Encapsulation For MPLS Performance Measurement with Alternate Marking Method
draft-ietf-mpls-inband-pm-encapsulation-01

Document Type Active Internet-Draft (mpls WG)
Authors Weiqiang Cheng  , Xiao Min  , Tianran Zhou  , Ximing Dong  , Yoav Peleg 
Last updated 2021-04-12 (latest revision 2021-04-11)
Replaces draft-cheng-mpls-inband-pm-encapsulation
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MPLS Working Group                                              W. Cheng
Internet-Draft                                              China Mobile
Intended status: Standards Track                                  X. Min
Expires: October 13, 2021                                      ZTE Corp.
                                                                 T. Zhou
                                                                  Huawei
                                                                 X. Dong
                                                               FiberHome
                                                                Y. Peleg
                                                                Broadcom
                                                          April 11, 2021

 Encapsulation For MPLS Performance Measurement with Alternate Marking
                                 Method
               draft-ietf-mpls-inband-pm-encapsulation-01

Abstract

   This document defines the encapsulation for MPLS performance
   measurement with alternate marking method, which performs flow-based
   packet loss, delay, and jitter measurements on live traffic.

Status of This Memo

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

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   This Internet-Draft will expire on October 13, 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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
       1.1.1.  Abbreviations . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   4
   2.  Flow-based PM Encapsulation in MPLS . . . . . . . . . . . . .   4
     2.1.  Examples for Applying Flow-ID Label in a label stack  . .   5
   3.  Procedures of Encapsulation, Look-up and Decapsulation  . . .   8
   4.  Procedures of Flow-ID allocation  . . . . . . . . . . . . . .   9
   5.  FLC and FRLD Considerations . . . . . . . . . . . . . . . . .  10
   6.  Equal-Cost Multipath Considerations . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   [RFC8321] describes a passive performance measurement method, which
   can be used to measure packet loss, delay, and jitter on live
   traffic.  Since this method is based on marking consecutive batches
   of packets, the method is often referred to as Alternate Marking
   Method.  [RFC8372] discusses the desired capabilities for MPLS flow
   identification, in order to perform a better in-band performance
   monitoring of user data packets.

   This document defines the encapsulation for MPLS performance
   measurement with alternate marking method, which performs flow-based
   packet loss, delay, and jitter measurements on live traffic.  The
   encapsulation defined in this document supports monitoring at
   intermediate nodes, as well as flow identification at both transport
   and service label.

   This document employs a method, other than Synonymous Flow Label
   (SFL), to accomplish MPLS flow identification.  The method described
   in this document is complementary to the SFL method [RFC8957]
   [I-D.ietf-mpls-sfl-control], the former mainly aims at hop-by-hop

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   performance measurement, and the latter mainly aims at end-to-end
   performance measurement.  Different sets of flows may use different
   methods.

   The method described in this document is also complementary to the
   In-situ OAM method [I-D.ietf-ippm-ioam-data]
   [I-D.ietf-ippm-ioam-direct-export], the former doesn't introduce any
   new header whereas the latter introduces a new In-situ OAM header,
   furthermore, the former requests the network nodes to report the data
   used for performance measurement, and the latter requests the network
   nodes to report the data used for operational and telemetry
   information collection.  One set of flows may use both of the two
   methods concurrently.

1.1.  Conventions Used in This Document

1.1.1.  Abbreviations

   ACL: Access Control List

   cSPL: Composite Special Purpose Label

   ECMP: Equal-Cost Multipath

   ELC: Entropy Label Capability

   ERLD: Entropy Readable Label Depth

   eSPL: Extended Special Purpose Label

   FLC: Flow-ID Label Capability

   FLI: Flow-ID Label Indicator

   FRLD: Flow-ID Readable Label Depth

   LSP: Label Switched Path

   MPLS: Multi-Protocol Label Switching

   NMS: Network Management System

   PHP: Penultimate Hop Popping

   PM: Performance Measurement

   PW: PseudoWire

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   SFL: Synonymous Flow Label

