Internet Engineering Task Force (IETF) G. Karagiannis
Request for Comments: 6663 University of Twente
Category: Informational T. Taylor
ISSN: 2070-1721 Huawei
K. Chan
Consultant
M. Menth
University of Tuebingen
P. Eardley
BT
July 2012
Internet Engineering Task Force (IETF) G. Karagiannis
Request for Comments: 6663 University of Twente
Category: Informational T. Taylor
ISSN: 2070-1721 Huawei
K. Chan
Consultant
M. Menth
University of Tuebingen
P. Eardley
BT
July 2012
Requirements for Signaling of Pre-Congestion Information in a Diffserv Domain
区分服务域中拥塞前信息的信令要求
Abstract
摘要
Pre-Congestion Notification (PCN) is a means for protecting quality of service for inelastic traffic admitted to a Diffserv domain. The overall PCN architecture is described in RFC 5559. This memo describes the requirements for the signaling applied within the PCN-domain: (1) PCN-feedback-information is carried from the PCN-egress-node to the Decision Point; (2) the Decision Point may ask the PCN-ingress-node to measure, and report back, the rate of sent PCN-traffic between that PCN-ingress-node and PCN-egress-node. The Decision Point may be either collocated with the PCN-ingress-node or a centralized node (in the first case, (2) is not required). The signaling requirements pertain in particular to two edge behaviors, Controlled Load (CL) and Single Marking (SM).
预拥塞通知（PCN）是一种用于保护进入区分服务域的非弹性流量的服务质量的方法。RFC 5559中描述了整个PCN体系结构。本备忘录描述了在PCN域内应用的信令要求：（1）PCN反馈信息从PCN出口节点传送到决策点；（2） 决策点可以要求PCN入口节点测量并报告该PCN入口节点和PCN出口节点之间发送的PCN流量的速率。决策点可以与PCN入口节点或集中式节点并置（在第一种情况下，（2）不是必需的）。信号要求特别涉及两种边缘行为，即控制负载（CL）和单标记（SM）。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。并非IESG批准的所有文件都适用于任何级别的互联网标准；见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6663.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6663.
Copyright Notice
版权公告
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2012 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................2
1.1. Requirements Language ......................................3
2. Signaling Requirements for Messages from the PCN-Egress-Nodes
to Decision Point(s) ............................................3
3. Signaling Requirements for Messages between Decision Point(s)
and PCN-Ingress-Nodes ...........................................5
4. Security Considerations .........................................5
5. Acknowledgments .................................................6
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................6
1. Introduction ....................................................2
1.1. Requirements Language ......................................3
2. Signaling Requirements for Messages from the PCN-Egress-Nodes
to Decision Point(s) ............................................3
3. Signaling Requirements for Messages between Decision Point(s)
and PCN-Ingress-Nodes ...........................................5
4. Security Considerations .........................................5
5. Acknowledgments .................................................6
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................6
The main objective of Pre-Congestion Notification (PCN) is to support the quality of service (QoS) of inelastic flows within a Diffserv domain in a simple, scalable, and robust fashion. Two mechanisms are used: admission control and flow termination. Admission control is used to decide whether to admit or block a new flow request, while flow termination is used in abnormal circumstances to decide whether to terminate some of the existing flows. To support these two features, the overall rate of PCN-traffic is metered on every link in the domain, and PCN-packets are appropriately marked when certain configured rates are exceeded. These configured rates are below the rate of the link, thus providing notification to boundary nodes about overloads before any congestion occurs (hence "pre-congestion" notification). The PCN-egress-nodes measure the rates of differently marked PCN traffic in periodic intervals and report these rates to the Decision Points for admission control and flow termination; the Decision Points use these rates to make decisions. The Decision Points may be collocated with the PCN-ingress-nodes, or their
预拥塞通知（PCN）的主要目标是以一种简单、可扩展和健壮的方式支持Diffserv域内非弹性流的服务质量（QoS）。使用两种机制：接纳控制和流终止。接纳控制用于决定是否接纳或阻止新的流请求，而流终止用于在异常情况下决定是否终止某些现有流。为了支持这两个功能，在域中的每个链路上测量PCN流量的总速率，并且当超过某些配置速率时，适当地标记PCN数据包。这些配置的速率低于链路速率，因此在发生任何拥塞之前向边界节点提供有关过载的通知（因此为“拥塞前”通知）。PCN出口节点以周期性间隔测量不同标记的PCN流量的速率，并将这些速率报告给决策点以进行准入控制和流量终止；决策点使用这些比率来做出决策。决策点可与PCN入口节点或其入口节点并置
function may be implemented in a centralized node. For more details see [RFC5559], [RFC6661], and [RFC6662].
