Encapsulation For MPLS Performance Measurement with Alternate Marking Method
draft-ietf-mpls-inband-pm-encapsulation-05

MPLS Working Group                                              W. Cheng
Internet-Draft                                              China Mobile
Intended status: Standards Track                             X. Min, Ed.
Expires: 13 September 2023                                     ZTE Corp.
                                                                 T. Zhou
                                                                  Huawei
                                                                 X. Dong
                                                               FiberHome
                                                                Y. Peleg
                                                                Broadcom
                                                           12 March 2023

 Encapsulation For MPLS Performance Measurement with Alternate Marking
                                 Method
               draft-ietf-mpls-inband-pm-encapsulation-05

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 MPLS live traffic.

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
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   This Internet-Draft will expire on 13 September 2023.

Copyright Notice

   Copyright (c) 2023 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 publication of this document.

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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

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 . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   [RFC9341] describes a 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,
   it's referred to as Alternate-Marking Method.  [RFC8372] describes
   the desired capabilities for MPLS flow identification, intended for
   in-band performance monitoring of MPLS flows.

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

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   This document employs an encapsulation method, other than Synonymous
   Flow Label (SFL), to achieve 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 processing and the latter mainly aims at edge-to-edge
   processing.  Different sets of MPLS flows may use different methods.

   The method described in this document is also complementary to the
   In-situ OAM method [RFC9197] [RFC9326], the former doesn't introduce
   any new header whereas the latter introduces a new In-situ OAM
   header.  Furthermore, the former requires the network nodes to
   collect the data used for performance measurement, while the latter
   requires the network nodes to collect the data used for operational
   and telemetry information collection.  An MPLS flow may apply both of
   the two methods concurrently.

1.1.  Conventions Used in This Document

1.1.1.  Abbreviations

   ACL: Access Control List

   BoS: Bottom of Stack

   cSPL: Composite Special Purpose Label

   ECMP: Equal-Cost Multipath

   ELC: Entropy Label Capability

   ERLD: Entropy Readable Label Depth

   eSPL: Extended Special Purpose Label

   FL: Flow-ID 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

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   PHP: Penultimate Hop Popping

   PM: Performance Measurement

   PW: PseudoWire

   SFL: Synonymous Flow Label

   SID: Segment ID

   SR: Segment Routing

   TC: Traffic Class

   TTL: Time to Live

   VC: Virtual Channel

   VPN: Virtual Private Network

   XL: Extension Label

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             |L|D|T|S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Flow-based PM Encapsulation in MPLS

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   The 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].  The FLI is defined in this document as value TBA1.

   The Traffic Class (TC) and Time To Live (TTL) [RFC3032] for the XL
   and FLI SHOULD follow the same field values of that label immediately
   preceding the XL.  Otherwise, the TC and TTL for the XL and FLI MAY
   be different values if it is known that the XL will not be exposed as
   the top label at any point along the LSP.  The Bottom of Stack (BoS)
   bit [RFC3032] for the XL and FLI MUST be zero.

   The Flow-ID Label (FL) is used as an MPLS flow identification
   [RFC8372], its value MUST be unique within the administrative domain.
   Flow-ID values can be allocated by an external NMS/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.

   The FL can be placed at either the bottom or the middle of the MPLS
   label stack, and the FL MAY appear multiple times in a label stack.
   Section 2.1 of this document provides several examples to illustrate
   how to apply FL in a label stack.  The TTL for the FL MUST be zero to
   ensure that it is not used inadvertently for forwarding.  The BoS bit
   for the FL depends on whether the FL is placed at the bottom of the
   MPLS label stack.

   Besides the flow identification, a color-marking field is also
   necessary for alternate marking method.  To achieve the purpose of
   coloring the MPLS traffic, as well as the distinction between hop-by-
   hop measurement and edge-to-edge measurement, the TC for the FL is
   defined as follows:

   *  L(oss) bit is used for coloring the MPLS packets for loss
      measurement.

   *  D(elay) bit is used for coloring the MPLS packets for delay/jitter
      measurement.

   *  T(ype) bit is used to indicate the measurement type.  When T bit
      is set to 1, that means edge-to-edge performance measurement.
      When T bit is set to 0, that means hop-by-hop performance
      measurement.

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:

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

                +----------------------+
                |          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 the 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 the 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, the Flow-ID label
   applied to MPLS transport and the 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 two different LSP flows, or two
   packets can belong to two different VPN flows but 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:

   *  The ingress node inserts the XL, FLI and FL into the MPLS label
      stack.  At the same time, the ingress node sets the Flow-ID value,
      the two color-marking bits and the T bit, as defined in Section 2.