   SID: Segment ID

   SPL: Special Purpose Label

   SR: Segment Routing

   TC: Traffic Class

   TTL: Time to Live

   VC: Virtual Channel

   VPN: Virtual Private Network

1.1.2.  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.  Flow-based PM Encapsulation in MPLS

   Flow-based MPLS performance measurement encapsulation with alternate
   marking method has the following format:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Extension Label (15)         |  TC |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flow-ID Label Indicator (TBA1)    |  TC |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Flow-ID Label             |  TC |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Flow-based PM Encapsulation in MPLS

   Flow-ID Label Indicator (FLI) is an Extended Special Purpose Label
   (eSPL), which is combined with the Extension Label (XL, value 15) to
   form a Composite Special Purpose Label (cSPL), as defined in
   [RFC9017].  Flow-ID Label Indicator is defined in this document as
   value TBA1.

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   Analogous to Entropy Label Indicator [RFC6790], the TC and TTL for
   the Extension Label and the Flow-ID Label Indicator SHOULD follow the
   same field values of that label immediately preceding the Extension
   Label, otherwise, the TC and TTL for the Extension Label and the
   Flow-ID Label Indicator MAY be different values if it is known that
   the Extension Label will not be exposed as the top label at any point
   along the LSP.  The S bit for the Extension Label and the Flow-ID
   Label Indicator MUST be zero.

   Flow-ID label is used as MPLS flow identification [RFC8372], its
   value should be unique within the administrative domain.  Flow-ID
   values can be allocated by an external NMS or a controller, based on
   measurement object instance such as LSP or PW.  There is a one-to-one
   mapping between Flow-ID and flow.  The specific method on how to
   allocate the Flow-ID values is described in Section 4.

   Analogous to Entropy Label [RFC6790], the Flow-ID label can be placed
   at either the bottom or the middle of the MPLS label stack, and the
   Flow-ID label MAY appear multiple times in a label stack.
   Section 2.1 of this document provides several examples to illustrate
   how to apply Flow-ID label in a label stack.  Again analogous to
   Entropy Label, the TTL for the Flow-ID label MUST be zero to ensure
   that it is not used inadvertently for forwarding, the TC for the
   Flow-ID label may be any value, the S bit for the Flow-ID Label
   depends on whether or not there are more labels in the label stack.

   Besides flow identification, a color-marking field is also necessary
   for alternate marking method.  To achieve the purpose of coloring the
   MPLS traffic, the current practice when writing this document is to
   reuse the Flow-ID label's TC, i.e., using TC's highest order two bits
   (called double-marking methodology [RFC8321]) as color-marking bits.
   Alternatively, allocating multiple Flow-ID labels to the same flow
   may be used for the purpose of alternate marking.

2.1.  Examples for Applying Flow-ID Label in a label stack

   Three examples on different layout of Flow-ID label (4 octets) are
   illustrated as follows:

   (1) Layout of Flow-ID label when applied to MPLS transport.

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                +----------------------+
                |          LSP         |
                |         Label        |
                +----------------------+
                |       Extension      | <--+
                |         Label        |    |
                +----------------------+    |--- cSPL
                |     Flow-ID Label    |    |
                |       Indicator      | <--+
                +----------------------+
                |        Flow-ID       |
                |         Label        |
                +----------------------+
                |      Application     |
                |         Label        |
                +----------------------+ <= Bottom of stack
                |                      |
                |        Payload       |
                |                      |
                +----------------------+

               Figure 2: Applying Flow-ID to MPLS transport

   Note that here if penultimate hop popping (PHP) is in use, the PHP
   LSR that recognizes the cSPL MAY choose not to pop the cSPL and the
   following Flow-ID label, otherwise the egress LSR would be excluded
   from the performance measurement.

   Also note that in other examples of applying Flow-ID to MPLS
   transport, one LSP label can be substituted by multiple SID labels in
   the case of using SR Policy, and the combination of cSPL and Flow-ID
   label can be placed between SID labels, as specified in Section 5.

