TEAS Working Group                                               T. Saad
Internet-Draft                                                 V. Beeram
Intended status: Informational                          Juniper Networks
Expires: 5 November 2022                                         J. Dong
                                                     Huawei Technologies
                                                                  B. Wen
                                                                 Comcast
                                                           D. Ceccarelli
                                                              J. Halpern
                                                                Ericsson
                                                                 S. Peng
                                                                 R. Chen
                                                         ZTE Corporation
                                                                  X. Liu
                                                          Volta Networks
                                                            L. Contreras
                                                              Telefonica
                                                                R. Rokui
                                                                   Ciena
                                                                L. Jalil
                                                                 Verizon
                                                              4 May 2022


              Realizing Network Slices in IP/MPLS Networks
                    draft-bestbar-teas-ns-packet-10

Abstract

   Realizing network slices may require the Service Provider to have the
   ability to partition a physical network into multiple logical
   networks of varying sizes, structures, and functions so that each
   slice can be dedicated to specific services or customers.  Multiple
   network slices can be realized on the same network while ensuring
   slice elasticity in terms of network resource allocation.  This
   document describes a scalable solution to realize network slicing in
   IP/MPLS networks by supporting multiple services on top of a single
   physical network by relying on compliant domains and nodes to provide
   forwarding treatment (scheduling, drop policy, resource usage) on to
   packets that carry identifiers that indicate the slicing service that
   is to be applied to the packets.

Status of This Memo

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





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Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Acronyms and Abbreviations  . . . . . . . . . . . . . . .   6
   2.  Network Resource Slicing Membership . . . . . . . . . . . . .   7
   3.  IETF Network Slice Realization  . . . . . . . . . . . . . . .   8
     3.1.  Network Topology Filters  . . . . . . . . . . . . . . . .   9
     3.2.  IETF Network Slice Service Request  . . . . . . . . . . .   9
     3.3.  Slice-Flow Aggregation  . . . . . . . . . . . . . . . . .  10
     3.4.  Path Placement over NRP Filter Topology . . . . . . . . .  10
     3.5.  NRP Policy Installation . . . . . . . . . . . . . . . . .  10
     3.6.  Path Instantiation  . . . . . . . . . . . . . . . . . . .  10
     3.7.  Service Mapping . . . . . . . . . . . . . . . . . . . . .  11
   4.  Network Resource Partition Modes  . . . . . . . . . . . . . .  11
     4.1.  Data plane Network Resource Partition Mode  . . . . . . .  11
     4.2.  Control Plane Network Resource Partition Mode . . . . . .  12
     4.3.  Data and Control Plane Network Resource Partition Mode  .  14
   5.  Network Resource Partition Instantiation  . . . . . . . . . .  14
     5.1.  NRP Policy Definition . . . . . . . . . . . . . . . . . .  14
       5.1.1.  Network Resource Partition - Flow-Aggregate
               Selector  . . . . . . . . . . . . . . . . . . . . . .  15



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       5.1.2.  Network Resource Partition Resource Reservation . . .  18
       5.1.3.  Network Resource Partition Per Hop Behavior . . . . .  19
       5.1.4.  Network Resource Partition Topology . . . . . . . . .  20
     5.2.  Network Resource Partition Boundary . . . . . . . . . . .  20
       5.2.1.  Network Resource Partition Edge Nodes . . . . . . . .  20
       5.2.2.  Network Resource Partition Interior Nodes . . . . . .  21
       5.2.3.  Network Resource Partition Incapable Nodes  . . . . .  21
       5.2.4.  Combining Network Resource Partition Modes  . . . . .  22
   6.  Mapping Traffic on Slice-Flow Aggregates  . . . . . . . . . .  23
     6.1.  Network Slice-Flow Aggregate Relationships  . . . . . . .  23
   7.  Path Selection and Instantiation  . . . . . . . . . . . . . .  24
     7.1.  Applicability of Path Selection to Slice-Flow
           Aggregates  . . . . . . . . . . . . . . . . . . . . . . .  24
     7.2.  Applicability of Path Control Technologies to Slice-Flow
           Aggregates  . . . . . . . . . . . . . . . . . . . . . . .  24
       7.2.1.  RSVP-TE Based Slice-Flow Aggregate Paths  . . . . . .  25
       7.2.2.  SR Based Slice-Flow Aggregate Paths . . . . . . . . .  25
   8.  Network Resource Partition Protocol Extensions  . . . . . . .  25
   9.  Outstanding Issues  . . . . . . . . . . . . . . . . . . . . .  26
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  27
   12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  27
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  27
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  28
     14.2.  Informative References . . . . . . . . . . . . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   Network slicing allows a Service Provider to create independent and
   logical networks on top of a shared physical network infrastructure.
   Such network slices can be offered to customers or used internally by
   the Service Provider to enhance the delivery of their service
   offerings.  A Service Provider can also use network slicing to
   structure and organize the elements of its infrastructure.  The
   solution discussed in this document works with any path control
   technology (such as RSVP-TE, or SR) that can be used by a Service
   Provider to realize network slicing in IP/MPLS networks.

   [I-D.ietf-teas-ietf-network-slices] provides the definition of a
   network slice for use within the IETF and discusses the general
   framework for requesting and operating IETF Network Slices, their
   characteristics, and the necessary system components and interfaces.
   It also discusses the function of an IETF Network Slice Controller
   and the requirements on its northbound and southbound interfaces.





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   This document introduces the notion of a Slice-Flow Aggregate which
   comprises of one or more IETF network slice traffic streams.  It also
   describes the Network Resource Partition (NRP) and the NRP Policy
   that can be used to instantiate control and data plane behaviors on
   select topological elements associated with the NRP that supports a
   Slice-Flow Aggregate - refer Section 5.1 for further details.

   The IETF Network Slice Controller is responsible for the aggregation
   of multiple IETF network traffic streams into a Slice-Flow Aggregate,
   and for maintaining the mapping required between them.  The
   mechanisms used by the controller to determine the mapping of one or
   more IETF network slice to a Slice-Flow Aggregate are outside the
   scope of this document.  The focus of this document is on the
   mechanisms required at the device level to address the requirements
   of network slicing in packet networks.

   In a Diffserv (DS) domain [RFC2475], packets requiring the same
   forwarding treatment (scheduling and drop policy) are classified and
   marked with the respective Class Selector (CS) Codepoint (or the
   Traffic Class (TC) field for MPLS packets [RFC5462]) at the DS domain
   ingress nodes.  Such packets are said to belong to a Behavior
   Aggregate (BA) that has a common set of behavioral characteristics or
   a common set of delivery requirements.  At transit nodes, the CS is
   inspected to determine the specific forwarding treatment to be
   applied before the packet is forwarded.  A similar approach is
   adopted in this document to realize network slicing.  The solution
   proposed in this document does not mandate Diffserv to be enabled in
   the network to provide a specific forwarding treatment.