该功能可以在集中式节点中实现。有关更多详细信息，请参阅[RFC5559]、[RFC6661]和[RFC6662]。
This memo specifies the requirements on signaling protocols: o to carry reports from a PCN-egress-node to the Decision Point, o to carry requests, from the Decision Point to a PCN-ingress-node, that trigger the PCN-ingress-node to measure the PCN-sent-rate, o to carry reports, from a PCN-ingress-node to the Decision Point.
本备忘录规定了信令协议的要求：o将报告从PCN出口节点传送到决策点；o将请求从决策点传送到PCN入口节点，触发PCN入口节点测量PCN发送速率；o将报告从PCN入口节点传送到决策点。
The latter two messages are only needed if the Decision Point and PCN-ingress-node are not collocated.
仅当决策点和PCN入口节点未并置时，才需要后两条消息。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[RFC2119]中所述进行解释。
2. Signaling Requirements for Messages from the PCN-Egress-Nodes to Decision Point(s)
2. 从PCN出口节点到决策点的消息信令要求
The PCN-egress-node measures per ingress-egress-aggregate the rates of differently marked PCN-traffic in regular intervals. The measurement intervals are recommended to take a fixed value between 100 ms and 500 ms; see [RFC6661] and [RFC6662]. At the end of each measurement interval, the PCN-egress-node calculates the congestion-level-estimate (CLE) based on these quantities.
PCN出口节点定期测量每个入口-出口聚合不同标记的PCN流量的速率。建议测量间隔取100 ms至500 ms之间的固定值；参见[RFC6661]和[RFC6662]。在每个测量间隔结束时，PCN出口节点根据这些量计算拥塞水平估计（CLE）。
The PCN-egress-node MAY be configured to record a set of identifiers of PCN-flows for which it received excess-traffic-marked packets during the last measurement interval. The latter may be useful to perform flow termination in networks with multipath routing.
PCN出口节点可被配置为记录其在最后测量间隔期间接收到的多余业务标记分组的PCN流的一组标识符。后者可用于在具有多路径路由的网络中执行流终止。
At the end of each measurement interval, or less frequently if "optional report suppression" is activated (see [RFC6661] and [RFC6662]), the PCN-egress-node sends a report to the Decision Point.
在每个测量间隔结束时，或者如果激活了“可选报告抑制”（参见[RFC6661]和[RFC6662]），则PCN出口节点向决策点发送报告的频率较低。
For the SM edge behavior, the report MUST contain: o the identifier of the PCN-ingress-node and the identifier of the PCN-egress-node (typically their IP addresses); together they specify the ingress-egress-aggregate to which the report refers, o the rate of not-marked PCN-traffic (NM-rate) in octets/second, and o the rate of PCN-marked traffic (PM-rate) in octets/second.
对于SM边缘行为，报告必须包含：o PCN入口节点的标识符和PCN出口节点的标识符（通常是它们的IP地址）；它们一起指定了报告所指的进出口聚合，o未标记PCN流量的速率（NM速率）（以八位字节/秒为单位）和o标记PCN流量的速率（PM速率）（以八位字节/秒为单位）。
For the CL edge behavior, the report MUST contain: o the identifier of the PCN-ingress-node and the identifier of the PCN-egress-node (typically their IP addresses); together they specify the ingress-egress-aggregate to which the report refers,
对于CL边缘行为，报告必须包含：o PCN入口节点的标识符和PCN出口节点的标识符（通常是它们的IP地址）；它们一起指定了报告所指的入口-出口聚合，
o the rate of not-marked PCN-traffic (NM-rate) in octets/second, o the rate of threshold-marked PCN traffic (ThM-rate) in octets/second, and o the rate of excess-traffic-marked traffic (ETM-rate) in octets/second.
o 未标记PCN流量的速率（NM速率）（以八位字节/秒为单位）、阈值标记PCN流量的速率（ThM速率）（以八位字节/秒为单位）和过量流量标记流量的速率（ETM速率）（以八位字节/秒为单位）。
The number format and the rate units used by the signaling protocol will limit the maximum rate that PCN can use. If signaling space is tight, it might be reasonable to impose a limit, but any such limit may impose unnecessary constraints in the future.
信令协议使用的数字格式和速率单位将限制PCN可以使用的最大速率。如果信号空间紧张，施加限制可能是合理的，但任何此类限制可能会在将来施加不必要的限制。
The signaling report can either be sent directly to the Decision Point or it can "piggy-back", i.e., be included within some other message that passes through the PCN-egress-node and then reaches the Decision Point.
信令报告可以直接发送到决策点，也可以“背驮”，即包括在通过PCN出口节点然后到达决策点的一些其他消息中。
As described in [RFC6661], PCN reports from the PCN-egress-node to the Decision Point may contain flow identifiers for individual flows within an ingress-egress-aggregate that have recently experienced excess-marking. Hence, the PCN report messages used by the PCN CL edge behavior MUST be capable of carrying sequences of octet strings constituting such identifiers.
