G/LTE, e.g.
based on embedded hardware modules. In cases, where an in-building
network is involved, the network can be based on Ethernet or wireless
technologies suitable for in-building usage.
The management of infrastructure monitoring applications is primarily
concerned with the monitoring of the functioning of the system.
Infrastructure monitoring devices are typically rolled out and
installed by dedicated experts and changes are rare since the
infrastructure itself changes rarely. However, monitoring devices
are often deployed in unsupervised environments and hence special
attention must be given to protecting the devices from being
modified.
Management responsibility typically rests with the organization
owning the infrastructure or responsible for its operation. The time
scale for detecting and recording failures is likely measured in
hours and repairs might easily take days. However, certain events
(e.g., natural disasters) may require that status information be
obtained much more quickly and that replacements of failed sensors
can be rolled out quickly (or redundant sensors are activated
quickly). In case the devices are difficult to access, a self-
healing feature on the device might become necessary.
3.9. Community Network Applications
Community networks are comprised of constrained routers in a multi-
hop mesh topology, communicating over a lossy, and often wireless
channel. While the routers are mostly non-mobile, the topology may
be very dynamic because of fluctuations in link quality of the
(wireless) channel caused by, e.g., obstacles, or other nearby radio
transmissions. Depending on the routers that are used in the
community network, the resources of the routers (memory, CPU) may be
more or less constrained - available resources may range from only a
few kilobytes of RAM to several megabytes or more, and CPUs may be
small and embedded, or more powerful general-purpose processors.
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Examples of such community networks are the FunkFeuer network
(Vienna, Austria), FreiFunk (Berlin, Germany), Seattle Wireless
(Seattle, USA), and AWMN (Athens, Greece). These community networks
are public and non-regulated, allowing their users to connect to each
other and - through an uplink to an ISP - to the Internet. No fee,
other than the initial purchase of a wireless router, is charged for
these services. Applications of these community networks can be
diverse, e.g., location based services, free Internet access, file
sharing between users, distributed chat services, social networking
etc, video sharing etc.
As an example of a community network, the FunkFeuer network comprises
several hundred routers, many of which have several radio interfaces
(with omnidirectional and some directed antennas). The routers of
the network are small-sized wireless routers, such as the Linksys
WRT54GL, available in 2011 for less than 50 Euros. These routers,
with 16 MB of RAM and 264 MHz of CPU power, are mounted on the
rooftops of the users. When new users want to connect to the
network, they acquire a wireless router, install the appropriate
firmware and routing protocol, and mount the router on the rooftop.
IP addresses for the router are assigned manually from a list of
addresses (because of the lack of autoconfiguration standards for
mesh networks in the IETF).
While the routers are non-mobile, fluctuations in link quality
require an ad hoc routing protocol that allows for quick convergence
to reflect the effective topology of the network (such as NHDP
[RFC6130] and OLSRv2 [I-D.ietf-manet-olsrv2] developed in the MANET
WG). Usually, no human interaction is required for these protocols,
as all variable parameters required by the routing protocol are
either negotiated in the control traffic exchange, or are only of
local importance to each router (i.e. do not influence
interoperability). However, external management and monitoring of an
ad hoc routing protocol may be desirable to optimize parameters of
the routing protocol. Such an optimization may lead to a more stable
perceived topology and to a lower control traffic overhead, and
therefore to a higher delivery success ratio of data packets, a lower
end-to-end delay, and less unnecessary bandwidth and energy usage.
Different use cases for the management of community networks are
possible:
o One single Network Management Station (NMS), e.g. a border gateway
providing connectivity to the Internet, requires managing or
monitoring routers in the community network, in order to
investigate problems (monitoring) or to improve performance by
changing parameters (managing). As the topology of the network is
dynamic, constant connectivity of each router towards the
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management station cannot be guaranteed. Current network
management protocols, such as SNMP and Netconf, may be used (e.g.,
using interfaces such as the NHDP-MIB [RFC6779]). However, when
routers in the community network are constrained, existing
protocols may require too many resources in terms of memory and
CPU; and more importantly, the bandwidth requirements may exceed
the available channel capacity in wireless mesh networks.
Moreover, management and monitoring may be unfeasible if the
connection between the NMS and the routers is frequently
interrupted.
o A distributed network monitoring, in which more than one
management station monitors or manages other routers. Because
connectivity to a server cannot be guaranteed at all times, a
distributed approach may provide a higher reliability, at the cost
of increased complexity. Currently, no IETF standard exists for
distributed monitoring and management.
o Monitoring and management of a whole network or a group of
routers. Monitoring the performance of a community network may
require more information than what can be acquired from a single
router using a network management protocol. Statistics, such as
topology changes over time, data throughput along certain routing
paths, congestion etc., are of interest for a group of routers (or
the routing domain) as a whole. As of 2012, no IETF standard
allows for monitoring or managing whole networks, instead of
single routers.
3.10. Mobile Applications
M2M services are increasingly provided by mobile service providers as
numerous devices, home appliances, utility meters, cars, video
surveillance cameras, and health monitors, are connected with mobile
broadband technologies. This diverse range of machines brings new
network and service requirements and challenges. Different
applications e.g. in a home appliance or in-car network use
Bluetooth, Wi-Fi or Zigbee and connect to a cellular module acting as
a gateway between the constrained environment and the mobile cellular
network.
Such a gateway might provide different options for the connectivity
of mobile networks and constrained devices, e.g.:
o a smart phone with 3G/4G and WLAN radio might use BT-LE to connect
to the devices in a home area network,
o a femtocell might be combined with home gateway functionality
acting as a low-power cellular base station connecting smart
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devices to the application server of a mobile service provider.
o an embedded cellular module with LTE radio connecting the devices
in the car network with the server running the telematics service,
o an M2M gateway connected to the mobile operator network supporting
diverse IoT connectivity technologies including ZigBee and CoAP
over 6LoWPAN over IEEE 802.15.4.
Common to all scenarios above is that they are embedded in a service
and connected to a network provided by a mobile service provider.
Usually there is a hierarchical deployment and management topology in
place where different parts of the network are managed by different
management entities and the count of devices to manage is high (e.g.
many thousands). In general, the network is comprised by manifold
type and size of devices matching to different device classes. As
such, the managing entity needs to be prepared to manage devices with
diverse capabilities using different communication or management
protocols. In case the devices are directly connected to a gateway
they most likely are managed by a management entity integrated with
the gateway, which itself is part of the Network Management System
(NMS) run by the mobile operator. Smart phones or embedded modules
connected to a gateway might be themselves in charge to manage the
devices on their level. The initial and subsequent configuration of
such a device is mainly based on self-configuration and is triggered
by the device itself.
The challenges in the management of devices in a mobile application
are manifold. Firstly, the issues caused through the device mobility
need to be taken into consideration. While the cellular devices are
moving around or roaming between different regional networks, they
should report their status to the corresponding management entities
with regard to their proximity and management hierarchy. Secondly, a
variety of device troubleshooting information needs to be reported to
the management system in order to provide accurate service to the
customer. Third but not least, the NMS and the used management
protocol need to be tailored to keep the cellular devices lightweight
and as energy efficient as possible.
