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Versions: 00 01 02 03 04 05 06 07 rfc9023                               
DetNet                                                     B. Varga, Ed.
Internet-Draft                                                 J. Farkas
Intended status: Informational                                  Ericsson
Expires: June 16, 2021                                          A. Malis
                                                        Malis Consulting
                                                               S. Bryant
                                                  Futurewei Technologies
                                                       December 13, 2020


 DetNet Data Plane: IP over IEEE 802.1 Time Sensitive Networking (TSN)
                    draft-ietf-detnet-ip-over-tsn-05

Abstract

   This document specifies the Deterministic Networking IP data plane
   when operating over a TSN sub-network.  This document does not define
   new procedures or processes.  Whenever this document makes
   requirements statements or recommendations, these are taken from
   normative text in the referenced RFCs.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 16, 2021.

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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terms Used In This Document . . . . . . . . . . . . . . .   3
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   3
   3.  DetNet IP Data Plane Overview . . . . . . . . . . . . . . . .   3
   4.  DetNet IP Flows over an IEEE 802.1   TSN sub-network  . . . .   4
     4.1.  Functions for DetNet Flow to TSN Stream Mapping . . . . .   5
     4.2.  TSN requirements of IP DetNet nodes . . . . . . . . . . .   6
     4.3.  Service protection within the TSN sub-network . . . . . .   7
     4.4.  Aggregation during DetNet flow to TSN Stream mapping  . .   7
   5.  Management and Control Implications . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative references  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative references  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Deterministic Networking (DetNet) is a service that can be offered by
   a network to DetNet flows.  DetNet provides these flows 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].

   [RFC8939] specifies the DetNet data plane operation for IP hosts and
   routers that provide DetNet service to IP encapsulated data.  This
   document focuses on the scenario where DetNet IP nodes are
   interconnected by a TSN sub-network.

   The DetNet Architecture decomposes the DetNet related data plane
   functions into two sub-layers: a service sub-layer and a forwarding
   sub-layer.  The service sub-layer is used to provide DetNet service
   protection and reordering.  The forwarding sub-layer is used to
   provides congestion protection (low loss, assured latency, and
   limited reordering).  As described in [RFC8939] no DetNet specific
   headers are added to support DetNet IP flows, only the forwarding
   sub-layer functions are supported inside the DetNet domain.  Service




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   protection can be provided on a per sub-network basis as shown here
   for the IEEE802.1 TSN sub-network scenario.

2.  Terminology

2.1.  Terms Used In This Document

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

2.2.  Abbreviations

   The following abbreviations used in this document:

   DetNet        Deterministic Networking.

   DF            DetNet Flow.

   FRER          Frame Replication and Elimination for Redundancy (TSN
                 function).

   L2            Layer-2.

   L3            Layer-3.

   PREOF         Packet Replication, Ordering and Elimination Function.

   TSN           Time-Sensitive Networking, TSN is a Task Group of the
                 IEEE 802.1 Working Group.

3.  DetNet IP Data Plane Overview

   [RFC8939] describes how IP is used by DetNet nodes, i.e., hosts and
   routers, to identify DetNet flows and provide a DetNet service.  From
   a data plane perspective, an end-to-end IP model is followed.  DetNet
   uses "6-tuple" based flow identification, where "6-tuple" refers to
   information carried in IP and higher layer protocol headers.

   DetNet flow aggregation may be enabled via the use of wildcards,
   masks, 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 assurance on the
   aggregate through resource allocation and congestion control
   mechanisms.

   Congestion protection, latency control and the resource allocation
   (queuing, policing, shaping) are supported using the underlying link



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   / sub-net specific mechanisms.  Service protections (packet
   replication and packet elimination functions) are not provided at the
   IP DetNet layer end-to-end due the lack of a unified end-to-end
   sequencing information that would be available for intermediate
   nodes.  However, such service protection can be provided on a per
   underlying L2 link and sub-network basis.

   DetNet routers ensure that DetNet service requirements are met per
   hop by allocating local resources, both receive and transmit, and by
   mapping the service requirements of each flow to appropriate sub-
   network mechanisms.  Such mappings are sub-network technology
   specific.  DetNet nodes interconnected by a TSN sub-network are the
   primary focus of this document.  The mapping of DetNet IP flows to
   TSN streams and TSN protection mechanisms are covered in Section 4.

4.  DetNet IP Flows over an IEEE 802.1 TSN sub-network

   This section covers how DetNet IP flows operate over an IEEE 802.1
   TSN sub-network.  Figure 1 illustrates such a scenario, where two IP
   (DetNet) nodes are interconnected by a TSN sub-network.  Dotted lines
   around the Service components of the IP (DetNet) Nodes indicate that
   they are DetNet service aware but do not perform any DetNet service
   sub-layer function.  Node-1 is single homed and Node-2 is dual-homed
   to the TSN sub-network.

