Internet Engineering Task Force (IETF)                  G. Fioccola, Ed.
Request for Comments: 8321                                    A. Capello
Category: Experimental                                       M. Cociglio
ISSN: 2070-1721                                           L. Castaldelli
                                                          Telecom Italia
                                                                 M. Chen
                                                                L. Zheng
                                                     Huawei Technologies
                                                               G. Mirsky
                                                              T. Mizrahi
                                                            January 2018

Alternate-Marking Method for Passive and Hybrid Performance Monitoring




This document describes a method to perform packet loss, delay, and jitter measurements on live traffic. This method is based on an Alternate-Marking (coloring) technique. A report is provided in order to explain an example and show the method applicability. This technology can be applied in various situations, as detailed in this document, and could be considered Passive or Hybrid depending on the application.


Status of This Memo


This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.

このドキュメントはInternet Standards Trackの仕様ではありません。試験、実験、評価のために公開されています。

This document defines an Experimental Protocol for the Internet community. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 7841.

このドキュメントでは、インターネットコミュニティの実験プロトコルを定義します。このドキュメントは、IETF(Internet Engineering Task Force)の製品です。これは、IETFコミュニティのコンセンサスを表しています。公開レビューを受け、インターネットエンジニアリングステアリンググループ(IESG)による公開が承認されました。 IESGによって承認されたすべてのドキュメントが、あらゆるレベルのインターネット標準の候補になるわけではありません。 RFC 7841のセクション2をご覧ください。

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at


Copyright Notice


Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.

Copyright(c)2018 IETF Trustおよびドキュメントの作成者として識別された人物。全著作権所有。

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( 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.

この文書は、BCP 78およびIETF文書に関するIETFトラストの法的規定(の対象であり、この文書の発行日に有効です。これらのドキュメントは、このドキュメントに関するあなたの権利と制限を説明しているため、注意深く確認してください。このドキュメントから抽出されたコードコンポーネントには、Trust Legal Provisionsのセクション4.eに記載されているSimplified BSD Licenseのテキストが含まれている必要があり、Simplified BSD Licenseに記載されているように保証なしで提供されます。

Table of Contents


   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Overview of the Method  . . . . . . . . . . . . . . . . . . .   5
   3.  Detailed Description of the Method  . . . . . . . . . . . . .   6
     3.1.  Packet Loss Measurement . . . . . . . . . . . . . . . . .   6
       3.1.1.  Coloring the Packets  . . . . . . . . . . . . . . . .  11
       3.1.2.  Counting the Packets  . . . . . . . . . . . . . . . .  12
       3.1.3.  Collecting Data and Calculating Packet Loss . . . . .  13
     3.2.  Timing Aspects  . . . . . . . . . . . . . . . . . . . . .  13
     3.3.  One-Way Delay Measurement . . . . . . . . . . . . . . . .  15
       3.3.1.  Single-Marking Methodology  . . . . . . . . . . . . .  15
       3.3.2.  Double-Marking Methodology  . . . . . . . . . . . . .  17
     3.4.  Delay Variation Measurement . . . . . . . . . . . . . . .  18
   4.  Considerations  . . . . . . . . . . . . . . . . . . . . . . .  18
     4.1.  Synchronization . . . . . . . . . . . . . . . . . . . . .  19
     4.2.  Data Correlation  . . . . . . . . . . . . . . . . . . . .  19
     4.3.  Packet Reordering . . . . . . . . . . . . . . . . . . . .  20
   5.  Applications, Implementation, and Deployment  . . . . . . . .  21
     5.1.  Report on the Operational Experiment  . . . . . . . . . .  22
       5.1.1.  Metric Transparency . . . . . . . . . . . . . . . . .  24
   6.  Hybrid Measurement  . . . . . . . . . . . . . . . . . . . . .  24
   7.  Compliance with Guidelines from RFC 6390  . . . . . . . . . .  25
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  27
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  28
     10.2.  Informative References . . . . . . . . . . . . . . . . .  29
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32
1. Introduction
1. はじめに

Nowadays, most Service Providers' networks carry traffic with contents that are highly sensitive to packet loss [RFC7680], delay [RFC7679], and jitter [RFC3393].


In view of this scenario, Service Providers need methodologies and tools to monitor and measure network performance with an adequate accuracy, in order to constantly control the quality of experience perceived by their customers. On the other hand, performance monitoring provides useful information for improving network management (e.g., isolation of network problems, troubleshooting, etc.).


A lot of work related to Operations, Administration, and Maintenance (OAM), which also includes performance monitoring techniques, has been done by Standards Developing Organizations (SDOs): [RFC7276] provides a good overview of existing OAM mechanisms defined in the IETF, ITU-T, and IEEE. In the IETF, a lot of work has been done on fault detection and connectivity verification, while a minor effort has been thus far dedicated to performance monitoring. The IPPM WG has defined standard metrics to measure network performance; however, the methods developed in this WG mainly refer to focus on Active measurement techniques. More recently, the MPLS WG has defined mechanisms for measuring packet loss, one-way and two-way delay, and delay variation in MPLS networks [RFC6374], but their applicability to Passive measurements has some limitations, especially for pure connection-less networks.

運用監視管理(OAM)に関連する多くの作業(パフォーマンス監視技術も含む)は、Standards Developing Organizations(SDO)によって行われています。[RFC7276]は、IETFで定義されている既存のOAMメカニズムの優れた概要を提供します。 ITU-T、およびIEEE。 IETFでは、障害の検出と接続の検証に関して多くの作業が行われていますが、これまでのところ、パフォーマンスの監視に少しの努力が費やされてきました。 IPPM WGは、ネットワークパフォーマンスを測定するための標準メトリックを定義しています。ただし、このWGで開発された方法は、主にアクティブ測定手法に焦点を当てることを示しています。最近では、MPLS WGはMPLSネットワーク[RFC6374]でのパケット損失、一方向および双方向の遅延、および遅延変動を測定するメカニズムを定義していますが、パッシブ測定への適用性には、特に純粋なコネクションレスネットワークに対していくつかの制限があります。 。

The lack of adequate tools to measure packet loss with the desired accuracy drove an effort to design a new method for the performance monitoring of live traffic, which is easy to implement and deploy. The effort led to the method described in this document: basically, it is a Passive performance monitoring technique, potentially applicable to any kind of packet-based traffic, including Ethernet, IP, and MPLS, both unicast and multicast. The method addresses primarily packet loss measurement, but it can be easily extended to one-way or two-way delay and delay variation measurements as well.


The method has been explicitly designed for Passive measurements, but it can also be used with Active probes. Passive measurements are usually more easily understood by customers and provide much better accuracy, especially for packet loss measurements.


RFC 7799 [RFC7799] defines Passive and Hybrid Methods of Measurement. In particular, Passive Methods of Measurement are based solely on observations of an undisturbed and unmodified packet stream of interest; Hybrid Methods are Methods of Measurement that use a combination of Active Methods and Passive Methods.

RFC 7799 [RFC7799]は、パッシブおよびハイブリッド測定方法を定義しています。特に、パッシブ測定方法は、対象となる妨害されていない変更されていないパケットストリームの観測のみに基づいています。ハイブリッドメソッドは、アクティブメソッドとパッシブメソッドの組み合わせを使用する測定方法です。

Taking into consideration these definitions, the Alternate-Marking Method could be considered Hybrid or Passive, depending on the case. In the case where the marking method is obtained by changing existing field values of the packets (e.g., the Differentiated Services Code Point (DSCP) field), the technique is Hybrid. In the case where the marking field is dedicated, reserved, and included in the protocol specification, the Alternate-Marking technique can be considered as Passive (e.g., Synonymous Flow Label as described in [SFL-FRAMEWORK] or OAM Marking Bits as described in [PM-MM-BIER]).

これらの定義を考慮すると、Alternate-Markingメソッドは、場合によってハイブリッドまたはパッシブと見なされます。パケットの既存のフィールド値(Differentiated Services Code Point(DSCP)フィールドなど)を変更してマーキング方法を取得する場合、この手法はハイブリッドです。マーキングフィールドが専用で、予約されており、プロトコル仕様に含まれている場合、代替マーキングテクニックはパッシブ([SFL-FRAMEWORK]で説明されているような同義フローラベル)または[PM-MM-BIER])。

The advantages of the method described in this document are:


o easy implementation: it can be implemented by using features already available on major routing platforms, as described in Section 5.1, or by applying an optimized implementation of the method for both legacy and newest technologies;

o 簡単な実装:セクション5.1で説明されているように、主要なルーティングプラットフォームですでに利用可能な機能を使用するか、レガシー技術と最新技術の両方にメソッドの最適化された実装を適用することで実装できます。

o low computational effort: the additional load on processing is negligible;

o 低い計算労力:処理への追加の負荷は無視できます。

o accurate packet loss measurement: single packet loss granularity is achieved with a Passive measurement;

o 正確なパケット損失測定:単一パケット損失の粒度は、パッシブ測定で達成されます。

o potential applicability to any kind of packet-based or frame-based traffic: Ethernet, IP, MPLS, etc., and both unicast and multicast;

o あらゆる種類のパケットベースまたはフレームベースのトラフィックへの潜在的な適用性:イーサネット、IP、MPLSなど、およびユニキャストとマルチキャストの両方。

o robustness: the method can tolerate out-of-order packets, and it's not based on "special" packets whose loss could have a negative impact;

o 堅牢性:このメソッドは、順序の乱れたパケットを許容でき、損失が悪影響を与える可能性のある「特殊な」パケットに基づいていません。

o flexibility: all the timestamp formats are allowed, because they are managed out of band. The format (the Network Time Protocol (NTP) [RFC5905] or the IEEE 1588 Precision Time Protocol (PTP) [IEEE-1588]) depends on the precision you want; and

o 柔軟性:帯域外で管理されるため、すべてのタイムスタンプ形式が許可されます。形式(Network Time Protocol(NTP)[RFC5905]またはIEEE 1588 Precision Time Protocol(PTP)[IEEE-1588])は、希望する精度によって異なります。そして

o no interoperability issues: the features required to experiment and test the method (as described in Section 5.1) are available on all current routing platforms. Both a centralized or distributed solution can be used to harvest data from the routers.

o 相互運用性の問題はありません。メソッドの実験とテストに必要な機能(セクション5.1で説明)は、現在のすべてのルーティングプラットフォームで使用できます。集中型ソリューションと分散型ソリューションの両方を使用して、ルーターからデータを収集できます。

The method doesn't raise any specific need for protocol extension, but it could be further improved by means of some extension to existing protocols. Specifically, the use of Diffserv bits for coloring the packets could not be a viable solution in some cases: a standard method to color the packets for this specific application could be beneficial.


1.1. Requirements Language
1.1. 要件言語

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.


2. Overview of the Method
2. 方法の概要

In order to perform packet loss measurements on a production traffic flow, different approaches exist. The most intuitive one consists in numbering the packets so that each router that receives the flow can immediately detect a packet that is missing. This approach, though very simple in theory, is not simple to achieve: it requires the insertion of a sequence number into each packet, and the devices must be able to extract the number and check it in real time. Such a task can be difficult to implement on live traffic: if UDP is used as the transport protocol, the sequence number is not available; on the other hand, if a higher-layer sequence number (e.g., in the RTP header) is used, extracting that information from each packet and processing it in real time could overload the device.


