Internet-Draft enhanced-alternate-marking November 2023
Zhou, et al. Expires 27 May 2024 [Page]
Intended Status:
Standards Track
T. Zhou, Ed.
G. Fioccola
Y. Liu
China Mobile
M. Cociglio
Telecom Italia
R. Pang
China Unicom
L. Xiong
S. Lee
W. Li

Enhanced Alternate Marking Method


This document extends the IPv6 Alternate Marking Option to provide enhanced capabilities and allow advanced functionalities. With this extension, it can be possible to perform thicker packet loss measurements and more dense delay measurements with no limitation for the number of concurrent flows under monitoring.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at

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This Internet-Draft will expire on 27 May 2024.

1. Introduction

The Alternate Marking [RFC9341] and Multipoint Alternate Marking [RFC9342] define the Alternate Marking technique that is a hybrid performance measurement method, per [RFC7799] classification of measurement methods. This method is based on marking consecutive batches of packets and it can be used to measure packet loss, latency, and jitter on live traffic.

The IPv6 AltMark Option [RFC9343] applies the Alternate Marking Method to IPv6, and defines an Extension Header Option to encode the Alternate Marking Method for both the Hop-by-Hop Options Header and the Destination Options Header.

While the IPv6 AltMark Option implements the basic alternate marking methodology, this document defines extended data fields for the AltMark Option and provides enhanced capabilities to overcome some challenges and enable future proof applications.

It is worth mentioning that the enhanced capabilities are intended for further use and are optional.

Some possible enhanced applications MAY be:

  1. thicker packet loss measurements: the single marking method of the base AltMark Option can be extended with additional marking bits in order to get shortest marking periods under the same timing conditions.

  2. more dense delay measurements: than double marking method of the base AltMark Option can be extended with additional marking bits in order to identify down to each packet as delay sample.

  3. increase the number of concurrent flows under monitoring: if the 20-bit FlowMonID is set independently and pseudo randomly, there is a 50% chance of collision for 1206 flows. The size of FlowMonIDcan can be extended to raise the entropy and therefore to increase the number of concurrent flows that can be monitored.

1.1. Requirements Language

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. Data Fields Format

The Data Fields format is represented in Figure 1. A 5-bit NH(NextHeader) field is allocated from the Reserved field of IPv6 AltMark Option [RFC9343]. It is worth highlighting that remaining bits of the former Reserved field continue to be reserved.

 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
|           FlowMonID                   |L|D| Reserved|    NH   |

Figure 1: Data fields indicator for enhanced capabilities

The NH (NextHeader) field is used to indicate the extended data fields which are used for enhanced capabilities:

  • NextHeader value of 0 is reserved for backward compatibility. It means that there is no extended data field attached.

  • NextHeader values of 1-15 are reserved for private use or for experimentation.

  • NextHeader value of 16-31 indicates the extended data fields that should be defined in IETF. This document specifies the extended data fields when the NextHeader is 16. The format is shown in Figure 2.

 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
|           FlowMonID Ext               |F|  P  | M |  Reserved |
|           MetaInfo            |            Padding            |
Figure 2: Data fields extension for enhanced alternate marking


  • FlowMonID Ext - 20 bits unsigned integer. This is used to extend the FlowMonID in order to reduce the conflict when random allocation is applied. The disambiguation of the FlowMonID field is discussed in IPv6 AltMark Option [RFC9343].

  • F - The flag to enable the automatic backward flow monitoring. If F=1, it indicates the egress node to setup the backward flow monitoring automatically based on 5 tuple of the forward flow.

  • P - It indicates period of the alternate marking.

    • 000: 1s

    • 001: 10s

    • 010: 30s

    • 011: 60s

    • 100: 300s

    M - It indicates the measurement mode.

    • 00: Reserved;

    • 01: Edge to edge mode;

    • 10: Hop by hop mode;

    • 11: Reserved.

  • MetaInfo - A 16-bit Bitmap to indicate more meta data attached for the enhanced function (see below).