       IP (DetNet)                   IP (DetNet)
         Node-1                        Node-2

      ............                  ............
   <--: Service  :-- DetNet flow ---: Service  :-->
      +----------+                  +----------+
      |Forwarding|                  |Forwarding|
      +--------.-+    <-TSN Str->   +-.-----.--+
                \      ,-------.     /     /
                 +----[ TSN-Sub ]---+     /
                      [ Network ]--------+
                       `-------'
   <----------------- DetNet IP ----------------->

      Figure 1: DetNet (DN) Enabled IP Network over a TSN sub-network

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




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   DetNet networks.  All these functions have to identify flows that
   require TSN treatment.

   TSN capabilities of the TSN sub-network are made available for IP
   (DetNet) flows via the protocol interworking function desribed in
   Annex C.5 of IEEE 802.1CB [IEEE8021CB].  For example, applied on the
   TSN edge port it can convert an ingress unicast IP (DetNet) flow to
   use a specific Layer-2 multicast destination MAC address and a VLAN,
   in order to direct the packet through a specific path inside the
   bridged network.  A similar interworking function pair at the other
   end of the TSN sub-network would restore the packet to its original
   Layer-2 destination MAC address and VLAN.

   Placement of TSN functions depends on the TSN capabilities of nodes.
   IP (DetNet) Nodes may or may not support TSN functions.  For a given
   TSN Stream (i.e., a mapped DetNet flow) an IP (DetNet) node is
   treated as a Talker or a Listener inside the TSN sub-network.

4.1.  Functions for DetNet Flow to TSN Stream Mapping

   Mapping of a DetNet IP flow to a TSN Stream is provided via the
   combination of a passive and an active stream identification function
   that operate at the frame level (Layer-2).  The passive stream
   identification function is used to catch the 6-tuple of a DetNet IP
   flow and the active stream identification function is used to modify
   the Ethernet header according to the ID of the mapped TSN Stream.

   Clause 6.7 of IEEE 802.1CB [IEEE8021CB] defines an IP Stream
   identification function that can be used as a passive function for IP
   DetNet flows using UDP or TCP.  Clause 6.8 of IEEE P802.1CBdb
   [IEEEP8021CBdb] defines a Mask-and-Match Stream identification
   function that can be used as a passive function for any IP DetNet
   flows.

   Clause 6.6 of IEEE 802.1CB [IEEE8021CB] defines an Active Destination
   MAC and VLAN Stream identification function, what can replace some
   Ethernet header fields namely (1) the destination MAC-address, (2)
   the VLAN-ID and (3) priority parameters with alternate values.
   Replacement is provided for the frame passed down the stack from the
   upper layers or up the stack from the lower layers.

   Active Destination MAC and VLAN Stream identification can be used
   within a Talker to set flow identity or a Listener to recover the
   original addressing information.  It can be used also in a TSN bridge
   that is providing translation as a proxy service for an End System.






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4.2.  TSN requirements of IP DetNet nodes

   This section covers required behavior of a TSN-aware DetNet node
   using a TSN sub-network.  The implementation of TSN packet processing
   functions must be compliant with the relevant IEEE 802.1 standards.

   From the TSN sub-network perspective DetNet IP nodes are treated as
   Talker or Listener, that may be (1) TSN-unaware or (2) TSN-aware.

   In cases of TSN-unaware IP DetNet nodes the TSN relay nodes within
   the TSN sub-network must modify the Ethernet encapsulation of the
   DetNet IP flow (e.g., MAC translation, VLAN-ID setting, Sequence
   number addition, etc.) to allow proper TSN specific handling inside
   the sub-network.  There are no requirements defined for TSN-unaware
   IP DetNet nodes in this document.

   IP (DetNet) nodes being TSN-aware can be treated as a combination of
   a TSN-unaware Talker/Listener and a TSN-Relay, as shown in Figure 2.
   In such cases the IP (DetNet) node must provide the TSN sub-network
   specific Ethernet encapsulation over the link(s) towards the sub-
   network.

