Network Working Group R. Koodli
Request for Comments: 3357 Nokia Research Center
Category: Informational R. Ravikanth
Axiowave
August 2002
Network Working Group R. Koodli
Request for Comments: 3357 Nokia Research Center
Category: Informational R. Ravikanth
Axiowave
August 2002
One-way Loss Pattern Sample Metrics
单向损失模式样本度量
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2002). All Rights Reserved.
版权所有（C）互联网协会（2002年）。版权所有。
Abstract
摘要
Using the base loss metric defined in RFC 2680, this document defines two derived metrics "loss distance" and "loss period", and the associated statistics that together capture loss patterns experienced by packet streams on the Internet. The Internet exhibits certain specific types of behavior (e.g., bursty packet loss) that can affect the performance seen by the users as well as the operators. The loss pattern or loss distribution is a key parameter that determines the performance observed by the users for certain real-time applications such as packet voice and video. For the same loss rate, two different loss distributions could potentially produce widely different perceptions of performance.
使用RFC 2680中定义的基本损失度量，本文档定义了两个衍生度量“损失距离”和“损失周期”，以及相关统计数据，它们共同捕获互联网上数据包流所经历的损失模式。互联网表现出某些特定类型的行为（例如突发性数据包丢失），这些行为会影响用户和运营商看到的性能。丢失模式或丢失分布是一个关键参数，它决定了用户在某些实时应用（如分组语音和视频）中观察到的性能。对于相同的损失率，两种不同的损失分布可能会产生截然不同的绩效感知。
Table of Contents
目录
1. Introduction 3
2. Terminology 3
3. The Approach 3
4. Basic Definitions 4
5. Definitions for Samples of One-way Loss Distance, and One-way
Loss Period 5
5.1. Metric Names . . . . . . . . . . . . . . . . . . . . . . 5
5.1.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 5
5.1.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 5
5.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 5
5.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . 5
5.3.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 5
5.3.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 5
5.4. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
5.4.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 6
5.4.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 6
5.4.3. Examples . . . . . . . . . . . . . . . . . . . . 6
5.5. Methodologies . . . . . . . . . . . . . . . . . . . . . . 7
5.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . 8
5.7. Sampling Considerations . . . . . . . . . . . . . . . . . 8
5.8. Errors and Uncertainties . . . . . . . . . . . . . . . . 8
6. Statistics 9
6.1. Type-P-One-Way-Loss-Noticeable-Rate . . . . . . . . . . . 9
6.2. Type-P-One-Way-Loss-Period-Total . . . . . . . . . . . . 9
6.3. Type-P-One-Way-Loss-Period-Lengths . . . . . . . . . . . 10
6.4. Type-P-One-Way-Inter-Loss-Period-Lengths . . . . . . . . 10
6.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations 11
7.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 12
7.2. Privacy / Confidentiality . . . . . . . . . . . . . . . . 12
7.3. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations 12
9. Acknowledgements 12
10. Normative References 12
11. Informative References 13
Authors' Addresses 14
Full Copyright Statement 15
1. Introduction 3
2. Terminology 3
3. The Approach 3
4. Basic Definitions 4
5. Definitions for Samples of One-way Loss Distance, and One-way
Loss Period 5
5.1. Metric Names . . . . . . . . . . . . . . . . . . . . . . 5
5.1.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 5
5.1.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 5
5.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 5
5.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . 5
5.3.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 5
5.3.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 5
5.4. Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
5.4.1. Type-P-One-Way-Loss-Distance-Stream . . . . . . . 6
5.4.2. Type-P-One-Way-Loss-Period-Stream . . . . . . . . 6
5.4.3. Examples . . . . . . . . . . . . . . . . . . . . 6
5.5. Methodologies . . . . . . . . . . . . . . . . . . . . . . 7
5.6. Discussion . . . . . . . . . . . . . . . . . . . . . . . 8
5.7. Sampling Considerations . . . . . . . . . . . . . . . . . 8
5.8. Errors and Uncertainties . . . . . . . . . . . . . . . . 8
6. Statistics 9
6.1. Type-P-One-Way-Loss-Noticeable-Rate . . . . . . . . . . . 9
6.2. Type-P-One-Way-Loss-Period-Total . . . . . . . . . . . . 9
6.3. Type-P-One-Way-Loss-Period-Lengths . . . . . . . . . . . 10
6.4. Type-P-One-Way-Inter-Loss-Period-Lengths . . . . . . . . 10
6.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations 11
7.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 12
7.2. Privacy / Confidentiality . . . . . . . . . . . . . . . . 12
7.3. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations 12
9. Acknowledgements 12
10. Normative References 12
11. Informative References 13
Authors' Addresses 14
Full Copyright Statement 15
In certain real-time applications (such as packet voice and video), the loss pattern or loss distribution is a key parameter that determines the performance observed by the users. For the same loss rate, two different loss distributions could potentially produce widely different perceptions of performance. The impact of loss pattern is also extremely important for non-real-time applications that use an adaptive protocol such as TCP. Refer to [4], [5], [6], [11] for evidence as to the importance and existence of loss burstiness and its effect on packet voice and video applications.
