Internet Engineering Task Force (IETF) J. Hedin
Request for Comments: 7750 G. Mirsky
Updates: 5357 S. Baillargeon
Category: Standards Track Ericsson
ISSN: 2070-1721 February 2016
Internet Engineering Task Force (IETF) J. Hedin
Request for Comments: 7750 G. Mirsky
Updates: 5357 S. Baillargeon
Category: Standards Track Ericsson
ISSN: 2070-1721 February 2016
Differentiated Service Code Point and Explicit Congestion Notification Monitoring in the Two-Way Active Measurement Protocol (TWAMP)
双向主动测量协议（TWAMP）中的区分服务码点和显式拥塞通知监控
Abstract
摘要
This document describes an optional extension for Two-Way Active Measurement Protocol (TWAMP) allowing the monitoring of the Differentiated Service Code Point and Explicit Congestion Notification fields with the TWAMP-Test protocol.
本文档描述了双向主动测量协议（TWAMP）的可选扩展，允许使用TWAMP测试协议监控区分服务代码点和显式拥塞通知字段。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
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). Further information on Internet Standards is available in 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。有关互联网标准的更多信息，请参见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/rfc7750.
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/rfc7750.
Copyright Notice
版权公告
Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2016 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. Conventions Used in This Document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. TWAMP Extensions . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Setting Up Connection to Monitor DSCP and ECN . . . . . . 3
2.2. TWAMP-Test Extension . . . . . . . . . . . . . . . . . . 4
2.2.1. Session-Reflector Packet Format for DSCP and ECN
Monitoring . . . . . . . . . . . . . . . . . . . . . 4
2.2.2. DSCP and ECN Monitoring with Extensions from RFC 6038 8
2.2.3. Consideration for TWAMP Light Mode . . . . . . . . . 8
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Normative References . . . . . . . . . . . . . . . . . . 9
5.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. TWAMP Extensions . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Setting Up Connection to Monitor DSCP and ECN . . . . . . 3
2.2. TWAMP-Test Extension . . . . . . . . . . . . . . . . . . 4
2.2.1. Session-Reflector Packet Format for DSCP and ECN
Monitoring . . . . . . . . . . . . . . . . . . . . . 4
2.2.2. DSCP and ECN Monitoring with Extensions from RFC 6038 8
2.2.3. Consideration for TWAMP Light Mode . . . . . . . . . 8
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Normative References . . . . . . . . . . . . . . . . . . 9
5.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
The One-Way Active Measurement Protocol (OWAMP) [RFC4656] defines the Type-P Descriptor field and negotiation of its value in the OWAMP-Control protocol. The Two-Way Active Measurement Protocol (TWAMP) [RFC5357] states that only a Differentiated Services Code Point (DSCP) value (see [RFC2474], [RFC3168], and [RFC3260]) can be defined by Type-P Descriptor, and the negotiated value must be used by both the Session-Sender and Session-Reflector. The TWAMP specification also states that the same DSCP value (found in the Session-Sender packet) MUST be used in the test packet reflected by the Session-Reflector. However, the TWAMP-Test protocol does not specify any methods to determine or report when the DSCP value has changed or is different than expected in the forward or reverse direction. Re-marking the DSCP (changing its original value) in IP networks is possible and often accomplished by a Differentiated Services policy configured on a single node along the IP path. In many cases, a change of the DSCP value indicates an unintentional or erroneous behavior. At best, the Session-Sender can detect a change of the DSCP reverse direction, assuming such a change is actually detectable.