The data models used in these scenario are mostly derived from the
models of the operator NMS and might be used to monitor the status of
the devices and to exchange the data sent by or read from the
devices. The gateway might be in charge of filtering and aggregating
the data received from the device as the information sent by the
device might be mostly redundant.
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3.11. Automated Metering Infrastructure (AMI)
An AMI network enables an electric utility to retrieve frequent
electric usage data from each electric meter installed at a
customer's home or business. With an AMI network, a utility can also
receive immediate notification of power outages when they occur,
directly from the electric meters that are experiencing those
outages. In addition, if the AMI network is designed to be open and
extensible, it could serve as the backbone for communicating with
other distribution automation devices besides meters, which could
include transformers and reclosers.
In this use case, each meter in the AMI network contains a
constrained device. These devices are typically C2 devices. Each
meter connects to a constrained mesh network with a low-bandwidth
radio. These radios can be 50, 150, or 200 kbps at raw link speed,
but actual network throughput may be significantly lower due to
forward error correction, multihop delays, MAC delays, lossy links,
and protocol overhead.
The constrained devices are used to connect the metering logic with
the network, so that usage data and outage notifications can be sent
back to the utility's headend systems over the network. These
headend systems are located in a data center managed by the utility,
and may include meter data collection systems, meter data management
systems, and outage management systems.
The meters are connected to a mesh network, and each meter can act as
both a source of traffic and as a router for other meters' traffic.
In a typical AMI application, smaller amounts of traffic (read
requests, configuration) flow "downstream" from the headend to the
mesh, and larger amounts of traffic flow "upstream" from the mesh to
the headend. However, during a firmware update operation, larger
amounts of traffic might flow downstream while smaller amounts flow
upstream. Other applications that make use of the AMI network may
have their own distinct traffic flows.
The mesh network is anchored by a collection of higher-end devices,
which contain a mesh radio that connects to the constrained network
as well as a backhaul link that connects to a less-constrained
network. The backhaul link could be cellular, WiMAX, or Ethernet,
depending on the backhaul networking technology that the utility has
chosen. These higher-end devices (termed "routers" in this use case)
are typically installed on utility poles throughout the service
territory. Router devices are typically less constrained than
meters, and often contain the full routing table for all the
endpoints routing through them.
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In this use case, the utility typically installs on the order of 1000
meters per router. The collection of meters comprised in a local
network that are routing through a specific router is called in this
use case a Local Meter Network (LMN). When powered on, each meter is
designed to discover the nearby LMNs, select the optimal LMN to join,
and select the optimal meters in that LMN to route through when
sending data to the headend. After joining the LMN, the meter is
designed to continuously monitor and optimize its connection to the
LMN, and it may change routes and LMNs as needed.
Each LMN may be configured e.g. to share an encryption key, providing
confidentiality for all data traffic within the LMN. This key may be
obtained by a meter only after an end-to-end authentication process
based on certificates, ensuring that only authorized and
authenticated meters are allowed to join the LMN, and by extension,
the mesh network as a whole.
After joining the LMN, each endpoint obtains a routable and possibly
private IPv6 address that enables end-to-end communication between
the headend systems and each meter. In this use case, the meters are
always-on. However, due to lossy links and network optimization, not
every meter will be immediately accessible, though eventually every
meter will be able to exchange data with the headend.
In a large AMI deployment, there may be 10 million meters supported
by 10.000 routers, spread across a very large geographic area.
Within a single LMN, the meters may range between 1 and approx. 20
hops from the router. During the deployment process, these meters
are installed and turned on in large batches, and those meters must
be authenticated, given addresses, and provisioned with any
configuration information necessary for their operation. During
deployment and after deployment is finished, the network must be
monitored continuously and failures must be handled. Configuration
parameters may need to be changed on large numbers of devices, but
most of the devices will be running the same configuration.
Moreover, eventually, the firmware in those meters will need to be
upgraded, and this must also be done in large batches because most of
the devices will be running the same firmware image.
Because there may be thousands of routers, this operational model
(batch deployment, automatic provisioning, continuous monitoring,
batch reconfiguration, batch firmware update) should also apply to
the routers as well as the constrained devices. The scale is
different (thousands instead of millions) but still large enough to
make individual management impractical for routers as well.
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3.12. MANET Concept of Operations (CONOPS) in Military
The use case on the Concept of Operations (CONOPS) focuses on the
configuration and monitoring of networks that are currently being
used in military and as such, it offers insights and challenges of
network management that military agencies are facing.
As technology advances, military networks nowadays become large and
consist of varieties of different types of equipments that run
different protocols and tools that obviously increase complexity of
the tactical networks. Moreover, lacks of open common interfaces and
Application Programming Interface (API) are often a challenge to
network management. Configurations are, most likely, manually
performed. Some devices do not support IP networks. Integration and
evaluation process are no longer trivial for a large set of protocols
and tools. In addition, majority of protocols and tools developed by
vendors that are being used are proprietary which makes integration
more difficult. The main reason that leads to this problem is that
there is no clearly defined standard for the MANET Concept of
Operations (CONOPS). In the following, a set of scenarios of network
operations are described, which might lead to the development of
network management protocols and a framework that can potentially be
used in military networks.
Note: The term "node" is used at IETF for either a host or router.
The term "unit" or "mobile unit" in military (e.g. Humvees, tanks)
is a unit that contains multiple routers, hosts, and/or other non-IP-
based communication devices.
Scenario: Parking Lot Staging Area:
The Parking Lot Staging Area is the most common network operation
that is currently widely used in military prior to deployment. MANET
routers, which can be identical such as the platoon leader's or
rifleman's radio, are shipped to a remote location along with a Fixed
Network Operations Center (NOC), where they are all connected over
traditional wired or wireless networks. The Fixed NOC then performs
mass-configuration and evaluation of configuration processes. The
same concept can be applied to mobile units. Once all units are
successfully configured, they are ready to be deployed.
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+---------+ +----------+
| Fixed |<---+------->| router_1 |
| NOC | | +----------+
+---------+ |
| +----------+
+------->| router_2 |
| +----------+
| 0
| 0
| 0
| +----------+
+------->| router_N |
+----------+
Figure 1: Parking Lot Staging Area
Scenario: Monitoring with SatCom Reachback:
The Monitoring with SatCom Reachback, which is considered another
possible common scenario to military's network operations, is similar
to the Parking Lot Staging Area. Instead, the Fixed NOC and MANET
routers are connected through a Satellite Communications (SatCom)
network. The Monitoring with SatCom Reachback is a scenario where
MANET routers are augmented with SatCom Reachback capabilities while
On-The-Move (OTM). Vehicles carrying MANET routers support multiple
types of wireless interfaces, including High Capacity Short Range
Radio interfaces as well as Low Capacity OTM SatCom interfaces. The
radio interfaces are the preferred interfaces for carrying data
traffic due to their high capacity, but the range is limiting with
respect to connectivity to a Fixed NOC. Hence, OTM SatCom interfaces
offer a more persistent but lower capacity reachback capability. The
existence of a SatCom persistent Reachback capability offers the NOC
the ability to monitor and manage the MANET routers over the air.