在某些实时应用（如分组语音和视频）中，丢失模式或丢失分布是决定用户观察到的性能的关键参数。对于相同的损失率，两种不同的损失分布可能会产生截然不同的绩效感知。对于使用自适应协议（如TCP）的非实时应用程序，丢失模式的影响也非常重要。请参阅[4]、[5]、[6]、[11]以获取关于丢失突发性的重要性和存在及其对分组语音和视频应用的影响的证据。
Previously, the focus of the IPPM had been on specifying base metrics such as delay, loss and connectivity under the framework described in RFC 2330. However, specific Internet behaviors can also be captured under the umbrella of the IPPM framework, specifying new concepts while reusing existing guidelines as much as possible. In this document, we propose two derived metrics, called "loss distance" and "loss period", with associated statistics, to capture packet loss patterns. The loss period metric captures the frequency and length (burstiness) of loss once it starts, and the loss distance metric captures the spacing between the loss periods. It is important to note that these metrics are derived based on the base metric Type-P-One-Way-packet-Loss.
在此之前，IPPM的重点是在RFC 2330中描述的框架下指定基本指标，如延迟、损失和连接。然而，特定的互联网行为也可以在IPPM框架下捕获，在尽可能重用现有指南的同时指定新概念。在本文中，我们提出了两个派生的度量，称为“丢失距离”和“丢失周期”，以及相关的统计信息，以捕获数据包丢失模式。损耗周期度量捕获损耗开始后的频率和长度（突发性），损耗距离度量捕获损耗周期之间的间隔。需要注意的是，这些度量是基于基本度量类型P-单向-分组丢失导出的。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and "silently ignore" in this document are to be interpreted as described in BCP 14, RFC 2119 [2].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不得”、“应”、“不应”、“建议”、“可”、“可选”和“无声忽略”应按照BCP 14、RFC 2119[2]中的说明进行解释。
This document closely follows the guidelines specified in [3]. Specifically, the concepts of singleton, sample, statistic, measurement principles, Type-P packets, as well as standard-formed packets all apply. However, since the document proposes to capture specific Internet behaviors, modifications to the sampling process MAY be needed. Indeed, this is mentioned in [1], where it is noted that alternate sampling procedures may be useful depending on specific circumstances. This document proposes that the specific behaviors be captured as "derived" metrics from the base metrics the behaviors are related to. The reasons for adopting this position are the following:
本文件严格遵循[3]中规定的指南。具体来说，单例、样本、统计、测量原理、P型数据包以及标准格式数据包的概念都适用。但是，由于该文件建议捕获特定的互联网行为，因此可能需要对采样过程进行修改。事实上，在[1]中提到了这一点，其中指出，根据具体情况，替代取样程序可能是有用的。本文档建议将特定行为捕获为与行为相关的基本度量的“派生”度量。采取这一立场的原因如下：
- it provides consistent usage of singleton metric definition for different behaviors (e.g., a single definition of packet loss is needed for capturing burst of losses, 'm out of n' losses etc.)
- 它为不同的行为提供了单例度量定义的一致使用（例如，捕获突发性丢失、“n中取m”丢失等时需要一个包丢失定义）
- it allows re-use of the methodologies specified for the singleton metric with modifications whenever necessary
- 它允许重复使用为单例度量指定的方法，并在必要时进行修改
- it clearly separates few base metrics from many Internet behaviors
- 它清楚地将一些基本指标与许多互联网行为区分开来
Following the guidelines in [3], this translates to deriving sample metrics from the respective singletons. The process of deriving sample metrics from the singletons is specified in [3], [1], and others.
按照[3]中的指导原则，这转化为从相应的单例中导出样本度量。[3]、[1]等中规定了从单例中导出样本度量的过程。
In the following sections, we apply this approach to a particular Internet behavior, namely the packet loss process.
在以下部分中，我们将此方法应用于特定的Internet行为，即数据包丢失过程。
Sequence number: Consecutive packets in a time series sample are given sequence numbers that are consecutive integers. This document does not specify exactly how to associate sequence numbers with packets. The sequence numbers could be contained within test packets themselves, or they could be derived through post-processing of the sample.
序列号：时间序列样本中的连续数据包是给定的连续整数序列号。本文档没有具体说明如何将序列号与数据包相关联。序列号可以包含在测试包本身中，也可以通过对样本的后处理得到。
Bursty loss: The loss involving consecutive packets of a stream.
突发性丢失：涉及流的连续数据包的丢失。
Loss Distance: The difference in sequence numbers of two successively lost packets which may or may not be separated by successfully received packets.
