Network Working Group                                     A. Farrel, Ed.
Internet-Draft                                        Old Dog Consulting
Intended status: Informational                                  J. Drake
Expires: 5 September 2022                               Juniper Networks
                                                                R. Rokui
                                                                   Ciena
                                                                S. Homma
                                                                     NTT
                                                            K. Makhijani
                                                               Futurewei
                                                          L.M. Contreras
                                                              Telefonica
                                                             J. Tantsura
                                                               Microsoft
                                                            4 March 2022


                   Framework for IETF Network Slices
                 draft-ietf-teas-ietf-network-slices-07

Abstract

   This document describes network slicing in the context of networks
   built from IETF technologies.  It defines the term "IETF Network
   Slice" and establishes the general principles of network slicing in
   the IETF context.

   The document discusses the general framework for requesting and
   operating IETF Network Slices, the characteristics of an IETF Network
   Slice, the necessary system components and interfaces, and how
   abstract requests can be mapped to more specific technologies.  The
   document also discusses related considerations with monitoring and
   security.

   This document also provides definitions of related terms to enable
   consistent usage in other IETF documents that describe or use aspects
   of IETF Network Slices.

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/.




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   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 5 September 2022.

Copyright Notice

   Copyright (c) 2022 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
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   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terms and Abbreviations . . . . . . . . . . . . . . . . . . .   5
     2.1.  Core Terminology  . . . . . . . . . . . . . . . . . . . .   5
   3.  IETF Network Slice Objectives . . . . . . . . . . . . . . . .   7
     3.1.  Definition and Scope of IETF Network Slice  . . . . . . .   7
     3.2.  IETF Network Slice Service  . . . . . . . . . . . . . . .   8
       3.2.1.  Ancillary SDPs  . . . . . . . . . . . . . . . . . . .  11
   4.  IETF Network Slice System Characteristics . . . . . . . . . .  11
     4.1.  Objectives for IETF Network Slices  . . . . . . . . . . .  11
       4.1.1.  Service Level Objectives  . . . . . . . . . . . . . .  12
       4.1.2.  Service Level Expectations  . . . . . . . . . . . . .  14
     4.2.  IETF Network Slice Service Demarcation Points . . . . . .  16
     4.3.  IETF Network Slice Decomposition  . . . . . . . . . . . .  18
   5.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .  19
     5.1.  IETF Network Slice Stakeholders . . . . . . . . . . . . .  19
     5.2.  Expressing Connectivity Intents . . . . . . . . . . . . .  19
     5.3.  IETF Network Slice Controller (NSC) . . . . . . . . . . .  21
       5.3.1.  IETF Network Slice Controller Interfaces  . . . . . .  23
       5.3.2.  Management Architecture . . . . . . . . . . . . . . .  25
     5.4.  IETF Network Slice Structure  . . . . . . . . . . . . . .  25
   6.  Realizing IETF Network Slices . . . . . . . . . . . . . . . .  27
     6.1.  Architecture to Realize IETF Network Slices . . . . . . .  27
     6.2.  Procedures to Realize IETF Network Slices . . . . . . . .  30
     6.3.  Applicability of ACTN to IETF Network Slices  . . . . . .  31



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     6.4.  Applicability of Enhanced VPNs to IETF Network Slices . .  31
     6.5.  Network Slicing and Aggregation in IP/MPLS Networks . . .  32
   7.  Isolation in IETF Network Slices  . . . . . . . . . . . . . .  32
     7.1.  Isolation as a Service Requirement  . . . . . . . . . . .  32
     7.2.  Isolation in IETF Network Slice Realization . . . . . . .  33
   8.  Management Considerations . . . . . . . . . . . . . . . . . .  33
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  33
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  34
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  35
   12. Informative References  . . . . . . . . . . . . . . . . . . .  35
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  38
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  39
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  40

1.  Introduction

   A number of use cases benefit from network connections that along
   with the connectivity provide assurance of meeting a specific set of
   objectives with respect to network resources use.  This connectivity
   and resource commitment is referred to as a network slice.  Since the
   term network slice is rather generic, the qualifying term "IETF" is
   used in this document to limit the scope of network slice to network
   technologies described and standardized by the IETF.  This document
   defines the concept of IETF Network Slices that provide connectivity
   coupled with a set of specific commitments of network resources
   between a number of endpoints (known as Service Demarcation Points
   (SDPs) - see Section 2.1) over a shared underlay network.  Services
   that might benefit from IETF Network Slices include, but are not
   limited to:

   *  5G services (e.g. eMBB, URLLC, mMTC)(See [TS23501])

   *  Network wholesale services

   *  Network infrastructure sharing among operators

   *  NFV connectivity and Data Center Interconnect

   IETF Network Slices are created and managed within the scope of one
   or more network technologies (e.g., IP, MPLS, optical).  They are
   intended to enable a diverse set of applications that have different
   requirements to coexist on the shared underlay network.  A request
   for an IETF Network Slice is agnostic to the technology in the
   underlying network so as to allow a customer to describe their
   network connectivity objectives in a common format, independent of
   the underlying technologies used.





