DetNet                                                  J. Korhonen, Ed.
Internet-Draft                                                  Broadcom
Intended status: Informational                                 J. Farkas
Expires: February March 18, 2017                                        G. Mirsky
                                                              P. Thubert
                                                               Y. Zhuang
                                                               L. Berger
                                                         August 17,
                                                      September 14, 2016

          DetNet Data Plane Protocol and Solution Alternatives


   This document identifies existing IP and MPLS, and other
   encapsulations that run over IP and/or MPLS data plane technologies
   that can be considered as the base line solution for deterministic
   networking data plane definition.

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   This Internet-Draft will expire on February March 18, 2017.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  DetNet Data Plane Overview  . . . . . . . . . . . . . . . . .   3
     3.1.  Example DetNet Service Scenarios  . . . . . . . . . . . .   6
   4.  Criteria for data plane solution alternatives . . . . . . . .   8
     4.1.  #1 Encapsulation and overhead . . . . . . . . . . . . . .   9
     4.2.  #2 Flow identification  . . . . . . . . . . . . . . . . .   9
     4.3.  #3 Packet sequencing and duplicate elimination  . . . . .   9
     4.4.  #4 Explicit routes  . . . . . . . . . . . . . . . . . . .  10
     4.5.  #5 Flow duplication and merging . . . . . . . . . . . . .  10
     4.6.  #6 Operations, Administration and Maintenance . . . . . .  11
     4.7.  #8 Class and quality of service capabilities  . . . . . .  11
     4.8.  #9 Packet traceability  . . . . . . . . . . . . . . . . .  12
     4.9.  #10 Technical maturity  . . . . . . . . . . . . . . . . .  12
   5.  Data plane solution alternatives  . . . . . . . . . . . . . .  12
     5.1.  DetNet Transport layer technologies . . . . . . . . . . .  13
       5.1.1.  Native IPv6 transport . . . . . . . . . . . . . . . .  13
       5.1.2.  Native IPv4 transport . . . . . . . . . . . . . . . .  16
       5.1.3.  Multiprotocol Label Switching (MPLS)  . . . . . . . .  19
       5.1.4.  Bit Indexed Explicit Replication (BIER) . . . . . . .  23
       5.1.5.  BIER - Traffic Engineering (BIER-TE)  . . . . . . . .  27
     5.2.  DetNet Service layer technologies . . . . . . . . . . . .  34  27
       5.2.1.  Generic Routing Encapsulation (GRE) . . . . . . . . .  34  27
       5.2.2.  MPLS-based Services for DetNet  . . . . . . . . . . .  36  29
       5.2.3.  Pseudo Wire Emulation Edge-to-Edge (PWE3) . . . . . .  37  30
       5.2.4.  MPLS-Based Ethernet VPN (EVPN)  . . . . . . . . . . .  41  34
       5.2.5.  Higher layer header fields  . . . . . . . . . . . . .  43  36
   6.  Summary of data plane alternatives  . . . . . . . . . . . . .  45  38
   7.  Security considerations . . . . . . . . . . . . . . . . . . .  47  40
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47  40
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  48  41
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  48  41
     10.1.  Informative References . . . . . . . . . . . . . . . . .  48  41
     10.2.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  57  50
   Appendix A.  Examples of combined DetNet Service and Transport
                layers . . . . . . . . . . . . . . . . . . . . . . .  58  50
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  58  50

1.  Introduction

   Deterministic Networking (DetNet) [I-D.ietf-detnet-problem-statement]
   provides a capability to carry unicast or multicast data flows for
   real-time applications with extremely low data loss rates, timely
   delivery and bounded packet delay variation
   [I-D.finn-detnet-architecture].  The deterministic networking Quality
   of Service (QoS) is expressed as 1) the minimum and the maximum end-
   to-end latency from source (talker) to destination (listener), and 2)
   probability of loss of a packet.  Only the worst-case values for the
   mentioned parameters are concerned.

   There are three techniques to achieve the QoS required by
   deterministic networks:

   o  Congestion protection,
   o  explicit routes,
   o  service protection.

   This document identifies existing IP and Multiprotocol Label
   Switching (MPLS) [RFC3031], layer-2 or layer-3 encapsulations and
   transport protocols that could be considered as foundations for a
   deterministic networking data plane.  The full scope of the
   deterministic networking data plane solution is considered including,
   as appropriate: quality of service (QoS); Operations, Administration
   and Maintenance (OAM); and time synchronization among other criteria
   described in Section 4.

   This document does not select a deterministic networking data plane
   protocol.  It does, however, elaborate what it would require to adapt
   and use a specific protocol as the deterministic networking data
   plane solution.  This document is only concerned with data plane
   considerations and, specifically, with topics that potentially impact
   potential deterministic networking aware data plane hardware.
   Control plane considerations are out of scope of this document.

2.  Terminology

   This document uses the terminology established in the DetNet
   architecture [I-D.finn-detnet-architecture].

3.  DetNet Data Plane Overview

   A "Deterministic Network" will be composed of DetNet enabled nodes
   i.e., End Systems, Edge Nodes, Relay Nodes and collectively deliver
   DetNet services.  DetNet enabled nodes are interconnected via Transit
   Nodes (i.e., routers) which support DetNet, but are not DetNet
   service aware.  Transit nodes see DetNet nodes as end points.  All
   DetNet enabled nodes are connect to sub-networks, where a point-to-
   point link is also considered as a simple sub-network.  These sub-
   networks will provide DetNet compatible service for support of DetNet
   traffic.  Examples of sub-networks include IEEE 802.1TSN and OTN.  Of
   course, multi-layer DetNet systems may also be possible, where one
   DetNet appears as a sub-network, and provides service to, a higher
   layer DetNet system.  A simple DetNet concept network is shown in
   Figure 1.

  TSN              Edge          Transit        Relay        DetNet
  End System       Node            Node         Node         End System

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

                 Figure 1: A Simple DetNet Enabled Network

   The DetNet data plane is logically divided into two layers (also see
   Figure 2):

   DetNet Service Layer

      The DetNet service layer provides adaptation of DetNet services.
      It is composed of a shim layer to carry deterministic flow
      specific attributes, which are needed during forwarding and for
      service protection.  DetNet enabled end systems originate and
      terminate the DetNet Service layer and are peers at the DetNet
      Service layer.  DetNet relay and edge nodes also implement DetNet
      Service layer functions.  The DetNet service layer is used to
      deliver traffic end to end across a DetNet domain.

   DetNet Transport Layer

      The DetNet transport layer is required on all DetNet nodes.  All
      DetNet nodes are end points and at the transport layer.  Non-DetNet
      service aware transit nodes deliver traffic between DetNet nodes.
      The DetNet transport layer operates below and supports the DetNet
      Service layer and optionally provides congestion protection for
      DetNet flows.

   Distinguishing the function of these two DetNet data plane layers
   helps to explore and evaluate various combinations of the data plane
   solutions available.  This separation of DetNet layers, while
   helpful, should not be considered as formal requirement.  For
   example, some technologies may violate these strict layers and still
   be able to deliver a DetNet service.

           |  Service  | PW, RTP/(UDP), GRE
           | Transport | (UDP)/IPv6, (UDP)/IPv4, MPLS LSPs, BIER, BIER-TE BIER

                 Figure 2: DetNet adaptation to data plane

   The two logical layers defined here aim to help to identify which
   data plane technology can be used for what purposes in the DetNet
   context.  This layering is similar to the data plane concept of MPLS,
   where some part of the label stack is "Service" specific (e.g., PW
   labels, VPN labels) and an other part is "Transport" specific (e.g,
   LSP label, TE label(s)).

   In some networking scenarios, the end system initially provides a
   DetNet flow encapsulation, which contains all information needed by
   DetNet nodes (e.g., Real-time Transport Protocol (RTP) [RFC3550]
   based DetNet flow transported over a native UDP/IP network or
   PseudoWire).  In other scenarios, the encapsulation formats might
   differ significantly.  As an example, a CPRI "application's" I/Q data
   mapped directly to Ethernet frames may have to be transported over an
   MPLS-based packet switched network (PSN).

   There are many valid options to create a data plane solution for
   DetNet traffic by selecting a technology approach for the DetNet
   Service layer and also selecting a technology approach for the DetNet
   Transport layer.  There are a high number of valid combinations.
   Therefore, not the combinations but the different technologies are
   evaluated along the criteria collected in Section 4.  Different
   criteria apply for the DetNet Service layer and the DetNet Transport
   layer, however, some of the criteria are valid for both layers.

   One of the most fundamental differences between different potential
   data plane options is the basic addressing and headers used by DetNet
   end systems.  For example, is the basic service a Layer 2 (e.g.,
   Ethernet) or Layer 3 (i.e., IP) service.  This decision impacts how
   DetNet end systems are addressed, and the basic forwarding logic for
   the DetNet Service layer.

3.1.  Example DetNet Service Scenarios

   In an attempt to illustrate a DetNet date plane, this document uses
   the Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3) [RFC5254]
   reference model shown in Figure 3 as the foundation for different
   DetNet data plane deployment options and how layering could work.
   Other reference models are possible but not covered in this document.
   Note that other technologies can be also used to implement DetNet,
   Multi-Segment PW is only used here to illustrate functions, features
   and layering from the perspective of the architecture.

         Native  |<--------Multi-Segment Pseudowire----->|  Native
         Service |         PSN              PSN          |  Service
          (AC)   |     |<-Tunnel->|     |<-Tunnel->|     |  (AC)
           |     V     V     1    V     V     2    V     V   |
           |     +-----+          +-----+          +---- +   |
   +---+   |     |T-PE1|==========|S-PE1|==========|T-PE2|   |    +---+
   |   |---|-----|........PW1...........|...PW3..........|---|----|   |
   |CE1|   |     |     |          |     |          |     |   |    |CE2|
   |   |---------|........PW2...........|...PW4..........|--------|   |
   +---+   |     |     |==========|     |==========|     |   |    +---+
       ^         +-----+          +-----+          +-----+        ^
       |     Provider Edge 1         ^        Provider Edge 3     |
       |                             |                            |
       |                     PW switching point                   |
       |                                                          |
       |<------------------- Emulated Service ------------------->|

              Figure 3: Pseudo Wire switching reference model

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

          TSN    |<----- End to End DetNet Service ----->|  TSN
         Service |        Transit          Transit       | Service
   TSN    (AC)   |     |<-Tunnel->|     |<-Tunnel->|     |  (AC)     TSN
   End     |     V     V     1    V     V     2    V     V   |       End
   System  |     +-----+          +-----+          +---- +   |    System
   +---+   |     |T-PE1|==========|S-PE1|==========|T-PE2|   |    +---+
   |   |---|-----|.X_..DetNet Flow1..X..|...DF3........X.|---|----|   |
   |CE1|   |     |  \  |          |     |          |  /  |   |    |CE2|
   |   |         |...X_...DF2........X..|...DF4......X_..|        |   |
   +---+         |     |==========|     |==========|     |        +---+
       ^         +-----+          +-----+          +-----+        ^
       |        Edge Node        Relay Node       Edge Node       |
       |                                                          |
       |<--------------- Emulated TSN Service ------------------->|

                    Figure 4: IEEE 802.1TSN over DetNet

   Figure 5 illustrates how end to end native DetNet service can be
   provided.  In this case, the end systems are able to send and receive
   native DetNet flows.  For example, as PseudoWire (PW) encapsulated
   IP.  Like earlier the 'X' in the end systems, edge and relay nodes
   represents potential DetNet flow packet replication and elimination
   points.  Here the relay nodes may change the underlying transport,
   for example replacing IP with MPLS or tunneling IP over MPLS (e.g.,
   via L3VPNs), or simply interconnect network domains.

