Network Working Group W. Fang
Request for Comments: 2859 Princeton University
Category: Experimental N. Seddigh
B. Nandy
Nortel Networks
June 2000
Network Working Group W. Fang
Request for Comments: 2859 Princeton University
Category: Experimental N. Seddigh
B. Nandy
Nortel Networks
June 2000
A Time Sliding Window Three Colour Marker (TSWTCM)
时间滑动窗口三色标记（TSWTCM）
Status of this Memo
本备忘录的状况
This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.
这份备忘录为互联网社区定义了一个实验性协议。它没有规定任何类型的互联网标准。要求进行讨论并提出改进建议。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2000). All Rights Reserved.
版权所有（C）互联网协会（2000年）。版权所有。
Abstract
摘要
This memo defines a Time Sliding Window Three Colour Marker (TSWTCM), which can be used as a component in a Diff-Serv traffic conditioner [RFC2475, RFC2474]. The marker is intended to mark packets that will be treated by the Assured Forwarding (AF) Per Hop Behaviour (PHB) [AFPHB] in downstream routers. The TSWTCM meters a traffic stream and marks packets to be either green, yellow or red based on the measured throughput relative to two specified rates: Committed Target Rate (CTR) and Peak Target Rate (PTR).
本备忘录定义了一个时间滑动窗口三色标记（TSWTCM），该标记可用作区分服务流量调节器[RFC2475，RFC2474]中的一个组件。该标记旨在标记将由下游路由器中的保证转发（AF）每跳行为（PHB）[AFPHB]处理的分组。TSWTCM测量业务流，并根据相对于两个指定速率（提交目标速率（CTR）和峰值目标速率（PTR））的测量吞吐量将数据包标记为绿色、黄色或红色。
The Time Sliding Window Three Colour Marker (TSWTCM) is designed to mark packets of an IP traffic stream with colour of red, yellow or green. The marking is performed based on the measured throughput of the traffic stream as compared against the Committed Target Rate (CTR) and the Peak Target Rate (PTR). The TSWTCM is designed to mark packets contributing to sending rate below or equal to the CTR with green colour. Packets contributing to the portion of the rate between the CTR and PTR are marked yellow. Packets causing the rate to exceed PTR are marked with red colour.
时间滑动窗口三色标记（TSWTCM）设计用于以红色、黄色或绿色标记IP流量流的数据包。标记是基于测量的业务流吞吐量与提交目标速率（CTR）和峰值目标速率（PTR）进行比较来执行的。TSWTCM用于用绿色标记发送速率低于或等于CTR的数据包。构成CTR和PTR之间的速率部分的数据包被标记为黄色。导致速率超过PTR的数据包用红色标记。
The TSWTCM has been primarily designed for traffic streams that will be forwarded based on the AF PHB in core routers.
TSWTCM主要设计用于基于核心路由器中的AF PHB转发的业务流。
The TSWTCM operates based on simple control theory principles of proportionally regulated feedback control.
TSWTCM基于比例调节反馈控制的简单控制理论原理运行。
The TSWTCM consists of two independent components: a rate estimator, and a marker to associate a colour (drop precedence) with each packet. The marker uses the algorithm specified in section 4. If the marker is used with the AF PHB, each colour would correspond to a level of drop precedence.
TSWTCM由两个独立的组件组成：一个速率估计器和一个将颜色（丢弃优先级）与每个数据包相关联的标记。标记使用第4节中指定的算法。如果标记与AF PHB一起使用，则每种颜色都对应一个下降优先级别。
The rate estimator provides an estimate of the running average bandwidth. It takes into account burstiness and smoothes out its estimate to approximate the longer-term measured sending rate of the traffic stream.
