



Internet Engineering Task Force (IETF)                     B. Varga, Ed.
Request for Comments: 8939                                     J. Farkas
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                                L. Berger
                                                                D. Fedyk
                                                 LabN Consulting, L.L.C.
                                                               S. Bryant
                                                  Futurewei Technologies
                                                           November 2020


            Deterministic Networking (DetNet) Data Plane: IP

Abstract

   This document specifies the Deterministic Networking (DetNet) data
   plane operation for IP hosts and routers that provide DetNet service
   to IP-encapsulated data.  No DetNet-specific encapsulation is defined
   to support IP flows; instead, the existing IP-layer and higher-layer
   protocol header information is used to support flow identification
   and DetNet service delivery.  This document builds on the DetNet
   architecture (RFC 8655) and data plane framework (RFC 8938).

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in 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/rfc8939.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Terminology
     2.1.  Terms Used in This Document
     2.2.  Abbreviations
     2.3.  Requirements Language
   3.  Overview of the DetNet IP Data Plane
   4.  DetNet IP Data Plane Considerations
     4.1.  End-System-Specific Considerations
     4.2.  DetNet Domain-Specific Considerations
     4.3.  Forwarding Sub-Layer Considerations
       4.3.1.  Class of Service
       4.3.2.  Quality of Service
       4.3.3.  Path Selection
     4.4.  DetNet Flow Aggregation
     4.5.  Bidirectional Traffic
   5.  DetNet IP Data Plane Procedures
     5.1.  DetNet IP Flow Identification Procedures
       5.1.1.  IP Header Information
       5.1.2.  Other Protocol Header Information
     5.2.  Forwarding Procedures
     5.3.  DetNet IP Traffic Treatment Procedures
   6.  Management and Control Information Summary
   7.  Security Considerations
   8.  IANA Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   Deterministic Networking (DetNet) is a service that can be offered by
   a network to DetNet flows.  DetNet provides these flows with
   extremely low packet loss rates and assured maximum end-to-end
   delivery latency.  General background and concepts of DetNet can be
   found in the DetNet architecture [RFC8655].

   This document specifies the DetNet data plane operation for IP hosts
   and routers that provide DetNet service to IP-encapsulated data.  No
   DetNet-specific encapsulation is defined to support IP flows;
   instead, the existing IP-layer and higher-layer protocol header
   information is used to support flow identification and DetNet service
   delivery.  Common data plane procedures and control information for
   all DetNet data planes can be found in [RFC8938].

   The DetNet architecture models the DetNet-related data plane
   functions as two sub-layers: a service sub-layer and a forwarding
   sub-layer.  The service sub-layer is used to provide DetNet service
   protection (e.g., by the Packet Replication Function (PRF) and Packet
   Elimination Function (PEF)) and reordering.  The forwarding sub-layer
   is used to provide congestion protection (low loss, assured latency,
   and limited out-of-order delivery).  The service sub-layer generally
   requires additional header fields to provide its service; for
   example, see [DetNet-MPLS].  Since no DetNet-specific fields are
   added to support DetNet IP flows, only the forwarding sub-layer
   functions are supported using the DetNet IP defined by this document.
   Service protection can be provided on a per-sub-network basis using
   technologies such as MPLS [DetNet-MPLS] and Ethernet, as specified by
   the IEEE 802.1 TSN (Time-Sensitive Networking) task group (referred
   to in this document simply as "IEEE 802.1 TSN").  See
   [IEEE802.1TSNTG].

   This document provides an overview of the DetNet IP data plane in
   Section 3 and considerations that apply to providing DetNet services
   via the DetNet IP data plane in Section 4.  Section 5 provides the
   procedures for hosts and routers that support IP-based DetNet
   services.  Section 6 summarizes the set of information that is needed
   to identify an individual DetNet flow.

2.  Terminology

2.1.  Terms Used in This Document

   This document uses the terminology and concepts established in the
   DetNet architecture [RFC8655], and it is assumed that the reader is
   familiar with that document and its terminology.

2.2.  Abbreviations

   The following abbreviations are used in this document:

   CoS           Class of Service

   DetNet        Deterministic Networking

   DN            DetNet

   Diffserv      Differentiated Services

   DSCP          Differentiated Services Code Point

   L2            Layer 2

   L3            Layer 3

   LSP           Label Switched Path

   MPLS          Multiprotocol Label Switching

   PEF           Packet Elimination Function

   PREOF         Packet Replication, Elimination, and Ordering Functions

   PRF           Packet Replication Function

   QoS           Quality of Service

   TSN           Time-Sensitive Networking.  TSN is a task group of the
                 IEEE 802.1 Working Group.

2.3.  Requirements Language

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

3.  Overview of the DetNet IP Data Plane

   This document describes how IP is used by DetNet nodes, i.e., hosts
   and routers, to identify DetNet flows and provide a DetNet service
   using an IP data plane.  From a data plane perspective, an end-to-end
   IP model is followed.  As mentioned above, existing IP-layer and
   higher-layer protocol header information is used to support flow
   identification and DetNet service delivery.  Common data plane
   procedures and control information for all DetNet data planes can be
   found in [RFC8938].