An alternate approach is to count the number of packets sent on one end, count the number of packets received on the other end, and compare the two values. This operation is much simpler to implement, but it requires the devices performing the measurement to be in sync: in order to compare two counters, it is required that they refer exactly to the same set of packets. Since a flow is continuous and cannot be stopped when a counter has to be read, it can be difficult to determine exactly when to read the counter. A possible solution to overcome this problem is to virtually split the flow in consecutive blocks by periodically inserting a delimiter so that each counter refers exactly to the same block of packets. The delimiter could be, for example, a special packet inserted artificially into the flow. However, delimiting the flow using specific packets has some limitations. First, it requires generating additional packets within the flow and requires the equipment to be able to process those packets. In addition, the method is vulnerable to out-of-order reception of delimiting packets and, to a lesser extent, to their loss.


The method proposed in this document follows the second approach, but it doesn't use additional packets to virtually split the flow in blocks. Instead, it "marks" the packets so that the packets belonging to the same block will have the same color, whilst consecutive blocks will have different colors. Each change of color represents a sort of auto-synchronization signal that guarantees the consistency of measurements taken by different devices along the path (see also [IP-MULTICAST-PM] and [OPSAWG-P3M], where this technique was introduced).


Figure 1 represents a very simple network and shows how the method can be used to measure packet loss on different network segments: by enabling the measurement on several interfaces along the path, it is possible to perform link monitoring, node monitoring, or end-to-end monitoring. The method is flexible enough to measure packet loss on any segment of the network and can be used to isolate the faulty element.

図1は非常に単純なネットワークを表しており、この方法を使用してさまざまなネットワークセグメントのパケット損失を測定する方法を示しています。パスに沿った複数のインターフェイスで測定を有効にすることで、リンクモニタリング、ノードモニタリング、またはエンドツーエンドを実行できます。 -監視を終了する。この方法は、ネットワークの任意のセグメントでパケット損失を測定するのに十分な柔軟性があり、障害のある要素を特定するために使用できます。

                               Traffic Flow
          +------+       +------+       +------+       +------+
      ---<>  R1  <>-----<>  R2  <>-----<>  R3  <>-----<>  R4  <>---
          +------+       +------+       +------+       +------+
          .              .      .              .       .      .
          .              .      .              .       .      .
          .              <------>              <------->      .
          .          Node Packet Loss      Link Packet Loss   .
          .                                                   .
                           End-to-End Packet Loss

Figure 1: Available Measurements


3. Detailed Description of the Method
3. メソッドの詳細な説明

This section describes, in detail, how the method operates. A special emphasis is given to the measurement of packet loss, which represents the core application of the method, but applicability to delay and jitter measurements is also considered.


3.1. Packet Loss Measurement
3.1. パケットロス測定

The basic idea is to virtually split traffic flows into consecutive blocks: each block represents a measurable entity unambiguously recognizable by all network devices along the path. By counting the number of packets in each block and comparing the values measured by different network devices along the path, it is possible to measure packet loss occurred in any single block between any two points.


As discussed in the previous section, a simple way to create the blocks is to "color" the traffic (two colors are sufficient), so that packets belonging to different consecutive blocks will have different colors. Whenever the color changes, the previous block terminates and the new one begins. Hence, all the packets belonging to the same block will have the same color and packets of different consecutive blocks will have different colors. The number of packets in each block depends on the criterion used to create the blocks:


o if the color is switched after a fixed number of packets, then each block will contain the same number of packets (except for any losses); and

o 一定数のパケットの後に色が切り替えられる場合、各ブロックには同じ数のパケットが含まれます(損失を除く)。そして

o if the color is switched according to a fixed timer, then the number of packets may be different in each block depending on the packet rate.

o 固定タイマーに従って色が切り替えられる場合、パケット数に応じて、ブロックごとにパケット数が異なる場合があります。

The following figure shows how a flow looks like when it is split in traffic blocks with colored packets.


A: packet with A coloring B: packet with B coloring


            |           |           |           |           |
            |           |    Traffic Flow       |           |
       ...  |  Block 5  |  Block 4  |  Block 3  |  Block 2  |  Block 1
            |           |           |           |           |

Figure 2: Traffic Coloring


Figure 3 shows how the method can be used to measure link packet loss between two adjacent nodes.


Referring to the figure, let's assume we want to monitor the packet loss on the link between two routers: router R1 and router R2. According to the method, the traffic is colored alternatively with two different colors: A and B. Whenever the color changes, the transition generates a sort of square-wave signal, as depicted in the following figure.


   Color A   ----------+           +-----------+           +----------
                       |           |           |           |
   Color B             +-----------+           +-----------+
              Block n        ...      Block 3     Block 2     Block 1
            <---------> <---------> <---------> <---------> <--------->
                                Traffic Flow

Figure 3: Computation of Link Packet Loss


Traffic coloring can be done by R1 itself if the traffic is not already colored. R1 needs two counters, C(A)R1 and C(B)R1, on its egress interface: C(A)R1 counts the packets with color A and C(B)R1 counts those with color B. As long as traffic is colored as A, only counter C(A)R1 will be incremented, while C(B)R1 is not incremented; conversely, when the traffic is colored as B, only C(B)R1 is incremented. C(A)R1 and C(B)R1 can be used as reference values to determine the packet loss from R1 to any other measurement point down the path. Router R2, similarly, will need two counters on its ingress interface, C(A)R2 and C(B)R2, to count the packets received on that interface and colored with A and B, respectively. When an A block ends, it is possible to compare C(A)R1 and C(A)R2 and calculate the packet loss within the block; similarly, when the successive B block terminates, it is possible to compare C(B)R1 with C(B)R2, and so on, for every successive block.

トラフィックがまだ色付けされていない場合、トラフィックの色付けはR1自体によって行うことができます。 R1には、その出力インターフェイスに2つのカウンターC(A)R1とC(B)R1が必要です。C(A)R1は色Aのパケットをカウントし、C(B)R1は色Bのパケットをカウントします。トラフィックがAとして色分けされている場合、C(A)R1のみがインクリメントされ、C(B)R1はインクリメントされません。逆に、トラフィックがBとして色分けされている場合、C(B)R1のみが増分されます。 C(A)R1とC(B)R1は、R1からパスの他の測定ポイントまでのパケット損失を決定するための参照値として使用できます。同様に、ルータR2は、そのインターフェイスで受信され、それぞれAおよびBで色分けされたパケットをカウントするために、その入力インターフェイスに2つのカウンタC(A)R2およびC(B)R2を必要とします。 Aブロックが終了すると、C(A)R1とC(A)R2を比較して、ブロック内のパケット損失を計算できます。同様に、連続するBブロックが終了すると、連続するブロックごとにC(B)R1をC(B)R2と比較することができます。

Likewise, by using two counters on the R2 egress interface, it is possible to count the packets sent out of the R2 interface and use them as reference values to calculate the packet loss from R2 to any measurement point down R2.


Using a fixed timer for color switching offers better control over the method: the (time) length of the blocks can be chosen large enough to simplify the collection and the comparison of measures taken by different network devices. It's preferable to read the value of the counters not immediately after the color switch: some packets could arrive out of order and increment the counter associated with the previous block (color), so it is worth waiting for some time. A safe choice is to wait L/2 time units (where L is the duration for each block) after the color switch, to read the still counter of the previous color, so the possibility of reading a running counter instead of a still one is minimized. The drawback is that the longer the duration of the block, the less frequent the measurement can be taken.

色の切り替えに固定タイマーを使用すると、方法をより適切に制御できます。ブロックの(時間)長さは、さまざまなネットワークデバイスで行われる測定の収集と比較を簡素化するのに十分な長さに選択できます。カラースイッチの直後ではなく、カウンターの値を読み取ることをお勧めします。一部のパケットは順不同で到着し、前のブロック(カラー)に関連付けられたカウンターをインクリメントする可能性があるため、しばらく待つ価値があります。安全な選択は、色の切り替え後にL / 2時間単位(Lは各ブロックの期間)を待って、前の色の静止カウンターを読み取ることです。そのため、静止カウンターの代わりに実行カウンターを読み取る可能性があります。最小化。欠点は、ブロックの期間が長いほど、測定の頻度が少なくなることです。

The following table shows how the counters can be used to calculate the packet loss between R1 and R2. The first column lists the sequence of traffic blocks, while the other columns contain the counters of A-colored packets and B-colored packets for R1 and R2. In this example, we assume that the values of the counters are reset to zero whenever a block ends and its associated counter has been read: with this assumption, the table shows only relative values, which is the exact number of packets of each color within each block. If the values of the counters were not reset, the table would contain cumulative values, but the relative values could be determined simply by the difference from the value of the previous block of the same color.


The color is switched on the basis of a fixed timer (not shown in the table), so the number of packets in each block is different.


           | Block | C(A)R1 | C(B)R1 | C(A)R2 | C(B)R2 | Loss |
           | 1     | 375    | 0      | 375    | 0      | 0    |
           | 2     | 0      | 388    | 0      | 388    | 0    |
           | 3     | 382    | 0      | 381    | 0      | 1    |
           | 4     | 0      | 377    | 0      | 374    | 3    |
           | ...   | ...    | ...    | ...    | ...    | ...  |
           | 2n    | 0      | 387    | 0      | 387    | 0    |
           | 2n+1  | 379    | 0      | 377    | 0      | 2    |

Table 1: Evaluation of Counters for Packet Loss Measurements


During an A block (blocks 1, 3, and 2n+1), all the packets are A-colored; therefore, the C(A) counters are incremented to the number seen on the interface, while C(B) counters are zero. Conversely, during a B block (blocks 2, 4, and 2n), all the packets are B-colored: C(A) counters are zero, while C(B) counters are incremented.

Aブロック(ブロック1、3、および2n + 1)の間、すべてのパケットはAカラーです。したがって、C(A)カウンターはインターフェイスで見られる数に増加しますが、C(B)カウンターはゼロです。逆に、Bブロック(ブロック2、4、および2n)の間、すべてのパケットはB色です。C(A)カウンターはゼロですが、C(B)カウンターは増分されます。

When a block ends (because of color switching), the relative counters stop incrementing; it is possible to read them, compare the values measured on routers R1 and R2, and calculate the packet loss within that block.


For example, looking at the table above, during the first block (A-colored), C(A)R1 and C(A)R2 have the same value (375), which corresponds to the exact number of packets of the first block (no loss). Also, during the second block (B-colored), R1 and R2 counters have the same value (388), which corresponds to the number of packets of the second block (no loss). During the third and fourth blocks, R1 and R2 counters are different, meaning that some packets have been lost: in the example, one single packet (382-381) was lost during block three, and three packets (377-374) were lost during block four.

たとえば、上の表を見ると、最初のブロック(A色)の間、C(A)R1とC(A)R2は同じ値(375)を持ちます。これは、最初のブロックの正確なパケット数に対応します。 (損失なし)。また、2番目のブロック(B色)の間、R1およびR2カウンターは同じ値(388)を持ち、これは2番目のブロックのパケット数に対応します(損失なし)。 3番目と4番目のブロックでは、R1とR2のカウンターが異なります。つまり、一部のパケットが失われました。この例では、ブロック3で1つのパケット(382-381)が失われ、3つのパケット(377-374)が失われました。ブロック4の間。

The method applied to R1 and R2 can be extended to any other router and applied to more complex networks, as far as the measurement is enabled on the path followed by the traffic flow(s) being observed.