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   *  If the hop-by-hop measurement is applied, i.e., the T bit is set
      to 0, then whether the transit node or the egress node is the
      processing node.  If the edge-to-edge measurement is applied,
      i.e., the T bit is set to 1, then only the egress node is the
      processing node.  The processing node looks up the FL with the
      help of the XL and FLI, and exports the collected data, such as
      the Flow-ID, block counters and timestamps, to an external NMS/
      controller, referring to the alternate marking method.  Note that
      while looking up the Flow-ID label, the transit node needs to
      perform some deep packet inspection beyond the label (at the top
      of the label stack) used to take forwarding decisions.

   *  The processing node may also pop the XL, FLI and FL from the MPLS
      label stack.  The egress node pops the whole MPLS label stack, and
      this document doesn't introduce any new process to 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:

   *  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/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).

   *  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/controller by IPFIX [RFC7011], then
      the NMS/controller would generate one or two Flow-IDs based on the
      characteristics exported from the ingress node, and provision the
      ingress node with the characteristics of the identified flow and
      the corresponding allocated Flow-ID(s).

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   The policy pre-configured at the NMS/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 node needs to look up both of
   the two Flow-IDs by default, and that can be changed by configuration
   to, e.g., look up only the Flow-ID applied to MPLS transport.

   Whether using manual trigger or automatic trigger, the NMS/controller
   MUST guarantee every generated Flow-ID is unique within the
   administrative domain and MUST NOT have a value in the reserved label
   space (0-15) [RFC3032].

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 the 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 FL at an appropriate depth, which
   ensures the node to which the FL is exposed has the FLC.  The ingress
   node SHOULD insert each FL within an appropriate FRLD, which is the
   minimum FRLD of all the on-path nodes that need to read and use the
   FL in question.  How the ingress node knows the FLC and FRLD of all
   the on-path nodes is outside the scope of this document, whereas
   [I-D.xzc-lsr-mpls-flc-frld] provides a method to achieve that.

   When the SR paths are used for 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 FL 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 FL between SID labels, i.e., multiple identical FLs 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.

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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 the FL
   may lead to the same problem as caused by the SFL, and the two
   solutions proposed for SFL would also apply here.

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 edge, 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 edge, 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, a new Extended
   Special-Purpose MPLS Label Value for the Flow-ID Label Indicator is
   requested from IANA as follows:

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

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

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9.  Acknowledgements

   The authors would like to acknowledge Loa Andersson, Tarek Saad,
   Stewart Bryant, Rakesh Gandhi, Greg Mirsky, Aihua Liu, Shuangping
   Zhan, Ming Ke, and Wei He 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.

10.  Contributors

   Minxue Wang
   China Mobile
   Email: wangminxue@chinamobile.com

   Wen Ye
   China Mobile
   Email: yewen@chinamobile.com

11.  References

11.1.  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>.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [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>.

   [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>.

   [RFC9341]  Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
              and T. Zhou, "Alternate-Marking Method", RFC 9341,
              DOI 10.17487/RFC9341, December 2022,
              <https://www.rfc-editor.org/info/rfc9341>.

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11.2.  Informative References

   [I-D.ietf-mpls-sfl-control]
              Bryant, S., Swallow, G., and S. Sivabalan, "A Simple
              Control Protocol for MPLS SFLs", Work in Progress,
              Internet-Draft, draft-ietf-mpls-sfl-control-03, 6 August
              2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
              mpls-sfl-control-03>.

   [I-D.xzc-lsr-mpls-flc-frld]
              Min, X., Zhang, Z., and W. Cheng, "Signaling Flow-ID Label
              Capability and Flow-ID Readable Label Depth", Work in
              Progress, Internet-Draft, draft-xzc-lsr-mpls-flc-frld-02,
              10 February 2023, <https://datatracker.ietf.org/doc/html/
              draft-xzc-lsr-mpls-flc-frld-02>.

   [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>.

   [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>.

   [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>.

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   [RFC9197]  Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
              Ed., "Data Fields for In Situ Operations, Administration,
              and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
              May 2022, <https://www.rfc-editor.org/info/rfc9197>.

   [RFC9326]  Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
              Mizrahi, "In Situ Operations, Administration, and
              Maintenance (IOAM) Direct Exporting", RFC 9326,
              DOI 10.17487/RFC9326, November 2022,
              <https://www.rfc-editor.org/info/rfc9326>.

Authors' Addresses

   Weiqiang Cheng
   China Mobile
   Beijing
   China
   Email: chengweiqiang@chinamobile.com

   Xiao Min (editor)
   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
   United States of America
   Email: yoav.peleg@broadcom.com

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