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Versions: (draft-ietf-detnet-dp-sol) 00

DetNet                                                  J. Korhonen, Ed.
Internet-Draft
Intended status: Standards Track                           B. Varga, Ed.
Expires: January 1, 2019                                        Ericsson
                                                           June 30, 2018


                  DetNet MPLS Data Plane Encapsulation
                    draft-ietf-detnet-dp-sol-mpls-00

Abstract

   This document specifies Deterministic Networking data plane
   encapsulation solutions.  The described data plane solutions is
   applied over an MPLS Packet Switched Networks.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 1, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terms used in this document . . . . . . . . . . . . . . .   4
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Requirements language . . . . . . . . . . . . . . . . . . . .   6
   4.  MPLS DetNet data plane overview . . . . . . . . . . . . . . .   6
     4.1.  DetNet data plane encapsulation requirements  . . . . . .  12
   5.  DetNet encapsulation  . . . . . . . . . . . . . . . . . . . .  13
     5.1.  End-system specific considerations  . . . . . . . . . . .  13
     5.2.  DetNet domain specific considerations . . . . . . . . . .  15
       5.2.1.  DetNet Layer Two Service  . . . . . . . . . . . . . .  15
       5.2.2.  DetNet Routing Service (IP over MPLS) . . . . . . . .  16
     5.3.  DetNet Inter-Working Function (DN-IWF)  . . . . . . . . .  17
       5.3.1.  Networks with multiple technology segments  . . . . .  17
       5.3.2.  DN-IWF related considerations . . . . . . . . . . . .  18
   6.  MPLS-based DetNet data plane solution . . . . . . . . . . . .  19
     6.1.  DetNet over MPLS Encapsulation Components . . . . . . . .  19
     6.2.  MPLS data plane encapsulation . . . . . . . . . . . . . .  21
     6.3.  DetNet control word . . . . . . . . . . . . . . . . . . .  22
     6.4.  Flow Identification . . . . . . . . . . . . . . . . . . .  23
     6.5.  Indication of the DetNet Payload Type . . . . . . . . . .  23
     6.6.  OAM Indication  . . . . . . . . . . . . . . . . . . . . .  24
     6.7.  Flow Aggregation  . . . . . . . . . . . . . . . . . . . .  24
       6.7.1.  Aggregation at the LSP  . . . . . . . . . . . . . . .  25
       6.7.2.  Aggregating DetNet flows as a new DetNet flow . . . .  25
       6.7.3.  Simple Aggregation at the DetNet layer  . . . . . . .  26
     6.8.  Service Layer Considerations  . . . . . . . . . . . . . .  27
       6.8.1.  Edge node processing  . . . . . . . . . . . . . . . .  27
       6.8.2.  Relay node processing . . . . . . . . . . . . . . . .  28
     6.9.  Other DetNet data plane considerations  . . . . . . . . .  29
       6.9.1.  Class of Service  . . . . . . . . . . . . . . . . . .  29
       6.9.2.  Quality of Service  . . . . . . . . . . . . . . . . .  30
       6.9.3.  Cross-DetNet flow resource aggregation  . . . . . . .  31
       6.9.4.  Layer 2 addressing and QoS Considerations . . . . . .  32
       6.9.5.  Time Synchronization  . . . . . . . . . . . . . . . .  32
   7.  Management and control considerations . . . . . . . . . . . .  33
     7.1.  MPLS-based data plane . . . . . . . . . . . . . . . . . .  33
       7.1.1.  S-Label assignment and distribution . . . . . . . . .  33
       7.1.2.  Explicit routes . . . . . . . . . . . . . . . . . . .  33
     7.2.  Packet replication and elimination  . . . . . . . . . . .  34
     7.3.  Congestion protection and latency control . . . . . . . .  35
     7.4.  Bidirectional traffic . . . . . . . . . . . . . . . . . .  35
     7.5.  Flow aggregation control  . . . . . . . . . . . . . . . .  35
   8.  DetNet IP Operation over DetNet MPLS Service  . . . . . . . .  35
   9.  IEEE 802.1 TSN Interconnection over DetNet MPLS Service . . .  36
   10. DetNet MPLS Transport Layer Operation over IEEE 802.1 TSN



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       Sub-Networks  . . . . . . . . . . . . . . . . . . . . . . . .  36
   11. DetNet MPLS Transport Layer Operation over IP DetNet PSNs . .  36
   12. Security considerations . . . . . . . . . . . . . . . . . . .  38
   13. IANA considerations . . . . . . . . . . . . . . . . . . . . .  38
   14. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  39
   15. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  41
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  41
     16.1.  Normative references . . . . . . . . . . . . . . . . . .  41
     16.2.  Informative references . . . . . . . . . . . . . . . . .  44
   Appendix A.  Example of DetNet data plane operation . . . . . . .  45
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  46

1.  Introduction

   Deterministic Networking (DetNet) is a service that can be offered by
   a network to DetNet flows.  DetNet provides these flows with a low
   packet loss rates and assured maximum end-to-end delivery latency.
   General background and concepts of DetNet can be found in
   [I-D.ietf-detnet-architecture].

   This document specifies the DetNet data plane and the on-wire
   encapsulation of DetNet flows over an MPLS-based Packet Switched
   Network (PSN).  The specified encapsulation provides the building
   blocks to enable the DetNet service layer functions and allow flow
   identification as described in the DetNet Architecture.

   The DetNet transport layer functionality that provides congestion
   protection for DetNet flows is assumed to be in place in a DetNet
   node.

   Furthermore, this document also describes how DetNet flows are
   identified, and how a DetNet Relay/Edge/Transit nodes works.  It also
   describes the function and operation of the Packet Replication (PRF)
   Packet Elimination (PEF) and Packet Ordering (POF) functions in the
   MPLS data plane.

   This document does not define the associated control plane functions,
   or Operations, Administration, and Maintenance (OAM).  It also does
   not specify traffic handling capabilities required to deliver
   congestion protection and latency control for DetNet flows at the
   DetNet transport layer.

2.  Terminology








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2.1.  Terms used in this document

   This document uses the terminology established in the DetNet
   architecture [I-D.ietf-detnet-architecture] and the DetNet Data Plane
   Solution Alternatives [I-D.ietf-detnet-dp-alt].

   T-Label       A label used to identify the LSP used to transport 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 layer
                 functions.  An S-Label is also used to identify a
                 DetNet flow at DetNet service layer.

   PEF           A Packet Elimination Function (PEF) eliminates
                 duplicate copies of packets received by an edge or a
                 relay node to prevent excess packets flooding the
                 network, or to prevent duplicate packets being sent out
                 of the DetNet domain.

   PRF           A Packet Replication Function (PRF) replicates DetNet
                 flow packets in an edge or a relay node and forwards
                 them to one or more next hops in the DetNet domain.
                 The number of packet copies sent to each next hop is a
                 DetNet Flow specific parameter at the node doing the
                 replication.

   POF           A Packet Order Function (POF) re-orders packets within
                 a DetNet flow that are received out of order.  This
                 function may be implemented at an edge or a relay node.

   PREOF         Collective name for Packet Replication, Elimination,
                 and Ordering Functions.

   d-CW          A DetNet Control Word (d-CW) is used for sequencing and
                 identifying duplicate packets of a DetNet flow at the
                 DetNet service layer.

2.2.  Abbreviations

   The following abbreviations used in this document:

   AC            Attachment Circuit.

   CE            Customer Edge equipment.

   CoS           Class of Service.



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   CW            Control Word.

   d-CW          DetNet Control Word.

   DetNet        Deterministic Networking.

   DF            DetNet Flow.

   DN-IWF        DetNet Inter-Working Function.

   L2            Layer 2.

   L2VPN         Layer 2 Virtual Private Network.

   L3            Layer 3.

   LSR           Label Switching Router.

   MPLS          Multiprotocol Label Switching.

   MPLS-TE       Multiprotocol Label Switching - Traffic Engineering.

   MPLS-TP       Multiprotocol Label Switching - Transport Profile.

   MS-PW         Multi-Segment PseudoWire (MS-PW).

   NSP           Native Service Processing.

   OAM           Operations, Administration, and Maintenance.

   PE            Provider Edge.

   PEF           Packet Elimination Function.

   PRF           Packet Replication Function.

   PREOF         Packet Replication, Elimination and Ordering Functions.

   POF           Packet Ordering Function.

   PSN           Packet Switched Network.

   PW            PseudoWire.

   QoS           Quality of Service.

   S-PE          Switching Provider Edge.




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   T-PE          Terminating Provider Edge.

   TSN           Time-Sensitive Network.

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.

4.  MPLS DetNet data plane overview

   This document describes how DetNet flows are carried over MPLS
   networks.  The DetNet Architecture, [I-D.ietf-detnet-architecture],
   decomposes the DetNet data plane into two layers: a service layer and
   a transport layer.  The basic approach defined in this document
   supports the DetNet service layer based on existing pseudowire (PW)
   encapsulations and mechanisms, and supports the DetNet transport
   layer based on existing MPLS Traffic Engineering encapsulations and
   mechanisms.  Background on PWs can be found in [RFC3985] and
   [RFC3031].

                          DetNet        MPLS
                            .
                            .
                        +-----------+
                        |  Service  | d-CW, S-Label
                        +-----------+
                        | Transport | T-Label(s)
                        +-----------+
                            .
                            .

              Figure 1: DetNet adaptation to MPLS data plane

   The MPLS DetNet data plane approach defined in this document is shown
   in Figure 1.  The service layer is supported by a DetNet control word
   (d-CW) which conforms to the Generic PW MPLS Control Word (PWMCW)
   defined in [RFC4385].  A d-CW identifying service label (S-Label) is
   also used.  The transport layer is supported by one or labels
   (T-Labels).








