wdiff rfc7547.alt-original rfc7547.txt

Internet Engineering Task Force (IETF) M. Ersue, Ed.
Internet-Draft
Request for Comments: 7547 Nokia Networks
Intended status:
Category: Informational D. Romascanu
Expires: September 2, 2015
ISSN: 2070-1721 Avaya
J. Schoenwaelder
Jacobs University Bremen
U. Herberg
March 1,
April 2015

Management of Networks with Constrained Devices:
Problem Statement and Requirements
draft-ietf-opsawg-coman-probstate-reqs-05

Abstract

This document provides a problem statement, deployment and management
topology options options, as well as requirements addressing the different
use cases of the management of networks where constrained devices are
involved.

Status of This Memo

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provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

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approved by the IESG are a maximum candidate for any level of six months Internet
Standard; see Section 2 of RFC 5741.

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This Internet-Draft will expire on September 2, 2015.
http://www.rfc-editor.org/info/rfc7547.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Network Types and Characteristics in Focus . . . . . . . 5
1.4. Constrained Device Deployment Options . . . . . . . . . . 9
1.5. Management Topology Options . . . . . . . . . . . . . . . 9
1.6. Managing the Constrainedness of a Device or Network . . . 10
1.7. Configuration and Monitoring Functionality Levels . . . . 13
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 14
3. Requirements on the Management of Networks with Constrained
Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1. Management Architecture/System . . . . . . . . . . . . . 17
3.2. Management Protocols and Data Models . . . . . . . . . . 21
3.3. Configuration Management . . . . . . . . . . . . . . . . 24
3.4. Monitoring Functionality . . . . . . . . . . . . . . . . 26
3.5. Self-management Self-Management . . . . . . . . . . . . . . . . . . . . . 31
3.6. Security and Access Control . . . . . . . . . . . . . . . 32
3.7. Energy Management . . . . . . . . . . . . . . . . . . . . 34
3.8. Software Distribution . . . . . . . . . . . . . . . . . . 36
3.9. Traffic Management . . . . . . . . . . . . . . . . . . . 36
3.10. Transport Layer . . . . . . . . . . . . . . . . . . . . . 37
3.11. Implementation Requirements . . . . . . . . . . . . . . . 39
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
5. Security Considerations . . . . . . . . . . . . . . . . . . . 40
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41
7.
5. Informative References . . . . . . . . . . . . . . . . . . . 41
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 42
A.1. draft-ietf-opsawg-coman-probstate-reqs-04 - draft-ietf-
opsawg-coman-probstate-reqs-05 . . . . . . . . . . . . . 42
A.2. draft-ietf-opsawg-coman-probstate-reqs-03 - draft-ietf-
opsawg-coman-probstate-reqs-04 . . . . . . . . . . . . . 42
A.3. draft-ietf-opsawg-coman-probstate-reqs-02 - draft-ietf-
opsawg-coman-probstate-reqs-03 . . . . . . . . . . . . . 42
A.4. draft-ietf-opsawg-coman-probstate-reqs-01 - draft-ietf-
opsawg-coman-probstate-reqs-02 .
Acknowledgments . . . . . . . . . . . . 43
A.5. draft-ietf-opsawg-coman-probstate-reqs-00 - draft-ietf-
opsawg-coman-probstate-reqs-01 . . . . . . . . . . . . . 43
A.6. draft-ersue-constrained-mgmt-03 - draft-ietf-opsawg-
coman-probstate-reqs-00 . . . . . . . . . . . . . . . . . 44
A.7. draft-ersue-constrained-mgmt-02-03 . . . . . . . . . . . 44
A.8. draft-ersue-constrained-mgmt-01-02 . . . . . . . . . . . 45
A.9. draft-ersue-constrained-mgmt-00-01 . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46 43

1. Introduction

1.1. Overview

Constrained devices, aka. aka sensor, smart object, or smart device, devices, with
limited CPU, memory, and power resources, 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,
factories and send sending the information to one or more server stations.

Constrained devices may also 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

Today, constrained devices of diverse size and with different
resources and capabilities are being connected. Mobile personal
gadgets, building-automation devices, cellular phones, Machine-to-machine machine-to-
machine (M2M) devices, etc. 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 built 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 faults (and inferring their causes, causes), setting network
parameters, and carrying out actions to remove faults, maintain
normal operation, and improve network efficiency and application
performance. The traditional network monitoring application
periodically collects information from a set of elements that are
needed to manage, manage and processes the data, and it presents them to the
network management users. Constrained devices, however, often have
limited power, have 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 faces a different
type of challenges compared to the management of a traditional IP
network.