Similarly to the Parking Lot Staging scenario, the same concept can
be applied to mobile units.
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--- +--+ ---
/ /---|SC|---/ /
--- +--+ ---
+---------+ |
| Fixed |<---------------------+
| NOC | +--------------|
+---------+ | +-------------------+
| | |
+----------+ | +----------+
| router_1 | +----------+ | router_N |
+----------+ | | +----------+
* | | * *
* +----------+ | * *
*********| router_2 |*****|******* *
+----------+ | *
* | *
* +----------+ *
********| router_3 |****
+----------+
--- SatCom links
*** Radio links
Figure 2: Monitoring with one-hop SatCom Reachback network
Scenario: Hierarchical Management:
Another reasonable scenario common to military operations in a MANET
environment is the Hierarchical Management scenario. Vehicles carry
a rather complex set of networking devices, including routers running
MANET control protocols. In this hierarchical architecture, the
MANET mobile unit has a rather complex internal architecture where a
local manager within the unit is responsible for local management.
The local management includes management of the MANET router and
control protocols, the firewall, servers, proxies, hosts and
applications. In addition, a standard management interface is
required in this architecture. Moreover, in addition to requiring
standard management interfaces into the components comprising the
MANET nodal architecture, the local manager is responsible for local
monitoring and the generation of periodic reports back to the Fixed
NOC.
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Interface
|
V
+---------+ +-------------------------+
| Fixed | Interface | +---+ +---+ |
| NOC |<---+------->| | R |--+--| F | |
+---------+ | | +---+ | +---+ |
| | | | +---+ |
| | +---+ | +--| P | |
| | | M |--+ | +---+ |
| | +---+ | |
| | | +---+ |
| | +--| D | |
| | | +---+ |
| | | |
| | | +---+ |
| | +--| H | |
| | | +---+ |
| | unit_1 |
| +-------------------------+
|
|
| +--------+
+------->| unit_2 |
| +--------+
| 0
| 0
| 0
| +--------+
+------->| unit_N |
+--------+
Key: R-Router
F-Firewall
P-PEP (Performance Enhancing Proxy)
D-Servers, e.g., DNS
H-hosts
M-Local Manager
Figure 3: Hierarchical Management
Scenario: Management over Lossy/Intermittent Links:
In the future of military operations, the standard management will be
done over lossy and intermittent links and ideally the Fixed NOC will
become mobile. In this architecture, the nature and current quality
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of each link are distinct. However, there are a number of issues
that would arise and need to be addressed:
1. Common and specific configurations are undefined:
A. When mass-configuring devices, common set of configurations
are undefined at this time.
B. Similarly, when performing a specific device, set of specific
configurations is unknown.
2. Once the total number of units becomes quite large, scalability
would be an issue and need to be addressed.
3. The state of the devices are different and may be in various
states of operations, e.g., ON/OFF, etc.
4. Pushing large data files over reliable transport, e.g., TCP,
would be problematic. Would a new mechanism of transmitting
large configurations over the air in low bandwidth be
implemented? Which protocol would be used at transport layer?
5. How to validate network configuration (and local configuration)
is complex, even when to cutover is an interesting question.
6. Security as a general issue needs to be addressed as it could be
problematic in military operations.
+---------+ +----------+
| Mobile |<----------->| router_1 |
| NOC |?--+ +----------+
+---------+ |
^ | +----------+
| +------->| router_2 |
| +----------+
| 0
| 0
| 0
| +----------+
+---------------->| router_N |
+----------+
Figure 4: Management over Lossy/intermittent Links
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4. Requirements on the Management of Networks with Constrained Devices
This section describes the requirements categorized by management
areas listed in subsections.
Note that the requirements in this section need to be seen as
standalone requirements. A device might be able to provide selected
requirements but might not be capable to provide all requirements at
once. On the other hand a device vendor might select a subset of the
requirements to implement. As of today this document does not
recommend the realization of a profile of requirements.
Following template is used for the definition of the requirements.
Req-ID: An ID uniquely identified by a three-digit number
Title: The title of the requirement.
Description: The rational and description of the requirement.
Source: The origin of the requirement and the matching use case or
application.
Requirement Type: Functional Requirement, Non-Functional
Requirement, Design Constraint
Device type: The device types by which this requirement can be
supported: C0, C1 and/or C2.
Priority: The priority of the requirement showing the importance:
Mandatory (M), Optional (O), Conditional (C).
4.1. Management Architecture/System
Req-ID: 4.1.001
Title: Support multiple device classes within a single network.
Description: Larger networks usually are made up of devices
belonging to different device classes (e.g., constrained mesh
endpoints and less constrained routers) that work together.
Hence, the management architecture must be applicable to networks
that have a mix of different device classes. See Section 3. of
[LWIG-TERMS] for the definition of Constrained Device Classes.
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Source: All use cases.
Requirement Type: Non-Functional Requirement
Device type: Managing and intermediary entities.
Priority: Mandatory
---
Req-ID: 4.1.002
Title: Management scalability.
Description: The management architecture must be able to scale with
the number of devices involved and operate efficiently in any
network size and topology. This implies that e.g. the managing
entity is able to handle huge amount of device monitoring data and
the management protocol is not sensitive to the decrease of the
time between two client requests. To achieve good scalability,
caching techniques, in-network data aggregation techniques,
hierarchical management models may be used.
Source: General requirement for all use cases to enable large scale
networks.
Requirement Type: Design Constraint
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.1.003
Title: Hierarchical management
Description: Provide a means of hierarchical management, i.e.
provide intermediary management entities on different levels,
which can take over the responsibility for the management of a
sub-hierarchy of the network of constraint devices. The
intermediary management entity can e.g. support management data
aggregation to handle e.g. high-frequent monitoring data or
provide a caching mechanism for the uplink and downlink
communication. Hierarchical management contributes to management
scalability.
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Source: Use cases where a huge amount of devices are deployed with a
hierarchical topology.
Requirement Type: Non-Functional Requirement
Device type: Managing and intermediary entities.
Priority: Optional
---
Req-ID: 4.1.004
Title: Minimize state maintained on constrained devices.
Description: The amount of state that needs to be maintained on
constrained devices should be minimized. This is important in
order to save memory (especially relevant for C0 and C1 devices)
and in order to allow devices to restart for example to apply
configuration changes or to recover from extended periods of
inactivity. One way to achieve this is to adopt a RESTful
architecture that minimizes the amount of state maintained by
managed constrained devices and that makes resources of a device
addressable via URIs.
Source: Basic requirement which concerns all use cases.
