6MAN Working Group                                           G. Fioccola
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: December 2, 2021                                    M. Cociglio
                                                          Telecom Italia
                                                                  F. Qin
                                                            China Mobile
                                                                 R. Pang
                                                            China Unicom
                                                            May 31, 2021

            IPv6 Application of the Alternate Marking Method


   This document describes how the Alternate Marking Method can be used
   as a passive performance measurement tool in an IPv6 domain.  It
   defines a new Extension Header Option to encode alternate marking
   information in both the Hop-by-Hop Options Header and Destination
   Options Header.

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 https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 2, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of

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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Alternate Marking application to IPv6 . . . . . . . . . . . .   3
     2.1.  Controlled Domain . . . . . . . . . . . . . . . . . . . .   4
   3.  Definition of the AltMark Option  . . . . . . . . . . . . . .   5
     3.1.  Data Fields Format  . . . . . . . . . . . . . . . . . . .   5
   4.  Use of the AltMark Option . . . . . . . . . . . . . . . . . .   6
   5.  Alternate Marking Method Operation  . . . . . . . . . . . . .   8
     5.1.  Packet Loss Measurement . . . . . . . . . . . . . . . . .   8
     5.2.  Packet Delay Measurement  . . . . . . . . . . . . . . . .   9
     5.3.  Flow Monitoring Identification  . . . . . . . . . . . . .  10
       5.3.1.  Uniqueness of FlowMonID . . . . . . . . . . . . . . .  11
     5.4.  Multipoint and Clustered Alternate Marking  . . . . . . .  12
     5.5.  Data Collection and Calculation . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   [RFC8321] and [RFC8889] describe a passive performance measurement
   method, which can be used to measure packet loss, latency and jitter
   on live traffic.  Since this method is based on marking consecutive
   batches of packets, the method is often referred to as the Alternate
   Marking Method.

   This document defines how the Alternate Marking Method can be used to
   measure packet loss and delay metrics in IPv6.

   The format of IPv6 addresses is defined in [RFC4291] while [RFC8200]
   defines the IPv6 Header, including a 20-bit Flow Label and the IPv6
   Extension Headers.

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   [I-D.fioccola-v6ops-ipv6-alt-mark] summarizes the possible
   implementation options for the application of the Alternate Marking
   Method in an IPv6 domain.  This document, starting from the outcome
   of [I-D.fioccola-v6ops-ipv6-alt-mark], introduces a new TLV that can
   be encoded in the Options Headers (Hop-by-Hop or Destination) for the
   purpose of the Alternate Marking Method application in an IPv6
   domain.  While the case of Segment Routing Header (SRH), defined in
   [RFC8754], is also discussed, it is valid for all the types of
   Routing Header (RH).

1.1.  Terminology

   This document uses the terms related to the Alternate Marking Method
   as defined in [RFC8321] and [RFC8889].

1.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.  Alternate Marking application to IPv6

   The Alternate Marking Method requires a marking field.  As mentioned,
   several alternatives have been analysed in
   [I-D.fioccola-v6ops-ipv6-alt-mark] such as IPv6 Extension Headers,
   IPv6 Address and Flow Label.

   Consequently, a robust choice is to standardize a new Hop-by-Hop or
   Destination Option.

   This approach is compliant with [RFC8200].  The Alternate Marking
   application to IPv6 involves the following operations:

   o  The source node is the only one that writes the Option Header to
      mark alternately the flow (for both Hop-by-Hop and Destination

   o  In case of Hop-by-Hop Option Header carrying Alternate Marking
      bits, it is not inserted or deleted, but can be read by any node
      along the path.  The intermediate nodes may be configured to
      support this Option or not and the measurement can be done only
      for the nodes configured to read the Option.  Anyway this should
      not affect the traffic throughput on nodes that do not recognize
      the Option, as further discussed in Section 4.

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   o  In case of Destination Option Header carrying Alternate Marking
      bits, it is not processed, inserted, or deleted by any node along
      the path until the packet reaches the destination node.  Note
      that, if there is also a Routing Header (RH), any visited
      destination in the route list can process the Option Header.

   Hop-by-Hop Option Header is also useful to signal to routers on the
   path to process the Alternate Marking.  However, as said, routers
   will examine this option if properly configured.