   When logical networks associated with an NRP are realized on top of a
   shared physical network infrastructure, it is important to steer
   traffic on the specific network resources partition that is allocated
   for a given Slice-Flow Aggregate.  In packet networks, the packets of
   a specific Slice-Flow Aggregate may be identified by one or more
   specific fields carried within the packet.  An NRP ingress boundary
   node (where Slice-Flow Aggregate traffic enters the NRP) populates
   the respective field(s) in packets that are mapped to a Slice-Flow
   Aggregate in order to allow interior NRP nodes to identify and apply
   the specific Per NRP Hop Behavior (NRP-PHB) associated with the
   Slice-Flow Aggregate.  The NRP-PHB defines the scheduling treatment
   and, in some cases, the packet drop probability.

   If Diffserv is enabled within the network, the Slice-Flow Aggregate
   traffic can further carry a Diffserv CS to enable differentiation of
   forwarding treatments for packets within a Slice-Flow Aggregate.






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   For example, when using MPLS as a dataplane, it is possible to
   identify packets belonging to the same Slice-Flow Aggregate by
   carrying an identifier in an MPLS Label Stack Entry (LSE).
   Additional Diffserv classification may be indicated in the Traffic
   Class (TC) bits of the global MPLS label to allow further
   differentiation of forwarding treatments for traffic traversing the
   same NRP.

   This document covers different modes of NRPs and discusses how each
   mode can ensure proper placement of Slice-Flow Aggregate paths and
   respective treatment of Slice-Flow Aggregate traffic.

1.1.  Terminology

   The reader is expected to be familiar with the terminology specified
   in [I-D.ietf-teas-ietf-network-slices].

   The following terminology is used in the document:

   IETF Network Slice:
      refer to the definition of 'IETF network slice' in
      [I-D.ietf-teas-ietf-network-slices].

   IETF Network Slice Controller (NSC):
      refer to the definition in [I-D.ietf-teas-ietf-network-slices].

   Network Resource Partition:
      refer to the definition in [I-D.ietf-teas-ietf-network-slices].

   Slice-Flow Aggregate:
      a collection of packets that match an NRP Policy and are given the
      same forwarding treatment; a Slice-Flow Aggregate comprises of one
      or more IETF network slice traffic streams; the mapping of one or
      more IETF network slices to a Slice-Flow Aggregate is maintained
      by the IETF Network Slice Controller.  The boundary nodes MAY also
      maintain a mapping of specific IETF network slice service(s) to a
      SFA.

   Network Resource Partition Policy (NRP):
      a policy construct that enables instantiation of mechanisms in
      support of IETF network slice specific control and data plane
      behaviors on select topological elements; the enforcement of an
      NRP Policy results in the creation of an NRP.

   NRP Identifier (NRP-ID):
      an identifier that is globally unique within an NRP domain and
      that can be used in the control or management plane to identify
      the resources associated with the NRP.



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   NRP Capable Node:
      a node that supports one of the NRP modes described in this
      document.

   NRP Incapable Node:
      a node that does not support any of the NRP modes described in
      this document.

   Slice-Flow Aggregate Path:
      a path that is setup over the NRP that is associated with a
      specific Slice-Flow Aggregate.

   Slice-Flow Aggregate Packet:
      a packet that traverses over the NRP that is associated with a
      specific Slice-Flow Aggregate.

   NRP Filter Topology:
      a set of topological elements associated with a Network Resource
      Partition.

   NRP state aware TE (NRP-TE):
      a mechanism for TE path selection that takes into account the
      available network resources associated with a specific NRP.

1.2.  Acronyms and Abbreviations

      BA: Behavior Aggregate

      CS: Class Selector

      NRP-PHB: NRP Per Hop Behavior as described in Section 5.1.3

      FAS: Flow Aggregate Selector

      FASL: Flow Aggregate Selector Label as described in Section 5.1.1

      SLA: Service Level Agreements

      SLO: Service Level Objectives

      SLE: Service Level Expectations

      Diffserv: Differentiated Services

      MPLS: Multiprotocol Label Switching

      LSP: Label Switched Path




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      RSVP: Resource Reservation Protocol

      TE: Traffic Engineering

      SR: Segment Routing

      VRF: VPN Routing and Forwarding

      AC: Attachment Circuit

      CE: Customer Edge

      PE: Provider Edge

      PCEP: Path Computation Element (PCE) Communication Protocol (PCEP)

2.  Network Resource Slicing Membership

   An NRP that supports a Slice-Flow Aggregate can be instantiated over
   parts of an IP/MPLS network (e.g., all or specific network resources
   in the access, aggregation, or core network), and can stretch across
   multiple domains administered by a provider.  The NRP topology may be
   comprised of dedicated and/or shared network resources (e.g., in
   terms of processing power, storage, and bandwidth).

   The physical network resources may be fully dedicated to a specific
   Slice-Flow Aggregate.  For example, traffic belonging to a Slice-Flow
   Aggregate can traverse dedicated network resources without being
   subjected to contention from traffic of other Slice-Flow Aggregates.
   Dedicated physical network resource slicing allows for simple
   partitioning of the physical network resources amongst Slice-Flow
   Aggregates without the need to distinguish packets traversing the
   dedicated network resources since only one Slice-Flow Aggregate
   traffic stream can traverse the dedicated resource at any time.

   To optimize network utilization, sharing of the physical network
   resources may be desirable.  In such case, the same physical network
   resource capacity is divided among multiple NRPs that support
   multiple Slice-Flow Aggregates.  The shared physical network
   resources can be partitioned in the data plane (for example by
   applying hardware policers and shapers) and/or partitioned in the
   control plane by providing a logical representation of the physical
   link that has a subset of the network resources available to it.








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3.  IETF Network Slice Realization

   Figure 1 describes the steps required to realize an IETF network
   slice service in a provider network using the solution proposed in
   this document.  While Figure 4 of [I-D.ietf-teas-ietf-network-slices]
   provides an abstract architecture of an IETF Network Slice, this
   section intends to offer a realization of that architecture specific
   for IP/MPLS packet networks.

   Each of the steps is further elaborated on in a subsequent section.

