DetNet Working Group                                           G. Mirsky
Internet-Draft                                                  Ericsson
Intended status: Standards Track                                 M. Chen
Expires: 23 March 21 April 2022                                            Huawei
                                                       19 September
                                                         18 October 2021

   Operations, Administration and Maintenance (OAM) for Deterministic
                 Networks (DetNet) with MPLS Data Plane


   This document defines format and use principals of the Deterministic
   Network (DetNet) service Associated Channel (ACH) over a DetNet
   network with the MPLS data plane.  The DetNet service ACH can be used
   to carry test packets of active Operations, Administration, and
   Maintenance protocols that are used to detect DetNet failures and
   measure performance metrics.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 23 March 21 April 2022.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology and Acronyms  . . . . . . . . . . . . . . . .   3
     2.2.  Keywords  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Active OAM for DetNet Networks with MPLS Data Plane . . . . .   4
     3.1.  DetNet Active OAM Encapsulation . . . . . . . . . . . . .   5
     3.2.  DetNet Packet Replication, Elimination, and Ordering Sub-functions
           Functions Interaction with Active OAM . . . . . . . . . . . . . . .   7
   4.  Use of Hybrid OAM in DetNet . . . . . . . . . . . . . . . . .   7
   5.  OAM Interworking Models . . . . . . . . . . . . . . . . . . .   8   7
     5.1.  OAM of DetNet MPLS Interworking with OAM of TSN . . . . .   8
     5.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informational References  . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   [RFC8655] introduces and explains Deterministic Networks (DetNet)
   architecture and how the Packet Replication Replication, Elimination, and Elimination function
   Ordering functions (PREOF) can be used to ensure low packet drop
   ratio in DetNet domain.

   Operations, Administration and Maintenance (OAM) protocols are used
   to detect, localize defects in the network, and monitor network
   performance.  Some OAM functions, e.g., failure detection, work in
   the network proactively, while others, e.g., defect localization,
   usually performed on-demand.  These tasks achieved by a combination
   of active and hybrid, as defined in [RFC7799], OAM methods.

   Also, this document defines format and use principals of the DetNet
   service Associated Channel over a DetNet network with the MPLS data
   plane [RFC8964].

2.  Conventions used in this document

2.1.  Terminology and Acronyms

   The term "DetNet OAM" used in this document interchangeably with
   longer version "set of OAM protocols, methods and tools for
   Deterministic Networks".

   CW Control Word

   DetNet Deterministic Networks

   d-ACH DetNet Associated Channel Header

   d-CW DetNet Control Word

   DNH DetNet Header

   GAL Generic Associated Channel Label

   G-ACh Generic Associated Channel

   OAM: Operations, Administration and Maintenance


   PREOF Packet Replication Replication, Elimination, and Elimination Function

   POF Packet Ordering Function Functions

   PW Pseudowire

   RDI Remote Defect Indication

   E2E End-to-end

   CFM Connectivity Fault Management

   BFD Bidirectional Forwarding Detection

   TSN Time-Sensitive Network

   F-Label A Detnet "forwarding" label that identifies the LSP used to
   forward a DetNet flow across an MPLS PSN, e.g., a hop-by-hop label
   used between label switching routers (LSR).

   S-Label A DetNet "service" label that is used between DetNet nodes
   that implement also the DetNet service sub-layer functions.  An
   S-Label is also used to identify a DetNet flow at DetNet service sub-

   Underlay Network or Underlay Layer: The network that provides
   connectivity between the DetNet nodes.  MPLS network providing LSP
   connectivity between DetNet nodes is an example of the underlay

   DetNet Node - a node that is an actor in the DetNet domain.  DetNet
   domain edge node and node that performs PREF PREOF within the domain are
   examples of DetNet node.

2.2.  Keywords

   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.

