MPLS Sub-Stack Encapsulation for Deterministic Latency Action
draft-sx-detnet-mpls-queue-05

DetNet Working Group                                             X. Song
Internet-Draft                                                  Q. Xiong
Intended status: Standards Track                               ZTE Corp.
Expires: 27 September 2023                                     R. Gandhi
                                                     Cisco Systems, Inc.
                                                           26 March 2023

     MPLS Sub-Stack Encapsulation for Deterministic Latency Action
                     draft-sx-detnet-mpls-queue-05

Abstract

   This document specifies formats and principals for the MPLS header
   which contains the Deterministic Latency Action (DLA) option,
   designed for use over a DetNet network with MPLS data plane.  It
   enables guaranteed latency support and makes scheduling decisions for
   time-sensitive service running on DetNet nodes that operate within a
   constrained network domain.

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 27 September 2023.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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.
   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  DetNet DLA Option . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Queuing delay . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  DLA Option  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  MPLS Extension for DLA  . . . . . . . . . . . . . . . . . . .   5
     4.1.  DetNet MPLS Header for DLA  . . . . . . . . . . . . . . .   5
     4.2.  MPLS Sub-Stack for DLA  . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   As specified in [RFC8655] and [RFC8938], Deterministic Networking
   (DetNet) operates at the IP layer and delivers service with low data
   loss rates and bounded latency guarantee within a network domain.

   As defined in [RFC8964], the DetNet MPLS data plane provides a
   foundation of building blocks to enable PREOF (Packet Replication,
   Elimination and Ordering Functions (PREOF)) functions to DetNet
   service and forwarding sub-layer.  The DetNet service sub-layer
   includes a DetNet Control Word (d-CW), service label (S-Label), an
   aggregation label (A-Label) in special case of S-Label used for
   aggregation.  The DetNet forwarding sub-layer supports one or more
   forwarding labels (F-Labels) used to forward a DetNet flow over MPLS
   domains.  The DetNet forwarding sub-layer provides corresponding
   forwarding assurance with IETF existing functions using resource
   allocations and explicit routes.  But these functions may not be
   enough to provide the deterministic latency (including bounded
   latency, low packet loss and in-order delivery) assurance.  Because

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   latency variation in one DetNet system results in the need for extra
   buffer space in the next-hop DetNet system(s), which in turn
   increases the worst-case per-hop latency.  So standard queuing and
   scheduling algorithms are required to compute and reserve the
   sufficient buffer space for DetNet nodes along the path of DetNet
   flows.

   To support time-sensitive service with ultra-low loss rates and
   deterministic latency, it is required to apply feasible scheduling
   mechanisms to specific applications for deterministic networking.  As
   described in [RFC9320], the end-to-end bounded latency is considered
   as the sum of non-queuing and queuing delay bounds along with the
   queuing mechanisms.  The value for non-queuing delay bounds (which
   consist of packet output delay, link delay, frame preemption delay
   and processing delay) is relative with the physical capability of on-
   used networks and can be considered to be stable.  The unstable
   latency delay bounds are mainly from queuing delay and regulation
   delay.  The regulation delay is mainly from regulation policy.  To
   simplify the question this draft assumes there is no regulation
   policy.  So the question is left to address the selection for queuing
   mechanisms and queuing delay information encapsulation in data plane.

   The queuing mechanisms, as mentioned in [RFC9320] and [RFC8655],
   which include Time Aware Shaping IEEE802.1Qbv, Asynchronous Traffic
   Shaping IEEE802.1Qcr, cyclic-scheduling queuing mechanism proposed in
   IEEE802.1Qch.  There are also discussions on new queuing or
   scheduling mechanisms such as [I-D.peng-6man-deadline-option] and
   [I-D.dang-queuing-with-multiple-cyclic-buffers].  In terms of delay
   guarantee for different applications, to select the right scheduling/
   queuing mechanism applied to a specific application is required.

   Based on the existing DetNet MPLS encapsulations and mechanisms
   [RFC8964], the draft defines the encoding format for Deterministic
   Latency Action (DLA) option carried in MPLS sub-stack.

2.  Conventions

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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2.2.  Terminology

   Refer to [RFC8655], [RFC8964], [I-D.ietf-mpls-mna-hdr] and [RFC9320]
   for the key terms used in this document.

   Deterministic Latency (DL):the bound of network latency and delay
   variation between two DetNet endpoints.  It may includes parameters
   such as bounded latency, bounded delay variation, etc.

   Deterministic Latency Action (DLA): used to indicate deterministic
   latency actions for MPLS Sub-Stack.