   The optimization of both implementation and scaling of the Alternate
   Marking Method is also considered and a way to identify flows is
   required.  The Flow Monitoring Identification field (FlowMonID), as
   introduced in the next sections, goes in this direction and it is
   used to identify a monitored flow.

   Note that the FlowMonID is different from the Flow Label field of the
   IPv6 Header ([RFC8200]).  Flow Label is used for load-balancing/equal
   cost multi-path (LB/ECMP).  Instead, FlowMonID is only used to
   identify the monitored flow.  The reuse of flow label field for
   identifying monitored flows is not considered since it may change the
   application intent and forwarding behaviour.  Furthermore the flow
   label may be changed en route and this may also violate the
   measurement task.  Also, since the flow label is pseudo-random, there
   is always a finite probability of collision.  Those reasons make the
   definition of the FlowMonID necessary for IPv6.  Flow Label and
   FlowMonID within the same packet have different scope, identify
   different flows, and are intended for different use cases.

   An important point that will also be discussed in this document is
   the uniqueness of the FlowMonID and how to allow disambiguation of
   the FlowMonID in case of collision.  [RFC6437] states that the Flow
   Label cannot be considered alone to avoid ambiguity since it could be
   accidentally or intentionally changed en route for compelling
   operational security reasons.  But the Alternate Marking is usually
   applied in a controlled domain and there is no security issue that
   would necessitate rewriting Flow Labels.  So, for the purposes of
   this document, both IP addresses and Flow Label should not change in
   flight and, in some cases, they could be considered together with the
   FlowMonID for disambiguation.

2.1.  Controlled Domain

   [RFC8799] introduces the concept of specific limited domain solutions
   and, in this regard, it is reported the IPv6 Application of the
   Alternate Marking Method as an example.

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   IPv6 has much more flexibility than IPv4 and innovative applications
   have been proposed, but for a number of reasons, such as the options
   supported, the style of network management and security requirements,
   it is suggested to limit some of these applications to a controlled
   domain.  This is also the case of the Alternate Marking application
   to IPv6 as assumed hereinafter.

3.  Definition of the AltMark Option

   The desired choice is to define a new TLV for the Options Extension
   Headers, carrying the data fields dedicated to the alternate marking

3.1.  Data Fields Format

   The following figure shows the data fields format for enhanced
   alternate marking TLV.  This AltMark data is expected to be
   encapsulated in the IPv6 Options Headers (Hop-by-Hop or Destination

    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
                                   |  Option Type  |  Opt Data Len |
   |              FlowMonID                |L|D|     Reserved      |


   o  Option Type: 8 bit identifier of the type of Option that needs to
      be allocated.  Unrecognised Types MUST be ignored on receipt.  For
      Hop-by-Hop Options Header or Destination Options Header, [RFC8200]
      defines how to encode the three high-order bits of the Option Type
      field.  The two high-order bits specify the action that must be
      taken if the processing IPv6 node does not recognize the Option
      Type; for AltMark these two bits MUST be set to 00 (skip over this
      Option and continue processing the header).  The third-highest-
      order bit specifies whether or not the Option Data can change en
      route to the packet's final destination; for AltMark the value of
      this bit MUST be set to 0 (Option Data does not change en route).

   o  Opt Data Len: The length of the Option Data Fields of this Option
      in bytes.

   o  FlowMonID: 20 bits unsigned integer.  The FlowMon identifier is
      described in Section 5.3.

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   o  L: Loss flag for Packet Loss Measurement as described in
      Section 5.1;

   o  D: Delay flag for Single Packet Delay Measurement as described in
      Section 5.2;

   o  Reserved: is reserved for future use.  These bits MUST be set to
      zero on transmission and ignored on receipt.

4.  Use of the AltMark Option

   The AltMark Option is the best way to implement the Alternate Marking
   method and can be carried by the Hop-by-Hop Options header and the
   Destination Options header.  In case of Destination Option, it is
   processed only by the source and destination nodes: the source node
   inserts and the destination node removes it.  While, in case of Hop-
   by-Hop Option, it may be examined by any node along the path, if
   explicitly configured to do so.