          DetNet                                           DetNet
          Service         Transit          Transit        Service
   DetNet   |          |<-Tunnel->|     |<-Tunnel->|         |    DetNet
   End      |          V     1    V     V     2    V         |    End
   System   |    +-----+          +-----+          +-----+   |    System
   +---+    |    |S-PE1|==========|S-PE2|==========|S-PE3|   |    +---+
   |  X....DFa.....X_.......DF1.......X_....DF3........X.....DFa...X  |
   |CE1|=========|  \  |          |  /  |          |  /  |========|CE2|
   |   |    |    |   \......DF2.....X_......DF4....../   |   |    |   |
   +---+         |     |==========|     |==========|     |        +---+
       ^         +-----+          +-----+          +-----+        ^
       |        Relay Node       Relay Node       Relay Node      |
       |                                                          |
       |<------------- End to End DetNet Service ---------------->|

                          Figure 5: Native DetNet

   Figure 6 illustrates how a IEEE 802.1TSN end system could communicate
   with a native DetNet end system through an edge node which provides a
   TSN to DetNet inter-working capability.  The edge node would add and
   remove required DetNet data plane encapsulation as well as provide
   any needed address mapping.  As in previous figures, the 'X' in the
   end systems, edge and relay nodes represents potential DetNet flow
   packet duplication and elimination points.

        TSN    |<----- End to End DetNet Service -------------->|
       Service |        Transit          Transit                |
TSN     (AC)   |     |<-Tunnel->|     |<-Tunnel->|       DetNet | DetNet
End      |     V     V     1    V     V     2    V      Service | End
System   |     +-----+          +-----+          +-----+   |    V System
 +---+   |     |T-PE1|==========|S-PE1|==========|S-PE2|   |    +---+
 |   |---|-----|.X_.......DF1......X..|...DF3........X.|...DFa...X  |
 |CE1|   |     |  \  |          |     |          |  /  |========|CE2|
 |   |         |   \.....DF2.......X..|...DF4....../   |   |    |   |
 +---+         |     |==========|     |==========|     |        +---+
     ^         +-----+          +-----+          +-----+        ^
     |        Edge Node        Relay Node      Relay Node       |
     |                                                          |
     |<----------------- End to End Service ------------------->|

                 Figure 6: IEEE 802.1TSN to native DetNet

4.  Criteria for data plane solution alternatives

   This section provides criteria to help to evaluate potential options.
   Each deterministic networking data plane solution alternative is
   described and evaluated using the criteria described in this section.
   The used criteria enumerated in this section are selected so that
   they highlight the existence or lack of features that are expected or
   seen important to a solution alternative for the data plane solution.

   The criteria for the DetNet Service layer:

   #1 Encapsulation and overhead
   #2 Flow identification (Service ID part of the DetNet flows)
   #3 Packet sequencing and duplicate elimination
   #5 Flow duplication and merging
   #6 Operations, Administration and Maintenance (capabilities)
   #8 Class and quality of service capabilities (DetNet Service
   #10  Technical maturity

   The criteria for the DetNet Transport layer:

   #1 Encapsulation and overhead
   #2 Flow identification
   #4 Explicit routes (network path)
   #5 Flow duplication and merging (sometimes, flow duplication and
      merging is also doable at the transport layer, not just at the
      service layer)

   #6 Operations, Administration and Maintenance (capabilities,
      performance management, packet traceability)
   #8 Class and quality of service capabilities (DetNet Transport
   #9 Packet traceability (can be part of OAM)
   #10  Technical maturity

   [Editor's Note: numbering is off because #7 is removed.]

   [Editor's Note: #9 should(?) be integrated into #6.]

   Most of the criteria is relevant for both the DetNet Service and
   DetNet Transport layers.  However, different aspects of the same
   criteria may relevant for different layers, for example, as it is the
   case with criteria #5 Packet replication and elimination.

4.1.  #1 Encapsulation and overhead

   Encapsulation and overhead is related to how the DetNet data plane
   carries DetNet flow.  In several cases a DetNet flow has to be
   encapsulated inside other protocols, for example, when transporting a
   layer-2 Ethernet frame over an IP transport network.  In some cases a
   tunneling like encapsulation can be avoided by underlying transport
   protocol translation, for example, translating layer-2 Ethernet frame
   including addressing and flow identification into native IP traffic.
   Last it is possible that sources and destinations handle
   deterministic flows natively in layer-3.  This criteria concerns what
   is the encapsulation method the solution alternative support:
   tunneling like encapsulation, protocol translation or native layer-3
   transport.  In addition to the encapsulation mechanism this criteria
   is also concerned of with the processing and specifically the encapsulate
   encapsulation header overhead.

4.2.  #2 Flow identification

   The solution alternative has to provide means to identify specific
   deterministic flows.  The flow identification can, for example, be an
   explicit field in the data plane encapsulation header or implicitly
   encoded into the addressing scheme of the used data plane protocol or
   their combination.  This criteria concerns the availability and
   details of deterministic flow identification the data plane protocol
   alternative has.

4.3.  #3 Packet sequencing and duplicate elimination

   The solution alternative has to provide means for end systems to
   number packets sequentially and transport that sequencing information
   along with the sent packets.  In addition to possible reordering of
   packets other important uses for sequencing are detecting duplicates
   and lost packets.

   In a case of intentional packet duplication a combination of flow
   identification and packet sequencing allows for detecting and
   eliminating duplicates at the destination (see Section 4.5 for more

4.4.  #4 Explicit routes

   The solution alternative has to provide a mechanism(s) for
   establishing explicit routes that all packets belonging to a
   deterministic flow will follow.  The explicit route can be seen as a
   form of source routing or a pre-reserved path e.g., using some
   network management procedure.  It should be noted that the explicit
   route does not need to be detailed to a level where every possible
   intermediate node along the path is part of the named explicit route.
   RSVP-TE [RFC3209] supports explicit routes, and typically provides
   pinned data paths for established LSPs.  At Layer-2, the IEEE
   802.1Qca [IEEE802.1Qca] specification defines how to do explicit path
   control in a bridged network and its IETF counter part is defined in
   [RFC7813].  This criteria concerns the available mechanisms for
   explicit routes for the data plane protocol alternative.

4.5.  #5 Flow duplication and merging

   Flow duplication and flow merging are methods being considered to
   provide DetNet service protection.  The objective for supporting flow
   duplication and flow merging is to enable hitless (or lossless) 1+1
   protection.  Other methods, if so identified, are also permissible.

   The solution alternative has to provide means for end systems, relay
   and edge nodes to be able to duplicate packets into duplicate flows,
   and later merge the flows into one for duplicate elimination.  The
   duplication and merging may take place at multiple points in the
   network in order to ensure that one (or more) equipment failure
   event(s) still leave at least one path intact for a deterministic
   networking flow.  The goal is again to enable hitless 1+1 protection
   in a way that no packet gets lost or there is no ramp up time when
   either one of the paths fails for one reason or another.

   Another concern regarding packet duplication is how to enforce
   duplicated packets to take different route or path while the final
   destination still remains the same.  With strict source routing, all
   the intermediate hops are listed and paths can be guaranteed to be
   non-overlapping.  Loose source routing only signals some of the
   intermediate hops and it takes additional knowledge to ensure that
   there is no single point of failure.

   The IEEE 802.1CB (seamless redundancy) [IEEE8021CB] is an example of
   Ethernet-based solution that defines packet sequence numbering, flow
   duplication, flow merging, duplicate packet identification and
   elimination.  The deterministic networking data plane solution
   alternative at layer-3 has to provide equivalent functionality.  This
   criteria concerns the available mechanisms for packet replication and
   duplicate deletion the data plane protocol alternative has.

4.6.  #6 Operations, Administration and Maintenance

   The solution alternative should demonstrate an availability of
   appropriate standardized OAM tools that can be extended for
   deterministic networking purposes with a reasonable effort, when
   required.  The OAM tools do not necessarily need to be specific to
   the data plane protocol as it could be the case, for example, with
   MPLS-based data planes.  But any OAM-related implications or
   requirements on data plane hardware must be considered.

   The OAM includes but is not limited to tools listed in the
   requirements for overlay networks
   [I-D.ooamdt-rtgwg-ooam-requirement].  Specifically, the performance
   management requirements are of interest at both service and transport

4.7.  #8 Class and quality of service capabilities

   Class and quality of service, i.e., CoS and QoS, are terms that are
   often used interchangeably and confused.  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 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).

   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].

   A critical DetNet service enabled by QoS (and perhaps CoS) is
   delivering zero congestion loss.  There are different mechanisms that
   maybe used separately or in combination to deliver a zero congestion
   loss service.  The key aspect of this objective is that DetNet
   packets are not discarded due to congestion at any point in a DetNet
   aware network.

   In the context of the data plane solution there should be means for
   flow identification, which then can be used to map a flow against
   specific resources and treatment in a node enforcing the QoS.
   Hereto,  For
   DetNet, certain aspects of CoS and QoS may be provided by the
   underlying sub-net technology, e.g., actual queuing or IEEE 802.3x
   priority flow control (PFC).

4.8.  #9 Packet traceability

   For the network management and specifically for tracing
   implementation or network configuration errors any means to find out
   whether a packet is a replica, which node performed replication, and
   which path was intended for the replica, can be very useful.  This
   criteria concerns the availability of solutions for tracing packets
   in the context of data plane protocol alternative.  Packet
   traceability can also be part of OAM.

4.9.  #10 Technical maturity

   The technical maturity of the data plane solution alternative is
   crucial, since it basically defines the effort, time line and risks
   involved for the use of the solution in deployments.  For example,
   the maturity level can be categorized as available immediately,
   available with small extensions, available with re-purposing/
   redefining portions of the protocol or its header fields.  Yet
   another important measure for maturity is the deployment experience.
   This criteria concerns the maturity of the data plane protocol
   alternative as the solution alternative.  This criteria is
   particularly important given, as previously noted, that the DetNet
   data plane solution is expected to impact, i.e., be supported in,

5.  Data plane solution alternatives

   The following sections describe and rate deterministic data plane
   solution alternatives.  In "Analysis and Discussion" section each
   alternative is evaluated against the criteria given in Section 4 and
   rated using the following: (M)eets the criteria, (W)ork needed, and
   (N)ot suitable or too much work envisioned.

5.1.  DetNet Transport layer technologies

5.1.1.  Native IPv6 transport  Solution description

   This section investigates the application of native IPv6 [RFC2460] as
   the data plane for deterministic networking along the criteria
   collected in Section 4.

   The application of higher OSI layer headers, i.e., headers deeper in
   the packet, can be considered.  Two aspects have to be taken into
   account for such solutions. (i) Those header fields can be encrypted.
   (ii) Those header fields are deeper in the packet, therefore, routers
   have to apply deep packet inspection.  See further details in
   Section 5.2.5.  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      IPv6 can encapsulate DetNet Service layer headers (and associated
      DetNet flow payload) like any other upper-layer header indicated
      by the Next Header.  The fixed header of an IPv6 packet is 40
      bytes [RFC2460].  This overhead is bigger if any Extension Header
      is used, and a generic behaviour for host and forwarding nodes is
      specified in [RFC7045].  However, the exact overhead (Section 4.1)
      depends on what solution is actually used to provide DetNet
      features, e.g., explicit routing or DetNet service protection if
      any of these is applied.

      IPv6 has two types of Extension Headers that are processed by
      intermediate routers between the source and the final destination
      and may be of interest for the data plane signaling, the Routing
      Header that is used to direct the traffic via intermediate routers
      in a strict or loose source routing way, and the Hop-by-Hop
      Options Header that carries optional information that must be
      examined by every node along a packet's delivery path.  The Hop-
      by-Hop Options Header, when present, must immediately follow the
      IPv6 Header and it is not possible to limit its processing to the
      end points of Source Routed segments.