   (2) Layout of Flow-ID label when applied to MPLS service.

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                +----------------------+
                |          LSP         |
                |         Label        |
                +----------------------+
                |      Application     |
                |         Label        |
                +----------------------+
                |       Extension      | <--+
                |         Label        |    |
                +----------------------+    |--- cSPL
                |     Flow-ID Label    |    |
                |       Indicator      | <--+
                +----------------------+
                |        Flow-ID       |
                |         Label        |
                +----------------------+ <= Bottom of stack
                |                      |
                |        Payload       |
                |                      |
                +----------------------+

                Figure 3: Applying Flow-ID to MPLS service

   Note that here application label can be MPLS PW label, MPLS Ethernet
   VPN label or MPLS IP VPN label, and it's also called VC label as
   defined in [RFC4026].

   (3) Layout of Flow-ID label when applied to both MPLS transport and
   MPLS service.

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                +----------------------+
                |          LSP         |
                |         Label        |
                +----------------------+
                |       Extension      | <--+
                |         Label        |    |
                +----------------------+    |--- cSPL
                |     Flow-ID Label    |    |
                |       Indicator      | <--+
                +----------------------+
                |        Flow-ID       |
                |         Label        |
                +----------------------+
                |      Application     |
                |         Label        |
                +----------------------+
                |       Extension      | <--+
                |         Label        |    |
                +----------------------+    |--- cSPL
                |     Flow-ID Label    |    |
                |       Indicator      | <--+
                +----------------------+
                |        Flow-ID       |
                |         Label        |
                +----------------------+ <= Bottom of stack
                |                      |
                |        Payload       |
                |                      |
                +----------------------+

    Figure 4: Applying Flow-ID to both MPLS transport and MPLS service

   Note that for this example the two Flow-ID values appearing in a
   label stack MUST be different, that is to say, Flow-ID label applied
   to MPLS transport and Flow-ID label applied to MPLS service share the
   same value space.  Also note that the two Flow-ID label values are
   independent from each other, e.g., two packets can belong to the same
   VPN flow but to two different LSP flows, or two packets can belong to
   two different VPN flows but to the same LSP flow.

3.  Procedures of Encapsulation, Look-up and Decapsulation

   The procedures for Flow-ID label encapsulation, look-up and
   decapsulation are summarized as follows:

   o  The ingress node inserts the Extension Label, the Flow-ID Label
      Indicator, alongside with the Flow-ID label, into the MPLS label
      stack.  At the same time, the ingress node sets the color-marking

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      field, as needed by alternate-marking technique, and sets the
      Flow-ID value, as defined in this document.

   o  The transit nodes lookup the Flow-ID label with the help of the
      Extension Label and the Flow-ID Label Indicator, and transmit the
      collected information to an external NMS or a controller, which
      includes the values of the block counters and the timestamps of
      the marked packets, along with the value of the Flow-ID, referring
      to the procedures of alternate marking method.  Note that in order
      to lookup the Flow-ID label, the transit nodes need to perform
      some deep packet inspection beyond the label at the top of the
      label stack used to take forwarding decisions.

   o  The egress node pops the Extension Label and the Flow-ID Label
      Indicator, alongside with the Flow-ID label, from the MPLS label
      stack.  This document doesn't introduce any new procedure
      regarding to the process of the decapsulated packet.

4.  Procedures of Flow-ID allocation

   There are two ways of allocating Flow-ID, one way is to allocate
   Flow-ID by manual trigger from the network operator, and the other
   way is to allocate Flow-ID by automatic trigger from the ingress
   node, details are as follows:

   o  In the case of manual trigger, the network operator would manually
      input the characteristics (e.g.  IP five tuples and IP DSCP) of
      the measured flow, then the NMS or the controller would generate
      one or two Flow-IDs based on the input from the network operator,
      and provision the ingress node with the characteristics of the
      measured flow and the corresponding allocated Flow-ID(s).

   o  In the case of automatic trigger, the ingress node would identify
      the flow entering the measured path, export the characteristics of
      the identified flow to the NMS or the controller by IPFIX
      [RFC7011], then the NMS or the controller would generate one or
      two Flow-IDs based on the export from the ingress node, and
      provision the ingress node with the characteristics of the
      identified flow and the corresponding allocated Flow-ID(s).