The IETF has already done substantial standardization work to enable
the
communication in IP networks and to manage such networks as well as
the manifold type types 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., environment (i.e., devices with very limited memory, CPU, and
energy resources, use resources) nowadays use application-layer protocols in an ad- ad
hoc manner to do simple resource management and monitoring.

This document provides a problem statement and lists requirements for
the different use cases of management of a network with constrained
devices. Section Sections 1.3 and Section 1.5 describe different topology options
for the networking and management of constrained devices. Section 2
provides a problem statement on the issue of the management of
networked constrained devices. Section 3 lists requirements on the
management of applications and networks with constrained devices.
Note that the requirements listed in Section 3 have been separated
from the context in which they may appear. Depending on the concrete
circumstances, an implementer may decide to address a certain
relevant subset of the requirements.

The use cases in the context of networks with constrained devices can
be found in the companion document [COM-USE]. This informational
document [RFC7548]. That Informational RFC provides a list of
objectives for discussions and does not aim to be a strict
requirements document for all use cases. In fact, there likely is
not a single solution that works equally well for all the use cases.

1.2. Terminology

Concerning constrained devices and networks networks, this document generally
builds on the terminology defined in [RFC7228], where the terms
Constrained Device, Constrained Network, etc. and others are defined.

The

Additionally, the following terms are additionally used throughout this
documentation: throughout:

AMI: (Advanced Metering Infrastructure) A system including
hardware, software, and networking technologies that measures,
collects, and analyzes energy usage, use and that communicates with a
hierarchically deployed network of metering devices, either on
request or on a schedule.

C0: Class 0 constrained device as defined in Section 3. 3 of
[RFC7228].

C1: Class 1 constrained device as defined in Section 3. 3 of
[RFC7228].

C2: Class 2 constrained device as defined in Section 3. 3 of
[RFC7228].

Network of Constrained Devices: A network to which constrained
devices are connected that may or may not be a Constrained
Network (see [RFC7228] for the definition of the term
Constrained Network).

M2M: (Machine to Machine) stands for the The automatic data transfer between
devices of different kind. kinds. In M2M scenarios scenarios, a device (such
as a sensor or meter) captures an event, which is relayed
through a network (wireless, wired wired, or hybrid) to an
application.

MANET: Mobile Ad-hoc Networks [RFC2501], a (Mobile Ad Hoc Network [RFC2501]) A self-configuring and
infrastructureless network of mobile devices connected by
wireless technologies.

Smart Grid: An electrical grid that uses communication technologies
to gather and act on information in an automated fashion to
improve the efficiency, reliability reliability, and sustainability of the
production and distribution of electricity.

Smart Meter: An electrical meter in the context of a Smart Grid.

For a detailed discussion on the constrained networks as well as
classes of constrained devices and their capabilities capabilities, please see
[RFC7228].

1.3. Network Types and Characteristics in Focus

In this document document, we differentiate the following types of networks
concerning their transport and communication technologies:

(Note that a network in general can involve constrained and non-
constrained devices.)

1. Wireline non-constrained networks, e.g., an Ethernet-LAN Ethernet LAN with
constrained and non-constrained devices involved.

2. A combination of wireline and wireless networks, possibly with a
multi-hop connectivity between constrained devices, utilizing
dynamic routing in both the wireless and wireline portions of the
network. Such networks usually support highly distributed
applications with many nodes (e.g., environmental monitoring) and
tend to deal with large-scale multipoint-to-point (MP2MP)
systems. Wireless Mesh Networks (WMN), (WMNs), as a specific variant,
use off-the-
shelf off-the-shelf radio technology such as Wi-Fi, WiMax, 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.

3. A combination of wireline and wireless networks with point-to-
point (P2P) or point-to-multipoint (P2MP) communication generally
with single-
hop single-hop connectivity to constrained devices, utilizing
static routing over the wireless network. Such networks support
short-range,
point-to-point, P2P, low-data-rate, source-to-sink type types of
applications
applications, such as RFID systems, light switches, fire and smoke fire/smoke
detectors, and home appliances. This type of networks network also
support
supports 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 such
networks. By using 6LowPAN 6LoWPANs (IPv6 over Low-Power Wireless
Personal Area Networks) [RFC4919] and RPL (IPv6 Routing (Routing Protocol for
Low-Power and Lossy Networks) [RFC6550] on top of IEEE 802.15.4,
multi-hop connectivity and dynamic routing can be achieved. With RPL
RPL, the IETF has specified a proactive route-over "route-over" architecture
where routing and forwarding is implemented at the network layer.
The protocol provides a mechanism whereby
multipoint-to-point, point-to-multipoint MP2P, P2MP, and point-to-point P2P
traffic are supported.