速率估计器提供运行平均带宽的估计。它考虑突发性并平滑其估计，以近似于业务流的长期测量发送速率。
The marker uses the estimated rate to probabilistically associate packets with one of the three colours. Using a probabilistic function in the marker is beneficial to TCP flows as it reduces the likelihood of dropping multiple packets within a TCP window. The marker also works correctly with UDP traffic, i.e., it associates the appropriate portion of the UDP packets with yellow or red colour marking if such flows transmit at a sustained level above the contracted rate.
标记使用估计的速率概率地将数据包与三种颜色中的一种相关联。在标记中使用概率函数有利于TCP流，因为它降低了在TCP窗口中丢弃多个数据包的可能性。该标记还可以正确处理UDP流量，即，如果UDP数据包的适当部分以高于约定速率的持续水平传输，则该标记会将其与黄色或红色标记相关联。
+---------+
| Rate | Rate
|estimator| ==========
| | |
+---------+ |
^ V
| +---------+
| | |
Packet ====================>| Marker |====> Marked packet stream
Stream | | (Green, Yellow and Red)
+---------+
+---------+
| Rate | Rate
|estimator| ==========
| | |
+---------+ |
^ V
| +---------+
| | |
Packet ====================>| Marker |====> Marked packet stream
Stream | | (Green, Yellow and Red)
+---------+
Figure 1. Block diagram for the TSWTCM
图1。TSWTCM的框图
The colour of the packet is translated into a DS field packet marking. The colours red, yellow and green translate into DS codepoints representing drop precedence 2, 1 and 0 of a single AF class respectively.
数据包的颜色转换为DS字段数据包标记。红色、黄色和绿色转换为DS码点，分别表示单个AF类的下降优先级2、1和0。
Based on feedback from four different implementations, the TSWTCM is simple and straightforward to implement. The TSWTCM can be implemented in either software or hardware depending on the nature of the forwarding engine.
基于来自四种不同实现的反馈，TSWTCM实现起来简单明了。根据转发引擎的性质，TSWTCM可以在软件或硬件中实现。
The Rate Estimator provides an estimate of the traffic stream's arrival rate. This rate should approximate the running average bandwidth of the traffic stream over a specific period of time (AVG_INTERVAL).
速率估计器提供业务流到达速率的估计。该速率应近似于特定时间段（平均间隔）内业务流的运行平均带宽。
This memo does not specify a particular algorithm for the Rate Estimator. However, different Rate Estimators should yield similar results in terms of bandwidth estimation over the same fixed window (AVG_INTERVAL) of time. Examples of Rate Estimation schemes include: exponential weighted moving average (EWMA) and the time-based rate estimation algorithm provided in [TON98].
本备忘录未规定费率估计器的特定算法。然而，不同的速率估计器在相同固定时间窗（AVG_间隔）上的带宽估计方面应该产生相似的结果。速率估计方案的示例包括：指数加权移动平均（EWMA）和[TON98]中提供的基于时间的速率估计算法。
Preferably, the Rate Estimator SHOULD maintain time-based history for its bandwidth estimation. However, the Rate Estimator MAY utilize weight-based history. In this case, the Estimator used should discuss how the weight translates into a time-window such as AVG_INTERVAL.
优选地，速率估计器应当为其带宽估计维护基于时间的历史。然而，速率估计器可以利用基于权重的历史。在这种情况下，使用的估计器应讨论权重如何转换为时间窗，如平均间隔。
Since weight-based Estimators track bandwidth based on packet arrivals, a high-sending traffic stream will decay its past history faster than a low-sending traffic stream. The time-based Estimator is intended to address this problem. The latter Rate Estimator utilizes a low-pass filter decaying function. [FANG99] shows that this Rate Estimator decays past history independently of the traffic stream's packet arrival rate. The algorithm for the Rate Estimator from [TON98] is shown in Figure 2 below.