                           --      --      --
                          |CE|    |CE|    |CE|
                           --      --      --
                         AC :    AC :    AC :
                         ----------------------       -------
                        ( |PE|....|PE|....|PE| )     ( IETF  )
       IETF Network    (   --:     --     :--   )   ( Network )
       Slice Service   (     :............:     )   (  Slice  )
       Request          (  IETF Network Slice  )     (       )  Customer
         v               ----------------------       -------     View
         v        ............................\........./...............
         v                                     \       /        Provider
         v    >>>>>>>>>>>>>>>  Slice-Flow       \     /           View
         v   ^                 Aggregate Mapping v   v
         v   ^             -----------------------------------------
         v   ^            ( |PE|.......|PE|........|PE|.......|PE|  )
        ---------        (   --:        --         :--         --    )
       |         |       (     :...................:                 )
       |   NSC   |        (        Network Resource Partition       )
       |         |         -----------------------------------------
       |         |                             ^
       |         |>>>>>  Resource Partitioning |
        ---------          of Filter Topology  |
         v   v                                 |
         v   v            -----------------------------      --------
         v   v           (|PE|..-..|PE|... ..|PE|..|PE|)    (        )
         v   v          ( :--  |P|  --   :-:  --   :--  )  (  Filter  )
         v   v          ( :.-   -:.......|P|       :-   )  ( Topology )
         v   v          (  |P|...........:-:.......|P|  )   (        )
         v   v           (  -    Filter Topology       )     --------
         v   v            -----------------------------       ^
         v    >>>>>>>>>>>>  Topology Filter ^                /
         v        ...........................\............../...........
         v                                    \            /  Underlay
        ----------                             \          /  (Physical)
       |          |                             \        /    Network
       | Network  |    ----------------------------------------------



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       |Controller|   ( |PE|.....-.....|PE|......    |PE|.......|PE| )
       |          |  (   --     |P|     --      :-...:--     -..:--   )
        ----------  (    :       -:.............|P|.........|P|        )
            v       (    -......................:-:..-       -         )
             >>>>>>> (  |P|.........................|P|......:        )
         Program the  (  -                           -               )
           Network     ----------------------------------------------
                                (NRP Policies and Paths)*

    * : NRP Policy installation and path placement can be centralized
        or distributed.

            Figure 1: IETF network slice realization steps.

3.1.  Network Topology Filters

   The Physical Network may be filtered into a number of Filter
   Topologies.  Filter actions may include selection of specific nodes
   and links according to their capabilities and are based on network-
   wide policies.  The resulting topologies can be used to host IETF
   Network Slices and provide a useful way for the network operator to
   know that all of the resources they are using to plan a network slice
   meet specific SLOs.  This step can be done offline during planning
   activity, or could be performed dynamically as new demands arise.

   Section 5.1.4 describes how topology filters can be associated with
   the NRP instantiated by the NRP Policy.

3.2.  IETF Network Slice Service Request

   The customer requests an IETF Network Slice Service specifying the
   CE-AC-PE points of attachment, the connectivity matrix, and the SLOs/
   SLEs as described in [I-D.ietf-teas-ietf-network-slices].  These
   capabilities are always provided based on a Service Level Agreement
   (SLA) between the network slice costumer and the provider.

   This defines the traffic flows that need to be supported when the
   slice is realized.  Depending on the mechanism and encoding of the
   Attachment Circuit (AC), the IETF Network Slice Service may also
   include information that will allow the operator's controllers to
   configure the PEs to determine what customer traffic is intended for
   this IETF Network Slice.

   IETF Network Slice Service Requests are likely to arrive at various
   times in the life of the network, and may also be modified.






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3.3.  Slice-Flow Aggregation

   A network may be called upon to support very many IETF Network
   Slices, and this could present scaling challenges in the operation of
   the network.  In order to overcome this, the IETF Network Slice
   streams may be aggregated into groups according to similar
   characteristics.

   A Slice-Flow Aggregate is a construct that comprises the traffic
   flows of one or more IETF Network Slices.  The mapping of IETF
   Network Slices into an Slice-Flow Aggregate is a matter of local
   operator policy is a function executed by the Controller.  The Slice-
   Flow Aggregate may be preconfigured, created on demand, or modified
   dynamically.

3.4.  Path Placement over NRP Filter Topology

   Depending on the underlying network technology, the paths are
   selected in the network in order to best deliver the SLOs for the
   different services carried by the Slice-Flow Aggregate.  The path
   placement function (carried on ingress node or by a controller) is
   performed on the Filter Topology that is selected to support the
   Slice-Flow Aggregate.

   Note that this step may indicate the need to increase the capacity of
   the underlying Filter Topology or to create a new Filter Topology.

3.5.  NRP Policy Installation

   A Controller function programs the physical network with policies for
   handling the traffic flows belonging to the Slice-Flow Aggregate.
   These policies instruct underlying routers how to handle traffic for
   a specific Slice-Flow Aggregate: the routers correlate markers
   present in the packets that belong to the Slice-Flow Aggregate.  The
   way in which the NRP Policy is installed in the routers and the way
   that the traffic is marked is implementation specific.  The NRP
   Policy instantiation in the network is further described in
   Section 5.

3.6.  Path Instantiation

   Depending on the underlying network technology, a Controller function
   may install the forwarding state specific to the Slice-Flow Aggregate
   so that traffic is routed along paths derived in the Path Placement
   step described in Section 3.4.  The way in which the paths are
   instantiated is implementation specific.





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3.7.  Service Mapping

   The edge points can be configured to support the network slice
   service by mapping the customer traffic to Slice-Flow Aggregates,
   possibly using information supplied when the IETF network slice
   service was requested.  The edge points may also be instructed to
   mark the packets so that the network routers will know which policies
   and routing instructions to apply.  The steering of traffic onto
   Slice-Flow Aggregate paths is further described in Section 6.

4.  Network Resource Partition Modes

   An NRP Policy can be used to dictate if the network resource
   partitioning of the shared network resources among multiple Slice-
   Flow Aggregates can be achieved:

   a)  in data plane only,

   b)  in control plane only, or

   c)  in both control and data planes.

4.1.  Data plane Network Resource Partition Mode

   The physical network resources can be partitioned on network devices
   by applying a Per Hop forwarding Behavior (PHB) onto packets that
   traverse the network devices.  In the Diffserv model, a Class
   Selector (CS) codepoint is carried in the packet and is used by
   transit nodes to apply the PHB that determines the scheduling
   treatment and drop probability for packets.

   When data plane NRP mode is applied, packets need to be forwarded on
   the specific NRP that supports the Slice-Flow Aggregate to ensure the
   proper forwarding treatment dictated in the NRP Policy is applied
   (refer to Section 5.1 below).  In this case, a Flow Aggregate
   Selector (FAS) must be carried in each packet to identify the Slice-
   Flow Aggregate that it belongs to.

   The ingress node of an NRP domain adds a FAS field if one is not
   already present in each Slice-Flow Aggregate packet.  In the data
   plane NRP mode, the transit nodes within an NRP domain use the FAS to
   associate packets with a Slice-Flow Aggregate and to determine the
   Network Resource Partition Per Hop Behavior (NRP-PHB) that is applied
   to the packet (refer to Section 5.1.3 for further details).  The CS
   is used to apply a Diffserv PHB on to the packet to allow
   differentiation of traffic treatment within the same Slice-Flow
   Aggregate.