      IPv6 also provides a Destination Options Header that is used to
      carry optional information to be examined only by a packet's
      destination node(s).  The encoding of the options used in the Hop-
      by-Hop and in the Destination Options Header indicates the
      expected behavior when a processing IPv6 node does not recognize
      the Option Type, e.g. skip or drop; it should be noted that due to
      performance restrictions nodes may ignore the Hop-by-Hop Option
      Header, drop packets containing a Hop-by-Hop Option Header, or
      assign packets containing a Hop-by-Hop Option Header to a slow
      processing path [I-D.ietf-6man-rfc2460bis] (e.g. punt packets from
      hardware to software forwarding which is highly detrimental to the

      The creation of new Extension Headers that would need to be
      processed by intermediate nodes is strongly discouraged.  In
      particular, new Extension Header(s) having hop-by-hop behavior
      must not be created or specified.  New options for the existing
      Hop-by-Hop Header should not be created or specified unless no
      alternative solution is feasible [RFC6564].

   #2 Flow identification (W)

      The 20-bit flow label field of the fixed IPv6 header is suitable
      to distinguish different deterministic flows.  But guidance on the
      use of the flow label provided by [RFC6437] places restrictions on
      how the flow label can be used.  In particular, labels should be
      chosen from an approximation to a discrete uniform distribution.
      Additionally, existing implementations generally do not open APIs
      to control the flow label from the upper layers.

      Alternatively, the Flow identification could be transported in a
      new option in the Hop-by-Hop Options Header.

   #4 Explicit routes (W)

      One possibility is for a Software-Defined Networking (SDN)
      [RFC7426] based approach to be applied to compute, establish and
      manage the explicit routes, leveraging Traffic Engineering (TE)
      extensions to routing protocols [RFC5305] [RFC7752] and evolving
      to the Path Computation Element (PCE) Architecture [RFC5440],
      though a number of issues remain to be solved [RFC7399].

      Segment Routing (SR) [I-D.ietf-spring-segment-routing] is a new
      initiative to equip IPv6 with explicit routing capabilities.  The
      idea for the DetNet data plane would be to apply SR to IPv6 with
      the addition of a new type of routing extension header
      [I-D.ietf-6man-segment-routing-header] to explicitly signal the
      path in the data plane between the source and the destination,
      and/or between replication points and elimination points if this
      functionality is used.

   #5 Flow duplication and merging (W)
      The functionality of replicating a packet exists in IPv6 but is
      limited to multicast flows.  In order to enforce replicated
      packets to take different routes and eventually again merge flow
      (bring them to a specific merging point), IP-in-IP encapsulation
      and Segment Routing could be leveraged to signal a segment in a
      packet.  A replication point would insert a different routing
      header in each copy it makes, the routing header providing
      explicitly the hops to the merging point for that particular
      replica of the packet, in a strict or in a loose source routing
      fashion.  A flow merging point would pop the routing headers from
      the various copies it gets and do the rest of the required
      processing for merging the two flows into one flow.

   #6 Operations, Administration and Maintenance (M/W)

      IPv6 enjoys the existing toolbox for generic IP network
      management.  However, IPv6 specific management features are still
      not at the level comparable to that of IPv4.  Particular areas of
      concerns are those that are IPv6 specific, for example, related to
      neighbor discovery protocol (ND), stateless address
      autoconfiguration (SLAAC), subscriber identification, and
      security.  While the standards are already mostly in place the
      implementations in deployed equipment can be lacking or inadequate
      for commercial deployments.  This is larger issue with older
      existing equipment.

   #8 Class and quality of service capabilities (W)

      IPv6 provides support for CoS and QoS.  CoS is provided by
      DiffServ which is enabled by IP header differentiated services
      code point (DSCP) and QoS is defined as part of RSVP [RFC2205].
      DiffServ support is widely available, while RSVP for IP packets is
      generally not supported.

   #9 Packet traceability (W)

      The traceability of replicated packets involves the capability to
      resolve which replication point issued a particular copy of a
      packet, which segment was intended for that replica, and which
      particular packet of which particular flow this is.  Sequence also
      depends on the sequencing mechanism.  As an example, the
      replication point may be indicated as the source of the packet if
      IP-in-IP encapsulation is used to forward along segments.  Another
      alternate to IP-in-IP tunneling along segments would be to protect
      the original source address in a destination option similar to the
      Home Address option [RFC6275] and then use the address of the
      replication point as source in the IP header.

      The traceability also involves the capability to determine if a
      particular segment is operational.  While IPv6 as such has no
      support for reversing a path, it appears source route extensions
      such as the one defined for segment routing could be used for
      tracing purposes.  Though it is not a usual practice, IPv6
      [RFC2460] expects that a Source Route path may be reversed, and
      the standard insists that a node must not include the reverse of a
      Routing Header in the response unless the received Routing Header
      was authenticated.

   #10 Technical maturity (M/W)

      IPv6 has been around about 20 years.  However, large scale global
      and commercial IPv6 deployments are rather new dating only few
      years back to around 2012.  While IPv6 has proven itself for best
      effort traffic, DiffServ usage is less common and QoS capabilities
      are not currently present.  Additional, there are number of small
      issues to work on as they show up once operations experience

      The Cisco 6Lab site [1] provides information on IPv6 deployment
      per country, indicating figures for prefixes, transit AS, content
      and users.  Per this site, many countries, including Canada,
      Brazil, the USA, Germany, France, Japan, Portugal, Sweden,
      Finland, Norway, Greece, and Ecuador, achieve a deployment ratio
      above 30 percent, and the overall adoption reported by Google
      Statistics [2] is now above 10 percent.  Summary

   IPv6 supports a significant portion of the identified DetNet data
   plane criteria today.  There are aspects of the DetNet data plane
   that are not fully supported, notably QoS, but these can be
   incrementally added or supplemented by the underlying sub-network
   layer.  IPv6 may be a choice as the DetNet Transport layer in
   networks where other technologies such as MPLS are not deployed.

5.1.2.  Native IPv4 transport  Solution description

   IPv4 [RFC0791] is in principle the same as IPv6, except that it has a
   smaller address space.  However, IPv6 was designed around the fact
   that extension headers are an integral part of the protocol and
   operation from the beginning, although the practice may some times
   prove differently [RFC7872].  IPv4 does support header options, but
   these have historically not been supported on in hardware-based
   forwarding so are generally blocked or handled at a much slower rate.
   In either case, the use of IP header options is generally avoided.
   In the context of deterministic networking data plane solutions the
   major difference between IPv4 and IPv6 seems to be the practical
   support for header extensibility.  Anything below and above the IP
   header independent of the version is practically the same.  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      The fixed header of an IPv4 packet is 20 bytes [RFC0791].  IP
      options add overhead, but are not generally used and are not
      considered as part of this document.

   #2 Flow identification (W)

      The IPv4 header has a 16-bit identification field that was
      originally intended for assisting fragmentation and reassembly of
      IPv4 packets as described in [RFC0791].  The identification field
      has also been proposed to be used for actually identifying flows
      between two IP addresses and a given protocol for detecting and
      removing duplicate packets [RFC1122].  However, recent update
      [RFC6864] to both [RFC0791] and [RFC1122] restricts the use of
      IPv4 identification field only to fragmentation purposes.

      The IPv4 also has a stream identifier option [RFC0791], which
      contains a 16-bit SATNET stream identifier.  However, the option
      has been deprecated [RFC6814].  The conclusion is that stream
      identification does not work nicely with IPv4 header alone and a
      traditional 5-tuple identification might not also be enough in a
      case of a flow duplication or encrypted flows.  For a working
      solution, upper layer protocol headers such as RTP or PWs may be
      required for unambiguous flow identification.  There is also
      emerging work within the IETF that may provide new flow
      identification alternatives.

   #4 Explicit routes (W)

      IPv4 has two source routing option specified: the loose source and
      record route option (LSRR), and the strict source and record route
      option (SSRR) [RFC0791].  The support of these options in the
      Internet is questionable but within a closed network the support
      may be assumed.  But as both these options use IP header options,
      which are generally not supported in hardware, use of these
      options are questionable.  Of course, the same options of SDN and
      SR approaches discussed above for IPv6 may be equally applicable
      to IPv4.

   #5 Flow duplication and merging (W/N)

      The functionality of replicating a packet exists in IPv4 but is
      limited to multicast flows.  In general the issue regarding the
      IPv6 packet replication also applies to IPv4.  Duplicate packet
      detection for IPv4 is studied in [RFC6621] to a great detail in
      the context of simplified multicast forwarding.  In general there
      is no good way to detect duplicated packets for IPv4 without
      additional upper layer protocol support.

   #6 Operations, Administration and Maintenance (M)

      IPv4 enjoys the extensive and "complete" existing toolbox for
      generic IP network management.

   #8 Class and quality of service capabilities (M/W)

      IPv4 provides support for CoS and QoS.  CoS is provided by
      DiffServ which is enabled by IP header differentiated services
      code point (DSCP) and QoS is defined as part of RSVP [RFC2205].
      DiffServ support is widely available, while RSVP for IP packets is
      generally not supported.

   #9 Packet traceability (W)

      The IPv4 has similar needs and requirements for traceability as
      IPv6 (see Section  The IPv4 has a traceroute option
      [RFC6814] that could be used to record the route the packet took.
      However, the option has been deprecated [RFC6814].

   #10 Technical maturity (M/W)

      IPv4 can be considered mature technology with over 30 years of
      implementation, deployment and operations experience.  As with
      IPv6, today's commercial implementations and deployments of IPv4
      generally lack any support for QoS.  Summary

   The IPv4 has specifications to support most of the identified DetNet
   data plane criteria today.  However, several of those have already
   been deprecated or their wide support is not guaranteed.  The DetNet
   data plane criteria that are not fully supported could be
   incrementally added or supplemented by the underlying sub-network
   layer.  Unfortunately, the IPv4 has had limited success getting its
   extensions deployed at large.  However, introducing new extensions
   might have a better success in closed networks (like DetNet) than in
   Internet.  Due to the popularity of the IPv4, it should be considered
   as a potential choice for the DetNet Transport layer.

5.1.3.  Multiprotocol Label Switching (MPLS)

   Multiprotocol Label Switching Architecture (MPLS) [RFC3031] and its
   variants, MPLS with Traffic Engineering (MPLS-TE) [RFC3209] and
   [RFC3473], and MPLS Transport Profile (MPLS-TP) [RFC5921] is a widely
   deployed technology that switches traffic based on MPLS label stacks
   [RFC3032] and [RFC5960].  MPLS is the foundation for Pseudowire-based
   services Section 5.2.3 and emerging technologies such as Bit-Indexed
   Explicit Replication (BIER) Section 5.1.4 and Source Packet Routing

   MPLS supports the equivalent of both the DetNet Service and DetNet
   Transport layers, and provides a very rich set of mechanisms that can
   be reused directly, and perhaps augmented in certain cases, to
   deliver DetNet services.  At the DetNet Transport layer, MPLS
   provides forwarding, protection and OAM services.  At the DetNet
   Service Layer it provides client service adaption, directly, via
   Pseudowires Section 5.2.3 and via other label-like mechanisms such as
   EPVN Section 5.2.4.  A representation of these options are shown in
   Figure 7.