4. Self-configuring infrastructureless networks of mobile devices
(e.g., Mobile Adhoc networks, MANET) are a particular type of network connected by
wireless technologies. Infrastructureless networks are mostly
based on point-to-point P2P communications of devices moving independently in
any direction and changing the links to other devices frequently.
Such devices do act as a router to forward traffic unrelated to
their own use.

Wireline non-constrained networks with constrained and non-
constrained devices are mainly used for specific applications like
Building Automation or Infrastructure Monitoring. Wireline and
wireless networks with multi-hop or point-to-multipoint P2MP connectivity are used used, e.g.,
for environmental monitoring as well as transport and mobile
applications.

Furthermore

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 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 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 or clustered topology). These
different management topology options are described in Section 1.6.

Note that in certain network deployments, such as community ad hoc
networks (see the use case "Community Network Applications" in [COM-
USE]),
[RFC7548]), the topology is not pre-planned, and thus preplanned; thus, it may be unknown
for management purposes. In other use cases, such as industrial
applications (see the use case "Industrial Applications" in [COM-
USE]),
[RFC7548]), 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 as a function of 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 Low-power and lossy networks Lossy Networks (LLNs) on the other side. LLNs
nodes are often duty-cycled and operate on unreliable wireless links
and are potentially mobile (e.g., for sensor networks).

The more dynamic the topology is, the more have routing, transport
and application layer application-layer protocols 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 in the scope of this document if they are used with constrained
devices (see (see, e.g., the use case "Building Automation" in [COM-USE]). [RFC7548]).

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 [RFC7102], including "point-
to-point" (P2P), "multipoint-to-point" (MP2P), P2P,
MP2P, and "point-to-
multipoint" (P2MP) P2MP flows as:

o P2P: Point-To-Point. This Point-to-point refers to traffic exchanged between two nodes
(regardless of the number of hops between the two nodes).

o P2MP: Point-to-Multipoint 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 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 unit of time between two communication end-points. endpoints. 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 kilobytes per second (such as on some
IEEE 802.15.4 link layers) to many Gigabytes gigabytes per second (e.g., on
fiber optics).

For management purposes, the management protocol typically requires
to send
the sending of 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 dropped; thus, management is not possible
with such a protocol.

Networks without bandwidth limitation (e.g., Ethernet) are in-scope in the
scope of this document if they are used with constrained devices (see
the use case "Building Automation" in [COM-USE]). [RFC7548]).

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 10 Gbit Ethernet. For wireless networks, such as IEEE
802.15.4, the bit error rate can be as high as 10^-1 to 1 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.

1.4. Constrained Device Deployment Options

We differentiate the following deployment options for the constrained
devices:

o A network of constrained devices that communicate with each other,

o Constrained devices, which are connected directly to an IP
network,

o A network of constrained devices which that communicate with a gateway
or proxy with more communication capabilities acting possibly acting as a
representative of the device to entities in the non-constrained
network
network,

o Constrained devices, which are connected to the Internet or an IP
network via a gateway/proxy 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
devices - -- connected to one or more gateways - -- connected to some
application servers or NMS system NMS, and

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 entity.

1.5. Management Topology Options

We differentiate the 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 network of constrained devices 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 networks with
constrained devices are managed by the managers at their
corresponding hierarchy level. I.e., That is, each manager is
responsible for managing the nodes in its sub-network. subnetwork. It passes
information from its sub-network subnetwork to its higher-level manager, manager and
disseminates management functions received from the higher-level
manager to its
sub-network. subnetwork. 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 a network or devices.

Note that the list below gives examples and does not claim
completeness.

A constrained device:

o might only support an unreliable (e.g. (e.g., lossy) radio link, i.e.,
the client and server of a management protocol need to gracefully
handle incomplete command exchanges or missing commands.

o might only be able to go online from time-to-time, 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), battery) or may behave as 'sleepy
endpoints'
endpoints', setting their network links to a disconnected state
during long periods of time time, 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 a communication protocol, which is
not IP-based. IP based.

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 that support data compression
(e.g., C2) and devices that do not support data compression (e.g.,
C1 and C0).

o might only be able to support a simple encryption, i.e., it would
be beneficial if the devices use cryptographic algorithms that are
supported in hardware and the encryption used is efficient in
terms of memory and CPU usage.

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, features, i.e., the
managing entity might not be able to monitor all devices in a
network continuously.

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 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 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" "I am alive." message.

o might only be able to support a soft-reset from failure recovery.

o might possibly generate a large amount of redundant reporting
data, i.e., the intermediary management entity (see [RFC7252])
should be able to filter and aggregate redundant data.