   It is important to highlight that the Option Layout can be used both
   as Destination Option and as Hop-by-Hop Option depending on the Use
   Cases and it is based on the chosen type of performance measurement.
   In general, it is needed to perform both end to end and hop by hop
   measurements, and the alternate marking methodology allows, by
   definition, both performance measurements.  Anyway, in many cases the
   end-to-end measurement is not enough and it is required also the hop-
   by-hop measurement, so the most complete choice is the Hop-by-Hop
   Options Header.

   IPv6, as specified in [RFC8200], allows nodes to optionally process
   Hop-by-Hop headers.  Specifically the Hop-by-Hop Options header is
   not inserted or deleted, but may be examined or processed by any node
   along a packet's delivery path, until the packet reaches the node (or
   each of the set of nodes, in the case of multicast) identified in the
   Destination Address field of the IPv6 header.  Also, it is expected
   that nodes along a packet's delivery path only examine and process
   the Hop-by-Hop Options header if explicitly configured to do so.

   The Hop-by-Hop Option defined in this document is designed to take
   advantage of the property of how Hop-by-Hop options are processed.
   Nodes that do not support this Option SHOULD ignore them.  This can
   mean that, in this case, the performance measurement does not account
   for all links and nodes along a path.

   Another application that can be mentioned is the presence of a
   Routing Header, in particular it is possible to consider SRv6.  A new
   type of Routing Header, referred as SRH, has been defined for SRv6.
   Like any other use case of IPv6, Hop-by-Hop and Destination Options

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   are useable when SRv6 header is present.  Because SRv6 is implemented
   through a Segment Routing Header (SRH), Destination Options before
   the Routing Header are processed by each destination in the route
   list, that means, in case of SRH, by every SR node that is identified
   by the SR path.

   In summary, it is possible to list the alternative possibilities:

   o  Destination Option not preceding a Routing Header => measurement
      only by node in Destination Address.

   o  Hop-by-Hop Option => every router on the path with feature

   o  Destination Option preceding a Routing Header => every destination
      node in the route list.

   In general, Hop-by-Hop and Destination Options are the most suitable
   ways to implement Alternate Marking.

   It is worth mentioning that new Hop-by-Hop Options are not strongly
   recommended in [RFC7045] and [RFC8200], unless there is a clear
   justification to standardize it, because nodes may be configured to
   ignore the Options Header, drop or assign packets containing an
   Options Header to a slow processing path.  In case of the AltMark
   data fields described in this document, the motivation to standardize
   a new Hop-by-Hop Option is that it is needed for OAM.  An
   intermediate node can read it or not but this does not affect the
   packet behavior.  The source node is the only one that writes the
   Hop-by-Hop Option to mark alternately the flow, so, the performance
   measurement can be done for those nodes configured to read this
   Option, while the others are simply not considered for the metrics.

   It is important to highlight that the definition of the Hop-by-Hop
   Options in this document SHOULD NOT affect the throughput on nodes
   that do not recognize the Option.  Indeed, the three high-order bits
   of the Options Header defined in this draft are 000 and, in theory,
   as per [RFC8200] and [I-D.hinden-6man-hbh-processing], this means
   "skip if do not recognize and data do not change en route".
   [RFC8200] also mentions that the nodes only examine and process the
   Hop-by-Hop Options header if explicitly configured to do so.  For
   these reasons, this HbH Option should not affect the throughput.
   Anyway, in practice, it is important to be aware for the
   implementation that the things may be different and it can happen
   that packets with Hop-by-Hop are forced onto the slow path, but this
   is a general issue, as also explained in

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5.  Alternate Marking Method Operation

   This section describes how the method operates.  [RFC8321] introduces
   several alternatives but in this section the most applicable methods
   are reported and a new field is introduced to facilitate the
   deployment and improve the scalability.

5.1.  Packet Loss Measurement

   The measurement of the packet loss is really straightforward.  The
   packets of the flow are grouped into batches, and all the packets
   within a batch are marked by setting the L bit (Loss flag) to a same
   value.  The source node can switch the value of the L bit between 0
   and 1 after a fixed number of packets or according to a fixed timer,
   and this depends on the implementation.  By counting the number of
   packets in each batch and comparing the values measured by different
   network nodes along the path, it is possible to measure the packet
   loss occurred in any single batch between any two nodes.  Each batch
   represents a measurable entity unambiguously recognizable by all
   network nodes along the path.