   PW-Based               EVPN Labeled                 IP
   Services                  Services                Transport
 |------------|  |-----------------------------|  |------------|

   Emulated       EVPN over LSP   EVPN w/ ESI ID        IP
                                  |  Payload   |
 +------------+   +------------+  +------------+             (Service)
 | PW Payload |   |  Payload   |  |ESI Lbl(S=1)|
 +------------+   +------------+  +------------+  +------------+
 |PW Lbl(S=1) |   |VPN Lbl(S=1)|  |VPN Lbl(S=0)|  |     IP     |
 |LSP Lbl(S=0)|   |LSP Lbl(S=0)|  |LSP Lbl(S=0)|  |LSP Lbl(S=1)|
 +------------+   +------------+  +------------+  +------------+
       .                .               .               .
       .                .               .               .    (Transport)
       .                .               .               .

~~~~~~~~~~~ denotes DetNet Service <-> DetNet Transport layer boundary

                       Figure 7: MPLS-based Services

   MPLS can be controlled in a number of ways including via a control
   plane, via the management plane, or via centralized controller (SDN)
   based approaches.  MPLS also provides standard control plane
   reference points.  Additional information on MPLS architecture and
   control can be found in [RFC5921].  A summary of MPLS control plane
   related functions can be found in [RFC6373].  The remainder of this
   section will focus [RFC6373].  The remainder of this section will
   focus on the MPLS transport data plane, additional
   information on the MPLS service data plane can be found below in
   Section 5.2.2.  Solution description

   The following draws heavily from [RFC5960].

   Encapsulation and forwarding of packets traversing MPLS LSPs follows
   standard MPLS packet encapsulation and forwarding as defined in
   [RFC3031], [RFC3032], [RFC5331], and [RFC5332].

   Data plane Quality of Service capabilities are included in the MPLS
   in the form of Traffic Engineered (TE) LSPs [RFC3209] and the MPLS
   Differentiated Services (DiffServ) architecture [RFC3270].  Both
   E-LSP and L-LSP MPLS DiffServ modes are defined.  The Traffic Class
   field (formerly the EXP field) of an MPLS label follows the
   definition of [RFC5462] and [RFC3270].

   Except for transient packet reordering that may occur, for example,
   during fault conditions, packets are delivered in order on L-LSPs,
   and on E-LSPs within a specific ordered aggregate.

   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.

   Equal-Cost Multi-Path (ECMP) load-balancing is possible with MPLS
   LSPs and can be avoided using a number of techniques.  The same holds
   for Penultimate Hop Popping (PHP).

   MPLS includes the following LSP types:

   o  Point-to-point unidirectional
   o  Point-to-point associated bidirectional
   o  Point-to-point co-routed bidirectional
   o  Point-to-multipoint unidirectional

   Point-to-point unidirectional LSPs are supported by the basic MPLS
   architecture [RFC3031].

   A point-to-point associated bidirectional LSP between LSRs A and B
   consists of two unidirectional point-to-point LSPs, one from A to B
   and the other from B to A, which are regarded as a pair providing a
   single logical bidirectional transport path.

   A point-to-point co-routed bidirectional LSP is a point-to-point
   associated bidirectional LSP with the additional constraint that its
   two unidirectional component LSPs in each direction follow the same
   path (in terms of both nodes and links).  An important property of
   co-routed bidirectional LSPs is that their unidirectional component
   LSPs share fate.

   A point-to-multipoint unidirectional LSP functions in the same manner
   in the data plane, with respect to basic label processing and packet-
   switching operations, as a point-to-point unidirectional LSP, with
   one difference: an LSR may have more than one (egress interface,
   outgoing label) pair associated with the LSP, and any packet it
   transmits on the LSP is transmitted out all associated egress
   interfaces.  Point-to-multipoint LSPs are described in [RFC4875] and
   [RFC5332].  TTL processing and exception handling for point-to-
   multipoint LSPs is the same as for point-to-point LSPs.

   Additional data plane capabilities include Linear Protection,
   [RFC6378] and [RFC7271].  And the in progress work on MPLS support
   for time synchronization [I-D.ietf-mpls-residence-time].  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      There are two perspectives to consider when looking at
      encapsulation.  The first is encapsulation to support services.
      These considerations are part of the DetNet service layer and are
      covered below, see Sections 5.2.3 and 5.2.4.

      The second perspective relates to encapsulation, if any, which is
      needed to transport packets across network.  In this case, the
      MPLS label stack, [RFC3032] is used to identify flows across a
      network.  MPLS labels are compact and highly flexible.  They can
      be stacked to support client adaptation, protection, network
      layering, source routing, etc.

      The number of DetNet Transport layer specific labels is flexible
      and support a wide range of applicable functions and MPLS domain
      characteristics (e.g., TE-tunnels, Hierarchical-LSPs, etc.).

   #2 Flow identification (M)
      MPLS label stacks provide highly flexible ways to identify flows.
      Basically, they enable the complete separation of traffic
      classification from traffic treatment and thereby enable arbitrary
      combinations of both.

      For the DetNet flow identification the MPLS label stack can be
      used to support n-layers of DetNet flow identification.  For
      example, using dedicated LSP per DetNet flow would simplify flow
      identification for intermediate transport nodes, and additional
      hierarchical LSPs could be used to facilitate scaling.

   #4 Explicit routes (M)

      MPLS supports explicit routes based on how LSPs are established,
      e.g., via TE explicit routes [RFC3209].  Additional, but not
      required, capabilities are being defined as part of Segment
      Routing (SR) [I-D.ietf-spring-segment-routing].

   #5 Flow duplication and merging (M/W)

      MPLS as DetNet Transport layer supports the replication via point-
      to-multipoint LSPs.  At the MPLS LSP level, there are mechanisms
      defined to provide 1+1 protection, which could help in realizing
      the flow merging function.  The current definitions [RFC6378] and
      [RFC7271] use OAM mechanisms to support and coordinate protection
      switching and packet loss is possible during a switch.  While such
      this level of protection may be sufficient for many DetNet
      applications, when truly hitless (i.e., zero loss) switching is
      required, additional mechanisms will be needed.  It is expected
      that these additional mechanisms will be defined at a DetNet

   #6 Operations, Administration and Maintenance (M)

      MPLS already includes a rich set of OAM functions at both the
      Service and Transport Layers.  This includes LSP ping [ref] and
      those enabled via the MPLS Generic Associated Channel [RFC5586]
      and registered by IANA [4].

   #8 Class and quality of service capabilities (M/W)

      As previously mentioned, Data plane Quality of Service
      capabilities are included in the MPLS in the form of Traffic
      Engineered (TE) LSPs [RFC3209] and the MPLS Differentiated
      Services (DiffServ) architecture [RFC3270].  Both E-LSP and L-LSP
      MPLS DiffServ modes are defined.  The Traffic Class field
      (formerly the EXP field) of an MPLS label follows the definition
      of [RFC5462] and [RFC3270].  One potential open area of work is
      synchronized, time based scheduling.  Another is shaping, which is
      generally not supported in shipping MPLS hardware.

   #9 Packet traceability (M)

      MPLS supports multiple tracing mechanisms.  A control based one is
      defined in [RFC3209].  An OAM based mechanism is defined in MPLS
      On-Demand Connectivity Verification and Route Tracing [RFC6426].

   #10 Technical maturity (M)

      MPLS as a mature technology that has been widely deployed in many
      networks for many years.  Numerous vendor products and multiple
      generations of MPLS hardware have been built and deployed.  Summary

   MPLS is a mature technology that has been widely deployed.  Numerous
   vendor products and multiple generations of MPLS hardware have been
   built and deployed.  MPLS LSPs support a significant portion of the
   identified DetNet data plane criteria today.  Aspects of the DetNet
   data plane that are not fully supported can be incrementally added.
   It's worth noting that a number of limitations are in shipping
   hardware, versus at the protocol specification level, e.g., shaping.

5.1.4.  Bit Indexed Explicit Replication (BIER)

   Bit Indexed Explicit Replication [I-D.ietf-bier-architecture] (BIER)
   is a network plane replication technique that was initially intended
   as a new method for multicast distribution.  In a nutshell, a BIER
   header includes a bitmap that explicitly signals the destinations
   that are intended for a particular packet, which means that 1) the
   source is aware of the individual destinations and 2) the BIER
   control plane is a simple extension of the unicast routing as opposed
   to a dedicated multicast data plane, which represents a considerable
   reduction in OPEX.  For this reason, the technology faces is getting a lot
   of traction from Service Providers.  Section 5.1.4 discusses  In the
   applicability context of DetNet, BIER
   may be applicable for replication in the DetNet.

   The simplicity of the BIER technology makes it very versatile implementing packet replication, as a
   network plane signaling protocol.  Already, a new Traffic Engineering
   variation is emerging that uses bits to signal segments along a TE
   path.  While the more classical BIER is mainly a multicast technology
   that typically leverages a unicast distributed control plane through
   IGP extensions, BIER-TE is mainly a unicast technology that leverages
   a central computation to setup path, compute segments and install the
   mapping described
   in the intermediate nodes. Section 5.1.5 discusses the
   applicability of BIER-TE for replication, traceability and OAM
   operations in DetNet.

   Bit-Indexed Explicit Replication (BIER) layer may be considered to be
   included into Deterministic Networking data plane solution.
   Encapsulation 5.1.4.

   The encapsulation of a BIER packet in an MPLS network presented is shown in
   Figure 8
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     |                   Label Stack Element                         |
     |                   Label Stack Element                         |
     |              BIER-MPLS label          |     |1|               |
     |0 1 0 1|  Ver  |  Len  |              Entropy                  |
     |                BitString  (first 32 bits)                     ~
     ~                                                               ~
     ~                BitString  (last 32 bits)                      |
     |OAM|     Reserved      | Proto |            BFIR-id            |

                Figure 8: BIER packet in MPLS encapsulation  Solution description

   The DetNet may be presented in BIER as

   A distinctive BIER payload type with (with its own Proto(col) ID.  Then it is likely that DetNet will have the ID) would be
   created for DetNet, providing a header that would identify:

   o  Version;
   o  Sequence Number;
   o  Timestamp;
   o  Payload type, e.g. data vs. OAM.

   A DetNet node, collocated with BFIR, a BFIR (Bit-Forwarding Ingress Router)
   may use multiple BIER sub-domains to create replicated flows.
   Downstream DetNet nodes, collocated with
   BFER, BFER (Bit-Forwarding Ingress
   Router) would terminate redundant flows based on Sequence Number and/or and/
   or Timestamp information.  Such  Thus a DetNet node may be collocated with
   a BFER in one BIER sub- domain and with a BFIR in another.  Thus another, and a
   DetNet flow would could traverse several BIER sub-domains.

                                  |  A  |
                                   /   \
                                  .     .
                                 /       .
                                .         \
                               /           .
                              .             .
                             /               \
                        +-----+             +-----+
                        |  B  |             |  C  |
                        +-----+             +-----+
                         /   \               /   \
                        .     .             .     .
                       /       \           .       .
                      .         .         /         \
                     /           \       .           .
                    .             .     .             .
                   /               \   /               \
               +-----+            +-----+           +-----+
               |  D  |            |  E  |           |  F  |
               +-----+            +-----+           +-----+
                  \                .  .               /
                   .              .    .             .
                    \            .      .           .
                     .          .        .         /
                      \        .          .       .
                        .     .            .     .
                         \   .              .   /
                        +-----+            +-----+
                        |  G  |            |  H  |
                        +-----+            +-----+

                      Figure 9: DetNet in BIER domain

   Consider a DetNet flow that must traverse BIER enabled domain from A
   to G and H.  DetNet may use three BIER subdomains:

   o  A-B-D-E-G (dash-dot): A is BFIR, E and G are BFERs,
   o  A-C-E-F-H (dash-double-dot): A is BFIR, E and H are BFERs,
   o  E-G-H (dotted): E is BFIR, G and H are BFERs.

   DetNet node A sends DetNet into red and purple BIER sub-domains.
   DetNet node E receives DetNet packet and sends into green sub-domain
   while terminating duplicates and those that are deemed too-late. "too-late".

   DetNet nodes G and H receive DetNet flows, terminate duplicates and
   those that are too-late.  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      BIER over MPLS network encapsulation (will refer as "BIER ("BIER over