A network of constrained devices:

o might only support an unreliable (e.g. (e.g., lossy) radio link, 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 needs to support self-organization, i.e., given the large number
of nodes and their potential placement in hostile locations and
frequently changing topology, manual configuration of nodes is
typically not feasible. As such, the network would benefit from
the ability to reconfigure itself so that it can continue to
operate properly and support reliable connectivity.

o might need a management solution that is energy-efficient, energy efficient, using
as little wireless bandwidth as possible since communication is
highly energy demanding.

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 that 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 or failures detected by the
transport protocol should be handled smoothly. In such a case case, it
should be possible to run the protocol possibly at a reduced level but avoiding to fail
avoid failing completely. E.g., For example, self-monitoring mechanisms
or graceful degradation of features can be used to provide fault
tolerance.

o might require new management capabilities: capabilities, for example, network
coverage information and a constrained device power-distribution- 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.

1.7. Configuration and Monitoring Functionality Levels

Devices often differ significantly on the level of configuration
management support they provide. This document classifies the
configuration management functionality as follows:

CL0: Devices are pre-configured preconfigured and allow no runtime configuration
changes. Configuration parameters are often hard coded and
compiled directly into the firmware image.

CL1: Devices have explicit configuration objects. However, changes
require a restart of the device to take effect.

CL2: Devices allow management systems to replace the entire
configuration (or pre-determined predetermined subsets) in bulk.
Configuration changes take effect by soft-restarts of the
system (or subsystems).

CL3: Devices allow management systems to modify configuration
objects without bulk replacements and changes take effect
immediately.

CL4: Devices support multiple configuration datastores and they
might distinguish between the currently running and the next
startup configuration.

CL5: Devices support configuration datastore locking and device-
local configuration change transactions, i.e., either all
configuration changes are applied or none of them. them are.

CL6: Devices support configuration change transactions across
devices.

This document defines a classification of devices with regards regard to
different levels of monitoring support. In general general, a device may be
in several of the levels listed below:

ML0: Devices push pre-defined predefined monitoring data.

ML1: Devices allow management systems to pull pre-defined predefined monitoring
data.

ML2: Devices allow management systems to pull user-defined filtered
subsets of monitoring data.

ML3: Devices are able to locally process monitoring data in order to
detect threshold crossings or to aggregate data.

At the time of this writing, constrained devices often implement a
combination of one of CL0-CL2 with one of ML0-ML1.

2. Problem Statement

The terminology for the "Internet of Things" is still nascent, and
depending on the network type or layer in focus 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 constraints of the network nodes require a rethinking of
the protocol characteristics concerning power consumption,
performance, bandwidth consumption, memory, and CPU usage. As such,
there is a demand for protocol simplification, energy-efficient
communication, less CPU usage usage, and a smaller memory footprint.

On the application layer layer, the IETF is already developing protocols
like the Constrained Application Protocol (CoAP) [RFC7252] enabling
the communication of constrained devices and networks networks, e.g., for
smart energy applications or home automation environments. The In fact,
the deployment of such an environment involves in fact many, in some
scenarios up to
million million, constrained devices (e.g., smart meters),
which produce a large amount of data. This data needs to be
collected, filtered, and
pre-processed preprocessed for further use in diverse
services.

Considering the high number of nodes to deploy, one has to think
about 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 are already a reality in the standards of some of the
bodies
organizations such as 3GPP. To introduce self-configuration of smart
devices successfully successfully, a device-initiated connection establishment is
often required.

A simple and efficient application layer 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 application- and management management-
related data.

In an ideal world, we would have only one network management protocol
for monitoring, configuration, and exchanging management data,
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

So far, 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., today, devices with very limited memory and CPU
resources, use today,
resources use, e.g., application-layer protocols to do simple
resource management and monitoring. This might be sufficient for
some basic cases, cases; however, there is a need to reconsider the network
management mechanisms based on the new, changed, as well as and reduced
requirements coming from smart devices and the network of such
constrained devices. Albeit Although it is questionable whether we can take
the same comprehensive approach we use in an IP network also and use it
for the management of constrained devices. Hence, the management of
a network with constrained devices is necessary to design necessarily designed in a
simplified and less complex manner.

As Section 1.6 highlights, there are diverse characteristics of
constrained devices or networks, which stem from their
constrainedness and therefore have an impact on the requirements for
the management of such a network with constrained devices. The use
cases discussed in [COM-USE] [RFC7548] 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 features, as
well as the specific issues which that 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 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 that need to be addressed for the
management of a network with constrained
devices devices, please see Section Sections
1.6 and Section 3.