   The DetNet IP data plane primarily uses 6-tuple-based flow
   identification, where "6-tuple" refers to information carried in IP-
   layer and higher-layer protocol headers.  The 6-tuple referred to in
   this document is the same as that defined in [RFC3290].
   Specifically, the 6-tuple is destination address, source address, IP
   protocol, source port, destination port, and DSCP.  General
   background on the use of IP headers and 5-tuples to identify flows
   and support Quality of Service (QoS) can be found in [RFC3670].
   [RFC7657] also provides useful background on the delivery of Diffserv
   and tuple-based flow identification.  Note that a 6-tuple is composed
   of a 5-tuple plus the addition of a DSCP component.

   For some of the protocols, 5-tuples and 6-tuples cannot be used,
   because the port information is not available (e.g., ICMP, IPsec, and
   Encapsulating Security Payload (ESP)).  This is also the case for
   flow aggregates.  In such cases, using fewer fields is appropriate,
   such as a 3-tuple (2 IP addresses, IP protocol) or even a 2-tuple
   (all IP traffic between two IP addresses).

   The DetNet IP data plane also allows for optional matching on the
   IPv6 Flow Label field, as defined in [RFC8200].

   Non-DetNet and DetNet IP packets have the same protocol header format
   on the wire.  Generally, the fields used in flow identification are
   forwarded unmodified.  However, standard modification of the DSCP
   field [RFC2474] is not precluded.

   DetNet flow aggregation may be enabled via the use of wildcards,
   masks, lists, prefixes, and ranges.  IP tunnels may also be used to
   support flow aggregation.  In these cases, it is expected that
   DetNet-aware intermediate nodes will provide DetNet service on the
   aggregate through resource allocation and congestion control
   mechanisms.

   The specific procedures that are required to be implemented by a
   DetNet node supporting this document can be found in Section 5.  The
   DetNet Controller Plane, as defined in [RFC8655], is responsible for
   providing each node with the information needed to identify and
   handle each DetNet flow.

    DetNet IP       Relay                        Relay       DetNet IP
    End System      Node                         Node        End System

   +----------+                                             +----------+
   |   Appl.  |<------------ End-to-End Service ----------->|   Appl.  |
   +----------+  ............                 ...........   +----------+
   | Service  |<-: Service  :-- DetNet flow --: Service  :->| Service  |
   +----------+  +----------+                 +----------+  +----------+
   |Forwarding|  |Forwarding|                 |Forwarding|  |Forwarding|
   +--------.-+  +-.------.-+                 +-.---.----+  +-------.--+
            : Link :       \      ,-----.      /     \   ,-----.   /
            +......+        +----[  Sub- ]----+       +-[  Sub- ]-+
                                 [Network]              [Network]
                                  `-----'                `-----'

            |<--------------------- DetNet IP --------------------->|

                Figure 1: A Simple DetNet-Enabled IP Network

   Figure 1 illustrates a DetNet-enabled IP network.  The DetNet-enabled
   end systems originate IP-encapsulated traffic that is identified
   within the DetNet domain as DetNet flows based on IP header
   information.  Relay nodes understand the forwarding requirements of
   the DetNet flow and ensure that node, interface, and sub-network
   resources are allocated to ensure DetNet service requirements.  The
   dotted line around the Service component of the Relay Nodes indicates
   that the transit routers are DetNet service aware but do not perform
   any DetNet service sub-layer function, e.g., PREOF.

      |  Note: The sub-network can represent a TSN, MPLS network, or
      |  other network technology that can carry DetNet IP traffic.

    IP              Edge                        Edge         IP
    End System      Node                        Node         End System

   +----------+   +.........+                 +.........+   +----------+
   |   Appl.  |<--:Svc Proxy:-- E2E Service---:Svc Proxy:-->|   Appl.  |
   +----------+   +.........+                 +.........+   +----------+
   |    IP    |<--:IP : :Svc:---- IP flow ----:Svc: :IP :-->|    IP    |
   +----------+   +---+ +---+                 +---+ +---+   +----------+
   |Forwarding|   |Fwd| |Fwd|                 |Fwd| |Fwd|   |Forwarding|
   +--------.-+   +-.-+ +-.-+                 +-.-+ +-.-+   +---.------+
            :  Link :      \      ,-----.      /     /  ,-----.  \
            +.......+       +----[  Sub- ]----+     +--[  Sub- ]--+
                                 [network]             [network]
                                  `-----'               `-----'

         |<--- IP --->| |<------ DetNet IP ------>| |<--- IP --->|

      Figure 2: Non-DetNet-Aware IP End Systems with DetNet IP Domain

   Figure 2 illustrates a variant of Figure 1 where the end systems are
   not DetNet aware.  In this case, edge nodes sit at the boundary of
   the DetNet domain and provide DetNet service proxies for the end
   applications by initiating and terminating DetNet service for the
   application's IP flows.  The existing header information or an
   approach such as described in Section 4.4 can be used to support
   DetNet flow identification.

   Note that Figures 1 and 2 can be collapsed, so IP DetNet end systems
   can communicate over a DetNet IP network with IP end systems.