   Packets with different L values may get swapped at batch boundaries,
   and in this case, it is required that each marked packet can be
   assigned to the right batch by each router.  It is important to
   mention that for the application of this method there are two
   elements to consider: the clock error between network nodes and the
   network delay.  These can create offsets between the batches and out-
   of-order of the packets.  There is the condition on timing aspects
   explained in [RFC8321] that must be satisfied and it takes into
   considerations the different causes of reordering such as clock
   error, network delay.  The consequence is that it is necessary to
   define a waiting interval where to get stable counters and to avoid
   these issues.  Usually the counters can be taken in the middle of the
   batch period to be sure to take still counters.  In a few words this
   implies that the length of the batches MUST be chosen large enough so
   that the method is not affected by those factors.

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   L bit=1   ----------+           +-----------+           +----------
                       |           |           |           |
   L bit=0             +-----------+           +-----------+
              Batch n        ...      Batch 3     Batch 2     Batch 1
            <---------> <---------> <---------> <---------> <--------->

                                Traffic Flow
   L bit   ...1111111111 0000000000 11111111111 00000000000 111111111...

     Figure 1: Packet Loss Measurement and Single-Marking Methodology
                                using L bit

5.2.  Packet Delay Measurement

   The same principle used to measure packet loss can be applied also to
   one-way delay measurement.  Delay metrics MAY be calculated using the
   two possibilities:

   1.  Single-Marking Methodology: This approach uses only the L bit to
       calculate both packet loss and delay.  In this case, the D flag
       MUST be set to zero on transmit and ignored by the monitoring
       points.  The alternation of the values of the L bit can be used
       as a time reference to calculate the delay.  Whenever the L bit
       changes and a new batch starts, a network node can store the
       timestamp of the first packet of the new batch, that timestamp
       can be compared with the timestamp of the first packet of the
       same batch on a second node to compute packet delay.  Anyway this
       measurement is accurate only if no packet loss occurs and if
       there is no packet reordering at the edges of the batches.  A
       different approach can also be considered and it is based on the
       concept of the mean delay.  The mean delay for each batch is
       calculated by considering the average arrival time of the packets
       for the relative batch.  There are limitations also in this case
       indeed, each node needs to collect all the timestamps and
       calculate the average timestamp for each batch.  In addition the
       information is limited to a mean value.

   2.  Double-Marking Methodology: This approach is more complete and
       uses the L bit only to calculate packet loss and the D bit (Delay
       flag) is fully dedicated to delay measurements.  The idea is to
       use the first marking with the L bit to create the alternate flow
       and, within the batches identified by the L bit, a second marking
       is used to select the packets for measuring delay.  The D bit
       creates a new set of marked packets that are fully identified
       over the network, so that a network node can store the timestamps

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       of these packets; these timestamps can be compared with the
       timestamps of the same packets on a second node to compute packet
       delay values for each packet.  The most efficient and robust mode
       is to select a single double-marked packet for each batch, in
       this way there is no time gap to consider between the double-
       marked packets to avoid their reorder.  If a double-marked packet
       is lost, the delay measurement for the considered batch is simply
       discarded, but this is not a big problem because it is easy to
       recognize the problematic batch and skip the measurement just for
       that one.  So in order to have more information about the delay
       and to overcome out-of-order issues this method is preferred.

   L bit=1   ----------+           +-----------+           +----------
                       |           |           |           |
   L bit=0             +-----------+           +-----------+

   D bit=1         +          +          +          +            +
                   |          |          |          |            |
   D bit=0   ------+----------+----------+----------+------------+-----

                                Traffic Flow
   L bit   ...1111111111 0000000000 11111111111 00000000000 111111111...

   D bit   ...0000010000 0000010000 00000100000 00001000000 000001000...

        Figure 2: Double-Marking Methodology using L bit and D bit

   Similar to packet delay measurement (both for Single Marking and
   Double Marking), the method can also be used to measure the inter-
   arrival jitter.