   The policy pre-configured at the NMS or the controller decides
   whether one Flow-ID or two Flow-IDs would be generated.  If the
   performance measurement on MPLS service is enabled, then one Flow-ID
   applied to MPLS service would be generated; if the performance
   measurement on MPLS transport is enabled, then one Flow-ID applied to
   MPLS transport would be generated; if both of them are enabled, then
   two Flow-IDs respectively applied to MPLS service and MPLS transport
   would be generated, in this case the transit nodes need to lookup

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   both of the two Flow-IDs by default, and that can be changed to e.g.
   lookup only the Flow-ID applied to MPLS transport by configuration.

   Whether using manual trigger or using automatic trigger, the NMS or
   the controller MUST guarantee every generated Flow-ID is unique
   within the administrative domain.

5.  FLC and FRLD Considerations

   Analogous to the Entropy Label Capability (ELC) defined in Section 5
   of [RFC6790], and the Entropy Readable Label Depth (ERLD) defined in
   Section 4 of [RFC8662], the Flow-ID Label Capability (FLC) and the
   Flow-ID Readable Label Depth (FRLD) are defined in this document.
   Both FLC and FRLD have the similar semantics with ELC and ERLD to a
   router, except that the Flow-ID is used in its flow identification
   function while the Entropy is used in its load-balancing function.

   The ingress node MUST insert each Flow-ID label at an appropriate
   depth, which ensures the node that needs to process the Flow-ID label
   has the FLC.  The ingress node SHOULD insert each Flow-ID label
   within an appropriate FRLD, which is the minimum FRLD of all on-path
   nodes that needs to read and use the Flow-ID label in question.  How
   the ingress node knows the Flow-ID label processing node has the FLC
   and the appropriate FRLD for each Flow-ID label are outside the scope
   of this document, whereas [I-D.xzc-lsr-mpls-flc-flrd] provides a
   method to achieve that.

   When SR paths are used as transport, the label stack grows as the
   number of on-path segments increases, if the number of on-path
   segments is high, that may become a challenge for the Flow-ID label
   to be placed within an appropriate FRLD.  In order to overcome this
   potential challenge, an implementation MAY provide flexibility to the
   ingress node to place Flow-ID label between SID labels, i.e.,
   multiple identical Flow-ID labels at different depths MAY be
   interleaved with SID labels, when that happens a sophisticated
   network planning may be needed and it's beyond the scope of this
   document.

6.  Equal-Cost Multipath Considerations

   Analogous to what's described in Section 5 of [RFC8957], under
   conditions of Equal-Cost Multipath (ECMP), the introduction of a
   Flow-ID label may cause the same problem as the introduction of an
   SFL, and the two solutions proposed for the problem caused by the
   introduction of SFL would also apply here.

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7.  Security Considerations

   This document introduces the performance measurement domain that is
   the scope of a Flow-ID label.  The Flow-ID Label Indicator and Flow-
   ID label MUST NOT be signaled and distributed outside one performance
   measurement domain.  Improper configuration so that the Flow-ID label
   being passed from one domain to another would likely result in
   potential Flow-ID conflicts.

   To prevent packets carrying Flow-ID label from leaking from one
   domain to another, the domain boundary nodes SHOULD deploy some
   policies (e.g., ACL) to filter out the packets.  Specifically, in the
   sending end, the domain boundary node SHOULD filter out the packets
   that carry the Flow-ID Label Indicator and are sent to other domain;
   in the receiving end, the domain boundary node SHOULD drop the
   packets that carry the Flow-ID Label Indicator and are from other
   domains.

