



Internet Engineering Task Force (IETF)                   P. Thubert, Ed.
Request for Comments: 9912                                   Independent
Category: Informational                                       April 2026
ISSN: 2070-1721


           Reliable and Available Wireless (RAW) Architecture

Abstract

   Reliable and Available Wireless (RAW) extends the reliability and
   availability of Deterministic Networking (DetNet) to networks
   composed of any combination of wired and wireless segments.  The RAW
   architecture leverages and extends RFC 8655 ("Deterministic
   Networking Architecture") to adapt to challenges that prominently
   affect the wireless medium, notably intermittent transmission loss.
   This document defines a network control loop that optimizes the use
   of constrained bandwidth and energy while ensuring the expected
   DetNet services.  The loop involves a new Point of Local Repair (PLR)
   function in the DetNet Service sub-layer that dynamically selects the
   DetNet path(s) for packets to route around local connectivity
   degradation.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9912.

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Table of Contents

   1.  Introduction
   2.  The RAW Problem
   3.  Terminology
     3.1.  Abbreviations
     3.2.  Link and Direction
       3.2.1.  Flapping
       3.2.2.  Uplink
       3.2.3.  Downlink
       3.2.4.  Downstream
       3.2.5.  Upstream
     3.3.  Path and Recovery Graphs
       3.3.1.  Path
       3.3.2.  Recovery Graph
       3.3.3.  Forward and Crossing
       3.3.4.  Protection Path
       3.3.5.  Segment
     3.4.  Deterministic Networking
       3.4.1.  The DetNet Planes
       3.4.2.  Flow
       3.4.3.  Residence Time
       3.4.4.  L3 Deterministic Flow Identifier
       3.4.5.  Time-Sensitive Networking
       3.4.6.  Lower-Layer API
     3.5.  Reliability and Availability
       3.5.1.  Service Level Agreement
       3.5.2.  Service Level Objective
       3.5.3.  Service Level Indicator
       3.5.4.  Precision Availability Metrics
       3.5.5.  Reliability
       3.5.6.  Availability
   4.  Reliable and Available Wireless
     4.1.  High Availability Engineering Principles
       4.1.1.  Elimination of Single Points of Failure
       4.1.2.  Reliable Crossover
       4.1.3.  Prompt Notification of Failures
     4.2.  Applying Reliability Concepts to Networking
     4.3.  Wireless Effects Affecting Reliability
   5.  The RAW Conceptual Model
     5.1.  The RAW Planes
     5.2.  RAW Versus Upper and Lower Layers
     5.3.  RAW and DetNet
   6.  The RAW Control Loop
     6.1.  Routing Timescale Versus Forwarding Timescale
     6.2.  OODA Loop
     6.3.  Observe: RAW OAM
     6.4.  Orient: The RAW-Extended DetNet Operational Plane
     6.5.  Decide: The Point of Local Repair
     6.6.  Act: DetNet Path Selection and Reliability Functions
   7.  Security Considerations
     7.1.  Collocated Denial-of-Service Attacks
     7.2.  Layer 2 Encryption
     7.3.  Forced Access
   8.  IANA Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgments
   Contributors
   Author's Address

1.  Introduction

   Deterministic Networking (DetNet) aims to provide bounded latency and
   eliminate congestion loss, even when coexisting with best-effort
   traffic.  It provides the ability to carry specified unicast or
   multicast data flows for real-time applications with extremely low
   packet loss rates and ensures maximum end-to-end delivery latency.  A
   description of the general background and concepts of DetNet can be
   found in [DetNet-ARCH].

   DetNet and the related IEEE 802.1 Time-Sensitive Networking (TSN)
   [TSN] initially focused on wired infrastructure, which provides a
   more stable communication channel than wireless networks.  Wireless
   networks operate on a shared medium where uncontrolled interference,
   including self-induced multipath fading, may cause intermittent
   transmission losses.  Fixed and mobile obstacles and reflectors may
   block or alter the signal, causing transient and unpredictable
   variations of the throughput and Packet Delivery Ratio (PDR) of a
   wireless link.  This adds new dimensions to the statistical effects
   that affect the quality and reliability of the link.

   Nevertheless, deterministic capabilities are required in a number of
   wireless use cases as well [RAW-USE-CASES].  With scheduled radios
   such as Time-Slotted Channel Hopping (TSCH) and Orthogonal Frequency-
   Division Multiple Access (OFDMA) being developed to provide
   determinism over wireless links at the lower layers, providing DetNet
   capabilities has become possible.  See [RAW-TECHNOS] for more on
   TSCH, OFDMA, and other technologies.

   Reliable and Available Wireless (RAW) takes up the challenge of
   providing highly available and reliable end-to-end performances in a
   DetNet network that may include wireless segments.  To achieve this,
   RAW leverages all possible transmission diversity and redundancy to
   ensure packet delivery, while optimizing the use of the shared
   spectrum to preserve bandwidth and save energy.  To that effect, RAW
   defines protection paths that can be activated dynamically upon
   failures and a control loop that dynamically controls the activation
   and deactivation of the feasible protection paths to react quickly to
   intermittent losses.

   The intent of RAW is to meet Service Level Objectives (SLOs) in terms
   of PDR, maximum contiguous losses, or latency boundaries for DetNet
   flows over mixes of wired and wireless networks, including wireless
   access and meshes (see Section 2 for more on the RAW problem).  This
   document introduces and/or leverages terminology (see Section 3),
   principles (see Section 4), and concepts such as protection paths and
   recovery graphs to put together a conceptual model for RAW (see
   Section 5).  Based on that model, this document elaborates on an in-
   network optimization control loop (see Section 6).

2.  The RAW Problem

   While the generic "Deterministic Networking Problem Statement"
   [RFC8557] applies to both wired and wireless media, the
   "Deterministic Networking Architecture" [DetNet-ARCH] must be
   extended to address less consistent transmissions, energy
   conservation, and shared spectrum efficiency.

   Operating at Layer 3, RAW does not change the wireless technology at
   the lower layers.  On the other hand, it can further increase
   diversity in the spatial, time, code, and frequency domains by
   enabling multiple link-layer wired and wireless technologies in
   parallel or sequentially, for a higher resilience and a wider
   applicability.  RAW can also provide homogeneous services to critical
   applications beyond the boundaries of a single subnetwork, e.g.,
   using diverse radio access technologies to optimize the end-to-end
   application experience.

   RAW extends the DetNet services by providing elements that are
   specialized for transporting IP flows over deterministic radio
   technologies such as those listed in [RAW-TECHNOS].  Conceptually,
   RAW is agnostic to the lower layer, though the capability to control
   latency is assumed to ensure the DetNet services that RAW extends.
   How the lower layers are operated to do so (and whether a radio
   network is single hop or meshed, for example) are opaque to the IP
   layer and not part of the RAW abstraction.  Nevertheless, cross-layer
   optimizations may take place to ensure proper link awareness (such as
   link quality) and packet handling (such as scheduling).

   The RAW architecture extends the DetNet Network Plane to accommodate
   one or multiple hops of homogeneous or heterogeneous wired and
   wireless technologies.  RAW adds reactivity to the DetNet forwarding
   sub-layer to compensate the dynamics for the radio links in terms of
   lossiness and bandwidth.  This may apply, for instance, to mesh
   networks as illustrated in Figure 4 or diverse radio access networks
   as illustrated in Figure 10.

   As opposed to wired links, the availability and performance of an
   individual wireless link cannot be trusted over the long term; it
   varies with transient service discontinuity, and any path that
   includes wireless hops is bound to face short periods of high loss.
   On the other hand, being broadcast in nature, the wireless medium
   provides capabilities that are atypical on modern wired links and
   that the RAW architecture can leverage opportunistically to improve
   the end-to-end reliability over a collection of paths.

   Those capabilities include:

   Promiscuous overhearing:  Some wired and wireless technologies allow
      for multiple lower-layer attached nodes to receive the same packet
      sent by another node.  This differs from a lower-layer network
      that is physically point-to-point, like a wire.  With overhearing,
      more than one node in the forward direction of the packet may hear
      or overhear a transmission, and the reception by one may
      compensate the loss by another.  The concept of path can be
      revisited in favor of multipoint-to-multipoint progress in the
      forward direction and statistical chances of successful reception
      of any of the transmissions by any of the receivers.

   L2-aware routing:  As the quality and speed of a link varies over
      time, the concept of metric must also be revisited.  Shortest-path
      cost loses its absolute value, and hop count turns into a bad idea
      as the link budget drops with the physical distance.  Routing over
      radio requires both:

      1.  a new and more dynamic sense of link metrics, with new
          protocols such as the Dynamic Link Exchange Protocol (DLEP)
          and Layer 2 (L2) triggers to keep Layer 3 (L3) up to date with
          the link quality and availability, and

      2.  an approach to multipath routing, where multiple link metrics
          are considered since simple shortest-path cost loses its
          meaning with the instability of the metrics.

   Redundant transmissions:  Though feasible on any technology,
      proactive (forward) and reactive (acknowledgment-based) error
      correction is typical for wireless media.  Bounded latency can
      still be obtained on a wireless link while operating those
      technologies, provided that link latency used in path selection
      allows for the extra transmission or the introduced delay is
      compensated along the path.  In the case of coded fragments and
      retries, it makes sense to vary all the possible physical
      properties of the transmission to reduce the chances that the same
      effect causes the loss of both original and redundant
      transmissions.

   Relay coordination and constructive interference:  Though it can be
      difficult to achieve at high speed, a fine time synchronization
      and a precise sense of phase allows the energy from multiple
      coordinated senders to add up at the receiver and actually improve
      the signal quality, compensating for either distance or physical
      objects in the Fresnel zone that would reduce the link budget.
      From a DetNet perspective, this may translate to taking into
      account how transmission from one node may interfere with the
      transmission of another node attached to the same wireless sub-
      layer network.

   RAW and DetNet enable application flows that require a special
   treatment along paths that can provide that treatment.  This may be
   seen as a form of Path Aware networking and may be subject to
   impediments documented in [RFC9049].