由于基于权重的估计器基于数据包到达跟踪带宽，高发送流量流将比低发送流量流更快地衰减其过去的历史。基于时间的估计器旨在解决这个问题。后一种速率估计器利用低通滤波器衰减函数。[FANG99]表明，该速率估计器独立于业务流的数据包到达速率衰减过去的历史。[TON98]中速率估计器的算法如下图2所示。
========================================================================
|Initially: |
| |
| AVG_INTERVAL = a constant; |
| avg-rate = CTR; |
| t-front = 0; |
| |
|Upon each packet's arrival, the rate estimator updates its variables: |
| |
| Bytes_in_win = avg-rate * AVG_INTERVAL; |
| New_bytes = Bytes_in_win + pkt_size; |
| avg-rate = New_bytes/( now - t-front + AVG_INTERVAL); |
| t-front = now; |
| |
|Where: |
| now = The time of the current packet arrival |
| pkt_size = The packet size in bytes of the arriving packet |
| avg-rate = Measured Arrival Rate of traffic stream |
| AVG_INTERVAL = Time window over which history is kept |
| |
| |
| Figure 2. Example Rate Estimator Algorithm |
| |
========================================================================
========================================================================
|Initially: |
| |
| AVG_INTERVAL = a constant; |
| avg-rate = CTR; |
| t-front = 0; |
| |
|Upon each packet's arrival, the rate estimator updates its variables: |
| |
| Bytes_in_win = avg-rate * AVG_INTERVAL; |
| New_bytes = Bytes_in_win + pkt_size; |
| avg-rate = New_bytes/( now - t-front + AVG_INTERVAL); |
| t-front = now; |
| |
|Where: |
| now = The time of the current packet arrival |
| pkt_size = The packet size in bytes of the arriving packet |
| avg-rate = Measured Arrival Rate of traffic stream |
| AVG_INTERVAL = Time window over which history is kept |
| |
| |
| Figure 2. Example Rate Estimator Algorithm |
| |
========================================================================
The Rate Estimator MAY operate in the Router Forwarding Path or as a background function. In the latter case, the implementation MUST ensure that the Estimator provides a reasonably accurate estimation of the sending rate over a window of time. The Rate Estimator MAY sample only certain packets to determine the rate.
速率估计器可在路由器转发路径中操作或作为背景函数操作。在后一种情况下，实现必须确保估计器在一个时间窗口内对发送速率提供合理准确的估计。速率估计器可以仅对某些分组进行采样以确定速率。
The Marker determines the colour of a packet based on the algorithm presented in Figure 3. The overall effect of the marker on the packets of a traffic stream is to ensure that:
标记器根据图3所示的算法确定数据包的颜色。标记对业务流的分组的总体影响是确保：
- If the estimated average rate is less than or equal to the CTR, packets of the stream are designated green.
- 如果估计的平均速率小于或等于CTR，则流的分组被指定为绿色。
- If the estimated average rate is greater than the CTR but less than or equal to the PTR, packets are designated yellow with probability P0 and designated green with probability (1-P0). P0 is the fraction of packets contributing to the measured rate beyond the CTR.