3.  DetNet DLA Option

3.1.  Queuing delay

   [RFC8655] provides the architecture for deterministic networking
   (DetNet) which enables the service delivery of DetNet flows with
   extremely low packet loss rates and deterministic latency.  The
   forwarding sub-layer provides corresponding forwarding assurance but
   can not provide the deterministic latency (including bounded latency,
   low packet loss and in-order delivery).  As described at [RFC9320],
   the end-to-end bounded latency for one DetNet flow is the sum of
   delay bound of non-queuing and queuing processing latency.  The delay
   bound for non-queuing processing may include output delay, link
   delay, frame preemption delay, and processing delay, the delay bound
   for queuing processing may include regulator delay, queuing delay.
   It is assumed that the delay of non-queuing processing is fixed or be
   ignorable, the delay of queuing processing is variable.  To realize
   the guarantee of bounded latency service it is important to select
   right queuing methodology applied to specific applications and carry
   necessary queuing delay information for computation of end-to-end
   latency.

3.2.  DLA Option

   The DetNet data plane encapsulation in transport network with MPLS
   data plane is specified in [RFC8964].
   [I-D.xiong-detnet-data-fields-edp] has proposed a commom DetNet data
   fields for enhanced DetNet data plane and defined a DLA option to
   carry queuing-based metadata.This document provides additional
   encapsulation for the DLA in MPLS data plane.

   The DetNet routers in data plane perform MPLS forwarding functions to
   choose a feasible way with sufficient network resources for the
   incoming packets, and makes right selection on the queuing or
   scheduling mechanisms applied for specific DetNet flows to satisfy
   strict QoS criteria in the forwarding output port.  The information

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   for the queuing or scheduling mechanisms are carried in DetNet DLA
   header.  Refer to [I-D.stein-srtsn], considering the time latency
   information are processed per hop so the time latency informations
   (such as deadline time, cycle identify, etc.) of each DetNet node for
   DetNet flows are expected to be carried as a set of lists of LSEs in
   MPLS data plane.

4.  MPLS Extension for DLA

4.1.  DetNet MPLS Header for DLA

   The DetNet MPLS header follows [RFC8964], as showed the below figure
   1, the SP-Lable (SPL) is added to indicate Deterministic Latency
   Action (DLA).

           +---------------------------+
           |       DetNet App-Flow     |
           |       Payload Packet      |
           +---------------------------+--\
           |     DetNet Control Word   |   |
           +---------------------------+   |
           |          S-Label          |   | DetNet Data Plane
           +---------------------------+   | MPLS Encapsulation
           |          SP-Lable         |   |
           +---------------------------+   |
           |          F-Label(s)       |   |
           +---------------------------+--/
           |         Data-Link         |
           +---------------------------+
           |          Physical         |
           +---------------------------+

                        Figure 1: DetNet MPLS Header

   The SP-L (Special Purpose-Label) may be B-SPL [RFC9017], new-SPL,
   extended SPL [RFC9017].  This draft follows the MNA (MPLS Network
   Action) solution specified in [I-D.ietf-mpls-mna-hdr] and
   [I-D.ietf-mpls-mna-fwk], and uses b-SPL to indicate the presence of
   the MPLS Network Action Sub-Stack (NASS).  The value for the bSPL
   value is to be assigned by IANA and follows the assignment in
   [I-D.ietf-mpls-mna-hdr].  The SP-Label field is formatted as below
   figure.

4.2.  MPLS Sub-Stack for DLA

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    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     NASI Label = bSPL (TBA1)          | TC  |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 2: SP-Label Format

   NASI Label:

   A new bSPL value is to be assigned by IANA.  It is used to indicate
   the presence of the MPLS Network Action Sub-Stack (NASS).  The
   assignment for this field value refers to [I-D.ietf-mpls-mna-hdr].

   The MPLS sub-stack encoding format for DLA option is showed as figure
   3.  The format provides DetNet Latency Network Action Indicator (NAI)
   indicates the specific DLA.  Its detailed information is carried in
   Ancillary Data.

    0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Opcode     |                Flag           |S|  Data |  NAL  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|             AD LSE1                       |S|    AD LSE1    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|             AD LSE2                       |S|    AD LSE2    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 ...  ...  ...                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|             AD LSEn                       |S|    AD LSEn    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 3: MPLS LSE Format for DLA

   Opcode (7 bits): This is the first 7-bit value in the Label Field.
   The value is used to indicate DLA and to be assigned by IANA.

   Flag (16 bits): identifies the type of queuing mechanisms used in the
   network.  The queuing type format is defined in section 4.2 of
   [I-D.xiong-detnet-data-fields-edp].

   S (1 bit) : The Bottom of Stack [RFC3032].

   Data (4 bits) : Reserved bits for future use.

   NAL (4 bits): The DLA action length.  It indicates the number of AD
   LSEs in the sub-stack.

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   The first bit in the Label field of the following AD LSEs MUST be set
   to "1".  As specified in [I-D.ietf-mpls-mna-hdr] this is to prevent
   aliasing the label field with other bSPLs on the legacy routers.

   Ancillary Data:

   The 19-bit Label field and 4-bit TC field and 8-bit TTL field (except
   S bit) in the additional LSEs are used to carry the Ancillary Data
   for specific DLA latency information.