Requirement Type: Non-Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.1.005
Title: Automatic re-synchronization with eventual consistency.
Description: To support large scale networks, where some constrained
devices may be offline at any point in time, it is necessary to
distribute configuration parameters in a way that allows temporary
inconsistencies but eventually converges, after a sufficiently
long period of time without further changes, towards global
consistency.
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Source: Use cases with large scale networks with many devices.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.1.006
Title: Support for lossy links and unreachable devices.
Description: Some constrained devices will only be able to support
lossy and unreliable links characterized by a limited data rate, a
high latency, and a high transmission error rate. Furthermore
constrained devices often duty cycle their radio or the whole
device in order to save energy. In both cases the management
system must not assume that constrained devices are always
reachable. The management protocol(s) must act gracefully if a
conctrained device is not reachable and provide a high degree of
resilience. Intermediaries may be used that provide information
for devices currently inactive or that take responsibility to re-
synchronize devices when they become reachable again after an
extended offline period.
Source: Basic requirement for constrained networks with unreliable
links and constrained devices which sleep to save energy.
Requirement Type: Design Constraint
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.1.007
Title: Network-wide configuration
Description: Provide means by which the behavior of the network can
be specified at a level of abstraction (network-wide
configuration) higher than a set of configuration information
specific to individual devices. It is useful to derive the device
specific configuration from the network-wide configuration. The
identification of the relevant subset of the policies to be
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provisioned is according to the capabilities of each device and
can be obtained from a pre-configured data-repository. Such a
repository can be used to configure pre-defined device or protocol
parameters for the whole network. Furthermore, such a network-
wide view can be used to monitor and manage a group of routers or
a whole network. E.g. monitoring the performance of a network
requires additional information other than what can be acquired
from a single router using a management protocol.
Source: In general all use cases, which want to configure the
network and its devices based on a network view in a top-down
manner.
Requirement Type: Non-Functional Requirement
Device type: C0, C1, and C2
Priority: Optional
---
Req-ID: 4.1.008
Title: Distributed Management
Description: Provide a means of simple distributed management, where
a constrained network can be managed or monitored by more than one
manager. Since the connectivity to a server cannot be guaranteed
at all times, a distributed approach may provide a higher
reliability, at the cost of increased complexity. This
requirement implies the handling of data consistency in case of
concurrent read and write access to the device datastore. It
might also happen that no management (configuration) server is
accessible and the only reachable node is a peer device. In this
case the device should be able to obtain its configuration from
peer devices.
Source: Use cases where the count of devices to manage is high.
Requirement Type: Non-Functional Requirement
Device type: C1 and C2
Priority: Optional
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4.2. Management protocols and data model
Req-ID: 4.2.001
Title: Modular implementation of management protocols
Description: Management protocols should allow modular
implementations, i.e., it should be possible to implement only a
basic set of protocol primitives on highly constrained devices
while devices with additional resources may provide more support
for additional protocol primitives. It should be possible to
discover the management protocol primitives by a device.
Source: Basic requirement interesting for all use cases.
Requirement Type: Non-Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.2.002
Title: Compact encoding of management data
Description: The encoding of management data should be compact and
space efficient, enabling small message sizes.
Source: General requirement to save memory for the receiver buffer
and on-air bandwith.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.2.003
Title: Compression of management data or complete messages
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Description: Management data exchanges can be further optimized by
applying data compression techniques or delta encoding techniques.
Compression typically requires additional code size and some
additional buffers and/or the maintenance of some additional state
information. For C0 devices compression may not be feasible. As
such, this requirement is marked as optional.
Source: Use cases where it is beneficial to reduce transmission time
and bandwith, e.g. mobile applications which require to save on-
air bandwith.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
---
Req-ID: 4.2.004
Title: Mapping of management protocol interactions.
Description: It is desirable to have a loss-less automated mapping
between the management protocol used to manage constrained devices
and the management protocols used to manage regular devices. In
the ideal case, the same core management protocol can be used with
certain restrictions taking into account the resource limitations
of constrained devices. However, for very resource constrained
devices, this goal might not be achievable. Hence this
requirement is marked optional for device class C2.
Source: Use cases where high-frequent interaction with the
management system of a non-constrained network is required.
Requirement Type: Functional Requirement
Device type: C2
Priority: Optional
---
Req-ID: 4.2.005
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Title: Consistency of data models with the underlying information
model.
Description: The data models used by the management protocol must be
consistent with the information model used to define data models
for non-constrained networks. This is essential to facilitate the
integration of the management of constrained networks with the
management of non-constrained networks. Using an underlying
information model for future data model design enables furthermore
top-down model design and model reuse as well as data
interoperability (i.e. exchange of management information between
the constrained and non-constrained networks). This is a strong
requirement, even despite the fact that the underlying information
models are often not explicitly documented in the IETF.
Source: General requirement to support data interoperability,
consistency and model reuse.
Requirement Type: Non-Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.2.006
Title: Loss-less mapping of management data models.
Description: It is desirable to have a loss-less automated mapping
between the management data models used to manage regular devices
and the management data models used for managing constrained
devices. In the ideal case, the same core data models can be used
with certain restrictions taking into account the resource
limitations of constrained devices. However, for very resource
constrained devices, this goal might not be achievable. Hence
this requirement is marked optional for device class C2.
Source: Use cases where consistent data exchange with the management
system of a non-constrained network is required.
Requirement Type: Functional Requirement
Device type: C2
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Priority: Optional
---
Req-ID: 4.2.007
Title: Protocol extensibility
Description: Provide means of extensibility for the management
protocol, i.e. by adding new protocol messages or mechanisms that
can deal with the changing requirements on a supported message and
data types effectively, without causing inter-operability problems
or having to replace/update large amounts of deployed devices.
Source: Basic requirement useful for all use cases.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
4.3. Configuration management
Req-ID: 4.3.001
Title: Self-configuration capability
Description: Automatic configuration and re-configuration of devices
without manual intervention. Compared to the traditional
management of devices where the management application is the
central entity configuring the devices, in the auto-configuration
scenario the device is the active part and initiates the
configuration process. Self-configuration can be initiated during
the initial configuration or for subsequent configurations, where
the configuration data needs to be refreshed. Self-configuration
should be also supported during the initialization phase or in the
event of failures, where prior knowledge of the network topology
is not available or the topology of the network is uncertain.
Source: In general all use cases requiring easy deployment and plug&
play behavior as well as easy maintenance of many constrained
devices.
Requirement Type: Functional Requirement
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Device type: C0, C1, and C2
Priority: Mandatory for C0 and C1, Optional for C2.
---
Req-ID: 4.3.002
Title: Capability Discovery
Description: Enable the discovery of supported optional management
capabilities of a device and their exposure via at least one
protocol and/or data model.
Source: Use cases where the device interaction with other devices or
applications is a function of the level of support for its
capabilities.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
---
Req-ID: 4.3.003
Title: Asynchronous Transaction Support
Description: Provide configuration management with asynchronous
transaction support. Configuration operations must support a
transactional model, with asynchronous indications that the
transaction was completed.