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   When data plane only NRP mode is used, routers may rely on a network
   state independent view of the topology to determine the best paths.
   In this case, the best path selection dictates the forwarding path of
   packets to the destination.  The FAS field carried in each packet
   determines the specific NRP-PHB treatment along the selected path.

4.2.  Control Plane Network Resource Partition Mode

   Multiple NRPs can be realized over the same set of physical
   resources.  Each NRP is identified by an identifier (NRP-ID) that is
   globally unique within the NRP domain.  The NRP state reservations
   for each NRP can be maintained on the network element or on a
   controller.

   The network reservation states for a specific partition can be
   represented in a topology that contains all or a subset of the
   physical network elements (nodes and links) and reflect the network
   state reservations in that NRP.  The logical network resources that
   appear in the NRP topology can reflect a part, whole, or in-excess of
   the physical network resource capacity (e.g., when oversubscription
   is desirable).

   For example, the physical link bandwidth can be divided into
   fractions, each dedicated to an NRP that supports a Slice-Flow
   Aggregate.  The topology associated with the NRP supporting a Slice-
   Flow Aggregate can be used by routing protocols, or by the ingress/
   PCE when computing NRP state aware TE paths.

   To perform NRP state aware Traffic Engineering (NRP-TE), the resource
   reservation on each link needs to be NRP aware.  The NRP reservations
   state can be managed locally on the device or off device (e.g. on a
   controller).

   The same physical link may be member of multiple slice policies that
   instantiate different NRPs.  The NRP reservable or utilized bandwidth
   on such a link is updated (and may be advertised) whenever new paths
   are placed in the network.  The NRP reservation state, in this case,
   is maintained on each device or off the device on a resource
   reservation manager that holds reservation states for those links in
   the network.

   Multiple NRPs that support Slice-Flow Aggregates can form a group and
   share the available network resources allocated to each.  In this
   case, a node can update the reservable bandwidth for each NRP to take
   into consideration the available bandwidth from other NRPs in the
   same group.





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   For illustration purposes, Figure 2 describes bandwidth partitioning
   or sharing amongst a group of NRPs.  In Figure 2a, the NRPs
   identified by the following NRP-IDs: NRP1, NRP2, NRP3 and NRP4 are
   not sharing any bandwidths between each other.  In Figure 2b, the
   NRPs: NRP1 and NRP2 can share the available bandwidth portion
   allocated to each amongst them.  Similarly, NRP3 and NRP4 can share
   amongst themselves any available bandwidth allocated to them, but
   they cannot share available bandwidth allocated to NRP1 or NRP2.  In
   both cases, the Max Reservable Bandwidth may exceed the actual
   physical link resource capacity to allow for over subscription.

   I-----------------------------I       I-----------------------------I
   <--NRP1->                     I       I-----------------I           I
   I---------I                   I       I <-NRP1->        I           I
   I         I                   I       I I-------I       I           I
   I---------I                   I       I I       I       I           I
   I                             I       I I-------I       I           I
   <-----NRP2------>             I       I                 I           I
   I-----------------I           I       I <-NRP2->        I           I
   I                 I           I       I I---------I     I           I
   I-----------------I           I       I I         I     I           I
   I                             I       I I---------I     I           I
   <---NRP3---->                 I       I                 I           I
   I-------------I               I       I NRP1 + NRP2     I           I
   I             I               I       I-----------------I           I
   I-------------I               I       I                             I
   I                             I       I                             I
   <---NRP4---->                 I       I-----------------I           I
   I-------------I               I       I <-NRP3->        I           I
   I             I               I       I I-------I       I           I
   I-------------I               I       I I       I       I           I
   I                             I       I I-------I       I           I
   I NRP1+NRP2+NRP3+NRP4         I       I                 I           I
   I                             I       I <-NRP4->        I           I
   I-----------------------------I       I I---------I     I           I
   <--Max Reservable Bandwidth-->        I I         I     I           I
                                         I I---------I     I           I
                                         I                 I           I
                                         I NRP3 + NRP4     I           I
                                         I-----------------I           I
                                         I NRP1+NRP2+NRP3+NRP4         I
                                         I                             I
                                         I-----------------------------I
                                         <--Max Reservable Bandwidth-->

   (a) No bandwidth sharing              (b) Sharing bandwidth between
       between NRPs.                         NRPs of the same group.




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          Figure 2: Bandwidth isolation/sharing among NRPs.

4.3.  Data and Control Plane Network Resource Partition Mode

   In order to support strict guarantees for Slice-Flow Aggregates, the
   network resources can be partitioned in both the control plane and
   data plane.

   The control plane partitioning allows the creation of customized
   topologies per NRP that each supports a Slice-Flow Aggregate.  The
   ingress routers or a Path Computation Engine (PCE) may use the
   customized topologies and the NRP state to determine optimal path
   placement for specific demand flows using NRP-TE.

   The data plane partitioning provides isolation for Slice-Flow
   Aggregate traffic, and protection when resource contention occurs due
   to bursts of traffic from other Slice-Flow Aggregate traffic that
   traverses the same shared network resource.

5.  Network Resource Partition Instantiation

   A network slice can span multiple technologies and multiple
   administrative domains.  Depending on the network slice customer
   requirements, a network slice can be differentiated from other
   network slices in terms of data, control, and management planes.

   The customer of a network slice service expresses their intent by
   specifying requirements rather than mechanisms to realize the slice
   as described in Section 3.2.

   The network slice controller is fed with the network slice service
   intent and realizes it with an appropriate Network Resource Partition
   Policy (NRP Policy).  Multiple IETF network slices are mapped to the
   same Slice-Flow Aggregate as described in Section 3.3.

   The network wide consistent NRP Policy definition is distributed to
   the devices in the network as shown in Figure 1.  The specification
   of the network slice intent on the northbound interface of the
   controller and the mechanism used to map the network slice to a
   Slice-Flow Aggregate are outside the scope of this document and will
   be addressed in separate documents.

5.1.  NRP Policy Definition

   The NRP Policy is network-wide construct that is supplied to network
   devices, and may include rules that control the following:





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   *  Data plane specific policies: This includes the FAS, any firewall
      rules or flow-spec filters, and QoS profiles associated with the
      NRP Policy and any classes within it.

   *  Control plane specific policies: This includes bandwidth
      reservations, any network resource sharing amongst slice policies,
      and reservation preference to prioritize reservations of a
      specific NRP over others.

   *  Topology membership policies: This defines the topology filter
      policies that dictate node/link/function membership to a specific
      NRP.

