Internet Engineering Task Force (IETF) G. Fioccola, Ed.
Request for Comments: 8321 A. Capello
Category: Experimental M. Cociglio
ISSN: 2070-1721 L. Castaldelli
Telecom Italia
M. Chen
L. Zheng
Huawei Technologies
G. Mirsky
ZTE
T. Mizrahi
Marvell
January 2018
Internet Engineering Task Force (IETF) G. Fioccola, Ed.
Request for Comments: 8321 A. Capello
Category: Experimental M. Cociglio
ISSN: 2070-1721 L. Castaldelli
Telecom Italia
M. Chen
L. Zheng
Huawei Technologies
G. Mirsky
ZTE
T. Mizrahi
Marvell
January 2018
Alternate-Marking Method for Passive and Hybrid Performance Monitoring
被动和混合性能监测的替代标记方法
Abstract
摘要
This document describes a method to perform packet loss, delay, and jitter measurements on live traffic. This method is based on an Alternate-Marking (coloring) technique. A report is provided in order to explain an example and show the method applicability. This technology can be applied in various situations, as detailed in this document, and could be considered Passive or Hybrid depending on the application.
本文档描述了对实时流量执行数据包丢失、延迟和抖动测量的方法。此方法基于交替标记（着色）技术。为了解释一个例子并说明方法的适用性，提供了一份报告。如本文件所述，该技术可应用于各种情况，根据应用情况可被视为被动或混合。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.
本文件不是互联网标准跟踪规范；它是为检查、实验实施和评估而发布的。
This document defines an Experimental Protocol for the Internet community. 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 7841.
本文档为互联网社区定义了一个实验协议。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 7841第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8321.
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https://www.rfc-editor.org/info/rfc8321.
Copyright Notice
版权公告
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2018 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 (https://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(https://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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Overview of the Method . . . . . . . . . . . . . . . . . . . 5
3. Detailed Description of the Method . . . . . . . . . . . . . 6
3.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 6
3.1.1. Coloring the Packets . . . . . . . . . . . . . . . . 11
3.1.2. Counting the Packets . . . . . . . . . . . . . . . . 12
3.1.3. Collecting Data and Calculating Packet Loss . . . . . 13
3.2. Timing Aspects . . . . . . . . . . . . . . . . . . . . . 13
3.3. One-Way Delay Measurement . . . . . . . . . . . . . . . . 15
3.3.1. Single-Marking Methodology . . . . . . . . . . . . . 15
3.3.2. Double-Marking Methodology . . . . . . . . . . . . . 17
3.4. Delay Variation Measurement . . . . . . . . . . . . . . . 18
4. Considerations . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Synchronization . . . . . . . . . . . . . . . . . . . . . 19
4.2. Data Correlation . . . . . . . . . . . . . . . . . . . . 19
4.3. Packet Reordering . . . . . . . . . . . . . . . . . . . . 20
5. Applications, Implementation, and Deployment . . . . . . . . 21
5.1. Report on the Operational Experiment . . . . . . . . . . 22
5.1.1. Metric Transparency . . . . . . . . . . . . . . . . . 24
6. Hybrid Measurement . . . . . . . . . . . . . . . . . . . . . 24
7. Compliance with Guidelines from RFC 6390 . . . . . . . . . . 25
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
9. Security Considerations . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1. Normative References . . . . . . . . . . . . . . . . . . 28
10.2. Informative References . . . . . . . . . . . . . . . . . 29
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Overview of the Method . . . . . . . . . . . . . . . . . . . 5
3. Detailed Description of the Method . . . . . . . . . . . . . 6
3.1. Packet Loss Measurement . . . . . . . . . . . . . . . . . 6
3.1.1. Coloring the Packets . . . . . . . . . . . . . . . . 11
3.1.2. Counting the Packets . . . . . . . . . . . . . . . . 12
3.1.3. Collecting Data and Calculating Packet Loss . . . . . 13
3.2. Timing Aspects . . . . . . . . . . . . . . . . . . . . . 13
3.3. One-Way Delay Measurement . . . . . . . . . . . . . . . . 15
3.3.1. Single-Marking Methodology . . . . . . . . . . . . . 15
3.3.2. Double-Marking Methodology . . . . . . . . . . . . . 17
3.4. Delay Variation Measurement . . . . . . . . . . . . . . . 18
4. Considerations . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Synchronization . . . . . . . . . . . . . . . . . . . . . 19
4.2. Data Correlation . . . . . . . . . . . . . . . . . . . . 19
4.3. Packet Reordering . . . . . . . . . . . . . . . . . . . . 20
5. Applications, Implementation, and Deployment . . . . . . . . 21
5.1. Report on the Operational Experiment . . . . . . . . . . 22
5.1.1. Metric Transparency . . . . . . . . . . . . . . . . . 24
6. Hybrid Measurement . . . . . . . . . . . . . . . . . . . . . 24
7. Compliance with Guidelines from RFC 6390 . . . . . . . . . . 25
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
9. Security Considerations . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1. Normative References . . . . . . . . . . . . . . . . . . 28
10.2. Informative References . . . . . . . . . . . . . . . . . 29
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
Nowadays, most Service Providers' networks carry traffic with contents that are highly sensitive to packet loss [RFC7680], delay [RFC7679], and jitter [RFC3393].
如今，大多数服务提供商的网络承载的内容对数据包丢失[RFC7680]、延迟[RFC7679]和抖动[RFC3393]高度敏感。
In view of this scenario, Service Providers need methodologies and tools to monitor and measure network performance with an adequate accuracy, in order to constantly control the quality of experience perceived by their customers. On the other hand, performance monitoring provides useful information for improving network management (e.g., isolation of network problems, troubleshooting, etc.).
鉴于这种情况，服务提供商需要方法和工具以足够的准确性监控和测量网络性能，以便不断控制其客户感知的体验质量。另一方面，性能监视为改进网络管理提供了有用的信息（例如，隔离网络问题、排除故障等）。
A lot of work related to Operations, Administration, and Maintenance (OAM), which also includes performance monitoring techniques, has been done by Standards Developing Organizations (SDOs): [RFC7276] provides a good overview of existing OAM mechanisms defined in the IETF, ITU-T, and IEEE. In the IETF, a lot of work has been done on fault detection and connectivity verification, while a minor effort has been thus far dedicated to performance monitoring. The IPPM WG has defined standard metrics to measure network performance; however, the methods developed in this WG mainly refer to focus on Active measurement techniques. More recently, the MPLS WG has defined mechanisms for measuring packet loss, one-way and two-way delay, and delay variation in MPLS networks [RFC6374], but their applicability to Passive measurements has some limitations, especially for pure connection-less networks.
标准开发组织（SDO）已经完成了大量与操作、管理和维护（OAM）相关的工作，其中还包括性能监控技术：[RFC7276]提供了IETF、ITU-T和IEEE中定义的现有OAM机制的良好概述。在IETF中，在故障检测和连接性验证方面做了大量工作，而到目前为止，在性能监控方面只做了少量工作。IPPM工作组定义了衡量网络性能的标准指标；然而，本工作组开发的方法主要涉及主动测量技术。最近，MPLS WG定义了用于测量MPLS网络中的数据包丢失、单向和双向延迟以及延迟变化的机制[RFC6374]，但它们对被动测量的适用性有一些限制，特别是对于纯无连接网络。
The lack of adequate tools to measure packet loss with the desired accuracy drove an effort to design a new method for the performance monitoring of live traffic, which is easy to implement and deploy. The effort led to the method described in this document: basically, it is a Passive performance monitoring technique, potentially applicable to any kind of packet-based traffic, including Ethernet, IP, and MPLS, both unicast and multicast. The method addresses primarily packet loss measurement, but it can be easily extended to one-way or two-way delay and delay variation measurements as well.
由于缺乏足够的工具来准确测量数据包丢失，因此需要设计一种新的实时流量性能监控方法，该方法易于实现和部署。这一努力导致了本文中描述的方法：基本上，它是一种被动性能监控技术，可能适用于任何类型的基于数据包的流量，包括以太网、IP和MPLS，包括单播和多播。该方法主要解决数据包丢失测量，但也可以很容易地扩展到单向或双向延迟以及延迟变化测量。
The method has been explicitly designed for Passive measurements, but it can also be used with Active probes. Passive measurements are usually more easily understood by customers and provide much better accuracy, especially for packet loss measurements.
该方法已明确设计用于被动测量，但也可用于主动探头。被动测量通常更容易被客户理解，并提供更好的准确性，尤其是对于数据包丢失测量。
RFC 7799 [RFC7799] defines Passive and Hybrid Methods of Measurement. In particular, Passive Methods of Measurement are based solely on observations of an undisturbed and unmodified packet stream of interest; Hybrid Methods are Methods of Measurement that use a combination of Active Methods and Passive Methods.
RFC 7799[RFC7799]定义了被动和混合测量方法。具体而言，被动测量方法仅基于对未受干扰且未经修改的感兴趣分组流的观察；混合方法是使用主动方法和被动方法相结合的测量方法。
Taking into consideration these definitions, the Alternate-Marking Method could be considered Hybrid or Passive, depending on the case. In the case where the marking method is obtained by changing existing field values of the packets (e.g., the Differentiated Services Code Point (DSCP) field), the technique is Hybrid. In the case where the marking field is dedicated, reserved, and included in the protocol specification, the Alternate-Marking technique can be considered as Passive (e.g., Synonymous Flow Label as described in [SFL-FRAMEWORK] or OAM Marking Bits as described in [PM-MM-BIER]).
考虑到这些定义，可根据具体情况将替代标记方法视为混合或被动标记方法。在通过改变分组的现有字段值（例如，区分服务码点（DSCP）字段）来获得标记方法的情况下，该技术是混合的。在标记字段专用、保留并包含在协议规范中的情况下，可将替代标记技术视为被动标记（例如，[SFL-FRAMEWORK]中所述的同义流标签或[PM-MM-BIER]中所述的OAM标记位）。
The advantages of the method described in this document are:
本文件中所述方法的优点是：
o easy implementation: it can be implemented by using features already available on major routing platforms, as described in Section 5.1, or by applying an optimized implementation of the method for both legacy and newest technologies;
o 易于实施：如第5.1节所述，它可以通过使用主要路由平台上已有的功能来实施，或者通过对传统和最新技术应用该方法的优化实施来实施；
o low computational effort: the additional load on processing is negligible;
o 计算工作量低：处理上的额外负载可以忽略不计；
o accurate packet loss measurement: single packet loss granularity is achieved with a Passive measurement;
o 准确的丢包测量：通过被动测量实现单个丢包粒度；
o potential applicability to any kind of packet-based or frame-based traffic: Ethernet, IP, MPLS, etc., and both unicast and multicast;
o 潜在适用于任何类型的基于分组或基于帧的流量：以太网、IP、MPLS等，以及单播和多播；
o robustness: the method can tolerate out-of-order packets, and it's not based on "special" packets whose loss could have a negative impact;
o 鲁棒性：该方法可以容忍无序数据包，并且它不基于丢失可能产生负面影响的“特殊”数据包；
o flexibility: all the timestamp formats are allowed, because they are managed out of band. The format (the Network Time Protocol (NTP) [RFC5905] or the IEEE 1588 Precision Time Protocol (PTP) [IEEE-1588]) depends on the precision you want; and
o 灵活性：所有时间戳格式都是允许的，因为它们是带外管理的。格式（网络时间协议（NTP）[RFC5905]或IEEE 1588精确时间协议（PTP）[IEEE-1588]）取决于所需的精度；和
o no interoperability issues: the features required to experiment and test the method (as described in Section 5.1) are available on all current routing platforms. Both a centralized or distributed solution can be used to harvest data from the routers.
o 无互操作性问题：试验和测试方法所需的功能（如第5.1节所述）在所有当前路由平台上都可用。集中式或分布式解决方案均可用于从路由器获取数据。
The method doesn't raise any specific need for protocol extension, but it could be further improved by means of some extension to existing protocols. Specifically, the use of Diffserv bits for coloring the packets could not be a viable solution in some cases: a standard method to color the packets for this specific application could be beneficial.
该方法没有提出任何特定的协议扩展需求，但可以通过对现有协议进行一些扩展来进一步改进。具体地说，在某些情况下，使用Diffserv位为数据包着色可能不是一个可行的解决方案：为这个特定应用程序为数据包着色的标准方法可能是有益的。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”在所有大写字母出现时（如图所示）应按照BCP 14[RFC2119][RFC8174]所述进行解释。
In order to perform packet loss measurements on a production traffic flow, different approaches exist. The most intuitive one consists in numbering the packets so that each router that receives the flow can immediately detect a packet that is missing. This approach, though very simple in theory, is not simple to achieve: it requires the insertion of a sequence number into each packet, and the devices must be able to extract the number and check it in real time. Such a task can be difficult to implement on live traffic: if UDP is used as the transport protocol, the sequence number is not available; on the other hand, if a higher-layer sequence number (e.g., in the RTP header) is used, extracting that information from each packet and processing it in real time could overload the device.