3. 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 listed in this section have been separated
from the context in which they may appear. This In general, this document in general
does not recommend the realization of any subset of the described
requirements. As such such, this document avoids selecting any of the
requirements as mandatory to implement. A device might be able to
provide only a particular selected set of requirements and might not
be capable to provide all requirements in this document. On the
other hand hand, a device vendor might select a specific relevant subset
of the requirements to implement.

The following template is used for the definition of the
requirements.

Req-ID: An ID composed by of two numbers: a section number indicating
the topic area and a unique three-digit number per section section.

Title: The title of the requirement.

Description: The rational rationale and description of the requirement.

Source: The origin of the requirement and the matching use case or
application. For the discussion of referred use cases for
constrained management management, please see [COM-USE]. [RFC7548].

Requirement Type: Functional Requirement, Non-Functional Non-functional
Requirement. A functional requirement is related to a function or
component. As such such, functional requirements may be technical
details,
details or specific functionality that define what a system is
supposed to accomplish. Non-functional requirements (also known
as design constraints or quality requirements) impose
implementation-related considerations such as performance
requirements, security, or reliability.

Device type: The device types by which this requirement can be
supported: C0, C1 C1, and/or C2.

Priority: The priority of the requirement showing its importance for
a particular type of device: High, Medium, and Low. The priority
of a requirement can be High High, e.g., for a C2 device device, but Low for a
C1 or C0 device device, as the realization of complex features in a C1
device is in many cases not possible.

3.1. Management Architecture/System

Req-ID: 1.001

Title: Support multiple device classes within a single network. network

Description: Larger networks usually consist of devices belonging to
different device classes (e.g., constrained mesh endpoints and
less constrained routers) communicating with each other. Hence,
the management architecture must be applicable to networks that
have a mix of different device classes. See Section 3. 3 of
[RFC7228] for the definition of Constrained Device Classes.

Source: All use cases. cases

Requirement Type: Non-Functional Non-functional Requirement

Device type: C1 and/or C2

Priority: High

---

Req-ID: 1.002

Title: Management scalability. 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 that, e.g., the managing
entity is able to handle large amounts 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.
networks

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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
subhierarchy of the network of constraint devices. The
intermediary management entity can can, e.g., support management data
aggregation to handle handle, e.g., high-frequent monitoring data or
provide a caching mechanism for the uplink and downlink
communication. Hierarchical management contributes to management
scalability.

Source: Use cases where a large amount of devices are deployed with
a hierarchical topology. topology

Requirement Type: Non-Functional Non-functional Requirement

Device type: Managing and intermediary entities. entities

Priority: Medium

---

Req-ID: 1.004

Title: Minimize state maintained on constrained devices. 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 restart, for example example, to apply
configuration changes or to recover from extended periods of
inactivity.

Note: 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 that concerns all use cases. cases

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 1.005

Title: Automatic re-synchronization resynchronization with eventual consistency. 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.

Source: Use cases with large scale large-scale networks with many devices. devices

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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. Some classes of devices labeled
as 'sleepy endpoints' set their network links to a disconnected
state during long periods of time. In all cases cases, the management
system must not assume that constrained devices are always
reachable.

Source: Basic requirement for networks of constrained devices with
unreliable links and constrained devices that sleep to save
energy. energy

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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
device-specific configuration from the network-wide configuration.
Such a repository can be used to configure pre-defined predefined 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., For example, monitoring the
performance of a network requires additional information other than additional to what
can be acquired from a single router using a management protocol.

Note: The identification of the relevant subset of the policies to
be provisioned is according to the capabilities of each device and
can be obtained from a pre-configured preconfigured data-repository.

Source: In general general, all use cases of network and device
configuration based on a network view in a top-down manner. manner

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: Medium

---

Req-ID: 1.008
Title: Distributed management

Description: Provide a means of simple distributed management, where
a network of constrained devices 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
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. high

Requirement Type: Non-Functional Non-functional Requirement

Device type: C1 and C2

Priority: Medium

3.2. Management Protocols and Data Models

Req-ID: 2.001

Title: Modular implementation of management protocols

Description: Management protocols should be specified to allow for
modular implementations, i.e., it should be possible to implement
only a basic set of protocol primitives on highly constrained
devices
devices, while devices with additional resources may provide more
support for additional protocol primitives. See Section 1.7 for a
discussion on the level of configuration management and monitoring
support constrained devices may provide.

Source: Basic requirement interesting for all use cases. cases

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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 bandwidth. bandwidth

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 2.003

Title: Compression of management data or complete messages

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 devices, compression may not be feasible.