      MPLS" further for short), MPLS"), Figure 8,
      is being defined [I-D.  ietf-
      bier-mpls-encapsulation] [I-D.ietf-bier-mpls-encapsulation] within the
      BIER working group.

   #2 Flow identification (M)

      Flow identification and separation can be achieved through use of
      BIER domains and/or Entropy value in the BIER over MPLS, Figure 8.

   #4 Explicit routes (M)

      Explicit routes may be used as underlay for BIER domain.  BIER
      underlay may be calculated using PCE and instantiated using any
      southbound mechanism.

   #5 Flow duplication and merging (M/W)

      Packet replication, as indicated by its name, is a core function
      of the Bit-Indexed Explicit Replication.  Elimination of the
      duplicates and/or too-late packets cannot be done within BIER sub-
      domain but may be done at DetNet overlay at the edge of the BIER

      [Editor's note: how about the flow merging?]

   #6 Operations, Administration and Maintenance (M/W)

      BIER over MPLS guarantees that OAM is fate-sharing, i.e. in-band
      with a data flow being monitored or measured.  Additionally, BIER
      over MPLS enables passive performance measurement, e.g. with the
      marking method [I-D.mirsky-bier-pmmm-oam].  Some  Existing OAM protocols,
      e.g. protocols
      can be applied and used in BIER over MPLS as demonstrated in
      [I-D.ooamdt-rtgwg-oam-gap-analysis], while new protocols are being
      worked on, e.g. ping/traceroute [I-D.kumarzheng-bier-ping] or Path
      MTU Discovery [I-D.mirsky-bier-path-mtu-discovery].

   #8 Class and quality of service capabilities (M/W)

      Class of Service can be inherited from the underlay of the
      particular BIER sub-domain.  Quality of Service, i.e. scheduling
      and bandwidth reservations can be used among other constrains constraints in
      calculating explicit path paths for the BIER sub-domain's underlay.

   #9 Packet traceability (W)

      Ability to do passive performance measurement by using OAM field
      of the BIER over MPLS, Figure 8, is unmatched and significantly
      simplifies truly passive tracing of selected flows and packets
      within them.

   #10 Technical maturity (W)

      The BIER over MPLS is nearing finalization within the BIER WG and
      several experimental implementations are expected soon.  Summary

   BIER over MPLS supports a significant portion of the identified
   DetNet data plane requirements, including controlled packet
   replication, traffic engineering, while some requirements, e.g.
   duplicate and too-late packet elimination may be realized as function
   of the DetNet overlay.  BIER over MPLS is a viable candidate as the
   DetNet Transport layer in MPLS networks.

5.1.5.  BIER - Traffic Engineering (BIER-TE)

   An alternate use of Bit-Indexed Explicit Replication (BIER) uses bits
   in the BitString to represent adjacencies as opposed to destinations,
   as discussed in BIER Traffic Engineering (TE)

   The proposed function of BIER-TE in the DetNet data plane is to
   control the process of replication and elimination, as opposed to the
   identification of the flows or and the sequencing of packets within a

   At the path ingress, BIER-TE identifies the adjacencies that are
   activated for this packet (under the rule of the controller).  At the
   egress, BIER-TE is used to identify the adjacencies where
   transmission failed.  This information is passed to the controller,
   which in turn can modify the active adjacencies for the next packets.

   The value is that the replication can be controlled and monitored in
   a loop that may involve an external controller, with the granularity
   of a packet and an adjacency .  Solution description

   BIER-TE enables to activate the replication and elimination functions
   in a manner that is abstract to the data plane forwarding
   information.  An adjacency, which is represented by a bit in the BIER
   header, can correspond in the data plane to an Ethernet hop, a Label
   Switched Path, or it can correspond to an IPv6 loose or strict source
   routed path.

   In a nutshell, BIER-TE is used as follows:

   o  A controller computes a complex path, sometimes called a track,
      which takes the general form of a ladder.  The steps and the side
      rails between them are the adjacencies that can be activated on
      demand on a per-packet basis using bits in the BIER header.

                            ===> (A) ====> (C) ====
                          //     ^ |       ^ |     \\
              ingress (I)        | |       | |       (E) egress
                          \\     | v       | v     //
                            ===> (B) ====> (D) ====

      Figure 10: Ladder Shape with replication and elimination Points

   o  The controller assigns a BIER domain, and inside that domain,
      assigns bits to the adjacencies.  The controller assigns each bit
      to a replication node that sends towards the adjacency, for
      instance the ingress router into a segment that will insert a
      routing header in the packet.  A single bit may be used for a step
      in the ladder, indicating the other end of the step in both

                            ===> (A) ====> (C) ====
                          // 1   ^ |  4    ^ |   7 \\
              ingress (I)        |2|       |6|       (E) egress
                          \\ 3   | v  5    | v   8 //
                            ===> (B) ====> (D) ====

                         Figure 11: Assigning Bits

   o  The controller activates the replication by deciding the setting
      of the bits associated with the adjacencies.  This decision can be
      modified at any time, but takes the latency of a controller round
      trip to effectively take place.  Below is an example that uses
      replication and elimination to protect the A->C adjacency.

            | Bit # | Adjacency | Owner | Example Bit Setting |
            |   1   |    I->A   |   I   |          1          |
            |   2   |    A->B   |   A   |          1          |
            |       |    B->A   |   B   |                     |
            |   3   |    I->C   |   I   |          0          |
            |   4   |    A->C   |   A   |          1          |
            |   5   |    B->D   |   B   |          1          |
            |   6   |    C->D   |   C   |          1          |
            |       |    D->C   |   D   |                     |
            |   7   |    C->E   |   C   |          1          |
            |   8   |    D->E   |   D   |          0          |

                replication and elimination Protecting A->C

                     Table 1: Controlling Replication

   o  The BIER header with the controlling BitString is injected in the
      packet by the ingress node of the deterministic path.  That node
      may act as a replication point, in which case it may issue
      multiple copies of the packet

                          ====>  Repl ===> Elim ====
                       //         |         ^        \\
               ingress            |         |           egress
                                  v         |
                                 Fwd ====> Fwd

                      Figure 12: Enabled Adjacencies

   o  For each of its bits that is set in the BIER header, the owner
      replication point resets the bit and transmits towards the
      associated adjacency; to achieve this, the replication point
      copies the packet and inserts the relevant data plane information,
      such as a source route header, towards the adjacency that
      corresponds to the bit
                      | Adjacency | BIER BitString |
                      |    I->A   |    01011110    |
                      |    A->B   |    00011110    |
                      |    B->D   |    00010110    |
                      |    D->C   |    00010010    |
                      |    A->C   |    01001110    |

               BitString in BIER Header as Packet Progresses

                        Table 2: BIER-TE in Action

   o  Adversely, an elimination node on the way strips the data plane
      information and performs a bitwise AND on the BitStrings from the
      various copies of the packet that it has received, before it
      forwards the packet with the resulting BitString.

                      | Operation | BIER BitString |
                      |    D->C   |    00010010    |
                      |    A->C   |    01001110    |
                      |           |    --------    |
                      |  AND in C |    00000010    |
                      |           |                |
                      |    C->E   |    00000000    |

                BitString Processing at Elimination Point C

                    Table 3: BIER-TE in Action (cont.)

   o  In this example, all the transmissions succeeded and the BitString
      at arrival has all the bits reset - note that the egress may be an
      Elimination Point in which case this is evaluated after this node
      has performed its AND operation on the received BitStrings).

               | Failing Adjacency | Egress BIER BitString |
               |        I->A       |       Frame Lost      |
               |        I->B       |       Not Tried       |
               |        A->C       |        00010000       |
               |        A->B       |        01001100       |
               |        B->D       |        01001100       |
               |        D->C       |        01001100       |
               |        C->E       |       Frame Lost      |
               |        D->E       |       Not Tried       |

                       BitString indicating failures

                    Table 4: BIER-TE in Action (cont.)

   o  But if a transmission failed along the way, one (or more) bit is
      never cleared.  Table 4 provides the possible outcomes of a
      transmission.  If the frame is lost, then it is probably due to a
      failure in either I->A or C->E, and the controller should enable
      I->B and D->E to find out.  A BitString of 00010000 indicates
      unequivocally a transmission error on the A->C adjacency, and a
      BitString of 01001100 indicates a loss in either A->B, B->D or
      D->C; enabling D->E on the next packets may provide more
      information to sort things out.

   In more details:

   The BIER header is of variable size, and a DetNet network of a
   limited size can use a model with 64 bits if 64 adjacencies are
   enough, whereas a larger deployment may be able to signal up to 256
   adjacencies for use in very complex paths.  Figure 8 illustrates a
   BIER header as encapsulated within MPLS.  The format of this header
   is common to BIER and BIER-TE.

   For the DetNet data plane, a replication point is an ingress point
   for more than one adjacency, and an elimination point is an egress
   point for more than one adjacency.

   A pre-populated state in a replication node indicates which bits are
   served by this node and to which adjacency each of these bits
   corresponds.  With DetNet, the state is typically installed by a
   controller entity such as a PCE.  The way the adjacency is signaled
   in the packet is fully abstracted in the bit representation and must
   be provisioned to the replication nodes and maintained as a local
   state, together with the timing or shaping information for the
   associated flow.

   The DetNet data plane uses BIER-TE to control which adjacencies are
   used for a given packet.  This is signaled from the path ingress,
   which sets the appropriate bits in the BIER BitString to indicate
   which replication must happen.

   The replication point clears the bit associated to the adjacency
   where the replica is placed, and the elimination points perform a
   logical AND of the BitStrings of the copies that it gets before

   As is apparent in the examples above, clearing the bits enables to
   trace a packet to the replication points that made any particular
   copy.  BIER-TE also enables to detect the failing adjacencies or
   sequences of adjacencies along a path and to activate additional
   replications to counter balance the failures.

   Finally, using the same BIER-TE bit for both directions of the steps
   of the ladder enables to avoid replication in both directions along
   the crossing adjacencies.  At the time of sending along the step of
   the ladder, the bit may have been already reset by performing the AND
   operation with the copy from the other side, in which case the
   transmission is not needed and does not occur (since the control bit
   is now off).  Analysis and Discussion

   #1 Encapsulation and overhead (W/M)

      The size of the BIER header depends on the number of segments in
      the particular path.  It is very concise considering the amount of
      information that is carried (control of replication, traceability,
      and measurement of the reliability of the segments).

   #2 Flow identification (N)

      Some fields in the BIER header could be used to identify the flows
      but they are not the primary purpose, so it's probably not a good

   #4 Explicit routes (N)

      A separate procedure must be used to set up the paths and allocate
      the bits for the adjacencies.  The bits should be distributed as a
      form of tag by the route setup protocol.  This procedure requires
      more work and is separate from the data plane method that is
      described here.

   #5 Flow duplication and merging M/W)

      The bitmap expresses in a very concise fashion which replication
      and merging (and elimination) should take place for a given
      packet.  It also enables to control that process on a per packet
      basis, depending on the loss that it enables to measure.  The net
      result is that a complex path may be installed with all the
      possibilities and that the decision of which possibilities are
      used is controlled in the data plane.

   #6 Operations, Administration and Maintenance (W)

      The setting of the bits at arrival enables to determine which
      adjacencies worked and which did not, enabling a dynamic control
      of the replication and elimination process.  This is a form of OAM
      that is in-band with the data stream as opposed to leveraging
      separate packets, which is a more accurate information on the
      reliability of the link for the user.

   #8 Class and quality of service capabilities (N)

      BIER-TE does not signal that explicitly.

   #9 Packet traceability (W)

      This is a strong point of the solution.  The solution enables to
      determine which is the current segment that a given packet is