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   This document also provides a framework for discussing IETF Network
   Slices.  This framework is intended as a structure for discussing
   interfaces and technologies.  It is not intended to specify a new set
   of concrete interfaces or technologies.  Rather, the idea is that
   existing or under-development IETF technologies (plural) can be used
   to realize the concepts expressed herein.

   For example, virtual private networks (VPNs) have served the industry
   well as a means of providing different groups of users with logically
   isolated access to a common network.  The common or base network that
   is used to support the VPNs is often referred to as an underlay
   network, and the VPN is often called an overlay network.  An overlay
   network may, in turn, serve as an underlay network to support another
   overlay network.

   Note that it is conceivable that extensions to these IETF
   technologies are needed in order to fully support all the ideas that
   can be implemented with slices.  Evaluation of existing technologies,
   proposed extensions to existing protocols and interfaces, and the
   creation of new protocols or interfaces is outside the scope of this
   document.

1.1.  Background

   Driven largely by needs surfacing from 5G, the concept of network
   slicing has gained traction ([NGMN-NS-Concept], [TS23501], and
   [TS28530]).  In [TS23501], a Network Slice is defined as "a logical
   network that provides specific network capabilities and network
   characteristics", and a Network Slice Instance is defined as "A set
   of Network Function instances and the required resources (e.g.
   compute, storage and networking resources) which form a deployed
   Network Slice."  According to [TS28530], an end-to-end network slice
   consists of three major types of network segments: Radio Access
   Network (RAN), Transport Network (TN) and Core Network (CN).  An IETF
   Network Slice provides the required connectivity between different
   entities in RAN and CN segments of an end-to-end network slice, with
   a specific performance commitment.  For each end-to-end network
   slice, the topology and performance requirement on a customer's use
   of IETF Network Slice can be very different, which requires the
   underlay network to have the capability of supporting multiple
   different IETF Network Slices.

   While network slices are commonly discussed in the context of 5G, it
   is important to note that IETF Network Slices are a narrower concept,
   and focus primarily on particular network connectivity aspects.
   Other systems, including 5G deployments, may use IETF Network Slices
   as a component to create entire systems and concatenated constructs
   that match their needs, including end-to-end connectivity.



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   A IETF Network Slice could span multiple technologies and multiple
   administrative domains.  Depending on the IETF Network Slice
   customer's requirements, an IETF Network Slice could be isolated from
   other, often concurrent IETF Network Slices in terms of data, control
   and management planes.

   The customer expresses requirements for a particular IETF Network
   Slice by specifying what is required rather than how the requirement
   is to be fulfilled.  That is, the IETF Network Slice customer's view
   of an IETF Network Slice is an abstract one.

   Thus, there is a need to create logical network structures with
   required characteristics.  The customer of such a logical network can
   require a degree of isolation and performance that previously might
   not have been satisfied by overlay VPNs.  Additionally, the IETF
   Network Slice customer might ask for some level of control of their
   virtual networks, e.g., to customize the service paths in a network
   slice.

   This document specifies definitions and a framework for the provision
   of an IETF Network Slice service.  Section 6 briefly indicates some
   candidate technologies for realizing IETF Network Slices.

2.  Terms and Abbreviations

   The following abbreviations are used in this document.

   *  NSC: Network Slice Controller

   *  SLA: Service Level Agreement

   *  SLI: Service Level Indicator

   *  SLO: Service Level Objective

   The meaning of these abbreviations is defined in greater details in
   the remainder of this document.

2.1.  Core Terminology

   The following terms are presented here to give context.  Other
   terminology is defined in the remainder of this document.