3.  Active OAM for DetNet Networks with MPLS Data Plane

   OAM protocols and mechanisms act within the data plane of the
   particular networking layer.  And thus it is critical that the data
   plane encapsulation supports OAM mechanisms in such a way to comply
   with the OAM requirements listed in [I-D.tpmb-detnet-oam-framework].
   One of such examples that require special consideration is
   requirement #5:

      DetNet OAM packets MUST be in-band, i.e., follow precisely the
      same path as DetNet data plane traffic both for unidirectional and
      bi-directional DetNet paths.

   The Det Net data plane encapsulation in transport network with MPLS
   encapsulation specified in [RFC8964].  For the MPLS underlay network,
   DetNet flows to be encapsulated analogous to pseudowires (PW) over
   MPLS packet switched network, as described in [RFC3985], [RFC4385].
   Generic PW MPLS Control Word (CW), defined in [RFC4385], for DetNet
   displayed in Figure 1.

        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
       |0 0 0 0|                Sequence Number                        |

                    Figure 1: DetNet Control Word Format


   PREOF in the DetNet domain composed by a combination of nodes that
   perform replication and elimination sub-functions. functions.  The elimination
   function always uses the S-Label and packet sequencing information,
   e.g., the value in the Sequence Number field of DetNet CW (d-CW).
   The replication sub-function uses the S-Label information only.  For
   data packets Figure 2 presents an example of PREF PREOF in DetNet domain.

         1111   11111111  111111   112212   112212     132213
               \2          22222/                 3 /
                \2222222  /----+                 3 /

                  Figure 2: DetNet Data Plane Based on PW

3.1.  DetNet Active OAM Encapsulation

   DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in
   [RFC4385].  Figure 3 displays the encapsulation of a DetNet MPLS
   [RFC8964] active OAM packet.

         |                                 |
         |        DetNet App-Flow         |
         |         Payload OAM Packet        |
         |                                 |
         +---------------------------------+ <--\
         | DetNet Associated Channel Header|    |
         +---------------------------------+    +--> DetNet active OAM
         |           S-Label               |    |    MPLS encapsulation
         +---------------------------------+    |
         |         [ F-Label(s) ]          |    |
         +---------------------------------+ <--/
         |           Data-Link             |
         |           Physical              |

    Figure 3: DetNet Active OAM Packet Encapsulation in MPLS Data Plane

   Figure 4 displays encapsulation of a test packet of an active DetNet
   OAM protocol in case of MPLS-over-UDP/IP [RFC9025].

         |                                 |
         |        DetNet App-Flow         |
         |         Payload OAM Packet        |
         |                                 |
         +---------------------------------+ <--\
         | DetNet Associated Channel Header|    |
         +---------------------------------+    +--> DetNet active OAM
         |             S-Label             |    |    MPLS encapsulation
         +---------------------------------+    |
         |          [ F-label(s) ]         |    |
         +---------------------------------+ <--+
         |           UDP Header            |    |
         +---------------------------------+    +--> DetNet data plane
         |           IP Header             |    |    IP encapsulation
         +---------------------------------+ <--/
         |           Data-Link             |
         |           Physical              |

    Figure 4: DetNet Active OAM Packet Encapsulation in MPLS-over-UDP/IP

   Figure 5 displays the format of the DetNet Associated Channel Header

       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
      |0 0 0 1|Version|Sequence Number|         Channel Type          |

             Figure 5: DetNet Associated Channel Header Format

   The meanings of the fields in the d-ACH are:

      Bits 0..3 MUST be 0b0001.  This value of the first nibble allows
      the packet to be distinguished from an IP packet [RFC4928] and a
      DetNet data packet [RFC8964].

      Version: this is the version number of the d-ACH.  This
      specification defines version 0.

      Sequence Number: this is unsigned eight bits-long field.  The
      originating DetNet node MUST set the value of the Sequence Number
      field to a non-zero before packet being transmitted.  The originating node MUST
      monotonically increase the value of the Sequence Number field for
      the every next active OAM packet.

      Channel Type: the value of DetNet Associated Channel Type is one
      of values defined in the IANA PW Associated Channel Type registry.