It's worth mentioning two different strategies that can be used when implementing the method:


o flow-based: the flow-based strategy is used when only a limited number of traffic flows need to be monitored. According to this strategy, only a subset of the flows is colored. Counters for packet loss measurements can be instantiated for each single flow, or for the set as a whole, depending on the desired granularity. A relevant problem with this approach is the necessity to know in advance the path followed by flows that are subject to measurement. Path rerouting and traffic load-balancing increase the issue complexity, especially for unicast traffic. The problem is easier to solve for multicast traffic, where load-balancing is seldom used and static joins are frequently used to force traffic forwarding and replication.

o フローベース:フローベースの戦略は、限られた数のトラフィックフローのみを監視する必要がある場合に使用されます。この戦略によれば、フローのサブセットのみが色付けされます。パケット損失測定用のカウンターは、必要な粒度に応じて、単一のフローごとに、またはセット全体に対してインスタンス化できます。このアプローチに関連する問題は、測定の対象となるフローがたどるパスを事前に知る必要があることです。パスの再ルーティングとトラフィックの負荷分散により、特にユニキャストトラフィックの場合、問題が複雑になります。負荷分散がほとんど使用されず、トラフィックの転送と複製を強制するために静的結合が頻繁に使用されるマルチキャストトラフィックの場合、問題は解決しやすくなります。

o link-based: measurements are performed on all the traffic on a link-by-link basis. The link could be a physical link or a logical link. Counters could be instantiated for the traffic as a whole or for each traffic class (in case it is desired to monitor each class separately), but in the second case, a couple of counters are needed for each class.

o リンクベース:すべてのトラフィックに対してリンクごとに測定が実行されます。リンクは、物理リンクまたは論理リンクです。カウンタは、トラフィック全体またはトラフィッククラスごとにインスタンス化できます(各クラスを個別に監視する必要がある場合)が、2番目のケースでは、クラスごとにいくつかのカウンタが必要です。

As mentioned, the flow-based measurement requires the identification of the flow to be monitored and the discovery of the path followed by the selected flow. It is possible to monitor a single flow or multiple flows grouped together, but in this case, measurement is consistent only if all the flows in the group follow the same path. Moreover, if a measurement is performed by grouping many flows, it is not possible to determine exactly which flow was affected by packet loss. In order to have measures per single flow, it is necessary to configure counters for each specific flow. Once the flow(s) to be monitored has been identified, it is necessary to configure the monitoring on the proper nodes. Configuring the monitoring means configuring the rule to intercept the traffic and configuring the counters to count the packets. To have just an end-to-end monitoring, it is sufficient to enable the monitoring on the first-and last-hop routers of the path: the mechanism is completely transparent to intermediate nodes and independent from the path followed by traffic flows. On the contrary, to monitor the flow on a hop-by-hop basis along its whole path, it is necessary to enable the monitoring on every node from the source to the destination. In case the exact path followed by the flow is not known a priori (i.e., the flow has multiple paths to reach the destination), it is necessary to enable the monitoring system on every path: counters on interfaces traversed by the flow will report packet count, whereas counters on other interfaces will be null.


3.1.1. Coloring the Packets
3.1.1. パケットのカラーリング

The coloring operation is fundamental in order to create packet blocks. This implies choosing where to activate the coloring and how to color the packets.


In case of flow-based measurements, the flow to monitor can be defined by a set of selection rules (e.g., header fields) used to match a subset of the packets; in this way, it is possible to control the number of involved nodes, the path followed by the packets, and the size of the flows. It is possible, in general, to have multiple coloring nodes or a single coloring node that is easier to manage and doesn't raise any risk of conflict. Coloring in multiple nodes can be done, and the requirement is that the coloring must change periodically between the nodes according to the timing considerations in Section 3.2; so every node that is designated as a measurement point along the path should be able to identify unambiguously the colored packets. Furthermore, [MULTIPOINT-ALT-MM] generalizes the coloring for multipoint-to-multipoint flow. In addition, it can be advantageous to color the flow as close as possible to the source because it allows an end-to-end measure if a measurement point is enabled on the last-hop router as well.


For link-based measurements, all traffic needs to be colored when transmitted on the link. If the traffic had already been colored, then it has to be re-colored because the color must be consistent on the link. This means that each hop along the path must (re-)color the traffic; the color is not required to be consistent along different links.


Traffic coloring can be implemented by setting a specific bit in the packet header and changing the value of that bit periodically. How to choose the marking field depends on the application and is out of scope here. However, some applications are reported in Section 5.


3.1.2. Counting the Packets
3.1.2. パケットのカウント

For flow-based measurements, assuming that the coloring of the packets is performed only by the source nodes, the nodes between source and destination (included) have to count the colored packets that they receive and forward: this operation can be enabled on every router along the path or only on a subset, depending on which network segment is being monitored (a single link, a particular metro area, the backbone, or the whole path). Since the color switches periodically between two values, two counters (one for each value) are needed: one counter for packets with color A and one counter for packets with color B. For each flow (or group of flows) being monitored and for every interface where the monitoring is Active, a couple of counters are needed. For example, in order to separately monitor three flows on a router with four interfaces involved, 24 counters are needed (two counters for each of the three flows on each of the four interfaces). Furthermore, [MULTIPOINT-ALT-MM] generalizes the counting for multipoint-to-multipoint flow.


In case of link-based measurements, the behavior is similar except that coloring and counting operations are performed on a link-by-link basis at each endpoint of the link.


Another important aspect to take into consideration is when to read the counters: in order to count the exact number of packets of a block, the routers must perform this operation when that block has ended; in other words, the counter for color A must be read when the current block has color B, in order to be sure that the value of the counter is stable. This task can be accomplished in two ways. The general approach suggests reading the counters periodically, many times during a block duration, and comparing these successive readings: when the counter stops incrementing, it means that the current block has ended, and its value can be elaborated safely. Alternatively, if the coloring operation is performed on the basis of a fixed timer, it is possible to configure the reading of the counters according to that timer: for example, reading the counter for color A every period in the middle of the subsequent block with color B is a safe choice. A sufficient margin should be considered between the end of a block and the reading of the counter, in order to take into account any out-of-order packets.


3.1.3. Collecting Data and Calculating Packet Loss
3.1.3. データの収集とパケット損失の計算

The nodes enabled to perform performance monitoring collect the value of the counters, but they are not able to directly use this information to measure packet loss, because they only have their own samples. For this reason, an external Network Management System (NMS) can be used to collect and elaborate data and to perform packet loss calculation. The NMS compares the values of counters from different nodes and can calculate if some packets were lost (even a single packet) and where those packets were lost.

パフォーマンス監視を実行できるノードは、カウンターの値を収集しますが、独自のサンプルしかないため、この情報を直接使用してパケット損失を測定することはできません。このため、外部のネットワーク管理システム(NMS)を使用して、データを収集および生成し、パケット損失の計算を実行できます。 NMSは、さまざまなノードのカウンターの値を比較し、一部のパケットが失われた場合(単一のパケットであっても)、それらのパケットが失われた場所を計算できます。

The value of the counters needs to be transmitted to the NMS as soon as it has been read. This can be accomplished by using SNMP or FTP and can be done in Push Mode or Polling Mode. In the first case, each router periodically sends the information to the NMS; in the latter case, it is the NMS that periodically polls routers to collect information. In any case, the NMS has to collect all the relevant values from all the routers within one cycle of the timer.


It would also be possible to use a protocol to exchange values of counters between the two endpoints in order to let them perform the packet loss calculation for each traffic direction.


A possible approach for the performance measurement (PM) architecture is explained in [COLORING], while [IP-FLOW-REPORT] introduces new information elements of IP Flow Information Export (IPFIX) [RFC7011].


3.2. Timing Aspects
3.2. タイミングの側面

This document introduces two color-switching methods: one is based on a fixed number of packets, and the other is based on a fixed timer. But the method based on a fixed timer is preferable because it is more deterministic, and it will be considered in the rest of the document.


In general, clocks in network devices are not accurate and for this reason, there is a clock error between the measurement points R1 and R2. But, to implement the methodology, they must be synchronized to the same clock reference with an accuracy of +/- L/2 time units, where L is the fixed time duration of the block. So each colored packet can be assigned to the right batch by each router. This is because the minimum time distance between two packets of the same color but that belong to different batches is L time units.

一般に、ネットワークデバイスのクロックは正確ではないため、測定ポイントR1とR2の間にクロックエラーがあります。ただし、この方法論を実装するには、+ /-L / 2時間単位の精度で同じクロック基準に同期させる必要があります。ここで、Lはブロックの固定期間です。したがって、各色のパケットは、各ルーターによって適切なバッチに割り当てることができます。これは、同じ色で異なるバッチに属する2つのパケット間の最小時間距離がL時間単位であるためです。

In practice, in addition to clock errors, the delay between measurement points also affects the implementation of the methodology because each packet can be delayed differently, and this can produce out of order at batch boundaries. This means that, without considering clock error, we wait L/2 after color switching to be sure to take a still counter.

実際には、クロックエラーに加えて、測定ポイント間の遅延も方法論の実装に影響を与えます。これは、各パケットの遅延が異なるため、バッチ境界で順序が乱れる可能性があるためです。これは、クロックエラーを考慮せずに、色の切り替え後にL / 2待機して、確実に静止カウンターを取得することを意味します。

In summary, we need to take into account two contributions: clock error between network devices and the interval we need to wait to avoid packets being out of order because of network delay.


The following figure explains both issues.


                |                   L                    |
                |       L/2                   L/2        |
                |<===>|                            |<===>|
                   d  |                            |   d
                       available counting interval

Figure 4: Timing Aspects


It is assumed that all network devices are synchronized to a common reference time with an accuracy of +/- A/2. Thus, the difference between the clock values of any two network devices is bounded by A.

すべてのネットワークデバイスは、+ /-A / 2の精度で共通の基準時間に同期していると想定されています。したがって、任意の2つのネットワークデバイスのクロック値の差はAによって制限されます。

The guard band d is given by:


d = A + D_max - D_min,

d = A + D_max-D_min、

where A is the clock accuracy, D_max is an upper bound on the network delay between the network devices, and D_min is a lower bound on the delay.


The available counting interval is L - 2d that must be > 0.


The condition that must be satisfied and is a requirement on the synchronization accuracy is:


d < L/2.

d <L / 2。

3.3. One-Way Delay Measurement
3.3. 一方向遅延測定

The same principle used to measure packet loss can be applied also to one-way delay measurement. There are three alternatives, as described hereinafter.


Note that, for all the one-way delay alternatives described in the next sections, by summing the one-way delays of the two directions of a path, it is always possible to measure the two-way delay (round-trip "virtual" delay).


3.3.1. Single-Marking Methodology
3.3.1. シングルマーキング方法論

The alternation of colors can be used as a time reference to calculate the delay. Whenever the color changes (which means that a new block has started), a network device can store the timestamp of the first packet of the new block; that timestamp can be compared with the timestamp of the same packet on a second router to compute packet delay. When looking at Figure 2, R1 stores the timestamp TS(A1)R1 when it sends the first packet of block 1 (A-colored), the timestamp TS(B2)R1 when it sends the first packet of block 2 (B-colored), and so on for every other block. R2 performs the same operation on the receiving side, recording TS(A1)R2, TS(B2)R2, and so on. Since the timestamps refer to specific packets (the first packet of each block), we are sure that timestamps compared to compute delay refer to the same packets. By comparing TS(A1)R1 with TS(A1)R2 (and similarly TS(B2)R1 with TS(B2)R2, and so on), it is possible to measure the delay between R1 and R2. In order to have more measurements, it is possible to take and store more timestamps, referring to other packets within each block.