单向主动测量协议（OWAMP）[RFC4656]定义了P型描述符字段，并在OWAMP控制协议中协商其值。双向主动测量协议（TWAMP）[RFC5357]规定，P型描述符只能定义区分服务代码点（DSCP）值（请参见[RFC2474]、[RFC3168]和[RFC3260]），并且会话发送方和会话反射方都必须使用协商值。TWAMP规范还规定，会话反射器反射的测试数据包中必须使用相同的DSCP值（在会话发送器数据包中找到）。但是，TWAMP测试协议没有指定任何方法来确定或报告DSCP值在正向或反向发生变化或与预期不同时的情况。在IP网络中重新标记DSCP（更改其原始值）是可能的，并且通常通过在IP路径上的单个节点上配置的区分服务策略来完成。在许多情况下，DSCP值的更改表示无意或错误的行为。充其量，会话发送方可以检测到DSCP反向的变化，假设这种变化实际上是可检测的。
This document describes an OPTIONAL feature for TWAMP. It is called DSCP and ECN Monitoring. It allows the Session-Sender to know the actual DSCP value received at the Session-Reflector. Furthermore, this feature tracks the Explicit Congestion Notification (ECN) value (see [RFC2474], [RFC3168], and [RFC3260]) received at the Session-
本文档描述了TWAMP的可选功能。它被称为DSCP和ECN监控。它允许会话发送方知道会话反射器接收到的实际DSCP值。此外，此功能跟踪会话中接收的显式拥塞通知（ECN）值（请参阅[RFC2474]、[RFC3168]和[RFC3260]）-
Reflector. This is helpful to determine if the ECN is actually operating or if an ECN-capable node has detected congestion in the forward direction.
反射器。这有助于确定ECN是否实际在运行，或者支持ECN的节点是否检测到正向拥塞。
DSCP: Differentiated Services Code Point
DSCP：区分服务代码点
ECN: Explicit Congestion Notification
显式拥塞通知
IPPM: IP Performance Metrics
IPPM:IP性能度量
TWAMP: Two-Way Active Measurement Protocol
双向主动测量协议
OWAMP: One-Way Active Measurement Protocol
OWAMP：单向主动测量协议
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 [RFC2119].
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”应按照[RFC2119]中的说明进行解释。
TWAMP connection establishment follows the procedure defined in Section 3.1 of [RFC4656] and Section 3.1 of [RFC5357] where the Modes field is used to identify and select specific communication capabilities. At the same time, the Modes field is recognized and used as an extension mechanism [RFC6038]. The new feature requires a new flag to identify the ability of a Session-Reflector to return the values of received DSCP and ECN values back to a Session-Sender, and to support the new Session-Reflector packet format in the TWAMP-Test protocol. See Section 3 for details on the assigned bit position.
TWAMP连接建立遵循[RFC4656]第3.1节和[RFC5357]第3.1节中定义的程序，其中模式字段用于识别和选择特定的通信能力。同时，模式字段被识别并用作扩展机制[RFC6038]。新功能需要一个新标志来标识会话反射器将接收到的DSCP和ECN值的值返回给会话发送器的能力，并在TWAMP测试协议中支持新的会话反射器数据包格式。有关指定位位置的详细信息，请参见第3节。
The Server sets the DSCP and ECN Monitoring flag in the Modes field of the Server Greeting message to indicate its capabilities and willingness to monitor them. If the Control-Client agrees to monitor DSCP and ECN on some or all test sessions invoked with this control connection, it MUST set the DSCP and ECN Monitoring flag in the Modes field in the Setup Response message.
服务器在服务器问候语消息的模式字段中设置DSCP和ECN监视标志，以指示其监视它们的能力和意愿。如果控制客户端同意在此控制连接调用的部分或所有测试会话上监视DSCP和ECN，则必须在设置响应消息的模式字段中设置DSCP和ECN监视标志。
Monitoring of DSCP and ECN requires support by the Session-Reflector and changes the test packet format in all the original modes (unauthenticated, authenticated, and encrypted). Monitoring of DSCP and ECN does not alter the Session-Sender test packet format, but certain considerations must be taken when and if this mode is accepted in combination with Symmetrical Size mode [RFC6038].
监控DSCP和ECN需要会话反射器的支持，并在所有原始模式（未经验证、验证和加密）下更改测试数据包格式。对DSCP和ECN的监控不会改变会话发送方测试数据包的格式，但如果该模式与对称大小模式结合使用，则必须考虑某些因素[RFC6038]。
When the Session-Reflector supports DSCP and ECN Monitoring, it constructs the Sender DSCP and ECN (S-DSCP-ECN) field, presented in Figure 1, for each test packet it sends to the Session-Sender according to the following procedure:
当会话反射器支持DSCP和ECN监控时，它会根据以下过程为发送给会话发送器的每个测试数据包构造发送器DSCP和ECN（S-DSCP-ECN）字段，如图1所示：
o the six (least-significant) bits of the Differentiated Service field MUST be copied from the received Session-Sender test packet into the Sender DSCP (S-DSCP) field;
o 区分服务字段的六个（最低有效）位必须从接收到的会话发送方测试数据包复制到发送方DSCP（S-DSCP）字段中；
o the two bits of the ECN field MUST be copied from the received Session-Sender test packet into the Sender ECN (S-ECN) field.