Source: Use cases, which require transaction-oriented processing
because of reliability or distributed architecture functional
requirements.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Conditional
---
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Req-ID: 4.3.004
Title: Network reconfiguration
Description: Provide a means of iterative network reconfiguration in
order to recover the network functionality from node and
communication faults. The network reconfiguration can be failure-
driven and self-initiated (automatic reconfiguration). The
network reconfiguration can be also performed on the whole
hierarchical structure of a network (network topology).
Source: Practically all use cases, as network connectivity is a
basic requirement.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory, Conditional if the network has a hierarchical
topology.
4.4. Monitoring functionality
Req-ID: 4.4.001
Title: Device status monitoring
Description: Provide a monitoring function to collect and expose
information about device status and exposing it via at least one
management interface. The device monitoring might make use of the
hierarchical management through the intermediary entities and the
data caching mechanism. The device monitoring might also make use
of neighbor-monitoring (fault detection in local network) to
support fast fault detection and recovery, e.g. in a scenario
where a managing entity is unreachable and a neighbor can take
over the monitoring responsibility.
Source: All use cases
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory, Conditional for neighbor-monitoring.
---
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Req-ID: 4.4.002
Title: Energy status monitoring
Description: Provide a monitoring function to collect and expose
information about device energy parameters and usage (e.g. battery
level and communication power).
Source: Use case Energy Management
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory for energy reporting devices, Optional for the
rest
---
Req-ID: 4.4.003
Title: Monitoring of current and estimated device availability
Description: Provide a monitoring function to collect and expose
information about current device availability (energy, memory,
computing power, forwarding plane utilization, queue buffers,
etc.) and estimation of remaining available resources.
Source: All use cases. Note that monitoring energy resources (like
battery status) may be required on all kinds of devices.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Optional
---
Req-ID: 4.4.004
Title: Network status monitoring
Description: Provide a monitoring function to collect and expose
information related to the status of a network or network segments
connected to the interfaces of the device.
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Source: All use cases.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
---
Req-ID: 4.4.005
Title: Self-monitoring
Description: Provide self-monitoring (local fault detection) feature
for fast fault detection and recovery.
Source: Use cases where the devices cannot be monitored centrally in
appropriate manner, e.g. self-healing is required.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Mandatory for C2, Optional for C1
---
Req-ID: 4.4.006
Title: Performance Monitoring
Description: The device will provide a monitoring function to
collect and expose information about the basic TBD performance of
the device. The performance management functionality might make
use of the hierarchical management through the intermediary
devices.
Source: Use cases Building automation, and Transport applications
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
---
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Req-ID: 4.4.007
Title: Fault detection monitoring
Description: The device will provide fault detection monitoring.
The system collects information about network states in order to
identify whether faults have occurred. In some cases the
detection of the faults might be based on the processing and
analysis of the parameters retrieved from the network or other
devices. In case of C0 devices the monitoring might be limited to
the check whether the device is alive or not.
Source: Use cases Environmental Monitoring, Building Automation,
Energy Management, Infrastructure Monitoring
Requirement Type: Functional Requirement
Device type: C0, C1 and C2
Priority: Optional
---
Req-ID: 4.4.008
Title: Passive and Reactive Monitoring
Description: The device will provide passive and reactive monitoring
capabilities. The system or manager collects information about
device components and network states (passive monitoring) and may
perform postmortem analysis of collected data. In case events of
interest have occurred the system or manager can adaptively react
(reactive monitoring), e.g. reconfigure the network. Typically
actions (re-actions) will be executed or sent as commands by the
management applications.
Source: Diverse use cases relevant for device status and network
state monitoring
Requirement Type: Functional Requirement
Device type: C2
Priority: Optional
---
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Req-ID: 4.4.009
Title: Recovery
Description: Provide local, central and hierarchical recovery
mechanisms (recovery is in some cases achieved by recovering the
whole network of constrained devices).
Source: Use cases Industrial applications, Home and Building
Automation, Mobile Applications that involve different forms of
clustering or area managers.
Requirement Type: Functional Requirement
Device type: C2
Priority: Optional
---
Req-ID: 4.4.010
Title: Network topology discovery
Description: Provide a network topology discovery capability (e.g.
use of topology extraction algorithms to retrieve the network
state) and a monitoring function to collect and expose information
about the network topology.
Source: Use cases Community Network Applications and Mobile
Applications
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
---
Req-ID: 4.4.011
Title: Notifications
Description: The device will provide the capability of sending
notifications on critical events and faults.
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Source: All use cases.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory for C2, Optional for C1
---
Req-ID: 4.4.012
Title: Logging
Description: The device will provide the capability of building,
keeping, and allowing retrieval of logs of events (including but
not limited to critical faults and alarms).
Source: Use cases Industrial Applications, Building Automation,
Infrastructure monitoring
Requirement Type: Functional Requirement
Device type: C2
Priority: Mandatory for some medical or industrial applications,
Optional otherwise
4.5. Self-management
Req-ID: 4.5.001
Title: Self-management - Self-healing
Description: Enable event-driven and/or periodic self-management
functionality in a device. The device should be able to react in
case of a failure e.g. by initiating a fully or partly reset and
initiate a self-configuration or management data update as
necessary. A device might be further able to check for failures
cyclically or schedule-controlled to trigger self-management as
necessary. It is a matter of device design and subject for
discussion how much self-management a C1 device can support. A
minimal failure detection and self-management logic is assumed to
be generally useful for the self-healing of a device.
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Source: The requirement generally relates to all use cases in this
document.
Requirement Type: Functional Requirement
Device type: C1 and C2
Priority: Optional
4.6. Security and Access Control
Req-ID: 4.6.001
Title: Authentication of management system and devices.
Description: Systems having a management role must be properly
authenticated to the device such that the device can exercise
proper access control and in particular distinguish rightful
management systems from rogue systems. On the other hand managed
devices must authenticate themselves to systems having a
management role such that management systems can protect
themselves from rogue devices. In certain application scenarios,
it is possible that a large number of devices need to be
(re)started at about the same time. Protocols and authentication
systems should be designed such that a large number of devices
(re)starting simultaneously does not negatively impact the device
authentication process.
Source: Basic security requirement for all use cases.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory, Optional for the (re)start of a large number of
devices
---
Req-ID: 4.6.002
Title: Support suitable security bootstrapping mechanisms
Description: Mechanisms should be supported that simplify the
bootstrapping of device that is the discovery of newly deployed
devices in order to add them to access control lists.
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Source: Basic security requirement for all use cases.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.6.003
Title: Access control on management system and devices
Description: Systems acting in a management role must provide an
access control mechanism that allows the security administrator to
restrict which devices can access the managing system (e.g., using
an access control white list of known devices). On the other hand
managed constrained devices must provide an access control
mechanism that allows the security administrator to restrict how
systems in a management role can access the device (e.g., no-
access, read-only access, and read-write access).