      expected to traverse, which node performed the replication and
      which should perform the elimination if any

   #10 Technical maturity (W)

      Some components of the technology are more mature, e.g. segment
      routing and BIER.  Yet, the overall solution has never been
      deployed as is not fully defined.  It should be noted that the
      definition of the BIER-TE solution is outside the scope of the
      DetNet WG charter.  Summary

   BIER-TE occupies a particular position in the DetNet data plane.  In
   the one hand it is optional, and only useful if replication and
   elimination is taking place.  In the other hand, it has unique
   capabilities to:

   o  control which replication take place on a per packet basis, so
      that replication points can be configured but not actually
   o  trace the replication activity and determine which node replicated
      a particular packet
   o  measure the quality of transmission of the actual data packet
      along the replication segments and use that in a control loop to
      adapt the setting of the bits and maintain the reliability.

   However, as noted earlier, BIER-TE is not yet fully specified and the
   required specification work is outside the scope of the current
   DetNet WG charter.

5.2.  DetNet Service layer technologies

5.2.1.  Generic Routing Encapsulation (GRE)  Solution description

   Generic Routing Encapsulation (GRE) [RFC2784] provides an
   encapsulation of an arbitrary network layer protocol over another
   arbitrary network layer protocol.  The encapsulation of a GRE packet
   can be found in Figure 13. 10.

                     |        Delivery Header        |
                     |          GRE Header           |
                     |         Payload packet        |

                 Figure 13: 10: Encapsulation of a GRE packet

   Based on RFC2784, [RFC2890] further includes sequencing number and
   Key in optional fields of the GRE header, which may help to transport
   DetNet traffic flows over IP networks.  The format of a GRE header is
   presented in Figure 14. 11.

    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 2
    |C| |K|S|  Reserved0      | Ver |          Protocol Type          |
    |      Checksum (optional)      |        Reserved1 (Optional)     |
    |                        Key (optional)                           |
    |                  Sequence Number (optional)                     |

                     Figure 14: 11: Format of a GRE header  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      GRE can provide encapsulation at the service layer over the
      transport layer.  A new protocol type for DetNet traffic should be
      allocated as an "Ether Type" in [RFC3232] and in IANA Ethernet
      Numbers [5].  The fixed header of a GRE packet is 4 octets while
      the maximum header is 16 octets with optional fields in Figure 14. 11.

   #2 Flow identification (W)

      There is no flow identification field in GRE header.  However, it
      can rely on the flow identification mechanism applied in the
      delivery protocols, such as flow identification stated in IP
      Sections 5.1.1 and 5.1.2 when the delivery protocols are IPv6 and
      IPv4 respectively.  Alternatively, the Key field can also be
      extended to carry the flow identification.  The size of Key field
      is 4 octets.

   #3 Packet sequencing and duplicate elimination (M/W)

      As stated in Section 5.2.1, GRE provides an optional sequencing
      number in its header to provide sequencing services for packets.
      The size of the sequencing number is 32 bits.  The GRE header
      could be extended to indicate the duplicated packets by defining a
      flag in reserved fields or using the sequencing number of a flow.

   #5 Flow duplication and merging (W/N)

      GRE has no flow/packet replication and merging support in its
      header.  It can use the transport IPv4/IPv6 protocols at the
      transport layer to replicate the packets and take the different
      routes as discussed in Section 5.1.1 and Section 5.1.2.

   #6 Operations, Administration and Maintenance (M)

      GRE uses the network management provided by the IP protocols as
      transport layer.

   #8 Class and quality of service capabilities (W)

      For the class of service capability, an optional code point field
      to indicate CoS of the traffic could be added into the GRE header.
      Otherwise, GRE can reuse the class and quality of service of
      delivery protocols at transport layer such as IPv6 and IPv4 stated
      in Section 5.1.1 and Section 5.1.2.

   #10 Technical maturity (M)

      GRE has been developed over 20 years.  The delivery protocol
      mostly used is IPv4, while the IPv6 support for GRE is to be
      standardized now in IETF as [RFC7676].  Due to its good
      extensibility, GRE has also been extended to support network
      virtualization in Data Center, which is NVGRE [RFC7637].  Summary

   As a tunneling protocol, GRE can encapsulate a wide variety of
   network layer protocols over another network layer, which can
   naturally serve as the service layer protocol for DetNet.  Currently,
   it supports a portion of the Detnet service layer criteria, and still
   some are not fully supported but can be incrementally added or
   supported by delivery protocols at as the transport layer.  In
   general, GRE can be a choice as the DetNet service layer and can work
   with IPv6 and IPv4 as the DetNet Transport layer.

5.2.2.  MPLS-based Services for DetNet

   MPLS based technologies supports support both the DetNet Service and DetNet
   Transport layers.  This, as well as a general overview of MPLS, is
   covered above in Section 5.1.3.  These  Following sections focus on the
   DetNet Service Layer it which provides client service adaption, via
   Pseudowires Section 5.2.3 and via native and other label-like
   mechanisms such as EPVN in Section 5.2.4.  A representation of these
   options was previously discussed and is shown in Figure 7.

   The following text is adapted from [RFC5921]:

      The MPLS native service adaptation functions interface the client
      layer network service to MPLS.  For Pseudowires, these adaptation
      functions are the payload encapsulation described in Section 4.4
      of [RFC3985] and Section 6 of [RFC5659].  For network layer client
      services, the adaptation function uses the MPLS encapsulation
      format as defined in [RFC3032].

      The purpose of this encapsulation is to abstract the data plane of
      the client layer network from the MPLS data plane, thus
      contributing to the independent operation of the MPLS network.

      MPLS may itself be a client of an underlying server layer.  MPLS
      can thus also be bounded by a set of adaptation functions to this
      server layer network, which may itself be MPLS.  These adaptation
      functions provide encapsulation of the MPLS frames and for the
      transparent transport of those frames over the server layer

      While MPLS service can provided on and a true end-system to end-
      system end-system
      basis, it's more likely that DetNet service will be provided over
      Pseudowires as described in Section 5.2.3 or via an EPVN-based
      service described in Section 5.2.4 .

      MPLS labels in the label stack may be used to identify transport
      paths, see Section 5.1.3, or as service identifiers.  Typically a
      single label is used for service identification.

      Packet sequencing mechanisms are added in client-related
      adaptation processing, see Sections 5.2.3 and 5.2.4.

      The MPLS client inherits its Quality of Service (QoS) from the
      MPLS transport layer, which in turn inherits its QoS from the
      server (sub-network) layer.  The server layer therefore needs to
      provide the necessary QoS to ensure that the MPLS client QoS
      commitments can be satisfied.

5.2.3.  Pseudo Wire Emulation Edge-to-Edge (PWE3)  Solution description

   Pseudo Wire Emulation Edge-to-Edge (PWE3) [RFC3985] or simply
   PseudoWires (PW) provide means of emulating the essential attributes
   and behaviour of a telecommunications service over a packet switched
   network (PSN) using IP or MPLS transport.  In addition to traditional
   telecommunications services such as T1 line or Frame Relay, PWs also
   provide transport for Ethernet service [RFC4448] and for generic
   packet service [RFC6658].  Figure 15 12 illustrate the reference PWE3
   stack model.

    +----------------+                      +----------------+
    |Emulated Service|                      |Emulated Service|
    |(e.g., Eth, ...)|<= Emulated Service =>|(e.g., Eth, ...)|
    +----------------+                      +----------------+
    |    Payload     |                      |    Payload     | CW,
    |  Encapsulation |<=== Pseudo Wire ====>|  Encapsulation | Timing,
    |                |                      |                | Seq., ..
    +----------------+                      +----------------+
    |PW Demultiplexer|                      |PW Demultiplexer|
    |   PSN Tunnel,  |<==== PSN Tunnel ====>|  PSN Tunnel,   | MPLS.
    | PSN & Physical |                      | PSN & Physical | L2TP,
    |     Layers     |                      |    Layers      | IP, ..
    +-------+--------+     ___________      +---------+------+
            |             /           \               |
            +============/     PSN     \==============+
                         \             /

              Figure 15: 12: PWE3 protocol stack reference model

   PWs appear as a good data plane solution alternative for a number of
   reasons.  PWs are a proven and deployed technology with a rich OAM
   control plane [RFC4447], and enjoy the toolbox developed for MPLS
   networks in a case of MPLS-based PSN.  Furthermore, PWs may have an
   optional Control Word (CW) as part of the payload encapsulation
   between the PSN and the emulated service that is, for example,
   capable of frame sequencing and duplicate detection.  The
   encapsulation layer may also provide timing using RTP as described in
   Sections 5.2.2, 5.4.1 and 5.4.2 of [RFC3985] and utilized by
   [RFC4553][RFC5087].  Furthermore, advanced DetNet node functions are
   conceptually already supported by PW framework (with some added
   functional required), such as the DetNet Relay node modeled after the
   Multi-Segment PWE3 [RFC5254].

   PWs can be also used if the PSN is IP, which enables the application
   of PWs in networks that do not have MPLS enabled in their core
   routers.  One approach to provide PWs over IP is to provide MPLS over
   IP in some way and then leverage what is available for PWs over MPLS.
   The following standard solutions are available both for IPv4 and IPv6
   to follow this approach.  The different solutions have different
   overhead as discussed in the following subsection.  The MPLS-in-IP
   encapsulation is specified by [RFC4023].  The IPv4 Protocol Number
   field or the IPv6 Next Header field is set to 137, which indicates an
   MPLS unicast packet.  (The use of the MPLS-in-IP encapsulation for
   MPLS multicast packets is not supported.)  The MPLS-in-GRE
   encapsulation is specified in [RFC4023], where the IP header (either
   IPv4 or IPv6) is followed by a GRE header, which is followed by an
   MPLS label stack.  The protocol type field in the GRE header is set
   to MPLS Unicast (0x8847) or Multicast (0x8848).  MPLS over L2TPv3
   over IP encapsulation is specified by [RFC4817].  The MPLS-in-UDP
   encapsulation is specified by [RFC7510], where the UDP Destination
   Port indicates tunneled MPLS packet and the UDP Source Port is an
   entropy value that is generated by the encapsulator to uniquely
   identify a flow.  MPLS-in-UDP encapsulation can be applied to enable
   UDP-based ECMP (Equal-Cost Multipath) or Link Aggregation.  All these
   solutions can be secured with IPsec [RFC4303].  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      PWs offer encapsulation services practically for practically any types
      type of
      payloads payload over any PSN.  New PW types need a code point
      allocation [RFC4446] and in some cases an emulated service
      specific document.

      Specifically in the case of the MPLS PSN the PW encapsulation
      overhead is minimal.  Typically minimum two labels and a CW is
      needed, which totals to 12 octets.  PW type specific handling
      might, however, allow optimizations on the emulated service in the
      provider edge (PE) device's native service processing (NSP) /
      forwarder function.  These optimizations could be used, for
      example, to reduce header overhead.  Ethernet PWs already have
      rather low overhead [RFC4448].  Without a CW and VLAN tags the
      Ethernet header gets reduced to 14 octets (minimum Ethernet header
      overhead is 26).

      The overhead is somewhat bigger in case of IP PSN if an MPLS over
      IP solution is applied to provide PWs.  IP adds at least 20 (IPv4)
      or 40 (IPv6) bytes overhead to the PW over MPLS overhead;
      furthermore, the GRE, L2TPv3, or UDP header has to be taken into
      account if any of these further encapsulations is used.

   #2 Flow identification (M)

      PWs provide multiple layers of flow identification, especially in
      the case of the MPLS PSN.  The PWs are typically prepended with an
      endpoint specific PW label that can be used to identify a specific
      PW per endpoint.  Furthermore, the MPLS PSN also uses one or more
      labels to transport packets over a specific label switched paths
      (that then would carry PWs).  So, a DetNet flow can be identified
      in this example by the service and transport layer labels.  IP
      (and other) PSNs may need other mechanisms, such as, UDP port
      numbers, upper layer protocol header (like RTP) or some IP
      extension header to provide required flow identification.

   #3 Packet sequencing and duplicate elimination (M)

      As mentioned earlier PWs may contain an optional CW that is able
      to provide sequencing services.  The size of the sequence number
      in the generic CW is 16 bits, which might be, depending on the
      used link and DetNet flow speed be too little.  The PW duplicate
      detection mechanism is already conceptually specified [RFC3985]
      but no emulated service makes use of it currently.

   #5 Flow duplication and merging (W)

      PWs could use a (extended) version of existing transport layer
      provided protection mechanisms (e.g., hitless 1+1 protection) for
