Internet Engineering Task Force (IETF) C. Bormann
Request for Comments: 7228 Universitaet Bremen TZI
Category: Informational M. Ersue
ISSN: 2070-1721 Nokia Solutions and Networks
A. Keranen
Ericsson
May 2014
Internet Engineering Task Force (IETF) C. Bormann
Request for Comments: 7228 Universitaet Bremen TZI
Category: Informational M. Ersue
ISSN: 2070-1721 Nokia Solutions and Networks
A. Keranen
Ericsson
May 2014
Terminology for Constrained-Node Networks
约束节点网络术语
Abstract
摘要
The Internet Protocol Suite is increasingly used on small devices with severe constraints on power, memory, and processing resources, creating constrained-node networks. This document provides a number of basic terms that have been useful in the standardization work for constrained-node networks.
Internet协议套件越来越多地用于对电源、内存和处理资源有严重限制的小型设备，从而创建受限制的节点网络。本文档提供了一些基本术语，这些术语在受限节点网络的标准化工作中非常有用。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。并非IESG批准的所有文件都适用于任何级别的互联网标准；见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7228.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc7228.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................3
2. Core Terminology ................................................4
2.1. Constrained Nodes ..........................................4
2.2. Constrained Networks .......................................5
2.2.1. Challenged Networks .................................6
2.3. Constrained-Node Networks ..................................7
2.3.1. LLN .................................................7
2.3.2. LoWPAN, 6LoWPAN .....................................8
3. Classes of Constrained Devices ..................................8
4. Power Terminology ..............................................10
4.1. Scaling Properties ........................................10
4.2. Classes of Energy Limitation ..............................11
4.3. Strategies for Using Power for Communication ..............12
5. Security Considerations ........................................14
6. Acknowledgements ...............................................14
7. Informative References .........................................14
1. Introduction ....................................................3
2. Core Terminology ................................................4
2.1. Constrained Nodes ..........................................4
2.2. Constrained Networks .......................................5
2.2.1. Challenged Networks .................................6
2.3. Constrained-Node Networks ..................................7
2.3.1. LLN .................................................7
2.3.2. LoWPAN, 6LoWPAN .....................................8
3. Classes of Constrained Devices ..................................8
4. Power Terminology ..............................................10
4.1. Scaling Properties ........................................10
4.2. Classes of Energy Limitation ..............................11
4.3. Strategies for Using Power for Communication ..............12
5. Security Considerations ........................................14
6. Acknowledgements ...............................................14
7. Informative References .........................................14
Small devices with limited CPU, memory, and power resources, so-called "constrained devices" (often used as sensors/actuators, smart objects, or smart devices) can form a network, becoming "constrained nodes" in that network. Such a network may itself exhibit constraints, e.g., with unreliable or lossy channels, limited and unpredictable bandwidth, and a highly dynamic topology.
CPU、内存和电源资源有限的小型设备，即所谓的“受限设备”（通常用作传感器/执行器、智能对象或智能设备）可以形成网络，成为该网络中的“受限节点”。这样的网络本身可能表现出约束，例如，具有不可靠或有损信道、有限且不可预测的带宽以及高度动态的拓扑。
Constrained devices might be in charge of gathering information in diverse settings, including natural ecosystems, buildings, and factories, and sending the information to one or more server stations. They might also act on information, by performing some physical action, including displaying it. Constrained devices may work under severe resource constraints such as limited battery and computing power, little memory, and insufficient wireless bandwidth and ability to communicate; these constraints often exacerbate each other. Other entities on the network, e.g., a base station or controlling server, might have more computational and communication resources and could support the interaction between the constrained devices and applications in more traditional networks.
受约束的设备可能负责在各种环境中收集信息，包括自然生态系统、建筑物和工厂，并将信息发送到一个或多个服务器站。他们还可以通过执行一些物理操作（包括显示）对信息进行操作。受限制的设备可能在严重的资源限制下工作，如电池和计算能力有限、内存不足、无线带宽和通信能力不足；这些制约因素往往相互加剧。网络上的其他实体，例如基站或控制服务器，可能具有更多的计算和通信资源，并且可以支持更传统网络中受约束的设备和应用程序之间的交互。
Today, diverse sizes of constrained devices with different resources and capabilities are becoming connected. Mobile personal gadgets, building-automation devices, cellular phones, machine-to-machine (M2M) devices, and other devices benefit from interacting with other "things" nearby or somewhere in the Internet. With this, the Internet of Things (IoT) becomes a reality, built up out of uniquely identifiable and addressable objects (things). Over the next decade, this could grow to large numbers [FIFTY-BILLION] of Internet-connected constrained devices, greatly increasing the Internet's size and scope.
如今，具有不同资源和功能的各种尺寸的受限设备正在连接起来。移动个人小工具、楼宇自动化设备、手机、机器对机器（M2M）设备和其他设备从与互联网附近或某处的其他“事物”的交互中获益。由此，物联网（IoT）成为现实，由唯一可识别和可寻址的对象（物）构建而成。在未来十年，这可能会增长到大量（500亿）互联网连接受限设备，大大增加互联网的规模和范围。
The present document provides a number of basic terms that have been useful in the standardization work for constrained environments. The intention is not to exhaustively cover the field but to make sure a few core terms are used consistently between different groups cooperating in this space.
本文件提供了一些在受限环境标准化工作中有用的基本术语。目的不是详尽地涵盖该领域，而是确保在该领域合作的不同团体之间一致使用一些核心术语。
In this document, the term "byte" is used in its now customary sense as a synonym for "octet". Where sizes of semiconductor memory are given, the prefix "kibi" (1024) is combined with "byte" to "kibibyte", abbreviated "KiB", for 1024 bytes [ISQ-13].