色の変化は、遅延を計算するための時間基準として使用できます。色が変化するたびに(つまり、新しいブロックが開始したことを意味します)、ネットワークデバイスは新しいブロックの最初のパケットのタイムスタンプを保存できます。そのタイムスタンプを2番目のルーターの同じパケットのタイムスタンプと比較して、パケット遅延を計算できます。図2を見ると、R1は、ブロック1の最初のパケット(A色)を送信するときにタイムスタンプTS(A1)R1を保存し、ブロック2の最初のパケット(B色)を送信するときにタイムスタンプTS(B2)R1を保存します。 )、その他すべてのブロックについても同様です。 R2は受信側で同じ操作を実行し、TS(A1)R2、TS(B2)R2などを記録します。タイムスタンプは特定のパケット(各ブロックの最初のパケット)を参照しているため、計算遅延と比較したタイムスタンプは同じパケットを参照していることが確実です。 TS(A1)R1とTS(A1)R2(および同様にTS(B2)R1とTS(B2)R2など)を比較することにより、R1とR2の間の遅延を測定できます。より多くの測定値を取得するために、各ブロック内の他のパケットを参照して、より多くのタイムスタンプを取得して保存することが可能です。

In order to coherently compare timestamps collected on different routers, the clocks on the network nodes must be in sync. Furthermore, a measurement is valid only if no packet loss occurs and if packet misordering can be avoided; otherwise, the first packet of a block on R1 could be different from the first packet of the same block on R2 (for instance, if that packet is lost between R1 and R2 or it arrives after the next one).


The following table shows how timestamps can be used to calculate the delay between R1 and R2. The first column lists the sequence of blocks, while other columns contain the timestamp referring to the first packet of each block on R1 and R2. The delay is computed as a difference between timestamps. For the sake of simplicity, all the values are expressed in milliseconds.


      | Block | TS(A)R1 | TS(B)R1 | TS(A)R2 | TS(B)R2 | Delay R1-R2 |
      | 1     | 12.483  | -       | 15.591  | -       | 3.108       |
      | 2     | -       | 6.263   | -       | 9.288   | 3.025       |
      | 3     | 27.556  | -       | 30.512  | -       | 2.956       |
      |       | -       | 18.113  | -       | 21.269  | 3.156       |
      | ...   | ...     | ...     | ...     | ...     | ...         |
      | 2n    | 77.463  | -       | 80.501  | -       | 3.038       |
      | 2n+1  | -       | 24.333  | -       | 27.433  | 3.100       |

Table 2: Evaluation of Timestamps for Delay Measurements


The first row shows timestamps taken on R1 and R2, respectively, and refers to the first packet of block 1 (which is A-colored). Delay can be computed as a difference between the timestamp on R2 and the timestamp on R1. Similarly, the second row shows timestamps (in milliseconds) taken on R1 and R2 and refers to the first packet of block 2 (which is B-colored). By comparing timestamps taken on different nodes in the network and referring to the same packets (identified using the alternation of colors), it is possible to measure delay on different network segments.


For the sake of simplicity, in the above example, a single measurement is provided within a block, taking into account only the first packet of each block. The number of measurements can be easily increased by considering multiple packets in the block: for instance, a timestamp could be taken every N packets, thus generating multiple delay measurements. Taking this to the limit, in principle, the delay could be measured for each packet by taking and comparing the corresponding timestamps (possible but impractical from an implementation point of view).

簡単にするために、上記の例では、各ブロックの最初のパケットのみを考慮して、ブロック内で単一の測定が提供されています。ブロック内の複数のパケットを考慮することで、測定数を簡単に増やすことができます。たとえば、Nパケットごとにタイムスタンプを取得して、複数の遅延測定を生成できます。これを限界までとると、原則として、対応するタイムスタンプを取得して比較することにより、各パケットの遅延を測定できます(実装の観点からは可能ですが非現実的です)。 Mean Delay 平均遅延

As mentioned before, the method previously exposed for measuring the delay is sensitive to out-of-order reception of packets. In order to overcome this problem, a different approach has been considered: it is based on the concept of mean delay. The mean delay is calculated by considering the average arrival time of the packets within a single block. The network device locally stores a timestamp for each packet received within a single block: summing all the timestamps and dividing by the total number of packets received, the average arrival time for that block of packets can be calculated. By subtracting the average arrival times of two adjacent devices, it is possible to calculate the mean delay between those nodes. When computing the mean delay, the measurement error could be augmented by accumulating the measurement error of a lot of packets. This method is robust to out-of-order packets and also to packet loss (only a small error is introduced). Moreover, it greatly reduces the number of timestamps (only one per block for each network device) that have to be collected by the management system. On the other hand, it only gives one measure for the duration of the block (for instance, 5 minutes), and it doesn't give the minimum, maximum, and median delay values [RFC6703]. This limitation could be overcome by reducing the duration of the block (for instance, from 5 minutes to a few seconds), which implicates a highly optimized implementation of the method.

前述のように、遅延を測定するために以前に公開された方法は、パケットの順不同の受信に敏感です。この問題を克服するために、別のアプローチが検討されています。それは平均遅延の概念に基づいています。平均遅延は、単一ブロック内のパケットの平均到着時間を考慮して計算されます。ネットワークデバイスは、単一のブロック内で受信した各パケットのタイムスタンプをローカルに保存します。すべてのタイムスタンプを合計し、受信したパケットの総数で除算すると、そのパケットブロックの平均到着時間を計算できます。 2つの隣接デバイスの平均到着時間を差し引くことにより、それらのノード間の平均遅延を計算できます。平均遅延を計算するとき、多くのパケットの測定誤差を累積することにより、測定誤差が増大する可能性があります。この方法は、順序の乱れたパケットやパケット損失に対しても堅牢です(小さなエラーのみが導入されます)。さらに、管理システムが収集する必要があるタイムスタンプの数(各ネットワークデバイスのブロックごとに1つのみ)を大幅に削減します。一方、それはブロックの期間(たとえば、5分)の1つの測定値のみを提供し、最小、最大、および中央値の遅延値は提供しません[RFC6703]。この制限は、メソッドの高度に最適化された実装に関係するブロックの期間を短縮することで克服できます(たとえば、5分から数秒に)。

3.3.2. Double-Marking Methodology
3.3.2. ダブルマーキング方法論

The Single-Marking methodology for one-way delay measurement is sensitive to out-of-order reception of packets. The first approach to overcome this problem has been described before and is based on the concept of mean delay. But the limitation of mean delay is that it doesn't give information about the delay value's distribution for the duration of the block. Additionally, it may be useful to have not only the mean delay but also the minimum, maximum, and median delay values and, in wider terms, to know more about the statistic distribution of delay values. So, in order to have more information about the delay and to overcome out-of-order issues, a different approach can be introduced; it is based on a Double-Marking methodology.


Basically, the idea is to use the first marking to create the alternate flow and, within this colored flow, a second marking to select the packets for measuring delay/jitter. The first marking is needed for packet loss and mean delay measurement. The second marking creates a new set of marked packets that are fully identified over the network, so that a network device can store the timestamps of these packets; these timestamps can be compared with the timestamps of the same packets on a second router to compute packet delay values for each packet. The number of measurements can be easily increased by changing the frequency of the second marking. But the frequency of the second marking must not be too high in order to avoid out-of-order issues. Between packets with the second marking, there should be a security time gap (e.g., this gap could be, at the minimum, the mean network delay calculated with the previous methodology) to avoid out-of-order issues and also to have a number of measurement packets that are rate independent. If a second-marking packet is lost, the delay measurement for the considered block is corrupted and should be discarded.

基本的には、最初のマーキングを使用して代替フローを作成し、このカラーフロー内で2番目のマーキングを使用して、遅延/ジッターを測定するパケットを選択するという考え方です。最初のマーキングは、パケット損失と平均遅延の測定に必要です。 2番目のマーキングでは、ネットワーク上で完全に識別されるマーク付きパケットの新しいセットが作成されるため、ネットワークデバイスはこれらのパケットのタイムスタンプを保存できます。これらのタイムスタンプを2番目のルーターの同じパケットのタイムスタンプと比較して、各パケットのパケット遅延値を計算できます。 2番目のマーキングの頻度を変更することで、測定回数を簡単に増やすことができます。しかし、2番目のマーキングの頻度は、順不同の問題を回避するために高すぎてはなりません。 2番目のマーキングのあるパケット間には、セキュリティタイムギャップが必要です(たとえば、このギャップは、少なくとも、前の方法で計算された平均ネットワーク遅延である可能性があります)。レートに依存しない測定パケットの数。 2番目のマーキングパケットが失われた場合、考慮されているブロックの遅延測定は破損しているため、破棄する必要があります。

Mean delay is calculated on all the packets of a sample and is a simple computation to be performed for a Single-Marking Method. In some cases, the mean delay measure is not sufficient to characterize the sample, and more statistics of delay extent data are needed, e.g., percentiles, variance, and median delay values. The conventional range (maximum-minimum) should be avoided for several reasons, including stability of the maximum delay due to the influence by outliers. RFC 5481 [RFC5481], Section 6.5 highlights how the 99.9th percentile of delay and delay variation is more helpful to performance planners. To overcome this drawback, the idea is to couple the mean delay measure for the entire batch with a Double-Marking Method, where a subset of batch packets is selected for extensive delay calculation by using a second marking. In this way, it is possible to perform a detailed analysis on these double-marked packets. Please note that there are classic algorithms for median and variance calculation, but they are out of the scope of this document. The comparison between the mean delay for the entire batch and the mean delay on these double-marked packets gives useful information since it is possible to understand if the Double-Marking measurements are actually representative of the delay trends.

平均遅延は、サンプルのすべてのパケットで計算され、シングルマーキング方式で実行される単純な計算です。場合によっては、平均遅延測定はサンプルを特徴付けるのに十分ではなく、遅延範囲データのより多くの統計、たとえば、パーセンタイル、分散、および中央値遅延値が必要です。従来の範囲(最大-最小)は、外れ値の影響による最大遅延の安定性など、いくつかの理由で回避する必要があります。 RFC 5481 [RFC5481]のセクション6.5は、遅延の99.9パーセンタイルと遅延変動がパフォーマンスプランナーにとってどのように役立つかを強調しています。この欠点を克服するためのアイデアは、バッチ全体の平均遅延測定値をダブルマーキング法と組み合わせることです。この方法では、2番目のマーキングを使用してバッチパケットのサブセットを選択し、広範な遅延を計算します。このようにして、これらの二重マークされたパケットに対して詳細な分析を実行することが可能です。中央値と分散の計算には従来のアルゴリズムがありますが、それらはこのドキュメントの範囲外であることに注意してください。バッチ全体の平均遅延とこれらの二重マークパケットの平均遅延を比較すると、二重マーキング測定が実際に遅延傾向を表しているかどうかを理解できるため、有用な情報が得られます。

3.4. Delay Variation Measurement
3.4. 遅延変動測定

Similar to one-way delay measurement (both for Single Marking and Double Marking), the method can also be used to measure the inter-arrival jitter. We refer to the definition in RFC 3393 [RFC3393]. The alternation of colors, for a Single-Marking Method, can be used as a time reference to measure delay variations. In case of Double Marking, the time reference is given by the second-marked packets. Considering the example depicted in Figure 2, R1 stores the timestamp TS(A)R1 whenever it sends the first packet of a block, and R2 stores the timestamp TS(B)R2 whenever it receives the first packet of a block. The inter-arrival jitter can be easily derived from one-way delay measurement, by evaluating the delay variation of consecutive samples.