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   TSN             Edge          Transit         Edge         TSN
   End System      Node            Node          Node         End System
                   (T-PE)         (LSR)          (T-PE)

   +---------+   +.........+                   +.........+   +---------+
   |  Appl.  |<--:Svc Proxy:--End to End Svc.--:Svc Proxy:-->|  Appl.  |
   +---------+   +---------+                   +---------+   +---------+
   |   TSN   |   |TSN| |Svc|<-- DetNet flow -->: Service :-->|   TSN   |
   +---------+   +---+ +---+    +---------+    +---------+   +---------+
   |Transport|   |Trp| |Trp|    |Transport|    |Trp| |Trp|   |Transport|
   +-------.-+   +--.+ +-.-+    +--.----.-+    +-.-+ +-.-+   +---.-----+
           :  Link  :    /  ,-----.  \   :  Link  :    /  ,-----.  \
           +........+    +-[  Sub  ]-+   +........+    +-[  Sub  ]-+
                           [Network]                     [Network]
                            `-----'                       `-----'

           |<- TSN ->|   |<----- DetNet MPLS ---->|    |<-- TSN --->|

             Figure 2: A TSN over DetNet MPLS Enabled Network

   Figure 2 shows several node types defined in
   [I-D.ietf-detnet-architecture].  DetNet Edge Nodes sit at the
   boundary of a DetNet domain.  They are responsible for mapping non-
   DetNet aware traffic to DetNet services.  They also support the
   imposition and disposition of the required DetNet encapsulation.
   These are functionally similar to pseudowire (PW) Terminating
   Provider Edge (T-PE) nodes which use MPLS-TE LSPs.

   Transit nodes are normal MPLS Label Switching Routers (LSRs).  They
   are generally unaware of the special requirements of DetNet flows,
   although they need to provide traffic engineering services and proper
   QoS to the LSPs associated with DetNet flows to enhance the prospect
   of the LSPs meeting the DetNet service requirements.  Some
   implementations of transit nodes may be DetNet aware, but such nodes
   just support the DetNet transport layer.

   The MPLS LSP may be provided by any MPLS method (provisioned, RSVP-
   TE, MPLS- TP, or MPLS Segment Routing (SR)).













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   IP  DetNet       Relay          Transit       Relay       IP DetNet
   End System       Node            Node         Node        End System
                    (T-PE)          (LSR)        (T-PE)
   +---------+                                               +---------+
   |  Appl.  |<--------------- End to End Service ---------->|  Appl.  |
   +---------+    .....-----+                  +-----.....   +---------+
   | Service |<---: Service |-- DetNet flow ---| Service :-->| Service |
   +---------+    +---------+   +---------+    +---------+   +---------+
   |Transport|    |Trp| |Trp|   |Transport|    |Trp| |Trp|   |Transport|
   +-------.-+    +-.-+ +-.-+   +---.---.-+    +-.-+ +-.-+   +---.-----+
           :  Link  :    /  ,-----.  \  :  Link  :    /  ,-----.  \
           +........+    +-[  Sub  ]-+  +........+    +-[  Sub  ]-+
                           [Network]                    [Network]
                            `-----'                      `-----'

           |<-DN IP->|   |<---- DetNet MPLS ---->|      |<-DN IP->|

                Figure 3: DetNet (DN) IP Over MPLS Network

   Figure 3 and Figure 4, show different cases where relay nodes may be
   used.  Relay nodes are similar to edge nodes in that both are aware
   of the needs of particular DetNet flows and take care to process them
   in accordance with the required performance needs.  They differ in
   that relay nodes sit within a DetNet domain while edge nodes always
   sit at DetNet domain boundaries.  Both node types can enhance the
   reliability of delivery by enabling the replication of packets so
   that multiple copies, possibly over multiple paths are forwarded
   through the DetNet domain.  They also reduce the impact of
   replication by eliminating surplus copies of DetNet packets.  Relay
   nodes may sit the boundary of an MPLS domain when the non-MPLS domain
   is DetNet aware.  Relay nodes are functionally similar to PW S-PEs
   or, when at the edge of an MPLS network, T-PEs [RFC6073].

   Figure 4 illustrates how DetNet can provide services for IEEE
   802.1TSN end systems, CE1 and CE2, over a DetNet enabled network.
   The edge nodes, E1 and E2, insert and remove required DetNet data
   plane encapsulation.  The 'X' in the edge nodes and relay node, R1,
   represent a potential DetNet flow packet replication and elimination
   point.  This conceptually parallels L2VPN services, and could
   leverage existing related solutions as discussed below.











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        TSN    |<------- End to End DetNet Service ------>|  TSN
       Service |         Transit          Transit         | Service
   TSN  (AC)   |        |<-Tnl->|        |<-Tnl->|        |  (AC)  TSN
   End    |    V        V    1  V        V   2   V        V   |    End
   System |    +--------+       +--------+       +--------+   |  System
   +---+  |    |   E1   |=======|   R1   |=======|   E2   |   |   +---+
   |   |--|----|._X_....|..DF1..|.._ _...|..DF3..|...._X_.|---|---|   |
   |CE1|  |    |    \   |       |   X    |       |   /    |   |   |CE2|
   |   |       |     \_.|..DF2..|._/ \_..|..DF4..|._/     |       |   |
   +---+       |        |=======|        |=======|        |       +---+
       ^       +--------+       +--------+       +--------+       ^
       |        Edge Node       Relay Node        Edge Node       |
       |          (T-PE)           (S-PE)          (T-PE)         |
       |                                                          |
       |<--TSN-->     <---- TSN Over DetNet MPLS ---->   <--TSN-->|
       |                                                          |
       |<--- Emulated Time Sensitive Networking (TSN) Service --->|

       DFx = DetNet Flow x



                    Figure 4: IEEE 802.1TSN over DetNet

   Figure 5 illustrates how an end to end MPLS-based DetNet service is
   provided in a more detail.  In this case, the end systems, CE1 and
   CE2, are able to send and receive DetNet flows, and R1 and R2 are
   relay nodes as they sit in the middle of a DetNet network.  For
   example, an end system sends data encapsulated in MPLS.  The 'X' in
   the end systems, and relay nodes represents potential DetNet flow
   packet replication and elimination points.  Here the relay nodes may
   change the underlying transport, for example tunneling MPLS over IP
   Section 11, or simply interconnect network segments.


















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         DetNet                                           DetNet
   MPLS  Service          Transit          Transit       Service MPLS
   DetNet  |             |<-Tnl->|        |<-Tnl->|            | DetNet
   End     |             V   1   V        V   2   V            | End
   System  |    +--------+       +--------+       +--------+   | System
   +---+   |    |   R1   |=======|   R2   |=======|   R3   |   |  +---+
   |  X...DFa...|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|.DFa..|.X |
   |CE1|========|    \   |       |   X    |       |   /    |======|CE2|
   |   |   |    |     \_.|..DF2..|._/ \__.|..DF4..|._/     |   |  |   |
   +---+        |        |=======|        |=======|        |      +---+
       ^        +--------+       +--------+       +--------+      ^
       |        Relay Node       Relay Node       Relay Node      |
       |          (S-PE)           (S-PE)           (S-PE)        |
       |                                                          |
       |<---------------------- DetNet MPLS --------------------->|
       |                                                          |
       |<--------------- End to End DetNet Service -------------->|

                    Figure 5: MPLS-Based Native DetNet

   Figure 6 illustrates how an end to end MPLS-based DetNet service is
   provided where the end systems are not able to send and receive
   DetNet flows.  In this example, the nodes labeled CE1 and CE2 could
   be non-DetNet aware IP routers or hosts.  Note that E1 and E2 are
   edge nodes as they sit boundaries of the DetNet enabled domain.

         IP                                              IP
   Non   Service          Transit          Transit       Service Non
   DetNet                |<-Tnl->|        |<-Tnl->|              DetNet
   End     |             V   1   V        V   2   V            | End
   System  |    +--------+       +--------+       +--------+   | System
   +---+   |    |   E1   |=======|   R2   |=======|   E3   |   |  +---+
   |   |--------|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|------|   |
   |CE1|   |    |    \   |       |   X    |       |   /    |   |  |CE2|
   |   |   |    |     \_.|..DF2..|._/ \__.|..DF4..|._/     |   |  |   |
   +---+        |        |=======|        |=======|        |      +---+
                +--------+       +--------+       +--------+
                ^ Edge Node      Relay Node       Edge Node^
                | (T-PE)           (S-PE)          (T-PE)  |
                |                                          |
        <--IP-->|    <----- IP Over DetNet MPLS ---->      |<--IP-->
                |                                          |
                |<------ End to End DetNet Service ------->|

             Figure 6: MPLS-Based DetNet (non-MPLS End System)

   Figure 7 illustrates how end to end DetNet service is provided where
   the end systems are able to send and receive IP DetNet flows, e.g.,



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   per [I-D.ietf-detnet-dp-sol-ip], and the MPLS nodes optionally
   provide service protection.  In this case R1 and R3 are T-PEs and R2
   is an S-PE and the DetNet service is end-to-end.