在本文件中，“字节”一词是作为“八位字节”的同义词使用的。在给定半导体存储器大小的情况下，前缀“kibi”（1024）与“byte”到“kibibyte”组合，缩写为“KiB”，表示1024字节[ISQ-13]。
In computing, the term "power" is often used for the concept of "computing power" or "processing power", as in CPU performance. In this document, the term stands for electrical power unless explicitly stated otherwise. "Mains-powered" is used as a shorthand for being permanently connected to a stable electrical power grid.
在计算中，术语“能力”通常用于“计算能力”或“处理能力”的概念，如CPU性能。在本文件中，除非另有明确说明，否则术语代表电力。“市电供电”用作永久连接到稳定电网的简写。
There are two important aspects to _scaling_ within the Internet of Things:
物联网中的“缩放”有两个重要方面：
o scaling up Internet technologies to a large number [FIFTY-BILLION] of inexpensive nodes, while
o 将互联网技术扩展到大量（500亿）廉价节点
o scaling down the characteristics of each of these nodes and of the networks being built out of them, to make this scaling up economically and physically viable.
o 缩小每个节点的特性以及由其构建的网络的特性，以使这种扩展在经济上和物理上可行。
The need for scaling down the characteristics of nodes leads to "constrained nodes".
缩小节点特征的需要导致“受限节点”。
The term "constrained node" is best defined by contrasting the characteristics of a constrained node with certain widely held expectations on more familiar Internet nodes:
术语“受约束节点”的最佳定义是将受约束节点的特征与对更熟悉的互联网节点的某些广泛期望进行对比：
Constrained Node: A node where some of the characteristics that are otherwise pretty much taken for granted for Internet nodes at the time of writing are not attainable, often due to cost constraints and/or physical constraints on characteristics such as size, weight, and available power and energy. The tight limits on power, memory, and processing resources lead to hard upper bounds on state, code space, and processing cycles, making optimization of energy and network bandwidth usage a dominating consideration in all design requirements. Also, some layer-2 services such as full connectivity and broadcast/multicast may be lacking.
受限节点：在撰写本文时，互联网节点在其他方面几乎被视为理所当然的一些特性无法实现的节点，通常是由于尺寸、重量、可用功率和能量等特性的成本约束和/或物理约束。对电源、内存和处理资源的严格限制导致了状态、代码空间和处理周期的硬上限，使得能源和网络带宽使用的优化成为所有设计需求的主要考虑因素。此外，可能缺少一些第二层服务，例如完全连接和广播/多播。
While this is not a rigorous definition, it is grounded in the state of the art and clearly sets apart constrained nodes from server systems, desktop or laptop computers, powerful mobile devices such as smartphones, etc. There may be many design considerations that lead to these constraints, including cost, size, weight, and other scaling factors.
虽然这不是一个严格的定义，但它基于最先进的技术，明确地将受约束的节点与服务器系统、台式机或笔记本电脑、智能手机等功能强大的移动设备区分开来。可能有许多设计考虑因素导致这些约束，包括成本、尺寸、重量和其他比例因素。
(An alternative term, when the properties as a network node are not in focus, is "constrained device".)
（当作为网络节点的属性不在焦点时，另一个术语是“受约束设备”。）
There are multiple facets to the constraints on nodes, often applying in combination, for example:
节点上的约束有多个方面，通常组合应用，例如：
o constraints on the maximum code complexity (ROM/Flash),
o 对最大代码复杂度（ROM/Flash）的限制，
o constraints on the size of state and buffers (RAM),
o 对状态和缓冲区（RAM）大小的限制，
o constraints on the amount of computation feasible in a period of time ("processing power"),
o 一段时间内可行计算量的限制（“处理能力”），
o constraints on the available power, and
o 对可用电源的限制，以及
o constraints on user interface and accessibility in deployment (ability to set keys, update software, etc.).
o 部署中对用户界面和可访问性的限制（设置密钥、更新软件等的能力）。
Section 3 defines a small number of interesting classes ("class-N" for N = 0, 1, 2) of constrained nodes focusing on relevant combinations of the first two constraints. With respect to available power, [RFC6606] distinguishes "power-affluent" nodes (mains-powered or regularly recharged) from "power-constrained nodes" that draw their power from primary batteries or by using energy harvesting; more detailed power terminology is given in Section 4.
第3节定义了一小部分受约束节点的有趣类（N=0、1、2的“类-N”），重点关注前两个约束的相关组合。关于可用功率，[RFC6606]将“功率充足”节点（市电供电或定期充电）与“功率受限节点”区分开来，后者从原电池或通过能量收集获取电力；第4节给出了更详细的电源术语。
The use of constrained nodes in networks often also leads to constraints on the networks themselves. However, there may also be constraints on networks that are largely independent from those of the nodes. We therefore distinguish "constrained networks" from "constrained-node networks".
在网络中使用受约束节点通常也会导致对网络本身的约束。然而，在网络上也可能存在很大程度上独立于节点的约束。因此，我们将“受限网络”与“受限节点网络”区分开来。
We define "constrained network" in a similar way:
我们以类似的方式定义“受限网络”：
Constrained Network: A network where some of the characteristics pretty much taken for granted with link layers in common use in the Internet at the time of writing are not attainable.
受限网络：在撰写本文时，互联网上常用的链接层的某些特性几乎被认为是理所当然的，但却无法实现的网络。
Constraints may include:
限制可能包括：
o low achievable bitrate/throughput (including limits on duty cycle),
o 低可实现比特率/吞吐量（包括占空比限制），
o high packet loss and high variability of packet loss (delivery rate),
o 高数据包丢失和数据包丢失的高可变性（传输速率），
o highly asymmetric link characteristics,
o 高度不对称的链路特性，
o severe penalties for using larger packets (e.g., high packet loss due to link-layer fragmentation),
o 使用较大数据包的严重处罚（例如，由于链路层碎片导致的高数据包丢失），
o limits on reachability over time (a substantial number of devices may power off at any point in time but periodically "wake up" and can communicate for brief periods of time), and
o 随时间推移的可达性限制（相当数量的设备可能在任何时间点断电，但会定期“唤醒”，并可短时间通信），以及
o lack of (or severe constraints on) advanced services such as IP multicast.
o 缺乏（或严重限制）IP多播等高级服务。
More generally, we speak of constrained networks whenever at least some of the nodes involved in the network exhibit these characteristics.