                  IP (DetNet)
                     Node
      <---------------------------------->

      ............
   <--: Service  :-- DetNet flow ------------------
      +----------+
      |Forwarding|
      +----------+    +---------------+
      |    L2    |    | L2 Relay with |<--- TSN ---
      |          |    | TSN function  |    Stream
      +-----.----+    +--.------.---.-+
             \__________/        \   \______
                                  \_________
       TSN-unaware
        Talker /          TSN-Bridge
        Listener             Relay
                                          <----- TSN Sub-network -----
      <------- TSN-aware Tlk/Lstn ------->

               Figure 2: IP (DetNet) node with TSN functions

   A TSN-aware IP (DetNet) node impementations must support the Stream
   Identification TSN component for recognizing flows.





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   A Stream identification component must be able to instantiate the
   following functions (1) Active Destination MAC and VLAN Stream
   identification function, (2) IP Stream identification function, (3)
   Mask-and-Match Stream identification function and (4) the related
   managed objects in Clause 9 of IEEE 802.1CB [IEEE8021CB] and IEEE
   P802.1CBdb [IEEEP8021CBdb].

   A TSN-aware IP (DetNet) node implementations must support the
   Sequencing function and the Sequence encode/decode function as
   defined in Clause 7.4 and 7.6 of IEEE 802.1CB [IEEE8021CB] if FRER is
   used inside the TSN sub-network.

   The Sequence encode/decode function must support the Redundancy tag
   (R-TAG) format as per Clause 7.8 of IEEE 802.1CB [IEEE8021CB].

   A TSN-aware IP (DetNet) node implementations must support the Stream
   splitting function and the Individual recovery function as defined in
   Clause 7.7 and 7.5 of IEEE 802.1CB [IEEE8021CB] when the node is a
   replication or elimination point for FRER.

4.3.  Service protection within the TSN sub-network

   TSN Streams supporting DetNet flows may use Frame Replication and
   Elimination for Redundancy (FRER) as defined in Clause 8. of IEEE
   802.1CB [IEEE8021CB] based on the loss service requirements of the
   TSN Stream, which is derived from the DetNet service requirements of
   the DetNet mapped flow.  The specific operation of FRER is not
   modified by the use of DetNet and follows IEEE 802.1CB [IEEE8021CB].

   FRER function and the provided service recovery is available only
   within the TSN sub-network as the TSN Stream-ID and the TSN sequence
   number are not valid outside the sub-network.  An IP (DetNet) node
   represents a L3 border and as such it terminates all related
   information elements encoded in the L2 frames.

4.4.  Aggregation during DetNet flow to TSN Stream mapping

   Implementations of this document shall use management and control
   information to map a DetNet flow to a TSN Stream.  N:1 mapping
   (aggregating DetNet flows in a single TSN Stream) shall be supported.
   The management or control function that provisions flow mapping shall
   ensure that adequate resources are allocated and configured to
   provide proper service requirements of the mapped flows.








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5.  Management and Control Implications

   DetNet flow and TSN Stream mapping related information are required
   only for TSN-aware IP (DetNet) nodes.  From the Data Plane
   perspective there is no practical difference based on the origin of
   flow mapping related information (management plane or control plane).

   The following summarizes the set of information that is needed to
   configure DetNet IP over TSN:

   o  DetNet IP related configuration information according to the
      DetNet role of the DetNet IP node, as per [RFC8939].

   o  TSN related configuration information according to the TSN role of
      the DetNet IP node, as per [IEEE8021Q], [IEEE8021CB] and
      [IEEEP8021CBdb].

   o  Mapping between DetNet IP flow(s) (as flow identification defined
      in [RFC8939], it is summarized in Section 5.1 of that document,
      and includes all wildcards, port ranges and the ability to ignore
      specific IP fields) and TSN Stream(s) (as stream identification
      information defined in [IEEE8021CB] and [IEEEP8021CBdb]).  Note,
      that managed objects for TSN Stream identification can be found in
      [IEEEP8021CBcv].

   This information must be provisioned per DetNet flow.

   Mappings between DetNet and TSN management and control planes are out
   of scope of the document.  Some of the challanges are highligthed
   below.

   TSN-aware IP DetNet nodes are member of both the DetNet domain and
   the TSN sub-network.  Within the TSN sub-network the TSN-aware IP
   (DetNet) node has a TSN-aware Talker/Listener role, so TSN specific
   management and control plane functionalities must be implemented.
   There are many similarities in the management plane techniques used
   in DetNet and TSN, but that is not the case for the control plane
   protocols.  For example, RSVP-TE and MSRP behaves differently.
   Therefore management and control plane design is an important aspect
   of scenarios, where mapping between DetNet and TSN is required.