         DetNet                                           DetNet
   IP    Service          Transit          Transit       Service IP
   DetNet                |<-Tnl->|        |<-Tnl->|              DetNet
   End     |             V   1   V        V   2   V            | End
   System  |    +--------+       +--------+       +--------+   | System
   +---+   |    |   R1   |=======|   R2   |=======|   R3   |   |  +---+
   |   |--------|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|------|   |
   |CE1|   |    |    \   |       |   X    |       |   /    |   |  |CE2|
   |   |   |    |     \_.|..DF2..|._/ \__.|..DF4..|._/     |   |  |   |
   +---+        |        |=======|        |=======|        |      +---+
       ^        +--------+       +--------+       +--------+      ^
       |        Relay Node       Relay Node       Relay Node      |
       |          (T-PE)           (S-PE)          (T-PE)         |
       |                                                          |
       |<-DN IP->       <------ DetNet MPLS ------>      <-DN IP->|
       |                                                          |
       |<--------------- End to End DetNet Service -------------->|

                 Figure 7: DetNet IP over DetNet (DN) MPLS

   An example MPLS DetNet network fragment and packet flow is
   illustrated in Figure 8.

      1      1.1       1.1      1.2.1    1.2.1      1.2.2
   CE1----EN1--------R1-------R2-------R3--------EN2-----CE2
            \           1.2.1 /                   /
             \1.2     /-----+                   /
              +------R4------------------------+
                        1.2.2

       Figure 8: Example Packet flow in DetNet Enabled MPLS Network

   In Figure 8 the numbers are used to identify the instance of a
   packet.  Packet 1 is the original packet, and packets 1.1, and 1.2
   are two first generation copies of packet 1.  Packet 1.2.1 is a
   second generation copy of packet 1.2 etc.  Note that these numbers
   never appear in the packet, and are not to be confused with sequence
   numbers, labels or any other identifier that appears in the packet.
   They simply indicate the generation number of the original packet so
   that its passage through the network fragment can be identified to
   the reader.

   Customer Equipment CE1 sends a packet into the DetNet enabled MPLS
   network.  This is packet (1).  Edge Node EN1 encapsulates the packet



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   as a DetNet Packet and sends it to Relay node R1 (packet 1.1).  EN1
   makes a copy of the packet (1.2), encapsulates it and sends this copy
   to Relay node R4.

   Note that along the MPLS path from EN1 to R1 there may be zero or
   more LSRs which, for clarity, are not shown.  The same is true for
   any other path between two DetNet entities shown in Figure 8.

   Relay node R4 has been configured to send one copy of the packet to
   Relay Node R2 (packet 1.2.1) and one copy to Edge Node EN2 (packet
   1.2.2).

   R2 receives packet copy 1.2.1 before packet copy 1.1 arrives, and,
   having been configured to perform packet elimination on this DetNet
   flow, forwards packet 1.2.1 to Relay Node R3.  Packet copy 1.1 is of
   no further use and so is discarded by R2.

   Edge Node EN2 receives packet copy 1.2.2 from R4 before it receives
   packet copy 1.2.1 from R2 via relay Node R3.  EN2 therefore strips
   any DetNet encapsulation from packet copy 1.2.2 and forwards the
   packet to CE2.  When EN2 receives the later packet copy 1.2.1 this is
   discarded.

   The above is of course illustrative of many network scenarios that
   can be configured.  Between a pair of relay nodes there may be one or
   more transport nodes that simply forward the DetNet traffic, but
   these are omitted for clarity.

4.1.  DetNet data plane encapsulation requirements

   Two major groups of scenarios can be distinguished which require flow
   identification during transport:

   1.  DetNet function related scenarios:

       *  Congestion protection and latency control: usage of allocated
          resources (queuing, policing, shaping).

       *  Explicit routes: select/apply the flow specific path.

       *  Service protection: recognize DetNet compound and member flows
          for replication an elimination.

   2.  OAM function related scenarios:

       *  troubleshooting (e.g., identify misbehaving flows, etc.)





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       *  recognize flow(s) for analytics (e.g., increase counters,
          etc.)

       *  correlate events with flows (e.g., volume above threshold,
          etc.)

       *  etc.

   The DetNet data plane allows for the aggregation of DetNet flows,
   e.g., via MPLS hierarchical LSPs, to improved scaling.  When DetNet
   flows are aggregated, transit nodes may have limited ability to
   provide service on per-flow DetNet identifiers.  Therefore,
   identifying each individual DetNet flow on a transit node may not be
   achieved in some network scenarios, but DetNet service can still be
   assured in these scenarios through resource allocation and control.

   A node operating on a DetNet flow in the Detnet layer, i.e. a node
   processing a DetNet packet which has the S-label as top of stack uses
   the local context associated with that S-label to determine what
   local operation(s) are applied to that packet.  The S-label has to be
   unique on each edge and relay node, which is achieved by using a
   label taken from the platform label space [RFC3031].

5.  DetNet encapsulation

5.1.  End-system specific considerations

   Data-flows requiring DetNet service are generated and terminated on
   end-systems.  Encapsulation depends on application and its
   preferences.  In a DetNet (or even a TSN) domain the DN (TSN)
   functions use at most two flow parameters, namely Flow-ID and
   Sequence Number.  However, an application may exchange further flow
   related parameters (e.g., time-stamp), which are not considered by DN
   functions.

   Two types of end-systems are distinguished:

   o  L2 (Ethernet) end-system: application directly over L2.

   o  L3 (IP) end-system: application over L3.

   In case of Ethernet end-systems the application data is encapsulated
   directly in L2.  From the DN domain perspective no upper layer
   protocols are visible.  The Data-flow uses only Ethernet tag(s) and
   further flow specific parameters (if needed) are hidden inside the
   protocol data unit (PDU).





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   The IP end-system scenario is different.  Data-flows are encapsulated
   directly in L3 (i.e., IP) and the application may use further upper
   layer protocols (e.g., Real-time Transport Protocol (RTP)).  Many
   valid combinations exist, and it may be application specific how the
   IP header fields are used.  Also, usage of further upper layer
   protocols depends on application requirements (e.g., time-stamp).
   See [I-D.ietf-detnet-dp-sol-ip] more details.

      [Editor's note: IP solution document does not really detail
      anything beyond 6-tuple.]

   As a general rule, DetNet domains MUST be capable of forwarding any
   Data-flows and the DetNet domain MUST NOT mandate the end-system
   encapsulation format.

   Furthermore, no application-level-proxy function is envisioned inside
   the DetNet domain, so end-systems peer with end-systems using the
   same application encapsulation format (see figure below):

   o  L2 end-systems peer with L2 end-systems and

   o  L3 end-systems peer with L3 end-systems.

             +-----+
             |  X  |                               +-----+
             +-----+                               |  X  |
             | Eth |               ________        +-----+
             +-----+     _____    /        \       | Eth |
                    \   /     \__/          \___   +-----+
                     \ /                        \ /
                      0======== tunnel-1 ========0_
                      |                             \
                       \                             |
                       0========= tunnel-2 =========0
                      / \                        __/ \
               +-----+   \__     DetNet domain  /     \
               |  X  |      \         __       /       +-----+
               +-----+       \_______/  \_____/        |  X  |
               |  IP |                                 +-----+
               +-----+                                 |  IP |
                                                       +-----+


                Figure 9: End-systems and the DetNet domain







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5.2.  DetNet domain specific considerations

   From a connection type perspective, three scenarios are
   distinguished:

   1.  Directly attached: end-system is directly connected to an edge
       node.

   2.  Indirectly attached: end-system is behind a (L2-TSN / L3-DetNet)
       sub-network.

   3.  DN integrated: end-system is part of the DetNet domain.

   L3 end-systems may use any of these connection types, however L2 end-
   systems may use only the first two (directly or indirectly attached).
   DetNet domain MUST allow communication between any end-systems of the
   same type (L2-L2, L3-L3), independent of their connection type and
   DetNet capability.  However directly attached and indirectly attached
   end-systems have no knowledge about the DetNet domain and its
   encapsulation format at all.  See Figure 10 for L3 end-system
   scenarios.

                                               ____+----+
                       +----+        _____    /    | ES3|
                       | ES1|____   /     \__/     +----+___
                       +----+    \ /                        \
                                  +                          |
                          ____     \                        _/
            +----+     __/    \     +__    DetNet domain   /
            | ES2|____/  L2/L3 |___/   \         __     __/
            +----+    \_______/         \_______/  \___/



               Figure 10: Connection types of L3 end-systems

5.2.1.  DetNet Layer Two Service

   The simplest DetNet service is to provide tunneling for layer two,
   where the connected hosts are in the same broadcast (BC) domain.
   Forwarding over the DetNet domain is based on L2 (MAC) addresses
   (i.e. dst-MAC), or on received interface [RFC3985].  In both cases
   the L2 headers MUST either be kept, or provision must be made for
   their reconstruction at egress from the DetNet domain.







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                                   +------+
                                   |  X   |
                          +------+ +------+
                          |  X   | |  IP  |
                          +------+ +------+
              End-system  |  L2  | |  L2  |
                    +-----+======+-+======+--+------+
              DetNet tunnel                  | Shim |
                                             +------+
                                             | MPLS |
                                             +------+
                                             |  L2  |
                                             +------+

              Examples:

                                    +------+  +------+
                                    |  X   |  |  X   |
                          +------+  +------+  +------+
                          |  X   |  |  IP  |  |  IP  |
                          +------+  +------+  +------+
                          |  L2  |  |  L2  |  |  L2  |
                    +-----+======+--+======+--+======+-----+
                          | d-CW |  | d-CW |  | d-CW |
                          +------+  +------+  +------+
                          | MPLS |  | MPLS |  | MPLS |
                          +------+  +------+  +------+
                          |  L2  |  |  L2  |  | UDP  |
                          +------+  +------+  +------+
                                              |  IP  |
                                              +------+
                                              |  L2  |
                                              +------+


       Figure 11: Encapsulation format for DetNet Layer Two Service

   As shown in Figure 11 both L2 and L3 end-systems can be served by
   such a DetNet L2 encapsulation service.  This encapsulation service
   may be carried over MPLS natively Section 6.2, of over MPLS over IP
   Section 11.