   There is a desire for flexibility in realizing network slices to
   support the services across networks consisting of implementations
   from multiple vendors.  These networks may also be grouped into
   disparate domains and deploy various path control technologies and
   tunnel techniques to carry traffic across the network.  It is
   expected that a standardized data model for NRP Policy will
   facilitate the instantiation and management of the NRP on the
   topological elements selected by the NRP Policy topology filter.

   It is also possible to distribute the NRP Policy to network devices
   using several mechanisms, including protocols such as NETCONF or
   RESTCONF, or exchanging it using a suitable routing protocol that
   network devices participate in (such as IGP(s) or BGP).  The
   extensions to enable specific protocols to carry an NRP Policy
   definition will be described in separate documents.

5.1.1.  Network Resource Partition - Flow-Aggregate Selector

   A router should be able to identify a packet belonging to a Slice-
   Flow Aggregate before it can apply the associated dataplane
   forwarding treatment or NRP-PHB.  One or more fields within the
   packet are used as an FAS to do this.

   Forwarding Address Based FAS:

      It is possible to assign a different forwarding address (or MPLS
      forwarding label in case of MPLS network) for each Slice-Flow
      Aggregate on a specific node in the network.  [RFC3031] states in
      Section 2.1 that: 'Some routers analyze a packet's network layer
      header not merely to choose the packet's next hop, but also to
      determine a packet's "precedence" or "class of service"'.
      Assigning a unique forwarding address (or MPLS forwarding label)
      to each Slice-Flow Aggregate allows Slice-Flow Aggregate packets
      destined to a node to be distinguished by the destination address
      (or MPLS forwarding label) that is carried in the packet.



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      This approach requires maintaining per Slice-Flow Aggregate state
      for each destination in the network in both the control and data
      plane and on each router in the network.  For example, consider a
      network slicing provider with a network composed of 'N' nodes,
      each with 'K' adjacencies to its neighbors.  Assuming a node can
      be reached over 'M' different Slice-Flow Aggregates, the node
      assigns and advertises reachability to 'N' unique forwarding
      addresses, or MPLS forwarding labels.  Similarly, each node
      assigns a unique forwarding address (or MPLS forwarding label) for
      each of its 'K' adjacencies to enable strict steering over the
      adjacency for each slice.  The total number of control and data
      plane states that need to be stored and programmed in a router's
      forwarding is (N+K)*M states.  Hence, as 'N', 'K', and 'M'
      parameters increase, this approach suffers from scalability
      challenges in both the control and data planes.

   Global Identifier Based FAS:

      An NRP Policy may include a Global Identifier FAS (G-FAS) field
      that is carried in each packet in order to associate it to the NRP
      supporting a Slice-Flow Aggregate, independent of the forwarding
      address or MPLS forwarding label that is bound to the destination.
      Routers within the NRP domain can use the forwarding address (or
      MPLS forwarding label) to determine the forwarding next-hop(s),
      and use the G-FAS field in the packet to infer the specific
      forwarding treatment that needs to be applied on the packet.

      The G-FAS can be carried in one of multiple fields within the
      packet, depending on the dataplane used.  For example, in MPLS
      networks, the G-FAS can be encoded within an MPLS label that is
      carried in the packet's MPLS label stack.  All packets that belong
      to the same Slice-Flow Aggregate may carry the same G-FAS in the
      MPLS label stack.  It is also possible to have multiple G-FAS's
      map to the same Slice-Flow Aggregate.

      The G-FAS can be encoded in an MPLS label and may appear in
      several positions in the MPLS label stack.  For example, the VPN
      service label may act as a G-FAS to allow VPN packets to be mapped
      to the Slice-Flow Aggregate.  In this case, a single VPN service
      label acting as a G-FAS may be allocated by all Egress PEs of a
      VPN.  Alternatively, multiple VPN service labels may act as
      G-FAS's that map a single VPN to the same Slice-Flow Aggregate to
      allow for multiple Egress PEs to allocate different VPN service
      labels for a VPN.  In other cases, a range of VPN service labels
      acting as multiple G-FAS's may map multiple VPN traffic to a
      single Slice-Flow Aggregate.  An example of such deployment is
      shown in Figure 3.




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     SR Adj-SID:          G-FAS (VPN service label) on PE2: 1001
        9012: P1-P2
        9023: P2-PE2

            /-----\        /-----\        /-----\       /-----\
            | PE1 | -----  | P1  | ------ | P2  |------ | PE2 |
            \-----/        \-----/        \-----/       \-----/

   In
   packet:
   +------+       +------+         +------+        +------+
   | IP   |       | 9012 |         | 9023 |        | 1001 |
   +------+       +------+         +------+        +------+
   | Pay- |       | 9023 |         | 1001 |        | IP   |
   | Load |       +------+         +------+        +------+
   +----- +       | 1001 |         | IP   |        | Pay- |
                  +------+         +------+        | Load |
                  | IP   |         | Pay- |        +------+
                  +------+         | Load |
                  | Pay- |         +------+
                  | Load |
                  +------+

           Figure 3: G-FAS or VPN label at bottom of label stack.

      In some cases, the position of the G-FAS may not be at a fixed
      position in the MPLS label header.  In this case, the G-FAS label
      can show up in any position in the MPLS label stack.  To enable a
      transit router to identify the position of the G-FAS label, a
      special purpose label can be used to indicate the presence of a
      G-FAS in the MPLS label stack as shown in Figure 4.




















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        SR Adj-SID:          G-FAS: 1001
           9012: P1-P2
           9023: P2-PE2

               /-----\        /-----\        /-----\       /-----\
               | PE1 | -----  | P1  | ------ | P2  |------ | PE2 |
               \-----/        \-----/        \-----/       \-----/

      In
      packet:
      +------+       +------+         +------+        +------+
      | IP   |       | 9012 |         | 9023 |        | FAI  |
      +------+       +------+         +------+        +------+
      | Pay- |       | 9023 |         | FAI  |        | 1001 |
      | Load |       +------+         +------+        +------+
      +------+       | FAI  |         | 1001 |        | IP   |
                     +------+         +------+        +------+
                     | 1001 |         | IP   |        | Pay- |
                     +------+         +------+        | Load |
                     | IP   |         | Pay- |        +------+
                     +------+         | Load |
                     | Pay- |         +------+
                     | Load |
                     +------+

             Figure 4: FAI and G-FAS label in the label stack.

      When the slice is realized over an IP dataplane, the G-FAS can be
      encoded in the IP header (e.g. as an IPv6 option header).

5.1.2.  Network Resource Partition Resource Reservation

   Bandwidth and network resource allocation strategies for slice
   policies are essential to achieve optimal placement of paths within
   the network while still meeting the target SLOs.