   The mechanism used to establish a path is not unique to, or
   necessarily impacted by, RAW.  The mechanism is expected to be the
   product of the DetNet Controller Plane [DetNet-PLANE]; it may use a
   Path Computation Element (PCE) [RFC4655] or the DetNet YANG data
   model [RFC9633], or it may be computed in a distributed fashion as
   per the Resource ReSerVation Protocol (RSVP) [RFC2205].  Either way,
   the assumption is that it is slow relative to local forwarding
   operations along the path.  To react fast enough to transient changes
   in the radio transmissions, RAW leverages DetNet Network Plane
   enhancements to optimize the use of the paths and match the quality
   of the transmissions over time.

   As opposed to wired networks, the action of installing a path over a
   set of wireless links may be very slow relative to the speed at which
   the radio conditions vary; thus, in the wireless case, it makes sense
   to provide redundant forwarding solutions along alternate paths (see
   Section 3.3) and to leave it to the Network Plane to select which of
   those forwarding solutions are to be used for a given packet based on
   the current conditions.  The RAW Network Plane operations happen
   within the scope of a recovery graph (see Section 3.3.2) that is pre-
   established and installed by means outside of the scope of RAW.  A
   recovery graph may be strict or loose depending on whether each hop
   or just a subset of the hops is observed and controlled by RAW.

   RAW distinguishes the longer timescale at which routes are computed
   from the shorter timescale where forwarding decisions are made (see
   Section 6.1).  The RAW Network Plane operations happen at a timescale
   that sits timewise between the routing and the forwarding timescales.
   Within the resources delineated by a recovery graph, their goal is to
   dynamically select the protection path(s) that the upcoming packets
   of a DetNet flow shall follow.  As they influence the path for the
   entirety of the flows or a portion of them, the RAW Network Plane
   operations may affect the metrics used in their rerouting decisions,
   which could potentially lead to oscillations; such effects must be
   avoided or dampened.

3.  Terminology

   RAW reuses terminology defined for DetNet in "Deterministic
   Networking Architecture" [DetNet-ARCH], e.g., "PREOF" to stand for
   "Packet Replication, Elimination, and Ordering Functions".  RAW
   inherits and augments IETF recovery mechanisms such as the ones
   provided in DetNet [DetNet-ARCH] and in Traffic Engineering, e.g.,
   [RFC4090].

   RAW also reuses terminology defined for Operations, Administration,
   and Maintenance (OAM) protocols in Section 1.1 of "Framework of
   Operations, Administration, and Maintenance (OAM) for Deterministic
   Networking (DetNet)" [DetNet-OAM] and in "Active and Passive Metrics
   and Methods (with Hybrid Types In-Between)" [RFC7799].

   RAW also reuses terminology defined for MPLS in [RFC4427], such as
   the term "recovery" to cover both protection and restoration for a
   number of recovery types.  That document defines a number of
   concepts, such as the recovery domain, that are used in RAW
   mechanisms and defines the new term "recovery graph".  A recovery
   graph associates a topological graph with usage metadata that
   represents how the paths are built and used within the recovery
   graph.  The recovery graph provides excess bandwidth for the intended
   traffic over alternate potential paths, and the use of that bandwidth
   is optimized dynamically.

   The concept of a recovery graph is agnostic to the underlying
   technology and applies, but is not limited to, any full or partial
   wireless mesh.  RAW specifies strict and loose recovery graphs
   depending on whether the path is fully controlled by RAW or traverses
   an opaque network where RAW cannot observe and control the individual
   hops.

   RAW also reuses terminology defined for RSVP-TE in [RFC4090], such as
   the "Point of Local Repair (PLR)".  The concept of a backup path is
   generalized with protection path, which is the term mostly found in
   recent standards and used in this document.

   RAW also reuses terminology defined for 6TiSCH in [6TiSCH-ARCH] and
   equates the 6TiSCH concept of a Track with that of a recovery graph.

3.1.  Abbreviations

   RAW uses the following abbreviations.

   ARQ
      Automatic Repeat Request.  A well-known mechanism that enables an
      acknowledged transmission with retries to mitigate errors and
      loss.  ARQ may be implemented at various layers in a network.  ARQ
      is typically implemented per hop (not end to end) at Layer 2 in
      wireless networks.  ARQ improves delivery on lossy wireless.
      Additionally, ARQ retransmission may be further limited by a
      bounded time to meet end-to-end packet latency constraints.
      Additional details and considerations for ARQ are detailed in
      [RFC3366].

   FEC
      Forward Error Correction.  Adding redundant data to protect
      against a partial loss without retries.

   HARQ
      Hybrid ARQ.  A combination of FEC and ARQ.

   ETX
      Expected Transmission Count.  A statistical metric that represents
      the expected total number of packet transmissions (including
      retransmissions) required to successfully deliver a packet along a
      path, used by 6TiSCH [RFC6551].

   ISM
      Industrial, Scientific, and Medical.  Refers to a group of radio
      bands or parts of the radio spectrum (e.g., 2.4 GHz and 5 GHz)
      that are internationally reserved for the use of radio frequency
      (RF) energy intended for industrial, scientific, and medical
      requirements (e.g., by microwaves, depth radars, and medical
      diathermy machines).  Cordless phones, Bluetooth and Low-Power
      Wireless Personal Area Network (LoWPAN) devices, near-field
      communication (NFC) devices, garage door openers, baby monitors,
      and Wi-Fi networks may all use the ISM frequencies, although these
      low-power transmitters are not considered to be ISM devices.  In
      general, communications equipment operating in ISM bands must
      tolerate any interference generated by ISM applications, and users
      have no regulatory protection from ISM device operation in these
      bands.

   PER
      Packet Error Rate.  The ratio of the number of packets received in
      error to the total number of transmitted packets.  A packet is
      considered to be in error if even a single bit within the packet
      is received incorrectly.

   PDR
      Packet Delivery Ratio (PDR).  The ratio of the number of
      successfully delivered data packets to the total number of packets
      transmitted from the sender to the receiver.

   RSSI
      Received Signal Strength Indication.  Also known as "Energy
      Detection Level".  A measure of the incoherent (raw) RF power in a
      channel.  The RF power can come from any source: other
      transmitters using the same technology, other radio technology
      using the same band, or background radiation.  For a single hop,
      RSSI may be used for LQI.

   LQI
      Link Quality Indicator.  An indication of the quality of the data
      packets received by the receiver.  It is typically derived from
      packet error statistics, with the exact method depending on the
      network stack being used.  LQI values may be exposed to the
      Controller Plane for each individual hop or cumulated along
      segments.  Outgoing LQI values can be calculated from coherent
      (demodulated) PER, RSSI, and incoming LQI values.

   OAM
      Operations, Administration, and Maintenance.  Covers the
      processes, activities, tools, and standards involved with
      operating, administering, managing, and maintaining any system.
      This document uses the term in conformance with "Guidelines for
      the Use of the 'OAM' Acronym in the IETF" [RFC6291], and the
      system observed by the RAW OAM is the recovery graph.

   OODA
      Observe, Orient, Decide, Act. A generic formalism to represent the
      operational steps in a control loop.  In the context of RAW, OODA
      is applied to network control and convergence; see Section 6.2 for
      more.

   SNR
      Signal-to-Noise Ratio.  Also known as "S/N Ratio".  A measure used
      in science and engineering that compares the level of a desired
      signal to the level of background noise.  SNR is defined as the
      ratio of signal power to noise power, often expressed in decibels.

3.2.  Link and Direction

   This document uses the following terms relating to links and
   direction in the context of RAW.

3.2.1.  Flapping

   In the context of RAW, a link flaps when the reliability of the
   wireless connectivity drops abruptly for a short period of time,
   typically a duration of a subsecond to seconds.

3.2.2.  Uplink

   An uplink is the connection from end devices to data communication
   equipment.  In the context of wireless, uplink refers to the
   connection between a station (STA) and a controller (AP) or a User
   Equipment (UE) and a Base Station (BS) such as a 3GPP 5G gNodeB
   (gNB).

3.2.3.  Downlink

   A downlink is the reverse direction from uplink.

3.2.4.  Downstream

   Downstream refers to the following the direction of the flow data
   path along a recovery graph.

3.2.5.  Upstream

   Upstream refers to going against the direction of the flow data path
   along a recovery graph.

3.3.  Path and Recovery Graphs

   This document uses the following terms relating to paths and recovery
   graphs in the context of RAW.

3.3.1.  Path

   Section 1.3.3 of [INT-ARCH] provides a definition of path:

   |  At a given moment, all the IP datagrams from a particular source
   |  host to a particular destination host will typically traverse the
   |  same sequence of gateways.  We use the term "path" for this
   |  sequence.  Note that a path is uni-directional; it is not unusual
   |  to have different paths in the two directions between a given host
   |  pair.

   Section 2 of [RFC9473] points to a longer, more modern definition of
   path, which begins as follows:

   |  A sequence of adjacent path elements over which a packet can be
   |  transmitted, starting and ending with a node.
   |  
   |  Paths are unidirectional and time dependent, i.e., there can be a
   |  variety of paths from one node to another, and the path over which
   |  packets are transmitted may change.  A path definition can be
   |  strict (i.e., the exact sequence of path elements remains the
   |  same) or loose (i.e., the start and end node remain the same, but
   |  the path elements between them may vary over time).
   |  
   |  The representation of a path and its properties may depend on the
   |  entity considering the path.  On the one hand, the representation
   |  may differ due to entities having partial visibility of path
   |  elements comprising a path or their visibility changing over time.

   It follows that the general acceptance of a path is a linear sequence
   of links and nodes, as opposed to a multi-dimensional graph, defined
   by the experience of the packet that went from a node A to a node B.
   In the context of this document, a path is observed by following one
   copy or one fragment of a packet that conserves its uniqueness and
   integrity.  For instance, if C replicates to E and F and if D
   eliminates duplicates, a packet from A to B can experience two paths:
   A->C->E->D->B and A->C->F->D->B.  Those paths are called protection
   paths.  Protection paths may be fully non-congruent; alternatively,
   they may intersect at replication or elimination points.

   With DetNet and RAW, a packet may be duplicated, fragmented, and
   network coded, and the various byproducts may travel different paths
   that are not necessarily end to end between A and B.  We refer to
   this complex scenario as a DetNet path.  As such, the DetNet path
   extends the above description of a path, but it still matches the
   experience of a packet that traverses the network.