   In order to use a TSN sub-network between DetNet nodes, DetNet
   specific information must be converted to TSN sub-network specific
   ones.  DetNet flow ID and flow related parameters/requirements must
   be converted to a TSN Stream ID and stream related parameters/
   requirements.  Note that, as the TSN sub-network is just a portion of
   the end-to-end DetNet path (i.e., single hop from IP perspective),
   some parameters (e.g., delay) may differ significantly.  Other



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   parameters (like bandwidth) also may have to be tuned due to the L2
   encapsulation used within the TSN sub-network.

   In some case it may be challenging to determine some TSN Stream
   related information.  For example, on a TSN-aware IP (DetNet) node
   that acts as a Talker, it is quite obvious which DetNet node is the
   Listener of the mapped TSN stream (i.e., the IP Next-Hop).  However
   it may be not trivial to locate the point/interface where that
   Listener is connected to the TSN sub-network.  Such attributes may
   require interaction between control and management plane functions
   and between DetNet and TSN domains.

   Mapping between DetNet flow identifiers and TSN Stream identifiers,
   if not provided explicitly, can be done by a TSN-aware IP (DetNet)
   node locally based on information provided for configuration of the
   TSN Stream identification functions (IP Stream identification, Mask-
   and-match Stream identification and active Stream identification
   function).

   Triggering the setup/modification of a TSN Stream in the TSN sub-
   network is an example where management and/or control plane
   interactions are required between the DetNet and TSN sub-network.
   TSN-unaware IP (DetNet) nodes make such a triggering even more
   complicated as they are fully unaware of the sub-network and run
   independently.

   Configuration of TSN specific functions (e.g., FRER) inside the TSN
   sub-network is a TSN domain specific decision and may not be visible
   in the DetNet domain.

6.  Security Considerations

   Security considerations for DetNet are described in detail in
   [I-D.ietf-detnet-security].  General security considerations are
   described in [RFC8655].  DetNet IP data plane specific considerations
   are summarized in [RFC8939].  This section considers exclusively
   security considerations which are specific to the DetNet IP over TSN
   sub-network scenario.

   The sub-network between DetNet nodes needs to be subject to
   appropriate confidentiality.  Additionally, knowledge of what DetNet/
   TSN services are provided by a sub-network may supply information
   that can be used in a variety of security attacks.  The ability to
   modify information exchanges between connected DetNet nodes may
   result in bogus operations.  Therefore, it is important that the
   interface between DetNet nodes and TSN sub-network are subject to
   authorization, authentication, and encryption.




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   The TSN sub-network operates at Layer-2 so various security
   mechanisms defined by IEEE can be used to secure the connection
   between the DetNet nodes (e.g., encryption may be provided using
   MACSec [IEEE802.1AE-2018]).

7.  IANA Considerations

   None.

8.  Acknowledgements

   The authors wish to thank Norman Finn, Lou Berger, Craig Gunther,
   Christophe Mangin and Jouni Korhonen for their various contributions
   to this work.

9.  References

9.1.  Normative references

   [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>.

9.2.  Informative references

   [I-D.ietf-detnet-security]
              Grossman, E., Mizrahi, T., and A. Hacker, "Deterministic
              Networking (DetNet) Security Considerations", draft-ietf-
              detnet-security-12 (work in progress), October 2020.

   [IEEE802.1AE-2018]
              IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC
              Security (MACsec)", 2018,
              <https://ieeexplore.ieee.org/document/8585421>.

   [IEEE8021CB]
              IEEE 802.1, "Standard for Local and metropolitan area
              networks - Frame Replication and Elimination for
              Reliability (IEEE Std 802.1CB-2017)", 2017,
              <http://standards.ieee.org/about/get/>.

   [IEEE8021Q]
              IEEE 802.1, "Standard for Local and metropolitan area
              networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
              2018)", 2018, <http://standards.ieee.org/about/get/>.





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   [IEEEP8021CBcv]
              Kehrer, S., "FRER YANG Data Model and Management
              Information Base Module", IEEE P802.1CBcv
              /D0.4 P802.1CBcv, August 2020,
              <https://www.ieee802.org/1/files/private/cv-drafts/d0/802-
              1CBcv-d0-4.pdf>.

   [IEEEP8021CBdb]
              Mangin, C., "Extended Stream identification functions",
              IEEE P802.1CBdb /D1.0 P802.1CBdb, September 2020,
              <http://www.ieee802.org/1/files/private/db-drafts/d1/802-
              1CBdb-d1-0.pdf>.

   [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>.

Authors' Addresses

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

   Email: balazs.a.varga@ericsson.com


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

   Email: janos.farkas@ericsson.com


   Andrew G. Malis
   Malis Consulting

   Email: agmalis@gmail.com


   Stewart Bryant
   Futurewei Technologies

   Email: stewart.bryant@gmail.com



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