o ECN字段的两位必须从接收到的会话发送方测试数据包复制到发送方ECN（S-ECN）字段中。
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| S-DSCP | S-ECN |
+---+---+---+---+---+---+---+---+
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| S-DSCP | S-ECN |
+---+---+---+---+---+---+---+---+
Figure 1: Sender DSCP and ECN Field Format
图1：发送方DSCP和ECN字段格式
Formats of the test packet transmitted by the Session-Reflector in unauthenticated, authenticated, and encrypted modes have been defined in Section 4.2.1 of [RFC5357]. For the Session-Reflector that supports DSCP and ECN Monitoring, these formats are displayed in Figures 2 and 3.
[RFC5357]第4.2.1节定义了会话反射器在未经验证、验证和加密模式下传输的测试数据包格式。对于支持DSCP和ECN监视的会话反射器，这些格式显示在图2和图3中。
For unauthenticated mode:
对于未经验证的模式：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Session-Reflector Test Packet Format with DSCP and ECN Monitoring in Unauthenticated Mode
图2:DSCP和ECN监视处于未经验证模式的会话反射器测试数据包格式
The DSCP and ECN values (part of the Type-P Descriptor [RFC4656]) can be provisioned through TWAMP-Control or by other means (command-line interface (CLI) or Central Controller). The DSCP and ECN values are often copied into reflected test packets with current TWAMP implementations without TWAMP-Control protocol. With the DSCP and ECN Monitoring extension, the Session-Reflector handles the DSCP as follows:
DSCP和ECN值（P型描述符[RFC4656]的一部分）可通过TWAMP控制或其他方式（命令行界面（CLI）或中央控制器）提供。DSCP和ECN值通常被复制到反射的测试数据包中，当前的TWAMP实现没有TWAMP控制协议。通过DSCP和ECN监视扩展，会话反射器按如下方式处理DSCP：
o the Session-Reflector MUST extract the DSCP and ECN values from the received packet and MUST use them to populate the S-DSCP-ECN field of the corresponding reflected packet;
o 会话反射器必须从接收到的分组中提取DSCP和ECN值，并且必须使用它们来填充相应反射分组的S-DSCP-ECN字段；
o the Session-Reflector MUST transmit each reflected test packet with the DSCP set to the provisioned value;
o 会话反射器必须在DSCP设置为规定值的情况下发送每个反射的测试包；
o if the provisioned DSCP value is not known (e.g., TWAMP Light), the choice of the DSCP is implementation specific. For instance, the Session-Reflector MAY copy the DSCP value from the received test packet and set it as the DSCP in a reflected packet. Alternatively, the Session-Reflector MAY set the DSCP value to CS0 (zero) [RFC2474];
o 如果配置的DSCP值未知（例如TWAMP灯），则DSCP的选择取决于具体实现。例如，会话反射器可以从接收到的测试分组复制DSCP值，并将其设置为反射分组中的DSCP。或者，会话反射器可以将DSCP值设置为CS0（零）[RFC2474]；
o if the provisioned ECN value is not known, ECN SHOULD be set to Not-ECT codepoint value [RFC3168]. Otherwise, the provisioned ECN value for the session SHALL be used.
o 如果配置的ECN值未知，则应将ECN设置为not ECT codepoint value[RFC3168]。否则，应使用为会话提供的ECN值。
A Session-Reflector in the DSCP and ECN Monitoring mode does not analyze nor act on the ECN value of the received TWAMP test packet; therefore, it ignores congestion indications from the network. It is expected that sending rates are low enough, as TWAMP deployment experience had demonstrated since TWAMP base (RFC 5357) was published in 2008, that ignoring these congestion indications will not significantly contribute to network congestion.
