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Deterministic Networking specific MNA
draft-varmir-mpls-detnet-mna-00

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Authors Greg Mirsky , Balazs Varga
Last updated 2024-07-22
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draft-varmir-mpls-detnet-mna-00
MPLS                                                           G. Mirsky
Internet-Draft                                                  B. Varga
Intended status: Standards Track                                Ericsson
Expires: 23 January 2025                                    22 July 2024

                 Deterministic Networking specific MNA
                    draft-varmir-mpls-detnet-mna-00

Abstract

   In IETF the Deterministic Networking (DetNet) Working Group focuses
   on deterministic data paths that can provide bounds on latency, loss,
   and packet delay variation (jitter), and high reliability.  This
   document focuses on the MPLS Data Plane, namely, how to use MNA (MPLS
   Network Action) for DetNet flows, when forwarded over an MPLS
   technology-based 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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 23 January 2025.

Copyright Notice

   Copyright (c) 2024 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.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Terms Used in This Document . . . . . . . . . . . . . . .   3
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  DetNet-specific MNA . . . . . . . . . . . . . . . . . . . . .   3
   4.  DetNet information in NASes . . . . . . . . . . . . . . . . .   4
     4.1.  DetNet-specific NASes . . . . . . . . . . . . . . . . . .   4
     4.2.  Characteristics of DetNet NASes . . . . . . . . . . . . .   5
     4.3.  Examples of DetNet NASes  . . . . . . . . . . . . . . . .   6
     4.4.  Aggregation Example . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   DetNet work group has defined Packet Replication Function (PRF) and
   Packet Elimination Function (PEF) to achieve extreme low packet loss.
   In general, usage of these per packet replication and elimination
   functions may result in out-of-order delivery of frames/packets
   [RFC8655].  This characteristic of PRF/PEF was identified by IETF and
   a Packet Ordering Function (POF) was defined [RFC9550].  The POF
   function is a DetNet service sub-layer function similar to PRF and
   PEF.  All the DetNet service sub-layer functions are usually referred
   as Packet Replication, Elimination and Ordering Functions (PREOF).

   These DetNet service sub-layer related functions require ordering
   information (e.g., sequence number).  IETF DetNet WG has defined how
   sequencing information (i.e., sequence number) travels with DetNet
   packets using the d-CW [RFC8964], when PW (PseudoWire) technology is
   used with an MPLS Data Plane.

   The DetNet forwarding sub-layer related functions focus on ensuring
   the bounded latency requirements and they may intend to use packet
   specific latency information during the forwarding.  No solution was
   defined to add such latency specific information to the PW
   encapsulated DetNet packets.

2.  Terminology

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2.1.  Terms Used in This Document

   This document uses the terminology established in the DetNet
   architecture [RFC8655].  The reader is assumed to be familiar with
   that document and its terminology.

2.2.  Abbreviations

   The following abbreviations are used in this document:

   DetNet        Deterministic Networking

   Flow-ID       Flow Identifier

   MNA           MPLS Network Action

   NAI           Network Action Indicator

   NAS           Network Action Sub-Stack

   LSE           Label Stack Entry

   PEF           Packet Elimination Function

   POF           Packet Ordering Function

   PREOF         Packet Replication, Elimination and Ordering Functions

   PRF           Packet Replication Function

   SeqNum        Sequence Number

2.3.  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.

3.  DetNet-specific MNA

   There are three information elements that may be required during the
   forwarding of DetNet packets:

   1.  Flow identifier (Flow-ID)

   2.  Sequence information (SeqNum)

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   3.  Latency information (LatencyInfo)

   "1" and "2" are used by the DetNet service sub-layer (i.e., by
   PREOF).  "1" and "3" are used by the DetNet forwarding sub-layer to
   ensure the bounded latency for a DetNet packet.

   The usage of a DetNet-specific MNA solution allows using a single
   encapsulation format for all DetNet specific parameters (Flow-ID,
   SeqNum, LatencyInfo) as MNA data.  DetNet-specific MNA allows more
   fine-tuned and scalable handling of the latency bound requirement
   together with service protection natively in MPLS.  The MNA based
   DetNet solution does not require any post-stack-data, contrary to the
   mandatory d-CW used by PW technology.