   The Ancillary Data LSE1 is expected to carry the latency
   informationDLA option data defined in section 4.2.2 of
   [I-D.xiong-detnet-data-fields-edp] of the edge DetNet node.  Depend
   on specific queuing mechanisms used in the network the DLA field
   length for the latency information for one DetNet node is variable.
   The specific queuing (including cycle, deadline, etc.) data
   encapsulation are described in [I-D.xiong-detnet-data-fields-edp].

   The first AD LSE is expected to carry the latency information for
   edge DetNet node.  When the length of latency information is more
   than 32bits less than 64bits, both AD LSE1 and LSE2 are expected to
   carry the latency information for edge DetNet node.  In this case,
   the DLA option data of next hop is carried in AD LSE3 and LSE4.
   Along the path of DetNet flows the AD LSE(n-1) and LSEn carry the DLA
   option data for the peer edge DetNet node.  With the DetNet flows are
   being forwarded in its output ports the corresponding node latency
   information carried in DLA options are processed hop by hop.

5.  IANA Considerations

   This document describes a new IANA-managed registry to identify
   DetNet application processing.  The registration procedure is "IETF
   Review" [RFC8126].  The registry name is "Opcode" and assigned for
   DLA Indicator, as defined in Table 1.

               +============+=============+===============+
               | Value      | Description | Reference     |
               +============+=============+===============+
               | Unassigned | Opcode      | this document |
               +------------+-------------+---------------+

                          Table 1: DLA Indicator

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6.  Security Considerations

   Security considerations for DetNet are covered in the DetNet
   Architecture RFC8655 and DetNet Security Considerations [RFC9055].
   MPLS security considerations are covered in [RFC8964], [RFC3031],
   [RFC3032].  These security considerations also apply to this
   document.

7.  Acknowledgements

   The authors would like to acknowledge Shaofu Peng for his thorough
   review and very helpful comments.

8.  References

8.1.  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>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.

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   [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, <https://www.rfc-editor.org/info/rfc8964>.

   [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>.

8.2.  Informative References

   [I-D.dang-queuing-with-multiple-cyclic-buffers]
              Liu, B. and J. Dang, "A Queuing Mechanism with Multiple
              Cyclic Buffers", Work in Progress, Internet-Draft, draft-
              dang-queuing-with-multiple-cyclic-buffers-00, 22 February
              2021, <https://datatracker.ietf.org/doc/html/draft-dang-
              queuing-with-multiple-cyclic-buffers-00>.

   [I-D.ietf-mpls-mna-fwk]
              Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
              Network Actions Framework", Work in Progress, Internet-
              Draft, draft-ietf-mpls-mna-fwk-03, 11 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
              mna-fwk-03>.

   [I-D.ietf-mpls-mna-hdr]
              Rajamanickam, J., Gandhi, R., Zigler, R., Song, H., and K.
              Kompella, "MPLS Network Action (MNA) Sub-Stack Solution",
              Work in Progress, Internet-Draft, draft-ietf-mpls-mna-hdr-
              01, 8 March 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-mpls-mna-hdr-01>.

   [I-D.peng-6man-deadline-option]
              Peng, S., Tan, B., and P. Liu, "Deadline Option", Work in
              Progress, Internet-Draft, draft-peng-6man-deadline-option-
              01, 11 July 2022, <https://datatracker.ietf.org/doc/html/
              draft-peng-6man-deadline-option-01>.

   [I-D.stein-srtsn]
              Stein, Y. J., "Segment Routed Time Sensitive Networking",
              Work in Progress, Internet-Draft, draft-stein-srtsn-01, 29
              August 2021, <https://datatracker.ietf.org/doc/html/draft-
              stein-srtsn-01>.

   [I-D.xiong-detnet-data-fields-edp]
              Xiong, Q. and D. Yang, "Data Fields for DetNet Enhanced
              Data Plane", Work in Progress, Internet-Draft, draft-

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              xiong-detnet-data-fields-edp-00, 10 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-xiong-detnet-
              data-fields-edp-00>.

   [RFC8938]  Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane
              Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020,
              <https://www.rfc-editor.org/info/rfc8938>.

   [RFC9055]  Grossman, E., Ed., Mizrahi, T., and A. Hacker,
              "Deterministic Networking (DetNet) Security
              Considerations", RFC 9055, DOI 10.17487/RFC9055, June
              2021, <https://www.rfc-editor.org/info/rfc9055>.

   [RFC9320]  Finn, N., Le Boudec, J.-Y., Mohammadpour, E., Zhang, J.,
              and B. Varga, "Deterministic Networking (DetNet) Bounded
              Latency", RFC 9320, DOI 10.17487/RFC9320, November 2022,
              <https://www.rfc-editor.org/info/rfc9320>.

Authors' Addresses

   Xueyan Song
   ZTE Corp.
   China
   Email: song.xueyan2@zte.com.cn

   Quan Xiong
   ZTE Corp.
   China
   Email: xiong.quan@zte.com.cn

   Rakesh Gandhi
   Cisco Systems, Inc.
   Canada
   Email: rgandhi@cisco.com

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