丢失距离：两个连续丢失的数据包序列号的差异，成功接收的数据包可能会或可能不会将它们分开。
Example: In a packet stream, the packet with sequence number 20 is considered lost, followed by the packet with sequence number 50. The loss distance is 30.
示例：在分组流中，序列号为20的分组被视为丢失，随后是序列号为50的分组。损失距离为30。
Loss period: Let P_i be the i'th packet. Define f(P_i) = 1 if P_i is
lost, 0 otherwise. Then, a loss period begins if
f(P_i) = 1 and f(P_(i-1)) = 0
Loss period: Let P_i be the i'th packet. Define f(P_i) = 1 if P_i is
lost, 0 otherwise. Then, a loss period begins if
f(P_i) = 1 and f(P_(i-1)) = 0
Example: Consider the following sequence of lost (denoted by x) and received (denoted by r) packets.
示例：考虑丢失的序列（由x表示）和接收（由R表示）分组。
r r r x r r x x x r x r r x x x
r r x r x x r x r x r x x r x x x x
Then, with `i' assigned as follows, 1 1 1 1 1 1 i: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
然后，将'i'赋值如下，111i:012345678890123445
f(P_i) is,
f（P_i）是，
f(P_i): 0 0 0 1 0 0 1 1 1 0 1 0 0 1 1 1
f（P_i）：01 01 01 01 01 01
and there are four loss periods in the above sequence beginning at P_3, P_6, P_10, and P_13.
在上述顺序中有四个损失期，从pU3、pU6、pU10和pU13开始。
5. Definitions for Samples of One-way Loss Distance, and One-way Loss Period
5. 单向损耗距离和单向损耗周期样本的定义
Src, the IP address of a host
Src，主机的IP地址
Dst, the IP address of a host
Dst，主机的IP地址
T0, a time
T0，一次
Tf, a time
Tf，一次
lambda, a rate of any sampling method chosen in reciprocal of seconds
λ，以秒的倒数选择的任何采样方法的速率
A sequence of pairs of the form <loss distance, loss>, where loss is derived from the sequence of <time, loss> in [1], and loss distance is either zero or a positive integer.
一种形式为<loss distance，loss>的成对序列，其中损耗由[1]中的<time，loss>序列推导而来，损耗距离为零或正整数。
A sequence of pairs of the form <loss period, loss>, where loss is derived from the sequence of <time, loss> in [1], and loss period is an integer.
一种形式为<loss period，loss>的成对序列，其中loss由[1]中的<time，loss>序列推导而来，loss period为整数。
When a packet is considered lost (using the definition in [1]), we look at its sequence number and compare it with that of the previously lost packet. The difference is the loss distance between the lost packet and the previously lost packet. The sample would consist of <loss distance, loss> pairs. This definition assumes that sequence numbers of successive test packets increase monotonically by one. The loss distance associated with the very first packet loss is considered to be zero.
当一个数据包被认为丢失时（使用[1]中的定义），我们查看它的序列号，并将其与先前丢失的数据包的序列号进行比较。差异是丢失的数据包和以前丢失的数据包之间的丢失距离。样本将由<loss distance，loss>对组成。该定义假设连续测试数据包的序列号单调增加1。与第一个分组丢失相关联的丢失距离被认为是零。
The sequence number of a test packet can be derived from the timeseries sample collected by performing the loss measurement according to the methodology in [1]. For example, if a loss sample consists of <T0,0>, <T1,0>, <T2,1>, <T3,0>, <T4,0>, the sequence numbers of the five test packets sent at T0, T1, T2, T3, and T4 can be 0, 1, 2, 3 and 4 respectively, or 100, 101, 102, 103 and 104 respectively, etc.
测试数据包的序列号可以从根据[1]中的方法进行损耗测量所收集的时间序列样本中得出。例如，如果丢失样本由<T0,0>、<T1,0>、<T2,1>、<T3,0>、<T4,0>组成，则在T0、T1、T2、T3和T4处发送的五个测试分组的序列号可以分别为0、1、2、3和4，或者分别为100、101、102、103和104，以此类推。
We start a counter 'n' at an initial value of zero. This counter is incremented by one each time a lost packet satisfies the definition outlined in 4. The metric is defined as <loss period, loss> where "loss" is derived from the sequence of <time, loss> in Type-P-One-Way-Loss-Stream [1], and loss period is set to zero when "loss" is zero in Type-P-One-Way-Loss-Stream, and loss period is set to 'n' (above) when "loss" is one in Type-P-One-Way-Loss-Stream.
我们在初始值为零时启动计数器“n”。每当丢失的数据包满足4中所述的定义时，该计数器将递增一。该度量定义为<loss period，loss>，其中“loss”源自P-One-Way-loss-Stream[1]类型中的<time，loss>序列，当P-One-Way-loss-Stream中的“loss”为零时，loss period设置为零，当P-One-Way-loss-Stream中的“loss”为一时，loss period设置为“n”（如上）。
Essentially, when a packet is lost, the current value of "n" indicates the loss period to which this packet belongs. For a packet that is received successfully, the loss period is defined to be zero.