更一般地说，只要网络中至少有一些节点表现出这些特征，我们就谈论约束网络。
Again, there may be several reasons for this:
同样，这可能有几个原因：
o cost constraints on the network,
o 网络上的成本限制，
o constraints posed by the nodes (for constrained-node networks),
o 由节点构成的约束（对于受约束的节点网络），
o physical constraints (e.g., power constraints, environmental constraints, media constraints such as underwater operation, limited spectrum for very high density, electromagnetic compatibility),
o 物理约束（例如，功率约束、环境约束、介质约束，如水下操作、极高密度的有限频谱、电磁兼容性），
o regulatory constraints, such as very limited spectrum availability (including limits on effective radiated power and duty cycle) or explosion safety, and
o 监管限制，如频谱可用性非常有限（包括有效辐射功率和占空比限制）或爆炸安全，以及
o technology constraints, such as older and lower-speed technologies that are still operational and may need to stay in use for some more time.
o 技术限制，如仍在运行且可能需要继续使用一段时间的旧技术和低速技术。
A constrained network is not necessarily a "challenged network" [FALL]:
受限网络不一定是“挑战网络”[FALL]：
Challenged Network: A network that has serious trouble maintaining what an application would today expect of the end-to-end IP model, e.g., by:
挑战网络：在维护应用程序目前对端到端IP模型的期望方面存在严重问题的网络，例如：
* not being able to offer end-to-end IP connectivity at all,
* 根本无法提供端到端IP连接，
* exhibiting serious interruptions in end-to-end IP connectivity, or
* 端到端IP连接出现严重中断，或
* exhibiting delay well beyond the Maximum Segment Lifetime (MSL) defined by TCP [RFC0793].
* 延迟远远超过TCP[RFC0793]定义的最大段寿命（MSL）。
All challenged networks are constrained networks in some sense, but not all constrained networks are challenged networks. There is no well-defined boundary between the two, though. Delay-Tolerant Networking (DTN) has been designed to cope with challenged networks [RFC4838].
从某种意义上说，所有受挑战的网络都是受约束的网络，但并非所有受约束的网络都是受挑战的网络。不过，两者之间没有明确的界限。延迟容忍网络（DTN）设计用于应对挑战性网络[RFC4838]。
Constrained-Node Network: A network whose characteristics are influenced by being composed of a significant portion of constrained nodes.
受约束节点网络：其特性受很大一部分受约束节点影响的网络。
A constrained-node network always is a constrained network because of the network constraints stemming from the node constraints, but it may also have other constraints that already make it a constrained network.
受约束节点网络始终是受约束网络，因为网络约束源自节点约束，但它也可能具有其他约束，这些约束已使其成为受约束网络。
The rest of this subsection introduces two additional terms that are in active use in the area of constrained-node networks, without an intent to define them: LLN and (6)LoWPAN.
本小节的其余部分介绍了在受约束节点网络领域积极使用的两个附加术语，但无意对其进行定义：LLN和（6）LoWPAN。
A related term that has been used to describe the focus of the IETF ROLL working group is "Low-Power and Lossy Network (LLN)". The ROLL (Routing Over Low-Power and Lossy) terminology document [RFC7102] defines LLNs as follows:
用于描述IETF滚动工作组重点的一个相关术语是“低功耗和有损网络（LLN）”。滚动（低功耗和有损布线）术语文档[RFC7102]对LLN的定义如下：
LLN: Low-Power and Lossy Network. Typically composed of many embedded devices with limited power, memory, and processing resources interconnected by a variety of links, such as IEEE 802.15.4 or low-power Wi-Fi. There is a wide scope of application areas for LLNs, including industrial monitoring, building automation (heating, ventilation, and air conditioning (HVAC), lighting, access control, fire), connected home, health care, environmental monitoring, urban sensor networks, energy management, assets tracking, and refrigeration.
LLN：低功耗和有损网络。通常由许多嵌入式设备组成，这些设备具有有限的电源、内存和处理资源，通过各种链路互连，如IEEE 802.15.4或低功耗Wi-Fi。LLN有广泛的应用领域，包括工业监控、楼宇自动化（供暖、通风和空调（HVAC）、照明、门禁、消防）、联网家庭、医疗保健、环境监控、城市传感器网络、能源管理、资产跟踪和制冷。
Beyond that, LLNs often exhibit considerable loss at the physical layer, with significant variability of the delivery rate, and some short-term unreliability, coupled with some medium-term stability that makes it worthwhile to both construct directed acyclic graphs that are medium-term stable for routing and do measurements on the edges such as Expected Transmission Count (ETX) [RFC6551]. Not all LLNs comprise low-power nodes [RPL-DEPLOYMENT].
除此之外，LLN通常在物理层表现出相当大的损失，交付率具有显著的可变性，并且存在一些短期的不可靠性，再加上一些中期稳定性，这使得有必要构造中期稳定的有向无环图，并在边上进行测量，如预期传输计数（ETX）[RFC6551]。并非所有LLN都包含低功耗节点[RPL-DEPLOYMENT]。
LLNs typically are composed of constrained nodes; this leads to the design of operation modes such as the "non-storing mode" defined by RPL (the IPv6 Routing Protocol for Low-Power and Lossy Networks [RFC6550]). So, in the terminology of the present document, an LLN is a constrained-node network with certain network characteristics, which include constraints on the network as well.