   The DetNet flow, according to [RFC8964], is identified by the S-label
   that MUST be at the bottom of the stack.  Active OAM packet MUST have
   d-ACH immediately following the S-label.

3.2.  DetNet Packet Replication, Elimination, and Ordering Sub-functions Functions
      Interaction with Active OAM

   At the DetNet service layer, sub-layer, special functions MAY be applied to
   the particular DetNet flow - PREF flow, PREOF, to potentially lower packet loss,
   improve the probability of on-time packet delivery and Packet
   Ordering Function (POF) to ensure in-order in-
   order packet delivery.  As data
   and the active OAM packets have the same Flow ID, S-label, sub-
   functions that  PREOF rely on sequencing information in the
   DetNet service
   layer MUST process sub-layer.  For a DetNet active OAM packet, 28 MSBs of
   the d-ACH MUST be used as the source of the sequencing information for the OAM packet. by

4.  Use of Hybrid OAM in DetNet

   Hybrid OAM methods are used in performance monitoring and defined in
   [RFC7799] as:

      Hybrid Methods are Methods of Measurement that use a combination
      of Active Methods and Passive Methods.

   A hybrid measurement method may produce metrics as close to passive,
   but it still alters something in a data packet even if that is the
   value of a designated field in the packet encapsulation.  One example
   of such a hybrid measurement method is the Alternate Marking method
   described in [RFC8321].  Reserving the field for the Alternate
   Marking method in the DetNet Header will enhance available to an
   operator set of DetNet OAM tools.

5.  OAM Interworking Models

   Interworking of two OAM domains that utilize different networking
   technology can be realized either by a peering or a tunneling model.
   In a peering model, OAM domains are within the corresponding network
   domain.  When using the peering model, state changes that are
   detected by a Fault Management OAM protocol can be mapped from one
   OAM domain into another or a notification, e.g., an alarm, can be
   sent to a central controller.  In the tunneling model of OAM
   interworking, usually, only one active OAM protocol is used.  Its
   test packets are tunneled through another domain along with the data
   flow, thus ensuring the fate sharing among test and data packets.

5.1.  OAM of DetNet MPLS Interworking with OAM of TSN

   Active DetNet OAM is required to provide the E2E fault management and
   performance monitoring for a DetNet flow.  Interworking of DetNet
   active OAM with MPLS data plane with the IEEE 802.1 Time-Sensitive
   Networking (TSN) domain based on [RFC9037].

   In the case of the peering model is used in the fault management OAM,
   then the node that borders both TSN and DetNet MPLS domains MUST
   support [RFC7023].  [RFC7023] specified the mapping of defect states
   between Ethernet Attachment Circuits (ACs) and associated Ethernet
   PWs that are part of an end-to-end (E2E) emulated Ethernet service.
   Requirements and mechanisms described in [RFC7023] are equally
   applicable to using the peering model to achieve E2E FM OAM over
   DetNet MPLS and TSN domains.  The Connectivity Fault Management (CFM)
   protocol [IEEE.CFM] or in [ITU.Y1731] can provide fast detection of a
   failure in the TSN segment of the DetNet service.  In the DetNet MPLS
   domain BFD (Bidirectional Forwarding Detection), specified in
   [RFC5880] and [RFC5885], can be used.  To provide E2E failure
   detection, the TSN segment might be presented as a concatenated with
   the DetNet MPLS and the Section 6.8.17 [RFC5880] MAY be used to
   inform the upstream DetNet MPLS node of a failure of the TSN segment.
   Performance monitoring can be supported by [RFC6374] in the DetNet
   MPLS and [ITU.Y1731] in the TSN domains, respectively.  Performance
   objectives for each domain should refer to metrics that additive or
   be defined for each domain separately.

   The following considerations are to be realized when using the
   tunneling model of OAM interworking between DetNet MPLS and TSN

   *  Active OAM test packet MUST be mapped to the same TSN Stream ID as
      the monitored DetNet flow.