基本上，当数据包丢失时，“n”的当前值指示该数据包所属的丢失周期。对于成功接收的数据包，丢失周期定义为零。
Let the following set of pairs represent a Type-P-One-Way-Loss-Stream.
让下面的一组对表示一个类型-P-单向-Loss-Stream。
{<T1,0>,<T2,1>,<T3,0>,<T4,0>,<T5,1>,<T6,0>,<T7,1>,<T8,0>,
<T9,1>,<T10,1>}
{<T1,0>,<T2,1>,<T3,0>,<T4,0>,<T5,1>,<T6,0>,<T7,1>,<T8,0>,
<T9,1>,<T10,1>}
where T1, T2,..,T10 are in increasing order.
其中T1，T2，…，T10按递增顺序排列。
Packets sent at T2, T5, T7, T9, T10 are lost. The two derived metrics can be obtained from this sample as follows.
在T2、T5、T7、T9、T10发送的数据包丢失。这两个衍生指标可从该样本中获得，如下所示。
(i) Type-P-One-Way-Loss-Distance-Stream:
(i) P型-单向-损耗-距离-流：
Since packet 2 is the first lost packet, the associated loss distance is zero. For the next lost packet (packet 5), loss distance is 5-2 or 3. Similarly, for the remaining lost packets (packets 7, 9, and 10) their loss distances are 2, 2, and 1 respectively. Therefore, the Type-P-One-Way-Loss-Distance-Stream is:
由于分组2是第一个丢失的分组，因此相关的丢失距离为零。对于下一个丢失的数据包（数据包5），丢失距离为5-2或3。类似地，对于其余丢失的分组（分组7、9和10），其丢失距离分别为2、2和1。因此，P-单向-损耗-距离-流类型为：
{<0,0>,<0,1>,<0,0>,<0,0>,<3,1>,<0,0>,<2,1>,<0,0>,<2,1>,<1,1>}
{<0,0>,<0,1>,<0,0>,<0,0>,<3,1>,<0,0>,<2,1>,<0,0>,<2,1>,<1,1>}
(ii) The Type-P-One-Way-Loss-Period-Stream:
（ii）P型单向损失周期流：
The packet 2 sets the counter 'n' to 1, which is incremented by one for packets 5, 7 and 9 according to the definition in 4. However, for packet 10, the counter remains at 4, again satisfying the definition in 4. Thus, the Type-P-One-Way-Loss-Period-Stream is:
数据包2将计数器“n”设置为1，根据4中的定义，对于数据包5、7和9，计数器“n”增加1。然而，对于包10，计数器保持在4，再次满足4中的定义。因此，P-单向损失-周期-流类型为：
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>}
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>}
The same methodology outlined in [1] can be used to conduct the sample experiments. A synopsis is listed below.
[1]中概述的相同方法可用于进行样品实验。下面列出了一个概要。
Generally, for a given Type-P, one possible methodology would proceed as follows:
通常，对于给定的P型，一种可能的方法如下：
- Assume that Src and Dst have clocks that are synchronized with each other. The degree of synchronization is a parameter of the methodology, and depends on the threshold used to determine loss (see below).
- 假设Src和Dst具有相互同步的时钟。同步程度是该方法的一个参数，取决于用于确定损失的阈值（见下文）。
- At the Src host, select Src and Dst IP addresses, and form a test packet of Type-P with these addresses.
- 在Src主机上，选择Src和Dst IP地址，并使用这些地址形成类型为P的测试数据包。
- At the Dst host, arrange to receive the packet.
- 在Dst主机上，安排接收数据包。
- At the Src host, place a timestamp in the prepared Type-P packet, and send it towards Dst.
- 在Src主机上，在准备好的Type-P数据包中放置一个时间戳，并将其发送到Dst。
- If the packet arrives within a reasonable period of time, the one-way packet-loss is taken to be zero.
- 如果数据包在合理的时间段内到达，则单向数据包丢失被视为零。
- If the packet fails to arrive within a reasonable period of time, the one-way packet-loss is taken to be one. Note that the threshold of "reasonable" here is a parameter of the methodology.
- 如果数据包未能在合理的时间段内到达，则单向数据包丢失被视为1。请注意，此处的“合理”阈值是该方法的一个参数。
The Loss-Distance-Stream metric allows one to study the separation between packet losses. This could be useful in determining a "spread factor" associated with the packet loss rate. In conjunction, the Loss-Period-Stream metric allows the study of loss burstiness for each occurrence of loss. A single loss period of length 'n' can account for a significant portion of the overall loss rate. Note that it is possible to measure distance between loss bursts separated by one or more successfully received packets. (Refer to Sections 6.4 and 6.5).