   With RAW, the path experienced by a packet is subject to change from
   one packet to the next, but all the possible experiences are all
   contained within a finite set.  Therefore, we introduce the term
   "recovery graph" (see the next section) that coalesces that set and
   covers the overall topology where the possible DetNet paths are all
   contained.  As such, the recovery graph coalesces all the possible
   paths a flow may experience, each with its own statistical
   probability to be used.

3.3.2.  Recovery Graph

   A recovery graph is a networking graph that can be followed to
   transport packets with equivalent treatment and is associated with
   usage metadata.  In contrast to the definition of a path above, a
   recovery graph represents a potential path, not an actual one.  Also,
   a recovery graph is not necessarily a linear sequence like a simple
   path and is not necessarily fully traversed (flooded) by all packets
   of a flow like a DetNet path.  Still, and as a simplification, the
   casual reader may consider that a recovery graph is very much like a
   DetNet path, aggregating multiple paths that may overlap or fork and
   then rejoin, for instance, to enable a protection service by the
   PREOF operations.

                      _________
                     |         |
                     | IoT G/W |
                     |_________|
                       EGRESS  <<=== Elimination at Egress
                        |  |
            ---+--------+--+--------+--------
               |      Backbone      |
             __|__                __|__
            |     | Backbone     |     | Backbone
            |__ __| Router       |__ __| Router
               |           #        |
            #   \     #            /  <-- protection path
          #      #        #-------#
                  \  #   /  #         ( Low-power )
           #   #   \    /      #     ( Lossy Network)
                    \  /
              #   INGRESS <<=== Replication at recovery graph ingress
                     |
                     # <-- source device
           #: Low-power device

      Figure 1: Example IoT Recovery Graph to an IoT Gateway with 1+1
                                 Redundancy

   Refining further, a recovery graph is defined as the coalescence of
   all the feasible DetNet paths that a packet with an assigned flow may
   be forwarded along.  A packet that is assigned to the recovery graph
   experiences one of the feasible DetNet paths based on the current
   selection by the PLR at the time the packet traverses the network.

   Refining even further, the feasible DetNet paths within the recovery
   graph may or may not be computed in advance; instead, they may be
   decided upon the detection of a change from a clean slate.
   Furthermore, the PLR decision may be distributed, which yields a
   large combination of possible and dependent decisions, with no node
   in the network capable of reporting which is the current DetNet path
   within the recovery graph.

   In DetNet [DetNet-ARCH] terms, a recovery graph has the following
   properties:

   *  A recovery graph is a Layer 3 abstraction built upon IP links
      between routers.  A router may form multiple IP links over a
      single radio interface.

   *  A recovery graph has one ingress and one egress node, which
      operate as DetNet edge nodes.

   *  A recovery graph is reversible, meaning that packets can be routed
      against the flow of data packets, e.g., to carry OAM measurements
      or control messages back to the ingress.

   *  The vertices of a recovery graph are DetNet relay nodes that
      operate at the DetNet Service sub-layer and provide the PREOF
      functions.

   *  The topological edges of a recovery graph are strict sequences of
      DetNet transit nodes that operate at the DetNet forwarding sub-
      layer.

   Figure 2 illustrates the generic concept of a recovery graph, between
   an ingress node and an egress node.  The recovery graph is composed
   of forward protection paths, forward segments, and crossing segments
   (see the definitions of those terms in the next sections).  The
   recovery graph contains at least two protection paths: a main path
   and a backup path.

       ------------------- forward direction ---------------------->

             a ==> b ==> C -=- F ==> G ==> h     T1
           /              \   /      |       \ /
         I                  o        n        E -=- T2
           \              /   \      |       / \
             p ==> q ==> R -=- T ==> U ==> v     T3

            I: Ingress
            E: Egress
            T1, T2, T3: external targets
            Uppercase: DetNet relay nodes
            Lowercase: DetNet transit nodes

               Figure 2: A Recovery Graph and Its Components

   Of note:

   I ==> a ==> b ==> C:  A forward segment to targets F and o

   C ==> o ==> T:  A forward segment to target T (and/or U)

   G | n | U:  A crossing segment to targets G or U

   I -> F -> E:  A forward protection path to targets T1, T2, and T3

   I, a, b, C, F, G, h, E:  A path to T1, T2, and/or T3

   I, p, q, R, o, F, G, h, E:  A segment-crossing protection path

3.3.3.  Forward and Crossing

   Forward refers to progress towards the egress of the recovery graph.
   Forward links are directional, and packets that are forwarded along
   the recovery graph can only be transmitted along the link direction.
   Crossing links are bidirectional, meaning that they can be used in
   both directions, though a given packet may use the link in one
   direction only.  A segment can be forward, in which case it is
   composed of forward links only, or it can be crossing, in which case
   it is composed of crossing links only.  A protection path is always
   forward, meaning that it is composed of forward links and segments.

3.3.4.  Protection Path

   A protection path is an end-to-end forward path between the ingress
   and egress nodes of a recovery graph.  A protection path in a
   recovery graph is expressed as a strict sequence of DetNet relay
   nodes or as a loose sequence of DetNet relay nodes that are joined by
   segments in the recovery graph.  Background information on the
   concepts related to protection paths can be found in [RFC4427] and
   [RFC6378].

3.3.5.  Segment

   A segment is a strict sequence of DetNet transit nodes between two
   DetNet relay nodes; a segment of a recovery graph is composed
   topologically of two vertices of the recovery graph and one edge of
   the recovery graph between those vertices.

3.4.  Deterministic Networking

   This document reuses the terminology in Section 2 of [RFC8557] and
   Section 4.1.2 of [DetNet-ARCH] for deterministic networking and
   deterministic networks.  This document also uses the following terms.

3.4.1.  The DetNet Planes

   [DetNet-ARCH] defines three planes: the Application (User) Plane, the
   Controller Plane, and the Network Plane.  The DetNet Network Plane is
   composed of a Data Plane (packet forwarding) and an Operational Plane
   where OAM operations take place.  In the Network Plane, the DetNet
   Service sub-layer focuses on flow protection (e.g., using redundancy)
   and can be fully operated at Layer 3, while the DetNet forwarding
   sub-layer establishes the paths, associates the flows to the paths,
   ensures the availability of the necessary resources, and leverages
   Layer 2 functionalities for timely delivery to the next DetNet
   system.  For more information, see Section 2.

3.4.2.  Flow

   A flow is a collection of consecutive IP packets defined by the upper
   layers and signaled by the same 5-tuple or 6-tuple (see Section 5.1
   of [RFC8939]).  Packets of the same flow must be placed on the same
   recovery graph to receive an equivalent treatment from ingress to
   egress within the recovery graph.  Multiple flows may be transported
   along the same recovery graph.  The DetNet path that is selected for
   the flow may change over time under the control of the PLR.

3.4.3.  Residence Time

   A residence time (RT) is defined as the time interval between when
   the reception of a packet starts and the transmission of the packet
   begins.  In the context of RAW, RT is useful for a transit nodes, not
   ingress or egress nodes.

3.4.4.  L3 Deterministic Flow Identifier

   The classic IP 5-tuple that identifies a flow comprises the source
   IP, destination IP, source port, destination port, and the Upper-
   Layer Protocol (ULP).  DetNet uses a 6-tuple where the extra field is
   the Differentiated Services Code Point (DSCP) field in the packet
   (see Section 3.3 of [DetNet-DP]).  The IPv6 flow label is not used
   for that purpose.

3.4.5.  Time-Sensitive Networking

   Time-Sensitive Networking (TSN) denotes the IEEE 802 efforts
   regarding deterministic networking, originally for use on Ethernet.
   See [TSN].  Wireless TSN (WTSN) denotes extensions of the TSN work on
   wireless media, e.g., the RAW technologies described in
   [RAW-TECHNOS].

3.4.6.  Lower-Layer API

   RAW includes the concept of a lower-layer API (LL API) that provides
   an interface between the lower-layer (e.g., wireless) technology and
   the DetNet layers.  The LL API is technology dependent as what the
   lower layers expose towards the DetNet layers may vary.  Furthermore,
   different RAW technologies are equipped with different reliability
   features (e.g., short-range broadcast, Multiple User - Multiple Input
   Multiple Output (MU-MIMO), physical layer (PHY) rate and other
   Modulation Coding Scheme (MCS) adaptation, coding and retransmissions
   methods, and constructive interference and overhearing; see
   [RAW-TECHNOS] for more details).  The LL API enables interactions
   between the reliability functions provided by the lower layer and the
   reliability functions provided by DetNet.  That is, the LL API makes
   cross-layer optimization possible for the reliability functions of
   different layers depending on the actual exposure provided via the LL
   API by the given RAW technology.  The Dynamic Link Exchange Protocol
   (DLEP) [DLEP] is an example of a protocol that can be used to
   implement the LL API.

3.5.  Reliability and Availability

   In the context of the RAW work, reliability and availability are
   defined as follows, along with the following other terms.

3.5.1.  Service Level Agreement

   In the context of RAW, a Service Level Agreement (SLA) is a contract
   between a provider (the network) and a client (the application flow)
   that defines measurable metrics such as latency boundaries,
   consecutive losses, and Packet Delivery Ratio (PDR).

3.5.2.  Service Level Objective

   A Service Level Objective (SLO) is one term in the SLA, for which
   specific network setting and operations are implemented.  For
   instance, a dynamic tuning of packet redundancy addresses an SLO of
   consecutive losses in a row by augmenting the chances of delivery of
   a packet that follows a loss.

3.5.3.  Service Level Indicator

   A Service Level Indicator (SLI) measures the compliance of an SLO to
   the terms of the contract.  For instance, it can be the statistics of
   individual losses or losses in a row during a certain amount of time.

3.5.4.  Precision Availability Metrics

   Precision Availability Metrics (PAMs) [RFC9544] aim to capture
   service levels for a flow, specifically the degree to which the flow
   complies with the SLOs that are in effect.