如[RFC6661]中所述，从PCN出口节点到决策点的PCN报告可能包含入口-出口集合内最近经历过过度标记的单个流的流标识符。因此，PCN CL边缘行为使用的PCN报告消息必须能够承载构成此类标识符的八位字节字符串序列。
Signaling messages SHOULD have a higher priority and a lower drop precedence than PCN-packets (see [RFC5559]) in order to deliver them quickly and to prevent them from being dropped in case of overload.
信令消息应具有比PCN数据包更高的优先级和更低的丢弃优先级（请参见[RFC5559]），以便快速传递这些数据包，并防止在过载情况下丢弃这些数据包。
The load generated by the signaling protocol SHOULD be minimized. We give three methods that may help to achieve that goal: 1. piggy-backing the reports by the PCN-egress-nodes to the Decision Point(s) onto other signaling messages that are already in place, 2. reducing the amount of reports to be sent by optional report suppression, or 3. combining reports for different ingress-egress-aggregates in a single message (if they are for the same Decision Point).
信令协议产生的负载应最小化。我们给出了三种可能有助于实现这一目标的方法：1。将PCN出口节点到决策点的报告背驮到已经就位的其他信令消息上，2。通过可选报告抑制或3减少要发送的报告量。在单个消息中组合不同入口-出口聚合的报告（如果它们是针对同一决策点的）。
As PCN reports are sent regularly, additional reliability mechanisms are not needed. This also holds in the presence of optional report suppression, as reports are sent periodically if actions by the Decision Point(s) are needed; see [RFC6661] and [RFC6662].
由于PCN报告定期发送，因此不需要额外的可靠性机制。这也适用于存在可选报告抑制的情况，因为如果需要决策点采取行动，报告将定期发送；参见[RFC6661]和[RFC6662]。
3. Signaling Requirements for Messages between Decision Point(s) and PCN-Ingress-Nodes
3. 决策点和PCN入口节点之间消息的信令要求
Through request-response signaling between the Decision Point and PCN-ingress-node, the Decision Point requests and in response the PCN-ingress-node measures and reports the PCN-sent-rate for a specific ingress-egress-aggregate. Signaling is needed only if the Decision Point and PCN-ingress-node are not collocated.
通过决策点和PCN入口节点之间的请求-响应信令，决策点请求并响应PCN入口节点测量并报告特定入口-出口聚合的PCN发送速率。仅当决策点和PCN入口节点未并置时才需要信令。
The request MUST contain: o the identifier of the PCN-ingress-node and the identifier of the PCN-egress-node; together they determine the ingress-egress-aggregate for which the PCN-sent-rate is requested, and o the identifier of the Decision Point that requests the PCN-sent-rate.
请求必须包含：o PCN入口节点的标识符和PCN出口节点的标识符；它们一起确定请求PCN发送速率的入口-出口聚合，以及请求PCN发送速率的决策点的标识符。
The report MUST contain: o the PCN-sent-rate in octets/second, and o the identifier of the PCN-ingress-node and the identifier of the PCN-egress-node.
报告必须包含：o以八位字节/秒为单位的PCN发送速率，以及o PCN入口节点的标识符和PCN出口节点的标识符。
The request MUST be addressed to the PCN-ingress-node, and the report MUST be addressed to the Decision Point that requested it.
请求必须发送至PCN入口节点，报告必须发送至请求该请求的决策点。
Because they are sent only when flow termination is needed (which is an urgent action), the request and the report SHOULD be sent with high priority, with a lower drop precedence than PCN-packets, and in a reliable manner.
由于它们仅在需要终止流（这是一项紧急操作）时发送，因此请求和报告应以高优先级、比PCN数据包更低的丢弃优先级和可靠的方式发送。
Note that a complete system description for a PCN-domain with centralized Decision Point includes the signaling from Decision Point to the PCN-ingress-nodes to control flow admission and termination. However, this is a known problem (with solutions provided in [RFC3084] and [RFC5431], for example), and it lies outside the scope of the present document.
注意，对于具有集中决策点的PCN域的完整系统描述包括从决策点到PCN入口节点的信令，以控制流的接纳和终止。然而，这是一个已知的问题（例如[RFC3084]和[RFC5431]中提供的解决方案），不在本文档的范围内。
[RFC5559] provides a general description of the security considerations for PCN. This memo relies on the security-related requirements of the PCN signaling, provided in [RFC5559]. In particular, the signaling between the PCN-boundary-nodes must be protected from attacks. For example, the recipient needs to validate that the message is indeed from the node that claims to have sent it. Possible measures include digest authentication and protection against replay and man-in-the-middle attacks.