为了对生产业务流执行分组丢失测量，存在不同的方法。最直观的方法是对数据包进行编号，以便接收数据流的每个路由器都能立即检测到丢失的数据包。这种方法虽然理论上非常简单，但实现起来并不简单：它需要在每个数据包中插入一个序列号，并且设备必须能够提取序列号并实时检查。这样的任务很难在实时流量上实现：如果使用UDP作为传输协议，则序列号不可用；另一方面，如果使用更高的层序列号（例如，在RTP报头中），则从每个分组中提取该信息并实时处理它可能使设备过载。
An alternate approach is to count the number of packets sent on one end, count the number of packets received on the other end, and compare the two values. This operation is much simpler to implement, but it requires the devices performing the measurement to be in sync: in order to compare two counters, it is required that they refer exactly to the same set of packets. Since a flow is continuous and cannot be stopped when a counter has to be read, it can be difficult to determine exactly when to read the counter. A possible solution to overcome this problem is to virtually split the flow in consecutive blocks by periodically inserting a delimiter so that each counter refers exactly to the same block of packets. The delimiter could be, for example, a special packet inserted artificially into the flow. However, delimiting the flow using specific packets has some limitations. First, it requires generating additional packets within the flow and requires the equipment to be able to process those packets. In addition, the method is vulnerable to out-of-order reception of delimiting packets and, to a lesser extent, to their loss.
另一种方法是计算一端发送的数据包数量，计算另一端接收的数据包数量，并比较这两个值。此操作的实现要简单得多，但它要求执行测量的设备保持同步：为了比较两个计数器，要求它们完全引用同一组数据包。由于流是连续的，并且在必须读取计数器时无法停止，因此很难准确确定何时读取计数器。克服这个问题的一个可能的解决方案是，通过周期性地插入分隔符，将流虚拟地分割成连续的块，以便每个计数器都精确地引用相同的数据包块。例如，分隔符可以是人工插入流中的特殊数据包。但是，使用特定的数据包来划分流有一些限制。首先，它要求在流中生成额外的数据包，并要求设备能够处理这些数据包。此外，该方法容易受到定界分组的无序接收的影响，并且在较小程度上容易受到分组丢失的影响。
The method proposed in this document follows the second approach, but it doesn't use additional packets to virtually split the flow in blocks. Instead, it "marks" the packets so that the packets belonging to the same block will have the same color, whilst consecutive blocks will have different colors. Each change of color represents a sort of auto-synchronization signal that guarantees the consistency of measurements taken by different devices along the path (see also [IP-MULTICAST-PM] and [OPSAWG-P3M], where this technique was introduced).
本文中提出的方法遵循第二种方法，但它不使用额外的数据包来虚拟地将流分块。相反，它“标记”数据包，以便属于同一块的数据包将具有相同的颜色，而连续的数据块将具有不同的颜色。每一种颜色的变化都代表一种自动同步信号，保证不同设备沿路径进行测量的一致性（另请参见[IP-MULTICAST-PM]和[OPSAWG-P3M]，其中引入了该技术）。
Figure 1 represents a very simple network and shows how the method can be used to measure packet loss on different network segments: by enabling the measurement on several interfaces along the path, it is possible to perform link monitoring, node monitoring, or end-to-end monitoring. The method is flexible enough to measure packet loss on any segment of the network and can be used to isolate the faulty element.
图1显示了一个非常简单的网络，并显示了如何使用该方法测量不同网段上的数据包丢失：通过在路径上的几个接口上启用测量，可以执行链路监视、节点监视或端到端监视。该方法具有足够的灵活性，可以测量网络任何部分上的数据包丢失，并可用于隔离故障元件。
Traffic Flow
========================================================>
+------+ +------+ +------+ +------+
---<> R1 <>-----<> R2 <>-----<> R3 <>-----<> R4 <>---
+------+ +------+ +------+ +------+
. . . . . .
. . . . . .
. <------> <-------> .
. Node Packet Loss Link Packet Loss .
. .
<--------------------------------------------------->
End-to-End Packet Loss
Traffic Flow
========================================================>
+------+ +------+ +------+ +------+
---<> R1 <>-----<> R2 <>-----<> R3 <>-----<> R4 <>---
+------+ +------+ +------+ +------+
. . . . . .
. . . . . .
. <------> <-------> .
. Node Packet Loss Link Packet Loss .
. .
<--------------------------------------------------->
End-to-End Packet Loss
Figure 1: Available Measurements
图1：可用测量值
This section describes, in detail, how the method operates. A special emphasis is given to the measurement of packet loss, which represents the core application of the method, but applicability to delay and jitter measurements is also considered.
本节详细描述了该方法的操作方式。特别强调了包丢失的测量，它代表了该方法的核心应用，但也考虑了延迟和抖动测量的适用性。
The basic idea is to virtually split traffic flows into consecutive blocks: each block represents a measurable entity unambiguously recognizable by all network devices along the path. By counting the number of packets in each block and comparing the values measured by different network devices along the path, it is possible to measure packet loss occurred in any single block between any two points.
其基本思想是将业务流虚拟地分割成连续的块：每个块表示一个可测量的实体，该实体可由路径上的所有网络设备明确识别。通过计算每个块中的数据包数量并比较路径上不同网络设备测量的值，可以测量任意两点之间任何单个块中发生的数据包丢失。
As discussed in the previous section, a simple way to create the blocks is to "color" the traffic (two colors are sufficient), so that packets belonging to different consecutive blocks will have different colors. Whenever the color changes, the previous block terminates and the new one begins. Hence, all the packets belonging to the same block will have the same color and packets of different consecutive blocks will have different colors. The number of packets in each block depends on the criterion used to create the blocks:
如前一节所讨论的，创建块的一种简单方法是“着色”流量（两种颜色就足够了），这样属于不同连续块的数据包将具有不同的颜色。每当颜色改变时，上一个块终止，新块开始。因此，属于同一块的所有分组将具有相同的颜色，并且不同连续块的分组将具有不同的颜色。每个块中的数据包数量取决于用于创建块的标准：
o if the color is switched after a fixed number of packets, then each block will contain the same number of packets (except for any losses); and
o 如果在固定数量的包之后切换颜色，则每个块将包含相同数量的包（任何丢失除外）；和
o if the color is switched according to a fixed timer, then the number of packets may be different in each block depending on the packet rate.
o 如果根据固定计时器切换颜色，则根据分组速率，每个块中的分组数量可能不同。
The following figure shows how a flow looks like when it is split in traffic blocks with colored packets.
下图显示了流在使用彩色数据包拆分为流量块时的外观。
A: packet with A coloring B: packet with B coloring
A:有颜色的包B:有颜色的包
| | | | |
| | Traffic Flow | |
------------------------------------------------------------------->
BBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAA
------------------------------------------------------------------->
... | Block 5 | Block 4 | Block 3 | Block 2 | Block 1
| | | | |
| | | | |
| | Traffic Flow | |
------------------------------------------------------------------->
BBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAA
------------------------------------------------------------------->
... | Block 5 | Block 4 | Block 3 | Block 2 | Block 1
| | | | |
Figure 2: Traffic Coloring
图2：交通着色
Figure 3 shows how the method can be used to measure link packet loss between two adjacent nodes.
图3显示了该方法如何用于测量两个相邻节点之间的链路数据包丢失。
Referring to the figure, let's assume we want to monitor the packet loss on the link between two routers: router R1 and router R2. According to the method, the traffic is colored alternatively with two different colors: A and B. Whenever the color changes, the transition generates a sort of square-wave signal, as depicted in the following figure.
参考图，假设我们想要监控两个路由器之间链路上的数据包丢失：路由器R1和路由器R2。根据该方法，交通用两种不同的颜色交替着色：A和B。每当颜色改变时，转换产生一种方波信号，如下图所示。
Color A ----------+ +-----------+ +----------
| | | |
Color B +-----------+ +-----------+
Block n ... Block 3 Block 2 Block 1
<---------> <---------> <---------> <---------> <--------->
Color A ----------+ +-----------+ +----------
| | | |
Color B +-----------+ +-----------+
Block n ... Block 3 Block 2 Block 1
<---------> <---------> <---------> <---------> <--------->
Traffic Flow
===========================================================>
Color ...AAAAAAAAAAA BBBBBBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAA...
===========================================================>
Traffic Flow
===========================================================>
Color ...AAAAAAAAAAA BBBBBBBBBBB AAAAAAAAAAA BBBBBBBBBBB AAAAAAA...
===========================================================>
Figure 3: Computation of Link Packet Loss
图3：链路分组丢失的计算
Traffic coloring can be done by R1 itself if the traffic is not already colored. R1 needs two counters, C(A)R1 and C(B)R1, on its egress interface: C(A)R1 counts the packets with color A and C(B)R1 counts those with color B. As long as traffic is colored as A, only counter C(A)R1 will be incremented, while C(B)R1 is not incremented; conversely, when the traffic is colored as B, only C(B)R1 is incremented. C(A)R1 and C(B)R1 can be used as reference values to determine the packet loss from R1 to any other measurement point down the path. Router R2, similarly, will need two counters on its ingress interface, C(A)R2 and C(B)R2, to count the packets received on that interface and colored with A and B, respectively. When an A block ends, it is possible to compare C(A)R1 and C(A)R2 and calculate the packet loss within the block; similarly, when the successive B block terminates, it is possible to compare C(B)R1 with C(B)R2, and so on, for every successive block.
Traffic coloring can be done by R1 itself if the traffic is not already colored. R1 needs two counters, C(A)R1 and C(B)R1, on its egress interface: C(A)R1 counts the packets with color A and C(B)R1 counts those with color B. As long as traffic is colored as A, only counter C(A)R1 will be incremented, while C(B)R1 is not incremented; conversely, when the traffic is colored as B, only C(B)R1 is incremented. C(A)R1 and C(B)R1 can be used as reference values to determine the packet loss from R1 to any other measurement point down the path. Router R2, similarly, will need two counters on its ingress interface, C(A)R2 and C(B)R2, to count the packets received on that interface and colored with A and B, respectively. When an A block ends, it is possible to compare C(A)R1 and C(A)R2 and calculate the packet loss within the block; similarly, when the successive B block terminates, it is possible to compare C(B)R1 with C(B)R2, and so on, for every successive block.translate error, please retry
Likewise, by using two counters on the R2 egress interface, it is possible to count the packets sent out of the R2 interface and use them as reference values to calculate the packet loss from R2 to any measurement point down R2.
同样，通过使用R2出口接口上的两个计数器，可以对从R2接口发送的数据包进行计数，并将其用作参考值，以计算从R2到R2以下任何测量点的数据包丢失。
Using a fixed timer for color switching offers better control over the method: the (time) length of the blocks can be chosen large enough to simplify the collection and the comparison of measures taken by different network devices. It's preferable to read the value of the counters not immediately after the color switch: some packets could arrive out of order and increment the counter associated with the previous block (color), so it is worth waiting for some time. A safe choice is to wait L/2 time units (where L is the duration for each block) after the color switch, to read the still counter of the previous color, so the possibility of reading a running counter instead of a still one is minimized. The drawback is that the longer the duration of the block, the less frequent the measurement can be taken.
使用固定计时器进行颜色切换可以更好地控制该方法：可以选择足够大的块（时间）长度，以简化不同网络设备所采取措施的收集和比较。最好不要在颜色切换后立即读取计数器的值：某些数据包可能会无序到达，并增加与前一个块（颜色）关联的计数器，因此值得等待一段时间。安全的选择是在颜色切换后等待1/2个时间单位（其中L是每个块的持续时间），以读取前一颜色的静止计数器，因此读取运行计数器而不是静止计数器的可能性最小化。缺点是块的持续时间越长，测量频率越低。
The following table shows how the counters can be used to calculate the packet loss between R1 and R2. The first column lists the sequence of traffic blocks, while the other columns contain the counters of A-colored packets and B-colored packets for R1 and R2. In this example, we assume that the values of the counters are reset to zero whenever a block ends and its associated counter has been read: with this assumption, the table shows only relative values, which is the exact number of packets of each color within each block. If the values of the counters were not reset, the table would contain cumulative values, but the relative values could be determined simply by the difference from the value of the previous block of the same color.
下表显示了如何使用计数器计算R1和R2之间的数据包丢失。第一列列出了业务块的序列，而其他列包含R1和R2的A色数据包和B色数据包的计数器。在这个例子中，我们假设每当一个块结束并且读取了它的相关计数器时，计数器的值被重置为零：在这个假设下，表格只显示相对值，即每个块中每种颜色的包的确切数量。如果计数器的值未重置，则该表将包含累积值，但可以通过与相同颜色的前一个块的值的差值来确定相对值。
The color is switched on the basis of a fixed timer (not shown in the table), so the number of packets in each block is different.
颜色根据固定计时器（表中未显示）进行切换，因此每个块中的数据包数量不同。
+-------+--------+--------+--------+--------+------+
| Block | C(A)R1 | C(B)R1 | C(A)R2 | C(B)R2 | Loss |
+-------+--------+--------+--------+--------+------+
| 1 | 375 | 0 | 375 | 0 | 0 |
| 2 | 0 | 388 | 0 | 388 | 0 |
| 3 | 382 | 0 | 381 | 0 | 1 |
| 4 | 0 | 377 | 0 | 374 | 3 |
| ... | ... | ... | ... | ... | ... |
| 2n | 0 | 387 | 0 | 387 | 0 |
| 2n+1 | 379 | 0 | 377 | 0 | 2 |
+-------+--------+--------+--------+--------+------+
+-------+--------+--------+--------+--------+------+
| Block | C(A)R1 | C(B)R1 | C(A)R2 | C(B)R2 | Loss |
+-------+--------+--------+--------+--------+------+
| 1 | 375 | 0 | 375 | 0 | 0 |
| 2 | 0 | 388 | 0 | 388 | 0 |
| 3 | 382 | 0 | 381 | 0 | 1 |
| 4 | 0 | 377 | 0 | 374 | 3 |
| ... | ... | ... | ... | ... | ... |
| 2n | 0 | 387 | 0 | 387 | 0 |
| 2n+1 | 379 | 0 | 377 | 0 | 2 |
+-------+--------+--------+--------+--------+------+
Table 1: Evaluation of Counters for Packet Loss Measurements
表1：分组丢失测量计数器的评估
During an A block (blocks 1, 3, and 2n+1), all the packets are A-colored; therefore, the C(A) counters are incremented to the number seen on the interface, while C(B) counters are zero. Conversely, during a B block (blocks 2, 4, and 2n), all the packets are B-colored: C(A) counters are zero, while C(B) counters are incremented.