Source: Basic security requirement for use cases where access
control is essential.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.6.004
Title: Select cryptographic algorithms that are efficient in both
code space and execution time.
Description: Cryptographic algorithms have a major impact in terms
of both code size and overall execution time. It is therefore
necessary to select mandatory to implement cryptographic
algorithms (like some elliptic curve algorithm) that are
reasonable to implement with the available code space and that
have a small impact at runtime. Furthermore some wireless
technologies (e.g., IEEE 802.15.4) require the support of certain
cryptographic algorithms. It might be useful to choose algorithms
that are likely to be supported in wireless chipsets for certain
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wireless technologies.
Source: Generic requirement to reduce the footprint and CPU usage of
a constrained device.
Requirement Type: Non-Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory, Optional for hardware-supported algorithms.
4.7. Energy Management
Req-ID: 4.7.001
Title: Management of Energy Resources
Description: Enable managing power resources in the network, e.g.
reduce the sampling rate of nodes with critical battery and reduce
node transmission power, put nodes to sleep, put single interfaces
to sleep, reject a management job based on available energy,
criteria e.g. importance levels pre-defined by the management
application, etc. (e.g. a task marked as essential can be executed
even if the energy level is low). The device may further
implement standard data models for energy management and expose it
through a management protocol interface, e.g. EMAN MIB modules
and extensions. It might be necessary to downscale EMAN MIBs for
the use in C1 and C2 devices.
Source: Use case Energy Management
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory for the use case Energy Management, Optional
otherwise.
---
Req-ID: 4.7.002
Title: Support of energy-optimized communication protocols
Description: Use of an optimized communication protocol to minimize
energy usage for the device (radio) receiver/transmitter, on-air
bandwidth (protocol efficiency), reduced amount of data
communication between nodes (implies data aggregation and
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filtering but also a compact format for the transferred data).
Source: Use cases Energy Management and Mobile Applications.
Requirement Type: Functional Requirement
Device type: C2
Priority: Optional
---
Req-ID: 4.7.003
Title: Support for layer 2 energy-aware protocols
Description: The device will support layer 2 energy management
protocols (e.g. energy-efficient Ethernet IEEE 802.3az) and be
able to report on these.
Source: Use case Energy Management
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Optional
---
Req-ID: 4.7.004
Title: Dying gasp
Description: When energy resources draw below the red line level,
the device will send a dying gasp notification and perform if
still possible a graceful shutdown including conservation of
critical device configuration and status information.
Source: Use case Energy Management
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
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Priority: Optional
4.8. SW Distribution
Req-ID: 4.8.001
Title: Group-based provisioning
Description: Support group-based provisioning, i.e. firmware update
and configuration management, of a large set of constrained
devices with eventual consistency and coordinated reload times.
The device should accept group-based configuration management
based on bulk commands, which aim similar configurations of a
large set of constrained devices of the same type in a given
group. Activation of configuration may be based on pre-loaded
sets of default values.
Source: All use cases
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Optional
4.9. Traffic management
Req-ID: 4.9.001
Title: Congestion avoidance
Description: Provide the ability to avoid congestion by modifying
the device's reporting rate for periodical data (which is usually
redundant) based on the importance and reliability level of the
management data. This functionality is usually controlled by the
managing entity, where the managing entity marks the data as
important or relevant for reliability. However reducing a
device's reporting rate can also be initiated by a device if it is
able to detect congestion or has insufficient buffer memory.
Source: Use cases with high reporting rate and traffic e.g. AMI or
M2M.
Requirement Type: Design Constraint
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Device type: C1 and C2
Priority: Optional
---
Req-ID: 4.9.002
Title: Redirect traffic
Description: Provide the ability for network nodes to redirect
traffic from overloaded intermediary nodes in a network to another
path in order to prevent congestion on a central server and in the
primary network.
Source: Use cases with high reporting rate and traffic e.g. AMI or
M2M.
Requirement Type: Design Constraint
Device type: Intermediary entity in the network.
Priority: Optional
---
Req-ID: 4.9.003
Title: Traffic delay schemes.
Description: Provide the ability to apply delay schemes to incoming
and outgoing links on an overloaded intermediary node as necessary
in order to reduce the amount of traffic in the network.
Source: Use cases with high reporting rate and traffic e.g. AMI or
M2M.
Requirement Type: Design Constraint
Device type: Intermediary entity in the network.
Priority: Optional
4.10. Transport Layer
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Req-ID: 4.10.001
Title: Scalable transport layer
Description: Enable the use of a scalable transport layer, i.e. not
sensitive to the decrease of the time between two client requests,
which is useful for applications requiring frequent access to
device data.
Source: Applications with high frequent access to the device data.
Requirement Type: Design Constraint
Device type: C0, C1 and C2
Priority: Conditional, in case such scalability is a prerequisite.
---
Req-ID: 4.10.002
Title: Reliable unicast transport.
Description: Provide reliable unicast transport of messages.
Source: Generally all applications benefit from the reliability of
the message transport.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Mandatory
---
Req-ID: 4.10.003
Title: Best-effort multicast
Description: Provide best-effort multicast of messages, which is
generally useful when devices need to discover a service provided
by a server or many devices need to be configured by a managing
entity at once based on the same data model.
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Source: Use cases where a device needs to discover services as well
as use cases with high amount of devices to manage, which are
hierarchically deployed, e.g. AMI or M2M.
Requirement Type: Functional Requirement
Device type: C0, C1, and C2
Priority: Optional
Req-ID: 4.10.004
Title: Secure message transport.
Description: Enable secure message transport providing
authentication, data integrity, confidentiality by using existing
transport layer technologies with small footprint such as TLS/
DTLS.
Source: All use cases.
Requirement Type: Non-Functional Requirements
Device type: C1 and C2
Priority: Mandatory
4.11. Implementation Requirements
Req-ID: 4.11.001
Title: Avoid complex application layer transactions requiring large
application layer messages.
Description: Complex application layer transactions tend to require
large memory buffers that are typically not available on C0 or C1
devices and only by limiting functionality on C2 devices.
Furthermore, the failure of a single large transaction requires
repeating the whole transaction. On constrained devices, it is
often more desirable to a large transaction down into a sequence
of smaller transactions, which require less resources and allow to
make progress using a sequence of smaller steps.
Source: Basic requirement which concerns all use cases with memory
constrained devices.
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Requirement Type: Design Constraint
Device type: C0, C1, and C2
Priority: Mandatory
Req-ID: 4.11.002
Title: Avoid reassembly of messages at multiple layers in the
protocol stack.
Description: Reassembly of messages at multiple layers in the
protocol stack requires buffers at multiple layers, which leads to
inefficient use of memory resources. This can be avoided by
making sure the application layer, the security layer, the
transport layer, the IPv6 layer and any adaptation layers are
aware of the limitations of each other such that unnecessary
fragmentation and reassembly can be avoided. In addition, message
size constraints must be announced to protocol peers such that
they can adapt and avoid sending messages that can't be processed
due to resource constraints on the receiving device.