- 如果估计的平均速率大于CTR但小于或等于PTR，则分组被指定为概率为P0的黄色分组，概率为（1-P0）的绿色分组。P0是超出CTR的对测量速率有贡献的数据包的分数。
===================================================================
| avg-rate = Estimated Avg Sending Rate of Traffic Stream |
| |
| if (avg-rate <= CTR) |
| the packet is green; |
| else if (avg-rate <= PTR) AND (avg-rate > CTR) |
| (avg-rate - CTR) |
| calculate P0 = ---------------- |
| avg-rate |
| with probability P0 the packet is yellow; |
| with probability (1-P0) the packet is green; |
| else |
| (avg-rate - PTR) |
| calculate P1 = ---------------- |
| avg-rate |
| (PTR - CTR) |
| calculate P2 = ----------- |
| avg-rate |
| with probability P1 the packet is red; |
| with probability P2 the packet is yellow; |
| with probability (1-(P1+P2)) the packet is green; |
| |
| Figure 3. TSWTCM Marking Algorithm |
===================================================================
===================================================================
| avg-rate = Estimated Avg Sending Rate of Traffic Stream |
| |
| if (avg-rate <= CTR) |
| the packet is green; |
| else if (avg-rate <= PTR) AND (avg-rate > CTR) |
| (avg-rate - CTR) |
| calculate P0 = ---------------- |
| avg-rate |
| with probability P0 the packet is yellow; |
| with probability (1-P0) the packet is green; |
| else |
| (avg-rate - PTR) |
| calculate P1 = ---------------- |
| avg-rate |
| (PTR - CTR) |
| calculate P2 = ----------- |
| avg-rate |
| with probability P1 the packet is red; |
| with probability P2 the packet is yellow; |
| with probability (1-(P1+P2)) the packet is green; |
| |
| Figure 3. TSWTCM Marking Algorithm |
===================================================================
- If the estimated average rate is greater than the PTR, packets are designated red with probability P1, designated yellow with probability P2 and designated green with probability (1-(P1+P2)). P1 is the fraction of packets contributing to the measured rate beyond the PTR. P2 is the fraction of packets contributing to that part of the measured rate between CTR and PTR.
- 如果估计的平均速率大于PTR，则分组以概率P1被指定为红色，以概率P2被指定为黄色，以概率（1-（P1+P2））被指定为绿色。P1是对PTR之外的测量速率起作用的数据包的分数。P2是在CTR和PTR之间对该部分测量速率起作用的数据包的分数。
The marker MUST operate in the forwarding path of all packets.
标记必须在所有数据包的转发路径中运行。
If the Rate Estimator is time-based, it should base its bandwidth estimate on the last AVG_INTERVAL of time. AVG_INTERVAL is the amount of history (recent time) that should be used by the algorithm in estimating the rate. Essentially it represents the window of time included in the Rate Estimator's most recent result.
如果速率估计器是基于时间的，则其带宽估计应基于最后的平均时间间隔。AVG_INTERVAL是算法在估计速率时应使用的历史量（最近时间）。本质上，它代表了费率估计器最新结果中包含的时间窗口。
The value of AVG_INTERVAL SHOULD be configurable, and MAY be specified in either milliseconds or seconds.
AVG_INTERVAL的值应该是可配置的，可以毫秒或秒为单位指定。
[TON98] recommends that for the case where a single TCP flow constitutes the contracted traffic, AVG_INTERVAL be configured to approximately the same value as the RTT of the TCP flow. Subsequent experimental studies in [GLOBE99] utilized an AVG_INTERVAL value of 1 second for scenarios where the contracted traffic consisted of multiple TCP flows, some with different RTT values. The latter work showed that AVG_INTERVAL values larger than the largest RTT for a TCP flow in an aggregate can be used as long as the long-term bandwidth assurance for TCP aggregates is measured at a granularity of seconds. The AVG_INTERVAL value of 1 second was also used successfully for aggregates with UDP flows.
[TON98]建议在单个TCP流构成约定流量的情况下，将平均间隔配置为与TCP流的RTT大致相同的值。[GLOBE99]中的后续实验研究使用了1秒的平均G_间隔值，用于契约流量由多个TCP流组成的场景，其中一些具有不同的RTT值。后一项工作表明，只要TCP聚合的长期带宽保证以秒的粒度测量，就可以使用大于聚合中TCP流的最大RTT的平均间隔值。1秒的平均间隔值也成功用于UDP流的聚合。
If the Rate Estimator is weight-based, the factor used in weighting history - WEIGHT - SHOULD be a configurable parameter.
如果速率估计器是基于权重的，则加权历史中使用的因子-权重-应为可配置参数。
The Rate Estimator measures the average sending rate of the traffic stream based on the bytes in the IP header and IP payload. It does not include link-specific headers in its estimation of the sending rate.