   As non-DetNet and DetNet IP packets have the same protocol header
   format on the wire, from a data plane perspective, the only
   difference is that there is flow-associated DetNet information on
   each DetNet node that defines the flow-related characteristics and
   required forwarding behavior.  As shown above, edge nodes provide a
   Service Proxy function that "associates" one or more IP flows with
   the appropriate DetNet flow-specific information and ensures that the
   flow receives the proper traffic treatment within the domain.

      |  Note: The operation of IEEE 802.1 TSN end systems over DetNet-
      |  enabled IP networks is not described in this document.  TSN
      |  over MPLS is described in [DetNet-TSN-over-MPLS].

4.  DetNet IP Data Plane Considerations

   This section provides considerations related to providing DetNet
   service to flows that are identified based on their header
   information.

4.1.  End-System-Specific Considerations

   Data flows requiring DetNet service are generated and terminated on
   end systems.  This document deals only with IP end systems.  The
   protocols used by an IP end system are specific to an application,
   and end systems peer with other end systems.  DetNet's use of 6-tuple
   IP flow identification means that DetNet must be aware of not only
   the format of the IP header, but also of the next protocol value
   carried within an IP packet (see Section 5.1.1.3).

   For DetNet-unaware IP end systems, service-level proxy functions are
   needed inside the DetNet domain.

   When IP end systems are DetNet aware, no application-level or
   service-level proxy functions are needed inside the DetNet domain.
   End systems need to ensure that DetNet service requirements are met
   when processing packets associated to a DetNet flow.  When sending
   packets, this means that packets are appropriately shaped on
   transmission and receive appropriate traffic treatment on the
   connected sub-network; see Sections 4.3.2 and 4.2 for more details.
   When receiving packets, this means that there are appropriate local
   node resources, e.g., buffers, to receive and process the packets of
   that DetNet flow.

   An important additional consideration for DetNet-aware end systems is
   avoiding IP fragmentation.  Full 6-tuple flow identification is not
   possible on IP fragments, as fragments don't include the transport
   headers or their port information.  As such, it is important that
   applications and/or end systems use an IP packet size that will avoid
   fragmentation within the network when sending DetNet flows.  The
   maximum size can be learned via Path MTU Discovery [RFC1191]
   [RFC8201] or via the Controller Plane.  Note that Path MTU Discovery
   relies on ICMP, which may not follow the same path as an individual
   DetNet flow.

   In order to maximize reuse of existing mechanisms, DetNet-aware
   applications and end systems SHOULD NOT mix DetNet and non-DetNet
   traffic within a single 5-tuple.

4.2.  DetNet Domain-Specific Considerations

   As a general rule, DetNet IP domains need to be able to forward any
   DetNet flow identified by the IP 6-tuple.  Doing otherwise would
   limit the number of 6-tuple flow ID combinations that could be used
   by the end systems.  From a practical standpoint, this means that all
   nodes along the end-to-end path of DetNet flows need to agree on what
   fields are used for flow identification.  Possible consequences of
   not having such an agreement include some flows interfering with
   other flows, and the traffic treatment expected for a service not
   being provided.

   From a connection-type perspective, two scenarios are identified:

   1.  DN attached: the end system is directly connected to an edge node
       or the end system is behind a sub-network.  (See ES1 and ES2 in
       Figure 3.)

   2.  DN integrated: the end system is part of the DetNet domain.  (See
       ES3 in Figure 3.)

   L3 (IP) end systems may use any of these connection types.  A DetNet
   domain allows communication between any end systems using the same
   encapsulation format, independent of their connection type and DetNet
   capability.  DN-attached end systems have no knowledge about the
   DetNet domain and its encapsulation format.  See Figure 3 for L3 end
   system connection examples.

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

                Figure 3: Connection Types of L3 End Systems

   Within a DetNet domain, the DetNet-enabled IP routers are
   interconnected by links and sub-networks to support end-to-end
   delivery of DetNet flows.  From a DetNet architecture perspective,
   these routers are DetNet relays, as they must be DetNet service
   aware.  Such routers identify DetNet flows based on the IP 6-tuple
   and ensure that the traffic treatment required by the DetNet service
   is provided on both the node and any attached sub-network.

   This solution provides DetNet functions end to end, but it does so on
   a per-link and per-sub-network basis.  Congestion protection, latency
   control, and resource allocation (queuing, policing, shaping) are
   supported using the underlying link/sub-network-specific mechanisms.
   However, service protection (PRF and PEF) is not provided end to end
   at the DetNet layer.  Instead, service protection can be provided on
   a per-link (underlying L2 link) and per-sub-network basis.

   The DetNet service flow is mapped to the link/sub-network-specific
   resources using an underlying system-specific means.  This implies
   that each DetNet-aware node on the path looks into the forwarded
   DetNet service flow packet and utilizes, for example, a 6-tuple to
   find out the required mapping within a node.

   As noted earlier, service protection must be implemented within each
   link/sub-network independently, using the domain-specific mechanisms.
   This is due to the lack of unified end-to-end sequencing information
   that could be used by the intermediate nodes.  Therefore, service
   protection (if enabled) cannot be provided end to end, only within
   sub-networks.  This is shown for a scenario with three sub-networks
   in Figure 4, where each sub-network can provide service protection
   between its borders.  "R" and "E" denote replication and elimination
   points within the sub-network.