在A块（块1、3和2n+1）期间，所有分组都是A色的；因此，C（A）计数器增加到界面上显示的数字，而C（B）计数器为零。相反，在B块（块2、4和2n）期间，所有包都是B色的：C（a）计数器为零，而C（B）计数器递增。
When a block ends (because of color switching), the relative counters stop incrementing; it is possible to read them, compare the values measured on routers R1 and R2, and calculate the packet loss within that block.
当块结束时（由于颜色切换），相对计数器停止递增；可以读取它们，比较路由器R1和R2上测量的值，并计算该块内的数据包丢失。
For example, looking at the table above, during the first block (A-colored), C(A)R1 and C(A)R2 have the same value (375), which corresponds to the exact number of packets of the first block (no loss). Also, during the second block (B-colored), R1 and R2 counters have the same value (388), which corresponds to the number of packets of the second block (no loss). During the third and fourth blocks,
例如，查看上表，在第一块（A色）期间，C（A）R1和C（A）R2具有相同的值（375），其对应于第一块（无丢失）的确切分组数。此外，在第二块（B色）期间，R1和R2计数器具有相同的值（388），其对应于第二块的分组数（无丢失）。在第三和第四个街区，
R1 and R2 counters are different, meaning that some packets have been lost: in the example, one single packet (382-381) was lost during block three, and three packets (377-374) were lost during block four.
R1和R2计数器不同，这意味着一些数据包已经丢失：在本例中，一个数据包（382-381）在块3期间丢失，三个数据包（377-374）在块4期间丢失。
The method applied to R1 and R2 can be extended to any other router and applied to more complex networks, as far as the measurement is enabled on the path followed by the traffic flow(s) being observed.
适用于R1和R2的方法可以扩展到任何其他路由器，并适用于更复杂的网络，只要在观察到的流量所遵循的路径上启用测量。
It's worth mentioning two different strategies that can be used when implementing the method:
值得一提的是，在实施该方法时，可以使用两种不同的策略：
o flow-based: the flow-based strategy is used when only a limited number of traffic flows need to be monitored. According to this strategy, only a subset of the flows is colored. Counters for packet loss measurements can be instantiated for each single flow, or for the set as a whole, depending on the desired granularity. A relevant problem with this approach is the necessity to know in advance the path followed by flows that are subject to measurement. Path rerouting and traffic load-balancing increase the issue complexity, especially for unicast traffic. The problem is easier to solve for multicast traffic, where load-balancing is seldom used and static joins are frequently used to force traffic forwarding and replication.
o 基于流量：当只需要监控有限数量的交通流时，使用基于流量的策略。根据这个策略，只有一部分流是彩色的。根据所需的粒度，可以为每个流或整个集合实例化包丢失测量计数器。这种方法的一个相关问题是，必须事先知道需要测量的流量所遵循的路径。路径重路由和流量负载平衡增加了问题的复杂性，特别是对于单播流量。对于很少使用负载平衡且经常使用静态联接来强制流量转发和复制的多播流量，这个问题更容易解决。
o link-based: measurements are performed on all the traffic on a link-by-link basis. The link could be a physical link or a logical link. Counters could be instantiated for the traffic as a whole or for each traffic class (in case it is desired to monitor each class separately), but in the second case, a couple of counters are needed for each class.
o 基于链路：在逐个链路的基础上对所有流量执行测量。链接可以是物理链接或逻辑链接。可以为整个流量或每个流量类实例化计数器（如果需要单独监视每个类），但在第二种情况下，每个类需要两个计数器。
As mentioned, the flow-based measurement requires the identification of the flow to be monitored and the discovery of the path followed by the selected flow. It is possible to monitor a single flow or multiple flows grouped together, but in this case, measurement is consistent only if all the flows in the group follow the same path. Moreover, if a measurement is performed by grouping many flows, it is not possible to determine exactly which flow was affected by packet loss. In order to have measures per single flow, it is necessary to configure counters for each specific flow. Once the flow(s) to be monitored has been identified, it is necessary to configure the monitoring on the proper nodes. Configuring the monitoring means configuring the rule to intercept the traffic and configuring the counters to count the packets. To have just an end-to-end monitoring, it is sufficient to enable the monitoring on the first-and last-hop routers of the path: the mechanism is completely transparent to intermediate nodes and independent from the path followed by traffic flows. On the contrary, to monitor the flow on a
如上所述，基于流量的测量要求识别要监控的流量，并发现所选流量所遵循的路径。可以监控单个流或分组在一起的多个流，但在这种情况下，只有当组中的所有流都遵循相同的路径时，测量才是一致的。此外，如果通过分组许多流来执行测量，则不可能准确地确定哪个流受到分组丢失的影响。为了对每个流进行测量，有必要为每个特定流配置计数器。一旦确定了要监控的流，就需要在适当的节点上配置监控。配置监控意味着配置规则以拦截流量，并配置计数器以统计数据包。为了只进行端到端监控，只需在路径的第一个和最后一个跃点路由器上启用监控即可：该机制对中间节点完全透明，并且独立于随后的流量路径。相反，要监视
hop-by-hop basis along its whole path, it is necessary to enable the monitoring on every node from the source to the destination. In case the exact path followed by the flow is not known a priori (i.e., the flow has multiple paths to reach the destination), it is necessary to enable the monitoring system on every path: counters on interfaces traversed by the flow will report packet count, whereas counters on other interfaces will be null.
在逐跳的基础上，沿着其整个路径，有必要在从源到目的地的每个节点上启用监视。如果流所遵循的确切路径事先未知（即，流有多条路径到达目的地），则有必要在每条路径上启用监控系统：流所遍历的接口上的计数器将报告数据包计数，而其他接口上的计数器将为空。
The coloring operation is fundamental in order to create packet blocks. This implies choosing where to activate the coloring and how to color the packets.
着色操作是创建数据包块的基础。这意味着选择在何处激活着色以及如何为数据包着色。
In case of flow-based measurements, the flow to monitor can be defined by a set of selection rules (e.g., header fields) used to match a subset of the packets; in this way, it is possible to control the number of involved nodes, the path followed by the packets, and the size of the flows. It is possible, in general, to have multiple coloring nodes or a single coloring node that is easier to manage and doesn't raise any risk of conflict. Coloring in multiple nodes can be done, and the requirement is that the coloring must change periodically between the nodes according to the timing considerations in Section 3.2; so every node that is designated as a measurement point along the path should be able to identify unambiguously the colored packets. Furthermore, [MULTIPOINT-ALT-MM] generalizes the coloring for multipoint-to-multipoint flow. In addition, it can be advantageous to color the flow as close as possible to the source because it allows an end-to-end measure if a measurement point is enabled on the last-hop router as well.
在基于流的测量的情况下，要监视的流可以由用于匹配分组子集的一组选择规则（例如，报头字段）来定义；通过这种方式，可以控制相关节点的数量、数据包所遵循的路径以及流的大小。一般来说，可以有多个着色节点或单个着色节点，这样更易于管理且不会产生任何冲突风险。可以在多个节点中进行着色，要求根据第3.2节中的计时考虑，着色必须在节点之间周期性地改变；因此，沿路径指定为测量点的每个节点都应该能够明确地识别彩色数据包。此外，[MULTIPOINT-ALT-MM]还推广了多点到多点流的着色。此外，将流着色到尽可能靠近源是有利的，因为如果在最后一跳路由器上也启用了测量点，则允许端到端测量。
For link-based measurements, all traffic needs to be colored when transmitted on the link. If the traffic had already been colored, then it has to be re-colored because the color must be consistent on the link. This means that each hop along the path must (re-)color the traffic; the color is not required to be consistent along different links.
对于基于链路的测量，当在链路上传输时，所有流量都需要着色。如果流量已经上色，则必须重新上色，因为链接上的颜色必须一致。这意味着路径上的每一跳都必须（重新）为流量着色；不同链接的颜色不需要一致。
Traffic coloring can be implemented by setting a specific bit in the packet header and changing the value of that bit periodically. How to choose the marking field depends on the application and is out of scope here. However, some applications are reported in Section 5.
流量着色可以通过在包头中设置一个特定的位并定期更改该位的值来实现。如何选择标记字段取决于应用程序，超出了此处的范围。但是，第5节报告了一些应用。
For flow-based measurements, assuming that the coloring of the packets is performed only by the source nodes, the nodes between source and destination (included) have to count the colored packets that they receive and forward: this operation can be enabled on every router along the path or only on a subset, depending on which network segment is being monitored (a single link, a particular metro area, the backbone, or the whole path). Since the color switches periodically between two values, two counters (one for each value) are needed: one counter for packets with color A and one counter for packets with color B. For each flow (or group of flows) being monitored and for every interface where the monitoring is Active, a couple of counters are needed. For example, in order to separately monitor three flows on a router with four interfaces involved, 24 counters are needed (two counters for each of the three flows on each of the four interfaces). Furthermore, [MULTIPOINT-ALT-MM] generalizes the counting for multipoint-to-multipoint flow.
对于基于流的测量，假设数据包的着色仅由源节点执行，源节点和目标节点（包括）之间的节点必须计算它们接收和转发的着色数据包：此操作可以在路径上的每个路由器上启用，也可以仅在子集上启用，取决于正在监视的网段（单个链路、特定的城域网、主干网或整个路径）。由于颜色在两个值之间定期切换，因此需要两个计数器（每个值一个）：一个计数器用于颜色为A的数据包，另一个计数器用于颜色为B的数据包。对于被监控的每个流（或流组）以及监控活动的每个接口，需要两个计数器。例如，为了单独监控路由器上涉及四个接口的三个流，需要24个计数器（四个接口上的三个流中的每一个都需要两个计数器）。此外，[MULTIPOINT-ALT-MM]概括了多点到多点流的计数。
In case of link-based measurements, the behavior is similar except that coloring and counting operations are performed on a link-by-link basis at each endpoint of the link.
在基于链接的测量中，除了在链接的每个端点逐个链接执行着色和计数操作外，行为类似。
Another important aspect to take into consideration is when to read the counters: in order to count the exact number of packets of a block, the routers must perform this operation when that block has ended; in other words, the counter for color A must be read when the current block has color B, in order to be sure that the value of the counter is stable. This task can be accomplished in two ways. The general approach suggests reading the counters periodically, many times during a block duration, and comparing these successive readings: when the counter stops incrementing, it means that the current block has ended, and its value can be elaborated safely. Alternatively, if the coloring operation is performed on the basis of a fixed timer, it is possible to configure the reading of the counters according to that timer: for example, reading the counter for color A every period in the middle of the subsequent block with color B is a safe choice. A sufficient margin should be considered between the end of a block and the reading of the counter, in order to take into account any out-of-order packets.
要考虑的另一个重要方面是何时读取计数器：为了计算一个块的数据包的确切数量，路由器必须在该块结束时执行此操作；换句话说，当当前块具有颜色B时，必须读取颜色A的计数器，以确保计数器的值稳定。这项任务可以通过两种方式完成。一般方法建议定期读取计数器，在块持续时间内多次，并比较这些连续读数：当计数器停止递增时，意味着当前块已结束，其值可以安全地细化。或者，如果在固定定时器的基础上执行着色操作，则可以根据该定时器配置计数器的读数：例如，用颜色B读取后续颜色块中间的每个周期的颜色计数器是安全的选择。为了考虑任何无序数据包，应在数据块结束和计数器读数之间考虑足够的余量。
The nodes enabled to perform performance monitoring collect the value of the counters, but they are not able to directly use this information to measure packet loss, because they only have their own samples. For this reason, an external Network Management System (NMS) can be used to collect and elaborate data and to perform packet loss calculation. The NMS compares the values of counters from different nodes and can calculate if some packets were lost (even a single packet) and where those packets were lost.
能够执行性能监视的节点收集计数器的值，但它们不能直接使用此信息来测量数据包丢失，因为它们只有自己的样本。因此，可以使用外部网络管理系统（NMS）来收集和细化数据，并执行分组丢失计算。NMS比较来自不同节点的计数器值，并可以计算某些数据包是否丢失（即使是单个数据包）以及这些数据包丢失的位置。
The value of the counters needs to be transmitted to the NMS as soon as it has been read. This can be accomplished by using SNMP or FTP and can be done in Push Mode or Polling Mode. In the first case, each router periodically sends the information to the NMS; in the latter case, it is the NMS that periodically polls routers to collect information. In any case, the NMS has to collect all the relevant values from all the routers within one cycle of the timer.
计数器的值需要在读取后立即传输到NMS。这可以通过使用SNMP或FTP实现，并且可以在推送模式或轮询模式下完成。在第一种情况下，每个路由器周期性地向NMS发送信息；在后一种情况下，NMS定期轮询路由器以收集信息。在任何情况下，NMS都必须在计时器的一个周期内从所有路由器收集所有相关值。
It would also be possible to use a protocol to exchange values of counters between the two endpoints in order to let them perform the packet loss calculation for each traffic direction.