5.2.2.  DetNet Routing Service (IP over MPLS)

   IP traffic and IP DetNet flows, see [I-D.ietf-detnet-dp-sol-ip], can
   be carried over a DetNet MPLS domain.  In such cases, the IP headers
   are modified per standard router behavior, e.g., TTL handling.




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   Figure 12 shows the encapsulation of an IP flow over MPLS as well as
   when MPLS is carried over an IP PSN, see Section 11.



                               +------+
                               |  X   |
                               +------+
                   End-system  |  IP  |
                         +-----+======+--+------+
                   DetNet tunnel         | Shim |
                                         +------+
                                         | MPLS |
                                         +------+
                                         |  L2  |
                                         +------+

                   Examples:

                               +------+  +------+
                               |  X   |  |  X   |
                               +------+  +------+
                               |  IP  |  |  IP  |
                         +-----+======+--+======+-----+
                               | d-CW |  | d-CW |
                               +------+  +------+
                               | MPLS |  | MPLS |
                               +------+  +------+
                               |  L2  |  | UDP  |
                               +------+  +------+
                                         |  IP  |
                                         +------+
                                         |  L2  |
                                         +------+


   Figure 12: Encapsulation format for DetNet Routing in MPLS PSN for L3
                                end-systems

5.3.  DetNet Inter-Working Function (DN-IWF)

5.3.1.  Networks with multiple technology segments

   There are networking scenarios, where the DetNet domain contains
   multiple technology segments (IP, MPLS, ..) and all those segments
   are under the same administrative control (see Figure 13).
   Furthermore, DetNet nodes may be interconnected via TSN segments.




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   An important aspect of DetNet network design is the placement of
   DetNet functions across the domain.  Designs based on segment-by-
   segment optimization can provide only sub-optimal solutions.  In
   order to achieve global optimized Inter-Working Functions (DN-IWF)
   can be placed at segment edge nodes, which stitch together DetNet
   flows across connected segments.

   DN-IWF may ensure that flow attributes are correlated across segment
   edges.  For example, there are two DetNet functions which require
   Sequence Numbers: (1) PEF: removes duplications from flows and (2)
   POF: ensures in-order-delivery of packet in a flow.  Stitching flows
   together and correlating attributes means for example that
   replication of packets can happen in one segment and elimination of
   duplicates in a different one.

                                      ______
                            ____     /      \__
               ____        /     \__/          \___   ______
   +----+   __/    +======+                       +==+      \     +----+
   |src |__/  Seg1  )     |                       |  \  Seg3 \____| dst|
   +----+  \_______+      \       Segment-2       |   \+_____/    +----+
                    \======+_                    _+===/
                             \         __     __/
                              \_______/  \___/


                                          +------------+
                +---------------E----+    |            |
   +----+       |               |    +----R---+        |          +----+
   |src |-------R           +---+             |        E----------+ dst|
   +----+       |           |                 E--------+          +----+
                +-----------R                 |
                            +-----------------+


      Figure 13: Optimal replication and elimination placement across
                        technology segments example

5.3.2.  DN-IWF related considerations

   The goal of DN-IWF is to (1) match and (2) translate segment specific
   flow attributes.  The DN-IWF ensures that segment specific attributes
   comprise per domain unique attributes for the whole DetNet domain.
   This characteristic can ensure that DetNet functions can be based on
   per domain attributes and not per segment attributes.

   The two DetNet specific attributes have the following
   characteristics:



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   o  Flow-ID: it is same in all packets of a flow

   o  Sequence Number: it is different packet-by-packet

   For the Flow-ID the DN-IWF can implement a static mapping.  The
   situation is more complicated for Sequence Number as it is different
   packet-by-packet, so it may need more sophisticated translation
   unless its format is exactly the same in the two technology segments.
   In this later case the DN-IWF can simple copy the Sequence Number
   field between the tunneling encapsulation of the two technology
   segments.

   In case of three technology segments (IP, MPLS and TSN) three DN-IWF
   functions can be specified.  In the rest of this section the focus is
   on the (1) IP - MPLS network scenario.  Note: the use-cases are out-
   of-scope for (2) TSN - IP, (3) TSN - MPLS.

   Simplest implementation of DN-IWF is provided if the flow attributes
   have the same format.  Such a common denominator of the tunnel
   encapsulation format is the pseudowire encapsulation over both IP and
   MPLS.

                                 +--------+
                                 |        |
                                 | X    X |
                                 |  ____  |
                                 | /    \ |
                                 |        |
                                 |/\/\/\/\|

                                    Oops!
                               404 Not Found


                  Figure 14: FIGURE Placeholder PW over X

   [Editor's note: Where is the text describing how 802.1 TSN Streams
   are mapping to DetNet services/flows. i.e., EVPN+]

6.  MPLS-based DetNet data plane solution

6.1.  DetNet over MPLS Encapsulation Components

   To carry DetNet over MPLS the following is required:

   1.  A method of identifying the MPLS payload type.





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   2.  A method of identifying the DetNet flow group to the processing
       element.

   3.  A method of distinguishing DetNet OAM packets from DetNet data
       packets.

   4.  A method of carrying the DetNet sequence number.

   5.  A suitable LSP to deliver the packet to the egress PE.

   6.  A method of carrying queuing and forwarding indication.

   In this design an MPLS service label (the S-Label), similar to a
   pseudowire (PW) label [RFC3985], is used to identify both the DetNet
   flow identity and the payload MPLS payload type satisfying (1) and
   (2) in the list above.  OAM traffic discrimination happens through
   the use of the Associated Channel method described in [RFC4385].  The
   sequence number is carried in the DetNet Control word which carries
   the Data/OAM discriminator.  The LSP used to transport the DetNet
   packet may be of any type (MPLS-LDP, MPLS-TE, MPLS-TP [RFC5921], or
   MPLS-SR [I-D.ietf-spring-segment-routing-mpls]).  The LSP (T-Label)
   label and/or the S-Label may be used to indicate the queue processing
   as well as the forwarding parameters.

   To simplify implementation and to maximize interoperability two
   sequence number sizes are supported: a 16 bit sequence number and a
   28 bit sequence number.  The 16 bit sequence number is needed to
   support some types of legacy clients.  The 28 bit sequence number is
   used in situations where it is necessary ensure that in high speed
   networks the sequence number space does not wrap whilst packets are
   in flight.  In addition it must be possible to send a packet with a
   zero length sequence number, to support the case where sequence
   numbers are not required by a particular DetNet flow.

   Note that the concept of a zero length sequence number is not to be
   confused with a sequence number of zero.  For example, were the
   sequence number size is 16 bits, the sequence will contain: 65535, 0,
   1.  In this case zero is an ordinary sequence number.  Unlike
   [RFC4448] a sequence number of zero does not indicate that no
   sequence number is in use.  Where sequence numbers are not in use,
   and thus a zero length sequence number is in used, the sequence
   number field in the packet is sent as zero.  The DetNet packet
   forwarder knows which of these cases applies through configuration
   parameters associated with each specific DetNet flow.

   Note that when the network consists only of DetNet enabled nodes with
   no aggregation, Penultimate Hop Popping (PHP) means that the only
   label in the label stack may be the S-label.



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6.2.  MPLS data plane encapsulation

   Figure 15 illustrates a DetNet data plane MPLS encapsulation.  The
   MPLS-based encapsulation of the DetNet flows is a good fit for the
   Layer-2 interconnect deployment cases (see Figure 4).  Furthermore,
   end to end DetNet service i.e., native DetNet deployment (see
   Figure 5) is also possible if DetNet end systems are capable of
   initiating and termination MPLS encapsulated packets.

   The MPLS-based DetNet data plane encapsulation consists of:

   o  DetNet control word (d-CW) containing sequencing information for
      packet replication and duplicate elimination purposes, and the OAM
      indicator.  There MUST be a separate sequence number space for
      each DetNet flow.

   o  DetNet service Label (S-label) that identifies a DetNet flow to
      the peer node that is to process it.  The S-Label is allocated
      from the platform label space [RFC3031].

   o  Zero or more MPLS transport LSP label(s) (T-label) used to direct
      the packet along the label switched path (LSP) to the next peer
      node along the path.  When Penultimate Hop Popping is in use there
      may be no label T-label in the protocol stack on the final hop.

   o  The necessary data-link encapsulation is then applied prior to
      transmission over the physical media.
























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        DetNet MPLS-based encapsulation

      +---------------------------------+
      |                                 |
      |           DetNet Flow           |
      |         Payload  Packet         |
      |                                 |
      +---------------------------------+ <--\
      |       DetNet Control Word       |    |
      +---------------------------------+    +--> DetNet data plane
      |           S-Label               |    |    MPLS encapsulation
      +---------------------------------+ <--/
      |           T-Label(s)            |
      +---------------------------------+
      |           Data-Link             |
      +---------------------------------+
      |           Physical              |
      +---------------------------------+


       Figure 15: Encapsulation of a DetNet flow in an MPLS(-TP) PSN

6.3.  DetNet control word

   A DetNet control word (d-CW) conforms to the Generic PW MPLS Control
   Word (PWMCW) defined in [RFC4385] and is illustrated in Figure 16.
   The upper nibble of the d-CW MUST be set to zero (0).  Two sequence
   number sizes are supported: 16 bits and 28 bits.  The sequence number
   size in use for the d-CW associated with a DetNet flow (S-Label) is
   configured either by a control plane or manually for each DetNet
   flow.  The sequence number is aligned to the right (least significant
   bits) and unused bits MUST be set to zero (0).  Each DetNet flow MUST
   have its own sequence number counter.  The sequence number is
   incremented by one for each new packet.