   Customer:  A customer is the requester of an IETF Network Slice
      service.  Customers may request monitoring of SLOs.  A customer
      may be an entity such as an enterprise network or a network
      operator, an individual working at such an entity, a private
      individual contracting for a service, or an application or



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      software component.  A customer may be an external party
      (classically a paying customer) or a division of a network
      operator that uses the service provided by another division of the
      same operator.  Other terms that have been applied to the customer
      role are "client" and "consumer".

   Provider:  A provider is the organization that delivers an IETF
      Network Slice service.  A provider is the network operator that
      controls the network resources used to construct the network slice
      (that is, the network that is sliced).  The provider's network
      maybe a physical network or may be a virtual network supplied by
      another service provider.

   Customer Edge (CE):  The customer device that provides connectivity
      to a service provider.  Examples include routers, Ethernet
      switches, firewalls, 4G/5G RAN or Core nodes, application
      accelerators, server load balancers, HTTP header enrichment
      functions, and PEPs (Performance Enhancing Proxy).  In some
      circumstances CEs are provided to the customer and managed by the
      provider.

   Provider Edge:  The device within the provider network to which a CE
      is attached.  A CE may be attached to multiple PEs, and multiple
      CEs may be attached to a given PE.

   Attachment Circuit (AC):  A channel connecting a CE and a PE over
      which packets that belong to an IETF Network Slice service are
      exchanged.  The customer and provider agree (through
      configuration) on which values in which combination of layer 2 and
      layer 3 header and payload fields within a packet identify to
      which {IETF Network Slice service, connectivity construct, and
      SLOs/SLEs} that packet is assigned.  The customer and provider may
      agree on a per {IETF Network Slice service, connectivity
      construct, and SLOs/SLEs} basis to police or shape traffic on the
      AC in both the ingress (CE to PE) direction and egress (PE to CE)
      direction, This ensures that the traffic is within the capacity
      profile that is agreed in an IETF Network Slice service.  Excess
      traffic is dropped by default, unless specific out-of-profile
      policies are agreed between the customer and the provider.  As
      described in Section 4.2 the AC may be part of the IETF Network
      Slice service or may be external to it.

   Service Demarcation Point (SDP):  The point at which an IETF Network
      Slice service is delivered by a service provider to a customer.
      Depending on the service delivery model (see Section 4.2 this may
      be a CE or a PE, and could be a device, a software component, or
      in the case of network functions virtualization (for example), be
      an abstract function supported within the provider's network.



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      Each SDP must have a unique identifier (e.g., an IP address or MAC
      address) within a given IETF Network Slice service and may use the
      same identifier in multiple IETF Network Slice services.

      An SDP may be abstracted as a Service Attachment Point (SAP)
      [I-D.ietf-opsawg-sap] for the purpose generalizing the concept
      across multiple service types and representing it in management
      and configuration systems.

3.  IETF Network Slice Objectives

   It is intended that IETF Network Slices can be created to meet
   specific requirements, typically expressed as bandwidth, latency,
   latency variation, and other desired or required characteristics.
   Creation is initiated by a management system or other application
   used to specify network-related conditions for particular traffic
   flows.

   It is also intended that, once created, these slices can be
   monitored, modified, deleted, and otherwise managed.

   It is also intended that applications and components will be able to
   use these IETF Network Slices to move packets between the specified
   end-points of the service in accordance with specified
   characteristics.

3.1.  Definition and Scope of IETF Network Slice

   An IETF Network Slice service enables connectivity between a set of
   Service Demarcation Points (SDPs) with specific Service Level
   Objectives (SLOs) and Service Level Expectations (SLEs) over a common
   underlay network.

   An IETF Network Slice combines the connectivity resource requirements
   and associated network behaviors such as bandwidth, latency, jitter,
   and network functions with other resource behaviors such as compute
   and storage availability.  The definition of an IETF Network Slice
   service is independent of the connectivity and technologies used in
   the underlay network.  This allows an IETF Network Slice service
   customer to describe their network connectivity and relevant
   objectives in a common format, independent of the underlying
   technologies used.









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   IETF Network Slices may be combined hierarchically, so that a network
   slice may itself be sliced.  They may also be combined sequentially
   so that various different networks can each be sliced and the network
   slices placed into a sequence to provide an end-to-end service.  This
   form of sequential combination is utilized in some services such as
   in 3GPP's 5G network [TS23501].

   An IETF Network Slice service is agnostic to the technology of the
   underlying network, and its realization may be selected based upon
   multiple considerations including its service requirements and the
   capabilities of the underlay network.