还可以使用协议在两个端点之间交换计数器的值，以便让它们为每个业务方向执行丢包计算。
A possible approach for the performance measurement (PM) architecture is explained in [COLORING], while [IP-FLOW-REPORT] introduces new information elements of IP Flow Information Export (IPFIX) [RFC7011].
性能度量（PM）体系结构的一种可能方法在[COLORING]中进行了解释，[IP-FLOW-REPORT]引入了IP流信息导出（IPFIX）[RFC7011]的新信息元素。
This document introduces two color-switching methods: one is based on a fixed number of packets, and the other is based on a fixed timer. But the method based on a fixed timer is preferable because it is more deterministic, and it will be considered in the rest of the document.
本文档介绍了两种颜色切换方法：一种基于固定数量的数据包，另一种基于固定计时器。但基于固定计时器的方法更可取，因为它更具确定性，并且将在本文档的其余部分中予以考虑。
In general, clocks in network devices are not accurate and for this reason, there is a clock error between the measurement points R1 and R2. But, to implement the methodology, they must be synchronized to the same clock reference with an accuracy of +/- L/2 time units, where L is the fixed time duration of the block. So each colored packet can be assigned to the right batch by each router. This is because the minimum time distance between two packets of the same color but that belong to different batches is L time units.
通常，网络设备中的时钟不准确，因此，测量点R1和R2之间存在时钟误差。但是，为了实现该方法，它们必须以+/-L/2时间单位的精度同步到相同的时钟基准，其中L是块的固定持续时间。因此，每个路由器可以将每个彩色数据包分配给正确的批次。这是因为相同颜色但属于不同批次的两个数据包之间的最小时间距离为L时间单位。
In practice, in addition to clock errors, the delay between measurement points also affects the implementation of the methodology because each packet can be delayed differently, and this can produce out of order at batch boundaries. This means that, without considering clock error, we wait L/2 after color switching to be sure to take a still counter.
在实践中，除了时钟错误外，测量点之间的延迟也会影响方法的实施，因为每个数据包的延迟可能不同，这可能在批边界处产生无序。这意味着，在不考虑时钟误差的情况下，我们在颜色切换后等待L/2，以确保使用静止计数器。
In summary, we need to take into account two contributions: clock error between network devices and the interval we need to wait to avoid packets being out of order because of network delay.
总之，我们需要考虑两个因素：网络设备之间的时钟错误和我们需要等待的时间间隔，以避免由于网络延迟导致数据包无序。
The following figure explains both issues.
下图解释了这两个问题。
...BBBBBBBBB | AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA | BBBBBBBBB...
|<======================================>|
| L |
...=========>|<==================><==================>|<==========...
| L/2 L/2 |
|<===>| |<===>|
d | | d
|<==========================>|
available counting interval
...BBBBBBBBB | AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA | BBBBBBBBB...
|<======================================>|
| L |
...=========>|<==================><==================>|<==========...
| L/2 L/2 |
|<===>| |<===>|
d | | d
|<==========================>|
available counting interval
Figure 4: Timing Aspects
图4：时间方面
It is assumed that all network devices are synchronized to a common reference time with an accuracy of +/- A/2. Thus, the difference between the clock values of any two network devices is bounded by A.
假设所有网络设备都同步到一个公共参考时间，精度为+/-a/2。因此，任意两个网络设备的时钟值之间的差由A限定。
The guard band d is given by:
保护带d由下式给出：
d = A + D_max - D_min,
d=A+d_最大值-d_最小值，
where A is the clock accuracy, D_max is an upper bound on the network delay between the network devices, and D_min is a lower bound on the delay.
其中A是时钟精度，D_max是网络设备之间网络延迟的上界，D_min是延迟的下界。
The available counting interval is L - 2d that must be > 0.
可用的计数间隔为L-2d，必须大于0。
The condition that must be satisfied and is a requirement on the synchronization accuracy is:
同步精度必须满足的条件是：
d < L/2.
d<L/2。
The same principle used to measure packet loss can be applied also to one-way delay measurement. There are three alternatives, as described hereinafter.
用于测量分组丢失的相同原理也可应用于单向延迟测量。如下文所述，有三种备选方案。
Note that, for all the one-way delay alternatives described in the next sections, by summing the one-way delays of the two directions of a path, it is always possible to measure the two-way delay (round-trip "virtual" delay).
注意，对于下一节中描述的所有单向延迟备选方案，通过将路径两个方向的单向延迟相加，始终可以测量双向延迟（往返“虚拟”延迟）。
The alternation of colors can be used as a time reference to calculate the delay. Whenever the color changes (which means that a new block has started), a network device can store the timestamp of the first packet of the new block; that timestamp can be compared with the timestamp of the same packet on a second router to compute packet delay. When looking at Figure 2, R1 stores the timestamp TS(A1)R1 when it sends the first packet of block 1 (A-colored), the timestamp TS(B2)R1 when it sends the first packet of block 2 (B-colored), and so on for every other block. R2 performs the same operation on the receiving side, recording TS(A1)R2, TS(B2)R2, and so on. Since the timestamps refer to specific packets (the first packet of each block), we are sure that timestamps compared to compute delay refer to the same packets. By comparing TS(A1)R1 with TS(A1)R2 (and similarly TS(B2)R1 with TS(B2)R2, and so on), it is possible to measure the delay between R1 and R2. In order to have more measurements, it is possible to take and store more timestamps, referring to other packets within each block.
颜色的交替可以用作计算延迟的时间参考。每当颜色改变时（这意味着新块已经开始），网络设备可以存储新块的第一分组的时间戳；可以将该时间戳与第二路由器上相同分组的时间戳进行比较，以计算分组延迟。当查看图2时，R1在发送块1的第一个数据包（A色）时存储时间戳TS（A1）R1，在发送块2的第一个数据包（B色）时存储时间戳TS（B2）R1，依此类推。R2在接收侧执行相同的操作，记录TS（A1）R2、TS（B2）R2等。由于时间戳指的是特定的数据包（每个块的第一个数据包），因此我们可以确定，与计算延迟相比，时间戳指的是相同的数据包。通过比较TS（A1）R1和TS（A1）R2（类似地，TS（B2）R1和TS（B2）R2等），可以测量R1和R2之间的延迟。为了有更多的测量，可以参考每个块中的其他数据包来获取和存储更多的时间戳。
In order to coherently compare timestamps collected on different routers, the clocks on the network nodes must be in sync. Furthermore, a measurement is valid only if no packet loss occurs and if packet misordering can be avoided; otherwise, the first packet of a block on R1 could be different from the first packet of the same block on R2 (for instance, if that packet is lost between R1 and R2 or it arrives after the next one).
为了一致地比较不同路由器上收集的时间戳，网络节点上的时钟必须同步。此外，只有在不发生分组丢失并且分组误序可以避免的情况下，测量才有效；否则，R1上块的第一个数据包可能不同于R2上同一块的第一个数据包（例如，如果该数据包在R1和R2之间丢失或在下一个数据包之后到达）。
The following table shows how timestamps can be used to calculate the delay between R1 and R2. The first column lists the sequence of blocks, while other columns contain the timestamp referring to the first packet of each block on R1 and R2. The delay is computed as a difference between timestamps. For the sake of simplicity, all the values are expressed in milliseconds.
下表显示了如何使用时间戳计算R1和R2之间的延迟。第一列列出了块序列，而其他列包含时间戳，表示R1和R2上每个块的第一个数据包。延迟计算为时间戳之间的差值。为了简单起见，所有值都以毫秒表示。
+-------+---------+---------+---------+---------+-------------+
| Block | TS(A)R1 | TS(B)R1 | TS(A)R2 | TS(B)R2 | Delay R1-R2 |
+-------+---------+---------+---------+---------+-------------+
| 1 | 12.483 | - | 15.591 | - | 3.108 |
| 2 | - | 6.263 | - | 9.288 | 3.025 |
| 3 | 27.556 | - | 30.512 | - | 2.956 |
| | - | 18.113 | - | 21.269 | 3.156 |
| ... | ... | ... | ... | ... | ... |
| 2n | 77.463 | - | 80.501 | - | 3.038 |
| 2n+1 | - | 24.333 | - | 27.433 | 3.100 |
+-------+---------+---------+---------+---------+-------------+
+-------+---------+---------+---------+---------+-------------+
| Block | TS(A)R1 | TS(B)R1 | TS(A)R2 | TS(B)R2 | Delay R1-R2 |
+-------+---------+---------+---------+---------+-------------+
| 1 | 12.483 | - | 15.591 | - | 3.108 |
| 2 | - | 6.263 | - | 9.288 | 3.025 |
| 3 | 27.556 | - | 30.512 | - | 2.956 |
| | - | 18.113 | - | 21.269 | 3.156 |
| ... | ... | ... | ... | ... | ... |
| 2n | 77.463 | - | 80.501 | - | 3.038 |
| 2n+1 | - | 24.333 | - | 27.433 | 3.100 |
+-------+---------+---------+---------+---------+-------------+
Table 2: Evaluation of Timestamps for Delay Measurements
表2：延迟测量的时间戳评估
The first row shows timestamps taken on R1 and R2, respectively, and refers to the first packet of block 1 (which is A-colored). Delay can be computed as a difference between the timestamp on R2 and the timestamp on R1. Similarly, the second row shows timestamps (in milliseconds) taken on R1 and R2 and refers to the first packet of block 2 (which is B-colored). By comparing timestamps taken on different nodes in the network and referring to the same packets (identified using the alternation of colors), it is possible to measure delay on different network segments.
第一行分别显示R1和R2上的时间戳，并表示块1的第一个数据包（A色）。延迟可以计算为R2上的时间戳和R1上的时间戳之间的差值。类似地，第二行显示R1和R2上的时间戳（以毫秒为单位），并引用块2的第一个数据包（B色）。通过比较网络中不同节点上的时间戳并参考相同的数据包（使用颜色的交替来识别），可以测量不同网段上的延迟。
For the sake of simplicity, in the above example, a single measurement is provided within a block, taking into account only the first packet of each block. The number of measurements can be easily increased by considering multiple packets in the block: for instance, a timestamp could be taken every N packets, thus generating multiple delay measurements. Taking this to the limit, in principle, the delay could be measured for each packet by taking and comparing the corresponding timestamps (possible but impractical from an implementation point of view).
为了简单起见，在上述示例中，在块内提供单个测量，仅考虑每个块的第一个分组。通过考虑块中的多个分组，可以容易地增加测量的数量：例如，可以每N个分组获取一个时间戳，从而生成多个延迟测量。原则上，将其限制在一定范围内，可以通过获取和比较相应的时间戳来测量每个分组的延迟（从实现的角度来看，这可能但不切实际）。
As mentioned before, the method previously exposed for measuring the delay is sensitive to out-of-order reception of packets. In order to overcome this problem, a different approach has been considered: it is based on the concept of mean delay. The mean delay is calculated by considering the average arrival time of the packets within a single block. The network device locally stores a timestamp for each packet received within a single block: summing all the timestamps and dividing by the total number of packets received, the average arrival time for that block of packets can be calculated. By subtracting the average arrival times of two adjacent devices, it is possible to calculate the mean delay between those nodes. When computing the mean delay, the measurement error could be augmented by accumulating
如前所述，先前公开的用于测量延迟的方法对分组的无序接收敏感。为了克服这个问题，人们考虑了一种不同的方法：它基于平均延迟的概念。通过考虑单个块内数据包的平均到达时间来计算平均延迟。网络设备在本地存储单个块内接收的每个分组的时间戳：将所有时间戳相加并除以接收的分组总数，可以计算该分组块的平均到达时间。通过减去两个相邻设备的平均到达时间，可以计算这些节点之间的平均延迟。在计算平均延迟时，测量误差可以通过累积来增大
the measurement error of a lot of packets. This method is robust to out-of-order packets and also to packet loss (only a small error is introduced). Moreover, it greatly reduces the number of timestamps (only one per block for each network device) that have to be collected by the management system. On the other hand, it only gives one measure for the duration of the block (for instance, 5 minutes), and it doesn't give the minimum, maximum, and median delay values [RFC6703]. This limitation could be overcome by reducing the duration of the block (for instance, from 5 minutes to a few seconds), which implicates a highly optimized implementation of the method.
大量数据包的测量误差。该方法对无序数据包和数据包丢失（只引入了一个小错误）具有鲁棒性。此外，它大大减少了必须由管理系统收集的时间戳的数量（每个网络设备每个块仅一个）。另一方面，它只给出了块持续时间的一个度量（例如，5分钟），而没有给出最小、最大和中值延迟值[RFC6703]。这一限制可以通过缩短块的持续时间（例如，从5分钟缩短到几秒钟）来克服，这意味着该方法的高度优化实现。
The Single-Marking methodology for one-way delay measurement is sensitive to out-of-order reception of packets. The first approach to overcome this problem has been described before and is based on the concept of mean delay. But the limitation of mean delay is that it doesn't give information about the delay value's distribution for the duration of the block. Additionally, it may be useful to have not only the mean delay but also the minimum, maximum, and median delay values and, in wider terms, to know more about the statistic distribution of delay values. So, in order to have more information about the delay and to overcome out-of-order issues, a different approach can be introduced; it is based on a Double-Marking methodology.