      both flow duplication and flow merging.  The service layer has to
      provide the functionality to map DetNet flows into appropriate
      transport leyer connection, though. layer connection.

   #6 Operations, Administration and Maintenance (M/W)

      PWs have rich control plane for OAM and in a case of the MPLS PSN
      enjoy the full control plane toolbox developed for MPLS network
      OAM likewise IP PSN have has the full toolbox of IP network OAM tools.
      There could be, however, need for deterministic networking
      specific extensions for the mentioned control planes.

   #8 Class and quality of service capabilities (M/W)

      In a case of IP PSN the 6-bit differentiated services code point
      (DSCP) field can be used for indicating the class of service
      [RFC2474] and 2-bit field reserved for the explicit congestion
      notification (ECN) [RFC3168].  Similarly, in a case of MPLS PSN,
      there are 3-bit traffic class field (TC) [RFC5462] in the label
      reserved for for both Explicitly TC-encoded-PSC LSPs (E-LSP)
      [RFC3270] and ECN [RFC5129].  Due to the limited number of bits in
      the TC field, their use for QoS and ECN functions is restricted
      and intended to be flexible.  Although the QoS/CoS mechanism is
      already in place some clarifications may be required in the
      context of deterministic networking flows, for example, if some
      specific mapping between bit fields have to be done.

      When PWs are used over MPLS, MPLS LSPs can be used to provide both
      CoS (E-LSPs and L-LSPs) and QoS (dedicated TE LSPS).

   #10 Technical maturity (M)

      PWs, IP and MPLS are proven technologies with wide variety of
      deployments and years of operational experience.  Furthermore, the
      estimated work for missing functionality (packet replication and
      elimination) does not appear to be extensive, since the existing
      protection mechanism already get gets close to what is needed from the
      deterministic networking data plane solution.  Summary

   PseudoWires appear to be a strong candidate as the deterministic
   networking data plane solution alternative for the DetNet Service
   layer.  The strong points are the technical maturity and the
   extensive control plane for OAM.  This holds specifically for MPLS-
   based PSN.

   Extensions are required to realize the packet replication and
   duplicate detection features of the deterministic networking data

5.2.4.  MPLS-Based Ethernet VPN (EVPN)  Solution description

   MPLS-Based Ethernet VPN (EVPN), in the form documented in [RFC7432]
   and [RFC7209], is an increasingly popular approach to delivering
   MPLS-based Ethernet services and is designed to be the successor to
   Virtual Private LAN Service (VPLS), [RFC4664].

   EVPN provides client adaptation and reuses the MPLS data plane
   discussed above in Section 5.2.2.  While not required, the PW Control
   Word is also used.  EVPN control is via BGP, [RFC7432], and may use
   TE-LSPs, e.g., controlled via [RFC3209] for MPLS transport.
   Additional EVPN related RFCs and in progress drafts are being
   developed by the BGP Enabled Services Working Group [6].  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      EVPN generally uses a single MPLS label stack entry to support its
      client adaptation service.  The optional addition of a second
      label is also supported.  In certain cases PW Control Word may
      also be used.

   #2 Flow identification (W)

      EVPN currently uses labels to identify flows per {Ethernet Segment
      Identifier, VLAN} or per MAC level.  Additional definition will be
      needed to standardize identification of finer granularity DetNet
      flows as well as mapping of TSN services to DetNet Services.

   #3 Packet sequencing and duplicate elimination (M)

      Like MPLS, EVPN generally orders packets similar to Ethernet.
      Reordering is possible primarily during path changes and
      protection switching.  In order to avoid misordering due to ECMP,
      EVPN uses the "Preferred PW MPLS Control Word" [RFC4385] (in which
      case EVPN inherits this function from PWs) or the entropy labels

      If additional ordering mechanisms are required, such mechanisms
      will need to be defined.

   #5 Flow duplication and merging (M/W)

      EVPN relies on the MPLS layer for all protection functions.  See
      Section 5.1.3 and Section 5.2.2.  Some extensions, either at the
      EVPN or MPLS levels, will be need to support those DetNet
      applications which require true hitless (i.e., zero loss) 1+1
      protection switching.  (Network coding may be an interesting
      alternative to investigate to delivering such hitless loss
      protection capability.)

   #6 Operations, Administration and Maintenance (M/W)

      Nodes supporting EVPN may participate in either or both Ethernet
      level and MPLS level OAM.  It is likely that it may make sense to
      map or adapt the OAM functions at the different levels, but such
      has yet to be defined.  [RFC6371] provides some useful background
      on this topic.

   #8 Class and quality of service capabilities (M/W)

      EVPN is largely silent on the topics of CoS and QoS, but the 802.1
      TSN Ethernet and existing MPLS TE mechanisms can be directly used.
      The inter-working of such is new work and within the scope of
      DetNet.  The existing MPLS mechanisms include both CoS (E-LSPs and
      L-LSPs) and QoS (dedicated TE LSPs).

   #10 Technical maturity (M)
      EVPN is a second (or third) generation MPLS-based L2VPN service
      standard.  From a data plane standpoint it makes uses of existing
      MPLS data plane mechanisms.  The mechanisms have been widely
      implemented and deployed.  Summary

   EVPN is the emerging successor to VPLS.  EVPN is standardized,
   implemented and deployed.  It makes use of the mature MPLS data
   plane.  While offering a mature and very comprehensive set of
   features, certain DetNet required features are not fully/directly
   supported and additional standardization in these areas are needed.
   Examples include: mapping CoS and QoS; use of labels per DetNet flow,
   and hitless 1+1 protection.

5.2.5.  Higher layer header fields

   Fields of headers belonging to higher OSI layers can be used to
   implement functionality that is not provided e.g., by the IPv6 or
   IPv4 header fields.  However, this approach cannot be always applied,
   e.g., due to encryption.  Furthermore, even if this approach is
   applicable, it requires deep packet inspection from the routers and
   switches.  There are implementation dependent limits how far into the
   packet the lookup can be done efficiently in the fast path.  When
   encryption is not used, a safe bet is generally between 128 and 256
   octets for the maximum lookup depth.  Various higher layer protocols
   can be applied.  Some examples are provided here for the sequence
   numbering feature (Section 4.3).  TCP

   The TCP header includes a sequence number parameter, which can be
   applied to detect and eliminate duplicate packets if DetNet service
   protection is used.  As the TCP header is right after the IP header,
   it does not require very deep packet inspection; the 4-byte sequence
   number is conveyed by bits 32 through 63 of the TCP header.  In
   addition to sequencing, the TCP header also contain source and
   destination port information that can be used for assisting the flow
   identification.  RTP  Solution Description

   Real-time Transport Protocol (RTP) [RFC3550] is often used to deliver
   time critical traffic in IP networks.  RTP is typically carried on
   top of UDP/IP.  However, as noted earlier in Section 5.2.3
   PseudoWires also have a well-defined way of embedding and
   transposting RTP header headers as part of its payload encapsulation headers/
   headers/sub-layer.  RTP is also augmented by its own control protocol
   RTCP, which monitors of the data delivery and provides minimal control
   and identification functionality.  RTCP packets do not carry "media
   payload".  Although both RTP and RTCP are typically used with UDP/IP
   transport they are designed to be independent of the underlying
   transport and network layers.

   The RTP header includes a 2-byte sequence number, which can be used
   to detect and eliminate duplicate packets if DetNet service
   protection is used.  The sequence number is conveyed by bits 16
   through 31 of the RTP header.  In addition to the sequence number the
   RTP header has also timestamp field (bits 32 through 63) that can be
   useful for time synchronization purposes.  Furthermore, the RTP
   header has also one or more synchronization sources (bits starting
   from 64) that can potentially be useful for flow identification
   purposes.  Analysis and Discussion

   #1 Encapsulation and overhead (M)

      RTP adds minimum 12 octets of header overhead.  Typically 8 octets
      overhead of UDP header has to be also added, at least in a case
      when RTP is transported over IP.  Although RTCP packets do not
      contribute to the media payload transport they still consume
      overall network capacity, since all participants to an RTP session
      including sourcess and multicast session destinations are expected
      to send RTCP reports.

   #2 Flow identification (M)

      The RTP header contains a synchronization source (SSRC)
      identifier.  The intent is that no two synchronization sources
      within the same RTP session has have the same SSRC identifier.

   #3 Packet sequencing and duplicate elimination (M)

      The RTP header contains a 16 bit sequence number.  The sequence
      number can be also used to detect duplicate packets.

   #5 Flow duplication and merging (M/W)

      RTP has precedence of being used for hitless protection switching
      [ST20227], which essentially is equivalent to DetNet service
      protection.  Furthermore, recent work in IETF for RTP stream
      duplication [RFC7198] as a mechanism to protect media flows from
      packet loss is again equivalent to Detnet service protection.

   #6 Operations, Administration and Maintenance (M)

      RTP has its own control protocol RTCP for (minimal) management and
      stream monitoring purposes.  Existing IP OAM tools can directly
      leveraged when RTP is deployed over IP transport.

   #8 Class and quality of service capabilities (M/W)

      TBD.  [Editor's note: relies on lower layers to provide CoS/QoS]

   #10 Technical maturity (M)

      RTP has been deployed and used in large commercial systems for
      over ten years and can be considered a mature technology.  Summary

   RTP appears to be a good candidate as the deterministic networking
   data plane solution alternative for the DetNet Service layer.  The
   strong points are the technical maturity and the fact it was designed
   for transporting time-sensitive payload from the beginning.  RTP is
   specifically well suited to be used with (UDP)/IP transport.

   Extensions may be required to realize the packet replication and
   duplicate detection features of the deterministic networking data
   plane.  However, there is already precedence of similar solutions
   that could potentially be leveraged [ST20227][RFC7198].

6.  Summary of data plane alternatives

   The following table summarizes the criteria (Section 4) used for the
   evaluation of data plane options.

                       Applicability per Alternative

         | Item # |                   Meaning                   |
         |   #1   |          Encapsulation and overhead         |
         |   #2   |             Flow identification             |
         |   #3   | Packet sequencing and duplicate elimination |
         |   #4   |               Explicit routes               |
         |   #5   |         Flow duplication and merging        |
         |   #6   |  Operations, Administration and Maintenance |
         |   #8   |  Class and quality of service capabilities  |
         |   #9   |             Packet traceability             |
         |  #10   |              Technical maturity             |

                       Table 5: 1: Evaluation criteria (#7 obsoleted)

   There is no single technology that could meet all the criteria on its
   own.  Distinguishing the DetNet Service and the DetNet Transport, as
   explained in (Section 3), allows a number of combinations, which can
   meet most of the criteria.  There is no room here to evaluate all
   possible combinations.  Therefore, only some combinations are
   highlighted here, which are selected based on the number of criteria
   that are met and the maturity of the technology (#10).

   The following table summarizes the evaluation of the data plane
   options that can be used for the DetNet Transport Layer against the
   evaluation criteria.  Each value in the table is from the
   corresponding section.

                  Applicability per Transport Alternative


         | Solution | #1 | #2 | #4 | #5  | #6  | #8  | #9 | #10 |
         |   IPv6   | M  | W  | W  | W   | M   | W   | W  | M/W |
         |   IPv4   | M  | W  | W  | W/N | M   | M/W | W  | M/W |
         |   MPLS   | M  | M  | M  | M/W | M   | M/W | M  | M   |
         |   BIER   | M  | M  | M  | M/W | M/W | M/W | M  | W   |
         | BIER-TE  | W/M | N  | N  | M/W | W   | N   | W  | W   |

                    Summarizing Transport capabilities

                      Table 6: 2: DetNet Transport Layer

   The following table summarizes the evaluation of the data plane
   options that can be used for the DetNet Service Layer against the
   criteria evaluation criteria.  Each value in the table is from the
   corresponding section.

                   Applicability per Service Alternative

           | Solution | #1 | #2 | #3  | #5  | #6  | #8  | #10 |
           |   GRE    | M  | W  | M/W | W/N | M   | W   | M   |
           |   PWE3   | M  | M  | M   | W   | M/W | M/W | M   |
           |   EVPN   | M  | W  | M   | M/W | M/W | M/W | M   |
           |   RTP    | M  | M  | M   | M/W | M   | M/W | M   |

                     Summarizing Service capabilities

                       Table 7: 3: DetNet Service Layer

   PseudoWire (Section 5.2.3) is a technology that is mature and meets
   most of the criteria for the DetNet Service layer as shown in the
   table above.  From upper layer protocols PWs or RTP can be a
   candidate for non-MPLS PSNs.  The identified work for PWs is to
   figure out how to implement duplicate detection for these protocols
   (e.g., based on [RFC3985]).  In a case of RTP there is precedence of