   *  Active OAM test packets MUST be treated in the TSN domain based on
      its S-label and CoS marking (TC field value).

   Note that the tunneling model of the OAM interworking requires that
   the remote peer of the E2E OAM domain supports the active OAM
   protocol selected on the ingress endpoint.  For example, if BFD is
   used for proactive path continuity monitoring in the DetNet MPLS
   domain, a TSN endpoint of the DetNet service has also support BFD as
   defined in [RFC5885].

5.2.  OAM of DetNet MPLS Interworking with OAM of DetNet IP

   Interworking between active OAM segments in DetNet MPLS and DetNet IP
   domains can also be realized using either the peering or the
   tunneling model, as discussed in Section 5.1.  Using the same
   protocol, e.g., BFD, over both segments, simplifies the mapping of
   errors in the peering model.  To provide the performance monitoring
   over a DetNet IP domain STAMP [RFC8762] and its extensions [RFC8972]
   can be used.

6.  IANA Considerations

   This document does not have any requests for IANA allocation.  This
   section can be deleted before the publication of the draft.

7.  Security Considerations

   Additionally, security considerations discussed in DetNet
   specifications: [RFC8655], [RFC9055], [RFC8964] are applicable to
   this document.  Security concerns and issues related to MPLS OAM
   tools like LSP Ping [RFC8029], BFD over PW [RFC5885] also apply to
   this specification.

8.  Acknowledgment

   Authors extend their appreciation to Pascal Thubert for his
   insightful comments and productive discussion that helped to improve
   the document.

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,

   [RFC7023]  Mohan, D., Ed., Bitar, N., Ed., Sajassi, A., Ed., DeLord,
              S., Niger, P., and R. Qiu, "MPLS and Ethernet Operations,
              Administration, and Maintenance (OAM) Interworking",
              RFC 7023, DOI 10.17487/RFC7023, October 2013,

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

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,

   [RFC8964]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
              S., and J. Korhonen, "Deterministic Networking (DetNet)
              Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
              2021, <>.

   [RFC9025]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane:
              MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
              2021, <>.

9.2.  Informational References

              Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., and C. J.
              Bernardos, "Framework of Operations, Administration and
              Maintenance (OAM) for Deterministic Networking (DetNet)",
              Work in Progress, Internet-Draft, draft-tpmb-detnet-oam-
              framework-01, 30 March 2021,

   [IEEE.CFM] IEEE, "Connectivity Fault Management clause of IEEE
              802.1Q", IEEE 802.1Q, 2013.

              ITU-T, "OAM functions and mechanisms for Ethernet based
              Networks", ITU-T Recommendation G.8013/Y.1731, November

   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
              February 2006, <>.

   [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
              Cost Multipath Treatment in MPLS Networks", BCP 128,
              RFC 4928, DOI 10.17487/RFC4928, June 2007,

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,

   [RFC5885]  Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
              Forwarding Detection (BFD) for the Pseudowire Virtual
              Circuit Connectivity Verification (VCCV)", RFC 5885,
              DOI 10.17487/RFC5885, June 2010,

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

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

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,

   [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, <>.

   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,

   [RFC8972]  Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
              and E. Ruffini, "Simple Two-Way Active Measurement
              Protocol Optional Extensions", RFC 8972,
              DOI 10.17487/RFC8972, January 2021,

   [RFC9037]  Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
              "Deterministic Networking (DetNet) Data Plane: MPLS over
              IEEE 802.1 Time-Sensitive Networking (TSN)", RFC 9037,
              DOI 10.17487/RFC9037, June 2021,

   [RFC9055]  Grossman, E., Ed., Mizrahi, T., and A. Hacker,
              "Deterministic Networking (DetNet) Security
              Considerations", RFC 9055, DOI 10.17487/RFC9055, June
              2021, <>.

Authors' Addresses

   Greg Mirsky


   Mach(Guoyi) Chen