5.3.  Flow Monitoring Identification

   The Flow Monitoring Identification (FlowMonID) is required for some
   general reasons:

   o  First, it helps to reduce the per node configuration.  Otherwise,
      each node needs to configure an access-control list (ACL) for each
      of the monitored flows.  Moreover, using a flow identifier allows
      a flexible granularity for the flow definition.

   o  Second, it simplifies the counters handling.  Hardware processing
      of flow tuples (and ACL matching) is challenging and often incurs
      into performance issues, especially in tunnel interfaces.

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   o  Third, it eases the data export encapsulation and correlation for
      the collectors.

   The FlowMon identifier field is to uniquely identify a monitored flow
   within the measurement domain.  The field is set at the source node.
   The FlowMonID can be uniformly assigned by the central controller or
   algorithmically generated by the source node.  The latter approach
   cannot guarantee the uniqueness of FlowMonID but it may be preferred
   for local or private network, where the conflict probability is small
   due to the large FlowMonID space.

5.3.1.  Uniqueness of FlowMonID

   It is important to note that if the 20 bit FlowMonID is set
   independently and pseudo randomly there is a chance of collision.
   So, in some cases, FlowMonID could not be sufficient for uniqueness.

   In general the probability of a flow identifier uniqueness correlates
   to the amount of entropy of the inputs.  For instance, using the
   well-known birthday problem in probability theory, if the 20 bit
   FlowMonID is set independently and pseudo randomly without any
   additional input entropy, there is a 50% chance of collision for just
   1206 flows.  For a 32 bit identifier the 50% threshold jumps to
   77,163 flows and so on.  So, for more entropy, FlowMonID can either
   be combined with other identifying flow information in a packet (e.g.
   it is possible to consider the hashed 3-tuple Flow Label, Source and
   Destination addresses) or the FlowMonID size could be increased.

   This issue is more visible when the FlowMonID is pseudo randomly
   generated by the source node and there needs to tag it with
   additional flow information to allow disambiguation.  While, in case
   of a centralized controller, the controller should set FlowMonID by
   considering these aspects and instruct the nodes properly in order to
   guarantee its uniqueness.

   Anyway, it is worth highlighting that the uniqueness of FlowMonID may
   not be a problem and a low rate of ambiguous FlowMonIDs can be
   acceptable, since this does not cause significant harm to the
   operators or their clients and this harm may not justify the
   complications of avoiding it.  But, for large scale measurements
   where it is possible to monitor a big number of flows, the
   disambiguation of the Flow Monitoring Identification field is
   something to take into account.

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5.4.  Multipoint and Clustered Alternate Marking

   The Alternate Marking method can also be extended to any kind of
   multipoint to multipoint paths, and the network clustering approach
   allows a flexible and optimized performance measurement, as described
   in [RFC8889].

   The Cluster is the smallest identifiable subnetwork of the entire
   Network graph that still satisfies the condition that the number of
   packets that goes in is the same that goes out.  With network
   clustering, it is possible to use the partition of the network into
   clusters at different levels in order to perform the needed degree of
   detail.  So, for Multipoint Alternate Marking, FlowMonID can identify
   in general a multipoint-to-multipoint flow and not only a point-to-
   point flow.

5.5.  Data Collection and Calculation

   The nodes enabled to perform performance monitoring collect the value
   of the packet counters and timestamps.  There are several
   alternatives to implement Data Collection and Calculation, but this
   is not specified in this document.

6.  Security Considerations

   This document aims to apply a method to perform measurements that
   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.

   Harm caused by the measurement: Alternate Marking implies
   modifications on the fly to an Option Header of IPv6 packets by the
   source node but this must be performed in a way that does not alter
   the quality of service experienced by the packets and that preserves
   stability and performance of routers doing the measurements.  The
   advantage of the Alternate Marking method is that the marking bits
   are the only small information that is exchanged between the network
   nodes.  Therefore, due to this intrinsic characteristic, network
   reconnaissance through passive eavesdropping on data-plane traffic is
   difficult.  Indeed the only way for an attacker can be to eavesdrop
   on multiple nodes at the same time, apply the methodology and finally
   gain information about the network performance, but this is not
   immediate.  Moreover, Alternate Marking should usually be applied in
   a controlled domain and this also helps to limit the problem.