一方向遅延測定(シングルマーキングとダブルマーキングの両方)と同様に、この方法は到着間ジッターの測定にも使用できます。 RFC 3393 [RFC3393]の定義を参照します。シングルマーキング方式の場合、色の変化は、時間の基準として使用して遅延変動を測定できます。ダブルマーキングの場合、時間参照は2番目にマークされたパケットによって与えられます。図2に示す例を考えると、R1はブロックの最初のパケットを送信するたびにタイムスタンプTS(A)R1を保存し、R2はブロックの最初のパケットを受信するたびにタイムスタンプTS(B)R2を保存します。到着間ジッタは、連続するサンプルの遅延変動を評価することにより、一方向の遅延測定から簡単に導出できます。

The concept of mean delay can also be applied to delay variation, by evaluating the average variation of the interval between consecutive packets of the flow from R1 to R2.


4. Considerations
4. 考慮事項

This section highlights some considerations about the methodology.


4.1. Synchronization
4.1. 同期

The Alternate-Marking technique does not require a strong synchronization, especially for packet loss and two-way delay measurement. Only one-way delay measurement requires network devices to have synchronized clocks.


Color switching is the reference for all the network devices, and the only requirement to be achieved is that all network devices have to recognize the right batch along the path.


If the length of the measurement period is L time units, then all network devices must be synchronized to the same clock reference with an accuracy of +/- L/2 time units (without considering network delay). This level of accuracy guarantees that all network devices consistently match the color bit to the correct block. For example, if the color is toggled every second (L = 1 second), then clocks must be synchronized with an accuracy of +/- 0.5 second to a common time reference.

測定期間の長さがL時間単位の場合、すべてのネットワークデバイスは、+ /-L / 2時間単位の精度で(ネットワーク遅延を考慮せずに)同じクロック基準に同期する必要があります。このレベルの精度は、すべてのネットワークデバイスがカラービットを正しいブロックに常に一致させることを保証します。たとえば、色が1秒ごとに切り替わる場合(L = 1秒)、クロックは一般的な時間基準に対して+/- 0.5秒の精度で同期する必要があります。

This synchronization requirement can be satisfied even with a relatively inaccurate synchronization method. This is true for packet loss and two-way delay measurement, but not for one-way delay measurement, where clock synchronization must be accurate.


Therefore, a system that uses only packet loss and two-way delay measurement does not require synchronization. This is because the value of the clocks of network devices does not affect the computation of the two-way delay measurement.


4.2. Data Correlation
4.2. データ相関

Data correlation is the mechanism to compare counters and timestamps for packet loss, delay, and delay variation calculation. It could be performed in several ways depending on the Alternate-Marking application and use case. Some possibilities are to:


o use a centralized solution using NMS to correlate data; and

o NMSを使用した集中型ソリューションを使用してデータを相互に関連付けます。そして

o define a protocol-based distributed solution by introducing a new protocol or by extending the existing protocols (e.g., see RFC 6374 [RFC6374] or the Two-Way Active Measurement Protocol (TWAMP) as defined in RFC 5357 [RFC5357] or the One-Way Active Measurement Protocol (OWAMP) as defined in RFC 4656 [RFC4656]) in order to communicate the counters and timestamps between nodes.

o 新しいプロトコルを導入するか、既存のプロトコルを拡張して、プロトコルベースの分散ソリューションを定義します(たとえば、RFC 6374 [RFC6374]またはRFC 5357 [RFC5357]で定義されている双方向アクティブ測定プロトコル(TWAMP)を参照)。ノード間でカウンターとタイムスタンプを通信するために、RFC 4656 [RFC4656]で定義されているWay Active Measurement Protocol(OWAMP)。

In the following paragraphs, an example data correlation mechanism is explained and could be used independently of the adopted solutions.


When data is collected on the upstream and downstream nodes, e.g., packet counts for packet loss measurement or timestamps for packet delay measurement, and is periodically reported to or pulled by other nodes or an NMS, a certain data correlation mechanism SHOULD be in use to help the nodes or NMS tell whether any two or more packet counts are related to the same block of markers or if any two timestamps are related to the same marked packet.


The Alternate-Marking Method described in this document literally splits the packets of the measured flow into different measurement blocks; in addition, a Block Number (BN) could be assigned to each such measurement block. The BN is generated each time a node reads the data (packet counts or timestamps) and is associated with each packet count and timestamp reported to or pulled by other nodes or NMSs. The value of a BN could be calculated as the modulo of the local time (when the data are read) and the interval of the marking time period.

このドキュメントで説明する代替マーキング方法は、測定されたフローのパケットを文字通り、異なる測定ブロックに分割します。さらに、そのような各測定ブロックにブロック番号(BN)を割り当てることができます。 BNは、ノードがデータ(パケットカウントまたはタイムスタンプ)を読み取るたびに生成され、他のノードまたはNMSに報告またはプルされた各パケットカウントおよびタイムスタンプに関連付けられます。 BNの値は、ローカル時間(データが読み取られるとき)のモジュロおよびマーキング期間の間隔として計算できます。

When the nodes or NMS see, for example, the same BNs associated with two packet counts from an upstream and a downstream node, respectively, it considers that these two packet counts correspond to the same block, i.e., these two packet counts belong to the same block of markers from the upstream and downstream nodes. The assumption of this BN mechanism is that the measurement nodes are time synchronized. This requires the measurement nodes to have a certain time synchronization capability (e.g., the Network Time Protocol (NTP) [RFC5905] or the IEEE 1588 Precision Time Protocol (PTP) [IEEE-1588]). Synchronization aspects are further discussed in Section 4.1.

ノードまたはNMSが、たとえば、上流ノードと下流ノードからの2つのパケットカウントに関連付けられた同じBNをそれぞれ見た場合、これらの2つのパケットカウントは同じブロックに対応すると見なします。つまり、これらの2つのパケットカウントは上流ノードと下流ノードからのマーカーの同じブロック。このBNメカニズムの前提は、測定ノードが時間同期されていることです。これには、測定ノードに特定の時間同期機能が必要です(たとえば、ネットワークタイムプロトコル(NTP)[RFC5905]またはIEEE 1588プレシジョンタイムプロトコル(PTP)[IEEE-1588])。同期の側面については、セクション4.1で詳しく説明します。

4.3. Packet Reordering
4.3. パケットの並べ替え

Due to ECMP, packet reordering is very common in an IP network. The accuracy of a marking-based PM, especially packet loss measurement, may be affected by packet reordering. Take a look at the following example:


   Block   :    1    |    2    |    3    |    4    |    5    |...

Figure 5: Packet Reordering


In Figure 5, the packet stream for Node R1 isn't being reordered and can be safely assigned to interval blocks, but the packet stream for Node R2 is being reordered; so, looking at the packet with the marker of "B" in block 3, there is no safe way to tell whether the packet belongs to block 2 or block 4.


In general, there is the need to assign packets with the marker of "B" or "A" to the right interval blocks. Most of the packet reordering occurs at the edge of adjacent blocks, and they are easy to handle if the interval of each block is sufficiently large. Then, it can be assumed that the packets with different markers belong to the block that they are closer to. If the interval is small, it is difficult and sometimes impossible to determine to which block a packet belongs.


To choose a proper interval is important, and how to choose a proper interval is out of the scope of this document. But an implementation SHOULD provide a way to configure the interval and allow a certain degree of packet reordering.


5. Applications, Implementation, and Deployment
5. アプリケーション、実装、および展開

The methodology described in the previous sections can be applied in various situations. Basically, the Alternate-Marking technique could be used in many cases for performance measurement. The only requirement is to select and mark the flow to be monitored; in this way, packets are batched by the sender, and each batch is alternately marked such that it can be easily recognized by the receiver.


Some recent Alternate-Marking Method applications are listed below:


o IP Flow Performance Measurement (IPFPM): this application of the marking method is described in [COLORING]. As an example, in this document, the last reserved bit of the Flag field of the IPv4 header is proposed to be used for marking, while a solution for IPv6 could be to leverage the IPv6 extension header for marking.

o IPフローパフォーマンス測定(IPFPM):このマーキング方法のアプリケーションは、[COLORING]で説明されています。例として、このドキュメントでは、IPv4ヘッダーのフラグフィールドの最後の予約ビットをマーキングに使用することを提案していますが、IPv6の解決策はIPv6拡張ヘッダーをマーキングに活用することです。

o OAM Passive Performance Measurement: In [RFC8296], two OAM bits from the Bit Index Explicit Replication (BIER) header are reserved for the Passive performance measurement marking method. [PM-MM-BIER] details the measurement for multicast service over the BIER domain. In addition, the Alternate-Marking Method could also be used in a Service Function Chaining (SFC) domain. Lastly, the application of the marking method to Network Virtualization over Layer 3 (NVO3) protocols is considered by [NVO3-ENCAPS].

o OAMパッシブパフォーマンス測定:[RFC8296]では、ビットインデックス明示レプリケーション(BIER)ヘッダーからの2つのOAMビットは、パッシブパフォーマンス測定マーキングメソッド用に予約されています。 [PM-MM-BIER]は、BIERドメインを介したマルチキャストサービスの測定について詳しく説明しています。さらに、Alternate-Marking Methodは、Service Function Chaining(SFC)ドメインでも使用できます。最後に、マーキング手法をNetwork Virtualization over Layer 3(NVO3)プロトコルに適用することは、[NVO3-ENCAPS]によって検討されています。

o MPLS Performance Measurement: RFC 6374 [RFC6374] uses the Loss Measurement (LM) packet as the packet accounting demarcation point. Unfortunately, this gives rise to a number of problems that may lead to significant packet accounting errors in certain situations. [MPLS-FLOW] discusses the desired capabilities for

o MPLSパフォーマンス測定:RFC 6374 [RFC6374]は、パケットアカウンティング境界ポイントとして損失測定(LM)パケットを使用します。残念ながら、これはいくつかの問題を引き起こし、特定の状況では重大なパケットアカウンティングエラーにつながる可能性があります。 [MPLS-FLOW]は、

MPLS flow identification in order to perform a better in-band performance monitoring of user data packets. A method of accomplishing identification is Synonymous Flow Labels (SFLs) introduced in [SFL-FRAMEWORK], while [SYN-FLOW-LABELS] describes performance measurements in RFC 6374 with SFL.

MPLSフローの識別により、ユーザーデータパケットのインバンドパフォーマンス監視を改善します。識別を達成する方法は、[SFL-FRAMEWORK]で導入されたシノニムフローラベル(SFL)ですが、[SYN-FLOW-LABELS]は、SFLを使用したRFC 6374のパフォーマンス測定について説明しています。

o Active Performance Measurement: [ALT-MM-AMP] describes how to extend the existing Active Measurement Protocol, in order to implement the Alternate-Marking methodology. [ALT-MM-SLA] describes an extension to the Cisco SLA Protocol Measurement-Type UDP-Measurement.

o アクティブパフォーマンス測定:[ALT-MM-AMP]では、代替マーキング方法を実装するために、既存のアクティブ測定プロトコルを拡張する方法について説明しています。 [ALT-MM-SLA]は、Cisco SLAプロトコルMeasurement-Type UDP-Measurementの拡張機能を示しています。

An example of implementation and deployment is explained in the next section, just to clarify how the method can work.