DSCP和ECN监控模式下的会话反射器不分析接收到的TWAMP测试分组的ECN值，也不对其进行操作；因此，它忽略了来自网络的拥塞指示。正如自2008年发布TWAMP base（RFC 5357）以来的TWAMP部署经验所表明的那样，预计发送速率足够低，忽略这些拥塞指示不会显著导致网络拥塞。
For authenticated and encrypted modes:
对于认证和加密模式：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (14 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| MBZ (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | S-DSCP-ECN | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (14 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Packet Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Session-Reflector Test Packet Format with DSCP and ECN Monitoring in Authenticated or Encrypted Modes
图3：会话反射器测试数据包格式，DSCP和ECN监控处于认证或加密模式
[RFC6038] defined two extensions to TWAMP -- first, to ensure that the Session-Sender and Session-Reflector exchange TWAMP-Test packets of equal size; second, to specify the number of octets to be reflected by Session-Reflector. If DSCP and ECN Monitoring and Symmetrical Size and/or Reflects Octets modes are being negotiated between Server and Control-Client in Unauthenticated mode, then, because Sender DSCP and Sender ECN increase the size of the unauthenticated Session-Reflector packet by 4 octets, the Padding Length value SHOULD be greater than or equal to 28 octets to allow for the truncation process that TWAMP recommends in Section 4.2.1 of [RFC5357].
[RFC6038]为TWAMP定义了两个扩展——首先，确保会话发送方和会话反射方交换大小相同的TWAMP测试包；其次，指定会话反射器要反映的八位字节数。如果服务器和控制客户端在未经身份验证的模式下协商DSCP和ECN监控和对称大小和/或反射八位字节模式，则由于发送方DSCP和发送方ECN将未经身份验证的会话反射器数据包的大小增加了4个八位字节，填充长度值应大于或等于28个八位字节，以允许TWAMP在[RFC5357]第4.2.1节中建议的截断过程。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (28 octets) |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. .
. Packet Padding .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| MBZ (28 octets) |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. .
. Packet Padding .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Session-Sender Test Packet Format with DSCP and ECN Monitoring and Symmetrical Test Packet in Unauthenticated Mode
图4:DSCP和ECN监视的会话发送方测试数据包格式以及未经验证模式下的对称测试数据包
Appendix I of [RFC5357] does not explicitly state how the value of the Type-P Descriptor is synchronized between the Session-Sender and Session-Reflector and whether different values are considered as error conditions and should be reported. We assume that by some means the Session-Sender and the Session-Reflector of the given TWAMP-Test session have been informed to use the same DSCP value. The same means, i.e., configuration, could be used to inform the
[RFC5357]的附录I未明确说明会话发送方和会话反射器之间如何同步P型描述符的值，以及不同的值是否被视为错误条件，是否应报告。我们假设通过某种方式，已通知给定TWAMP测试会话的会话发送方和会话反射器使用相同的DSCP值。同样的方法，即配置，可用于通知客户
Session-Reflector to support DSCP and ECN Monitoring mode by copying data from received TWAMP test packets. Then Session-Sender may be informed to use the Sender DSCP and ECN field in the reflected TWAMP test packet.
会话反射器通过从接收到的TWAMP测试数据包复制数据来支持DSCP和ECN监控模式。然后，可以通知会话发送方使用反射的TWAMP测试分组中的发送方DSCP和ECN字段。
In the TWAMP-Modes registry defined in [RFC5618], IANA has reserved a new DSCP and ECN Monitoring Capability as follows:
在[RFC5618]中定义的TWAMP模式注册表中，IANA保留了新的DSCP和ECN监控功能，如下所示：
+-----+---------------------------+---------------------+-----------+
| Bit | Description | Semantics | Reference |
| Pos | | Definition | |
+-----+---------------------------+---------------------+-----------+
| 8 | DSCP and ECN Monitoring | Section 2 | RFC 7750 |
| | Capability | | |
+-----+---------------------------+---------------------+-----------+
+-----+---------------------------+---------------------+-----------+
| Bit | Description | Semantics | Reference |
| Pos | | Definition | |
+-----+---------------------------+---------------------+-----------+
| 8 | DSCP and ECN Monitoring | Section 2 | RFC 7750 |
| | Capability | | |
+-----+---------------------------+---------------------+-----------+
Table 1: New Type-P Descriptor Monitoring Capability
表1：新型P型描述符监控能力
Monitoring of DSCP and ECN does not appear to introduce any additional security threat to hosts that communicate with TWAMP as defined in [RFC5357] and existing extensions [RFC6038]. Sections such as 3.2, 4, 4.1.2, 4.2, and 4.2.1 of [RFC5357] discuss unauthenticated, authenticated, and encrypted modes in varying degrees of detail. The security considerations that apply to any active measurement of live networks are relevant here as well. See the Security Considerations sections in [RFC4656] and [RFC5357].