LLN通常由受约束的节点组成；这导致了操作模式的设计，如RPL（低功耗和有损网络的IPv6路由协议[RFC6550]）定义的“非存储模式”。因此，在本文档的术语中，LLN是具有特定网络特征的受约束节点网络，其也包括对网络的约束。
One interesting class of a constrained network often used as a constrained-node network is "LoWPAN" [RFC4919], a term inspired from the name of an IEEE 802.15.4 working group (low-rate wireless personal area networks (LR-WPANs)). The expansion of the LoWPAN acronym, "Low-Power Wireless Personal Area Network", contains a hard-to-justify "Personal" that is due to the history of task group naming in IEEE 802 more than due to an orientation of LoWPANs around a single person. Actually, LoWPANs have been suggested for urban monitoring, control of large buildings, and industrial control applications, so the "Personal" can only be considered a vestige. Occasionally, the term is read as "Low-Power Wireless Area Networks" [WEI]. Originally focused on IEEE 802.15.4, "LoWPAN" (or when used for IPv6, "6LoWPAN") also refers to networks built from similarly constrained link-layer technologies [V6-BTLE] [V6-DECT-ULE] [V6-G9959].
通常用作受约束节点网络的受约束网络的一个有趣类别是“LoWPAN”[RFC4919]，该术语来源于IEEE 802.15.4工作组（低速无线个人区域网络（LR WPAN））的名称。LoWPAN首字母缩略词“低功耗无线个人区域网络”的扩展包含一个难以证明的“个人”，这是由于IEEE 802中任务组命名的历史，而不是由于LoWPANs围绕单个人的方向。事实上，低面板已经被建议用于城市监控、大型建筑控制和工业控制应用，因此“个人”只能被视为遗迹。有时，该术语被解读为“低功率无线区域网络”[WEI]。最初主要关注IEEE 802.15.4，“LoWPAN”（或用于IPv6时，“6LoWPAN”）也指由类似受限链路层技术构建的网络[V6-BTLE][V6-DECT-ULE][V6-G9959]。
Despite the overwhelming variety of Internet-connected devices that can be envisioned, it may be worthwhile to have some succinct terminology for different classes of constrained devices. In this document, the class designations in Table 1 may be used as rough indications of device capabilities:
尽管可以预见到各种各样的互联网连接设备，但为不同类别的受约束设备提供一些简洁的术语可能是值得的。在本文件中，表1中的类别名称可用作设备性能的粗略指示：
+-------------+-----------------------+-------------------------+
| Name | data size (e.g., RAM) | code size (e.g., Flash) |
+-------------+-----------------------+-------------------------+
| Class 0, C0 | << 10 KiB | << 100 KiB |
| | | |
| Class 1, C1 | ~ 10 KiB | ~ 100 KiB |
| | | |
| Class 2, C2 | ~ 50 KiB | ~ 250 KiB |
+-------------+-----------------------+-------------------------+
+-------------+-----------------------+-------------------------+
| Name | data size (e.g., RAM) | code size (e.g., Flash) |
+-------------+-----------------------+-------------------------+
| Class 0, C0 | << 10 KiB | << 100 KiB |
| | | |
| Class 1, C1 | ~ 10 KiB | ~ 100 KiB |
| | | |
| Class 2, C2 | ~ 50 KiB | ~ 250 KiB |
+-------------+-----------------------+-------------------------+
Table 1: Classes of Constrained Devices (KiB = 1024 bytes)
表1：受约束设备的类别（KiB=1024字节）
As of the writing of this document, these characteristics correspond to distinguishable clusters of commercially available chips and design cores for constrained devices. While it is expected that the
在撰写本文件时，这些特性对应于可区分的商用芯片集群和受限设备的设计核心。虽然预计
boundaries of these classes will move over time, Moore's law tends to be less effective in the embedded space than in personal computing devices: gains made available by increases in transistor count and density are more likely to be invested in reductions of cost and power requirements than into continual increases in computing power.
随着时间的推移，这些类别的界限将发生变化，摩尔定律在嵌入式空间的效果往往不如在个人计算设备中有效：晶体管数量和密度增加带来的收益更有可能投资于降低成本和功率需求，而不是持续提高计算能力。
Class 0 devices are very constrained sensor-like motes. They are so severely constrained in memory and processing capabilities that most likely they will not have the resources required to communicate directly with the Internet in a secure manner (rare heroic, narrowly targeted implementation efforts notwithstanding). Class 0 devices will participate in Internet communications with the help of larger devices acting as proxies, gateways, or servers. Class 0 devices generally cannot be secured or managed comprehensively in the traditional sense. They will most likely be preconfigured (and will be reconfigured rarely, if at all) with a very small data set. For management purposes, they could answer keepalive signals and send on/ off or basic health indications.
0类设备是非常受限的传感器，如尘粒。它们的内存和处理能力受到严重限制，很可能无法以安全的方式直接与互联网进行通信（尽管很少有英勇的、目标明确的实施工作）。0类设备将在作为代理、网关或服务器的大型设备的帮助下参与互联网通信。在传统意义上，0类设备通常无法得到全面的保护或管理。它们很可能是用一个非常小的数据集预配置的（并且很少重新配置，如果有的话）。出于管理目的，他们可以应答保持信号并发送开/关或基本健康指示。
Class 1 devices are quite constrained in code space and processing capabilities, such that they cannot easily talk to other Internet nodes employing a full protocol stack such as using HTTP, Transport Layer Security (TLS), and related security protocols and XML-based data representations. However, they are capable enough to use a protocol stack specifically designed for constrained nodes (such as the Constrained Application Protocol (CoAP) over UDP [COAP]) and participate in meaningful conversations without the help of a gateway node. In particular, they can provide support for the security functions required on a large network. Therefore, they can be integrated as fully developed peers into an IP network, but they need to be parsimonious with state memory, code space, and often power expenditure for protocol and application usage.