Source: Use cases where it is beneficial to reduce transmission time
and bandwidth, e.g., mobile applications which that require to save saving on-
air bandwidth. bandwidth

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Medium

---

Req-ID: 2.004

Title: Mapping of management protocol interactions

Description: It is desirable to have a lossless 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 resource-constrained
devices, this goal might not be achievable.

Source: Use cases where high-frequent interaction with the
management system of a non-constrained network is required. required

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Medium

---

Req-ID: 2.005

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 further
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
consistency, and model reuse. reuse

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 2.006

Title: Lossless mapping of management data models. models

Description: It is desirable to have a lossless 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 resource-
constrained devices, this goal might not be achievable.

Source: Use cases where consistent data exchange with the management
system of a non-constrained network is required. required

Requirement Type: Functional Requirement

Device type: C2

Priority: Medium

---

Req-ID: 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 changing requirements on a supported message and
data types effectively, without causing interoperability problems
or having to replace/update large amount of deployed devices.

Source: Basic requirement useful for all use cases. cases

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

3.3. Configuration Management

Req-ID: 3.001

Title: Self-configuration capability

Description: Automatic configuration and re-configuration reconfiguration 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 autoconfiguration
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 general, all use cases requiring easy deployment and
plug&play behavior as well as easy maintenance of many constrained
devices.
devices

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High for device categories C0 and C1, C1; Medium for C2. C2

---

Req-ID: 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.
capabilities

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Medium

---

Req-ID: 3.003

Title: Asynchronous transaction support

Description: Provide configuration management with asynchronous
(event-driven) transaction support. Configuration operations must
support a transactional model, with asynchronous indications that
the transaction was completed.

Source: Use cases that require transaction-oriented processing
because of reliability or distributed architecture functional
requirements.
requirements

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Medium

---

Req-ID: 3.004

Title: Network reconfiguration

Description: Provide a means of iterative network reconfiguration in
order to recover the network from node and communication failures.
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

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: Medium

3.4. Monitoring Functionality

Req-ID: 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
caching mechanism. The device monitoring might also make use of
neighbor-monitoring (fault detection in the 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: High, High; Medium for neighbor-monitoring. neighbor-monitoring

---

Req-ID: 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 average power consumption).

Source: Use case Energy Management

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High for energy reporting devices, devices; Low for others. others

---

Req-ID: 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 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: Medium

---
Req-ID: 4.004

Title: Network status monitoring

Description: Provide a monitoring function to collect, analyze analyze, and
expose information related to the status of a network or network
segments connected to the interface of the device.

Source: All use cases. cases

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Low, based on the realization complexity. complexity

---

Req-ID: 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
an appropriate manner, e.g., self-healing is required. required

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: High for C2, C2; Medium for C1

---

Req-ID: 4.006

Title: Performance monitoring

Description: The device will provide a monitoring function to
collect and expose information about the basic performance
parameter of the device. The performance management functionality
might make use of the hierarchical management through the
intermediary devices.

Source: Use cases Building automation, automation and Transport applications
Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: Low

---

Req-ID: 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 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 devices, the monitoring might be limited
to the check whether or not the device is alive or not. alive.

Source: Use cases Environmental Monitoring, Building Automation,
Energy Management, Infrastructure Monitoring

Requirement Type: Functional Requirement

Device type: C0, C1 and C2

Priority: Medium

---

Req-ID: 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 occurred, the system or the manager can adaptively
react (reactive monitoring), e.g., reconfigure the network. Typically
Typically, actions (re-actions) (reactions) 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: Medium

---

Req-ID: 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. managers

Requirement Type: Functional Requirement

Device type: C2

Priority: Medium

---

Req-ID: 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: Low, based on the realization complexity. complexity

---

Req-ID: 4.011
Title: Notifications

Description: The device will provide the capability of sending
notifications on critical events and faults.

Source: All use cases. cases

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: Medium for C2, C2; Low for C0 and C1

---

Req-ID: 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: High for some medical or industrial applications, applications; Medium
otherwise

3.5. Self-management Self-Management

Req-ID: 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 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 on a schedule in order 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.

Source: The requirement generally relates to all use cases in this
document.

Requirement Type: Functional Requirement

Device type: C1 and C2

Priority: High for C2, C2; Medium for C1

3.6. Security and Access Control

Req-ID: 6.001

Title: Authentication of management system and devices. 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 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
(re-)started at about the same time. Protocols and authentication
systems should be designed such that a large number of devices
(re)starting
(re-)starting simultaneously does not negatively impact the device
authentication process.

Source: Basic security requirement for all use cases. cases

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High, High; Medium for the (re)start (re-)start of a large number of
devices

---

Req-ID: 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 provide them with appropriate access control
permissions.