速率估计器基于IP报头和IP有效负载中的字节来测量业务流的平均发送速率。它在估计发送速率时不包括特定于链路的报头。
The TSWTCM marker is configured by assigning values to its two traffic parameters: Committed Target Rate (CTR) and Peak Target Rate (PTR).
TSWTCM标记通过为其两个流量参数分配值进行配置：提交目标速率（CTR）和峰值目标速率（PTR）。
The PTR MUST be equal to or greater than the CTR.
PTR必须等于或大于CTR。
The CTR and PTR MAY be specifiable in bits per second or bytes per second.
CTR和PTR可以每秒比特数或每秒字节数来指定。
The TSWTCM can be configured so that it essentially operates with a single rate. If the PTR is set to the same value as the CTR then all packets will be coloured either green or red. There will be no yellow packets.
TSWTCM可以配置为基本上以单一速率运行。如果PTR设置为与CTR相同的值，则所有数据包将被涂成绿色或红色。不会有黄包。
If the PTR is set to link speed and the CTR is set below the PTR then all packets will be coloured either green or yellow. There will be no red packets.
如果PTR设置为链路速度，且CTR设置在PTR下方，则所有数据包将被涂成绿色或黄色。不会有红包。
The TSWTCM can work with both sender-based service level agreements and receiver-based service level agreements.
TSWTCM可以同时使用基于发送方的服务级别协议和基于接收方的服务级别协议。
There are no restrictions on the type of traffic stream for which the TSWTCM can be utilized. It can be used to meter and mark individual TCP flows, aggregated TCP flows, aggregates with both TCP and UDP flows [UDPTCP] etc.
TSWTCM可用于的交通流类型没有限制。它可用于测量和标记单个TCP流、聚合TCP流、与TCP和UDP流的聚合[UDPTCP]等。
The TSWTCM can be used in conjunction with the AF PHB to create a service where a service provider can provide decreasing levels of bandwidth assurance for packets originating from customer sites.
TSWTCM可与AF PHB结合使用，以创建服务，其中服务提供商可为源自客户站点的数据包提供降低的带宽保证级别。
With sufficient over-provisioning, customers are assured of mostly achieving their CTR. Sending rates beyond the CTR will have lesser assurance of being achieved. Sending rates beyond the PTR have the least chance of being achieved due to high drop probability of red packets.
有了充足的超额供应，客户就可以确保基本上实现其CTR。超出CTR的发送速率将无法保证实现。由于红包的高丢弃概率，超过PTR的发送速率实现的可能性最小。
Based on the above, the Service Provider can charge a tiered level of service based on the final achieved rate.
基于上述情况，服务提供商可以根据最终实现的费率收取分层服务级别的费用。
TSWTCM has no known security concerns.
TSWTCM没有已知的安全问题。
The authors would like to thank Juha Heinanen, Kenjiro Cho, Ikjun Yeom and Jamal Hadi Salim for their comments on earlier versions of this document. Their suggestions are incorporated in this memo.
作者感谢Juha Heinanen、Kenjiro Cho、Ikjun Yeom和Jamal Hadi Salim对本文件早期版本的评论。他们的建议包含在这份备忘录中。
[TON98] D.D. Clark, W. Fang, "Explicit Allocation of Best Effort Packet Delivery Service", IEEE/ACM Transactions on Networking, August 1998, Vol 6. No. 4, pp. 362-373.
[TON98]D.D.Clark，W.Fang，“尽力而为数据包交付服务的明确分配”，IEEE/ACM网络交易，1998年8月，第6卷。第4号，第362-373页。
[RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998.
[RFC2474]Nichols，K.，Blake，S.，Baker，F.和D.Black，“IPv4和IPv6标头中区分服务字段（DS字段）的定义”，RFC 2474，1998年12月。
[RFC2475] Black, D., Blake, S., Carlson, M., Davies, E., Wang, Z. and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998.