Source: Basic requirement which concerns all use cases with memory
constrained devices.
Requirement Type: Design Constraint
Device type: C0, C1, and C2
Priority: Mandatory
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5. IANA Considerations
This document does not introduce any new code-points or namespaces
for registration with IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
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6. Security Considerations
This document discusses the use cases and requirements on the network
of constrained devices. If specific requirements for security will
be identified, they will be described in future versions of this
document.
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7. Contributors
Following persons made significant contributions to and reviewed this
document:
o Ulrich Herberg (Fujitsu Laboratories of America) contributed the
Section 3.9 on Community Network Applications and to the
Section 1.3 on Class of Networks in Focus.
o Peter van der Stok contributed to Section 3.5 on Building
Automation.
o Zhen Cao contributed to Section 3.10 on Mobile Applications.
o Gilman Tolle contributed the Section 3.11 on Automated Metering
Infrastructure.
o James Nguyen and Ulrich Herberg contributed the Section 3.12 on
MANET Concept of Operations (CONOPS) in Military.
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8. Acknowledgments
The editors would like to thank the contributors and the participants
on the Coman maillist for their valuable contributions and comments.
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[RFC6632] Ersue, M. and B. Claise, "An Overview of the IETF Network
Management Standards", RFC 6632, June 2012.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, April 2011.
[RFC6779] Herberg, U., Cole, R., and I. Chakeres, "Definition of
Managed Objects for the Neighborhood Discovery Protocol",
RFC 6779, October 2012.
[I-D.ietf-manet-olsrv2]
Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol version 2",
draft-ietf-manet-olsrv2-17 (work in progress),
October 2012.
[I-D.ietf-lwig-guidance]
Bormann, C., "Guidance for Light-Weight Implementations of
the Internet Protocol Suite", draft-ietf-lwig-guidance-02
(work in progress), August 2012.
[I-D.ietf-core-coap]
Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
"Constrained Application Protocol (CoAP)",
draft-ietf-core-coap-13 (work in progress), December 2012.
[I-D.ietf-eman-framework]
Claise, B., Parello, J., Schoening, B., Quittek, J., and
B. Nordman, "Energy Management Framework",
draft-ietf-eman-framework-06 (work in progress),
October 2012.
[I-D.ietf-eman-requirements]
Quittek, J., Chandramouli, M., Winter, R., Dietz, T., and
B. Claise, "Requirements for Energy Management",
draft-ietf-eman-requirements-11 (work in progress),
January 2013.
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[I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-10 (work in
progress), January 2013.
[M2MDEVCLASS]
Open Mobile Alliance, "OMA M2M Device Classification
v1.0", October 2012, <http://
technical.openmobilealliance.org/Technical/
release_program/m2m_Device_class_v1_0.aspx>.
[EU-IOT-A]
EU Commission Seventh Framework Programme, "EU FP7 Project
Internet-of-Things Architecture", <http://www.iot-a.eu/>.
[EU-SENSEI]
EU Commission Seventh Framework Programme, "EU Project
SENSEI", <http://www.sensei-project.eu/>.
[EU-FI-WARE]
EU Commission Future Internet Public Private Partnership
(FI-PPP), "EU Project Future Internet-Core Platform",
<http://www.iot-butler.eu/>.
[EU-IOT-BUTLER]
EU Commission Seventh Framework Programme, "EU FP7 Project
Butler Smartlife", <http://www.iot-butler.eu/>.
[LWIG-TERMS]
Bormann, C., "Terminology for Constrained Node Networks",
draft-bormann-lwig-terms (work in progress),
November 2012.
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Appendix A. Related Development in other Bodies
Note that over time the summary on the related work in other bodies
might become outdated.
A.1. ETSI TC M2M
ETSI Technical Committee Machine-to-Machine (ETSI TC M2M) aims to
provide an end-to-end view of M2M standardization, which enables the
integration of multiple vertical M2M applications. The main goal is
to overcome the current M2M market fragmentation and to reuse
existing mechanisms from telecom standards such as from OMA or 3GPP.
ETSI Release 1 is functionally frozen. The main focus is on use
cases for Smart Metering (Technical Report (TR) 102 691) but it also
includes eHealth use cases (TR 102 732) and some others. The Service
requirements (Technical Standard (TS) 102 689) derived from the use
cases, and the functional architecture specification (TS 102 690),
will together define the M2M platform. The architecture consists of
Service Capabilities (SC), which are basic functional building blocks
for building the M2M platform.
Smart Metering is seen as the important showcase for M2M. It is
believed that the Service Enablers that were defined based on the
work done for Smart Metering and eHealth segments will also allow the
building of other services like vending machines, alarm systems etc.
The functional architecture includes following management-related
definitions:
o Network Management Functions: consists of all functions required
to manage the Access, Transport and Core networks: these include
Provisioning, Supervision, Fault Management, etc.
o M2M Management Functions: consists of functions required to manage
generic functionalities of M2M Applications and M2M Service
Capabilities in the Network and Applications Domain. The
management of the M2M Devices and Gateways may use specific M2M
Service Capabilities.
The Release 2 work of ETSI TC M2M has started beginning of 2012.
Following is a list of networking- and management-related topics
under work:
o Interworking with 3GPP networks. This is a new work item, and no
discussion has been held on technical details. The intent is to
define which ETSI TC M2M functions are applicable when 3GPP NW is
used as transport. It is possible that this work would also cover
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details on how to use 3GPP interfaces, e.g. those defined in the
SIMTC work, but also for charging and policy control.
o Creating a Semantic Model or Data Abstraction layer for vertical
industries and interworking. This would provide some high level
information description that would be usable for interworking with
local networks (e.g. ZigBee), and also for verticals, and it
would allow the ETSI Service Enablement layer to also understand
the data, instead of being just a bit storage and bit pipe. All
technical details are still under discussion, but it has been
agreed that a function for this exists in the architecture at
least for interworking.
A.2. OASIS
Developments in OASIS related to management of constrained networks
are following:
o The Energy Interoperation TC works to define interaction between
Smart Grids and their end nodes, including Smart Buildings,
Enterprises, Industry, Homes, and Vehicles. The TC develops data
and communication models that enable the interoperable and
standard exchange of signals for dynamic pricing, reliability, and
emergencies. The TC's agenda also extends to the communication of
market participation data (such as bids), load predictability, and
generation information. The first version of the Energy
Interoperation specification is in final review.
o OASIS Open Data Protocol (OData) aims to simplify the querying and
sharing of data across disparate applications and multiple
stakeholders for re-use in the enterprise, Cloud, and mobile
devices. As a REST-based protocol, OData builds on HTTP, AtomPub,
and JSON using URIs to address and access data feed resources. It
enables information to be accessed from a variety of sources
including (but not limited to) relational databases, file systems,
content management systems, and traditional Web sites.
o Open Building Information Exchange (oBIX) aims to enable the
mechanical and electrical control systems in buildings to
communicate with enterprise applications, and to provide a
platform for developing new classes of applications that integrate
control systems with other enterprise functions. Enterprise
functions include processes such as Human Resources, Finance,
Customer Relationship Management (CRM), and Manufacturing.