   Resource reservation allows for the management of available bandwidth
   and the prioritization of existing allocations to enable preference-
   based preemption when contention on a specific network resource
   arises.  Sharing of a network resource's available bandwidth amongst
   a group of NRPs may also be desirable.  For example, a Slice-Flow
   Aggregate may not be using all of the NRP reservable bandwidth; this
   allows other NRPs in the same group to use the available bandwidth
   resources for other Slice-Flow Aggregates.







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   Congestion on shared network resources may result from sub-optimal
   placement of paths in different slice policies.  When this occurs,
   preemption of some Slice-Flow Aggregate paths may be desirable to
   alleviate congestion.  A preference-based allocation scheme enables
   prioritization of Slice-Flow Aggregate paths that can be preempted.

   Since network characteristics and its state can change over time, the
   NRP topology and its network state need to be propagated in the
   network to enable ingress TE routers or Path Computation Engine
   (PCEs) to perform accurate path placement based on the current state
   of the NRP network resources.

5.1.3.  Network Resource Partition Per Hop Behavior

   In Diffserv terminology, the forwarding behavior that is assigned to
   a specific class is called a Per Hop Behavior (PHB).  The PHB defines
   the forwarding precedence that a marked packet with a specific CS
   receives in relation to other traffic on the Diffserv-aware network.

   The NRP Per Hop Behavior (NRP-PHB) is the externally observable
   forwarding behavior applied to a specific packet belonging to a
   Slice-Flow Aggregate.  The goal of an NRP-PHB is to provide a
   specified amount of network resources for traffic belonging to a
   specific Slice-Flow Aggregate.  A single NRP may also support
   multiple forwarding treatments or services that can be carried over
   the same logical network.

   The Slice-Flow Aggregate traffic may be identified at NRP ingress
   boundary nodes by carrying a FAS to allow routers to apply a specific
   forwarding treatment that guarantee the SLA(s).

   With Differentiated Services (Diffserv) it is possible to carry
   multiple services over a single converged network.  Packets requiring
   the same forwarding treatment are marked with a CS at domain ingress
   nodes.  Up to eight classes or Behavior Aggregates (BAs) may be
   supported for a given Forwarding Equivalence Class (FEC) [RFC2475].
   To support multiple forwarding treatments over the same Slice-Flow
   Aggregate, a Slice-Flow Aggregate packet may also carry a Diffserv CS
   to identify the specific Diffserv forwarding treatment to be applied
   on the traffic belonging to the same NRP.

   At transit nodes, the CS field carried inside the packets are used to
   determine the specific PHB that determines the forwarding and
   scheduling treatment before packets are forwarded, and in some cases,
   drop probability for each packet.






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5.1.4.  Network Resource Partition Topology

   A key element of the NRP Policy is a customized topology that may
   include the full or subset of the physical network topology.  The NRP
   topology could also span multiple administrative domains and/or
   multiple dataplane technologies.

   An NRP topology can overlap or share a subset of links with another
   NRP topology.  A number of topology filtering policies can be defined
   as part of the NRP Policy to limit the specific topology elements
   that belong to the NRP.  For example, a topology filtering policy can
   leverage Resource Affinities as defined in [RFC2702] to include or
   exclude certain links that the NRP is instantiated on in supports of
   the Slice-Flow Aggregate.

   The NRP Policy may also include a reference to a predefined topology
   (e.g., derived from a Flexible Algorithm Definition (FAD) as defined
   in [I-D.ietf-lsr-flex-algo], or Multi-Topology ID as defined
   [RFC4915].

5.2.  Network Resource Partition Boundary

   A network slice originates at the edge nodes of a network slice
   provider.  Traffic that is steered over the corresponding NRP
   supporting a Slice-Flow Aggregate may traverse NRP capable as well as
   NRP incapable interior nodes.

   The network slice may encompass one or more domains administered by a
   provider.  For example, an organization's intranet or an ISP.  The
   network provider is responsible for ensuring that adequate network
   resources are provisioned and/or reserved to support the SLAs offered
   by the network end-to-end.

5.2.1.  Network Resource Partition Edge Nodes

   NRP edge nodes sit at the boundary of a network slice provider
   network and receive traffic that requires steering over network
   resources specific to a NRP that supports a Slice-Flow Aggregate.
   These edge nodes are responsible for identifying Slice-Flow Aggregate
   specific traffic flows by possibly inspecting multiple fields from
   inbound packets (e.g., implementations may inspect IP traffic's
   network 5-tuple in the IP and transport protocol headers) to decide
   on which NRP it can be steered.








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   Network slice ingress nodes may condition the inbound traffic at
   network boundaries in accordance with the requirements or rules of
   each service's SLAs.  The requirements and rules for network slice
   services are set using mechanisms which are outside the scope of this
   document.

   When data plane NRP mode is employed, the NRP ingress nodes are
   responsible for adding a suitable FAS onto packets that belong to
   specific Slice-Flow Aggregate.  In addition, edge nodes may mark the
   corresponding Diffserv CS to differentiate between different types of
   traffic carried over the same Slice-Flow Aggregate.

5.2.2.  Network Resource Partition Interior Nodes

   An NRP interior node receives slice traffic and may be able to
   identify the packets belonging to a specific Slice-Flow Aggregate by
   inspecting the FAS field carried inside each packet, or by inspecting
   other fields within the packet that may identify the traffic streams
   that belong to a specific Slice-Flow Aggregate.  For example, when
   data plane NRP mode is applied, interior nodes can use the FAS
   carried within the packet to apply the corresponding NRP-PHB
   forwarding behavior.  Nodes within the network slice provider network
   may also inspect the Diffserv CS within each packet to apply a per
   Diffserv class PHB within the NRP Policy, and allow differentiation
   of forwarding treatments for packets forwarded over the same NRP that
   supports the Slice-Flow Aggregate.

5.2.3.  Network Resource Partition Incapable Nodes

   Packets that belong to a Slice-Flow Aggregate may need to traverse
   nodes that are NRP incapable.  In this case, several options are
   possible to allow the slice traffic to continue to be forwarded over
   such devices and be able to resume the NRP forwarding treatment once
   the traffic reaches devices that are NRP-capable.

   When data plane NRP mode is employed, packets carry a FAS to allow
   slice interior nodes to identify them.  To support end-to-end network
   slicing, the FAS is maintained in the packets as they traverse
   devices within the network - including NRP capable and incapable
   devices.

   For example, when the FAS is an MPLS label at the bottom of the MPLS
   label stack, packets can traverse over devices that are NRP incapable
   without any further considerations.  On the other hand when the FASL
   is at the top of the MPLS label stack, packets can be bypassed (or
   tunneled) over the NRP incapable devices towards the next device that
   supports NRP as shown in Figure 5.