   As discussed in Section 6, zero is an ordinary sequence number with
   no special meaning.  Also as discussed therein, where no sequence
   number is used by a particular DetNet flow, the sequence number field
   in the d-CW is set to zero.

   The d-CW MUST always be present in a packet.  In a case where the
   sequence number is not used (e.g., for DetNet-t-flows) a zero length
   sequence number is used and the sequence number MUST be set to zero
   (0).







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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0|                Sequence Number                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 16: DetNet Control Word

6.4.  Flow Identification

   DetNet flow identification at a DetNet service layer is realized by
   an S-label.  The S-label is allocated from the platform label space
   [RFC3031] which means that the DetNet flow is correctly identified
   and matched to the flow parameters, including the flow history,
   regardless of which input interface the packet arrives on.  The
   S-label MUST be at the bottom label of the label stack for a DetNet-
   s- or DetNet-st-flow and MUST precede the d-CW.

   The S-label for a specific DetNet flow is unique to that DetNet flow
   on a specific node, but is not required to be identical with the
   S-label for that DetNet flow in any other node within the DetNet
   domain.  Thus the S-label can only be used to identify the DetNet
   flow at the intended receiving node.

6.5.  Indication of the DetNet Payload Type

   The only nodes that needs to know the payload type of a flow are the
   DetNet ingress node and the DetNet egress nodes.  The ingress node
   has to know how to process the packet it receives from the ingress AC
   or IP flow, and the egress edge node has to know how to prepare the
   packet for transmission to the next hop.

   On ingress a DetNet edge node has to classify the packets into those
   that are for transmission as Detnet packets and those that are for
   transmission as "normal" packets at one of more lower priorities.
   The packet type is indicated to the egress edge node through the
   value of the S-label.  Thus, when the egress edge node looks up the
   S-label one of the parameters returned is the packet type which in
   turn tells the egress edge node how to prepare the packet for
   transmission to a next hop.

   The consequence of this approach is that if multiple packet
   encapsulations are processed on a node pair, each encapsulation will
   need its own S-Label.  That is not generally a problems, since it is
   anticipated that only one encapsulation type will be present for each
   DetNet flow.  Of course, if for some reason the multiple
   encapsulations are needed to support a single DetNet service,



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   multiple S-labels will be required for that service.  Note that in
   the unlikely case that Ipv4 and IPv6 will map to the same DetNet
   flow, different S-labels will be needed to differentiate between the
   versions of IP.

6.6.  OAM Indication

   OAM follows the procedures set out in [RFC5085] with the restriction
   that only Virtual Circuit Connectivity Verification (VCCV) type 1 is
   supported.

   As shown in Figure 3 of [RFC5085] when the first nibble of the d-CW
   is 0x0 the payload following the d-CW is normal user data.  However,
   when the first nibble of the d-CW is 0X1, the payload that follows
   the d-DW is an OAM payload with the OAM type indicated by the value
   in the d-CW Channel Type field.

   The reader is referred to [RFC5085] for a more detailed description
   of the Associated Channel mechanism, and to the DetNet work on OAM
   for more information DetNet OAM.

6.7.  Flow Aggregation

   1.  Aggregate at the LSP (Transport)

   2.  Aggregating DetNet flows as a new DetNet flow

   3.  Simple Aggregation at the DetNet layer

   A further method of using SR to perform aggregation is for further
   study.

   The resource control and management aspects of aggregation (including
   the queuing/shaping/ policing implications) will be covered in other
   documents.

   The ability to aggregate individual flows, and their associated
   resource control, into a larger aggregate is an important technique
   for improving scaling of control in the data, management and control
   planes.  The DetNet data plane allows for the aggregation of DetNet
   flows, to improved scaling.  There are three methods of introducing
   flow aggregation:

   The following review comments were received when this section was
   committed to github.

   General comment: We should points to the major issue of aggregation,
   namely the Seq.Num related problem.  The aggregated flows have their



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   own Seq.Num and those are independent.  We should consider to group
   the aggregation techniques as per their impact on what DetNet
   functions they allow on a DetNet flow.  (E.g., aggregation without
   new Aggregate.Seq.Num would prohibit usage of FR, EF and in-order-
   delivery function on the aggregate flow).

   SR based aggregation can be treated as a form of H-LSP aggregation.
   Should we differentiate them?  What are the differences?

   What are the issues when aggregating of different payload types?
   Should we add an editor note on this?

   Simple-aggregation-at-the-detnet-layer: is this not the same as
   H-LSP?  The A-label can be treated just as an additional T-label.

   End of review comment.

6.7.1.  Aggregation at the LSP

   DetNet flows transported via MPLS can leverage MPLS-TE?s existing
   support for hierarchical LSPs (H-LSPs), see [RFC4206].  H-LSPs are
   typically used to aggregate control and resources, they may also be
   used to provide OAM or protection for the aggregated LSPs.  Arbitrary
   levels of aggregation naturally falls out of the definition for
   hierarchy and the MPLS label stack [RFC3032].  DetNet nodes which
   support aggregation (LSP hierarchy) map one or more LSPs (labels)
   into and from an H-LSP.  Both carried LSPs and H-LSPs may or may not
   use the TC field, i.e., L-LSPs or E-LSPs.  Such nodes will need to
   ensure that traffic from aggregated LSPs are placed (shaped/policed/
   enqueued) onto the H-LSPs in a fashion that ensures the required
   DetNet service is preserved.

   Additional details of the traffic control capabilities needed at a
   DetNet-aware node may be covered in the new service descriptions
   mentioned above or in separate future documents.  Management and
   control plane mechanisms will also need to ensure that the service
   required on the aggregate flow (H-LSP or DSCP) are provided, which
   may include the discarding or remarking mentioned in the previous
   sections.

6.7.2.  Aggregating DetNet flows as a new DetNet flow

   An aggregate can be built by layering DetNet flows as shown below:








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   +---------------------------------+
   |                                 |
   |           DetNet Flow           |
   |         Payload  Packet         |
   |                                 |
   +---------------------------------+ <--\
   |       DetNet Control Word       |    |
   +=================================+    |
   |            S-Label              |    |
   +---------------------------------+    +----DetNet data plane
   |       DetNet Control Word       |    |    MPLS encapsulation
   +=================================+    |
   |            A-Label              |    |
   +---------------------------------+ <--/
   |           T-Label(s)            |
   +---------------------------------+
   |           Data-Link             |
   +---------------------------------+
   |           Physical              |
   +---------------------------------+

   Both the Aggregation (A) label and the S-label have their MPLS S bit
   set indicating bottom of stack, and the d-CW allows the PREOF to
   work.

   It is a property of the A-label that what follows is d-CW followed by
   an S-label.  A relay node processing the A-label would not know the
   underlying payload type.  This would only be known to a node that was
   a peer of the node imposing the S-label.  However there is no real
   need for it to know the payload type during aggregation processing.

6.7.3.  Simple Aggregation at the DetNet layer

   Another approach would be not to include a d-CW for the aggregated
   flow.  This would be functionally similar to aggregation at the
   transport layer using H-LSPs, but would confine knowledge of the
   aggregation to the DetNet layer.  Such an approach shares the
   disadvantage that PREOF operations would not be possible.  OAM
   operation in this mode is for further study.












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    +---------------------------------+
    |                                 |
    |           DetNet Flow           |
    |         Payload  Packet         |
    |                                 |
    +---------------------------------+ <--\
    |       DetNet Control Word       |    |
    +=================================+    |
    |            S-Label              |    +----DetNet data plane
    +---------------------------------+    |    MPLS encapsulation
    |            A-Label              |    |
    +---------------------------------+ <--/
    |           T-Label(s)            |
    +---------------------------------+
    |           Data-Link             |
    +---------------------------------+
    |           Physical              |
    +---------------------------------+

6.8.  Service Layer Considerations

   The edge and relay node internal procedures related to PREOF are
   implementation specific.  The order of a packet elimination or
   replication is out of scope in this specification.  However, care
   should be taken that the replication function does not actually
   loopback packets as "replicas".  Looped back packets include
   artificial delay when the node that originally initiated the packet
   receives it again.  Also, looped back packets may make the network
   condition to look healthier than it actually is (in some cases link
   failures are not reflected properly because looped back packets make
   the situation appear better than it actually is).

   It is important that the DetNet layer is configured such that a
   DetNet node never receives its own replicated packets.  If it were to
   receive such packets the replication function would make the loop
   more destructive of bandwidth than a conventional unicast loop.
   Ultimately the TTL in the S-Label will cause the packet to die during
   a transient, but given the sensitivity of applications to packet
   latency the impact on the DetNet application would be severe.

6.8.1.  Edge node processing

   An edge node is resposable for matching ingress packets to the
   service they require and encapsulating them accordingly.An edge node
   may participate in the packet replication and duplication
   elimination.





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   The DetNet-aware forwarder selects the egress DetNet member flow
   segment based on the flow identification.  The mapping of ingress
   DetNet member flow segment to egress DetNet member flow segment may
   be statically or dynamically configured.  Additionally the DetNet-
   aware forwarder does duplicate frame elimination based on the flow
   identification and the sequence number combination.  The packet
   replication is also done within the DetNet-aware forwarder.  During
   elimination and the replication process the sequence number of the
   DetNet member flow MUST be preserved and copied to the egress DetNet
   member flow.