3.5.5.  Reliability

   Reliability is a measure of the probability that an item (e.g.,
   system or network) will perform its intended function with no failure
   for a stated period of time (or for a stated number of demands or
   load) under stated environmental conditions.  In other words,
   reliability is the probability that an item will be in an uptime
   state (i.e., fully operational or ready to perform) for a stated
   mission (e.g., to provide an SLA).  See more in [NASA1].

3.5.6.  Availability

   Availability is the probability of an item's (e.g., a network's)
   mission readiness (e.g., to provide an SLA).  Availability is
   expressed as (uptime)/(uptime+downtime).  Note that it is
   availability that addresses downtime (including time for maintenance,
   repair, and replacement activities) and not reliability.  See more in
   [NASA2].

4.  Reliable and Available Wireless

4.1.  High Availability Engineering Principles

   The reliability criteria of a critical system pervade its elements,
   and if the system comprises a data network, then the data network is
   also subject to the inherited reliability and availability criteria.
   It is only natural to consider the art of high availability
   engineering and apply it to wireless communications in the context of
   RAW.

   There are three principles (pillars) of high availability
   engineering:

   1.  elimination of each single point of failure

   2.  reliable crossover

   3.  prompt detection of failures as they occur

   These principles are common to all high availability systems, not
   just ones with Internet technology at the center.  Both non-Internet
   and Internet examples are included.

4.1.1.  Elimination of Single Points of Failure

   Physical and logical components in a system happen to fail, either as
   the effect of wear and tear, when used beyond acceptable limits, or
   due to a software bug.  It is necessary to decouple component failure
   from system failure to avoid the latter.  This allows failed
   components to be restored while the rest of the system continues to
   function.

   IP routers leverage routing protocols to reroute to alternate routes
   in case of a failure.  When links are cabled through the same
   conduit, they form a Shared Risk Link Group (SRLG) and share the same
   fate if the conduit is cut, making the reroute operation ineffective.
   The same effect can happen with virtual links that end up in the same
   physical transport through the intricacies of nested encapsulation.
   In the same fashion, an interferer or an obstacle may affect multiple
   wireless transmissions at the same time, even between different sets
   of peers.

   Intermediate network nodes (such as routers, switches and APs, wire
   bundles, and the air medium itself) can become single points of
   failure.  Thus, for high availability, the use of physically link-
   disjoint and node-disjoint paths is required; in the wireless space,
   the use of the highest possible degree of diversity (time, space,
   code, frequency, and channel width) in the transmissions over the air
   is also required to combat the additional causes of transmission
   loss.

   From an economics standpoint, executing this principle properly
   generally increases capital expense because of the redundant
   equipment.  In a constrained network where the waste of energy and
   bandwidth should be minimized, an excessive use of redundant links
   must be avoided; for RAW, this means that the extra bandwidth must be
   used wisely and efficiently.

4.1.2.  Reliable Crossover

   Backup equipment has limited value unless it can be reliably switched
   into use within the downtime parameters.  IP routers execute reliable
   crossover continuously because the routers use any alternate routes
   that are available [RFC0791].  This is due to the stateless nature of
   IP datagrams and the dissociation of the datagrams from the
   forwarding routes they take.  "IP Fast Reroute Framework" [FRR]
   analyzes mechanisms for fast failure detection and path repair for IP
   Fast Reroute (FRR) and discusses the case of multiple failures and
   SRLG.  Examples of FRR techniques include Remote Loop-Free Alternate
   [RLFA-FRR] and backup Label Switched Path (LSP) tunnels for the local
   repair of LSP tunnels using RSVP-TE [RFC4090].

   Deterministic flows, on the contrary, are attached to specific paths
   where dedicated resources are reserved for each flow.  Therefore,
   each DetNet path must inherently provide sufficient redundancy to
   provide the assured SLOs at all times.  The DetNet PREOF typically
   leverages 1+1 redundancy whereby a packet is sent twice, over non-
   congruent paths.  This avoids the gap during the FRR operation but
   doubles the traffic in the network.

   In the case of RAW, the expectation is that multiple transient faults
   may happen in overlapping time windows, in which case the 1+1
   redundancy with delayed reestablishment of the second path does not
   provide the required guarantees.  The Data Plane must be configured
   with a sufficient degree of redundancy to select an alternate
   redundant path immediately upon a fault, without the need for a slow
   intervention from the Controller Plane.

4.1.3.  Prompt Notification of Failures

   The execution of the two above principles is likely to render a
   system where the end user rarely sees a failure.  However, a failure
   that occurs must still be detected in order to direct maintenance.

   There are many reasons for system monitoring (Fault, Configuration,
   Accounting, Performance, and Security (FCAPS) is a handy mental
   checklist), but fault monitoring is a sufficient reason.

   "Overview and Principles of Internet Traffic Engineering" [TE]
   discusses the importance of measurement for network protection and
   provides an abstract method for network survivability with the
   analysis of a traffic matrix as observed via a network management
   YANG data model, probing techniques, file transfers, IGP link state
   advertisements, and more.

   Those measurements are needed in the context of RAW to inform the
   controller and make the long-term reactive decision to rebuild a
   recovery graph based on statistical and aggregated information.  RAW
   itself operates in the DetNet Network Plane at a faster timescale
   with live information on speed, state, etc.  This live information
   can be obtained directly from the lower layer (e.g., using L2
   triggers), read from a protocol such as DLEP, or transported over
   multiple hops using OAM and reverse OAM, as illustrated in Figure 11.

4.2.  Applying Reliability Concepts to Networking

   The terms "reliability" and "availability" are defined for use in RAW
   in Section 3, and the reader is invited to read [NASA1] and [NASA2]
   for more details on the general definition of reliability.
   Practically speaking, a number of nines is often used to indicate the
   reliability of a data link (e.g., 5 nines indicate a Packet Delivery
   Ratio (PDR) of 99.999%).

   This number is typical in a wired environment where the loss is due
   to a random event such as a solar particle that affects the
   transmission of a particular packet but does not affect the previous
   packet, the next packet, or packets transmitted on other links.  Note
   that the QoS requirements in RAW may include a bounded latency, and a
   packet that arrives too late is a fault and not considered as
   delivered.

   For a periodic networking pattern such as an automation control loop,
   this number is proportional to the Mean Time Between Failures (MTBF).
   When a single fault can have dramatic consequences, the MTBF
   expresses the chances that the unwanted fault event occurs.  In data
   networks, this is rarely the case.  Packet loss cannot be fully
   avoided, and the systems are built to resist some loss.  This can be
   done by using redundancy with retries (as in HARQ), Packet
   Replication and Elimination (PRE) FEC, and Network Coding (e.g.,
   using FEC with Static Context Header Compression (SCHC) [RFC8724]
   fragments).  Also, in a typical control loop, linear interpolation
   from the previous measurements can be used.

   However, the linear interpolation method cannot resist multiple
   consecutive losses, and a high MTBF is desired as a guarantee that
   the number of losses in a row is bounded.  In this case, what is
   really desired is a Maximum Consecutive Loss (MCL).  If the number of
   losses in a row passes the MCL, the control loop has to abort, and
   the system (e.g., the production line) may need to enter an emergency
   stop condition.

   Engineers that build automated processes may use the network
   reliability expressed in nines as the MTBF and as a proxy to indicate
   an MCL, e.g., as described in Section 7.4 of "Deterministic
   Networking Use Cases" [RFC8578].

4.3.  Wireless Effects Affecting Reliability

   In contrast with wired networks, errors in transmission are the
   predominant source of packet loss in wireless networks.

   The root cause for the loss may be of multiple origins, calling for
   the use of different forms of diversity:

   Multipath fading:  A destructive interference by a reflection of the
      original signal.

      A radio signal may be received directly (line-of-sight) and/or as
      a reflection on a physical structure (echo).  The reflections take
      a longer path and are delayed by the extra distance divided by the
      speed of light in the medium.  Depending on the frequency, the
      echo lands with a different phase, which may either add up to
      (constructive interference) or cancel (destructive interference)
      the direct signal.

      The affected frequencies depend on the relative position of the
      sender, the receiver, and all the reflecting objects in the
      environment.  A given hop suffers from multipath fading for
      multiple packets in a row until a physical movement changes the
      reflection patterns.

   Co-channel interference:  Energy in the spectrum used for the
      transmission confuses the receiver.

      The wireless medium itself is a Shared Risk Link Group (SRLG) for
      nearby users of the same spectrum, as an interference may affect
      multiple co-channel transmissions between different peers within
      the interference domain of the interferer, possibly even when they
      use different technologies.

   Obstacle in Fresnel zone:  The Fresnel zone is an elliptical region
      of space between and around the transmit and receive antennas in a
      point-to-point wireless communication.  The optimal transmission
      happens when it is free of obstacles.

   In an environment that is rich in metallic structures and mobile
   objects, a single radio link provides a fuzzy service, meaning that
   it cannot be trusted to transport the traffic reliably over a long
   period of time.

   Transmission losses are typically not independent, and their nature
   and duration are unpredictable; as long as a physical object (e.g., a
   metallic trolley between peers) that affects the transmission is not
   removed, or as long as the interferer (e.g., a radar in the ISM band)
   keeps transmitting, a continuous stream of packets are affected.

   The key technique to combat those unpredictable losses is diversity.
   Different forms of diversity are necessary to combat different causes
   of loss, and the use of diversity must be maximized to optimize the
   PDR.

   A single packet may be sent at different times (time diversity) over
   diverse paths (spatial diversity) that rely on diverse radio channels
   (frequency diversity) leveraging diverse PHY technologies (e.g.,
   narrowband versus spread spectrum or diverse codes).  Using time
   diversity defeats short-term interferences; spatial diversity combats
   very local causes of interference such as multipath fading;
   narrowband and spread spectrum are relatively innocuous to one
   another and can be used for diversity in the presence of the other.