[RFC5559]提供了PCN安全注意事项的一般说明。本备忘录依赖于[RFC5559]中提供的PCN信令的安全相关要求。特别是，必须保护PCN边界节点之间的信令免受攻击。例如，收件人需要验证消息是否确实来自声称已发送消息的节点。可能的措施包括摘要身份验证和防止重播和中间人攻击。
Specifically for the generic aggregate RSVP protocol, additional protection methods against security attacks are described in [RFC4860].
特别是对于通用聚合RSVP协议，[RFC4860]中描述了针对安全攻击的其他保护方法。
We would like to acknowledge the members of the PCN working group for the discussions that produced the contents of this memo.
我们要感谢PCN工作组成员的讨论，讨论产生了本备忘录的内容。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC5559] Eardley, P., Ed., "Pre-Congestion Notification (PCN) Architecture", RFC 5559, June 2009.
[RFC5559]Eardley，P.，Ed.“拥塞前通知（PCN）体系结构”，RFC55559，2009年6月。
[RFC6661] Charny, A., Huang, F., Karagiannis, G., Twente, U., Menth, M., and T. Taylor, Ed., "Pre-Congestion Notification (PCN) Boundary-Node Behaviour for the Controlled Load (CL) Mode of Operation", RFC 6661, July 2012.
[RFC6661]Charny，A.，Huang，F.，Karagiannis，G.，Twente，U.，Minth，M.，和T.Taylor，Ed.，“受控负荷（CL）运行模式下的拥塞前通知（PCN）边界节点行为”，RFC 6661，2012年7月。
[RFC6662] Charny, A., Zhang, J., Karagiannis, G., Twente, U., Menth, M., and T. Taylor, Ed., "Pre-Congestion Notification (PCN) Boundary-Node Behaviour for the Single Marking (SM) Mode of Operation", RFC 6662, July 2012.
[RFC6662]Charny，A.，Zhang，J.，Karagiannis，G.，Twente，U.，Minth，M.，和T.Taylor，Ed.，“单一标记（SM）运行模式下的拥塞前通知（PCN）边界节点行为”，RFC 6662，2012年7月。
[RFC3084] Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie, K., Herzog, S., Reichmeyer, F., Yavatkar, R., and A. Smith, "COPS Usage for Policy Provisioning (COPS-PR)", RFC 3084, March 2001.
[RFC3084]Chan，K.，Seligson，J.，Durham，D.，Gai，S.，McCloghrie，K.，Herzog，S.，Reichmeyer，F.，Yavatkar，R.，和A.Smith，“策略供应的COPS使用（COPS-PR）”，RFC 30842001年3月。
[RFC4860] Le Faucheur, F., Davie, B., Bose, P., Christou, C., and M. Davenport, "Generic Aggregate Resource ReSerVation Protocol (RSVP) Reservations", RFC 4860, May 2007.
[RFC4860]Le Faucheur，F.，Davie，B.，Bose，P.，Christou，C.，和M.Davenport，“通用聚合资源预留协议（RSVP）预留”，RFC 48602007年5月。
[RFC5431] Sun, D., "Diameter ITU-T Rw Policy Enforcement Interface Application", RFC 5431, March 2009.
[RFC5431]Sun，D.，“Diameter ITU-T Rw策略实施接口应用”，RFC 54312009年3月。
Authors' Addresses
作者地址
Georgios Karagiannis University of Twente P.O. Box 217 7500 AE Enschede, The Netherlands EMail: g.karagiannis@utwente.nl
乔治斯卡拉基安尼斯屯特大学邮政信箱217 7500 AE恩斯赫德，荷兰电子邮件：G。karagiannis@utwente.nl
Tom Taylor Huawei Technologies Ottawa Canada EMail: tom.taylor.stds@gmail.com
汤姆泰勒华为技术渥太华加拿大电子邮件：Tom.Taylor。stds@gmail.com
Kwok Ho Chan Consultant EMail: khchan.work@gmail.com
郭浩灿顾问电邮：khchan。work@gmail.com
Michael Menth University of Tuebingen Sand 13 72076 Tuebingen Germany Phone: +49-7071-2970505 EMail: menth@uni-tuebingen.de
米迦勒·蒙特大学图宾根沙特13 72076德布宁德国电话：+497071-970505电子邮件：menth@uni-图宾根
Philip Eardley BT B54/77, Sirius House Adastral Park Martlesham Heath Ipswich, Suffolk IP5 3RE United Kingdom EMail: philip.eardley@bt.com
Philip Eardley BT B54/77，天狼星之家阿达斯特拉尔公园，萨福克郡马特勒沙姆希思伊普斯维奇IP5 3RE英国电子邮件：Philip。eardley@bt.com