单向延迟测量的单标记方法对数据包的无序接收非常敏感。克服这个问题的第一种方法之前已经描述过，它基于平均延迟的概念。但是，平均延迟的局限性在于，它没有给出延迟值在块持续时间内的分布信息。此外，不仅要有平均延迟值，还要有最小、最大和中值延迟值，更广泛地说，还要了解延迟值的统计分布。因此，为了获得更多关于延迟的信息并克服无序问题，可以引入不同的方法；它基于双重标记方法。
Basically, the idea is to use the first marking to create the alternate flow and, within this colored flow, a second marking to select the packets for measuring delay/jitter. The first marking is needed for packet loss and mean delay measurement. The second marking creates a new set of marked packets that are fully identified over the network, so that a network device can store the timestamps of these packets; these timestamps can be compared with the timestamps of the same packets on a second router to compute packet delay values for each packet. The number of measurements can be easily increased by changing the frequency of the second marking. But the frequency of the second marking must not be too high in order to avoid out-of-order issues. Between packets with the second marking, there should be a security time gap (e.g., this gap could be, at the minimum, the mean network delay calculated with the previous methodology) to avoid out-of-order issues and also to have a number of measurement packets that are rate independent. If a second-marking packet is lost, the delay measurement for the considered block is corrupted and should be discarded.
基本上，想法是使用第一个标记来创建备用流，并且在该彩色流中，使用第二个标记来选择用于测量延迟/抖动的包。第一个标记用于分组丢失和平均延迟测量。第二标记创建通过网络完全识别的一组新的标记分组，以便网络设备可以存储这些分组的时间戳；这些时间戳可与第二路由器上相同分组的时间戳进行比较，以计算每个分组的分组延迟值。通过改变第二次标记的频率，可以很容易地增加测量次数。但第二次标记的频率不得过高，以避免出现无序问题。在具有第二标记的数据包之间，应存在安全时间间隔（例如，该间隔至少可以是使用先前方法计算的平均网络延迟），以避免无序问题，并且还应具有许多与速率无关的测量数据包。如果第二个标记数据包丢失，则所考虑的块的延迟测量被破坏，应丢弃。
Mean delay is calculated on all the packets of a sample and is a simple computation to be performed for a Single-Marking Method. In some cases, the mean delay measure is not sufficient to characterize the sample, and more statistics of delay extent data are needed, e.g., percentiles, variance, and median delay values. The conventional range (maximum-minimum) should be avoided for several reasons, including stability of the maximum delay due to the influence by outliers. RFC 5481 [RFC5481], Section 6.5 highlights how the 99.9th percentile of delay and delay variation is more helpful to performance planners. To overcome this drawback, the idea is to couple the mean delay measure for the entire batch with a Double-Marking Method, where a subset of batch packets is selected for extensive delay calculation by using a second marking. In this way, it is possible to perform a detailed analysis on these double-marked packets. Please note that there are classic algorithms for median and variance calculation, but they are out of the scope of this document. The comparison between the mean delay for the entire batch and the mean delay on these double-marked packets gives useful information since it is possible to understand if the Double-Marking measurements are actually representative of the delay trends.
平均延迟是对一个样本的所有数据包进行计算的，并且是针对单个标记方法执行的简单计算。在某些情况下，平均延迟度量不足以表征样本，需要更多延迟程度数据的统计信息，例如，百分位数、方差和延迟中值。出于几个原因，应避免使用常规范围（最大-最小值），包括由于异常值的影响而导致的最大延迟的稳定性。RFC 5481[RFC5481]，第6.5节强调了延迟和延迟变化的99.9%如何对绩效计划人员更有帮助。为了克服这一缺点，我们的想法是将整个批次的平均延迟度量与双标记方法相结合，其中通过使用第二个标记选择批次数据包的子集进行广泛的延迟计算。通过这种方式，可以对这些双标记分组执行详细分析。请注意，有用于中值和方差计算的经典算法，但它们不在本文档的范围内。整个批次的平均延迟与这些双标记数据包的平均延迟之间的比较提供了有用的信息，因为可以理解双标记测量值是否实际代表延迟趋势。
Similar to one-way delay measurement (both for Single Marking and Double Marking), the method can also be used to measure the inter-arrival jitter. We refer to the definition in RFC 3393 [RFC3393]. The alternation of colors, for a Single-Marking Method, can be used as a time reference to measure delay variations. In case of Double Marking, the time reference is given by the second-marked packets. Considering the example depicted in Figure 2, R1 stores the timestamp TS(A)R1 whenever it sends the first packet of a block, and R2 stores the timestamp TS(B)R2 whenever it receives the first packet of a block. The inter-arrival jitter can be easily derived from one-way delay measurement, by evaluating the delay variation of consecutive samples.
与单向延迟测量（单标记和双标记）类似，该方法也可用于测量到达间抖动。我们参考RFC 3393[RFC3393]中的定义。对于单个标记方法，颜色的交替可以用作测量延迟变化的时间参考。在双重标记的情况下，时间参考由第二个标记的数据包给出。考虑图2中所示的示例，R1在发送块的第一个数据包时存储时间戳TS（A）R1，R2在接收块的第一个数据包时存储时间戳TS（B）R2。通过评估连续样本的延迟变化，单向延迟测量可以很容易地得出到达间抖动。
The concept of mean delay can also be applied to delay variation, by evaluating the average variation of the interval between consecutive packets of the flow from R1 to R2.
通过评估从R1到R2的流的连续分组之间的间隔的平均变化，平均延迟的概念也可应用于延迟变化。
This section highlights some considerations about the methodology.
本节重点介绍了有关该方法的一些注意事项。
The Alternate-Marking technique does not require a strong synchronization, especially for packet loss and two-way delay measurement. Only one-way delay measurement requires network devices to have synchronized clocks.
交替标记技术不需要强同步，特别是对于分组丢失和双向延迟测量。只有单向延迟测量要求网络设备具有同步时钟。
Color switching is the reference for all the network devices, and the only requirement to be achieved is that all network devices have to recognize the right batch along the path.
颜色切换是所有网络设备的参考，需要实现的唯一要求是所有网络设备必须识别路径上的正确批次。
If the length of the measurement period is L time units, then all network devices must be synchronized to the same clock reference with an accuracy of +/- L/2 time units (without considering network delay). This level of accuracy guarantees that all network devices consistently match the color bit to the correct block. For example, if the color is toggled every second (L = 1 second), then clocks must be synchronized with an accuracy of +/- 0.5 second to a common time reference.
如果测量周期长度为L个时间单位，则所有网络设备必须同步到同一时钟基准，精度为+/-L/2个时间单位（不考虑网络延迟）。此精度级别可确保所有网络设备一致地将颜色位匹配到正确的块。例如，如果每秒切换一次颜色（L=1秒），则时钟必须以+/-0.5秒的精度与公共时间基准同步。
This synchronization requirement can be satisfied even with a relatively inaccurate synchronization method. This is true for packet loss and two-way delay measurement, but not for one-way delay measurement, where clock synchronization must be accurate.
即使使用相对不准确的同步方法，也可以满足此同步要求。这适用于数据包丢失和双向延迟测量，但不适用于单向延迟测量，在单向延迟测量中，时钟同步必须准确。
Therefore, a system that uses only packet loss and two-way delay measurement does not require synchronization. This is because the value of the clocks of network devices does not affect the computation of the two-way delay measurement.
因此，仅使用分组丢失和双向延迟测量的系统不需要同步。这是因为网络设备的时钟值不影响双向延迟测量的计算。
Data correlation is the mechanism to compare counters and timestamps for packet loss, delay, and delay variation calculation. It could be performed in several ways depending on the Alternate-Marking application and use case. Some possibilities are to:
数据关联是一种比较计数器和时间戳以计算数据包丢失、延迟和延迟变化的机制。根据替代标记应用和用例，可以通过多种方式执行。一些可能性是：
o use a centralized solution using NMS to correlate data; and
o 使用集中解决方案，使用NMS关联数据；和
o define a protocol-based distributed solution by introducing a new protocol or by extending the existing protocols (e.g., see RFC 6374 [RFC6374] or the Two-Way Active Measurement Protocol (TWAMP) as defined in RFC 5357 [RFC5357] or the One-Way Active Measurement Protocol (OWAMP) as defined in RFC 4656 [RFC4656]) in order to communicate the counters and timestamps between nodes.
o 通过引入新协议或扩展现有协议（例如，参见RFC 6374[RFC6374]或RFC 5357[RFC5357]中定义的双向主动测量协议（TWAMP）或RFC 4656[RFC4656]中定义的单向主动测量协议（OWAMP），定义基于协议的分布式解决方案以便在节点之间通信计数器和时间戳。
In the following paragraphs, an example data correlation mechanism is explained and could be used independently of the adopted solutions.
在以下段落中，将解释示例数据关联机制，该机制可独立于所采用的解决方案使用。
When data is collected on the upstream and downstream nodes, e.g., packet counts for packet loss measurement or timestamps for packet delay measurement, and is periodically reported to or pulled by other nodes or an NMS, a certain data correlation mechanism SHOULD be in use to help the nodes or NMS tell whether any two or more packet counts are related to the same block of markers or if any two timestamps are related to the same marked packet.
当在上游和下游节点上收集数据时，例如，用于分组丢失测量的分组计数或用于分组延迟测量的时间戳，并且定期向其他节点或NMS报告或由其他节点或NMS拉取数据，应该使用某种数据关联机制来帮助节点或NMS判断任何两个或多个数据包计数是否与同一标记块相关，或者任何两个时间戳是否与同一标记数据包相关。
The Alternate-Marking Method described in this document literally splits the packets of the measured flow into different measurement blocks; in addition, a Block Number (BN) could be assigned to each such measurement block. The BN is generated each time a node reads the data (packet counts or timestamps) and is associated with each packet count and timestamp reported to or pulled by other nodes or NMSs. The value of a BN could be calculated as the modulo of the local time (when the data are read) and the interval of the marking time period.
本文件中所述的替代标记方法将被测流量的数据包分为不同的测量块；此外，可以为每个这样的测量块分配块号（BN）。BN在每次节点读取数据（包计数或时间戳）时生成，并与向其他节点或nms报告或由其他节点或nms拉取的每个包计数和时间戳相关联。BN的值可以计算为本地时间（读取数据时）和标记时间段间隔的模。
When the nodes or NMS see, for example, the same BNs associated with two packet counts from an upstream and a downstream node, respectively, it considers that these two packet counts correspond to the same block, i.e., these two packet counts belong to the same block of markers from the upstream and downstream nodes. The assumption of this BN mechanism is that the measurement nodes are time synchronized. This requires the measurement nodes to have a certain time synchronization capability (e.g., the Network Time Protocol (NTP) [RFC5905] or the IEEE 1588 Precision Time Protocol (PTP) [IEEE-1588]). Synchronization aspects are further discussed in Section 4.1.
例如，当节点或NMS看到分别与来自上游和下游节点的两个分组计数相关联的相同bn时，其认为这两个分组计数对应于相同块，即，这两个分组计数属于来自上游和下游节点的相同标记块。这种BN机制的假设是测量节点是时间同步的。这要求测量节点具有一定的时间同步能力（例如，网络时间协议（NTP）[RFC5905]或IEEE 1588精密时间协议（PTP）[IEEE-1588]）。第4.1节将进一步讨论同步方面。
Due to ECMP, packet reordering is very common in an IP network. The accuracy of a marking-based PM, especially packet loss measurement, may be affected by packet reordering. Take a look at the following example:
由于ECMP，数据包重新排序在IP网络中非常常见。基于标记的PM的准确性，尤其是分组丢失测量，可能会受到分组重新排序的影响。请看以下示例：
Block : 1 | 2 | 3 | 4 | 5 |...
--------|---------|---------|---------|---------|---------|---
Node R1 : AAAAAAA | BBBBBBB | AAAAAAA | BBBBBBB | AAAAAAA |...
Node R2 : AAAAABB | AABBBBA | AAABAAA | BBBBBBA | ABAAABA |...
Block : 1 | 2 | 3 | 4 | 5 |...
--------|---------|---------|---------|---------|---------|---
Node R1 : AAAAAAA | BBBBBBB | AAAAAAA | BBBBBBB | AAAAAAA |...
Node R2 : AAAAABB | AABBBBA | AAABAAA | BBBBBBA | ABAAABA |...
Figure 5: Packet Reordering
图5：数据包重新排序
In Figure 5, the packet stream for Node R1 isn't being reordered and can be safely assigned to interval blocks, but the packet stream for Node R2 is being reordered; so, looking at the packet with the marker
在图5中，节点R1的数据包流没有被重新排序，可以安全地分配给间隔块，但节点R2的数据包流正在被重新排序；那么，看看有标记的包
of "B" in block 3, there is no safe way to tell whether the packet belongs to block 2 or block 4.
对于块3中的“B”，没有安全的方法来判断数据包是属于块2还是块4。
In general, there is the need to assign packets with the marker of "B" or "A" to the right interval blocks. Most of the packet reordering occurs at the edge of adjacent blocks, and they are easy to handle if the interval of each block is sufficiently large. Then, it can be assumed that the packets with different markers belong to the block that they are closer to. If the interval is small, it is difficult and sometimes impossible to determine to which block a packet belongs.
通常，需要将具有“B”或“A”标记的分组分配给正确的间隔块。大多数分组重新排序发生在相邻块的边缘，如果每个块的间隔足够大，则它们很容易处理。然后，可以假设具有不同标记的分组属于它们更接近的块。如果间隔很小，则很难且有时不可能确定数据包属于哪个块。
To choose a proper interval is important, and how to choose a proper interval is out of the scope of this document. But an implementation SHOULD provide a way to configure the interval and allow a certain degree of packet reordering.