        <-------------------- DetNet IP ------------------------>
                                    ______
                          ____     /      \__
               ____      /     \__/          \___   ______
   +----+   __/    +====+                       +==+      \     +----+
   |src |__/ Sub-N1 )   |                       |  \ Sub-N3\____| dst|
   +----+  \_______/    \      Sub-network 2    |   \______/    +----+
                         \_                    _/
                           \         __     __/
                            \_______/  \___/


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

      Figure 4: Replication and Elimination in Sub-networks for DetNet
                                IP Networks

   If end-to-end service protection is desired, it can be implemented --
   for example, by the DetNet end systems using Layer 4 (L4) transport
   protocols or application protocols.  However, these protocols are out
   of the scope of this document.

   Note that not mixing DetNet and non-DetNet traffic within a single
   5-tuple, as described above, enables simpler 5-tuple filters to be
   used (or reused) at the edges of a DetNet network to prevent non-
   congestion-responsive DetNet traffic from escaping the DetNet domain.

4.3.  Forwarding Sub-Layer Considerations

4.3.1.  Class of Service

   Class of Service (CoS) for DetNet flows carried in IPv4 and IPv6 is
   provided using the standard DSCP field [RFC2474] and related
   mechanisms.

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

4.3.2.  Quality of Service

   Quality of Service (QoS) for DetNet service flows carried in IP must
   be provided locally by the DetNet-aware hosts and routers supporting
   DetNet flows.  Such support leverages the underlying network layer
   such as 802.1 TSN.  The node-internal traffic control mechanisms used
   to deliver QoS for IP-encapsulated DetNet flows are outside the scope
   of this document.  From an encapsulation perspective, the combination
   of the 6-tuple (the typical 5-tuple enhanced with the DSCP) and
   optionally the flow label uniquely identifies a DetNet IP flow.

   Packets that are identified as part of a DetNet IP flow but that have
   not been the subject of a completed reservation can disrupt the QoS
   offered to properly reserved DetNet flows by using resources
   allocated to the reserved flows.  Therefore, the network nodes of a
   DetNet network MUST ensure that no DetNet-allocated resource, e.g.,
   queue or shaper, is used by such flows.  There are multiple methods
   that may be used by an implementation to defend service delivery to
   reserved DetNet flows, including but not limited to:

   *  Treating packets associated with an incomplete reservation as non-
      DetNet traffic.

   *  Discarding packets associated with an incomplete reservation.

   *  Re-marking packets associated with an incomplete reservation.  Re-
      marking can be accomplished by changing the value of the DSCP
      field to a value that results in the packet no longer matching any
      other reserved DetNet IP flow.

4.3.3.  Path Selection

   While path selection algorithms and mechanisms are out of the scope
   of the DetNet data plane definition, it is important to highlight the
   implications of DetNet IP flow identification on path selection and
   next hops.  As mentioned above, the DetNet IP data plane identifies
   flows using 6-tuple header information as well as the optional (flow
   label) header field.  DetNet generally allows for both flow-specific
   traffic treatment and flow-specific next hops.

   In non-DetNet IP forwarding, it is generally assumed that the same
   series of next hops, i.e., the same path, will be used for a
   particular 5-tuple or, in some cases (e.g., [RFC5120]), for a
   particular 6-tuple.  Using different next hops for different 5-tuples
   does not take any special consideration for DetNet-aware
   applications.

   Care should be taken when using different next hops for the same
   5-tuple.  As discussed in [RFC7657], unexpected behavior can occur
   when a single 5-tuple application flow experiences reordering due to
   being split across multiple next hops.  Understanding of the
   application and transport protocol impact of using different next
   hops for the same 5-tuple is required.  Again, this only indirectly
   impacts path selection for DetNet flows and this document.

4.4.  DetNet Flow Aggregation

   As described in [RFC8938], the ability to aggregate individual flows
   and their associated resource control into a larger aggregate is an
   important technique for improving scaling by reducing the state per
   hop.  DetNet IP data plane aggregation can take place within a single
   node, when that node maintains state about both the aggregated and
   individual flows.  It can also take place between nodes, when one
   node maintains state about only flow aggregates while the other node
   maintains state on all or a portion of the component flows.  In
   either case, the management or control function that provisions the
   aggregate flows must ensure that adequate resources are allocated and
   configured to provide the combined service requirements of the
   individual flows.  As DetNet is concerned about latency and jitter,
   more than just bandwidth needs to be considered.

   From a single node perspective, the aggregation of IP flows impacts
   DetNet IP data plane flow identification and resource allocation.  As
   discussed above, IP flow identification uses the IP 6-tuple for flow
   identification.  DetNet IP flows can be aggregated using any of the
   6-tuple fields and optionally also by the flow label.  The use of
   prefixes, wildcards, lists, and value ranges allows a DetNet node to
   identify aggregate DetNet flows.  From a resource allocation
   perspective, DetNet nodes ought to provide service to an aggregate
   rather than on a component flow basis.