5.1. Report on the Operational Experiment
5.1. 運用実験報告

The method described in this document, also called Packet Network Performance Monitoring (PNPM), has been invented and engineered in Telecom Italia.

このドキュメントで説明されている方法は、パケットネットワークパフォーマンスモニタリング(PNPM)とも呼ばれ、Telecom Italiaで発明および設計されています。

It is important to highlight that the general description of the methodology in this document is a consequence of the operational experiment. The fundamental elements of the technique have been tested, and the lessons learned from the operational experiment inspired the formalization of the Alternate-Marking Method as detailed in the previous sections.


The methodology has been used experimentally in Telecom Italia's network and is applied to multicast IPTV channels or other specific traffic flows with high QoS requirements (i.e., Mobile Backhauling traffic realized with a VPN MPLS).

この方法論はTelecom Italiaのネットワークで実験的に使用されており、マルチキャストIPTVチャネルまたはQoS要件の高いその他の特定のトラフィックフロー(つまり、VPN MPLSで実現されるモバイルバックホールトラフィック)に適用されます。

This technology has been employed by leveraging functions and tools available on IP routers, and it's currently being used to monitor packet loss in some portions of Telecom Italia's network. The application of this method for delay measurement has also been evaluated in Telecom Italia's labs.

このテクノロジーは、IPルーターで利用可能な機能とツールを活用して採用されており、現在、Telecom Italiaのネットワークの一部でパケット損失を監視するために使用されています。この方法の遅延測定への適用は、Telecom Italiaのラボでも評価されています。

This section describes how the experiment has been executed, particularly, how the features currently available on existing routing platforms can be used to apply the method, in order to give an example of implementation and deployment.


The operational test, described herein, uses the flow-based strategy, as defined in Section 3. Instead, the link-based strategy could be applied to a physical link or a logical link (e.g., an Ethernet VLAN or an MPLS Pseudowire (PW)).

ここで説明する運用テストでは、セクション3で定義されているフローベースの戦略を使用します。代わりに、リンクベースの戦略を物理リンクまたは論理リンク(たとえば、イーサネットVLANまたはMPLS疑似配線(PW ))。

The implementation of the method leverages the available router functions, since the experiment has been done by a Service Provider (as Telecom Italia is) on its own network. So, with current router implementations, only QoS-related fields and features offer the required flexibility to set bits in the packet header. In case a Service Provider only uses the three most-significant bits of the DSCP field (corresponding to IP Precedence) for QoS classification and queuing, it is possible to use the two least-significant bits of the DSCP field (bit 0 and bit 1) to implement the method without affecting QoS policies. That is the approach used for the experiment. One of the two bits (bit 0) could be used to identify flows subject to traffic monitoring (set to 1 if the flow is under monitoring, otherwise, it is set to 0), while the second (bit 1) can be used for coloring the traffic (switching between values 0 and 1, corresponding to colors A and B) and creating the blocks.

実験は独自のネットワーク上で(Telecom Italiaと同様に)サービスプロバイダーによって行われたため、このメソッドの実装は利用可能なルーター機能を活用します。したがって、現在のルーターの実装では、QoS関連のフィールドと機能だけが、パケットヘッダーにビットを設定するために必要な柔軟性を提供します。サービスプロバイダーがQoSの分類とキューイングにDSCPフィールドの3つの最上位ビット(IP Precedenceに対応)のみを使用する場合、DSCPフィールドの最下位2ビット(ビット0とビット1)を使用することが可能です。 )QoSポリシーに影響を与えずにメソッドを実装します。それが実験に使用されたアプローチです。 2つのビットの1つ(ビット0)はトラフィック監視の対象となるフローを識別するために使用でき(フローが監視中の場合は1に設定され、それ以外の場合は0に設定されます)、2番目のビット(ビット1)はトラフィックに色を付け(色AとBに対応する値0と1を切り替え)、ブロックを作成します。

The experiment considers a flow as all the packets sharing the same source IP address or the same destination IP address, depending on the direction. In practice, once the flow has been defined, traffic coloring using the DSCP field can be implemented by configuring an access-list on the router output interface. The access-list intercepts the flow(s) to be monitored and applies a policy to them that sets the DSCP field accordingly. Since traffic coloring has to be switched between the two values over time, the policy needs to be modified periodically. An automatic script is used to perform this task on the basis of a fixed timer. The automatic script is loaded on board of the router and automatizes the basic operations that are needed to realize the methodology.


After the traffic is colored using the DSCP field, all the routers on the path can perform the counting. For this purpose, an access-list that matches specific DSCP values can be used to count the packets of the flow(s) being monitored. The same access-list can be installed on all the routers of the path. In addition, network flow monitoring, such as provided by IPFIX [RFC7011], can be used to recognize timestamps of the first/last packet of a batch in order to enable one of the alternatives to measure the delay as detailed in Section 3.3.

DSCPフィールドを使用してトラフィックが色分けされると、パス上のすべてのルーターがカウントを実行できます。この目的のために、特定のDSCP値に一致するアクセスリストを使用して、監視されているフローのパケットをカウントできます。パスのすべてのルータに同じアクセスリストをインストールできます。さらに、IPFIX [RFC7011]によって提供されるようなネットワークフローモニタリングを使用して、セクション3.3で詳述するように、代替の1つが遅延を測定できるようにするために、バッチの最初/最後のパケットのタイムスタンプを認識することができます。

In Telecom Italia's experiment, the timer is set to 5 minutes, so the sequence of actions of the script is also executed every 5 minutes. This value has shown to be a good compromise between measurement frequency and stability of the measurement (i.e., the possibility of collecting all the measures referring to the same block).

Telecom Italiaの実験では、タイマーは5分に設定されているため、スクリプトの一連のアクションも5分ごとに実行されます。この値は、測定頻度と測定の安定性(つまり、同じブロックを参照するすべての測定値を収集する可能性)の間の適切な妥協点であることが示されています。

For this experiment, both counters and any other data are collected by using the automatic script that sends these out to an NMS. The NMS is responsible for packet loss calculation, performed by comparing the values of counters from the routers along the flow path(s). A 5-minute timer for color switching is a safe choice for reading the counters and is also coherent with the reporting window of the NMS.

この実験では、カウンターとその他のデータの両方が、これらをNMSに送信する自動スクリプトを使用して収集されます。 NMSは、フローパスに沿ったルーターからのカウンターの値を比較することによって実行されるパケット損失計算を担当します。色を切り替えるための5分のタイマーは、カウンターを読み取るための安全な選択であり、NMSのレポートウィンドウとも一致します。

Note that the use of the DSCP field for marking implies that the method in this case works reliably only within a single management and operation domain.


Lastly, the Telecom Italia experiment scales up to 1000 flows monitored together on a single router, while an implementation on dedicated hardware scales more, but it was tested only in labs for now.

最後に、Telecom Italiaの実験では、単一のルーターで一緒に監視される最大1000のフローをスケーリングしますが、専用ハードウェアへの実装ではさらにスケーリングしますが、現時点ではラボでのみテストしました。

5.1.1. Metric Transparency
5.1.1. メトリック透明度

Since a Service Provider application is described here, the method can be applied to end-to-end services supplied to customers. So it is important to highlight that the method MUST be transparent outside the Service Provider domain.


In Telecom Italia's implementation, the source node colors the packets with a policy that is modified periodically via an automatic script in order to alternate the DSCP field of the packets. The nodes between source and destination (included) have to use an access-list to count the colored packets that they receive and forward.

Telecom Italiaの実装では、送信元ノードは、パケットのDSCPフィールドを変更するために、自動スクリプトを介して定期的に変更されるポリシーでパケットに色を付けます。送信元と宛先(含まれている)の間のノードは、アクセスリストを使用して、受信して転送するカラーパケットをカウントする必要があります。

Moreover, the destination node has an important role: the colored packets are intercepted and a policy restores and sets the DSCP field of all the packets to the initial value. In this way, the metric is transparent because outside the section of the network under monitoring, the traffic flow is unchanged.


In such a case, thanks to this restoring technique, network elements outside the Alternate-Marking monitoring domain (e.g., the two Provider Edge nodes of the Mobile Backhauling VPN MPLS) are totally unaware that packets were marked. So this restoring technique makes Alternate Marking completely transparent outside its monitoring domain.

このような場合、この復元手法のおかげで、Alternate-Marking監視ドメイン外のネットワーク要素(たとえば、モバイルバックホールVPN MPLSの2つのプロバイダーエッジノード)は、パケットがマークされたことをまったく認識しません。したがって、この復元手法により、代替マーキングは監視ドメインの外部で完全に透過的になります。

6. Hybrid Measurement
6. ハイブリッド測定

The method has been explicitly designed for Passive measurements, but it can also be used with Active measurements. In order to have both end-to-end measurements and intermediate measurements (Hybrid measurements), two endpoints can exchange artificial traffic flows and apply Alternate Marking over these flows. In the intermediate points, artificial traffic is managed in the same way as real traffic and measured as specified before. So the application of the marking method can also simplify the Active measurement, as explained in [ALT-MM-AMP].


7. Compliance with Guidelines from RFC 6390
7. RFC 6390のガイドラインへの準拠

RFC 6390 [RFC6390] defines a framework and a process for developing Performance Metrics for protocols above and below the IP layer (such as IP-based applications that operate over reliable or datagram transport protocols).

RFC 6390 [RFC6390]は、IP層の上下のプロトコル(信頼性の高いプロトコルやデータグラムトランスポートプロトコルで動作するIPベースのアプリケーションなど)のパフォーマンスメトリックを開発するためのフレームワークとプロセスを定義しています。

This document doesn't aim to propose a new Performance Metric but rather a new Method of Measurement for a few Performance Metrics that have already been standardized. Nevertheless, it's worth applying guidelines from [RFC6390] to the present document, in order to provide a more complete and coherent description of the proposed method. We used a combination of the Performance Metric Definition template defined in Section 5.4 of [RFC6390] and the Dependencies laid out in Section 5.5 of that document.