选择合适的时间间隔很重要，如何选择合适的时间间隔超出了本文档的范围。但是，实现应该提供一种配置间隔的方法，并允许一定程度的数据包重新排序。
The methodology described in the previous sections can be applied in various situations. Basically, the Alternate-Marking technique could be used in many cases for performance measurement. The only requirement is to select and mark the flow to be monitored; in this way, packets are batched by the sender, and each batch is alternately marked such that it can be easily recognized by the receiver.
前几节中描述的方法可以应用于各种情况。基本上，替代标记技术在许多情况下可用于性能测量。唯一的要求是选择和标记要监控的流量；以这种方式，数据包由发送方进行批处理，并且每个批都交替地进行标记，以便接收方能够容易地识别。
Some recent Alternate-Marking Method applications are listed below:
下面列出了一些最近的替代标记方法应用：
o IP Flow Performance Measurement (IPFPM): this application of the marking method is described in [COLORING]. As an example, in this document, the last reserved bit of the Flag field of the IPv4 header is proposed to be used for marking, while a solution for IPv6 could be to leverage the IPv6 extension header for marking.
o IP流量性能测量（IPFPM）：标记方法的应用在[着色]中进行了描述。例如，在本文档中，建议将IPv4标头的标志字段的最后保留位用于标记，而IPv6的解决方案可以是利用IPv6扩展标头进行标记。
o OAM Passive Performance Measurement: In [RFC8296], two OAM bits from the Bit Index Explicit Replication (BIER) header are reserved for the Passive performance measurement marking method. [PM-MM-BIER] details the measurement for multicast service over the BIER domain. In addition, the Alternate-Marking Method could also be used in a Service Function Chaining (SFC) domain. Lastly, the application of the marking method to Network Virtualization over Layer 3 (NVO3) protocols is considered by [NVO3-ENCAPS].
o OAM被动性能度量：在[RFC8296]中，位索引显式复制（BIER）头中的两个OAM位保留用于被动性能度量标记方法。[PM-MM-BIER]详细说明了BIER域上多播服务的度量。此外，备用标记方法也可用于服务功能链接（SFC）域。最后，[NVO3-ENCAPS]考虑了标记方法在第3层网络虚拟化（NVO3）协议中的应用。
o MPLS Performance Measurement: RFC 6374 [RFC6374] uses the Loss Measurement (LM) packet as the packet accounting demarcation point. Unfortunately, this gives rise to a number of problems that may lead to significant packet accounting errors in certain situations. [MPLS-FLOW] discusses the desired capabilities for
o MPLS性能度量：RFC6374[RFC6374]使用丢失度量（LM）数据包作为数据包计费分界点。不幸的是，这会引起许多问题，在某些情况下可能会导致严重的数据包记帐错误。[MPLS-FLOW]讨论了
MPLS flow identification in order to perform a better in-band performance monitoring of user data packets. A method of accomplishing identification is Synonymous Flow Labels (SFLs) introduced in [SFL-FRAMEWORK], while [SYN-FLOW-LABELS] describes performance measurements in RFC 6374 with SFL.
MPLS流识别，以便对用户数据包执行更好的带内性能监控。实现识别的一种方法是[SFL-FRAMEWORK]中介绍的同义流标签（SFL），而[SYN-Flow-Labels]描述了RFC 6374中使用SFL的性能测量。
o Active Performance Measurement: [ALT-MM-AMP] describes how to extend the existing Active Measurement Protocol, in order to implement the Alternate-Marking methodology. [ALT-MM-SLA] describes an extension to the Cisco SLA Protocol Measurement-Type UDP-Measurement.
o 主动性能测量：[ALT-MM-AMP]描述了如何扩展现有的主动测量协议，以实现替代标记方法。[ALT-MM-SLA]描述了Cisco SLA协议测量类型UDP测量的扩展。
An example of implementation and deployment is explained in the next section, just to clarify how the method can work.
下一节将解释一个实现和部署的示例，只是为了阐明该方法如何工作。
The method described in this document, also called Packet Network Performance Monitoring (PNPM), has been invented and engineered in Telecom Italia.
本文件中描述的方法，也称为分组网络性能监测（PNPM），由意大利电信公司发明和设计。
It is important to highlight that the general description of the methodology in this document is a consequence of the operational experiment. The fundamental elements of the technique have been tested, and the lessons learned from the operational experiment inspired the formalization of the Alternate-Marking Method as detailed in the previous sections.
需要强调的是，本文件中对方法的一般描述是操作实验的结果。该技术的基本要素已经过测试，从操作实验中获得的经验教训启发了替代标记方法的形式化，如前几节所述。
The methodology has been used experimentally in Telecom Italia's network and is applied to multicast IPTV channels or other specific traffic flows with high QoS requirements (i.e., Mobile Backhauling traffic realized with a VPN MPLS).
该方法已在意大利电信的网络中进行了实验，并应用于多播IPTV频道或其他具有高QoS要求的特定流量（即，使用VPN MPLS实现的移动回程流量）。
This technology has been employed by leveraging functions and tools available on IP routers, and it's currently being used to monitor packet loss in some portions of Telecom Italia's network. The application of this method for delay measurement has also been evaluated in Telecom Italia's labs.
这项技术已经通过利用IP路由器上可用的功能和工具得到应用，目前正用于监控意大利电信网络某些部分的数据包丢失。意大利电信实验室也评估了这种延迟测量方法的应用。
This section describes how the experiment has been executed, particularly, how the features currently available on existing routing platforms can be used to apply the method, in order to give an example of implementation and deployment.
本节描述了实验是如何执行的，特别是如何使用现有路由平台上当前可用的功能来应用该方法，以便给出实现和部署的示例。
The operational test, described herein, uses the flow-based strategy, as defined in Section 3. Instead, the link-based strategy could be applied to a physical link or a logical link (e.g., an Ethernet VLAN or an MPLS Pseudowire (PW)).
本文所述的运行测试使用第3节中定义的基于流的策略。相反，基于链路的策略可以应用于物理链路或逻辑链路（例如，以太网VLAN或MPLS伪线（PW））。
The implementation of the method leverages the available router functions, since the experiment has been done by a Service Provider (as Telecom Italia is) on its own network. So, with current router implementations, only QoS-related fields and features offer the required flexibility to set bits in the packet header. In case a Service Provider only uses the three most-significant bits of the DSCP field (corresponding to IP Precedence) for QoS classification and queuing, it is possible to use the two least-significant bits of the DSCP field (bit 0 and bit 1) to implement the method without affecting QoS policies. That is the approach used for the experiment. One of the two bits (bit 0) could be used to identify flows subject to traffic monitoring (set to 1 if the flow is under monitoring, otherwise, it is set to 0), while the second (bit 1) can be used for coloring the traffic (switching between values 0 and 1, corresponding to colors A and B) and creating the blocks.
该方法的实现利用了可用的路由器功能，因为该实验是由服务提供商（如意大利电信）在其自己的网络上完成的。因此，在当前的路由器实现中，只有与QoS相关的字段和功能提供了在数据包头中设置位所需的灵活性。如果服务提供商仅使用DSCP字段的三个最高有效位（对应于IP优先级）进行QoS分类和排队，则可以使用DSCP字段的两个最低有效位（位0和位1）来实现该方法，而不影响QoS策略。这就是实验所采用的方法。两位中的一位（位0）可用于识别受流量监控的流量（如果流量正在监控，则设置为1，否则设置为0），而第二位（位1）可用于为流量着色（在值0和1之间切换，对应于颜色A和B）和创建块。
The experiment considers a flow as all the packets sharing the same source IP address or the same destination IP address, depending on the direction. In practice, once the flow has been defined, traffic coloring using the DSCP field can be implemented by configuring an access-list on the router output interface. The access-list intercepts the flow(s) to be monitored and applies a policy to them that sets the DSCP field accordingly. Since traffic coloring has to be switched between the two values over time, the policy needs to be modified periodically. An automatic script is used to perform this task on the basis of a fixed timer. The automatic script is loaded on board of the router and automatizes the basic operations that are needed to realize the methodology.
实验将流视为共享相同源IP地址或相同目标IP地址的所有数据包，具体取决于方向。实际上，一旦定义了流量，就可以通过在路由器输出接口上配置访问列表来实现使用DSCP字段的流量着色。访问列表截取要监视的流，并对其应用相应设置DSCP字段的策略。由于随着时间的推移，流量着色必须在这两个值之间切换，因此需要定期修改策略。自动脚本用于根据固定计时器执行此任务。自动脚本加载到路由器板上，并自动化实现该方法所需的基本操作。
After the traffic is colored using the DSCP field, all the routers on the path can perform the counting. For this purpose, an access-list that matches specific DSCP values can be used to count the packets of the flow(s) being monitored. The same access-list can be installed on all the routers of the path. In addition, network flow monitoring, such as provided by IPFIX [RFC7011], can be used to recognize timestamps of the first/last packet of a batch in order to enable one of the alternatives to measure the delay as detailed in Section 3.3.
使用DSCP字段对流量着色后，路径上的所有路由器都可以执行计数。为此，可以使用与特定DSCP值匹配的访问列表来统计被监视流的数据包。相同的访问列表可以安装在路径的所有路由器上。此外，IPFIX[RFC7011]提供的网络流监控可用于识别批次的第一个/最后一个数据包的时间戳，以使备选方案之一能够测量延迟，如第3.3节所述。
In Telecom Italia's experiment, the timer is set to 5 minutes, so the sequence of actions of the script is also executed every 5 minutes. This value has shown to be a good compromise between measurement frequency and stability of the measurement (i.e., the possibility of collecting all the measures referring to the same block).
在Telecom Italia的实验中，计时器设置为5分钟，因此脚本的操作序列也每5分钟执行一次。该值已证明是测量频率和测量稳定性之间的良好折衷（即，收集涉及同一块的所有测量值的可能性）。
For this experiment, both counters and any other data are collected by using the automatic script that sends these out to an NMS. The NMS is responsible for packet loss calculation, performed by
对于本实验，计数器和任何其他数据都是通过使用自动脚本收集的，该脚本将这些数据发送到NMS。NMS负责分组丢失计算，由
comparing the values of counters from the routers along the flow path(s). A 5-minute timer for color switching is a safe choice for reading the counters and is also coherent with the reporting window of the NMS.
比较流路径上路由器的计数器值。用于颜色切换的5分钟计时器是读取计数器的安全选择，并且与NMS的报告窗口一致。
Note that the use of the DSCP field for marking implies that the method in this case works reliably only within a single management and operation domain.
请注意，使用DSCP字段进行标记意味着本例中的方法仅在单个管理和操作域中可靠地工作。
Lastly, the Telecom Italia experiment scales up to 1000 flows monitored together on a single router, while an implementation on dedicated hardware scales more, but it was tested only in labs for now.
最后，Telecom Italia的实验可以在单个路由器上同时监控1000个流量，而在专用硬件上的实现可以扩展更多，但目前只在实验室进行了测试。
Since a Service Provider application is described here, the method can be applied to end-to-end services supplied to customers. So it is important to highlight that the method MUST be transparent outside the Service Provider domain.
因为这里描述了服务提供者应用程序，所以该方法可以应用于提供给客户的端到端服务。因此，需要强调的是，该方法必须在服务提供者域之外是透明的。
In Telecom Italia's implementation, the source node colors the packets with a policy that is modified periodically via an automatic script in order to alternate the DSCP field of the packets. The nodes between source and destination (included) have to use an access-list to count the colored packets that they receive and forward.
在Telecom Italia的实现中，源节点使用通过自动脚本定期修改的策略对数据包进行着色，以替换数据包的DSCP字段。源和目标（包括）之间的节点必须使用访问列表来统计它们接收和转发的彩色数据包。
Moreover, the destination node has an important role: the colored packets are intercepted and a policy restores and sets the DSCP field of all the packets to the initial value. In this way, the metric is transparent because outside the section of the network under monitoring, the traffic flow is unchanged.
此外，目的地节点还有一个重要的作用：拦截彩色数据包，策略恢复并将所有数据包的DSCP字段设置为初始值。这样，度量是透明的，因为在受监控的网络部分之外，流量是不变的。
In such a case, thanks to this restoring technique, network elements outside the Alternate-Marking monitoring domain (e.g., the two Provider Edge nodes of the Mobile Backhauling VPN MPLS) are totally unaware that packets were marked. So this restoring technique makes Alternate Marking completely transparent outside its monitoring domain.
在这种情况下，由于该恢复技术，备用标记监视域之外的网络元件（例如，移动回程VPN MPLS的两个提供商边缘节点）完全不知道分组被标记。因此，这种恢复技术使备用标记在其监视域之外完全透明。
The method has been explicitly designed for Passive measurements, but it can also be used with Active measurements. In order to have both end-to-end measurements and intermediate measurements (Hybrid measurements), two endpoints can exchange artificial traffic flows and apply Alternate Marking over these flows. In the intermediate
该方法已明确设计用于被动测量，但也可用于主动测量。为了同时具有端到端测量和中间测量（混合测量），两个端点可以交换人工交通流并对这些流应用替代标记。中间
points, artificial traffic is managed in the same way as real traffic and measured as specified before. So the application of the marking method can also simplify the Active measurement, as explained in [ALT-MM-AMP].