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   Harm to the Measurement: Alternate Marking measurements could be
   harmed by routers altering the marking of the packets or by an
   attacker injecting artificial traffic.  Since the measurement itself
   may be affected by network nodes along the path intentionally
   altering the value of the marking bits of IPv6 packets, the Alternate
   Marking should be applied in the context of a controlled domain,
   where the network nodes are locally administered and this type of
   attack can be avoided.  Indeed the source and destination addresses
   are within the controlled domain and therefore it is unlikely subject
   to hijacking of packets, because it is possible to filter external
   packets at the domain boundaries.  In addition, an attacker cannot
   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 as Alternate Marking requires.

   Additionally, it is to be noted that Alternate Marking bits are
   carried by the Options Header and it may have some impact on the
   packet sizes for the monitored flow and on the path MTU, since some
   packets might exceed the MTU.  Anyway the relative small size (48 bit
   in total) of these Option Headers and its application to a controlled
   domain help to mitigate the problem.

   The privacy concerns of network measurement are limited because the
   method only relies on information contained in the Option Header
   without any release of user data.  Although information in the Option
   Header is metadata that can be used to compromise the privacy of
   users, the limited marking technique seems unlikely to substantially
   increase the existing privacy risks from header or encapsulation

   The Alternate Marking application described in this document relies
   on an 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 [RFC7384].

7.  IANA Considerations

   The Option Type should be assigned in IANA's "Destination Options and
   Hop-by-Hop Options" registry.

   This draft requests the following IPv6 Option Type assignment from
   the Destination Options and Hop-by-Hop Options sub-registry of
   Internet Protocol Version 6 (IPv6) Parameters

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      Hex Value    Binary Value      Description           Reference
                   act chg rest
      TBD          00   0  tbd       AltMark               [This draft]

8.  Acknowledgements

   The authors would like to thank Bob Hinden, Ole Troan, Tom Herbert,
   Stefano Previdi, Brian Carpenter, Eric Vyncke, Ron Bonica, Greg
   Mirsky for the precious comments and suggestions.

9.  References

9.1.  Normative References

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,

9.2.  Informative References

              Fioccola, G., Velde, G. V. D., Cociglio, M., and P. Muley,
              "IPv6 Performance Measurement with Alternate Marking
              Method", draft-fioccola-v6ops-ipv6-alt-mark-01 (work in
              progress), June 2018.

              Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
              Processing Procedures", draft-hinden-6man-hbh-
              processing-00 (work in progress), December 2020.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

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   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437,
              DOI 10.17487/RFC6437, November 2011,

   [RFC7045]  Carpenter, B. and S. Jiang, "Transmission and Processing
              of IPv6 Extension Headers", RFC 7045,
              DOI 10.17487/RFC7045, December 2013,

   [RFC7384]  Mizrahi, T., "Security Requirements of Time Protocols in
              Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
              October 2014, <https://www.rfc-editor.org/info/rfc7384>.

   [RFC8321]  Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
              L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
              "Alternate-Marking Method for Passive and Hybrid
              Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
              January 2018, <https://www.rfc-editor.org/info/rfc8321>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,

   [RFC8799]  Carpenter, B. and B. Liu, "Limited Domains and Internet
              Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,

   [RFC8889]  Fioccola, G., Ed., Cociglio, M., Sapio, A., and R. Sisto,
              "Multipoint Alternate-Marking Method for Passive and
              Hybrid Performance Monitoring", RFC 8889,
              DOI 10.17487/RFC8889, August 2020,

Authors' Addresses

   Giuseppe Fioccola
   Riesstrasse, 25
   Munich  80992

   Email: giuseppe.fioccola@huawei.com

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   Tianran Zhou
   156 Beiqing Rd.
   Beijing  100095

   Email: zhoutianran@huawei.com

   Mauro Cociglio
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148

   Email: mauro.cociglio@telecomitalia.it

   Fengwei Qin
   China Mobile
   32 Xuanwumenxi Ave.
   Beijing  100032

   Email: qinfengwei@chinamobile.com

   Ran Pang
   China Unicom
   9 Shouti South Rd.
   Beijing  100089

   Email: pangran@chinaunicom.cn

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