Source: Basic security requirement for all use cases. cases

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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
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. essential

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 6.004

Title: Select cryptographic algorithms that are efficient in both
code space and execution time. time

Description: Cryptographic algorithms have a major impact in terms
of both code size and overall execution time. It Therefore, it is therefore
necessary to select mandatory to implement cryptographic
algorithms that are reasonable to implement with the available
code space and that have a small impact at runtime. Furthermore 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 wireless technologies.

Source: Generic requirement to reduce the footprint and CPU usage of
a constrained device. device

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High, High; Medium for hardware-supported algorithms. algorithms

3.7. Energy Management

Req-ID: 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
criteria, e.g., importance levels pre-defined predefined 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 (work ongoing). It might be necessary to use a
subset of EMAN MIBs for C1 and C2 devices.

Source: Use case Energy Management

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: Medium for the use case Energy Management, Management; Low otherwise. otherwise

---

Req-ID: 7.002

Title: Support of energy-optimized communication protocols

Description: Use of an optimized communication protocol to minimize
energy usage use for the device (radio) receiver/transmitter, on-air
bandwidth (protocol efficiency), reduced amount of data
communication between nodes (implies data aggregation and
filtering but also a compact format for the transferred data).

Source: Use cases Energy Management and Mobile Applications. Applications

Requirement Type: Non-Functional Non-functional Requirement

Device type: C2

Priority: Medium

---

Req-ID: 7.003

Title: Support for layer Layer 2 (L2) energy-aware protocols

Description: The device will support layer 2 energy management L2 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: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: Medium

---

Req-ID: 7.004

Title: Dying gasp

Description: When energy resources draw below the red line red-line level,
the device will send a dying gasp "dying gasp" notification and perform perform, if
still possible 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

Priority: Medium

3.8. Software Distribution

Req-ID: 8.001

Title: Group-based provisioning

Description: Support group-based provisioning, i.e., firmware update
and configuration management, 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, group and which
may share a common data model. Activation of configuration may be
based on pre-loaded preloaded sets of default values.

Source: All use cases

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: Medium

3.9. Traffic Management

Req-ID: 9.001

Title: Congestion avoidance

Description: Support congestion control principles as defined in
[RFC2914], e.g., 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 traffic, e.g., AMI or
M2M.
M2M

Requirement Type: Non-Functional Non-functional Requirement

Device type: C1 and C2

Priority: Medium
---

Req-ID: 9.002

Title: Reroute 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 traffic, e.g., AMI or
M2M.
M2M

Requirement Type: Non-Functional Non-functional Requirement

Device type: Intermediary entity in the network. network

Priority: Medium

---

Req-ID: 9.003

Title: Traffic Shaping. Shaping

Description: Provide the ability to apply traffic shaping traffic-shaping policies
to incoming and outgoing links on an overloaded intermediary node
as necessary
(as necessary) in order to reduce the amount of traffic in the
network.

Source: Use cases with high reporting rate and traffic traffic, e.g., AMI or
M2M.
M2M

Requirement Type: Non-Functional Non-functional Requirement

Device type: Intermediary entity in the network. network

Priority: Medium

3.10. Transport Layer

Req-ID: 10.001

Title: Scalable transport layer
Description: Enable the use of a scalable transport layer, i.e., not
sensitive to a high rate of incoming client requests, which is
useful for applications requiring frequent access to device data.

Source: Applications with high frequent access to the device data. data

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1 and C2

Priority: Medium

---

Req-ID: 10.002

Title: Reliable unicast transport of messages

Description: Diverse applications need a reliable transport of
messages. The reliability might be achieved based on a transport
protocol such as TCP or can be supported based on message
repetition if an acknowledgment is missing.

Source: Generally Generally, applications benefit from the reliability of the
message transport. transport

Requirement Type: Functional Requirement

Device type: C0, C1, and C2

Priority: High

---

Req-ID: 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.

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. M2M

Requirement Type: Functional Requirement
Device type: C0, C1, and C2

Priority: Medium

---

Req-ID: 10.004

Title: Secure message transport

Description: Enable secure message transport providing
authentication, data integrity, and confidentiality by using
existing
transport layer transport-layer technologies with a small footprint such
as TLS/
DTLS. TLS/DTLS.

Source: All use cases. cases

Requirement Type: Non-Functional Non-functional Requirements

Device type: C1 and C2

Priority: High

3.11. Implementation Requirements

Req-ID: 11.001

Title: Avoid complex application layer application-layer transactions requiring large
application layer messages.
application-layer messages

Description: Complex application layer 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 split a large transaction into a sequence
of smaller transactions that require less resources and allow to
make
making progress using a sequence of smaller steps.