このドキュメントは、新しいパフォーマンスメトリックを提案することを目的とせず、すでに標準化されているいくつかのパフォーマンスメトリックの新しい測定方法を提案します。それにもかかわらず、提案された方法のより完全で首尾一貫した説明を提供するために、[RFC6390]から現在の文書にガイドラインを適用することは価値があります。 [RFC6390]のセクション5.4で定義されたパフォーマンスメトリック定義テンプレートと、そのドキュメントのセクション5.5に配置された依存関係の組み合わせを使用しました。

o Metric Name / Metric Description: as already stated, this document doesn't propose any new Performance Metrics. On the contrary, it describes a novel method for measuring packet loss [RFC7680]. The same concept, with small differences, can also be used to measure delay [RFC7679] and jitter [RFC3393]. The document mainly describes the applicability to packet loss measurement.

o メトリック名/メトリックの説明:すでに述べたように、このドキュメントは新しいパフォーマンスメトリックを提案していません。それどころか、それはパケット損失を測定するための新しい方法を記述します[RFC7680]。わずかな違いはあるものの、同じ概念を使用して、遅延[RFC7679]とジッタ[RFC3393]を測定することもできます。このドキュメントでは、主にパケット損失測定への適用性について説明しています。

o Method of Measurement or Calculation: according to the method described in the previous sections, the number of packets lost is calculated by subtracting the value of the counter on the source node from the value of the counter on the destination node. Both counters must refer to the same color. The calculation is performed when the value of the counters is in a steady state. The steady state is an intrinsic characteristic of the marking method counters because the alternation of color makes the counters associated with each color still one at a time for the duration of a marking period.

o 測定または計算の方法:前のセクションで説明した方法に従って、宛先ノードのカウンターの値から送信元ノードのカウンターの値を減算することにより、失われたパケット数が計算されます。両方のカウンターは同じ色を参照する必要があります。カウンタの値が定常状態のときに計算が実行されます。定常状態は、マーキング方法カウンターの固有の特性です。これは、色が変わると、マーキング期間中、各色に関連付けられたカウンターが一度に1つずつ残るためです。

o Units of Measurement: the method calculates and reports the exact number of packets sent by the source node and not received by the destination node.

o 測定単位:このメソッドは、送信元ノードによって送信され、宛先ノードによって受信されなかった正確なパケット数を計算して報告します。

o Measurement Point(s) with Potential Measurement Domain: the measurement can be performed between adjacent nodes, on a per-link basis, or along a multi-hop path, provided that the traffic under measurement follows that path. In case of a multi-hop path, the measurements can be performed both end-to-end and hop-by-hop.

o 潜在的な測定ドメインを持つ測定ポイント:測定は、隣接するノード間で、リンクごとに、またはマルチホップパスに沿って実行できます。マルチホップパスの場合、測定はエンドツーエンドとホップバイホップの両方で実行できます。

o Measurement Timing: the method has a constraint on the frequency of measurements. This is detailed in Section 3.2, where it is specified that the marking period and the guard band interval are strictly related each other to avoid out-of-order issues. That is because, in order to perform a measurement, the counter must be in a steady state, and this happens when the traffic is being colored with the alternate color. As an example, in the experiment of the method, the time interval is set to 5 minutes, while other optimized implementations can also use a marking period of a few seconds.

o 測定タイミング:この方法には、測定の頻度に制約があります。これはセクション3.2で詳しく説明されています。ここでは、順序付けの問題を回避するために、マーキング期間とガードバンド間隔が互いに厳密に関連していることが指定されています。これは、測定を実行するために、カウンタが定常状態である必要があるためです。これは、トラフィックが代替色で着色されているときに発生します。例として、メソッドの実験では、時間間隔は5分に設定されていますが、他の最適化された実装でも数秒のマーキング期間を使用できます。

o Implementation: the experiment of the method uses two encodings of the DSCP field to color the packets; this enables the use of policy configurations on the router to color the packets and accordingly configure the counter for each color. The path followed by traffic being measured should be known in advance in order to configure the counters along the path and be able to compare the correct values.

o 実装:メソッドの実験では、DSCPフィールドの2つのエンコーディングを使用してパケットに色を付けます。これにより、ルーターでポリシー設定を使用してパケットに色を付け、それに応じて各色のカウンターを設定できます。パスに沿ってカウンターを構成し、正しい値を比較できるようにするには、測定対象のトラフィックがたどるパスをあらかじめ知っておく必要があります。

o Verification: both in the lab and in the operational network, the methodology has been tested and experimented for packet loss and delay measurements by using traffic generators together with precision test instruments and network emulators.

o 検証:ラボと運用ネットワークの両方で、トラフィックジェネレーターと高精度テスト機器およびネットワークエミュレーターを使用して、パケット損失と遅延測定の方法をテストおよび実験しました。

o Use and Applications: the method can be used to measure packet loss with high precision on live traffic; moreover, by combining end-to-end and per-link measurements, the method is useful to pinpoint the single link that is experiencing loss events.

o 用途とアプリケーション:この方法は、ライブトラフィックのパケット損失を高精度で測定するために使用できます。さらに、エンドツーエンドおよびリンクごとの測定を組み合わせることにより、この方法は、損失イベントが発生している単一のリンクを特定するのに役立ちます。

o Reporting Model: the value of the counters has to be sent to a centralized management system that performs the calculations; such samples must contain a reference to the time interval they refer to, so that the management system can perform the correct correlation; the samples have to be sent while the corresponding counter is in a steady state (within a time interval); otherwise, the value of the sample should be stored locally.

o レポートモデル:カウンターの値は、計算を実行する集中管理システムに送信する必要があります。そのようなサンプルには、管理システムが正しい相関を実行できるように、それらが参照する時間間隔への参照が含まれている必要があります。対応するカウンターが定常状態にある間(時間間隔内)にサンプルを送信する必要があります。それ以外の場合、サンプルの値はローカルに保存する必要があります。

o Dependencies: the values of the counters have to be correlated to the time interval they refer to; moreover, because the experiment of the method is based on DSCP values, there are significant dependencies on the usage of the DSCP field: it must be possible to rely on unused DSCP values without affecting QoS-related configuration and behavior; moreover, the intermediate nodes must not change the value of the DSCP field not to alter the measurement.

o 依存関係:カウンターの値は、それらが参照する時間間隔と相関している必要があります。さらに、メソッドの実験はDSCP値に基づいているため、DSCPフィールドの使用には大きな依存関係があります。QoS関連の構成と動作に影響を与えずに、未使用のDSCP値に依存できる必要があります。さらに、中間ノードは、DSCPフィールドの値を変更して、測定値を変更しないようにする必要があります。

o Organization of Results: the Method of Measurement produces singletons.

o 結果の構成:測定方法はシングルトンを生成します。

o Parameters: currently, the main parameter of the method is the time interval used to alternate the colors and read the counters.

o パラメータ:現在、メソッドの主なパラメータは、色を変更してカウンタを読み取るために使用される時間間隔です。

8. IANA Considerations
8. IANAに関する考慮事項

This document has no IANA actions.


9. Security Considerations
9. セキュリティに関する考慮事項

This document specifies a method to perform measurements in the context of a Service Provider's network and has not been developed to conduct Internet measurements, so it does not directly affect Internet security nor applications that run on the Internet. However, implementation of this method must be mindful of security and privacy concerns.


There are two types of security concerns: potential harm caused by the measurements and potential harm to the measurements.


o Harm caused by the measurement: the measurements described in this document are Passive, so there are no new packets injected into the network causing potential harm to the network itself and to data traffic. Nevertheless, the method implies modifications on the fly to a header or encapsulation of the data packets: this must be performed in a way that doesn't alter the quality of service experienced by packets subject to measurements and that preserves stability and performance of routers doing the measurements. One of the main security threats in OAM protocols is network reconnaissance; an attacker can gather information about the network performance by passively eavesdropping on OAM messages. The advantage of the methods described in this document is that the marking bits are the only information that is exchanged between the network devices. Therefore, Passive eavesdropping on data-plane traffic does not allow attackers to gain information about the network performance.

o 測定による害:このドキュメントで説明する測定はパッシブであるため、ネットワークに注入された新しいパケットがネットワーク自体やデータトラフィックに潜在的な害を及ぼすことはありません。それにもかかわらず、この方法は、データパケットのヘッダーまたはカプセル化へのオンザフライでの変更を意味します。これは、測定の対象となるパケットが経験するサービス品質を変更せず、ルーターの安定性とパフォーマンスを維持する方法で実行する必要があります。測定。 OAMプロトコルの主要なセキュリティ脅威の1つは、ネットワークの偵察です。攻撃者は、OAMメッセージを受動的に盗聴することにより、ネットワークパフォーマンスに関する情報を収集できます。このドキュメントで説明されている方法の利点は、マーキングビットがネットワークデバイス間で交換される唯一の情報であることです。したがって、データプレーントラフィックのパッシブ盗聴では、攻撃者はネットワークパフォーマンスに関する情報を入手できません。

o Harm to the Measurement: the measurements could be harmed by routers altering the marking of the packets or by an attacker injecting artificial traffic. Authentication techniques, such as digital signatures, may be used where appropriate to guard against injected traffic attacks. Since the measurement itself may be affected by routers (or other network devices) along the path of IP packets intentionally altering the value of marking bits of packets, as mentioned above, the mechanism specified in this document can be applied just in the context of a controlled domain; thus, the routers (or other network devices) are locally administered and this type of attack can be avoided. In addition, an attacker can't gain information about network performance from a single monitoring point; it must use synchronized monitoring points at multiple points on the path, because they have to do the same kind of measurement and aggregation that Service Providers using Alternate Marking must do.


The privacy concerns of network measurement are limited because the method only relies on information contained in the header or encapsulation without any release of user data. Although information in the header or encapsulation is metadata that can be used to compromise the privacy of users, the limited marking technique in this document seems unlikely to substantially increase the existing privacy risks from header or encapsulation metadata. It might be theoretically possible to modulate the marking to serve as a covert channel, but it would have a very low data rate if it is to avoid adversely affecting the measurement systems that monitor the marking.


Delay attacks are another potential threat in the context of this document. Delay measurement is performed using a specific packet in each block, marked by a dedicated color bit. Therefore, a man-in-the-middle attacker can selectively induce synthetic delay only to delay-colored packets, causing systematic error in the delay measurements. As discussed in previous sections, the methods described in this document rely on an underlying time synchronization protocol. Thus, by attacking the time protocol, an attacker can potentially compromise the integrity of the measurement. A detailed discussion about the threats against time protocols and how to mitigate them is presented in RFC 7384 [RFC7384].

遅延攻撃は、このドキュメントのコンテキストでは別の潜在的な脅威です。遅延測定は、専用のカラービットでマークされた各ブロックの特定のパケットを使用して実行されます。したがって、介在者の攻撃者は、遅延カラーのパケットにのみ合成遅延を選択的に誘導し、遅延測定に系統的エラーを引き起こす可能性があります。前のセクションで説明したように、このドキュメントで説明する方法は、基礎となる時刻同期プロトコルに依存しています。したがって、時間プロトコルを攻撃することにより、攻撃者は測定の整合性を危険にさらす可能性があります。時間プロトコルに対する脅威とそれらを軽減する方法についての詳細な議論は、RFC 7384 [RFC7384]に提示されています。

10. References
10. 参考文献
10.1. Normative References
10.1. 引用文献

[IEEE-1588] IEEE, "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", IEEE Std 1588-2008.

[IEEE-1588] IEEE、「ネットワーク化された測定および制御システム用の高精度クロック同期プロトコルのIEEE標準」、IEEE Std 1588-2008。

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <>.

[RFC2119] Bradner、S。、「要件レベルを示すためにRFCで使用するキーワード」、BCP 14、RFC 2119、DOI 10.17487 / RFC2119、1997年3月、< rfc2119>。

[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393, November 2002, <>.

[RFC3393] Demichelis、C。およびP. Chimento、「IPパフォーマンスメトリックのIPパケット遅延変動メトリック(IPPM)」、RFC 3393、DOI 10.17487 / RFC3393、2002年11月、< / info / rfc3393>。

[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, <>.

[RFC5905] Mills、D.、Martin、J.、Ed。、Burbank、J。、およびW. Kasch、「Network Time Protocol Version 4:Protocol and Algorithms Specification」、RFC 5905、DOI 10.17487 / RFC5905、2010年6月、 <>。

[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January 2016, <>.

[RFC7679] Almes、G.、Kalidindi、S.、Zekauskas、M。、およびA. Morton、編、「IPパフォーマンスメトリック(IPPM)の片方向遅延メトリック」、STD 81、RFC 7679、DOI 10.17487 / RFC7679、2016年1月、<>。

[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Loss Metric for IP Performance Metrics (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 2016, <>.

[RFC7680] Almes、G.、Kalidindi、S.、Zekauskas、M。、およびA. Morton、編、「IP Performance Metrics(IPPM)の一方向損失メトリック」、STD 82、RFC 7680、DOI 10.17487 / RFC7680、2016年1月、<>。

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <>.