第1类设备在代码空间和处理能力方面受到很大限制，因此它们无法轻松与采用完整协议栈（如使用HTTP、传输层安全性（TLS）和相关安全协议以及基于XML的数据表示）的其他Internet节点进行通信。但是，它们能够使用专门为受约束节点设计的协议栈（例如UDP[CoAP]上的受约束应用程序协议（CoAP）），并在没有网关节点帮助的情况下参与有意义的对话。特别是，它们可以为大型网络上所需的安全功能提供支持。因此，它们可以作为完全开发的对等点集成到IP网络中，但它们需要节省状态内存、代码空间，并且通常需要协议和应用程序使用的功耗。
Class 2 devices are less constrained and fundamentally capable of supporting most of the same protocol stacks as used on notebooks or servers. However, even these devices can benefit from lightweight and energy-efficient protocols and from consuming less bandwidth. Furthermore, using fewer resources for networking leaves more resources available to applications. Thus, using the protocol stacks defined for more constrained devices on Class 2 devices might reduce development costs and increase the interoperability.
第2类设备受限制较少，基本上能够支持笔记本电脑或服务器上使用的大多数相同协议栈。然而，即使是这些设备也可以受益于轻量级和节能的协议以及消耗更少的带宽。此外，使用更少的资源进行联网会为应用程序提供更多的资源。因此，在第2类设备上使用为更受约束的设备定义的协议栈可能会降低开发成本并提高互操作性。
Constrained devices with capabilities significantly beyond Class 2 devices exist. They are less demanding from a standards development point of view as they can largely use existing protocols unchanged. The present document therefore does not make any attempt to define classes beyond Class 2. These devices can still be constrained by a limited energy supply.
存在功能远远超过2类设备的受限设备。从标准开发的角度来看，它们的要求较低，因为它们可以在很大程度上使用现有的协议。因此，本文件不试图定义第2类以外的类。这些设备仍然受到有限能源供应的限制。
With respect to examining the capabilities of constrained nodes, particularly for Class 1 devices, it is important to understand what type of applications they are able to run and which protocol mechanisms would be most suitable. Because of memory and other limitations, each specific Class 1 device might be able to support only a few selected functions needed for its intended operation. In other words, the set of functions that can actually be supported is not static per device type: devices with similar constraints might choose to support different functions. Even though Class 2 devices have some more functionality available and may be able to provide a more complete set of functions, they still need to be assessed for the type of applications they will be running and the protocol functions they would need. To be able to derive any requirements, the use cases and the involvement of the devices in the application and the operational scenario need to be analyzed. Use cases may combine constrained devices of multiple classes as well as more traditional Internet nodes.
关于检查受约束节点的能力，特别是对于1类设备，了解它们能够运行的应用程序类型以及最适合的协议机制非常重要。由于内存和其他限制，每个特定的1类设备可能只能支持其预期操作所需的几个选定功能。换句话说，实际上可以支持的功能集并不是每种设备类型都是静态的：具有类似约束的设备可能会选择支持不同的功能。尽管第2类设备具有更多的可用功能，并且可能能够提供更完整的功能集，但仍需要评估它们将运行的应用程序类型和所需的协议功能。为了能够导出任何需求，需要分析应用程序和操作场景中的用例和设备的参与情况。用例可以结合多个类别的受约束设备以及更传统的Internet节点。
Devices not only differ in their computing capabilities but also in available power and/or energy. While it is harder to find recognizable clusters in this space, it is still useful to introduce some common terminology.
设备不仅在计算能力上有所不同，而且在可用功率和/或能量上也有所不同。虽然在这个领域很难找到可识别的集群，但引入一些通用术语仍然很有用。
The power and/or energy available to a device may vastly differ, from kilowatts to microwatts, from essentially unlimited to hundreds of microjoules.
设备可用的功率和/或能量可能有很大的不同，从千瓦到微瓦，从基本上无限到数百微焦耳。
Instead of defining classes or clusters, we simply state, using the International System of Units (SI units), an approximate value for one or both of the quantities listed in Table 2:
我们没有定义类别或集群，而是使用国际单位制（SI单位）简单说明表2中列出的一个或两个数量的近似值：
+------+--------------------------------------------------+---------+
| Name | Definition | SI Unit |
+------+--------------------------------------------------+---------+
| Ps | Sustainable average power available for the | W |
| | device over the time it is functioning | (Watt) |
| | | |
| Et | Total electrical energy available before the | J |
| | energy source is exhausted | (Joule) |
+------+--------------------------------------------------+---------+
+------+--------------------------------------------------+---------+
| Name | Definition | SI Unit |
+------+--------------------------------------------------+---------+
| Ps | Sustainable average power available for the | W |
| | device over the time it is functioning | (Watt) |
| | | |
| Et | Total electrical energy available before the | J |
| | energy source is exhausted | (Joule) |
+------+--------------------------------------------------+---------+
Table 2: Quantities Relevant to Power and Energy
表2：与电力和能源相关的数量
The value of Et may need to be interpreted in conjunction with an indication over which period of time the value is given; see Section 4.2.
Et的值可能需要结合给出该值的时间段的指示来解释；见第4.2节。
Some devices enter a "low-power" mode before the energy available in a period is exhausted or even have multiple such steps on the way to exhaustion. For these devices, Ps would need to be given for each of the modes/steps.
一些设备在一段时间内的可用能量耗尽之前进入“低功率”模式，甚至在耗尽的过程中有多个这样的步骤。对于这些设备，需要为每个模式/步骤提供Ps。
As discussed above, some devices are limited in available energy as opposed to (or in addition to) being limited in available power. Where no relevant limitations exist with respect to energy, the device is classified as E9. The energy limitation may be in total energy available in the usable lifetime of the device (e.g., a device that is discarded when its non-replaceable primary battery is exhausted), classified as E2. Where the relevant limitation is for a specific period, the device is classified as E1, e.g., a solar-powered device with a limited amount of energy available for the night, a device that is manually connected to a charger and has a period of time between recharges, or a device with a periodic (primary) battery replacement interval. Finally, there may be a limited amount of energy available for a specific event, e.g., for a button press in an energy-harvesting light switch; such devices are classified as E0. Note that, in a sense, many E1 devices are also E2, as the rechargeable battery has a limited number of useful recharging cycles.