   The internal design of a relay node is out of scope of this document.
   However the reader's attention is drawn to the need to make any PREOF
   state available to the packet processor(s) dealing with packets to
   which the PREOF functions must be applied, and to maintain that state
   is such as way that it is available to the packet processor operation
   on the next packet in the DetNet flow (which may be a duplicate, a
   late packet, or the next packet in sequence.

   [Editor's note: I think the rest of this section belongs in a new
   "802.1 TSN (island Interconnect) over MPLS DetNet" section.]

   This may be done in the DetNet layer, or where the native service
   processing (NSP) [RFC3985] is IEEE 802.1CB [IEEE8021CB] capable, the
   packet replication and duplicate elimination MAY entirely be done in
   the NSP, bypassing the DetNet flow encapsulation and logic entirely.
   This enables operating over unmodified implementations and
   deployments.  The NSP approach works only between edge nodes and
   cannot make use of relay nodes.

   The NSP approach is useful end to end tunnel and for for "island
   interconnect" scenarios.  However, when there is a need to do PREOF
   in a middle of the network, such plain edge to edge operation is not
   sufficient.

   The extended forwarder MAY copy the sequencing information from the
   native DetNet packet into the DetNet sequence number field and vice
   versa.  If there is no existing sequencing information available in
   the native packet or the forwarder chose not to copy it from the
   native packet, then the extended forwarder MUST maintain a sequence
   number counter for each DetNet flow (indexed by the DetNet flow
   identification).

6.8.2.  Relay node processing

   A DetNet Relay node operates in the DetNet transport layer . This
   processing is done within an extended forwarder function.  Whether an
   ingress DetNet member flow receives DetNet specific processing



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   depends on how the forwarding is programmed.  Some relay nodes may be
   DetNet service aware, while others may be unmodified LSRs that only
   understand how to swicth MPLS-TE LSPs.

   It is also possible to treat the relay node as a transit node, see
   Section 6.9.3.  Again, this is entirely up to how the forwarding has
   been programmed.

6.9.  Other DetNet data plane considerations

6.9.1.  Class of Service

   [Editor's note: this section needs to updated to discuss how DetNet
   service is mapped to E- and L-LSPs.  Perhaps this gets merged with
   the aggregation section or dropped?]

   Class and quality of service, i.e., CoS and QoS, are terms that are
   often used interchangeably and confused with each other.  In the
   context of DetNet, CoS is used to refer to mechanisms that provide
   traffic forwarding treatment based on aggregate group basis and QoS
   is used to refer to mechanisms that provide traffic forwarding
   treatment based on a specific DetNet flow basis.  Examples of
   existing network level CoS mechanisms include DiffServ which is
   enabled by IP header differentiated services code point (DSCP) field
   [RFC2474] and MPLS label traffic class field [RFC5462], and at Layer-
   2, by IEEE 802.1p priority code point (PCP).

   CoS for DetNet flows carried in PWs and MPLS is provided using the
   existing MPLS Differentiated Services (DiffServ) architecture
   [RFC3270].  Both E-LSP and L-LSP MPLS DiffServ modes MAY be used to
   support DetNet flows.  The Traffic Class field (formerly the EXP
   field) of an MPLS label follows the definition of [RFC5462] and
   [RFC3270].  The Uniform, Pipe, and Short Pipe DiffServ tunneling and
   TTL processing models are described in [RFC3270] and [RFC3443] and
   MAY be used for MPLS LSPs supporting DetNet flows.  MPLS ECN MAY also
   be used as defined in ECN [RFC5129] and updated by [RFC5462].

   CoS for DetNet flows carried in IPv6 is provided using the standard
   differentiated services code point (DSCP) field [RFC2474] and related
   mechanisms.  The 2-bit explicit congestion notification (ECN)
   [RFC3168] field MAY also be used.

   One additional consideration for DetNet nodes which support CoS
   services is that they MUST ensure that the CoS service classes do not
   impact the congestion protection and latency control mechanisms used
   to provide DetNet QoS.  This requirement is similar to requirement
   for MPLS LSRs to that CoS LSPs do not impact the resources allocated
   to TE LSPs via [RFC3473].



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6.9.2.  Quality of Service

   Quality of Service (QoS) mechanisms for flow specific traffic
   treatment typically includes a guarantee/agreement for the service,
   and allocation of resources to support the service.  Example QoS
   mechanisms include discrete resource allocation, admission control,
   flow identification and isolation, and sometimes path control,
   traffic protection, shaping, policing and remarking.  Example
   protocols that support QoS control include Resource ReSerVation
   Protocol (RSVP) [RFC2205] (RSVP) and RSVP-TE [RFC3209] and [RFC3473].
   The existing MPLS mechanisms defined to support CoS [RFC3270] can
   also be used to reserve resources for specific traffic classes.

   In addition to explicit routes, and packet replication and
   elimination, described in Section 6 above, DetNet provides zero
   congestion loss and bounded latency and jitter.  As described in
   [I-D.ietf-detnet-architecture], there are different mechanisms that
   maybe used separately or in combination to deliver a zero congestion
   loss service.  These mechanisms are provided by the either the MPLS
   or IP layers, and may be combined with the mechanisms defined by the
   underlying network layer such as 802.1TSN.

   A baseline set of QoS capabilities for DetNet flows carried in PWs
   and MPLS can provided by MPLS with Traffic Engineering (MPLS-TE)
   [RFC3209] and [RFC3473].  TE LSPs can also support explicit routes
   (path pinning).  Current service definitions for packet TE LSPs can
   be found in "Specification of the Controlled Load Quality of
   Service", [RFC2211], "Specification of Guaranteed Quality of
   Service", [RFC2212], and "Ethernet Traffic Parameters", [RFC6003].
   Additional service definitions are expected in future documents to
   support the full range of DetNet services.  In all cases, the
   existing label-based marking mechanisms defined for TE-LSPs and even
   E-LSPs are use to support the identification of flows requiring
   DetNet QoS.

   Packets that are marked with a DetNet Class of Service value, but
   that have not been the subject of a completed reservation, can
   disrupt the QoS offered to properly reserved DetNet flows by using
   resources allocated to the reserved flows.  Therefore, the network
   nodes of a DetNet network:

   o  MUST defend the DetNet QoS by discarding or remarking (to a non-
      DetNet CoS) packets received that are not the subject of a
      completed reservation.

   o  MUST NOT use a DetNet reserved resource, e.g. a queue or shaper
      reserved for DetNet flows, for any packet that does not carry a
      DetNet Class of Service marker.



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6.9.3.  Cross-DetNet flow resource aggregation

   [Editor's NOTE: keep and extend this section.]

   The ability to aggregate individual flows, and their associated
   resource control, into a larger aggregate is an important technique
   for improving scaling of control in the data, management and control
   planes.  This document identifies the traffic identification related
   aspects of aggregation of DetNet flows.  The resource control and
   management aspects of aggregation (including the queuing/shaping/
   policing implications) will be covered in other documents.  The data
   plane implications of aggregation are independent for PW/MPLS and IP
   encapsulated DetNet flows.

   DetNet flows transported via MPLS can leverage MPLS-TE's existing
   support for hierarchical LSPs (H-LSPs), see [RFC4206].  H-LSPs are
   typically used to aggregate control and resources, they may also be
   used to provide OAM or protection for the aggregated LSPs.  Arbitrary
   levels of aggregation naturally falls out of the definition for
   hierarchy and the MPLS label stack [RFC3032].  DetNet nodes which
   support aggregation (LSP hierarchy) map one or more LSPs (labels)
   into and from an H-LSP.  Both carried LSPs and H-LSPs may or may not
   use the TC field, i.e., L-LSPs or E-LSPs.  Such nodes will need to
   ensure that traffic from aggregated LSPs are placed (shaped/policed/
   enqueued) onto the H-LSPs in a fashion that ensures the required
   DetNet service is preserved.

   DetNet flows transported via IP have more limited aggregation
   options, due to the available traffic flow identification fields of
   the IP solution.  One available approach is to manage the resources
   associated with a DSCP identified traffic class and to map (remark)
   individually controlled DetNet flows onto that traffic class.  This
   approach also requires that nodes support aggregation ensure that
   traffic from aggregated LSPs are placed (shaped/policed/enqueued) in
   a fashion that ensures the required DetNet service is preserved.

   In both the MPLS and IP cases, additional details of the traffic
   control capabilities needed at a DetNet-aware node may be covered in
   the new service descriptions mentioned above or in separate future
   documents.  Management and control plane mechanisms will also need to
   ensure that the service required on the aggregate flow (H-LSP or
   DSCP) are provided, which may include the discarding or remarking
   mentioned in the previous sections.








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6.9.4.  Layer 2 addressing and QoS Considerations

   [Editor's NOTE: review and simplify this section.]

   The Time-Sensitive Networking (TSN) Task Group of the IEEE 802.1
   Working Group have defined (and are defining) a number of amendments
   to IEEE 802.1Q [IEEE8021Q] that provide zero congestion loss and
   bounded latency in bridged networks.  IEEE 802.1CB [IEEE8021CB]
   defines packet replication and elimination functions that should
   prove both compatible with and useful to, DetNet networks.

   As is the case for DetNet, a Layer 2 network node such as a bridge
   may need to identify the specific DetNet flow to which a packet
   belongs in order to provide the TSN/DetNet QoS for that packet.  It
   also will likely need a CoS marking, such as the priority field of an
   IEEE Std 802.1Q VLAN tag, to give the packet proper service.