丢失距离流度量允许我们研究分组丢失之间的分离。这可用于确定与分组丢失率相关联的“扩展因子”。同时，损失周期流指标允许研究每次损失发生时的损失突发性。长度为“n”的单个损失期可占整体损失率的很大一部分。注意，可以测量由一个或多个成功接收的数据包分隔的丢失突发之间的距离。（参考第6.4节和第6.5节）。
The proposed metrics can be used independent of the particular sampling method used. We note that Poisson sampling may not yield appropriate values for these metrics for certain real-time applications such as voice over IP, as well as to TCP-based applications. For real-time applications, it may be more appropriate to use the ON-OFF [10] model, in which an ON period starts with a certain probability 'p', during which a certain number of packets are transmitted with mean 'lambda-on' according to geometric distribution and an OFF period starts with probability '1-p' and lasts for a period of time based on exponential distribution with rate 'lambda-off'.
所提出的度量可以独立于所使用的特定抽样方法来使用。我们注意到，对于某些实时应用程序（如IP语音）以及基于TCP的应用程序，泊松采样可能无法为这些度量生成适当的值。对于实时应用，可能更适合使用开-关[10]模型，其中开周期以一定概率“p”开始，在此期间，一定数量的数据包根据几何分布以平均值“λ开”进行传输，而关闭周期以概率“1-p”开始，并持续一段时间，基于指数分布，速率为“λ关”。
For TCP-based applications, one may use the model proposed in [8]. See [9] for an application of the model.
对于基于TCP的应用程序，可以使用[8]中提出的模型。有关模型的应用，请参见[9]。
The measurement aspects, including the packet size, loss threshold, type of the test machine chosen etc, invariably influence the packet loss metric itself and hence the derived metrics described in this document. Thus, when making an assessment of the results pertaining to the metrics outlined in this document, attention must be paid to these matters. See [1] for a detailed consideration of errors and uncertainties regarding the measurement of base packet loss metric.
测量方面，包括数据包大小、丢失阈值、选择的测试机器类型等，都会影响数据包丢失度量本身，从而影响本文档中描述的导出度量。因此，在评估与本文件中概述的指标相关的结果时，必须注意这些事项。有关基本分组丢失度量测量的错误和不确定性的详细考虑，请参见[1]。
Define loss of a packet to be "noticeable" [7] if the distance between the lost packet and the previously lost packet is no greater than delta, a positive integer, where delta is the "loss constraint".
如果丢失的数据包和先前丢失的数据包之间的距离不大于正整数delta，则将数据包丢失定义为“明显的”[7]，其中delta是“丢失约束”。
Example: Let delta = 99. Let us assume that packet 50 is lost followed by a bursty loss of length 3 starting from packet 125. All the three losses starting from packet 125 are noticeable.
示例：让delta=99。让我们假设数据包50丢失，随后是从数据包125开始的长度为3的突发性丢失。从数据包125开始的所有三个丢失都是明显的。
Given a Type-P-One-Way-Loss-Distance-Stream, this statistic can be computed simply as the number of losses that violate some constraint delta, divided by the number of losses. (Alternatively, it can also be defined as the number of "noticeable losses" to the number of successfully received packets). This statistic is useful when the actual distance between successive losses is important. For example, many multimedia codecs can sustain losses by "concealing" the effect of loss by making use of past history information. Their ability to do so degrades with poor history resulting from losses separated by close distances. By choosing delta based on this sensitivity, one can measure how "noticeable" a loss might be for quality purposes. The noticeable loss requires a certain "spread factor" for losses in the timeseries. In the above example where loss constraint is equal to 99, a loss rate of one percent with a spread of 100 between losses (e.g., 100, 200, 300, 400, 500 out of 500 packets) may be more desirable for some applications compared to the same loss rate with a spread that violates the loss constraint (e.g., 100, 175, 275, 290, 400: losses occurring at 175 and 290 violate delta = 99).
给定一个P型单向损耗距离流，该统计数据可以简单地计算为违反某个约束增量的损耗数除以损耗数。（或者，它也可以定义为成功接收的数据包数量的“明显损失”数量）。当连续损失之间的实际距离很重要时，此统计数据很有用。例如，许多多媒体编解码器可以通过利用过去的历史信息“隐藏”丢失的影响来承受丢失。他们这样做的能力下降，因为距离较近的损失导致历史记录不佳。通过基于此灵敏度选择增量，可以测量损失对质量的影响程度。明显的损失要求时间序列中的损失具有一定的“扩散系数”。在上面的示例中，在丢失约束等于99的情况下，对于某些应用而言，与具有违反丢失约束的扩展的相同丢失率相比，具有100%的丢失率（例如，500个分组中的100、200、300、400、500个）可能更为理想（例如，100、175、275、290、400：在175和290处发生的损失delta=99）。
This represents the total number of loss periods, and can be derived from the loss period metric Type-P-One-Way-Loss-Period-Stream as follows:
这表示损失期的总数，可以从损失期度量Type-P-One-Way-loss-period-Stream中导出，如下所示：
Type-P-One-Way-Loss-Period-Total = maximum value of the first entry of the set of pairs, <loss period, loss>, representing the loss metric Type-P-One-Way-Loss-Period-Stream.