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     SR Node-SID:           FASL: 1001    @@@: NRP Policy enforced
        1601: P1                          ...: NRP Policy not enforced
        1602: P2
        1603: P3
        1604: P4
        1605: P5

               @@@@@@@@@@@@@@ ........................
                                                     .
              /-----\        /-----\        /-----\  .
              | P1  | -----  | P2  | ----- | P3  |   .
              \-----/        \-----/        \-----/  .
                                               |     @@@@@@@@@@
                                               |
                                            /-----\        /-----\
                                            | P4  | ------ | P5  |
                                            \-----/        \-----/


               +------+       +------+        +------+
               | 1001 |       | 1604 |        | 1001 |
               +------+       +------+        +------+
               | 1605 |       | 1001 |        | IP   |
               +------+       +------+        +------+
               | IP   |       | 1605 |        | Pay- |
               +------+       +------+        | Load |
               | Pay- |       | IP   |        +------+
               | Load |       +------+
               +----- +       | Pay- |
                              | Load |
                              +------+

      Figure 5: Extending network slice over NRP incapable device(s).

5.2.4.  Combining Network Resource Partition Modes

   It is possible to employ a combination of the NRP modes that were
   discussed in Section 4 to realize a network slice.  For example, data
   and control plane NRP modes can be employed in parts of a network,
   while control plane NRP mode can be employed in the other parts of
   the network.  The path selection, in such case, can take into account
   the NRP available network resources.  The FAS carried within packets
   allow transit nodes to enforce the corresponding NRP-PHB on the parts
   of the network that apply the data plane NRP mode.  The FAS can be
   maintained while traffic traverses nodes that do not enforce data
   plane NRP mode, and so slice PHB enforcement can resume once traffic
   traverses capable nodes.




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6.  Mapping Traffic on Slice-Flow Aggregates

   The usual techniques to steer traffic onto paths can be applicable
   when steering traffic over paths established for a specific Slice-
   Flow Aggregate.

   For example, one or more (layer-2 or layer-3) VPN services can be
   directly mapped to paths established for a Slice-Flow Aggregate.  In
   this case, the per Virtual Routing and Forwarding (VRF) instance
   traffic that arrives on the Provider Edge (PE) router over external
   interfaces can be directly mapped to a specific Slice-Flow Aggregate
   path.  External interfaces can be further partitioned (e.g., using
   VLANs) to allow mapping one or more VLANs to specific Slice-Flow
   Aggregate paths.

   Another option is steer traffic to specific destinations directly
   over multiple slice policies.  This allows traffic arriving on any
   external interface and targeted to such destinations to be directly
   steered over the slice paths.

   A third option that can also be used is to utilize a data plane
   firewall filter or classifier to enable matching of several fields in
   the incoming packets to decide whether the packet belongs to a
   specific Slice-Flow Aggregate.  This option allows for applying a
   rich set of rules to identify specific packets to be mapped to a
   Slice-Flow Aggregate.  However, it requires data plane network
   resources to be able to perform the additional checks in hardware.

6.1.  Network Slice-Flow Aggregate Relationships

   The following describes the generalization relationships between the
   IETF network slice and different parts of the solution as described
   in Figure 1.

   o A customer may request one or more IETF Network Slices.

   o Any given Attachment Circuit (AC) may support the traffic for one
   or more IETF Network Slices.  If there is more than one IETF Network
   Slice using a single AC, the IETF Network Slice Service request must
   include enough information to allow the edge nodes to demultiplex the
   traffic for the different IETF Network Slices.

   o By definition, multiple IETF Network Slices may be mapped to a
   single Slice-Flow Aggregate.  However, it is possible for an Slice-
   Flow Aggregate to contain just a single IETF Network Slice.






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   o The physical network may be filtered to multiple Filter Topologies.
   Each such Filter Topology facilitates planning the placement of paths
   for the Slice-Flow Aggregate by presenting only the subset of links
   and nodes that meet specific criteria.  Note, however, in absence of
   any Filter Topology, Slice-Flow Aggregate are free to operate over
   the full physical network.

   o It is anticipated that there may be very many IETF Network Slices
   supported by a network operator over a single physical network.  A
   network may support a limited number of Slice-Flow Aggregates, with
   each of the Slice-Flow Aggregates grouping any number of the IETF
   Network Slices streams.

7.  Path Selection and Instantiation

7.1.  Applicability of Path Selection to Slice-Flow Aggregates

   In State-dependent TE [I-D.ietf-teas-rfc3272bis], the path selection
   adapts based on the current state of the network.  The state of the
   network can be based on parameters flooded by the routers as
   described in [RFC2702].  The link state is advertised with current
   reservations, thereby reflecting the available bandwidth on each
   link.  Such link reservations may be maintained centrally on a
   network wide network resource manager, or distributed on devices (as
   usually done with RSVP-TE).  TE extensions exist today to allow IGPs
   (e.g., [RFC3630] and [RFC5305]), and BGP-LS [RFC7752] to advertise
   such link state reservations.

   When the network resource reservations are maintained for NRPs, the
   link state can carry per NRP state (e.g., reservable bandwidth).
   This allows path computation to take into account the specific
   network resources available for an NRP.  In this case, we refer to
   the process of path placement and path provisioning as NRP aware TE
   (NRP-TE).

7.2.  Applicability of Path Control Technologies to Slice-Flow
      Aggregates

   The NRP modes described in this document are agnostic to the
   technology used to setup paths that carry Slice-Flow Aggregate
   traffic.  One or more paths connecting the endpoints of the mapped
   IETF network slices may be selected to steer the corresponding
   traffic streams over the resources allocated for the NRP that
   supports a Slice-Flow Aggregate.

   The feasible paths can be computed using the NRP topology and network
   state subject the optimization metrics and constraints.




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7.2.1.  RSVP-TE Based Slice-Flow Aggregate Paths

   RSVP-TE [RFC3209] can be used to signal LSPs over the computed
   feasible paths in order to carry the Slice-Flow Aggregate traffic.
   The specific extensions to the RSVP-TE protocol required to enable
   signaling of NRP aware RSVP-TE LSPs are outside the scope of this
   document.

7.2.2.  SR Based Slice-Flow Aggregate Paths

   Segment Routing (SR) [RFC8402] can be used to setup and steer traffic
   over the computed Slice-Flow Aggregate feasible paths.

   The SR architecture defines a number of building blocks that can be
   leveraged to support the realization of NRPs that support Slice-Flow
   Aggregates in an SR network.

   Such building blocks include:

   *  SR Policy with or without Flexible Algorithm.

   *  Steering of services (e.g.  VPN) traffic over SR paths

   *  SR Operation, Administration and Management (OAM) and Performance
      Management (PM)

   SR allows a headend node to steer packets onto specific SR paths
   using a Segment Routing Policy (SR Policy).  The SR policy supports
   various optimization objectives and constraints and can be used to
   steer Slice-Flow Aggregate traffic in the SR network.