   It is the responsibility of the DetNet Controller Plane to properly
   provision the use of these aggregation mechanisms.  This includes
   ensuring that aggregated flows have compatible (e.g., the same or
   very similar) QoS and/or CoS characteristics; see Section 4.3.2.  It
   also includes ensuring that per-component-flow service requirements
   are satisfied by the aggregate; see Section 5.3.

   The DetNet Controller Plane MUST ensure that non-congestion-
   responsive DetNet traffic is not forwarded outside a DetNet domain.

4.5.  Bidirectional Traffic

   While the DetNet IP data plane must support bidirectional DetNet
   flows, there are no special bidirectional features within the data
   plane.  The special case of co-routed bidirectional DetNet flows is
   solely represented at the management and control plane levels,
   without specific support or knowledge within the DetNet data plane.
   Fate sharing and associated or co-routed bidirectional flows can be
   managed at the control level.

   Control and management mechanisms need to support bidirectional
   flows, but the specification of such mechanisms is out of the scope
   of this document.  An example control plane solution for MPLS can be
   found in [RFC7551].

5.  DetNet IP Data Plane Procedures

   This section provides DetNet IP data plane procedures.  These
   procedures have been divided into the following areas: flow
   identification, forwarding, and traffic treatment.  Flow
   identification includes those procedures related to matching IP-layer
   and higher-layer protocol header information to DetNet flow (state)
   information and service requirements.  Flow identification is also
   sometimes called "traffic classification"; for example, see
   [RFC5777].  Forwarding includes those procedures related to next-hop
   selection and delivery.  Traffic treatment includes those procedures
   related to providing an identified flow with the required DetNet
   service.

   DetNet IP data plane establishment and operational procedures also
   have requirements on the control and management systems for DetNet
   flows, and these are referred to in this section.  Specifically, this
   section identifies a number of information elements that require
   support via the management and control interfaces supported by a
   DetNet node.  The specific mechanism used for such support is out of
   the scope of this document.  A summary of the requirements for
   management- and control-related information is included.  Conformance
   language is not used in the summary, since it applies to future
   mechanisms such as those that may be provided in YANG models
   [DetNet-YANG].

5.1.  DetNet IP Flow Identification Procedures

   IP-layer and higher-layer protocol header information is used to
   identify DetNet flows.  All DetNet implementations that support this
   document MUST identify individual DetNet flows based on the set of
   information identified in this section.  Note that additional
   requirements for flow identification, e.g., to support other higher-
   layer protocols, may be defined in the future.

   The configuration and control information used to identify an
   individual DetNet flow MUST be ordered by an implementation.
   Implementations MUST support a fixed order when identifying flows and
   MUST identify a DetNet flow by the first set of matching flow
   information.

   Implementations of this document MUST support DetNet flow
   identification when the implementation is acting as a DetNet end
   system, a relay node, or an edge node.

5.1.1.  IP Header Information

   Implementations of this document MUST support DetNet flow
   identification based on IP header information.  The IPv4 header is
   defined in [RFC0791], and the IPv6 is defined in [RFC8200].

5.1.1.1.  Source Address Field

   Implementations of this document MUST support DetNet flow
   identification based on the Source Address field of an IP packet.
   Implementations SHOULD support longest prefix matching for this field
   (see [RFC1812] and [RFC7608]).  Note that a prefix length of zero (0)
   effectively means that the field is ignored.

5.1.1.2.  Destination Address Field

   Implementations of this document MUST support DetNet flow
   identification based on the Destination Address field of an IP
   packet.  Implementations SHOULD support longest prefix matching for
   this field (see [RFC1812] and [RFC7608]).  Note that a prefix length
   of zero (0) effectively means that the field is ignored.

      |  Note: Any IP address value is allowed, including an IP
      |  multicast destination address.

5.1.1.3.  IPv4 Protocol and IPv6 Next Header Fields

   Implementations of this document MUST support DetNet flow
   identification based on the IPv4 Protocol field when processing IPv4
   packets and the IPv6 Next Header field when processing IPv6 packets.
   This includes the next protocol values defined in Section 5.1.2 and
   any other value, including zero.  Implementations SHOULD allow for
   these fields to be ignored for a specific DetNet flow.

5.1.1.4.  IPv4 Type of Service and IPv6 Traffic Class Fields

   These fields are used to support differentiated services [RFC2474]
   [RFC2475].  Implementations of this document MUST support DetNet flow
   identification based on the DSCP field in the IPv4 Type of Service
   field when processing IPv4 packets and the DSCP field in the IPv6
   Traffic Class field when processing IPv6 packets.  Implementations
   MUST support list-based matching of DSCP values, where the list is
   composed of possible field values that are to be considered when
   identifying a specific DetNet flow.  Implementations SHOULD allow for
   this field to be ignored for a specific DetNet flow.

5.1.1.5.  IPv6 Flow Label Field

   Implementations of this document SHOULD support identification of
   DetNet flows based on the IPv6 Flow Label field.  Implementations
   that support matching based on this field MUST allow for it to be
   ignored for a specific DetNet flow.  When this field is used to
   identify a specific DetNet flow, implementations MAY exclude the IPv6
   Next Header field and next header information as part of DetNet flow
   identification.