如上所述，一些设备在可用能量方面受到限制，而不是（或另外）在可用功率方面受到限制。在能量方面不存在相关限制的情况下，该装置被归类为E9。能量限制可以是设备（例如，当其不可更换的主电池耗尽时丢弃的设备）的可用寿命内的总可用能量，分类为E2。如果相关限制是针对特定时间段的，则该装置被分类为E1，例如，夜间可用能量有限的太阳能装置、手动连接至充电器且充电间隔时间较长的装置，或具有定期（主）电池更换间隔的装置。最后，可用于特定事件的能量有限，例如，用于能量收集灯开关中的按钮按下；此类装置被归类为E0。请注意，在某种意义上，许多E1设备也是E2设备，因为可充电电池的有用充电循环次数有限。
Table 3 provides a summary of the classifications described above.
表3概述了上述分类。
+------+------------------------------+-----------------------------+
| Name | Type of energy limitation | Example Power Source |
+------+------------------------------+-----------------------------+
| E0 | Event energy-limited | Event-based harvesting |
| | | |
| E1 | Period energy-limited | Battery that is |
| | | periodically recharged or |
| | | replaced |
| | | |
| E2 | Lifetime energy-limited | Non-replaceable primary |
| | | battery |
| | | |
| E9 | No direct quantitative | Mains-powered |
| | limitations to available | |
| | energy | |
+------+------------------------------+-----------------------------+
+------+------------------------------+-----------------------------+
| Name | Type of energy limitation | Example Power Source |
+------+------------------------------+-----------------------------+
| E0 | Event energy-limited | Event-based harvesting |
| | | |
| E1 | Period energy-limited | Battery that is |
| | | periodically recharged or |
| | | replaced |
| | | |
| E2 | Lifetime energy-limited | Non-replaceable primary |
| | | battery |
| | | |
| E9 | No direct quantitative | Mains-powered |
| | limitations to available | |
| | energy | |
+------+------------------------------+-----------------------------+
Table 3: Classes of Energy Limitation
表3：能源限制类别
Especially when wireless transmission is used, the radio often consumes a big portion of the total energy consumed by the device. Design parameters, such as the available spectrum, the desired range, and the bitrate aimed for, influence the power consumed during transmission and reception; the duration of transmission and reception (including potential reception) influence the total energy consumption.
特别是当使用无线传输时，无线电通常消耗设备消耗的总能量的很大一部分。设计参数，如可用频谱、所需范围和目标比特率，影响传输和接收期间的功耗；传输和接收的持续时间（包括潜在接收）影响总能耗。
Different strategies for power usage and network attachment may be used, based on the type of the energy source (e.g., battery or mains-powered) and the frequency with which a device needs to communicate.
根据能源类型（例如，电池或电源供电）和设备需要通信的频率，可以使用不同的电源使用和网络连接策略。
The general strategies for power usage can be described as follows:
用电的一般策略可描述如下：
Always-on: This strategy is most applicable if there is no reason for extreme measures for power saving. The device can stay on in the usual manner all the time. It may be useful to employ power-friendly hardware or limit the number of wireless transmissions, CPU speeds, and other aspects for general power-saving and cooling needs, but the device can be connected to the network all the time.
始终开启：如果没有理由采取极端节能措施，则此策略最适用。该设备可以以通常的方式一直保持打开状态。使用电源友好型硬件或限制无线传输的数量、CPU速度和其他方面对于一般的节能和冷却需求可能是有用的，但是设备可以一直连接到网络。
Normally-off: Under this strategy, the device sleeps such long periods at a time that once it wakes up, it makes sense for it to not pretend that it has been connected to the network during
正常关闭：在这种策略下，设备一次睡眠的时间非常长，一旦醒来，就可以不假装在睡眠期间已连接到网络
sleep: the device reattaches to the network as it is woken up. The main optimization goal is to minimize the effort during the reattachment process and any resulting application communications.
睡眠：设备在唤醒时重新连接到网络。主要的优化目标是最小化重新连接过程中的工作量以及由此产生的任何应用程序通信。
If the device sleeps for long periods of time and needs to communicate infrequently, the relative increase in energy expenditure during reattachment may be acceptable.
如果设备长时间睡眠且需要不频繁通信，则可接受重新连接期间能量消耗的相对增加。
Low-power: This strategy is most applicable to devices that need to operate on a very small amount of power but still need to be able to communicate on a relatively frequent basis. This implies that extremely low-power solutions need to be used for the hardware, chosen link-layer mechanisms, and so on. Typically, given the small amount of time between transmissions, despite their sleep state, these devices retain some form of attachment to the network. Techniques used for minimizing power usage for the network communications include minimizing any work from re-establishing communications after waking up and tuning the frequency of communications (including "duty cycling", where components are switched on and off in a regular cycle) and other parameters appropriately.
低功耗：此策略最适用于需要在非常小的功率下运行，但仍需要能够在相对频繁的基础上进行通信的设备。这意味着硬件、所选链路层机制等需要使用极低功耗的解决方案。通常，考虑到传输之间的时间间隔很短，尽管处于睡眠状态，这些设备仍保留某种形式的网络连接。用于最小化网络通信的功率使用的技术包括最小化在唤醒和调谐通信频率（包括“占空比”，其中组件在常规周期中打开和关闭）和其他参数后重新建立通信的任何工作。
Table 4 provides a summary of the strategies described above.