   The SR policy can be instantiated with or without the IGP Flexible
   Algorithm (Flex-Algorithm) feature.  It may be possible to dedicate a
   single SR Flex-Algorithm to compute and instantiate SR paths for one
   Slice-Flow Aggregate traffic.  In this case, the SR Flex-Algorithm
   computed paths and Flex-Algorithm SR SIDs are not shared by other
   Slice-Flow Aggregates traffic.  However, to allow for better scale,
   it may be desirable for multiple Slice-Flow Aggregates traffic to
   share the same SR Flex-Algorithm computed paths and SIDs.

8.  Network Resource Partition Protocol Extensions

   Routing protocols may need to be extended to carry additional per NRP
   link state.  For example, [RFC5305], [RFC3630], and [RFC7752] are
   ISIS, OSPF, and BGP protocol extensions to exchange network link
   state information to allow ingress TE routers and PCE(s) to do proper
   path placement in the network.  The extensions required to support
   network slicing may be defined in other documents, and are outside



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   the scope of this document.

   The instantiation of an NRP Policy may need to be automated.
   Multiple options are possible to facilitate automation of
   distribution of an NRP Policy to capable devices.

   For example, a YANG data model for the NRP Policy may be supported on
   network devices and controllers.  A suitable transport (e.g., NETCONF
   [RFC6241], RESTCONF [RFC8040], or gRPC) may be used to enable
   configuration and retrieval of state information for slice policies
   on network devices.  The NRP Policy YANG data model is outside the
   scope of this document.

9.  Outstanding Issues

   Note to RFC Editor: Please remove this section prior to publication.

   This section records non-blocking issues that were raised during the
   Working Group Adoption Poll for the document.  The below list of
   issues needs to be fully addressed before progressing the document to
   publication in IESG.

   1.   Add new Appendix section with examples for the NRP modes
        described in Section 4.

   2.   Add text to clarify the relationship between Slice-Flow
        Aggregates, the NRP Policy, and the NRP.

   3.   Remove redundant references to Diffserv behaviors.

   4.   Elaborate on the SFA packet treatment when no rules to associate
        the packet to an NRP are defined in the NRP Policy.

   5.   Clarify the NRP instantiation through the NRP Policy
        enforcement.

   6.   Clarify how the solution caters to the different IETF Network
        Slice Service Demarcation Point locations described in
        Section 4.2 of [I-D.ietf-teas-ietf-network-slices].

   7.   Clarify the relationship the underlay physical network, the
        filter topology and the NRP resources.

   8.   Expand on how isolation between NRPs can be realized depending
        on the deployed NRP mode.

   9.   Revise Section 5.2.3 to describe how nodes can discover NRP
        incapable downstream neighbors.



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   10.  Expand Section 11 on additional security threats introduced with
        the solution.

   11.  Expand Section 5.2 on NRP domain boundary and multi-domain
        aspects.

10.  IANA Considerations

   This document has no IANA actions.

11.  Security Considerations

   The main goal of network slicing is to allow for varying treatment of
   traffic from multiple different network slices that are utilizing a
   common network infrastructure and to allow for different levels of
   services to be provided for traffic traversing a given network
   resource.

   A variety of techniques may be used to achieve this, but the end
   result will be that some packets may be mapped to specific resources
   and may receive different (e.g., better) service treatment than
   others.  The mapping of network traffic to a specific NRP is
   indicated primarily by the FAS, and hence an adversary may be able to
   utilize resources allocated to a specific NRP by injecting packets
   carrying the same FAS field in their packets.

   Such theft-of-service may become a denial-of-service attack when the
   modified or injected traffic depletes the resources available to
   forward legitimate traffic belonging to a specific NRP.

   The defense against this type of theft and denial-of-service attacks
   consists of a combination of traffic conditioning at NRP domain
   boundaries with security and integrity of the network infrastructure
   within an NRP domain.

12.  Acknowledgement

   The authors would like to thank Krzysztof Szarkowicz, Swamy SRK,
   Navaneetha Krishnan, Prabhu Raj Villadathu Karunakaran, and Mohamed
   Boucadair for their review of this document and for providing
   valuable feedback on it.  The authors would also like to thank Adrian
   Farrel for detailed discussions that resulted in Section 3.

13.  Contributors

   The following individuals contributed to this document:





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      Colby Barth
      Juniper Networks
      Email: cbarth@juniper.net

      Srihari R.  Sangli
      Juniper Networks
      Email: ssangli@juniper.net

      Chandra Ramachandran
      Juniper Networks
      Email: csekar@juniper.net

      Adrian Farrel
      Old Dog Consulting
      United Kingdom
      Email: adrian@olddog.co.uk

14.  References

14.1.  Normative References

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

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

14.2.  Informative References









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   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", Work in Progress,
              Internet-Draft, draft-ietf-lsr-flex-algo-19, 7 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-
              19.txt>.

   [I-D.ietf-teas-ietf-network-slices]
              Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
              K., Contreras, L. M., and J. Tantsura, "Framework for IETF
              Network Slices", Work in Progress, Internet-Draft, draft-
              ietf-teas-ietf-network-slices-10, 27 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-ietf-
              network-slices-10.txt>.

   [I-D.ietf-teas-rfc3272bis]
              Farrel, A., "Overview and Principles of Internet Traffic
              Engineering", Work in Progress, Internet-Draft, draft-
              ietf-teas-rfc3272bis-16, 24 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-
              rfc3272bis-16.txt>.

   [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>.

   [RFC2702]  Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
              McManus, "Requirements for Traffic Engineering Over MPLS",
              RFC 2702, DOI 10.17487/RFC2702, September 1999,
              <https://www.rfc-editor.org/info/rfc2702>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

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





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   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

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

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

Authors' Addresses

   Tarek Saad
   Juniper Networks
   Email: tsaad@juniper.net


   Vishnu Pavan Beeram
   Juniper Networks
   Email: vbeeram@juniper.net


   Jie Dong
   Huawei Technologies
   Email: jie.dong@huawei.com


   Bin Wen
   Comcast
   Email: Bin_Wen@cable.comcast.com


   Daniele Ceccarelli
   Ericsson
   Email: daniele.ceccarelli@ericsson.com


   Joel Halpern
   Ericsson
   Email: joel.halpern@ericsson.com


   Shaofu Peng
   ZTE Corporation



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   Email: peng.shaofu@zte.com.cn


   Ran Chen
   ZTE Corporation
   Email: chen.ran@zte.com.cn


   Xufeng Liu
   Volta Networks
   Email: xufeng.liu.ietf@gmail.com


   Luis M. Contreras
   Telefonica
   Email: luismiguel.contrerasmurillo@telefonica.com


   Reza Rokui
   Ciena
   Email: rrokui@ciena.com


   Luay Jalil
   Verizon
   Email: luay.jalil@verizon.com

























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