   The term "Slice" refers to a set of characteristics and behaviours
   that separate one type of user-traffic from another.  An IETF Network
   Slice assumes that an underlay network is capable of changing the
   configurations of the network devices on demand, through in-band
   signaling or via controller(s) and fulfilling all or some of SLOs/
   SLEs to all of the traffic in the slice or to specific flows.

3.2.  IETF Network Slice Service

   A service provider delivers an IETF Network Slice service for a
   customer.  The IETF Network Slice service is specified in terms of a
   set of SDPs, a set of one or more connectivity constructs between
   subsets of these SDPs, and a set of SLOs and SLEs for each SDP
   sending to each connectivity construct.  A communication type (point-
   to-point (P2P) both unidirectional and bidirectional, point-to-
   multipoint (P2MP), multipoint-to-point (MP2P), multipoint-to-
   multipoint (MP2MP), or any-to-any (A2A)) is specified for each
   connectivity construct.  That is, in a given IETF Network Slice
   service there may be one or more connectivity constructs of the same
   or different type, each connectivity construct may be between a
   different subset of SDPs, and for a given connectivity construct each
   sending SDP has its own set of SLOs and SLEs, and the SLOs and SLEs
   in each set may be different.  Note that a service provider may
   decide how many connectivity constructs per IETF Network Slice
   service it wishes to support.

   This approach results in the following possible connectivity
   constructs:

   *  For a P2P connectivity construct, there is one sending SDP and one
      receiving SDP.  This construct is like a private wire or a tunnel.
      All traffic injected at the sending SDP is intended to be received
      by the receiving SDP.  The SLOs and SLEs apply at the sender (and
      implicitly at the receiver).





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   *  A bidirectional P2P connectivity construct may also be defined,
      with two SDPs each of which may send to the other.  There are two
      sets of SLOs and SLEs which may be different and each of which
      applies to one of the SDPs as a sender.

   *  For a P2MP connectivity construct, there is only one sending SDP
      and more than one receiving SDP.  This is like a P2MP tunnel or
      multi-access VLAN segment.  All traffic from the sending SDP is
      intended to be received by all the receiving SDPs.  There is one
      set of SLOs and SLEs that apply at the sending SDP (and implicitly
      at all receiving SDPs).  Activating unicast or multicast
      capabilities to deliver an IETF Slice service can be explicitly
      requested by a customer or can be an engineering decision of a
      service provider based on capabilities of the network and
      operational choices.

   *  An MP2P connectivity construct has N SDPs: there is one receiving
      SDP and (N - 1) sending SDPs.  This is like a set of P2P
      connections all with a common receiver.  All traffic injected at
      any sending SDP is received by the single receiving SDP.  Each
      sending SDP has its own set of SLOs and SLEs, and they may all be
      different (the combination of those SLOs and SLEs gives the
      implicit SLOs and SLEs for the receiving SDP - that is, the
      receiving SDP is expected to receive all traffic from all
      senders).

   *  In an MP2MP connectivity construct each of the N SDPs can be a
      sending SDP such that its traffic is delivered to all of the other
      SDPs.  Each sending SDP has its own set of SLOs and SLEs and they
      may all be different.  The combination of those SLOs/SLEs gives
      the implicit SLOs/SLEs for each/all of the receiving SDPs since
      each receiving SDP is expect to receive all traffic from all/any
      sender.


















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   *  With an A2A construct, any sending SDP may send to any one
      receiving SDP or any set of receiving SDPs in the construct.
      There is an implicit level of routing in this connectivity
      construct that is not present in the other connectivity constructs
      as the construct must determine to which receiving SDPs to deliver
      each packet.  The SLOs/SLEs apply to individual sending SDPs and
      individual receiving SDPs, but there is no implicit linkage and a
      sending SDP may be "disappointed" if the receiver is over-
      subscribed.  This construct may be used to support P2P traffic
      between any pair of SDPs or to support multicast or broadcast
      traffic from one SDP to a set of other SDPs.  In the latter case,
      whether the service is delivered using multicast within the
      provider's network or using "ingress replication" or some other
      means is out of scope of the specification of the service.  A
      service provider may choose to support A2A constructs but limit
      the traffic to P2P.

   If an SDP has multiple attachment circuits to a given IETF Network
   Slice service and they are operating in single-active mode, then all
   traffic between the SDP and its attached PEs transits a single
   attachment circuit; if they are operating in in all-active mode, then
   traffic between the SDP and its attached PEs is distributed across
   all of the active attachment circuits.