Source: Basic requirement which that concerns all use cases with memory
constrained devices. devices

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High
---

Req-ID: 11.002

Title: Avoid reassembly of messages at multiple layers in the
protocol stack. 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 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 that concerns all use cases with memory
constrained devices. devices

Requirement Type: Non-Functional Non-functional Requirement

Device type: C0, C1, and C2

Priority: High

4. 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.

5. Security Considerations

This document discusses the problem statement and requirements on
networks of constrained devices. Section 1.6 mentions a number of
limitations that could prevent the implementation of strong
cryptographic algorithms. Requirements for security and access
control are listed in Section 3.6.

Constrained

Often, constrained devices might be deployed often in unsafe environments, environments
where attackers can gain physical access to the devices. As a
consequence, it is crucial that devices are robust and tamper
resistant, have no backdoors, do not provide services that are not
essential for the primary function, and properly protect any security
credentials that may be stored on the device (e.g., by using hardware
protection mechanisms). Furthermore, it is important that any
credentials leaking from a single device do not simplify the attack
on other (similar) devices. In particular, security credentials
should never be shared.

Since constrained devices often have limited computational resources,
care should be taken in choosing efficient but cryptographically
strong cryptographic algorithms. Designers of constrained devices
that have a long expected lifetime need to ensure that cryptographic
algorithms can be updated once devices have been deployed. The
ability to perform secure firmware and software updates is an
important management requirement.

Constrained devices might also generate sensitive data or require the
processing of sensitive data. It Therefore, it is therefore an important
requirement to properly protect access to the data in order to
protect the privacy of humans using Internet-enabled devices. For
certain types of data, protection during the transmission over the
network may not be sufficient sufficient, and methods should be investigated
that provide protection of data while it is cached or stored (e.g.,
when using a store-and-forward transport mechanism).

6. Acknowledgments

Following persons reviewed and provided valuable comments to
different versions of this document:

Dominique Barthel, Andy Bierman, Carsten Bormann, Zhen Cao, Benoit
Claise, Hui Deng, Bert Greevenbosch, Joel M. Halpern, Ulrich
Herberg, James Nguyen, Anuj Sehgal, Zach Shelby, Peter van der Stok,
Thomas Watteyne, and Bert Wijnen.

The editors would like to thank the reviewers and the participants on
the Coman and OPSAWG mailing lists for their valuable contributions
and comments.

5. Informative References

[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC
2914, September 2000. 2000,
<http://www.rfc-editor.org/info/rfc2914>.

[RFC2501] Corson, M. S. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999. 1999,
<http://www.rfc-editor.org/info/rfc2501>.

[RFC6632] Ersue, M. M., Ed. and B. Claise, "An Overview of the IETF
Network Management Standards", RFC 6632, June 2012. 2012,
<http://www.rfc-editor.org/info/rfc6632>.

[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, January 2014. 2014,
<http://www.rfc-editor.org/info/rfc7102>.

[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, May 2014. 2014,
<http://www.rfc-editor.org/info/rfc7228>.

[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, June 2014. 2014,
<http://www.rfc-editor.org/info/rfc7252>.

[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals", RFC
4919, August 2007. 2007,
<http://www.rfc-editor.org/info/rfc4919>.

[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, March 2012.

[COM-USE] 2012,
<http://www.rfc-editor.org/info/rfc6550>.

[RFC7548] Ersue, M., Ed., Romascanu, D., Schonwalder, J., and J. Schoenwaelder, A.
Sehgal, "Constrained Management: Use Cases", draft-ietf-opsawg-
coman-use-cases (work in progress), July 2014. RFC 7548,
April 2015, <http://www.rfc-editor.org/info/rfc7548>.

Acknowledgments

The following reviewed and provided valuable comments during the
creation of this document:

Dominique Barthel, Andy Bierman, Carsten Bormann, Zhen Cao, Benoit
Claise, Hui Deng, Bert Greevenbosch, Joel M. Halpern, Ulrich Herberg,
James Nguyen, Anuj Sehgal, Zach Shelby, Peter van der Stok, Thomas
Watteyne, and Bert Wijnen.

The editors would like to thank the reviewers and the participants on
the Coman and OPSAWG mailing lists for their valuable contributions
and comments.

Authors' Addresses

Mehmet Ersue (editor)
Nokia Networks

Email: mehmet.ersue@nsn.com

EMail: mehmet.ersue@nokia.com

Dan Romascanu
Avaya

Email:

EMail: dromasca@avaya.com

Juergen Schoenwaelder
Jacobs University Bremen

Email:

EMail: j.schoenwaelder@jacobs-university.de

Ulrich Herberg

Email:

EMail: ulrich@herberg.name