5.  The RAW Conceptual Model

   RAW extends the conceptual model described in Section 4 of
   "Deterministic Networking Architecture" [DetNet-ARCH] with the PLR at
   the Service sub-layer, as illustrated in Figure 3.  The PLR (see
   Section 6.5) provides additional agility against transmission loss.
   For example, the PLR can act based on indications from the lower
   layer or based on OAM.

              |  packets going  |        ^  packets coming   ^
              v down the stack  v        |   up the stack    |
           +-----------------------+   +-----------------------+
           |        Source         |   |      Destination      |
           +-----------------------+   +-----------------------+
           |   Service sub-layer:  |   |   Service sub-layer:  |
           |   Packet sequencing   |   | Duplicate elimination |
           |    Flow replication   |   |      Flow merging     |
           |    Packet encoding    |   |    Packet decoding    |
           | Point of Local Repair |   |                       |
           +-----------------------+   +-----------------------+
           | Forwarding sub-layer: |   | Forwarding sub-layer: |
           |  Resource allocation  |   |  Resource allocation  |
           |    Explicit routes    |   |    Explicit routes    |
           +-----------------------+   +-----------------------+
           |     Lower layers      |   |     Lower layers      |
           +-----------------------+   +-----------------------+
                       v                           ^
                        \_________________________/

            Figure 3: Extended DetNet Data Plane Protocol Stack

5.1.  The RAW Planes

   The RAW nodes are DetNet relay nodes that operate in the RAW Network
   Plane and are capable of additional diversity mechanisms and
   measurement functions related to the radio interface.  RAW leverages
   an Operational Plane orientation function (that typically operates
   inside the ingress edge nodes) to dynamically adapt the path of the
   packets and optimize the resource usage.

   In the case of centralized routing operations, the RAW Controller
   Plane Function (CPF) interacts with RAW nodes over a Southbound API.
   It consumes data and information from the network and generates
   knowledge and wisdom to help steer the traffic optimally inside a
   recovery graph.

                            DetNet Routing

           CPF               CPF          CPF                 CPF


                          Southbound API
      _-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-
    _-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-


                 ___ RAW  ___ RAW  ___ RAW  ___ RAW  __
                /    Node     Node     Node     Node   \
     Ingress __/     / \      /                   \     \____Egress
     End  __        /   \    /       .- -- .       \       ___  End
     Node   \      /     \  /     .-(        ).     \     /    Node
             \_ RAW  ___ RAW  ___(Non-RAW Nodes)__ RAW  _/
                Node     Node   (___.______.____)  Node

               Figure 4: RAW Nodes (Centralized Routing Case)

   When a new flow is defined, the routing function uses its current
   knowledge of the network to build a new recovery graph between an
   ingress End System and an egress End System for that flow; it
   indicates to the RAW nodes where the PREOF and/or radio diversity and
   reliability operations may be actioned in the Network Plane.

   *  The recovery graph may be strict, meaning that the DetNet
      forwarding sub-layer operations are enforced end to end.

   *  The recovery graph may be expressed loosely to enable traversing a
      non-RAW subnetwork as in Figure 7.  In that case, RAW cannot
      leverage end-to-end DetNet and cannot provide latency guarantees.

   The information that the orientation function reports to the routing
   function may be time aggregated (e.g., statistical), to match the
   longer-term operation of the routing function.  Example information
   includes link-layer metrics such as link bandwidth (the medium speed
   depends dynamically on the mode of the PHY layer), number of flows
   (bandwidth that can be reserved for a flow depends on the number and
   size of flows sharing the spectrum), and the average and mean squared
   deviation of availability and reliability metrics (such as PDR) over
   long periods of time.  It may also report an aggregated Expected
   Transmission Count (ETX) or a variation of it.

   Based on those metrics, the routing function installs the recovery
   graph with enough redundant forwarding solutions to ensure that the
   Network Plane can reliably deliver the packets within an SLA
   associated with the flows that it transports.  The SLA defines end-
   to-end reliability and availability requirements, in which
   reliability may be expressed as a successful delivery in order and
   within a bounded delay of at least one copy of a packet.

   Depending on the use case and the SLA, the recovery graph may
   comprise non-RAW segments, either interleaved inside the recovery
   graph (e.g., over tunnels) or all the way to the egress End node
   (e.g., a server in the local wired domain).  RAW observes the lower-
   layer links between RAW nodes (typically radio links) and the end-to-
   end network-layer operation to decide at all times which of the
   diversity schemes is actioned by which RAW nodes.

   Once a recovery graph is established, per-segment and end-to-end
   reliability and availability statistics are periodically reported to
   the routing function to ensure that the SLA can be met; if not, then
   the recovery graph is recomputed.

5.2.  RAW Versus Upper and Lower Layers

   RAW builds on DetNet-provided features such as scheduling and
   shaping.  In particular, RAW inherits the DetNet guarantees on end-
   to-end latency, which can be tuned to ensure that DetNet and RAW
   reliability mechanisms have no side effect on upper layers, e.g., on
   transport-layer packet recovery.  RAW operations include possible
   rerouting, which in turn may affect the ordering of a burst of
   packets.  RAW also inherits PREOF from DetNet, which can be used to
   reorder packets before delivery to the upper layers.  As a result,
   DetNet in general and RAW in particular offer a smoother transport
   experience for the upper layers than the Internet at large, with
   ultra-low jitter and loss.

   RAW improves the reliability of transmissions and the availability of
   the communication resources and should be seen as a dynamic
   optimization of the use of redundancy to maintain reliability and
   availability metrics within certain boundaries.  For instance, ARQ
   (which provides one-hop reliability through acknowledgements and
   retries) and FEC codes (such as turbo codes which reduce the PER) are
   typically operated at Layer 2 and Layer 1, respectively.  In both
   cases, redundant transmissions improve the one-hop reliability at the
   expense of energy and latency, which are the resources that RAW must
   control.  In order to achieve its goals, RAW may leverage the lower-
   layer operations by abstracting the concept and providing hints to
   the lower layers on the desired outcome (e.g., in terms of
   reliability and timeliness), as opposed to performing the actual
   operations at Layer 3.

   Guarantees such as bounded latency depend on the upper layers
   (transport or application) to provide the payload in volumes and at
   times that match the contract with the DetNet sub-layers and the
   layers below.  An excess of incoming traffic at the DetNet ingress
   may result in dropping or queueing of packets and can entail loss,
   latency, or jitter; this violates the guarantees that are provided
   inside the DetNet Network.

   When the traffic from upper layers matches the expectation of the
   lower layers, RAW still depends on DetNet mechanisms and the lower
   layers to provide the timing and physical resource guarantees that
   are needed to match the traffic SLA.  When the availability of the
   physical resource varies, RAW acts on the distribution of the traffic
   to leverage alternates within a finite set of potential resources.

   The Operational Plane elements (routing and OAM control) may gather
   aggregated information from lower layers (e.g., information about
   link quality), via measurement or communication with the lower layer.
   This information may be obtained from inside the device using
   specialized APIs (e.g., L2 triggers) via monitoring and measurement
   protocols such as Bidirectional Forwarding Detection (BFD) [RFC5880]
   and Simple Two-way Active Measurement Protocol (STAMP) [RFC8762],
   respectively, or via a control protocol exchange with the lower layer
   (e.g., DLEP [DLEP]).  It may then be processed and exported through
   OAM messaging or via a YANG data model and exposed to the Controller
   Plane.

5.3.  RAW and DetNet

   RAW leverages the DetNet forwarding sub-layer and requires the
   support of OAM in DetNet transit nodes (see Figure 3 of
   [DetNet-ARCH]) for the dynamic acquisition of link capacity and state
   to maintain a strict RAW service end to end over a DetNet Network.
   In turn, DetNet and thus RAW may benefit from or leverage
   functionality such as that provided by TSN at the lower layers.

   RAW extends DetNet to improve the protection against link errors such
   as transient flapping that are far more common in wireless links.
   Nevertheless, for the most part, the RAW methods are applicable to
   wired links as well, e.g., when energy savings are desirable and the
   available path diversity exceeds 1+1 linear redundancy.

   RAW adds sub-layer functions that operate in the DetNet Operational
   Plane, which is part of the Network Plane.  The RAW orientation
   function may run only in the DetNet edge nodes (ingress edge node or
   End System), or it can also run in DetNet relay nodes when the RAW
   operations are distributed along the recovery graph.  The RAW Service
   sub-layer includes the PLR, which decides the DetNet path for the
   future packets of a flow along the DetNet path, Maintenance End
   Points (MEPs) on edge nodes, and Maintenance Intermediate Points
   (MIPs) within.  The MEPs trigger, and learn from, OAM observations
   and feed the PLR for its next decision.

   As illustrated in Figure 5, RAW extends the DetNet Stack (see
   Figure 4 of [DetNet-ARCH] and Figure 3) with additional functionality
   at the DetNet Service sub-layer for the actuation of PREOF based on
   the PLR decision.  DetNet operates at Layer 3, leveraging
   abstractions of the lower layers and APIs that control those
   abstractions.  For instance, DetNet already leverages lower layers
   for time-sensitive operations such as time synchronization and
   traffic shapers.  As the performances of the radio layers are subject
   to rapid changes, RAW needs more dynamic gauges and knobs.  To that
   effect, the LL API provides an abstraction to the DetNet layer that
   can be used to push reliability and timing hints, like suggesting X
   retries (min, max) within a time window or sending unicast (one next
   hop) or multicast (for overhearing).  In the other direction up the
   stack, the RAW PLR needs hints about the radio conditions such as L2
   triggers (e.g., RSSI, LQI, or ETX) over all the wireless hops.

   RAW uses various OAM functionalities at the different layers.  For
   instance, the OAM function in the DetNet Service sub-layer may
   perform Active and/or Hybrid OAM to estimate the link and path
   availability, either end to end or limited to a segment.  The RAW
   functions may be present in the Service sub-layer in DetNet edge and
   relay nodes.

     +-----------------+     +-------------------+
     |     Routing     |     |    OAM Control    |
     +-----------------+     +-------------------+


                                             Controller Plane
   +-+-+-+-+-+-+-+-+ Southbound Interface -+-+-+-+-+-+-+-+-+-+-+-+
                                              Network Plane

                                                   |
                   Operational Plane               .   Data Plane
                                                   |
     +-----------------+                           .
     |  Orientation    |                           |
     +-----------------+                           .
                                                   |
     +-----------------+   +-------------------+   .
     | Point of Local  |   |  OAM Maintenance  |   |
     | Repair (PLR)    |   |  End Point (MEP)  |   .
     +-----------------+   +-------------------+   |
                                                   .
                                                   |

        Figure 5: RAW Function Placement (Centralized Routing Case)

   There are two main proposed models to deploy RAW and DetNet: strict
   (Figure 6) and loose (Figure 7).  In the strict model, illustrated in
   Figure 6, RAW operates over a continuous DetNet service end to end
   between the ingress and the egress edge nodes or End Systems.