   A given sending SDP may be part of multiple connectivity constructs
   within a single IETF Network Slice service, and the SDP may have
   different SLOs and SLEs for each connectivity construct to which it
   is sending.  Note that a given sending SDP's SLOs and SLEs for a
   given connectivity construct apply between it and each of the
   receiving SDPs for that connectivity construct.

   An IETF Network Slice service provider may freely make a deployment
   choice as to whether to offer a 1:1 relationship between IETF Network
   Slice service and connectivity construct, or to support multiple
   connectivity constructs in a single IETF Network Slice service.  In
   the former case, the provider might need to deliver multiple IETF
   Network Slice services to achieve the function of the second case.

   It should be noted that per Section 9 of [RFC4364] an IETF Network
   Slice service customer may actually provide IETF Network Slice
   services to other customers in a mode sometimes referred to as
   "carrier's carrier".  In this case, the underlying IETF Network Slice
   service provider may be owned and operated by the same or a different
   provider network.  As noted in Section 3.1, network slices may be
   composed hierarchically or serially.






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   Section 4.2 provides a description of endpoints in the context of
   IETF network slicing.  These are known as Service Demarcation Points
   (SDPs).  For a given IETF Network Slice service, the customer and
   provider agree, on a per-SDP basis which end of the attachment
   circuit provides the service demarcation point (i.e., whether the
   attachment circuit is inside or outside the IETF Network Slice
   service).  This determines whether the attachment circuit is subject
   to the set of SLOs and SLEs at the specific SDP.

3.2.1.  Ancillary SDPs

   It may be the case that the set of SDPs needs to be supplemented with
   additional senders or receivers.  An additional sender could be, for
   example, an IPTV or DNS server either within the provider's network
   or attached to it, while an extra receiver could be, for example, a
   node reachable via the Internet.  This will be modelled as a set of
   ancillary SDPs which supplement the other SDPs in one or more
   connectivity constructs, or which have their own connectivity
   constructs.  Note that an ancillary SDP can either have a resolvable
   address, e.g., an IP address or MAC address, or it may be a
   placeholder, e.g., IPTV or DNS server, which is resolved within the
   provider's network when the IETF Network Slice service is
   instantiated.

4.  IETF Network Slice System Characteristics

   The following subsections describe the characteristics of IETF
   Network Slices.

4.1.  Objectives for IETF Network Slices

   An IETF Network Slice service is defined in terms of quantifiable
   characteristics known as Service Level Objectives (SLOs) and
   unquantifiable characteristics known as Service Level Expectations
   (SLEs).  SLOs are expressed in terms Service Level Indicators (SLIs),
   and together with the SLEs form the contractual agreement between
   service customer and service provider known as a Service Level
   Agreement (SLA).

   The terms are defined as follows:

   *  A Service Level Indicator (SLI) is a quantifiable measure of an
      aspect of the performance of a network.  For example, it may be a
      measure of throughput in bits per second, or it may be a measure
      of latency in milliseconds.






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   *  A Service Level Objective (SLO) is a target value or range for the
      measurements returned by observation of an SLI.  For example, an
      SLO may be expressed as "SLI <= target", or "lower bound <= SLI <=
      upper bound".  A customer can determine whether the provider is
      meeting the SLOs by performing measurements on the traffic.

   *  A Service Level Expectation (SLE) is an expression of an
      unmeasurable service-related request that a customer of an IETF
      Network Slice makes of the provider.  An SLE is distinct from an
      SLO because the customer may have little or no way of determining
      whether the SLE is being met, but they still contract with the
      provider for a service that meets the expectation.

   *  A Service Level Agreement (SLA) is an explicit or implicit
      contract between the customer of an IETF Network Slice service and
      the provider of the slice.  The SLA is expressed in terms of a set
      of SLOs and SLEs that are to be applied for a given connectivity
      construct between a sending SDP and the set of receiving SDPs, and
      may describe the extent to which divergence from individual SLOs
      and SLEs can be tolerated, and commercial terms as well as any
      consequences for violating these SLOs and SLEs.

4.1.1.  Service Level Objectives

   SLOs define a set of measurable network attributes and
   characteristics that describe an IETF Network Slice service.  SLOs do
   not describe how an IETF Network Slice service is implemented or
   realized in the underlying network layers.  Instead, they are defined
   in terms of dimensions of operation (time, capacity, etc.),
   availability, and other attributes.