8.  IANA Considerations

   In the Special-Purpose MPLS Label Values registry defined in [SPL], a
   new Extended Special-Purpose MPLS Label Value for Flow-ID Label
   Indicator is requested from IANA as follows:

   +-----------------------+----------------+--------------+-----------+
   | Extended Special-     | Description    | Semantics    | Reference |
   | Purpose MPLS Label    |                | Definition   |           |
   | Value                 |                |              |           |
   +-----------------------+----------------+--------------+-----------+
   | TBA1                  | Flow-ID Label  | Section 2    | This      |
   |                       | Indicator      |              | Document  |
   +-----------------------+----------------+--------------+-----------+

    Table 1: New Extended Special-Purpose MPLS Label Value for Flow-ID
                              Label Indicator

9.  Acknowledgements

   The authors would like to acknowledge Loa Andersson, Tarek Saad,
   Stewart Bryant, Rakesh Gandhi, Greg Mirsky, Aihua Liu, Shuangping
   Zhan and Ming Ke for their careful review and very helpful comments.

   The authors would like to acknowledge Italo Busi and Chandrasekar
   Ramachandran for their insightful MPLS-RT review and very helpful
   comments.

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10.  References

10.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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>.

   [SPL]      IANA, "Special-Purpose Multiprotocol Label Switching
              (MPLS) Label Values",
              <https://www.iana.org/assignments/mpls-label-values/>.

10.2.  Informative References

   [I-D.ietf-ippm-ioam-data]
              Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
              for In-situ OAM", draft-ietf-ippm-ioam-data-11 (work in
              progress), November 2020.

   [I-D.ietf-ippm-ioam-direct-export]
              Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
              Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
              OAM Direct Exporting", draft-ietf-ippm-ioam-direct-
              export-02 (work in progress), November 2020.

   [I-D.ietf-mpls-sfl-control]
              Bryant, S., Swallow, G., and S. Sivabalan, "A Simple
              Control Protocol for MPLS SFLs", draft-ietf-mpls-sfl-
              control-00 (work in progress), January 2021.

   [RFC4026]  Andersson, L. and T. Madsen, "Provider Provisioned Virtual
              Private Network (VPN) Terminology", RFC 4026,
              DOI 10.17487/RFC4026, March 2005,
              <https://www.rfc-editor.org/info/rfc4026>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

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   [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,
              <https://www.rfc-editor.org/info/rfc7011>.

   [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>.

   [RFC8372]  Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
              Mirsky, "MPLS Flow Identification Considerations",
              RFC 8372, DOI 10.17487/RFC8372, May 2018,
              <https://www.rfc-editor.org/info/rfc8372>.

   [RFC8662]  Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and J. Tantsura, "Entropy Label for Source
              Packet Routing in Networking (SPRING) Tunnels", RFC 8662,
              DOI 10.17487/RFC8662, December 2019,
              <https://www.rfc-editor.org/info/rfc8662>.

   [RFC8957]  Bryant, S., Chen, M., Swallow, G., Sivabalan, S., and G.
              Mirsky, "Synonymous Flow Label Framework", RFC 8957,
              DOI 10.17487/RFC8957, January 2021,
              <https://www.rfc-editor.org/info/rfc8957>.

   [RFC9017]  Andersson, L., Kompella, K., and A. Farrel, "Special-
              Purpose Label Terminology", RFC 9017,
              DOI 10.17487/RFC9017, April 2021,
              <https://www.rfc-editor.org/info/rfc9017>.

Authors' Addresses

   Weiqiang Cheng
   China Mobile
   Beijing
   China

   Email: chengweiqiang@chinamobile.com

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   Xiao Min
   ZTE Corp.
   Nanjing
   China

   Email: xiao.min2@zte.com.cn

   Tianran Zhou
   Huawei
   Beijing
   China

   Email: zhoutianran@huawei.com

   Ximing Dong
   FiberHome
   Wuhan
   China

   Email: dxm@fiberhome.com

   Yoav Peleg
   Broadcom
   USA

   Email: yoav.peleg@broadcom.com

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