4.  DetNet information in NASes

4.1.  DetNet-specific NASes

   The MPLS MNA encapsulation is used between DetNet Relay nodes.

   DetNet specific parameters used during forwarding are: (1) Flow-ID,
   (2) SeqNum and (3) LatencyInfo.  For each of them, a specific NAS can
   be defined to carry the related variable in an MPLS MNA network:

   1.  PREOF specific NAS (e.g., SeqNum)

   2.  Latency specific NAS (e.g., LatencyClass)

   3.  Flow specific NAS (i.e., Flow-ID)

   Note: DetNet aggregate flows can be described with the same set of
   parameters.

   DetNet functions use these NASes as follow:

   *  DetNet PREOF requires Flow-ID+SeqNum parameters.  They are used
      only at DetNet Relay nodes implementing the service sub-layer.

   *  DetNet latency bound related functions use Flow-ID+LatencyInfo,
      for selecting proper queuing hop-by-hop along the transmission
      path.  They are used at DetNet Transit nodes implementing the
      forwarding sub-layer.

   Using these NASes in DetNet scenarios results in the following MPLS
   encapsulation format example, that ensures placing all DetNet
   parameters in the NASes:

   *  LSP(s) = F-Label(s): used for describing the forwarding path.

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   *  MNA Sub-Stack Indicator.

   *  NAS-3: (NAI: Flow-ID, Ancillary Data (AD): i.e., Flow-ID).

   *  NAS-2: (NAI: Latency, Ancillary Data (AD): e.g., LatencyClass).

   *  NAS-1: (NAI: SeqNum, Ancillary Data (AD): i.e., SeqNum (16/28
      bits)).

   *  Payload.

   Note: that using PW (S-Label) in the label stack is optional, it is
   not precluded by the method described in this document, and not shown
   in the above example.

4.2.  Characteristics of DetNet NASes

   Characteristics of the DetNet specific NASes are as follows:

   *  Encoding a Network Action: Different Operation Codes are used for
      the above DetNet specific NASes.

   *  Scope is encoded implicitly, all DetNet NAIs (Network Action
      Indicator) have a predefined scope.

      -  All DetNet specific NAI use "Select" mode, so usage of these
         NAIs may be restricted for DetNet-aware nodes if the operator
         intends to do so.

      -  Optional scope for the NAIs:

         o  NAI: Flow-ID can have Hop-by-hop (HBH) scope.

         o  NAI: Latency can have Hop-by-hop (HBH) scope.

         o  NAI: SeqNum can have Ingress-to-Egress (I2E) scope.

   *  Recognition action:

      -  NAI: Flow-ID is used for flow identification, and this NAI must
         be ignored if unrecognized.

      -  NAI: Latency is used by every node along the path those perform
         latency related action (e.g., queuing).  This NAI must be
         ignored if unrecognized.

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      -  NAI: SegNum is used only by the last node on the path defined
         by the F-Label(s) and perform the PREOF action.  If this NAI is
         unrecognized the packet may be dropped.

   *  Encoding of Post-Stack Data: N/A for these NASes.

   Via using the "Select" mode for the DetNet specific NASes, the
   network operation can emulate the MS-PW (Multi-Segment PW) pop-push
   characteristics on the S-Label.  There is no need to define at
   ingress the whole forwarding graph across the MPLS network.
   Furthermore, "Select" mode allows that the payload is an MPLS packet
   using the same label stack (as used by the MNA).

4.3.  Examples of DetNet NASes

   The figures show some possible DetNet specific NAS formats and their
   usage.

   DetNet Latency NAS: Format-B provides enough bits to encode e.g.,
   several LatencyClass-es.  For longer latency related parameters
   (e.g., time stamp) Format C/C+D can be used.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Label (MNA bSPL)         | TC  |S|      TTL      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Opcode    |   Data (Latency Info)   |R|IHS|S| Res |U|  NASL |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 1: An Example of the DetNet Latency Information Encoding
                             Using LSE Format B

   DetNet SeqNum NAS: Depending on the location of the SeqNum parameter
   within the MNA part of the MPLS stack a Format B+C/C/C+D is needed
   (contains 28/16 bits of the SeqNum).  In these formats there are
   unused "Data bits" to carry additional FLAGs related to the SeqNum.