  • Padding - These bits MUST be set to zero when not being used.

The MetaInfo is defined in the following Figure 4 as a bit map:

bit 0: If set to 1, it indicates a 6 bytes Timestamp that is attached after the MetaInfo. Timestamp(s) stands for the number of seconds in the timestamp. It will overwrite the Padding after MetaInfo. Timestamp(ns) stands for the number of sub-seconds in the timestamp with the unit of nano second. This Timestamp is filled by the encapsulation node, and is taken all the way to the decapsulation node. So that all the intermediate nodes could compare it with its local time, and measure the one way delay.

 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
                                |    Timestamp(s)               |
|                 Timestamp(ns)                                 |
Figure 3: Timestamp data field

bit 1: If set to 1, it indicates more detailed control information with the following data format that is attached after the MetaInfo:

 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
|  DIP Mask     |  SIP Mask     |P|I|O|V|S|T|    Period         |
Figure 4: Control information data field

This is used to set up the backward direction flow monitoring. Where:

  • DIP Mask: The length of the destination IP prefix used to match the flow.

  • SIP Mask: The length of the source IP prefix used to match the flow.

  • P bit: If set to 1, it indicates to match the flow using the protocol identifier in the trigger packet.

  • I bit: If set to 1, it indicates to match the source port.

  • O bit: If set to 1, it indicates to match the destination port.

  • V bit: If set to 1, the egress node will automatically set up reverse direction monitoring, and allocate a FlowMonID.

  • S bit: If set to 1, it indicates to match the DSCP.

  • T bit: Used to control the scope of tunnel measurement. T=1 means meausre between Network-to-Network Interfaces (i.e., NNI to NNI). T=0 means measure between User-to-Network Interfaces (i.e., UNI to UNI).

  • Period: it indicates the alternate marking period with the unit of second.

bit 2: If set to 1, it indicates a 4 bytes Sequence number with the following data format that is attached after the MetaInfo. The unique Sequence could be used to detect the out-of-order packets, in addition to the normal loss measurement. More over, the Sequence can be used together with the latency measurement, so as to get the per packet timestamp.

 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                             |
Figure 5: Sequence number data field

It is worth noting that the meta data information forming the Padding and specified above in Figure 3, Figure 4 and Figure 5 must be ordered according to the order of the MetaInfo bits.

3. Security Considerations

IPv6 AltMark Option [RFC9343] analyzes different security concerns and related solutions. These aspects are valid and applicable also to this document. In particular the fundamental security requirement is that Alternate Marking MUST only be applied in a specific limited domain, as also mentioned in [RFC8799].

4. IANA Considerations

This document has no request to IANA.

5. Acknowledgements

The authors would like to thank Adrian Farrel for the comments and review of this document.

6. References

6.1. Normative References

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T., and T. Zhou, "Alternate-Marking Method", RFC 9341, DOI 10.17487/RFC9341, , <>.
Fioccola, G., Ed., Cociglio, M., Sapio, A., Sisto, R., and T. Zhou, "Clustered Alternate-Marking Method", RFC 9342, DOI 10.17487/RFC9342, , <>.
Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R. Pang, "IPv6 Application of the Alternate-Marking Method", RFC 9343, DOI 10.17487/RFC9343, , <>.

6.2. Informative References

Morton, A., "Active and Passive Metrics and Methods (with Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, , <>.
Carpenter, B. and B. Liu, "Limited Domains and Internet Protocols", RFC 8799, DOI 10.17487/RFC8799, , <>.

Authors' Addresses

Tianran Zhou (editor)
156 Beiqing Rd.
Giuseppe Fioccola
Riesstrasse, 25
80992 Munich
Yisong Liu
China Mobile
Mauro Cociglio
Telecom Italia
Ran Pang
China Unicom
9 Shouti South Rd.
Lixia Xiong
Shinyoung Lee
71, Magokjungang 8-ro, Gangseo-gu
Republic of Korea
Weidong Li
156 Beiqing Rd.