对DSCP和ECN的监控似乎不会给与[RFC5357]和现有扩展[RFC6038]中定义的TWAMP通信的主机带来任何额外的安全威胁。[RFC5357]的第3.2、4、4.1.2、4.2和4.2.1节详细讨论了未经验证、验证和加密的模式。适用于实时网络的任何主动测量的安全注意事项也与此相关。请参阅[RFC4656]和[RFC5357]中的安全注意事项部分。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://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<http://www.rfc-editor.org/info/rfc2119>.
[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, DOI 10.17487/RFC2474, December 1998, <http://www.rfc-editor.org/info/rfc2474>.
[RFC2474]Nichols，K.，Blake，S.，Baker，F.，和D.Black，“IPv4和IPv6报头中区分服务字段（DS字段）的定义”，RFC 2474，DOI 10.17487/RFC2474，1998年12月<http://www.rfc-editor.org/info/rfc2474>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, DOI 10.17487/RFC3168, September 2001, <http://www.rfc-editor.org/info/rfc3168>.
[RFC3168]Ramakrishnan，K.，Floyd，S.，和D.Black，“向IP添加显式拥塞通知（ECN）”，RFC 3168，DOI 10.17487/RFC3168，2001年9月<http://www.rfc-editor.org/info/rfc3168>.
[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, <http://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<http://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, <http://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<http://www.rfc-editor.org/info/rfc5357>.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, DOI 10.17487/RFC5618, August 2009, <http://www.rfc-editor.org/info/rfc5618>.
[RFC5618]Morton，A.和K.Hedayat，“双向主动测量协议（TWAMP）的混合安全模式”，RFC 5618，DOI 10.17487/RFC5618，2009年8月<http://www.rfc-editor.org/info/rfc5618>.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement Protocol (TWAMP) Reflect Octets and Symmetrical Size Features", RFC 6038, DOI 10.17487/RFC6038, October 2010, <http://www.rfc-editor.org/info/rfc6038>.
[RFC6038]Morton，A.和L.Ciavattone，“双向主动测量协议（TWAMP）反映八位组和对称尺寸特征”，RFC 6038，DOI 10.17487/RFC6038，2010年10月<http://www.rfc-editor.org/info/rfc6038>.
[RFC3260] Grossman, D., "New Terminology and Clarifications for Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002, <http://www.rfc-editor.org/info/rfc3260>.
[RFC3260]Grossman，D.，“区分服务的新术语和澄清”，RFC 3260，DOI 10.17487/RFC3260，2002年4月<http://www.rfc-editor.org/info/rfc3260>.
Acknowledgements
致谢
The authors greatly appreciate thorough review and thoughtful comments by Bill Cerveny, Christofer Flinta, and Samita Chakrabarti.
作者非常感谢Bill Cerveny、Christofer Flinta和Samita Chakrabarti的全面审查和深思熟虑的评论。
Authors' Addresses
作者地址
Jonas Hedin Ericsson
乔纳斯·赫丁·爱立信
Email: jonas.hedin@ericsson.com
Email: jonas.hedin@ericsson.com
Greg Mirsky Ericsson
格雷格·米尔斯基·爱立信
Email: gregory.mirsky@ericsson.com
Email: gregory.mirsky@ericsson.com
Steve Baillargeon Ericsson
史蒂夫·伯拉金·爱立信
Email: steve.baillargeon@ericsson.com
Email: steve.baillargeon@ericsson.com