   In the loose model, illustrated in Figure 7, RAW may traverse a
   section of the network that is not serviced by DetNet.  RAW OAM may
   observe the end-to-end traffic and make the best of the available
   resources, but it may not expect the DetNet guarantees over all
   paths.  For instance, the packets between two wireless entities may
   be relayed over a wired infrastructure, in which case RAW observes
   and controls the transmission over the wireless first and last hops,
   as well as end-to-end metrics such as latency, jitter, and delivery
   ratio.  This operation is loose since the structure and properties of
   the wired infrastructure are ignored and may be either controlled by
   other means such as DetNet/TSN or neglected in the face of the
   wireless hops.

   A minimal forwarding sub-layer service is provided at all DetNet
   nodes to ensure that the OAM information flows.  DetNet relay nodes
   may or may not support RAW services, whereas the DetNet edge nodes
   are required to support RAW in any case.  DetNet guarantees, such as
   bounded latency, are provided end to end.  RAW extends the DetNet
   Service sub-layer to optimize the use of resources.

   --------------------Flow Direction---------------------------------->

   +---------+
   | RAW     |
   | Control |
   +---------+                           +---------+        +---------+
   | RAW +   |                           | RAW +   |        | RAW +   |
   | DetNet  |                           | DetNet  |        | DetNet  |
   | Service |                           | Service |        | Service |
   +---------+---------------------------+---------+--------+---------+
   |                       DetNet                                     |
   |                     Forwarding                                   |
   +------------------------------------------------------------------+

     Ingress             Transit            Relay              Egress
     Edge      ...       Nodes     ...      Nodes     ...        Edge
     Node                                                        Node

   <------------------End-to-End DetNet Service----------------------->

                  Figure 6: RAW over DetNet (Strict Model)

   In the loose model (illustrated in Figure 7), RAW operates over a
   partial DetNet service where typically only the ingress and the
   egress End Systems support RAW.  The DetNet domain may extend beyond
   the ingress node, or there may be a DetNet domain starting at an
   ingress edge node at the first hop after the End System.

   In the loose model, RAW cannot observe the hops in the network, and
   the path beyond the first hop is opaque; RAW can still observe the
   end-to-end behavior and use Layer 3 measurements to decide whether to
   replicate a packet and select the first-hop interface(s).

   --------------------Flow Direction---------------------------------->

   +---------+
   | RAW     |
   | Control |
   +---------+            +---------+                       +---------+
   | RAW +   |            | DetNet  |                       | RAW +   |
   | DetNet  |            |  Only   |                       | DetNet  |
   | Service |            | Service |                       | Service |
   +---------+----------------------+---+               +---+---------+
   |          DetNet                    |_______________|   DetNet    |
   |         Forwarding                  _______________  Forwarding  |
   +------------------------------------+               +-------------+

    Ingress    Transit       Relay           Tunnel             Egress
    End  ...   Nodes   ...   Nodes    ...                ...       End
    System                                                      System

   <---------------Partitioned DetNet Service------------------------->

                  Figure 7: RAW over DetNet (Loose Model)

6.  The RAW Control Loop

   The RAW architecture is based on an abstract OODA loop that controls
   the operation of a recovery graph.  The generic concept involves the
   following:

   1.  Operational Plane measurement protocols allow OAM to observe
       (like the first "O" in "OODA") some or all hops along a recovery
       graph as well as the end-to-end packet delivery.

   2.  The DetNet Controller Plane establishes primary and protection
       paths for use by the RAW Network Plane.  The orientation function
       reports data and information such as link statistics to be used
       by the routing function to compute, install, and maintain the
       recovery graphs.  The routing function may also generate
       intelligence such as a trained model for link quality prediction,
       which in turn can be used by the orientation function (like the
       second "O" in "OODA") to influence the path selection by the PLR
       within the RAW OODA loop.

   3.  A PLR operates at the DetNet Service sub-layer and hosts the
       decision function (like the "D" in "OODA").  The decision
       function determines which DetNet paths will be used for future
       packets that are routed within the recovery graph.

   4.  Service protection actions are actuated or triggered over the LL
       API by the PLR to increase the reliability of the end-to-end
       transmissions.  The RAW architecture also covers in-situ
       signaling that is embedded within live user traffic [RFC9378]
       (e.g., via OAM) when the decision is acted (like the "A" in
       "OODA") upon by a node that is downstream in the recovery graph
       from the PLR.

   The overall OODA loop optimizes the use of redundancy to achieve the
   required reliability and availability SLO(s) while minimizing the use
   of constrained resources such as spectrum and battery.

6.1.  Routing Timescale Versus Forwarding Timescale

   With DetNet, the Controller Plane Function (CPF) handles the routing
   computation and maintenance.  With RAW, the routing operation is
   segregated from the RAW control loop, so it may reside in the
   Controller Plane, whereas the control loop itself happens in the
   Network Plane.  To achieve RAW capabilities, the routing operation is
   extended to generate the information required by the orientation
   function in the loop.  For example, the routing function may propose
   DetNet paths to be used as a reflex action in response to network
   events or provide an aggregated history that the orientation function
   can use to make a decision.

   In a wireless mesh, the path to a routing function located in the
   Controller Plane can be expensive and slow, possibly going across the
   whole mesh and back.  Reaching the Controller Plane can also be slow
   in regard to the speed of events that affect the forwarding operation
   in the Network Plane at the radio layer.  Note that a distributed
   routing protocol may also take time and consume excessive wireless
   resources to reconverge to a new optimized state.

   As a result, the DetNet routing function is not expected to be aware
   of and react to very transient changes.  The abstraction of a link at
   the routing level is expected to use statistical metrics that
   aggregate the behavior of a link over long periods of time and
   represent its properties as shades of gray as opposed to numerical
   values such as a link quality indicator or a Boolean value for either
   up or down.

   The interaction between the network nodes and the routing function is
   handled by the orientation function, which reports to the routing
   function and sends control information in a digested form back to the
   RAW node to be used inside a forwarding control loop for traffic
   steering.

   Figure 8 illustrates a Network Plane recovery graph with links P-Q
   and N-E flapping, possibly in a transient fashion due to short-term
   interferences and possibly for a longer time (e.g., due to obstacles
   between the sender and the receiver or hardware failures).  In order
   to maintain a received redundancy around a value of 2 (for instance),
   RAW may leverage a higher ARQ on these hops if the overall latency
   permits the extra delay or enable alternate paths between ingress I
   and egress E.  For instance, RAW may enable protection path I ==> F
   ==> N ==> Q ==> M ==> R ==> E that routes around both issues and
   provides some degree of spatial diversity with protection path I ==>
   A ==> B ==> C ==> D ==> E.

                     +----------------+
                     |     DetNet     |
                     |    Routing     |
                     +----------------+
                             ^
                             |
                            Slow
                             |            Controller Plane
         _-._-._-._-._-._-.  |  ._-._-._-._-._-._-._-._-._-._-._-._-
       _-._-._-._-._-._-._-. | _-._-._-._-._-._-._-._-._-._-._-._-
                             |             Network Plane
                          Expensive
                             |
                    __...--- | ----.._.
                 .(          |          )-._
                (            v              ).
              (     A--------B---C----D       )
          _ -      / \          /      \       --._
         (        I---F--------N--***-- E           -
          -_       \          /        /             )
          (         P--***---Q----M---R             .
            _                                     )- ._
              -    <------ Fast ------->               )
             (                                   -._ .-
              (_.___.._____________.____.._ __-____)

      *** =  flapping at this time

                            Figure 8: Timescales

   In the case of wireless, the changes that affect the forwarding
   decision can happen frequently and often for short durations.  An
   example of this is a mobile object that moves between a transmitter
   and a receiver and cancels the line-of-sight transmission for a few
   seconds.  Another example is radar that measures the depth of a pool
   using the ISM band and interferes on a particular channel for a split
   second.

   Thus, there is a desire to separate the long-term computation of the
   route and the short-term forwarding decision.  In that model, the
   routing operation computes a recovery graph that enables multiple
   Unequal-Cost Multipath (UCMP) forwarding solutions along so-called
   protection paths and leaves it to the Network Plane to make the
   short-term decision of which of these possibilities should be used
   for which upcoming packets and flows.

   In the context of Traffic Engineering (TE), an alternate path can be
   used upon the detection of a failure in the main path, e.g., using
   OAM in Multiprotocol Label Switching - Transport Profile (MPLS-TP) or
   BFD over a collection of Software-Defined Wide Area Network (SD-WAN)
   tunnels.

   RAW formalizes a forwarding timescale that may be order(s) of
   magnitude shorter than the Controller Plane routing timescale and
   separates the protocols and metrics that are used at both scales.
   Routing can operate on long-term statistics such as delivery ratio
   over minutes to hours, but as a first approximation, it can ignore
   the cause of transient losses.  On the other hand, the RAW forwarding
   decision is made at the scale of a burst of packets and uses
   information that must be pertinent at the present time for the
   current transmission(s).

6.2.  OODA Loop

   The RAW architecture applies the generic OODA model to continuously
   optimize the spectrum and energy used to forward packets within a
   recovery graph, instantiating the OODA steps as follows:

   Observe:  Network Plane measurements, including protocols for OAM,
      observe the local state of the links and some or all hops along a
      recovery graph as well as the end-to-end packet delivery (see more
      in Section 6.3).  Information can also be provided by lower-layer
      interfaces such as DLEP.

   Orient:  The orientation function reports data and information such
      as the link statistics and leverages offline-computed wisdom and
      knowledge to orient the PLR for its forwarding decision (see more
      in Section 6.4).

   Decide:  A local PLR decides which DetNet path to use for future
      packet(s) that are routed along the recovery graph (see more in
      Section 6.5).