   implementing packet duplication and duplicate elimination

   PWs can be carried over MPLS or IP.  MPLS is the most common
   technology that is used as PSN for PseudoWires; furthermore, MPLS is
   a mature technology and meets most DetNet Transport layer criteria.
   IPv[46] can be also used as PSN and both are mature technologies,
   although both generally only support CoS (DiffServ) in deployed
   networks.  RTP is independent of the underlying transport technology
   and network.  However, it is well suited for UDP/IP transport or
   embedded as a part of the PseudoWire timing sub-layer.

7.  Security considerations

   This document does not add any new security considerations beyond
   what the referenced technologies already have.

8.  IANA Considerations

   This document has no IANA considerations.

9.  Acknowledgements

   The author(s) ACK and NACK.

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

      Jouni Korhonen
      Janos Farkas
      Norman Finn
      Olivier Marce
      Gregory Mirsky
      Pascal Thubert
      Zhuangyan Zhuang

   Substantial contributions were received from:

      Balazs Varga (service model)

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

      Lou Berger
      Pat Thaler

10.  References

10.1.  Informative References

              Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Traffic
              Engineering for Bit Index Explicit Replication BIER-TE",
              draft-eckert-bier-te-arch-04 (work in progress), July

              Finn, N., Thubert, P., N. and M. Teener, P. Thubert, "Deterministic Networking
              Architecture", draft-finn-detnet-
              architecture-07 draft-finn-detnet-architecture-08 (work in
              progress), July August 2016.

              Deering, D. and R.
              Hinden, R., "Internet Protocol, Version 6 (IPv6)
              Specification", draft-ietf-6man-rfc2460bis-05 draft-ietf-6man-rfc2460bis-06 (work in
              progress), June September 2016.

              Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
              J., Aries, E., Kosugi, T., Vyncke, E., and D. Lebrun,
              "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
              segment-routing-header-01 (work in progress), March 2016.

              Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
              S. Aldrin, "Multicast using Bit Index Explicit
              Replication", draft-ietf-bier-architecture-04 (work in
              progress), July 2016.

              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
              Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
              Explicit Replication in MPLS Networks", draft-ietf-bier-
              mpls-encapsulation-05 (work in progress), July 2016.

              Finn, N. and P. Thubert, "Deterministic Networking Problem
              Statement", draft-ietf-detnet-problem-statement-00 (work
              in progress), April 2016.

              Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
              and S. Vainshtein, "Residence Time Measurement in MPLS
              network", draft-ietf-mpls-residence-time-11 (work in
              progress), July 2016.

              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-09 (work in progress), July 2016.

              Perreault, S., Tsou, T., Zhou, C., and P. Fan, "Gap
              Analysis for IPv4 Sunset", draft-ietf-
              sunset4-gapanalysis-07 (work in progress), April 2015.

              Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
              and G. Mirsky, "BIER Ping and Trace", draft-kumarzheng-
              bier-ping-03 (work in progress), July 2016.

              Mirsky, G., Przygienda, T., and A. Dolganow, "Path Maximum
              Transmission Unit Discovery (PMTUD) for Bit Index Explicit
              Replication (BIER) Layer", draft-mirsky-bier-path-mtu-
              discovery-01 (work in progress), April 2016.

              Mirsky, G., Zheng, L., Chen, M., and G. Fioccola,
              "Performance Measurement (PM) with Marking Method in Bit
              Index Explicit Replication (BIER) Layer", draft-mirsky-
              bier-pmmm-oam-01 (work in progress), March 2016.

              Mirsky, G., Nordmark, E., Pignataro, C., Kumar, N., Kumar,
              D., Chen, M., Yizhou, L., Mozes, D., Networks, J., and i.
    , I.
              Bagdonas, "Operations, Administration and Maintenance
              (OAM) for Overlay Networks: Gap Analysis",
              draft-ooamdt-rtgwg-oam-gap-analysis-02 draft-ooamdt-
              rtgwg-oam-gap-analysis-02 (work in progress), July 2016.

              Kumar, N., Pignataro, C., Kumar, D., Mirsky, G., Chen, M.,
              Nordmark, E., Networks, J., and D. Mozes, "Overlay OAM
              Requirements", draft-ooamdt-rtgwg-ooam-requirement-01
              (work in progress), July 2016.

              IEEE, "Enhancements for Scheduled Traffic", 2016,

              IEEE 802.1, "IEEE 802.1Qca Bridges and Bridged Networks -
              Amendment 24: Path Control and Reservation", IEEE
              P802.1Qca/D2.1 P802.1Qca, June 2015,

              IEEE, "Cyclic Queuing and Forwarding", 2016,

              Finn, N., "Draft Standard for Local and metropolitan area
              networks - Seamless Redundancy", IEEE P802.1CB
              /D2.1 P802.1CB, December 2015,

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,

   [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, <>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <>.

   [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,

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              DOI 10.17487/RFC2784, March 2000,

   [RFC2890]  Dommety, G., "Key and Sequence Number Extensions to GRE",
              RFC 2890, DOI 10.17487/RFC2890, September 2000,

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,

   [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,

   [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,

   [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,

   [RFC3232]  Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
              by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
              January 2002, <>.

   [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,

   [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,

   [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,

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <>.

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

   [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,

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,

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

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446,
              DOI 10.17487/RFC4446, April 2006,

   [RFC4447]  Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
              G. Heron, "Pseudowire Setup and Maintenance Using the
              Label Distribution Protocol (LDP)", RFC 4447,
              DOI 10.17487/RFC4447, April 2006,

   [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,

   [RFC4553]  Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
              Agnostic Time Division Multiplexing (TDM) over Packet
              (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,

   [RFC4664]  Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
              2 Virtual Private Networks (L2VPNs)", RFC 4664,
              DOI 10.17487/RFC4664, September 2006,

   [RFC4817]  Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
              J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
              Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March
              2007, <>.

   [RFC4875]  Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
              Yasukawa, Ed., "Extensions to Resource Reservation
              Protocol - Traffic Engineering (RSVP-TE) for Point-to-
              Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
              DOI 10.17487/RFC4875, May 2007,

   [RFC5087]  Stein, Y(J)., Shashoua, R., Insler, R., and M. Anavi,
              "Time Division Multiplexing over IP (TDMoIP)", RFC 5087,
              DOI 10.17487/RFC5087, December 2007,

   [RFC5129]  Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
              Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January
              2008, <>.

   [RFC5254]  Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed.,
              "Requirements for Multi-Segment Pseudowire Emulation Edge-
              to-Edge (PWE3)", RFC 5254, DOI 10.17487/RFC5254, October
              2008, <>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <>.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space",
              RFC 5331, DOI 10.17487/RFC5331, August 2008,

   [RFC5332]  Eckert, T., Rosen, E., Ed., Aggarwal, R., and Y. Rekhter,
              "MPLS Multicast Encapsulations", RFC 5332,
              DOI 10.17487/RFC5332, August 2008,

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,

   [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, <>.

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586,
              DOI 10.17487/RFC5586, June 2009,

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              DOI 10.17487/RFC5659, October 2009,

   [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,

   [RFC5960]  Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
              Transport Profile Data Plane Architecture", RFC 5960,
              DOI 10.17487/RFC5960, August 2010,

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <>.

   [RFC6371]  Busi, I., Ed. and D. Allan, Ed., "Operations,
              Administration, and Maintenance Framework for MPLS-Based
              Transport Networks", RFC 6371, DOI 10.17487/RFC6371,
              September 2011, <>.

   [RFC6373]  Andersson, L., Ed., Berger, L., Ed., Fang, L., Ed., Bitar,
              N., Ed., and E. Gray, Ed., "MPLS Transport Profile (MPLS-
              TP) Control Plane Framework", RFC 6373,
              DOI 10.17487/RFC6373, September 2011,

   [RFC6378]  Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
              N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS-
              TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378,
              October 2011, <>.

   [RFC6426]  Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS
              On-Demand Connectivity Verification and Route Tracing",
              RFC 6426, DOI 10.17487/RFC6426, November 2011,

   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437,
              DOI 10.17487/RFC6437, November 2011,

   [RFC6564]  Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
              M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
              RFC 6564, DOI 10.17487/RFC6564, April 2012,

   [RFC6621]  Macker, J., Ed., "Simplified Multicast Forwarding",
              RFC 6621, DOI 10.17487/RFC6621, May 2012,

   [RFC6658]  Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
              "Packet Pseudowire Encapsulation over an MPLS PSN",
              RFC 6658, DOI 10.17487/RFC6658, July 2012,

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,

   [RFC6814]  Pignataro, C. and F. Gont, "Formally Deprecating Some IPv4
              Options", RFC 6814, DOI 10.17487/RFC6814, November 2012,

   [RFC6864]  Touch, J., "Updated Specification of the IPv4 ID Field",
              RFC 6864, DOI 10.17487/RFC6864, February 2013,

   [RFC7045]  Carpenter, B. and S. Jiang, "Transmission and Processing
              of IPv6 Extension Headers", RFC 7045,
              DOI 10.17487/RFC7045, December 2013,

   [RFC7198]  Begen, A. and C. Perkins, "Duplicating RTP Streams",
              RFC 7198, DOI 10.17487/RFC7198, April 2014,

   [RFC7209]  Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N.,
              Henderickx, W., and A. Isaac, "Requirements for Ethernet
              VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014,

   [RFC7271]  Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
              D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
              Transport Profile (MPLS-TP) Linear Protection to Match the
              Operational Expectations of Synchronous Digital Hierarchy,
              Optical Transport Network, and Ethernet Transport Network
              Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014,

   [RFC7399]  Farrel, A. and D. King, "Unanswered Questions in the Path
              Computation Element Architecture", RFC 7399,
              DOI 10.17487/RFC7399, October 2014,

   [RFC7426]  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
              Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
              Defined Networking (SDN): Layers and Architecture
              Terminology", RFC 7426, DOI 10.17487/RFC7426, January
              2015, <>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <>.

   [RFC7510]  Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
              "Encapsulating MPLS in UDP", RFC 7510,
              DOI 10.17487/RFC7510, April 2015,

   [RFC7637]  Garg, P., Ed. and Y. Wang, Ed., "NVGRE: Network
              Virtualization Using Generic Routing Encapsulation",
              RFC 7637, DOI 10.17487/RFC7637, September 2015,

   [RFC7676]  Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
              for Generic Routing Encapsulation (GRE)", RFC 7676,
              DOI 10.17487/RFC7676, October 2015,

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,

   [RFC7813]  Farkas, J., Ed., Bragg, N., Unbehagen, P., Parsons, G.,
              Ashwood-Smith, P., and C. Bowers, "IS-IS Path Control and
              Reservation", RFC 7813, DOI 10.17487/RFC7813, June 2016,

   [RFC7872]  Gont, F., Linkova, J., Chown, T., and W. Liu,
              "Observations on the Dropping of Packets with IPv6
              Extension Headers in the Real World", RFC 7872,
              DOI 10.17487/RFC7872, June 2016,

   [ST20227]  SMPTE 2022, "Seamless Protection Switching of SMPTE ST
              2022 IP Datagrams", ST 2022-7:2013, 2013,

   [TSNTG]    IEEE Standards Association, "IEEE 802.1 Time-Sensitive
              Networks Task Group", 2013,

10.2.  URIs







Appendix A.  Examples of combined DetNet Service and Transport layers

Authors' Addresses

   Jouni Korhonen (editor)
   3151 Zanker Road
   San Jose, CA  95134

   Janos Farkas
   Konyves Kalman krt. 11/B
   Budapest  1097


   Gregory Mirsky


   Pascal Thubert


   Yan Zhuang


   Lou Berger
   LabN Consulting, L.L.C.