5.1.2.  Other Protocol Header Information

   Implementations of this document MUST support DetNet flow
   identification based on header information identified in this
   section.  Support for TCP, UDP, ICMP, and IPsec flows is defined.
   Future documents are expected to define support for other protocols.

5.1.2.1.  TCP and UDP

   DetNet flow identification for TCP [RFC0793] and UDP [RFC0768] is
   achieved based on the Source and Destination Port fields carried in
   each protocol's header.  These fields share a common format and
   common DetNet flow identification procedures.

   The rules defined in this section only apply when the IPv4 Protocol
   or IPv6 Next Header field contains the IANA-defined value for UDP or
   TCP.

5.1.2.1.1.  Source Port Field

   Implementations of this document MUST support DetNet flow
   identification based on the Source Port field of a TCP or UDP packet.
   Implementations MUST support flow identification based on a
   particular value carried in the field, i.e., an exact value.
   Implementations SHOULD support range-based port matching.
   Implementation MUST also allow for the field to be ignored for a
   specific DetNet flow.

5.1.2.1.2.  Destination Port Field

   Implementations of this document MUST support DetNet flow
   identification based on the Destination Port field of a TCP or UDP
   packet.  Implementations MUST support flow identification based on a
   particular value carried in the field, i.e., an exact value.
   Implementations SHOULD support range-based port matching.
   Implementation MUST also allow for the field to be ignored for a
   specific DetNet flow.

5.1.2.2.  ICMP

   DetNet flow identification for ICMP [RFC0792] is achieved based on
   the protocol number in the IP header.  Note that ICMP type is not
   included in the flow definition.

5.1.2.3.  IPsec AH and ESP

   IPsec Authentication Header (AH) [RFC4302] and Encapsulating Security
   Payload (ESP) [RFC4303] share a common format for the Security
   Parameters Index (SPI) field.  Implementations MUST support flow
   identification based on a particular value carried in the field,
   i.e., an exact value.  Implementations SHOULD also allow for the
   field to be ignored for a specific DetNet flow.

   The rules defined in this section only apply when the IPv4 Protocol
   or IPv6 Next Header field contains the IANA-defined value for AH or
   ESP.

5.2.  Forwarding Procedures

   General requirements for IP nodes are defined in [RFC1122],
   [RFC1812], and [RFC8504] and are not modified by this document.  The
   typical next-hop selection process is impacted by DetNet.
   Specifically, implementations of this document SHALL use management
   and control information to select the one or more outgoing interfaces
   and next hops to be used for a packet associated with a DetNet flow.
   Specific management and control information will be defined in future
   documents, e.g., [DetNet-YANG].

   The use of multiple paths or links, e.g., ECMP, to support a single
   DetNet flow is NOT RECOMMENDED.  ECMP MAY be used for non-DetNet
   flows within a DetNet domain.

   The above implies that management and control functions will be
   defined to support this requirement, e.g., see [DetNet-YANG].

5.3.  DetNet IP Traffic Treatment Procedures

   Implementations of this document must ensure that a DetNet flow
   receives the traffic treatment that is provisioned for it via
   configuration or the Controller Plane, e.g., via [DetNet-YANG].
   General information on DetNet service can be found in
   [DetNet-Flow-Info].  Typical mechanisms used to provide different
   treatment to different flows include the allocation of system
   resources (such as queues and buffers) and provisioning of related
   parameters (such as shaping and policing).  Support can also be
   provided via an underlying network technology such as MPLS
   [DetNet-IP-over-MPLS] or IEEE 802.1 TSN [DetNet-IP-over-TSN].  Other
   mechanisms than the ones used in the TSN case are outside the scope
   of this document.

6.  Management and Control Information Summary

   The following summarizes the set of information that is needed to
   identify individual and aggregated DetNet flows:

   *  IPv4 and IPv6 Source Address field.

   *  IPv4 and IPv6 source address prefix length, where a zero (0) value
      effectively means that the Source Address field is ignored.

   *  IPv4 and IPv6 Destination Address field.

   *  IPv4 and IPv6 destination address prefix length, where a zero (0)
      value effectively means that the Destination Address field is
      ignored.

   *  IPv4 Protocol field.  A limited set of values is allowed, and the
      ability to ignore this field is desirable.

   *  IPv6 Next Header field.  A limited set of values is allowed, and
      the ability to ignore this field is desirable.

   *  For the IPv4 Type of Service and IPv6 Traffic Class fields:

      -  Whether or not the DSCP field is used in flow identification.
         Use of the DSCP field for flow identification is optional.

      -  If the DSCP field is used to identify a flow, then the flow
         identification information (for that flow) includes a list of
         DSCPs used by that flow.

   *  IPv6 Flow Label field.  This field can be optionally used for
      matching.  When used, this field can be used instead of matching
      against the Next Header field.

   *  TCP and UDP Source Port.  Support for both exact and wildcard
      matching is required.  Port ranges can optionally be used.

   *  TCP and UDP Destination Port.  Support for both exact and wildcard
      matching is required.  Port ranges can optionally be used.