   Act:  PREOF Data Plane actions are controlled by the PLR over the LL
      API to increase the reliability of the end-to-end transmission.
      The RAW architecture also covers in-situ signaling when the
      decision is acted by a node that is down the recovery graph from
      the PLR (see more in Section 6.6).

                     +-------> Orientation ---------+
                     |        reflex actions        |
                     |       pre-trained model      |
                     |                              |
                   ......................................
                     |                              |
                     |        Service sub-layer     |
                     |                              v
                 Observe (OAM)                 Decide (PLR)
                     ^                              |
                     |                              |
                     |                              |
                     +------- Act (LL API) <--------+

                        Figure 9: The RAW OODA Loop

   The overall OODA loop optimizes the use of redundancy to achieve the
   required reliability and availability Service Level Agreement (SLA)
   while minimizing the use of constrained resources such as spectrum
   and battery.

6.3.  Observe: RAW OAM

   The RAW in-situ OAM operation in the Network Plane may observe either
   a full recovery graph or the DetNet path that is being used at this
   time.  As packets may be load balanced, replicated, eliminated, and/
   or fragmented for Network Coding FEC, the RAW in-situ operation needs
   to be able to signal which operation occurred to an individual
   packet.

   Active RAW OAM may be needed to observe the unused segments and
   evaluate the desirability of a rerouting decision.

   Finally, the RAW Service sub-layer Service Assurance may observe the
   individual PREOF operation of a DetNet relay node to ensure that it
   is conforming; this might require injecting an OAM packet at an
   upstream point inside the recovery graph and extracting that packet
   at another point downstream before it reaches the egress.

   This observation feeds the RAW PLR that makes the decision on which
   path is used at which RAW node, for one packet or a small continuous
   series of packets.

   In the case of end-to-end protection in a wireless mesh, the recovery
   graph is strict and congruent with the path so all links are
   observed.

   Conversely, in the case of Radio Access Protection, illustrated in
   Figure 10, the recovery graph is loose and only the first hop is
   observed; the rest of the path is abstracted and considered
   infinitely reliable.  The loss of a packet is attributed to the
   first-hop Radio Access Network (RAN), even if a particular loss
   effectively happens farther down the path.  In that case, RAW enables
   technology diversity (e.g., Wi-Fi and 5G), which in turn improves the
   diversity in spectrum usage.

                                     Opaque to OAM
                             <---------------------------->
                                     .-  .. - ..
                   RAN 1  --------(              ).__
      +-------+  /              (                    ).      +------+
      |Ingress|-              __________Tunnel_______________|Egress|
      |  End  |------ RAN 2 --_______________________________  End  |
      |System |-               (                        )    |System|
      +-------+  \            (                        ).    +------+
                  RAN n ----(                            )
                           (_______...___.__...____....__..)

              <-------L2------>
               Observed by OAM
              <----------------------L3----------------------->

            Figure 10: Observed Links in Radio Access Protection

   The links that are not observed by OAM are opaque to it, meaning that
   the OAM information is carried across and possibly echoed as data,
   but there is no information captured in intermediate nodes.  In the
   example above, the tunnel underlay is opaque and not controlled by
   RAW; still, RAW OAM measures the end-to-end latency and delivery
   ratio for packets sent via RAN 1, RAN 2, and RAN 3, and determines
   whether a packet should be sent over either access link or a
   collection of those access links.

6.4.  Orient: The RAW-Extended DetNet Operational Plane

   RAW separates the long timescale at which a recovery graph is
   computed and installed from the short timescale at which the
   forwarding decision is taken for one or a few packets (see
   Section 6.1) that experience the same path until the network
   conditions evolve and another path is selected within the same
   recovery graph.

   The recovery graph computation is out of scope, but RAW expects that
   the CPF that installs the recovery graph also provides related
   knowledge in the form of metadata about the links, segments, and
   possible DetNet paths.  That metadata can be a pre-digested
   statistical model and may include prediction of future flaps and
   packet loss, as well as recommended actions when that happens.

   The metadata may include:

   *  A set of pre-determined DetNet paths that are prepared to match
      expected link-degradation profiles, so the DetNet relay nodes can
      take reflex rerouting actions when facing a degradation that
      matches one such profile; and

   *  Link-quality statistics history and pre-trained models (e.g., to
      predict the short-term variation of quality of the links in a
      recovery graph).

   The recovery graph is installed with measurable objectives that are
   computed by the CPF to achieve the RAW SLA.  The objectives can be
   expressed as any of the maximum number of packets lost in a row,
   bounded latency, maximal jitter, maximum number of interleaved out-
   of-order packets, average number of copies received at the
   elimination point, and maximal delay between the first and the last
   received copy of the same packet.

6.5.  Decide: The Point of Local Repair

   The RAW OODA loop operates at the path selection timescale to provide
   agility versus the brute-force approach of flooding the whole
   recovery graph.  Within the redundant solutions that are proposed by
   the routing function, the OODA loop controls what is used for each
   packet and provides a reliable and available service while minimizing
   the waste of constrained resources.

   To that effect, RAW defines the Point of Local Repair (PLR), which
   performs rapid local adjustments of the forwarding tables within the
   path diversity that is available in that in the recovery graph.  The
   PLR enables exploitation of the richer forwarding capabilities at a
   faster timescale over a portion of the recovery graph, in either a
   loose or a strict fashion.

   The PLR operates on metrics that evolve quickly and need to be
   advertised at a fast rate (but only locally, within the recovery
   graph), and the PLR reacts to the metric updates by changing the
   DetNet path in use for the affected flows.

   The rapid changes in the forwarding decisions are made and contained
   within the scope of a recovery graph, and the actions of the PLR are
   not signaled outside the recovery graph.  This is as opposed to the
   routing function that must observe the whole network and optimize all
   the recovery graphs globally, which can only be done at a slow pace
   and with long-term statistical metrics, as presented in Table 1.

     +===============+=========================+=====================+
     |               | Controller Plane        | PLR                 |
     +===============+=========================+=====================+
     | Communication | Slow, distributed       | Fast, local         |
     +===============+-------------------------+---------------------+
     | Timescale     | Path computation +      | Lookup + protection |
     | (order)       | round trip,             | switch, micro to    |
     |               | milliseconds to seconds | milliseconds        |
     +===============+-------------------------+---------------------+
     | Network Size  | Large, many recovery    | Small, limited set  |
     |               | graphs to optimize      | of protection paths |
     |               | globally                |                     |
     +===============+-------------------------+---------------------+
     | Considered    | Averaged, statistical,  | Instantaneous       |
     | Metrics       | shade of grey           | values / boolean    |
     |               |                         | condition           |
     +===============+-------------------------+---------------------+

                  Table 1: Centralized Decision Versus PLR

   The PLR sits in the DetNet forwarding sub-layer of edge and relay
   nodes.  The PLR operates on the packet flow, learning the recovery
   graph and path-selection information from the packet and possibly
   making a local decision and retagging the packet to indicate so.  On
   the other hand, the PLR interacts with the lower layers (through
   triggers and DLEP) and with its peers (through OAM) to obtain up-to-
   date information about its links and the quality of the overall
   recovery graph, respectively, as illustrated in Figure 11.

                |
         Packet | going
       down the | stack
     +==========v==========+=====================+===================+
     |(In-situ OAM + iCTRL)| (L2 triggers, DLEP) |   (Hybrid OAM)    |
     +==========v==========+=====================+===================+
     |     Learn from      |                     |    Learn from     |
     |    packet tagging   >       Maintain      <    end-to-end     |
     +----------v----------+      Forwarding     |    OAM packets    |
     | Forwarding decision <        State        +---------^---------|
     +----------v----------+                     |      Enrich or    |
     +    Retag packet     |  Learn abstracted   >     regenerate    |
     |    and forward      | metrics about links |     OAM packets   |
     +..........v..........+..........^..........+........^.v........+
     |                          Lower layers                         |
     +..........v.....................^...................^.v........+
          Frame | sent          Frame | L2 ack     Active | | OAM
           over | wireless        in  |            in and | | out
                v                     |                   | v

                    Figure 11: PLR Conceptual Interfaces

6.6.  Act: DetNet Path Selection and Reliability Functions

   The main action by the PLR is the swapping of the DetNet path within
   the recovery graph for the future packets.  The candidate DetNet
   paths represent different energy and spectrum profiles and provide
   protection against different failures.

   The LL API enriches the DetNet protection services (PREOF) with the
   possibility to interact with lower-layer, one-hop reliability
   functions that are more typical with wireless links than with wired
   ones, including ARQ, FEC, and other techniques such as overhearing
   and constructive interferences.  Because RAW may be leveraged on
   wired links (e.g., to save power), it is not expected that all lower
   layers support all those capabilities.

   RAW provides hints to the lower-layer services on the desired
   outcome, and the lower layer acts on those hints to provide the best
   approximation of that outcome, e.g., a level of reliability for one-
   hop transmission within a bounded budget of time and/or energy.
   Thus, the LL API makes possible cross-layer optimization for
   reliability depending on the actual abstraction provided.  That is,
   some reliability functions are controlled from Layer 3 using an
   abstract interface, while they are really operated at the lower
   layers.

   The RAW path selection can be implemented in both centralized and
   distributed approaches.  In the centralized approach, the PLR may
   obtain a set of pre-computed DetNet paths matching a set of expected
   failures and apply the appropriate DetNet paths for the current state
   of the wireless links.  In the distributed approach, the signaling in
   the packet may be more abstract than an explicit path, and the PLR
   decision might be revised along the selected DetNet path based on a
   better knowledge of the rest of the way.

   The dynamic DetNet path selection in RAW avoids the waste of critical
   resources such as spectrum and energy while providing for the assured
   SLA, e.g., by rerouting and/or adding redundancy only when a loss
   spike is observed.

7.  Security Considerations

7.1.  Collocated Denial-of-Service Attacks

   RAW leverages diversity (e.g., spatial and time diversity, coding
   diversity, and frequency diversity), possibly using heterogeneous
   wired and wireless networking technologies over different physical
   paths, to increase reliability and availability in the face of
   unpredictable conditions.  While this is not done specifically to
   defeat an attacker, the amount of diversity used in RAW defeats
   possible attacks that would impact a particular technology or a
   specific path.