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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Label (MNA bSPL)         | TC  |S|      TTL      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Opcode    |   Data (SeqNum)         |R|IHS|S| Res |U| NASL=1|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Opcode    |   Data (cont.)                |S| Data  | NAL=0 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 2: An Example of the DetNet Sequence Number Encoding Using
                            LSE Formats B and C

   DetNet Flow-ID NAS: Depending on the location of the Flow-ID a Format
   C/B+C is needed (contains 20 bits of the ID).

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Label (MNA bSPL)         | TC  |S|      TTL      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Opcode    |   Data (Flow-ID)        |R|IHS|S| Res |U| NASL=1|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Opcode    |   Data (cont.)                |S|  Data | NAL=0 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 3: An Example of the DetNet LFlow Identifier Encoding
                         Using LSE Formats B and C

   Figure 4 below shows an MNA which contains all the DetNet specific
   NASes.  MNA-6 contains the DetNet Latency parameter being encoded in
   Format-B.  MNA-7 contains the DetNet Flow-ID, a 20 bits Flow-ID is
   encoded in Format C.  MNA-8 contains the DetNet SeqNum in Format C
   with a 16 bits sequence number.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Label (MNA bSPL)         | TC  |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (6)|   Data (Latency Info)   |R|IHS|S| Res |U| NASL=2|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (7)|   Data (Flow-ID)              |S| (FID) | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (8)|   Data (SeqNum)               |S|  0    | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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      Figure 4: An Example of the Combined DetNet Parameters Encoding
                                 Using MNA

4.4.  Aggregation Example

   Figure 5 shows an aggregation example, where multiple DetNet flows
   are aggregated in a single aggregate.  NAS-A part contains the
   aggregate specific DetNet NASes, and NAS-F contains the flow specific
   NASes of the data packet.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Label (MNA bSPL)         | TC  |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (x)| Data (Aggr-Latency-Info)|R|IHS|S| Res |U| NASL=2|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (y)| Data (Aggr-Flow-ID)           |S| (FID) | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (z)| Data (Aggr-SeqNum)            |S|   0   | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Label (MNA bSPL)         | TC  |S|      TTL      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (x)|   Data (Latency Info)   |R|IHS|S| Res |U| NASL=2|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (y)|   Data (Flow-ID)              |S| (FID) | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Opcode (z)|   Data (SeqNum)               |S|  0    | NAL=0 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 5: An Example of the DetNet Aggregate Flow Parameters
                             Encoding Using MNA

   Note1: Opcodes are to be allocated by IANA during the
   standardization.

   Note2: NAS-x denotes the NAS containing the DetNet parameter. "x"
   just a number on the figure to denote that they contain different
   information.

   Note3: Aggregation re-uses the same Options code points for the
   aggregated and specific flows.  The interpretation is based on the
   order of NASes.  During de-aggregation of flows the MNA containing
   the aggregate parameters are removed from the label stack (poped).

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5.  Security Considerations

   This specification desribes the realization of DetNet over MPLS data
   plane using MNA approach.  As a result, it inherits security
   considerations of [RFC8964] and [I-D.ietf-mpls-mna-hdr].

6.  IANA Considerations

   IANA is requested to assign a new Opcode values from the Network
   Action Opcodes Registry as follows:

              +=======+=====================+===============+
              | Value |     Description     | Reference     |
              +=======+=====================+===============+
              | TBA1  |   Flow Identifier   | This document |
              +-------+---------------------+---------------+
              | TBA2  |   Sequence Number   | This document |
              +-------+---------------------+---------------+
              | TBA3  | Latency Information | This document |
              +-------+---------------------+---------------+

                     Table 1: DetNet Parameters in MNA

7.  Acknowledgements

   Authors extend their appreciation to Joel Halpern, Janos Farkas, and
   Ferenc Fejes for their insightful comments and contributions.

8.  Normative References

   [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-
              07, 17 June 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-mpls-mna-hdr-07>.

   [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>.

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   [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>.

   [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>.

   [RFC9550]  Varga, B., Ed., Farkas, J., Kehrer, S., and T. Heer,
              "Deterministic Networking (DetNet): Packet Ordering
              Function", RFC 9550, DOI 10.17487/RFC9550, March 2024,
              <https://www.rfc-editor.org/info/rfc9550>.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com

   Balazs Varga
   Ericsson
   Email: balazs.a.varga@ericsson.com

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