   *  IPsec Header SPI field.  Exact matching is required.  Support for
      wildcard matching is recommended.

   *  For end systems, an optional maximum IP packet size that should be
      used for that outgoing DetNet IP flow.

   This information MUST be provisioned per DetNet flow via
   configuration, e.g., via the Controller Plane or the management
   plane.

   An implementation MUST support ordering of the set of information
   used to identify an individual DetNet flow.  This can, for example,
   be used to provide a DetNet service for a specific UDP flow, with
   unique Source and Destination Port field values, while providing a
   different service for the aggregate of all other flows with that same
   UDP Destination Port value.

   It is the responsibility of the DetNet Controller Plane to properly
   provision both flow identification information and the flow-specific
   resources needed to provide the traffic treatment needed to meet each
   flow's service requirements.  This applies for aggregated and
   individual flows.

7.  Security Considerations

   Detailed security considerations for DetNet are cataloged in
   [DetNet-Security], and more general security considerations are
   described in [RFC8655].  This section exclusively considers security
   considerations that are specific to the DetNet IP data plane.

   Security aspects that are unique to DetNet are those whose aim is to
   provide the specific QoS aspects of DetNet, which are primarily to
   deliver data flows with extremely low packet loss rates and bounded
   end-to-end delivery latency.  Achieving such loss rates and bounded
   latency may not be possible in the face of a highly capable
   adversary, such as the one envisioned by the Internet Threat Model of
   BCP 72 [RFC3552] that can arbitrarily drop or delay any or all
   traffic.  In order to present meaningful security considerations, we
   consider a somewhat weaker attacker who does not control the physical
   links of the DetNet domain but may have the ability to control a
   network node within the boundary of the DetNet domain.

   The primary consideration for the DetNet data plane is to maintain
   integrity of data and delivery of the associated DetNet service
   traversing the DetNet network.  Since no DetNet-specific fields are
   available in the DetNet IP data plane, the integrity and
   confidentiality of application flows can be protected through
   whatever means are provided by the underlying technology.  For
   example, encryption may be used, such as that provided by IPsec
   [RFC4301] for IP flows and/or by an underlying sub-network using
   MACsec [IEEE802.1AE-2018] for IP over Ethernet (Layer 2) flows.

   From a data plane perspective, this document does not add or modify
   any header information.

   At the management and control level, DetNet flows are identified on a
   per-flow basis, which may provide Controller Plane attackers with
   additional information about the data flows (when compared to
   Controller Planes that do not include per-flow identification).  This
   is an inherent property of DetNet that has security implications that
   should be considered when determining if DetNet is a suitable
   technology for any given use case.

   To provide uninterrupted availability of the DetNet service,
   provisions can be made against DoS attacks and delay attacks.  To
   protect against DoS attacks, excess traffic due to malicious or
   malfunctioning devices can be prevented or mitigated -- for example,
   through the use of existing mechanisms such as policing and shaping
   applied at the input of a DetNet domain or within an edge IEEE 802.1
   TSN domain.  To prevent DetNet packets from being delayed by an
   entity external to a DetNet domain, DetNet technology definitions can
   allow for the mitigation of man-in-the-middle attacks -- for example,
   through the use of authentication and authorization of devices within
   the DetNet domain.

8.  IANA Considerations

   This document has no IANA actions.

9.  References

9.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

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

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <https://www.rfc-editor.org/info/rfc792>.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC1812]  Baker, F., Ed., "Requirements for IP Version 4 Routers",
              RFC 1812, DOI 10.17487/RFC1812, June 1995,
              <https://www.rfc-editor.org/info/rfc1812>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC7608]  Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix
              Length Recommendation for Forwarding", BCP 198, RFC 7608,
              DOI 10.17487/RFC7608, July 2015,
              <https://www.rfc-editor.org/info/rfc7608>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

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

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

9.2.  Informative References

   [DetNet-Flow-Info]
              Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D.
              Fedyk, "DetNet Flow Information Model", Work in Progress,
              Internet-Draft, draft-ietf-detnet-flow-information-model-
              11, 21 October 2020, <https://tools.ietf.org/html/draft-
              ietf-detnet-flow-information-model-11>.

   [DetNet-IP-over-MPLS]
              Varga, B., Ed., Berger, L., Fedyk, D., Bryant, S., and J.
              Korhonen, "DetNet Data Plane: IP over MPLS", Work in
              Progress, Internet-Draft, draft-ietf-detnet-ip-over-mpls-
              09, 11 October 2020, <https://tools.ietf.org/html/draft-
              ietf-detnet-ip-over-mpls-09>.

   [DetNet-IP-over-TSN]
              Varga, B., Ed., Farkas, J., Malis, A., and S. Bryant,
              "DetNet Data Plane: IP over IEEE 802.1 Time Sensitive
              Networking (TSN)", Work in Progress, Internet-Draft,
              draft-ietf-detnet-ip-over-tsn-04, 2 November 2020,
              <https://tools.ietf.org/html/draft-ietf-detnet-ip-over-
              tsn-04>.