人工交通的管理方式与实际交通的管理方式相同，并按照之前的规定进行测量。因此，如[ALT-MM-AMP]所述，标记方法的应用也可以简化主动测量。
RFC 6390 [RFC6390] defines a framework and a process for developing Performance Metrics for protocols above and below the IP layer (such as IP-based applications that operate over reliable or datagram transport protocols).
RFC 6390[RFC6390]定义了一个框架和过程，用于为IP层以上和以下的协议（例如在可靠或数据报传输协议上运行的基于IP的应用程序）开发性能指标。
This document doesn't aim to propose a new Performance Metric but rather a new Method of Measurement for a few Performance Metrics that have already been standardized. Nevertheless, it's worth applying guidelines from [RFC6390] to the present document, in order to provide a more complete and coherent description of the proposed method. We used a combination of the Performance Metric Definition template defined in Section 5.4 of [RFC6390] and the Dependencies laid out in Section 5.5 of that document.
本文件的目的不是提出新的性能指标，而是为一些已经标准化的性能指标提出一种新的测量方法。然而，值得将[RFC6390]中的指南应用到本文件中，以便对所提议的方法提供更完整和一致的描述。我们结合使用了[RFC6390]第5.4节中定义的性能指标定义模板和该文件第5.5节中列出的相关性。
o Metric Name / Metric Description: as already stated, this document doesn't propose any new Performance Metrics. On the contrary, it describes a novel method for measuring packet loss [RFC7680]. The same concept, with small differences, can also be used to measure delay [RFC7679] and jitter [RFC3393]. The document mainly describes the applicability to packet loss measurement.
o 指标名称/指标说明：如前所述，本文件未提出任何新的绩效指标。相反，它描述了一种测量数据包丢失的新方法[RFC7680]。相同的概念（差别很小）也可用于测量延迟[RFC7679]和抖动[RFC3393]。本文件主要描述了数据包丢失测量的适用性。
o Method of Measurement or Calculation: according to the method described in the previous sections, the number of packets lost is calculated by subtracting the value of the counter on the source node from the value of the counter on the destination node. Both counters must refer to the same color. The calculation is performed when the value of the counters is in a steady state. The steady state is an intrinsic characteristic of the marking method counters because the alternation of color makes the counters associated with each color still one at a time for the duration of a marking period.
o 测量或计算方法：根据前面章节中描述的方法，通过从目标节点上的计数器值减去源节点上的计数器值来计算丢失的数据包数。两个计数器必须使用相同的颜色。当计数器的值处于稳定状态时，执行计算。稳定状态是标记方法计数器的固有特征，因为颜色的交替使与每种颜色相关联的计数器在标记期间每次仍然是一个。
o Units of Measurement: the method calculates and reports the exact number of packets sent by the source node and not received by the destination node.
o 度量单位：该方法计算并报告源节点发送而目标节点未接收到的数据包的确切数量。
o Measurement Point(s) with Potential Measurement Domain: the measurement can be performed between adjacent nodes, on a per-link basis, or along a multi-hop path, provided that the traffic under measurement follows that path. In case of a multi-hop path, the measurements can be performed both end-to-end and hop-by-hop.
o 具有潜在测量域的测量点：可以在相邻节点之间、基于每条链路或沿着多跳路径执行测量，前提是测量中的流量遵循该路径。在多跳路径的情况下，可以端到端和逐跳执行测量。
o Measurement Timing: the method has a constraint on the frequency of measurements. This is detailed in Section 3.2, where it is specified that the marking period and the guard band interval are strictly related each other to avoid out-of-order issues. That is because, in order to perform a measurement, the counter must be in a steady state, and this happens when the traffic is being colored with the alternate color. As an example, in the experiment of the method, the time interval is set to 5 minutes, while other optimized implementations can also use a marking period of a few seconds.
o 测量时间：该方法对测量频率有限制。第3.2节对此进行了详细说明，其中规定标记周期和保护带间隔严格相关，以避免出现无序问题。这是因为，为了执行测量，计数器必须处于稳定状态，并且在使用备用颜色对通信量着色时会发生这种情况。例如，在该方法的实验中，时间间隔设置为5分钟，而其他优化实现也可以使用几秒钟的标记周期。
o Implementation: the experiment of the method uses two encodings of the DSCP field to color the packets; this enables the use of policy configurations on the router to color the packets and accordingly configure the counter for each color. The path followed by traffic being measured should be known in advance in order to configure the counters along the path and be able to compare the correct values.
o 实现：该方法的实验使用DSCP字段的两种编码对数据包进行着色；这允许使用路由器上的策略配置为数据包着色，并相应地为每种颜色配置计数器。应提前知道测量流量所遵循的路径，以便沿路径配置计数器并能够比较正确的值。
o Verification: both in the lab and in the operational network, the methodology has been tested and experimented for packet loss and delay measurements by using traffic generators together with precision test instruments and network emulators.
o 验证：在实验室和运营网络中，通过使用流量发生器、精密测试仪器和网络仿真器，对该方法进行了测试和实验，以测量数据包丢失和延迟。
o Use and Applications: the method can be used to measure packet loss with high precision on live traffic; moreover, by combining end-to-end and per-link measurements, the method is useful to pinpoint the single link that is experiencing loss events.
o 用途和应用：该方法可用于实时流量的高精度丢包测量；此外，通过结合端到端和每链路测量，该方法有助于精确定位发生丢失事件的单个链路。
o Reporting Model: the value of the counters has to be sent to a centralized management system that performs the calculations; such samples must contain a reference to the time interval they refer to, so that the management system can perform the correct correlation; the samples have to be sent while the corresponding counter is in a steady state (within a time interval); otherwise, the value of the sample should be stored locally.
o 报告模式：计数器的值必须发送到执行计算的集中管理系统；此类样本必须包含对其所指时间间隔的引用，以便管理系统能够执行正确的关联；必须在相应计数器处于稳定状态（时间间隔内）时发送样本；否则，样本值应存储在本地。
o Dependencies: the values of the counters have to be correlated to the time interval they refer to; moreover, because the experiment of the method is based on DSCP values, there are significant dependencies on the usage of the DSCP field: it must be possible to rely on unused DSCP values without affecting QoS-related configuration and behavior; moreover, the intermediate nodes must not change the value of the DSCP field not to alter the measurement.
o 相关性：计数器的值必须与它们引用的时间间隔相关；此外，由于该方法的实验基于DSCP值，因此对DSCP字段的使用有很大的依赖性：必须能够在不影响QoS相关配置和行为的情况下依赖未使用的DSCP值；此外，中间节点不得改变DSCP字段的值，以免改变测量值。
o Organization of Results: the Method of Measurement produces singletons.
o 结果组织：测量方法产生单粒子。
o Parameters: currently, the main parameter of the method is the time interval used to alternate the colors and read the counters.
o 参数：目前，该方法的主要参数是用于交替颜色和读取计数器的时间间隔。
This document has no IANA actions.
本文档没有IANA操作。
This document specifies a method to perform measurements in the context of a Service Provider's network and has not been developed to conduct Internet measurements, so it does not directly affect Internet security nor applications that run on the Internet. However, implementation of this method must be mindful of security and privacy concerns.
本文件规定了在服务提供商的网络环境中执行测量的方法，但尚未开发用于执行互联网测量，因此它不会直接影响互联网安全或互联网上运行的应用程序。但是，此方法的实现必须考虑安全和隐私问题。
There are two types of security concerns: potential harm caused by the measurements and potential harm to the measurements.
有两种类型的安全问题：由测量引起的潜在危害和对测量的潜在危害。
o Harm caused by the measurement: the measurements described in this document are Passive, so there are no new packets injected into the network causing potential harm to the network itself and to data traffic. Nevertheless, the method implies modifications on the fly to a header or encapsulation of the data packets: this must be performed in a way that doesn't alter the quality of service experienced by packets subject to measurements and that preserves stability and performance of routers doing the measurements. One of the main security threats in OAM protocols is network reconnaissance; an attacker can gather information about the network performance by passively eavesdropping on OAM messages. The advantage of the methods described in this document is that the marking bits are the only information that is exchanged between the network devices. Therefore, Passive eavesdropping on data-plane traffic does not allow attackers to gain information about the network performance.
o 测量造成的危害：本文档中描述的测量是被动的，因此没有新的数据包注入网络，对网络本身和数据流量造成潜在危害。然而，该方法意味着对数据包的报头或封装进行动态修改：这必须以不改变受测量的数据包所经历的服务质量的方式执行，并且保持进行测量的路由器的稳定性和性能。OAM协议的主要安全威胁之一是网络侦察；攻击者可以通过被动窃听OAM消息来收集有关网络性能的信息。本文档中描述的方法的优点是，标记位是网络设备之间交换的唯一信息。因此，对数据平面流量的被动窃听不允许攻击者获得有关网络性能的信息。
o Harm to the Measurement: the measurements could be harmed by routers altering the marking of the packets or by an attacker injecting artificial traffic. Authentication techniques, such as digital signatures, may be used where appropriate to guard against injected traffic attacks. Since the measurement itself may be affected by routers (or other network devices) along the path of IP packets intentionally altering the value of marking bits of packets, as mentioned above, the mechanism specified in this document can be applied just in the context of a controlled domain; thus, the routers (or other network devices) are locally administered and this type of attack can be avoided. In addition, an attacker can't gain information about network performance from
o 对测量的危害：路由器改变数据包的标记或攻击者注入人工流量可能会对测量造成危害。在适当的情况下，可以使用诸如数字签名之类的认证技术来防止注入流量攻击。如上所述，由于测量本身可能受到沿着IP分组路径的路由器（或其他网络设备）的影响，故意改变分组的标记位的值，因此本文件中规定的机制可以仅在受控域的上下文中应用；因此，路由器（或其他网络设备）是本地管理的，可以避免这种类型的攻击。此外，攻击者无法从中获得有关网络性能的信息
a single monitoring point; it must use synchronized monitoring points at multiple points on the path, because they have to do the same kind of measurement and aggregation that Service Providers using Alternate Marking must do.
单一监测点；它必须在路径上的多个点上使用同步监视点，因为它们必须执行与使用备用标记的服务提供商相同的测量和聚合。
The privacy concerns of network measurement are limited because the method only relies on information contained in the header or encapsulation without any release of user data. Although information in the header or encapsulation is metadata that can be used to compromise the privacy of users, the limited marking technique in this document seems unlikely to substantially increase the existing privacy risks from header or encapsulation metadata. It might be theoretically possible to modulate the marking to serve as a covert channel, but it would have a very low data rate if it is to avoid adversely affecting the measurement systems that monitor the marking.
网络测量的隐私问题是有限的，因为该方法只依赖于标头或封装中包含的信息，而不释放任何用户数据。尽管标题或封装中的信息是可用于危害用户隐私的元数据，但本文档中有限的标记技术似乎不太可能大幅增加标题或封装元数据的现有隐私风险。从理论上讲，可以将标记调制为隐蔽通道，但如果要避免对监测标记的测量系统产生不利影响，则其数据速率将非常低。
Delay attacks are another potential threat in the context of this document. Delay measurement is performed using a specific packet in each block, marked by a dedicated color bit. Therefore, a man-in-the-middle attacker can selectively induce synthetic delay only to delay-colored packets, causing systematic error in the delay measurements. As discussed in previous sections, the methods described in this document rely on an underlying time synchronization protocol. Thus, by attacking the time protocol, an attacker can potentially compromise the integrity of the measurement. A detailed discussion about the threats against time protocols and how to mitigate them is presented in RFC 7384 [RFC7384].
延迟攻击是本文档中的另一个潜在威胁。延迟测量使用每个块中的特定数据包执行，该数据包由专用颜色位标记。因此，中间人攻击者只能选择性地诱导合成延迟来延迟彩色数据包，从而导致延迟测量中的系统错误。如前几节所述，本文档中描述的方法依赖于底层时间同步协议。因此，通过攻击时间协议，攻击者可能会破坏测量的完整性。RFC 7384[RFC7384]中详细讨论了针对时间协议的威胁以及如何缓解这些威胁。
[IEEE-1588] IEEE, "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", IEEE Std 1588-2008.
[IEEE-1588]IEEE，“网络测量和控制系统精密时钟同步协议的IEEE标准”，IEEE Std 1588-2008。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，DOI 10.17487/RFC2119，1997年3月<https://www.rfc-editor.org/info/rfc2119>.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393, November 2002, <https://www.rfc-editor.org/info/rfc3393>.
[RFC3393]Demichelis，C.和P.Chimento，“IP性能度量的IP数据包延迟变化度量（IPPM）”，RFC 3393，DOI 10.17487/RFC3393，2002年11月<https://www.rfc-editor.org/info/rfc3393>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, <https://www.rfc-editor.org/info/rfc5905>.
[RFC5905]Mills，D.，Martin，J.，Ed.，Burbank，J.，和W.Kasch，“网络时间协议版本4：协议和算法规范”，RFC 5905，DOI 10.17487/RFC59052010年6月<https://www.rfc-editor.org/info/rfc5905>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January 2016, <https://www.rfc-editor.org/info/rfc7679>.
[RFC7679]Almes，G.，Kalidini，S.，Zekauskas，M.，和A.Morton，Ed.，“IP性能度量（IPPM）的单向延迟度量”，STD 81，RFC 7679，DOI 10.17487/RFC7679，2016年1月<https://www.rfc-editor.org/info/rfc7679>.