   Physical actions by a collocated attacker such as a radio
   interference may still lower the reliability of an end-to-end RAW
   transmission by blocking one segment or one possible path.  However,
   if an alternate path with diverse frequency, location, and/or
   technology is available, then RAW adapts by rerouting the impacted
   traffic over the preferred alternates, which defeats the attack after
   a limited period of lower reliability.  Then again, the security
   benefit is a side effect of an action that is taken regardless of
   whether or not the source of the issue is voluntary (an attack).

7.2.  Layer 2 Encryption

   Radio networks typically encrypt at the Media Access Control (MAC)
   layer to protect the transmission.  If the encryption is per pair of
   peers, then certain RAW operations like promiscuous overhearing
   become impractical.

7.3.  Forced Access

   A RAW policy typically selects the cheapest collection of links that
   matches the requested SLA, e.g., use free Wi-Fi versus paid 3GPP
   access.  By defeating the cheap connectivity (e.g., PHY-layer
   interference) the attacker can force an End System to use the paid
   access and increase the cost of the transmission for the user.

   Similar attacks may also be used to deplete resources in lower-power
   nodes by forcing additional transmissions for FEC and ARQ, and attack
   metrics such as battery life of the nodes.  By affecting the
   transmissions and the associated routing metrics in one area, an
   attacker may force the traffic and cause congestion along a remote
   path, thus reducing the overall throughput of the network.

8.  IANA Considerations

   This document has no IANA actions.

9.  References

9.1.  Normative References

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

   [DetNet-OAM]
              Mirsky, G., Theoleyre, F., Papadopoulos, G., Bernardos,
              CJ., Varga, B., and J. Farkas, "Framework of Operations,
              Administration, and Maintenance (OAM) for Deterministic
              Networking (DetNet)", RFC 9551, DOI 10.17487/RFC9551,
              March 2024, <https://www.rfc-editor.org/info/rfc9551>.

   [RAW-TECHNOS]
              Thubert, P., Ed., Cavalcanti, D., Vilajosana, X., Schmitt,
              C., and J. Farkas, "Reliable and Available Wireless (RAW)
              Technologies", RFC 9913, DOI 10.17487/RFC9913, April 2026,
              <https://www.rfc-editor.org/info/rfc9913>.

   [RFC4427]  Mannie, E., Ed. and D. Papadimitriou, Ed., "Recovery
              (Protection and Restoration) Terminology for Generalized
              Multi-Protocol Label Switching (GMPLS)", RFC 4427,
              DOI 10.17487/RFC4427, March 2006,
              <https://www.rfc-editor.org/info/rfc4427>.

   [RFC6291]  Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
              D., and S. Mansfield, "Guidelines for the Use of the "OAM"
              Acronym in the IETF", BCP 161, RFC 6291,
              DOI 10.17487/RFC6291, June 2011,
              <https://www.rfc-editor.org/info/rfc6291>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [RFC8557]  Finn, N. and P. Thubert, "Deterministic Networking Problem
              Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019,
              <https://www.rfc-editor.org/info/rfc8557>.

   [TSN]      IEEE, "Time-Sensitive Networking (TSN)",
              <https://1.ieee802.org/tsn/>.

9.2.  Informative References

   [6TiSCH-ARCH]
              Thubert, P., Ed., "An Architecture for IPv6 over the Time-
              Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
              RFC 9030, DOI 10.17487/RFC9030, May 2021,
              <https://www.rfc-editor.org/info/rfc9030>.

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

   [DetNet-PLANE]
              Malis, A., Geng, X., Ed., Chen, M., Varga, B., and CJ.
              Bernardos, "A Framework for the Deterministic Networking
              (DetNet) Controller Plane", RFC 9938,
              DOI 10.17487/RFC9938, March 2026,
              <https://www.rfc-editor.org/info/rfc9938>.

   [DLEP]     Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
              Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
              DOI 10.17487/RFC8175, June 2017,
              <https://www.rfc-editor.org/info/rfc8175>.

   [FRR]      Shand, M. and S. Bryant, "IP Fast Reroute Framework",
              RFC 5714, DOI 10.17487/RFC5714, January 2010,
              <https://www.rfc-editor.org/info/rfc5714>.

   [INT-ARCH] Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,
              <https://www.rfc-editor.org/info/rfc1122>.

   [NASA1]    Adams, T., "RELIABILITY: Definition & Quantitative
              Illustration", <https://extapps.ksc.nasa.gov/Reliability/
              Documents/150814-3bWhatIsReliability.pdf>.

   [NASA2]    Adams, T., "Availability",
              <https://extapps.ksc.nasa.gov/Reliability/
              Documents/160727.1_Availability_What_is_it.pdf>.

   [RAW-USE-CASES]
              Bernardos, CJ., Ed., Papadopoulos, G., Thubert, P., and F.
              Theoleyre, "Reliable and Available Wireless (RAW) Use
              Cases", RFC 9450, DOI 10.17487/RFC9450, August 2023,
              <https://www.rfc-editor.org/info/rfc9450>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

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

   [RFC3366]  Fairhurst, G. and L. Wood, "Advice to link designers on
              link Automatic Repeat reQuest (ARQ)", BCP 62, RFC 3366,
              DOI 10.17487/RFC3366, August 2002,
              <https://www.rfc-editor.org/info/rfc3366>.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              DOI 10.17487/RFC4090, May 2005,
              <https://www.rfc-editor.org/info/rfc4090>.

   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
              Computation Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [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, <https://www.rfc-editor.org/info/rfc6378>.

   [RFC6551]  Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
              and D. Barthel, "Routing Metrics Used for Path Calculation
              in Low-Power and Lossy Networks", RFC 6551,
              DOI 10.17487/RFC6551, March 2012,
              <https://www.rfc-editor.org/info/rfc6551>.

   [RFC8578]  Grossman, E., Ed., "Deterministic Networking Use Cases",
              RFC 8578, DOI 10.17487/RFC8578, May 2019,
              <https://www.rfc-editor.org/info/rfc8578>.

   [RFC8724]  Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
              Zuniga, "SCHC: Generic Framework for Static Context Header
              Compression and Fragmentation", RFC 8724,
              DOI 10.17487/RFC8724, April 2020,
              <https://www.rfc-editor.org/info/rfc8724>.

   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,
              <https://www.rfc-editor.org/info/rfc8762>.

   [RFC8939]  Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
              Bryant, "Deterministic Networking (DetNet) Data Plane:
              IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
              <https://www.rfc-editor.org/info/rfc8939>.

   [RFC9049]  Dawkins, S., Ed., "Path Aware Networking: Obstacles to
              Deployment (A Bestiary of Roads Not Taken)", RFC 9049,
              DOI 10.17487/RFC9049, June 2021,
              <https://www.rfc-editor.org/info/rfc9049>.

   [RFC9378]  Brockners, F., Ed., Bhandari, S., Ed., Bernier, D., and T.
              Mizrahi, Ed., "In Situ Operations, Administration, and
              Maintenance (IOAM) Deployment", RFC 9378,
              DOI 10.17487/RFC9378, April 2023,
              <https://www.rfc-editor.org/info/rfc9378>.

   [RFC9473]  Enghardt, R. and C. Krähenbühl, "A Vocabulary of Path
              Properties", RFC 9473, DOI 10.17487/RFC9473, September
              2023, <https://www.rfc-editor.org/info/rfc9473>.

   [RFC9544]  Mirsky, G., Halpern, J., Min, X., Clemm, A., Strassner,
              J., and J. François, "Precision Availability Metrics
              (PAMs) for Services Governed by Service Level Objectives
              (SLOs)", RFC 9544, DOI 10.17487/RFC9544, March 2024,
              <https://www.rfc-editor.org/info/rfc9544>.

   [RFC9633]  Geng, X., Ryoo, Y., Fedyk, D., Rahman, R., and Z. Li,
              "Deterministic Networking (DetNet) YANG Data Model",
              RFC 9633, DOI 10.17487/RFC9633, October 2024,
              <https://www.rfc-editor.org/info/rfc9633>.

   [RLFA-FRR] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
              So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
              RFC 7490, DOI 10.17487/RFC7490, April 2015,
              <https://www.rfc-editor.org/info/rfc7490>.

   [TE]       Farrel, A., Ed., "Overview and Principles of Internet
              Traffic Engineering", RFC 9522, DOI 10.17487/RFC9522,
              January 2024, <https://www.rfc-editor.org/info/rfc9522>.

Acknowledgments

   This architecture could never have been completed without the support
   and recommendations from the DetNet chairs Janos Farkas and Lou
   Berger, and from Dave Black, the DetNet Tech Advisor.  Many thanks to
   all of you.

   The authors wish to thank Ketan Talaulikar, as well as Balazs Varga,
   Dave Cavalcanti, Don Fedyk, Nicolas Montavont, and Fabrice Theoleyre
   for their in-depth reviews during the development of this document.

   The authors wish to thank Acee Lindem, Eva Schooler, Rich Salz,
   Wesley Eddy, Behcet Sarikaya, Brian Haberman, Gorry Fairhurst, Éric
   Vyncke, Erik Kline, Roman Danyliw, and Dave Thaler for their reviews
   and comments during the IETF Last Call and IESG review cycle.

   Special thanks for Mohamed Boucadair, Giuseppe Fioccola, and Benoit
   Claise for their help dealing with OAM technologies.

Contributors

   The editor wishes to thank the following individuals for their
   contributions to the text and the ideas discussed in this document:

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


   Xavi Vilajosana
   Wireless Networks Research Lab, Universitat Oberta de Catalunya
   Email: xvilajosana@gmail.com


   Geogios Papadopolous
   IMT Atlantique
   Email: georgios.papadopoulos@imt-atlantique.fr


   Remous-Aris Koutsiamanis
   IMT Atlantique
   Email: remous-aris.koutsiamanis@imt-atlantique.fr


   Rex Buddenberg
   Retired
   Email: buddenbergr@gmail.com


   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com


Author's Address

   Pascal Thubert (editor)
   Independent
   06330 Roquefort-les-Pins
   France
   Email: pascal.thubert@gmail.com