   Although the flow identification methods described in IEEE 802.1CB
   [IEEE8021CB] are flexible, and in fact, include IP 5-tuple
   identification methods, the baseline TSN standards assume that every
   Ethernet frame belonging to a TSN stream (i.e.  DetNet flow) carries
   a multicast destination MAC address that is unique to that flow
   within the bridged network over which it is carried.  Furthermore,
   IEEE 802.1CB [IEEE8021CB] describes three methods by which a packet
   sequence number can be encoded in an Ethernet frame.

   Ensuring that the proper Ethernet VLAN tag priority and destination
   MAC address are used on a DetNet/TSN packet may require further
   clarification of the customary L2/L3 transformations carried out by
   routers and edge label switches.  Edge nodes may also have to move
   sequence number fields among Layer 2, PW, and IPv6 encapsulations.

6.9.5.  Time Synchronization

   [Editor's Note: A detailed discussion of time synchronization is
   outside the scope of this document, and the production of a
   specialist text discussing this topic is encouraged.  This section
   will be updated/removed if such a document is available before
   publication of this text.]

   Time synchronization is important both from the perspective of
   operating the DetNet network itself and from the perspective of
   transferring time across the network between client applications.
   Some clients may be able to use the DetNet as their provider of time
   and frequency, others may require the DetNet to transfer time between
   a client clock source and a client clock user.





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   The reader's attention is drawn to [RFC8169] which describes a method
   of recording the packet queuing time in an MPLS LSR on a packet by
   per packet basis and forwarding this information to the egress edge
   system.  This allows compensation for any variable packet queuing
   delay to be applied at the packet receiver.  The mechanism described
   in [RFC8169] may have wider application than basic time transfer in a
   DetNet.

   A more detailed discussion of time synchronization is outside the
   scope of this document.

7.  Management and control considerations

   [Editor's note: This section needs to be different for MPLS and IP
   solutions.  Most solutions are technology dependant.  Currently most
   text in this section is just a draft and may have bits that are
   already moved to other places/documents.]

   While management plane and control planes are traditionally
   considered separately, from the Data Plane perspective there is no
   practical difference based on the origin of flow provisioning
   information.  This document therefore does not distinguish between
   information provided by a control plane protocol, e.g., RSVP-TE
   [RFC3209] and [RFC3473], or by a network management mechanisms, e.g.,
   RestConf [RFC8040] and YANG [RFC7950].

   [Editor's note: This section is a work in progress.  discuss here
   what kind of enhancements are needed for DetNet and specifically for
   PREOF and DetNet zero congest loss and latency control.  Need to
   cover both traffic control (queuing) and connection control (control
   plane).]

7.1.  MPLS-based data plane

7.1.1.  S-Label assignment and distribution

   [Editor's note: Outdated and needs more work.]

   The DetNet S-Label distribution follows the same mechanisms specified
   for XYZ . The details of the control plane protocol solution required
   for the label distribution and the management of the label number
   space are out of scope of this document.

7.1.2.  Explicit routes

   It is necessary to consider explicit routes both at the DetNet layer
   and in the MPLS layer.  In the DetNet layer the explicit route
   consists of the set of Relay Nodes that the DetNet flow must



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   traverse.  In the MPLS layer the explicit route consists of the set
   of LSRs, links, and possibly link bundle members and queues that the
   DetNet packets of a flow must traverse between nodes in the DetNet
   layer (i.e. between a specific Edge Node and the next hop Relay Node,
   between specific Relay Nodes, and between a specific Relay node and
   the egress Edge Node.  This detailed steering is needed to ensure
   that packets are routed through the resources that have been reserved
   for them, and hence provide the DetNet application with the required
   performance.

   Whether configuring, calculating and instantiating this is a multi-
   stage process, or a single stage process is out of scope of this
   document.

   The one method of explicitly setting up the explicit path at the
   DetNet layer is through the use of the management controller.

   [Editor's note: a method of setting up a graph through the DetNet
   Nodes using the IGP has been proposed.  A reference is needed to
   e.g., RFC 7813 IS-IS Path Control and Reservation.]

   There are a number of approaches that can be taken to provide
   explicit routes/paths in the MPLS layer:

   o  The path can be explicitly set up by the management controller
      calculating the path and explicitly configuring each node along
      that path.

   o  The LSP can be set up using RSVP-TE.  Such an approach confines
      the packet to the explicit path.

   o  The path can be implemented using segment routing.

   Where the DetNet traffic is carried over IP Section 11 explicit paths
   may need to be provided in the IP layer.  This is for further study.

7.2.  Packet replication and elimination

   [Editor's note: Outdated and at the functional level technology
   independent.. but needs more work.]

   The control plane protocol solution required for managing the PREOF
   processing is outside the scope of this document.








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7.3.  Congestion protection and latency control

   [Editor's note: TBD]

7.4.  Bidirectional traffic

   [Editor's NOTE: this section needs to be updated to have its scope
   limited to management and control.]

   Some DetNet applications generate bidirectional traffic.  Using MPLS
   definitions [RFC5654] there are associated bidirectional flows, and
   co-routed bidirectional flows.  MPLS defines a point-to-point
   associated bidirectional LSP as consisting of two unidirectional
   point-to-point LSPs, one from A to B and the other from B to A, which
   are regarded as providing a single logical bidirectional transport
   path.  This would be analogous of standard IP routing, or PWs running
   over two reciprocal unidirection LSPs.  MPLS defines a point-to-point
   co-routed bidirectional LSP as an associated bidirectional LSP which
   satisfies the additional constraint that its two unidirectional
   component LSPs follow the same path (in terms of both nodes and
   links) in both directions.  An important property of co-routed
   bidirectional LSPs is that their unidirectional component LSPs share
   fate.  In both types of bidirectional LSPs, resource allocations may
   differ in each direction.  The concepts of associated bidirectional
   flows and co-routed bidirectional flows can be applied to DetNet
   flows as well whether IPv6 or MPLS is used.

   While the IPv6 and MPLS data planes must support bidirectional DetNet
   flows, there are no special bidirectional features with respect to
   the data plane other than need for the two directions take the same
   paths.  Fate sharing and associated vs co-routed bidirectional flows
   can be managed at the control level.  Note, that there is no stated
   requirement for bidirectional DetNet flows to be supported using the
   same IPv6 Flow Labels or MPLS Labels in each direction.  Control
   mechanisms will need to support such bidirectional flows for both
   IPv6 and MPLS, but such mechanisms are out of scope of this document.
   An example control plane solution for MPLS can be found in [RFC7551].

7.5.  Flow aggregation control

   [TBD]

8.  DetNet IP Operation over DetNet MPLS Service

   [Editor's note: this is a place holder section.  A standalone section
   on operation of IP flows over DetNet MPLS data plane.  Includes
   RFC2119 Language.]




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9.  IEEE 802.1 TSN Interconnection over DetNet MPLS Service

   [Editor's note: this is a place holder section.  A standalone section
   on TSN "island" interconnect over DetNet".  Includes RFC2119
   Language.]

10.  DetNet MPLS Transport Layer Operation over IEEE 802.1 TSN Sub-
     Networks

   [Editor's note: this is a place holder section.  A standalone section
   on MPLS over IEEE 802.1 TSN.  Includes RFC2119 Language.]

11.  DetNet MPLS Transport Layer Operation over IP DetNet PSNs

   This section specifies the DetNet encapsulation over an IP transport
   network.  The approach is modeled on the operation of MPLS and
   PseudoWires (PW) over an IP Packet Switched Network (PSN)
   [RFC3985][RFC4385][RFC7510].  It is also based on the MPLS data plane
   encapsulation described in Section 6.2.

   To carry DetNet with full functionality at the DetNet layer over an
   IP transport network, the following components are required (these
   are a subset of the requirements for MPLS encapsulation listed in
   Section 6.1):

   1.  A method of identifying the DetNet flow group to the processing
       element.

   2.  A method of carrying the DetNet sequence number.

   3.  A method of distinguishing DetNet OAM packets from DetNet data
       packets.

   4.  A method of carrying queuing and forwarding indication.

   These requirements are satisfied by the DetNet over MPLS
   Encapsulation described in Section 6.2.

   To simplify operations and implementations, rather than inventing a
   new encapsulation, the IP encapsulation takes advantage of the MPLS
   encapsulation.  By using the specification of MPLS over UDP and IP in
   [RFC7510], the T-Label(s) shown in Figure 15 in Section 6.2 can be
   replaced by UDP and IP, resulting in the following encapsulation:








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      +---------------------------------+
      |                                 |
      |           DetNet Flow           |
      |         Payload  Packet         |
      |                                 |
      +---------------------------------+ <--\
      |       DetNet Control Word       |    |
      +---------------------------------+    +--> DetNet data plane
      |             S-Label             |    |    MPLS encapsulation
      +---------------------------------+ <--/
      |           UDP Header            |
      +---------------------------------+
      |           IP Header             |
      +---------------------------------+
      |           Data-Link             |
      +---------------------------------+
      |           Physical              |
      +---------------------------------+


                   Figure 17: IP Encapsulation of DetNet

   Where the UDP header is used as defined in Section 3 of [RFC7510].

   As in Section 6.2, the S-Label is used to identify a DetNet flow to
   the peer node that processes it, in this case the node addressed by
   the IP Header in Figure 17.  The S-Label is allocated from the
   receiving node?s platform label space [RFC3031].

   In ingress Edge Nodes, the encapsulation in Figure 17 will be imposed
   on Detnet Flow Payload Packets as received from DetNet End Systems,
   and the encapsulation will be removed in egress Edge Nodes as they
   transmit the Payload Packets to the End Systems.

   Note that this encapsulation works equally well with IPv4 and IPv6.