表4概述了上述战略。
+------+--------------+---------------------------------------------+
| Name | Strategy | Ability to communicate |
+------+--------------+---------------------------------------------+
| P0 | Normally-off | Reattach when required |
| | | |
| P1 | Low-power | Appears connected, perhaps with high |
| | | latency |
| | | |
| P9 | Always-on | Always connected |
+------+--------------+---------------------------------------------+
+------+--------------+---------------------------------------------+
| Name | Strategy | Ability to communicate |
+------+--------------+---------------------------------------------+
| P0 | Normally-off | Reattach when required |
| | | |
| P1 | Low-power | Appears connected, perhaps with high |
| | | latency |
| | | |
| P9 | Always-on | Always connected |
+------+--------------+---------------------------------------------+
Table 4: Strategies of Using Power for Communication
表4：使用电源进行通信的策略
Note that the discussion above is at the device level; similar considerations can apply at the communications-interface level. This document does not define terminology for the latter.
注意，上面的讨论是在设备级别上进行的；类似的注意事项可应用于通信接口级别。本文件未定义后者的术语。
A term often used to describe power-saving approaches is "duty-cycling". This describes all forms of periodically switching off some function, leaving it on only for a certain percentage of time (the "duty cycle").
常用于描述节能方法的术语是“工作循环”。这描述了周期性关闭某些功能的所有形式，仅在一定百分比的时间内保持打开状态（“占空比”）。
[RFC7102] only distinguishes two levels, defining a Non-Sleepy Node as a node that always remains in a fully powered-on state (always awake) where it has the capability to perform communication (P9) and a Sleepy Node as a node that may sometimes go into a sleep mode (a low-power state to conserve power) and temporarily suspend protocol communication (P0); there is no explicit mention of P1.
[RFC7102]仅区分两个级别，将非休眠节点定义为始终保持完全通电状态（始终处于唤醒状态）的节点，其中它具有执行通信的能力（第9页），将休眠节点定义为有时可能进入休眠模式（低功率状态以节省电源）的节点暂停协议通信（P0）；没有明确提到P1。
This document introduces common terminology that does not raise any new security issues. Security considerations arising from the constraints discussed in this document need to be discussed in the context of specific protocols. For instance, Section 11.6 of [COAP], "Constrained node considerations", discusses implications of specific constraints on the security mechanisms employed. [ROLL-SEC-THREATS] provides a security threat analysis for the RPL routing protocol. Implementation considerations for security protocols on constrained nodes are discussed in [IKEV2-MINIMAL] and [TLS-MINIMAL]. A wider view of security in constrained-node networks is provided in [IOT-SECURITY].
本文档介绍了不会引起任何新安全问题的通用术语。本文件中讨论的约束引起的安全注意事项需要在特定协议的上下文中讨论。例如，[COAP]第11.6节“受约束的节点注意事项”讨论了特定约束对所采用安全机制的影响。[ROLL-SEC-THREATS]为RPL路由协议提供安全威胁分析。[IKEV2-MINIMAL]和[TLS-MINIMAL]中讨论了受约束节点上安全协议的实现注意事项。[IOT-security]提供了受约束节点网络中更广泛的安全视图。
Dominique Barthel and Peter van der Stok provided useful comments; Charles Palmer provided a full editorial review.
多米尼克·巴塞尔和彼得·范德斯托克提供了有用的评论；查尔斯·帕尔默提供了完整的编辑评论。
Peter van der Stok insisted that we should include power terminology, hence Section 4. The text for Section 4.3 is mostly lifted from a previous version of [COAP-CELLULAR] and has been adapted for this document.
彼得·范德斯托克（Peter van der Stok）坚持认为我们应该包括权力术语，因此第4节。第4.3节的文本主要摘自[COAP-CELLULAR]的早期版本，并已针对本文件进行了修改。
[COAP] Shelby, Z., Hartke, K., and C. Bormann, "Constrained Application Protocol (CoAP)", Work in Progress, June 2013.
[COAP]Shelby，Z.，Hartke，K.，和C.Bormann，“受限应用协议（COAP）”，正在进行的工作，2013年6月。
[COAP-CELLULAR] Arkko, J., Eriksson, A., and A. Keranen, "Building Power-Efficient CoAP Devices for Cellular Networks", Work in Progress, February 2014.
[COAP-CELLULAR]Arkko，J.，Eriksson，A.，和A.Keranen，“为蜂窝网络构建节能的COAP设备”，正在进行的工作，2014年2月。
[FALL] Fall, K., "A Delay-Tolerant Network Architecture for Challenged Internets", SIGCOMM 2003, 2003.
[FALL]FALL，K.，“挑战互联网的延迟容忍网络架构”，SIGCOMM 2003，2003年。
[FIFTY-BILLION] Ericsson, "More Than 50 Billion Connected Devices", Ericsson White Paper 284 23-3149 Uen, February 2011, <http://www.ericsson.com/res/docs/whitepapers/ wp-50-billions.pdf>.
[500亿]爱立信，“超过500亿连接设备”，爱立信白皮书284 23-3149 Uen，2011年2月<http://www.ericsson.com/res/docs/whitepapers/ wp-500-10.pdf>。
[IKEV2-MINIMAL] Kivinen, T., "Minimal IKEv2", Work in Progress, October 2013.
[IKEV2-MINIMAL]Kivinen，T.，“MINIMAL IKEV2”，在建工程，2013年10月。
[IOT-SECURITY] Garcia-Morchon, O., Kumar, S., Keoh, S., Hummen, R., and R. Struik, "Security Considerations in the IP-based Internet of Things", Work in Progress, September 2013.
[物联网安全]加西亚·莫尔肯，O.，库马尔，S.，基奥，S.，胡曼，R.，和R.斯特鲁克，“基于IP的物联网中的安全考虑”，正在进行的工作，2013年9月。
[ISQ-13] International Electrotechnical Commission, "International Standard -- Quantities and units -- Part 13: Information science and technology", IEC 80000-13, March 2008.