Type-P-One-Way-Loss-Period-Total=一组对的第一个条目的最大值，<Loss Period，Loss>，表示P-One-Way-Loss-Period-Stream类型的损失度量。
Note that this statistic does not describe the duration of each loss period itself. If this statistic is large, it does not mean that the losses are more spread out than they are otherwise; one or more loss periods may include bursty losses. This statistic is generally useful in gathering first order approximation of loss spread.
请注意，此统计数据并不描述每个损失期本身的持续时间。如果这一统计数字很大，并不意味着损失比其他情况下更分散；一个或多个损失期可能包括突发性损失。该统计数据通常用于收集损失扩散的一阶近似值。
This statistic is a sequence of pairs <loss period, length>, with the "loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total. Thus the total number of pairs in this statistic equals Type-P-One-Way-Loss-Period-Total. In each pair, the "length" is obtained by counting the number of pairs, <loss period, loss>, in the metric Type-P-One-Way-Loss-Period-Stream which have their first entry equal to "loss period."
此统计数据是成对的序列<损失期，长度>，“损失期”条目范围为1-类型-P-单向-loss-period-Total。因此，该统计中的总对数等于Type-P-One-Way-Loss-Period-total。在每一对中，“长度”是通过计算公制类型-P-单向-loss-period-流中第一个条目等于“loss period”的对数<loss period，loss>获得的
Since this statistic represents the number of packets lost in each loss period, it is an indicator of burstiness of each loss period. In conjunction with loss-period-total statistic, this statistic is generally useful in observing which loss periods are potentially more influential than others from a quality perspective.
由于此统计数据表示每个丢失周期中丢失的数据包数，因此它是每个丢失周期突发性的指示器。结合损失期总统计，该统计通常有助于从质量角度观察哪些损失期可能比其他损失期更有影响。
This statistic measures distance between successive loss periods. It takes the form of a set of pairs <loss period, inter-loss-period-length>, with the "loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total, and "inter-loss-period-length" is the loss distance between the last packet considered lost in "loss period" 'i-1', and the first packet considered lost in "loss period" 'i', where 'i' ranges from 2 to Type-P-One-Way-Loss-Period-Total. The "inter-loss-period-length" associated with the first "loss period" is defined to be zero.
该统计数据测量连续损失期之间的距离。它采用一组对的形式<丢失周期，内部丢失周期长度>，“丢失周期”条目范围为1-类型-P-单向-loss-period-Total，“内部丢失周期长度”是在“丢失周期”'i-1'中被认为丢失的最后一个数据包与在“丢失周期”'i'中被认为丢失的第一个数据包之间的丢失距离，其中“i”的范围从2到P型-单向-损失-周期-总计。与第一个“损失期”相关的“损失期间长度”定义为零。
This statistic allows one to consider, for example, two loss periods each of length greater than one (implying loss burst), but separated by a distance of 2 to belong to the same loss burst if such a consideration is deemed useful. When the Inter-Loss-Period-Length between two bursty loss periods is smaller, it could affect the loss concealing ability of multimedia codecs since there is relatively smaller history. When it is larger, an application may be able to rebuild its history which could dampen the effect of an impending loss (period).
该统计允许考虑例如两个损失周期，每个长度大于一个（意味着损失突发），但是如果认为这样的考虑被认为有用，则间隔2的距离属于相同的损失突发。当两个突发性丢失周期之间的间隔丢失周期长度较小时，由于历史记录相对较小，可能会影响多媒体编解码器的丢失隐藏能力。当它更大时，应用程序可能能够重建其历史记录，这可能会减弱即将发生的损失（周期）的影响。
We continue with the same example as in Section 5.4.3. The three statistics defined above will have the following values.