[RFC2475]Black，D.，Blake，S.，Carlson，M.，Davies，E.，Wang，Z.和W.Weiss，“差异化服务架构”，RFC 24751998年12月。
[FANG99] Fang, W. "The 'Expected Capacity' Framework: Simulation Results", Princeton University Technical Report, TR-601-99, March, 1999.
[FANG99]Fang，W.“预期能力”框架：模拟结果”，普林斯顿大学技术报告，TR-601-99，1999年3月。
[YEOM99] I. Yeom, N. Reddy, "Impact of Marking Strategy on Aggregated Flows in a Differentiated Services Network", Proceedings of IwQoS, May 1999.
[YEOM99]I.Yeom，N.Reddy，“标记策略对差异化服务网络中聚合流的影响”，《IwQoS学报》，1999年5月。
[AFPHB] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, "Assured Forwarding PHB Group", RFC 2597, June 1999.
[AFPHB]Heinanen，J.，Baker，F.，Weiss，W.和J.Wroclawski，“保付PHB集团”，RFC 25971999年6月。
[UDPTCP] P. Pieda, N. Seddigh, B. Nandy, "The Dynamics of TCP and UDP Interaction in IP-QoS Differentiated Service Networks", Proceedings of the 3rd Canadian Conference on Broadband Research (CCBR), Ottawa, November 1999
[UDPTCP]P.Pieda，N.Seddigh，B.Nandy，“IP QoS区分服务网络中TCP和UDP交互的动力学”，第三届加拿大宽带研究会议论文集，渥太华，1999年11月
[GLOBE99] N. Seddigh, B. Nandy, P. Pieda, "Bandwidth Assurance Issues for TCP flows in a Differentiated Services Network", Proceedings of Global Internet Symposium, Globecom 99, Rio De Janeiro, December 1999.
[GLOBE99]N.Seddigh，B.Nandy，P.Pieda，“差异化服务网络中TCP流的带宽保证问题”，全球互联网研讨会论文集，Globecom 99，里约热内卢，1999年12月。
Wenjia Fang Computer Science Dept. 35 Olden Street, Princeton, NJ08540
NJ08540普林斯顿奥尔登街35号方文家计算机科学部
EMail: wfang@cs.princeton.edu
EMail: wfang@cs.princeton.edu
Nabil Seddigh Nortel Networks, 3500 Carling Ave Ottawa, ON, K2H 8E9 Canada
Nabil Seddigh Nortel Networks，加拿大渥太华卡林大道3500号，K2H 8E9
EMail: nseddigh@nortelnetworks.com
EMail: nseddigh@nortelnetworks.com
Biswajit Nandy Nortel Networks, 3500 Carling Ave Ottawa, ON, K2H 8E9 Canada
Biswajit Nandy Nortel Networks，加拿大渥太华卡林大道3500号，K2H 8E9
EMail: bnandy@nortelnetworks.com
EMail: bnandy@nortelnetworks.com
Copyright (C) The Internet Society (2000). All Rights Reserved.
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本文件及其译本可复制并提供给他人，对其进行评论或解释或协助其实施的衍生作品可全部或部分编制、复制、出版和分发，不受任何限制，前提是上述版权声明和本段包含在所有此类副本和衍生作品中。但是，不得以任何方式修改本文件本身，例如删除版权通知或对互联网协会或其他互联网组织的引用，除非出于制定互联网标准的需要，在这种情况下，必须遵循互联网标准过程中定义的版权程序，或根据需要将其翻译成英语以外的其他语言。
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
上述授予的有限许可是永久性的，互联网协会或其继承人或受让人不会撤销。
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
本文件和其中包含的信息是按“原样”提供的，互联网协会和互联网工程任务组否认所有明示或暗示的保证，包括但不限于任何保证，即使用本文中的信息不会侵犯任何权利，或对适销性或特定用途适用性的任何默示保证。
Acknowledgement
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。