   [DetNet-MPLS]
              Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
              S., and J. Korhonen, "DetNet Data Plane: MPLS", Work in
              Progress, Internet-Draft, draft-ietf-detnet-mpls-13, 11
              October 2020,
              <https://tools.ietf.org/html/draft-ietf-detnet-mpls-13>.

   [DetNet-Security]
              Grossman, E., Ed., Mizrahi, T., and A. Hacker,
              "Deterministic Networking (DetNet) Security
              Considerations", Work in Progress, Internet-Draft, draft-
              ietf-detnet-security-12, 2 October 2020,
              <https://tools.ietf.org/html/draft-ietf-detnet-security-
              12>.

   [DetNet-TSN-over-MPLS]
              Varga, B., Ed., Farkas, J., Malis, A., Bryant, S., and D.
              Fedyk, "DetNet Data Plane: IEEE 802.1 Time Sensitive
              Networking over MPLS", Work in Progress, Internet-Draft,
              draft-ietf-detnet-tsn-vpn-over-mpls-04, 2 November 2020,
              <https://tools.ietf.org/html/draft-ietf-detnet-tsn-vpn-
              over-mpls-04>.

   [DetNet-YANG]
              Geng, X., Chen, M., Ryoo, Y., Fedyk, D., Rahman, R., and
              Z. Li, "Deterministic Networking (DetNet) Configuration
              YANG Model", Work in Progress, Internet-Draft, draft-ietf-
              detnet-yang-09, 16 November 2020,
              <https://tools.ietf.org/html/draft-ietf-detnet-yang-09>.

   [IEEE802.1AE-2018]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks-Media Access Control (MAC) Security", IEEE 
              802.1AE-2018, DOI 10.1109/IEEESTD.2018.8585421, December
              2018, <https://ieeexplore.ieee.org/document/8585421>.

   [IEEE802.1TSNTG]
              IEEE, "Time-Sensitive Networking (TSN) Task Group",
              <https://1.ieee802.org/tsn/>.

   [RFC1122]  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>.

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,
              <https://www.rfc-editor.org/info/rfc1191>.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/info/rfc2475>.

   [RFC3290]  Bernet, Y., Blake, S., Grossman, D., and A. Smith, "An
              Informal Management Model for Diffserv Routers", RFC 3290,
              DOI 10.17487/RFC3290, May 2002,
              <https://www.rfc-editor.org/info/rfc3290>.

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

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <https://www.rfc-editor.org/info/rfc3552>.

   [RFC3670]  Moore, B., Durham, D., Strassner, J., Westerinen, A., and
              W. Weiss, "Information Model for Describing Network Device
              QoS Datapath Mechanisms", RFC 3670, DOI 10.17487/RFC3670,
              January 2004, <https://www.rfc-editor.org/info/rfc3670>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5777]  Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M.,
              Ed., and A. Lior, "Traffic Classification and Quality of
              Service (QoS) Attributes for Diameter", RFC 5777,
              DOI 10.17487/RFC5777, February 2010,
              <https://www.rfc-editor.org/info/rfc5777>.

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

   [RFC7657]  Black, D., Ed. and P. Jones, "Differentiated Services
              (Diffserv) and Real-Time Communication", RFC 7657,
              DOI 10.17487/RFC7657, November 2015,
              <https://www.rfc-editor.org/info/rfc7657>.

   [RFC8201]  McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
              "Path MTU Discovery for IP version 6", STD 87, RFC 8201,
              DOI 10.17487/RFC8201, July 2017,
              <https://www.rfc-editor.org/info/rfc8201>.

   [RFC8504]  Chown, T., Loughney, J., and T. Winters, "IPv6 Node
              Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504,
              January 2019, <https://www.rfc-editor.org/info/rfc8504>.

Acknowledgements

   The authors wish to thank Pat Thaler, Norman Finn, Loa Andersson,
   David Black, Rodney Cummings, Ethan Grossman, Tal Mizrahi, David
   Mozes, Craig Gunther, George Swallow, Yuanlong Jiang, and Carlos
   J. Bernardos for their various contributions to this work.  David
   Black served as technical advisor to the DetNet working group during
   the development of this document and provided many valuable comments.
   IESG comments were provided by Murray Kucherawy, Roman Danyliw,
   Alvaro Retana, Benjamin Kaduk, Rob Wilton, and Érik Vyncke.

Contributors

   The editor of this document wishes to thank and acknowledge the
   following people who contributed substantially to the content of this
   document and should be considered coauthors:

   Jouni Korhonen

   Email: jouni.nospam@gmail.com


   Andrew G. Malis
   Malis Consulting

   Email: agmalis@gmail.com


Authors' Addresses

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

   Email: balazs.a.varga@ericsson.com


   János Farkas
   Ericsson
   Budapest
   Magyar Tudosok krt. 11.
   1117
   Hungary

   Email: janos.farkas@ericsson.com


   Lou Berger
   LabN Consulting, L.L.C.

   Email: lberger@labn.net


   Don Fedyk
   LabN Consulting, L.L.C.

   Email: dfedyk@labn.net


   Stewart Bryant
   Futurewei Technologies

   Email: sb@stewartbryant.com