   This encapsulation can also be used in conjunction with segment
   routing as specified in [I-D.ietf-spring-segment-routing-mpls].  In
   this case, the T-Label(s) in Figure 17 should be retained, and at
   each hop, the top T-label is popped and mapped to a corresponding
   UDP/IP tunnel, resulting in the following encapsulation:










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       +---------------------------------+
       |                                 |
       |           DetNet Flow           |
       |         Payload  Packet         |
       |                                 |
       +---------------------------------+ <--\
       |       DetNet Control Word       |    |
       +---------------------------------+    +--> DetNet data plane
       |           S-Label               |    |    MPLS encapsulation
       +---------------------------------+ <--/
       |           T-Label(s)            |
       +---------------------------------+
       |           UDP Header            |
       +---------------------------------+
       |           IP Header             |
       +---------------------------------+
       |           Data-Link             |
       +---------------------------------+
       |           Physical              |
       +---------------------------------+


            Figure 18: IP Encapsulation of DetNet with MPLS-SR

   Again, the UDP header is used as defined in Section 3 of [RFC7510].

   Note that if required in both the case of IP Encapsulation of DetNet
   Figure 17, and of IP Encapsulation of DetNet with MPLS-SR Figure 18,
   it is possible to omit the UDP header if required.  Operation of MPLS
   directly over IP is described in [RFC4023].  In this case DetNet
   Service can be provided on a per IP flow basis as described in
   [I-D.ietf-detnet-dp-sol-ip].

12.  Security considerations

   The security considerations of DetNet in general are discussed in
   [I-D.ietf-detnet-architecture] and [I-D.sdt-detnet-security].  Other
   security considerations will be added in a future version of this
   draft.

13.  IANA considerations

   This document makes no IANA requests.








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14.  Contributors

   RFC7322 limits the number of authors listed on the front page of a
   draft to a maximum of 5, far fewer than the 20 individuals below who
   made important contributions to this draft.  The editor wishes to
   thank and acknowledge each of the following authors for contributing
   text to this draft.  See also Section 15.












































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      Loa Andersson
      Huawei
      Email: loa@pi.nu

      Yuanlong Jiang
      Huawei
      Email: jiangyuanlong@huawei.com

      Norman Finn
      Huawei
      3101 Rio Way
      Spring Valley, CA  91977
      USA
      Email: norman.finn@mail01.huawei.com

      Janos Farkas
      Ericsson
      Magyar Tudosok krt. 11.
      Budapest  1117
      Hungary
      Email: janos.farkas@ericsson.com

      Carlos J. Bernardos
      Universidad Carlos III de Madrid
      Av. Universidad, 30
      Leganes, Madrid  28911
      Spain
      Email: cjbc@it.uc3m.es

      Tal Mizrahi
      Marvell
      6 Hamada st.
      Yokneam
      Israel
      Email: talmi@marvell.com

      Lou Berger
      LabN Consulting, L.L.C.
      Email: lberger@labn.net

      Stewart Bryant
      Huawei Technologies
      Email: stewart.bryant@gmail.com

      Mach Chen
      Huawei Technologies
      Email: mach.chen@huawei.com




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15.  Acknowledgements

   The author(s) ACK and NACK.

   The following people were part of the DetNet Data Plane Solution
   Design Team:

      Jouni Korhonen

      Janos Farkas

      Norman Finn

      Balazs Varga

      Loa Andersson

      Tal Mizrahi

      David Mozes

      Yuanlong Jiang

      Carlos J.  Bernardos

   The DetNet chairs serving during the DetNet Data Plane Solution
   Design Team:

      Lou Berger

      Pat Thaler

   Thanks for Stewart Bryant for his extensive review of the previous
   versions of the document.

16.  References

16.1.  Normative references

   [I-D.ietf-spring-segment-routing-mpls]
              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-14
              (work in progress), June 2018.







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   [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>.

   [RFC2211]  Wroclawski, J., "Specification of the Controlled-Load
              Network Element Service", RFC 2211, DOI 10.17487/RFC2211,
              September 1997, <https://www.rfc-editor.org/info/rfc2211>.

   [RFC2212]  Shenker, S., Partridge, C., and R. Guerin, "Specification
              of Guaranteed Quality of Service", RFC 2212,
              DOI 10.17487/RFC2212, September 1997,
              <https://www.rfc-editor.org/info/rfc2212>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [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>.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,
              <https://www.rfc-editor.org/info/rfc3168>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC3270]  Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
              P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
              Protocol Label Switching (MPLS) Support of Differentiated
              Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
              <https://www.rfc-editor.org/info/rfc3270>.






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   [RFC3443]  Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
              in Multi-Protocol Label Switching (MPLS) Networks",
              RFC 3443, DOI 10.17487/RFC3443, January 2003,
              <https://www.rfc-editor.org/info/rfc3443>.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              DOI 10.17487/RFC3473, January 2003,
              <https://www.rfc-editor.org/info/rfc3473>.

   [RFC4023]  Worster, T., Rekhter, Y., and E. Rosen, Ed.,
              "Encapsulating MPLS in IP or Generic Routing Encapsulation
              (GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
              <https://www.rfc-editor.org/info/rfc4023>.

   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206,
              DOI 10.17487/RFC4206, October 2005,
              <https://www.rfc-editor.org/info/rfc4206>.

   [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, <https://www.rfc-editor.org/info/rfc4385>.

   [RFC5085]  Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
              Circuit Connectivity Verification (VCCV): A Control
              Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
              December 2007, <https://www.rfc-editor.org/info/rfc5085>.

   [RFC5129]  Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
              Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January
              2008, <https://www.rfc-editor.org/info/rfc5129>.

   [RFC5462]  Andersson, L. and R. Asati, "Multiprotocol Label Switching
              (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
              Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
              2009, <https://www.rfc-editor.org/info/rfc5462>.

   [RFC6003]  Papadimitriou, D., "Ethernet Traffic Parameters",
              RFC 6003, DOI 10.17487/RFC6003, October 2010,
              <https://www.rfc-editor.org/info/rfc6003>.







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   [RFC7510]  Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
              "Encapsulating MPLS in UDP", RFC 7510,
              DOI 10.17487/RFC7510, April 2015,
              <https://www.rfc-editor.org/info/rfc7510>.

   [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>.

16.2.  Informative references

   [I-D.ietf-detnet-architecture]
              Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", draft-ietf-
              detnet-architecture-05 (work in progress), May 2018.

   [I-D.ietf-detnet-dp-alt]
              Korhonen, J., Farkas, J., Mirsky, G., Thubert, P.,
              Zhuangyan, Z., and L. Berger, "DetNet Data Plane Protocol
              and Solution Alternatives", draft-ietf-detnet-dp-alt-00
              (work in progress), October 2016.

   [I-D.ietf-detnet-dp-sol-ip]
              Korhonen, J., Varga, B., "DetNet IP Data Plane
              Encapsulation", 2018.

   [I-D.sdt-detnet-security]
              Mizrahi, T., Grossman, E., Hacker, A., Das, S.,
              "Deterministic Networking (DetNet) Security
              Considerations, draft-sdt-detnet-security, work in
              progress", 2017.

   [IEEE8021CB]
              Finn, N., "Draft Standard for Local and metropolitan area
              networks - Seamless Redundancy", IEEE P802.1CB
              /D2.1 P802.1CB, December 2015,
              <http://www.ieee802.org/1/files/private/cb-drafts/
              d2/802-1CB-d2-1.pdf>.

   [IEEE8021Q]
              IEEE 802.1, "Standard for Local and metropolitan area
              networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
              2014)", 2014, <http://standards.ieee.org/about/get/>.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <https://www.rfc-editor.org/info/rfc2205>.



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   [RFC3985]  Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
              Edge-to-Edge (PWE3) Architecture", RFC 3985,
              DOI 10.17487/RFC3985, March 2005,
              <https://www.rfc-editor.org/info/rfc3985>.

   [RFC4448]  Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
              "Encapsulation Methods for Transport of Ethernet over MPLS
              Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
              <https://www.rfc-editor.org/info/rfc4448>.

   [RFC5654]  Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
              Sprecher, N., and S. Ueno, "Requirements of an MPLS
              Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
              September 2009, <https://www.rfc-editor.org/info/rfc5654>.

   [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
              L., and L. Berger, "A Framework for MPLS in Transport
              Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
              <https://www.rfc-editor.org/info/rfc5921>.

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073,
              DOI 10.17487/RFC6073, January 2011,
              <https://www.rfc-editor.org/info/rfc6073>.

   [RFC7551]  Zhang, F., Ed., Jing, R., and R. Gandhi, Ed., "RSVP-TE
              Extensions for Associated Bidirectional Label Switched
              Paths (LSPs)", RFC 7551, DOI 10.17487/RFC7551, May 2015,
              <https://www.rfc-editor.org/info/rfc7551>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8169]  Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
              and A. Vainshtein, "Residence Time Measurement in MPLS
              Networks", RFC 8169, DOI 10.17487/RFC8169, May 2017,
              <https://www.rfc-editor.org/info/rfc8169>.

Appendix A.  Example of DetNet data plane operation

   [Editor's note: Add a simplified example of DetNet data plane and how
   labels etc work in the case of MPLS-based PSN and utilizing PREOF.




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   The figure is subject to change depending on the further DT decisions
   on the label handling..]

Authors' Addresses

   Jouni Korhonen (editor)

   Email: jouni.nospam@gmail.com


   Balazs Varga (editor)
   Ericsson
   Magyar Tudosok krt. 11.
   Budapest  1117
   Hungary

   Email: balazs.a.varga@ericsson.com


































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