[ISQ-13]国际电工委员会，“国际标准——数量和单位——第13部分：信息科学与技术”，IEC 80000-132008年3月。
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981.
[RFC0793]Postel，J.，“传输控制协议”，标准7，RFC 793，1981年9月。
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, April 2007.
[RFC4838]Cerf，V.，Burleigh，S.，Hooke，A.，Torgerson，L.，Durst，R.，Scott，K.，Fall，K.，和H.Weiss，“延迟容忍网络架构”，RFC 48382007年4月。
[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.
[RFC4919]Kushalnagar，N.，黑山，G.，和C.Schumacher，“低功率无线个人区域网络（6LoWPANs）上的IPv6：概述，假设，问题陈述和目标”，RFC 4919，2007年8月。
[RFC6550] Winter, T., Thubert, P., 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.
[RFC6550]温特，T.，苏伯特，P.，勃兰特，A.，许，J.，凯尔西，R.，列维斯，P.，皮斯特，K.，斯特鲁克，R.，瓦塞尔，JP.，和R.亚历山大，“RPL：低功耗和有损网络的IPv6路由协议”，RFC 65502012年3月。
[RFC6551] Vasseur, JP., Kim, M., Pister, K., Dejean, N., and D. Barthel, "Routing Metrics Used for Path Calculation in Low-Power and Lossy Networks", RFC 6551, March 2012.
[RFC6551]Vasseur，JP.，Kim，M.，Pister，K.，Dejean，N.，和D.Barthel，“低功率和有损网络中用于路径计算的路由度量”，RFC 65512012年3月。
[RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem Statement and Requirements for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing", RFC 6606, May 2012.
[RFC6606]Kim，E.，Kaspar，D.，Gomez，C.，和C.Bormann，“通过低功率无线个人区域网络（6LoWPAN）路由的IPv6问题陈述和要求”，RFC 6606，2012年5月。
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and Lossy Networks", RFC 7102, January 2014.
[RFC7102]Vasseur，JP.，“低功耗和有损网络路由中使用的术语”，RFC 7102，2014年1月。
[ROLL-SEC-THREATS] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., and M. Richardson, "A Security Threat Analysis for Routing Protocol for Low-power and lossy networks (RPL)", Work in Progress, December 2013.
[ROLL-SEC-THREATS]Tsao，T.，Alexander，R.，Dohler，M.，Daza，V.，Lozano，A.，和M.Richardson，“低功耗和有损网络路由协议（RPL）的安全威胁分析”，正在进行中，2013年12月。
[RPL-DEPLOYMENT] Vasseur, J., Ed., Hui, J., Ed., Dasgupta, S., and G. Yoon, "RPL deployment experience in large scale networks", Work in Progress, July 2012.
[RPL-部署]Vasseur，J.，Ed.，Hui，J.，Ed.，Dasgupta，S.，和G.Yoon，“大规模网络中的RPL部署经验”，正在进行的工作，2012年7月。
[TLS-MINIMAL] Kumar, S., Keoh, S., and H. Tschofenig, "A Hitchhiker's Guide to the (Datagram) Transport Layer Security Protocol for Smart Objects and Constrained Node Networks", Work in Progress, March 2014.
[TLS-MINIMAL]Kumar，S.，Keoh，S.，和H.Tschofenig，“智能对象和受约束节点网络（数据报）传输层安全协议的搭便车指南”，正在进行的工作，2014年3月。
[V6-BTLE] Nieminen, J., Ed., Savolainen, T., Ed., Isomaki, M., Patil, B., Shelby, Z., and C. Gomez, "Transmission of IPv6 Packets over BLUETOOTH Low Energy", Work in Progress, May 2014.
[V6-BTLE]Nieminen，J.，Ed.，Savolainen，T.，Ed.，Isomaki，M.，Patil，B.，Shelby，Z.，和C.Gomez，“通过蓝牙低能量传输IPv6数据包”，正在进行的工作，2014年5月。
[V6-DECT-ULE] Mariager, P., Ed., Petersen, J., and Z. Shelby, "Transmission of IPv6 Packets over DECT Ultra Low Energy", Work in Progress, July 2013.
[V6-DECT-ULE]Mariager，P.，Ed.，Petersen，J.，和Z.Shelby，“通过DECT超低能量传输IPv6数据包”，正在进行的工作，2013年7月。
[V6-G9959] Brandt, A. and J. Buron, "Transmission of IPv6 packets over ITU-T G.9959 Networks", Work in Progress, May 2014.
[V6-G9959]Brandt，A.和J.Buron，“通过ITU-T G.9959网络传输IPv6数据包”，正在进行的工作，2014年5月。
[WEI] Shelby, Z. and C. Bormann, "6LoWPAN: the Wireless Embedded Internet", ISBN 9780470747995, 2009.
[WEI]Shelby，Z.和C.Bormann，“6LoWPAN：无线嵌入式互联网”，ISBN 97804707479952009。
Authors' Addresses
作者地址
Carsten Bormann Universitaet Bremen TZI Postfach 330440 D-28359 Bremen Germany
德国不来梅卡斯滕·鲍曼大学邮政学院330440 D-28359
Phone: +49-421-218-63921
EMail: cabo@tzi.org
Phone: +49-421-218-63921
EMail: cabo@tzi.org
Mehmet Ersue Nokia Solutions and Networks St.-Martinstrasse 76 81541 Munich Germany
Mehmet Ersue诺基亚解决方案和网络德国慕尼黑圣马丁大街76 81541号
Phone: +49 172 8432301
EMail: mehmet.ersue@nsn.com
Phone: +49 172 8432301
EMail: mehmet.ersue@nsn.com
Ari Keranen Ericsson Hirsalantie 11 02420 Jorvas Finland
Ari Keranen Ericsson Hirsalantie 11 02420 Jorvas Finland
EMail: ari.keranen@ericsson.com
EMail: ari.keranen@ericsson.com