我们继续使用与第5.4.3节相同的示例。上面定义的三个统计数据将具有以下值。
- Let delta = 2. In Type-P-One-Way-Loss-Distance-Stream
- 设δ=2。在类型P中，单向损耗距离流
{<0,0>,<0,1>,<0,0>,<0,0>,<3,1>,<0,0>,<2,1>,<0,0>,<2,1>,<1,1>},
{<0,0>,<0,1>,<0,0>,<0,0>,<3,1>,<0,0>,<2,1>,<0,0>,<2,1>,<1,1>},
there are 3 loss distances that violate the delta of 2. Thus, Type-P-One-Way-Loss-Noticeable-Rate = 3/5 ((number of noticeable losses)/(number of total losses))
有3个损耗距离违反了2的增量。因此，类型-P-单向损失-显著损失率=3/5（（显著损失数）/（总损失数））
- In Type-P-One-Way-Loss-Period-Stream
- 在P型单向损耗周期流中
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
the largest of the first entry in the sequence of <loss period,loss> pairs is 4. Thus,
<loss period，loss>对序列中第一个条目的最大值为4。因此
Type-P-One-Way-Loss-Period-Total = 4
Type-P-One-Way-Loss-Period-Total = 4
- In Type-P-One-Way-Loss-Period-Stream
- 在P型单向损耗周期流中
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
the lengths of individual loss periods are 1, 1, 1 and 2 respectively. Thus,
各损失期的长度分别为1、1、1和2。因此
Type-P-One-Way-Loss-Period-Lengths =
P型单向损耗周期长度=
{<1,1>,<2,1>,<3,1>,<4,2>}
{<1,1>,<2,1>,<3,1>,<4,2>}
- In Type-P-One-Way-Loss-Period-Stream
- 在P型单向损耗周期流中
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
{<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>},
the loss periods 1 and 2 are separated by 3 (5-2), loss periods 2 and 3 are separated by 2 (7-5), and 3 and 4 are separated by 2 (9-7). Thus, Type-P-One-Way-Inter-Loss-Period-Lengths =
损失期1和2由3（5-2）分隔，损失期2和3由2（7-5）分隔，3和4由2（9-7）分隔。因此，P型单向损耗周期长度=
{<1,0>,<2,3>,<3,2>,<4,2>}
{<1,0>,<2,3>,<3,2>,<4,2>}
Conducting Internet measurements raises both security and privacy concerns. This document does not specify a particular implementation of metrics, so it does not directly affect the security of the Internet nor of applications which run on the Internet. However, implementations of these metrics must be mindful of security and privacy concerns.
进行互联网测量会引起安全和隐私问题。本文档未指定指标的特定实现，因此它不会直接影响Internet的安全性，也不会直接影响在Internet上运行的应用程序的安全性。然而，这些指标的实现必须考虑安全和隐私问题。
The derived sample metrics in this document are based on the loss metric defined in RFC 2680 [1], and thus they inherit the security considerations of that document. The reader should consult [1] for a more detailed treatment of security considerations. Nevertheless, there are a few things to highlight.
本文件中的衍生样本指标基于RFC 2680[1]中定义的损失指标，因此它们继承了该文件的安全考虑因素。读者应参考[1]了解安全注意事项的更详细处理方法。然而，有几件事需要强调。
The lambda specified in the Type-P-Loss-Distance-Stream and Type-P-Loss-Period-Stream controls the rate at which test packets are sent, and therefore if it is set inappropriately large, it could perturb the network under test, cause congestion, or at worst be a denial-of-service attack to the network under test. Legitimate measurements must have their parameters selected carefully in order to avoid interfering with normal traffic in the network.
在Type-P-Loss-Distance-Stream和Type-P-Loss-Period-Stream中指定的lambda控制测试数据包的发送速率，因此，如果该lambda设置得过大，则可能会干扰被测网络，导致拥塞，或者最坏情况下是对被测网络的拒绝服务攻击。合法测量必须仔细选择其参数，以避免干扰网络中的正常流量。
Privacy of user data is not a concern, since the underlying metric is intended to be implemented using test packets that contain no user information. Even if packets contained user information, the derived metrics do not release data sent by the user.
用户数据的隐私性不是一个问题，因为底层度量是使用不包含用户信息的测试包来实现的。即使数据包包含用户信息，派生的度量也不会释放用户发送的数据。
Results could be perturbed by attempting to corrupt or disrupt the underlying stream, for example adding extra packets that look just like test packets. To ensure that test packets are valid and have not been altered during transit, packet authentication and integrity checks, such as a signed cryptographic hash, MAY be used.
结果可能会因为试图破坏或破坏底层流而受到干扰，例如添加看起来像测试数据包的额外数据包。为确保测试数据包有效且在传输过程中未被更改，可使用数据包身份验证和完整性检查，例如签名加密散列。
Since this document does not define a specific protocol, nor does it define any well-known values, there are no IANA considerations for this document.
由于本文档未定义特定协议，也未定义任何已知值，因此本文档不考虑IANA。
Matt Zekauskas provided insightful feedback and the text for the Security Considerations section. Merike Kao helped revising the Security Considerations and the Abstract to conform with RFC guidelines. We thank both of them. Thanks to Guy Almes for encouraging the work, and Vern Paxson for the comments during the IETF meetings. Thanks to Steve Glass for making the presentation at the Oslo meeting.