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A.3. OMA
OMA is currently working on Lightweight M2M Enabler, OMA Device
Management (OMA DM) Next Generation, and a white paper on M2M Device
Classification.
The Lightweight M2M Enabler covers both M2M device management and
service management for constrained devices. In the case of less
constrained devices, OMA DM Next Generation Enabler may be more
appropriate. OMA DM is structured around Management Objects (MO),
each specified for a specific purpose. There is also ongoing work
with various other MOs such as the Gateway Management Object (GwMO).
A draft for the "Lightweight M2M Requirements" is available.
OMA Lightweight M2M and OMA DM Next Generation are important to M2M
device management, provisioning and service managements in both the
protocol and management objects. OMA Lightweight M2M work seems to
have grown from its original scope of being targeted for very simple
devices only, i.e. such that could not handle all those protocols
that ETSI M2M requires.
The white paper on the M2M Device Classification [M2MDEVCLASS]
provides an M2M device classification framework based on the
horizontal attributes (e.g., wide or local area communication
interface, IP stack, I/O capabilities) of interest to communication
service providers and M2M service providers, independent of vertical
markets, such as smart grid, connected cars, e-health, etc. The
white paper can be used as a tool to analyze the applicability of
existing requirements and specifications developed by OMA and other
cooperative standards development organizations.
A.4. IPSO Alliance
IPSO Alliance developed a profile for Device Functions supporting
devices such as sensors with a limited user interface, where the
configuration of even basic parameters is impossible to do manually.
This is a challenge especially for consumer devices that are managed
by non-professional users. The configuration of a web service
application running on a constrained device goes beyond the
autoconfiguration of the IP stack and local information (e.g. proxy
address). Constrained devices need additionally service provider and
user account related configuration, such as an address/locator and
the username for a web server.
IPSO discusses the use cases and requirements for user friendly
configuration of such information on a constrained device, and
specifies how IPSO profile Device Function Set can be used in the
process. It furthermore defines a standard format for the basic
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application configuration information.
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Appendix B. Related Research Projects
o The EU project IoT-A (Internet-of-Things Architecture) develops an
architectural reference model together with the definition of an
initial set of key building blocks. These enable the integration
of IoT into the service layer of the Future Internet, and realize
a novel resolution infrastructure, as well as a network
infrastructure that allows the seamless communication flow between
IoT devices and services. The development includes a conceptual
model of a smart object as well as a basic Internet of Things
reference model defining the interaction and communication between
IoT devices and relevant entities. The requirements document
includes also network and information management requirements (see
[EU-IOT-A]).
o The EU project SENSEI specified the document on 'End to End
Networking and Management' for Wireless Sensor and Actuator
Networks. This report presents several research results carried
out in SENSEI's tasks related to End-to-End Networking and
Management. Particular analyses have been addressed related to
naming and addressing of resources, management of resources,
resource plug and play, resource level mobility and traffic
modelling. The detailed analysis on each of these topics is
intended to identify possible gaps between their specific
mechanisms and the functional requirements in the SENSEI reference
architecture (see [EU-SENSEI]).
o The EU project FI-WARE is developing the Things Management GE
(generic enabler), which uses a data model derived from the OMA DM
NGSI data model. Using the abstraction level of things which
include non-technical things like rooms, places and people, Things
Management GE aims to discover and look up IoT resources that can
provide information about things or actuate on these things. The
system aimes to manage the dynamic associations between IoT
resources and things in order to allow internal components as well
as external applications to interact with the system using the
thing abstraction as the core concept (see [EU-FI-WARE]).
o EU project BUTLER Smart Life discusses different IoT management
aspects and collects requirements for smart life use cases (e.g.
smart home or smart city) mainly from service management pov. (see
[EU-IOT-BUTLER]).
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Appendix C. Open issues
o Section 4 on the management requirements, as the core section in
the document, needs further discussion and consolidation.
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Appendix D. Change Log
D.1. 02-03
o Extended the terminology section and removed some of the
terminology addressed in the new LWIG terminology draft.
Referenced the LWIG terminology draft.
o Moved Section 1.3. on Constrained Device Classes to the new LWIG
terminology draft.
o Class of networks considering the different type of radio and
communication technologies in use and dimensions extended.
o Extended the Problem Statement in Section 2. following the
requirements listed in Section 4.
o Following requirements, which belong together and can be realized
with similar or same kind of solutions, have been merged.
* Distributed Management and Peer Configuration,
* Device status monitoring and Neighbor-monitoring,
* Passive Monitoring and Reactive Monitoring,
* Event-driven self-management - Self-healing and Periodic self-
management,
* Authentication of management systems and Authentication of
managed devices,
* Access control on devices and Access control on management
systems,
* Management of Energy Resources and Data models for energy
management,
* Software distribution (group-based firmware update) and Group-
based provisioning.
o Deleted the empty section on the gaps in network management
standards, as it will be written in a separate draft.
o Added links to mentioned external pages.
o Added text on OMA M2M Device Classification in appendix.
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D.2. 01-02
o Extended the terminology section.
o Added additional text for the use cases concerning deployment
type, network topology in use, network size, network capabilities,
radio technology, etc.
o Added examples for device classes in a use case.
o Added additional text provided by Cao Zhen (China Mobile) for
Mobile Applications and by Peter van der Stok for Building
Automation.
o Added the new use cases 'Advanced Metering Infrastructure' and
'MANET Concept of Operations in Military'.
o Added the section 'Managing the Constrainedness of a Device or
Network' discussing the needs of very constrained devices.
o Added a note that the requirements in Section 4 need to be seen as
standalone requirements and the current document does not
recommend any profile of requirements.
o Added Section 4 on the detailed requirements on constrained
management matched to management tasks like fault, monitoring,
configuration management, Security and Access Control, Energy
Management, etc.
o Solved nits and added references.
o Added Appendix A on the related development in other bodies.
o Added Appendix B on the work in related research projects.
D.3. 00-01
o Splitted the section on 'Networks of Constrained Devices' into the
sections 'Network Topology Options' and 'Management Topology
Options'.
o Added the use case 'Community Network Applications' and 'Mobile
Applications'.
o Provided a Contributors section.
o Extended the section on 'Medical Applications'.
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o Solved nits and added references.
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Authors' Addresses
Mehmet Ersue (editor)
Nokia Siemens Networks
Email: mehmet.ersue@nsn.com
Dan Romascanu (editor)
Avaya
Email: dromasca@avaya.com
Juergen Schoenwaelder (editor)
Jacobs University Bremen
Email: j.schoenwaelder@jacobs-university.de
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