[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Loss Metric for IP Performance Metrics (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 2016, <https://www.rfc-editor.org/info/rfc7680>.
[RFC7680]Almes，G.，Kalidini，S.，Zekauskas，M.，和A.Morton，Ed.，“IP性能度量（IPPM）的单向损失度量”，STD 82，RFC 7680，DOI 10.17487/RFC7680，2016年1月<https://www.rfc-editor.org/info/rfc7680>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8174]Leiba，B.，“RFC 2119关键词中大写与小写的歧义”，BCP 14，RFC 8174，DOI 10.17487/RFC8174，2017年5月<https://www.rfc-editor.org/info/rfc8174>.
[ALT-MM-AMP] Fioccola, G., Clemm, A., Bryant, S., Cociglio, M., Chandramouli, M., and A. Capello, "Alternate Marking Extension to Active Measurement Protocol", Work in Progress, draft-fioccola-ippm-alt-mark-active-01, March 2017.
[ALT-MM-AMP]Fioccola，G.，Clemm，A.，Bryant，S.，Cociglio，M.，Chandramouli，M.，和A.Capello，“主动测量协议的替代标记扩展”，正在进行的工作，草稿-Fioccola-ippm-ALT-mark-Active-01，2017年3月。
[ALT-MM-SLA] Fioccola, G., Clemm, A., Cociglio, M., Chandramouli, M., and A. Capello, "Alternate Marking Extension to Cisco SLA Protocol RFC6812", Work in Progress, draft-fioccola-ippm-rfc6812-alt-mark-ext-01, March 2016.
[ALT-MM-SLA]Fioccola，G.，Clemm，A.，Cociglio，M.，Chandramouli，M.，和A.Capello，“思科SLA协议RFC6812的替代标记扩展”，正在进行中，草稿-Fioccola-ippm-RFC6812-ALT-mark-ext-01，2016年3月。
[COLORING] Chen, M., Zheng, L., Mirsky, G., Fioccola, G., and T. Mizrahi, "IP Flow Performance Measurement Framework", Work in Progress, draft-chen-ippm-coloring-based-ipfpm-framework-06, March 2016.
[着色]Chen，M.，Zheng，L.，Mirsky，G.，Fioccola，G.，和T.Mizrahi，“IP流性能测量框架”，正在进行的工作，草稿-Chen-ippm-COLORING-based-ipfpm-Framework-062016年3月。
[IP-FLOW-REPORT] Chen, M., Zheng, L., and G. Mirsky, "IP Flow Performance Measurement Report", Work in Progress, draft-chen-ippm-ipfpm-report-01, April 2016.
[IP-FLOW-REPORT]Chen，M.，Zheng，L.，和G.Mirsky，“IP流量性能测量报告”，在建工程，草稿-Chen-ippm-ipfpm-REPORT-012016年4月。
[IP-MULTICAST-PM] Cociglio, M., Capello, A., Bonda, A., and L. Castaldelli, "A method for IP multicast performance monitoring", Work in Progress, draft-cociglio-mboned-multicast-pm-01, October 2010.
[IP-MULTICAST-PM]Cociglio，M.，Capello，A.，Bonda，A.，和L.Castaldelli，“IP多播性能监控方法”，正在进行的工作，草稿-Cociglio-mboned-MULTICAST-PM-01，2010年10月。
[MPLS-FLOW] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. Mirsky, "MPLS Flow Identification Considerations", Work in Progress, draft-ietf-mpls-flow-ident-06, December 2017.
[MPLS-FLOW]Bryant，S.，Pignataro，C.，Chen，M.，Li，Z.，和G.Mirsky，“MPLS流识别注意事项”，正在进行的工作，草稿-ietf-MPLS-FLOW-ident-062017年12月。
[MULTIPOINT-ALT-MM] Fioccola, G., Cociglio, M., Sapio, A., and R. Sisto, "Multipoint Alternate Marking method for passive and hybrid performance monitoring", Work in Progress, draft-fioccola-ippm-multipoint-alt-mark-01, October 2017.
[MULTIPOINT-ALT-MM]Fioccola，G.，Cociglio，M.，Sapio，A.，和R.Sisto，“被动和混合动力性能监测的多点交替标记方法”，正在进行的工作，草稿-Fioccola-ippm-MULTIPOINT-ALT-mark-012017年10月。
[NVO3-ENCAPS] Boutros, S., Ganga, I., Garg, P., Manur, R., Mizrahi, T., Mozes, D., Nordmark, E., Smith, M., Aldrin, S., and I. Bagdonas, "NVO3 Encapsulation Considerations", Work in Progress, draft-ietf-nvo3-encap-01, October 2017.
[NVO3-ENCAPS]Boutros，S.，Ganga，I.，Garg，P.，Manur，R.，Mizrahi，T.，Mozes，D.，Nordmark，E.，Smith，M.，Aldrin，S.，和I.Bagdonas，“NVO3封装注意事项”，正在进行的工作，草案-ietf-NVO3-encap-01，2017年10月。
[OPSAWG-P3M] Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda, "A packet based method for passive performance monitoring", Work in Progress, draft-tempia-opsawg-p3m-04, February 2014.
[OPSAWG-P3M]卡佩罗，A.，科奇利奥，M.，卡斯塔尔德利，L.，和A.邦达，“基于数据包的被动性能监控方法”，在建工程，草稿-tempia-OPSAWG-P3M-042014年2月。
[PM-MM-BIER] Mirsky, G., Zheng, L., Chen, M., and G. Fioccola, "Performance Measurement (PM) with Marking Method in Bit Index Explicit Replication (BIER) Layer", Work in Progress, draft-ietf-bier-pmmm-oam-03, October 2017.
[PM-MM-BIER]Mirsky，G.，Zheng，L.，Chen，M.，和G.Fioccola，“位索引显式复制（BIER）层中带有标记方法的性能测量（PM）”，正在进行的工作，草稿-ietf-BIER-pmmm-oam-032017年10月。
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006, <https://www.rfc-editor.org/info/rfc4656>.
[RFC4656]Shalunov，S.，Teitelbaum，B.，Karp，A.，Boote，J.，和M.Zekauskas，“单向主动测量协议（OWAMP）”，RFC 4656，DOI 10.17487/RFC4656，2006年9月<https://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, DOI 10.17487/RFC5357, October 2008, <https://www.rfc-editor.org/info/rfc5357>.
[RFC5357]Hedayat，K.，Krzanowski，R.，Morton，A.，Yum，K.，和J.Babiarz，“双向主动测量协议（TWAMP）”，RFC 5357，DOI 10.17487/RFC5357，2008年10月<https://www.rfc-editor.org/info/rfc5357>.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009, <https://www.rfc-editor.org/info/rfc5481>.
[RFC5481]Morton，A.和B.Claise，“数据包延迟变化适用性声明”，RFC 5481，DOI 10.17487/RFC5481，2009年3月<https://www.rfc-editor.org/info/rfc5481>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, DOI 10.17487/RFC6374, September 2011, <https://www.rfc-editor.org/info/rfc6374>.
[RFC6374]Frost，D.和S.Bryant，“MPLS网络的数据包丢失和延迟测量”，RFC 6374，DOI 10.17487/RFC6374，2011年9月<https://www.rfc-editor.org/info/rfc6374>.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New Performance Metric Development", BCP 170, RFC 6390, DOI 10.17487/RFC6390, October 2011, <https://www.rfc-editor.org/info/rfc6390>.
[RFC6390]Clark，A.和B.Claise，“考虑新绩效指标开发的指南”，BCP 170，RFC 6390，DOI 10.17487/RFC6390，2011年10月<https://www.rfc-editor.org/info/rfc6390>.
[RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting IP Network Performance Metrics: Different Points of View", RFC 6703, DOI 10.17487/RFC6703, August 2012, <https://www.rfc-editor.org/info/rfc6703>.
[RFC6703]Morton，A.，Ramachandran，G.，和G.Maguluri，“报告IP网络性能指标：不同观点”，RFC 6703，DOI 10.17487/RFC6703，2012年8月<https://www.rfc-editor.org/info/rfc6703>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013, <https://www.rfc-editor.org/info/rfc7011>.
[RFC7011]Claise，B.，Ed.，Trammell，B.，Ed.，和P.Aitken，“流量信息交换的IP流量信息导出（IPFIX）协议规范”，STD 77，RFC 7011，DOI 10.17487/RFC7011，2013年9月<https://www.rfc-editor.org/info/rfc7011>.
[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. Weingarten, "An Overview of Operations, Administration, and Maintenance (OAM) Tools", RFC 7276, DOI 10.17487/RFC7276, June 2014, <https://www.rfc-editor.org/info/rfc7276>.
[RFC7276]Mizrahi，T.，Sprecher，N.，Bellagamba，E.，和Y.Weingarten，“运营、管理和维护（OAM）工具概述”，RFC 7276，DOI 10.17487/RFC72762014年6月<https://www.rfc-editor.org/info/rfc7276>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC7384]Mizrahi，T.，“分组交换网络中时间协议的安全要求”，RFC 7384，DOI 10.17487/RFC7384，2014年10月<https://www.rfc-editor.org/info/rfc7384>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC7799]Morton，A.“主动和被动度量和方法（介于两者之间的混合类型）”，RFC 7799，DOI 10.17487/RFC7799，2016年5月<https://www.rfc-editor.org/info/rfc7799>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non-MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 2018, <https://www.rfc-editor.org/info/rfc8296>.
[RFC8296]Wijnands，IJ.，Ed.，Rosen，E.，Ed.，Dolganow，A.，Tantsura，J.，Aldrin，S.，和I.Meilik，“MPLS和非MPLS网络中位索引显式复制（BIER）的封装”，RFC 8296，DOI 10.17487/RFC8296，2018年1月<https://www.rfc-editor.org/info/rfc8296>.
[SFL-FRAMEWORK] Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., and G. Mirsky, "Synonymous Flow Label Framework", Work in Progress, draft-ietf-mpls-sfl-framework-00, August 2017.
[SFL-FRAMEWORK]Bryant，S.，Chen，M.，Li，Z.，Swallow，G.，Sivabalan，S.，和G.Mirsky，“同义流标签框架”，正在进行的工作，草稿-ietf-mpls-SFL-FRAMEWORK-00，2017年8月。
[SYN-FLOW-LABELS] Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., Mirsky, G., and G. Fioccola, "RFC6374 Synonymous Flow Labels", Work in Progress, draft-ietf-mpls-rfc6374-sfl-01, December 2017.
[SYN-FLOW-LABERS]Bryant，S.，Chen，M.，Li，Z.，Swallow，G.，Sivabalan，S.，Mirsky，G.，和G.Fioccola，“RFC6374同义流量标签”，正在进行中的工作，草稿-ietf-mpls-RFC6374-sfl-01，2017年12月。
Acknowledgements
致谢
The previous IETF specifications describing this technique were: [IP-MULTICAST-PM] and [OPSAWG-P3M].
先前描述该技术的IETF规范为：[IP-MULTICAST-PM]和[OPSAWG-P3M]。
The authors would like to thank Alberto Tempia Bonda, Domenico Laforgia, Daniele Accetta, and Mario Bianchetti for their contribution to the definition and the implementation of the method.
作者要感谢Alberto Tempia Bonda、Domenico Laforgia、Daniele Accetta和Mario Bianchetti对该方法的定义和实施所做的贡献。
The authors would also thank Spencer Dawkins, Carlos Pignataro, Brian Haberman, and Eric Vyncke for their assistance and their detailed and precious reviews.
作者还要感谢斯宾塞·道金斯（Spencer Dawkins）、卡洛斯·皮格纳塔罗（Carlos Pignataro）、布莱恩·哈伯曼（Brian Haberman）和埃里克·温克（Eric Vyncke）的帮助以及他们详细而宝贵的评论。
Authors' Addresses
作者地址
Giuseppe Fioccola (editor) Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy
Giuseppe Fioccola（编辑）意大利电信通过Reiss Romoli，274都灵10148意大利
Email: giuseppe.fioccola@telecomitalia.it
Email: giuseppe.fioccola@telecomitalia.it
Alessandro Capello Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy
亚历山德罗·卡佩罗（Alessandro Capello）通过里斯·罗莫利（Reiss Romoli）向意大利电信公司发送，意大利都灵274 10148
Email: alessandro.capello@telecomitalia.it
Email: alessandro.capello@telecomitalia.it
Mauro Cociglio Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy
Mauro Cociglio Telecom Italia Via Reiss Romoli，274都灵10148意大利
Email: mauro.cociglio@telecomitalia.it
Email: mauro.cociglio@telecomitalia.it
Luca Castaldelli Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy
卢卡·卡斯塔尔德利意大利电信公司Via Reiss Romoli，274都灵10148意大利
Email: luca.castaldelli@telecomitalia.it
Email: luca.castaldelli@telecomitalia.it
Mach(Guoyi) Chen Huawei Technologies
马赫（国一）陈华为技术有限公司
Email: mach.chen@huawei.com
Email: mach.chen@huawei.com
Lianshu Zheng Huawei Technologies
华为技术有限公司
Email: vero.zheng@huawei.com
Email: vero.zheng@huawei.com
Greg Mirsky ZTE United States of America
格雷格·米尔斯基美国中兴通讯
Email: gregimirsky@gmail.com
Email: gregimirsky@gmail.com
Tal Mizrahi Marvell 6 Hamada St. Yokneam Israel
Tal Mizrahi Marvell 6 Hamada St.Yokneam以色列
Email: talmi@marvell.com
Email: talmi@marvell.com