Matt Zekauskas为“安全注意事项”部分提供了深刻的反馈和文本。Merike Kao帮助修改了安全注意事项和摘要，以符合RFC指南。我们感谢他们两位。感谢Guy Almes鼓励这项工作，感谢Vern Paxson在IETF会议期间的评论。感谢史蒂夫·格拉斯在奥斯陆会议上的演讲。
[1] Almes, G., Kalindindi, S. and M. Zekauskas, "A One-way Packet Loss Metric for IPPM", RFC 2680, September 1999.
[1] Almes，G.，Kalindindi，S.和M.Zekauskas，“IPPM的单向分组丢失度量”，RFC 2680，1999年9月。
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[3] Paxson, V., Almes, G., Mahdavi, J. and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998.
[3] Paxson，V.，Almes，G.，Mahdavi，J.和M.Mathis，“IP性能度量框架”，RFC 2330，1998年5月。
[4] J.-C. Bolot and A. vega Garcia, "The case for FEC-based error control for Packet Audio in the Internet", ACM Multimedia Systems, 1997.
[4] J.-C.Bolot和A.vega Garcia，“互联网中基于FEC的分组音频差错控制案例”，ACM多媒体系统，1997年。
[5] M. S. Borella, D. Swider, S. Uludag, and G. B. Brewster, "Internet Packet Loss: Measurement and Implications for End-to-End QoS," Proceedings, International Conference on Parallel Processing, August 1998.
[5] M.S.Borella，D.Swider，S.Uludag和G.B.Brewster，“互联网数据包丢失：端到端QoS的测量和影响”，《并行处理国际会议论文集》，1998年8月。
[6] M. Handley, "An examination of MBONE performance", Technical Report, USC/ISI, ISI/RR-97-450, July 1997
[6] M.Handley，“MBONE绩效检查”，技术报告，USC/ISI，ISI/RR-97-450，1997年7月
[7] R. Koodli, "Scheduling Support for Multi-tier Quality of Service in Continuous Media Applications", PhD dissertation, Electrical and Computer Engineering Department, University of Massachusetts, Amherst, MA 01003, September 1997.
[7] R. Koodli，“连续媒体应用中的多层服务质量的调度支持”，麻州大学博士学位论文，电气与计算机工程系，Amherst，MA 01003，1997年9月。
[8] J. Padhye, V. Firoiu, J. Kurose and D. Towsley, "Modeling TCP throughput: a simple model and its empirical validation", in Proceedings of SIGCOMM'98, 1998.
[8] J.Padhye，V.Firoiu，J.Kurose和D.Towsley，“TCP吞吐量建模：一个简单模型及其经验验证”，发表于SIGCOMM'981998年论文集。
[9] J. Padhye, J. Kurose, D. Towsley and R. Koodli, "A TCP-friendly rate adjustment protocol for continuous media flows over best-effort networks", short paper presentation in ACM SIGMETRICS'99. Available as Umass Computer Science tech report from ftp://gaia.cs.umass.edu/pub/Padhye98-tcp-friendly-TR.ps.gz
[9] J.Padhye，J.Kurose，D.Towsley和R.Koodli，“一种TCP友好的速率调整协议，用于尽力而为网络上的连续媒体流”，ACM SIGMETRICS'99的短文介绍。可从以下网址获得麻省大学计算机科学技术报告：ftp://gaia.cs.umass.edu/pub/Padhye98-tcp-friendly-TR.ps.gz
[10] K. Sriram and W. Whitt, "Characterizing superposition arrival processes in packet multiplexers for voice and data", IEEE Journal on Selected Areas of Communication, pages 833-846, September 1986,
[10] K.Sriram和W.Whitt，“语音和数据分组复用器中叠加到达过程的特征”，《选定通信领域IEEE期刊》，第833-846页，1986年9月，
[11] M. Yajnik, J. Kurose and D. Towsley, "Packet loss correlation in the MBONE multicast network", Proceedings of IEEE Global Internet, London, UK, November 1996.
[11] M.Yajnik，J.Kurose和D.Towsley，“MBONE多播网络中的数据包丢失相关性”，IEEE全球互联网学报，英国伦敦，1996年11月。
Authors' Addresses
作者地址
Rajeev Koodli Communications Systems Lab Nokia Research Center 313 Fairchild Drive Mountain View, CA 94043 USA
Rajeev Koodli通信系统实验室诺基亚研究中心313 Fairchild Drive Mountain View，加利福尼亚州94043
Phone: +1-650 625-2359
Fax: +1 650 625-2502
EMail: rajeev.koodli@nokia.com
Phone: +1-650 625-2359
Fax: +1 650 625-2502
EMail: rajeev.koodli@nokia.com
Rayadurgam Ravikanth Axiowave Networks Inc. 200 Nickerson Road Marlborough, MA 01752 USA
美国马萨诸塞州马尔伯勒尼克森路200号Rayadurgam Ravikanth Axiowave Networks Inc.01752
EMail: rravikanth@axiowave.com
EMail: rravikanth@axiowave.com
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确认
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC编辑功能的资金目前由互联网协会提供。