[RFC8174] Leiba、B。、「RFC 2119キーワードの大文字と小文字のあいまいさ」、BCP 14、RFC 8174、DOI 10.17487 / RFC8174、2017年5月、< rfc8174>。

10.2. Informative References
10.2. 参考引用

[ALT-MM-AMP] Fioccola, G., Clemm, A., Bryant, S., Cociglio, M., Chandramouli, M., and A. Capello, "Alternate Marking Extension to Active Measurement Protocol", Work in Progress, draft-fioccola-ippm-alt-mark-active-01, March 2017.

[ALT-MM-AMP] Fioccola、G.、Clemm、A.、Bryant、S.、Cociglio、M.、Chandramouli、M.、A。Capello、「Active Measurement Protocolの代替マーキング拡張機能」、作業中、draft-fioccola-ippm-alt-mark-active-01、2017年3月。

[ALT-MM-SLA] Fioccola, G., Clemm, A., Cociglio, M., Chandramouli, M., and A. Capello, "Alternate Marking Extension to Cisco SLA Protocol RFC6812", Work in Progress, draft-fioccola-ippm-rfc6812-alt-mark-ext-01, March 2016.

[ALT-MM-SLA] Fioccola、G.、Clemm、A.、Cociglio、M.、Chandramouli、M。、およびA. Capello、「Cisco SLA Protocol RFC6812の代替マーキング拡張機能」、Work in Progress、draft-fioccola -ippm-rfc6812-alt-mark-ext-01、2016年3月。

[COLORING] Chen, M., Zheng, L., Mirsky, G., Fioccola, G., and T. Mizrahi, "IP Flow Performance Measurement Framework", Work in Progress, draft-chen-ippm-coloring-based-ipfpm-framework-06, March 2016.

[COLORING] Chen、M.、Zheng、L.、Mirsky、G.、Fioccola、G。、およびT. Mizrahi、「IPフローパフォーマンス測定フレームワーク」、Work in Progress、draft-chen-ippm-coloring-based- ipfpm-framework-06、2016年3月。

[IP-FLOW-REPORT] Chen, M., Zheng, L., and G. Mirsky, "IP Flow Performance Measurement Report", Work in Progress, draft-chen-ippm-ipfpm-report-01, April 2016.

[IP-FLOW-REPORT] Chen、M.、Zheng、L。、およびG. Mirsky、「IP Flow Performance Measurement Report」、Work in Progress、draft-chen-ippm-ipfpm-report-01、2016年4月。

[IP-MULTICAST-PM] Cociglio, M., Capello, A., Bonda, A., and L. Castaldelli, "A method for IP multicast performance monitoring", Work in Progress, draft-cociglio-mboned-multicast-pm-01, October 2010.

[IP-MULTICAST-PM] Cociglio、M.、Capello、A.、Bonda、A。、およびL. Castaldelli、「IPマルチキャストパフォーマンスモニタリングの方法」、作業中、draft-cociglio-mboned-multicast-pm 2010年10月1日。

[MPLS-FLOW] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G. Mirsky, "MPLS Flow Identification Considerations", Work in Progress, draft-ietf-mpls-flow-ident-06, December 2017.

[MPLS-FLOW]ブライアント、S。、ピグナタロ、C。、チェン、M。、リー、Z。、およびG.ミルスキー、「MPLSフロー識別の考慮事項」、作業中、draft-ietf-mpls-flow-ident -06、2017年12月。

[MULTIPOINT-ALT-MM] Fioccola, G., Cociglio, M., Sapio, A., and R. Sisto, "Multipoint Alternate Marking method for passive and hybrid performance monitoring", Work in Progress, draft-fioccola-ippm-multipoint-alt-mark-01, October 2017.

[MULTIPOINT-ALT-MM] Fioccola、G.、Cociglio、M.、Sapio、A。、およびR. Sisto、「パッシブおよびハイブリッドパフォーマンスモニタリングのためのマルチポイント代替マーキング方法」、進行中の作業、draft-fioccola-ippm- multipoint-alt-mark-01、2017年10月。

[NVO3-ENCAPS] Boutros, S., Ganga, I., Garg, P., Manur, R., Mizrahi, T., Mozes, D., Nordmark, E., Smith, M., Aldrin, S., and I. Bagdonas, "NVO3 Encapsulation Considerations", Work in Progress, draft-ietf-nvo3-encap-01, October 2017.

[NVO3-ENCAPS] Boutros、S.、Ganga、I.、Garg、P.、Manur、R.、Mizrahi、T.、Mozes、D.、Nordmark、E.、Smith、M.、Aldrin、S.、 I. Bagdonas、「NVO3カプセル化に関する考慮事項」、Work in Progress、draft-ietf-nvo3-encap-01、2017年10月。

[OPSAWG-P3M] Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda, "A packet based method for passive performance monitoring", Work in Progress, draft-tempia-opsawg-p3m-04, February 2014.

[OPSAWG-P3M] Capello、A.、Cociglio、M.、Castaldelli、L。、およびA. Bonda、「パッシブパフォーマンスモニタリングのためのパケットベースの方法」、Work in Progress、draft-tempia-opsawg-p3m-04、 2014年2月。

[PM-MM-BIER] Mirsky, G., Zheng, L., Chen, M., and G. Fioccola, "Performance Measurement (PM) with Marking Method in Bit Index Explicit Replication (BIER) Layer", Work in Progress, draft-ietf-bier-pmmm-oam-03, October 2017.

[PM-MM-BIER] Mirsky、G.、Zheng、L.、Chen、M。、およびG. Fioccola、「ビットインデックスの明示的なレプリケーション(BIER)レイヤーでのマーキング方法を使用したパフォーマンス測定(PM)」、作業中、draft-ietf-bier-pmmm-oam-03、2017年10月。

[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006, <>.

[RFC4656] Shalunov、S.、Teitelbaum、B.、Karp、A.、Boote、J。、およびM. Zekauskas、「A One-way Active Measurement Protocol(OWAMP)」、RFC 4656、DOI 10.17487 / RFC4656、9月2006、<>。

[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, <>.

[RFC5357] Hedayat、K.、Krzanowski、R.、Morton、A.、Yum、K。、およびJ. Babiarz、「A Two-Way Active Measurement Protocol(TWAMP)」、RFC 5357、DOI 10.17487 / RFC5357、10月2008、<>。

[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009, <>.

[RFC5481] Morton、A。およびB. Claise、「Packet Delay Variation Applicability Statement」、RFC 5481、DOI 10.17487 / RFC5481、2009年3月、<>。

[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, DOI 10.17487/RFC6374, September 2011, <>.

[RFC6374] Frost、D。およびS. Bryant、「MPLSネットワークのパケット損失と遅延測定」、RFC 6374、DOI 10.17487 / RFC6374、2011年9月、< >。

[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New Performance Metric Development", BCP 170, RFC 6390, DOI 10.17487/RFC6390, October 2011, <>.

[RFC6390]クラークA.およびB.クレイズ、「新しいパフォーマンスメトリック開発を検討するためのガイドライン」、BCP 170、RFC 6390、DOI 10.17487 / RFC6390、2011年10月、< / rfc6390>。

[RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting IP Network Performance Metrics: Different Points of View", RFC 6703, DOI 10.17487/RFC6703, August 2012, <>.

[RFC6703] Morton、A.、Ramachandran、G。、およびG. Maguluri、「Reporting IP Network Performance Metrics:Different Points of View」、RFC 6703、DOI 10.17487 / RFC6703、2012年8月、<https://www.rfc>。

[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013, <>.

[RFC7011] Claise、B。、編、Trammell、B。、編、およびP. Aitken、「フロー情報の交換のためのIPフロー情報エクスポート(IPFIX)プロトコルの仕様」、STD 77、RFC 7011、 DOI 10.17487 / RFC7011、2013年9月、<>。

[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. Weingarten, "An Overview of Operations, Administration, and Maintenance (OAM) Tools", RFC 7276, DOI 10.17487/RFC7276, June 2014, <>.

[RFC7276]ミズラヒ、T。、スプレッチャー、N。、ベラガンバ、E。、およびY.ウェインガルテン、「運用、管理、および保守(OAM)ツールの概要」、RFC 7276、DOI 10.17487 / RFC7276、2014年6月、 <>。

[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, October 2014, <>.

[RFC7384]ミズラヒ、T。、「パケット交換ネットワークにおけるタイムプロトコルのセキュリティ要件」、RFC 7384、DOI 10.17487 / RFC7384、2014年10月、<>。

[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, May 2016, <>.

[RFC7799]モートン、A。、「アクティブおよびパッシブメトリックおよびメソッド(中間のハイブリッドタイプを使用)」、RFC 7799、DOI 10.17487 / RFC7799、2016年5月、< / rfc7799>。

[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non-MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 2018, <>.

[RFC8296] Wijnands、IJ。、Ed。、Rosen、E.、Ed。、Dolganow、A.、Tantsura、J.、Aldrin、S.、and I. Meil​​ik、 "Encapsulation for Bit Index Explicit Replication(BIER)in MPLS and Non-MPLS Networks」、RFC 8296、DOI 10.17487 / RFC8296、2018年1月、<>。

[SFL-FRAMEWORK] Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., and G. Mirsky, "Synonymous Flow Label Framework", Work in Progress, draft-ietf-mpls-sfl-framework-00, August 2017.

[SFL-FRAMEWORK]ブライアント、S。、チェン、M。、リー、Z。、スワロー、G。、シババラン、S。、およびG.ミルスキー、「Synonymous Flow Label Framework」、Work in Progress、draft-ietf- mpls-sfl-framework-00、2017年8月。

[SYN-FLOW-LABELS] Bryant, S., Chen, M., Li, Z., Swallow, G., Sivabalan, S., Mirsky, G., and G. Fioccola, "RFC6374 Synonymous Flow Labels", Work in Progress, draft-ietf-mpls-rfc6374-sfl-01, December 2017.




The previous IETF specifications describing this technique were: [IP-MULTICAST-PM] and [OPSAWG-P3M].


The authors would like to thank Alberto Tempia Bonda, Domenico Laforgia, Daniele Accetta, and Mario Bianchetti for their contribution to the definition and the implementation of the method.


The authors would also thank Spencer Dawkins, Carlos Pignataro, Brian Haberman, and Eric Vyncke for their assistance and their detailed and precious reviews.


Authors' Addresses


Giuseppe Fioccola (editor) Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy

Giuseppe Fioccola(編集者)Telecom Italia Via Reiss Romoli、274トリノ10148イタリア


Alessandro Capello Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy

アレッサンドロカペッロテレコムイタリアVia Reiss Romoli、274トリノ10148イタリア


Mauro Cociglio Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy

Mauro Cociglio TelecomイタリアVia Reiss Romoli、274トリノ10148イタリア

Email: Luca Castaldelli Telecom Italia Via Reiss Romoli, 274 Torino 10148 Italy

メール Luca Castaldelli Telecom Italia Via Reiss Romoli、274 Torino 10148 Italy


Mach(Guoyi) Chen Huawei Technologies

Mach(GU O一)Chen hu Aはテクノロジー


Lianshu Zheng Huawei Technologies

lイアン番号Zは非常にGH UAはテクノロジー


Greg Mirsky ZTE United States of America



Tal Mizrahi Marvell 6 Hamada St. Yokneam Israel

Tal Mizrahi Marvell 6 Hamada St. Yokneamイスラエル