   An IETF Network Slice service may include multiple connection
   constructs that associate sets of endpoints (SDPs).  SLOs apply to a
   given connectivity construct and apply to specific directions of
   traffic flow.  That is, they apply to a specific sending SDP and the
   connection to specific receiving SDPs.

   The SLOs are combined with Service Level Expectations in an SLA.

4.1.1.1.  Some Common SLOs

   SLOs can be described as 'Directly Measurable Objectives': they are
   always measurable.  See Section 4.1.2 for the description of Service
   Level Expectations which are unmeasurable service-related requests
   sometimes known as 'Indirectly Measurable Objectives'.






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   Objectives such as guaranteed minimum bandwidth, guaranteed maximum
   latency, maximum permissible delay variation, maximum permissible
   packet loss rate, and availability are 'Directly Measurable
   Objectives'.  Future specifications (such as IETF Network Slice
   service YANG models) may precisely define these SLOs, and other SLOs
   may be introduced as described in Section 4.1.1.2.

   The definition of these objectives are as follows:

   Guaranteed Minimum Bandwidth:  Minimum guaranteed bandwidth between
      two endpoints at any time.  The bandwidth is measured in data rate
      units of bits per second and is measured unidirectionally.

   Guaranteed Maximum Latency:  Upper bound of network latency when
      transmitting between two endpoints.  The latency is measured in
      terms of network characteristics (excluding application-level
      latency).  [RFC2681] and [RFC7679] discuss round trip times and
      one-way metrics, respectively.

   Maximum Permissible Delay Variation:  Packet delay variation (PDV) as
      defined by [RFC3393], is the difference in the one-way delay
      between sequential packets in a flow.  This SLO sets a maximum
      value PDV for packets between two endpoints.

   Maximum Permissible Packet Loss Rate:  The ratio of packets dropped
      to packets transmitted between two endpoints over a period of
      time.  See [RFC7680].

   Availability:  The ratio of uptime to the sum of uptime and downtime,
      where uptime is the time the IETF Network Slice is available in
      accordance with the SLOs associated with it.

4.1.1.2.  Other Service Level Objectives

   Additional SLOs may be defined to provide additional description of
   the IETF Network Slice service that a customer requests.  These would
   be specified in further documents.

   If the IETF Network Slice service is traffic aware, other traffic
   specific characteristics may be valuable including MTU, traffic-type
   (e.g., IPv4, IPv6, Ethernet or unstructured), or a higher-level
   behavior to process traffic according to user-application (which may
   be realized using network functions).








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4.1.2.  Service Level Expectations

   SLEs define a set of network attributes and characteristics that
   describe an IETF Network Slice service, but which are not directly
   measurable by the customer.  Even though the delivery of an SLE
   cannot usually be determined by the customer, the SLEs form an
   important part of the contract between customer and provider.

   Quite often, an SLE will imply some details of how an IETF Network
   Slice service is realized by the provider, although most aspects of
   the implementation in the underlying network layers remain a free
   choice for the provider.

   SLEs may be seen as aspirational on the part of the customer, and
   they are expressed as behaviors that the provider is expected to
   apply to the network resources used to deliver the IETF Network Slice
   service.  The SLEs are combined with SLOs in an SLA.

   An IETF Network Slice service may include multiple connection
   constructs that associate sets of endpoints (SDPs).  SLEs apply to a
   given connectivity construct and apply to specific directions of
   traffic flow.  That is, they apply to a specific sending SDP and the
   connection to specific receiving SDPs.  However, being more general
   in nature that SLOs, SLEs may commonly be applied to all connection
   constructs in an IETF Network Slice service.

4.1.2.1.  Some Common SLEs

   SLEs can be described as 'Indirectly Measurable Objectives': they are
   not generally directly measurable by the customer.

   Security, geographic restrictions, maximum occupancy level, and
   isolation are example SLEs as follows.

   Security:  A customer may request that the provider applies
      encryption or other security techniques to traffic flowing between
      SDPs of an IETF Network Slice service.  For example, the customer
      could request that only network links that have MACsec [MACsec]
      enabled are used to realize the IETF Network Slice service.

      This SLE may include the request for encryption (e.g., [RFC4303])
      between the two SDPs explicitly to meet architecture
      recommendations as in [TS33.210] or for compliance with [HIPAA] or
      [PCI].

      Whether or not the provider has met this SLE is generally not
      directly observable by the customer and cannot be measured as a
      quantifiable metric.



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      Please see further discussion on security in Section 9.

   Geographic Restrictions:  A customer may request that certain
      geographic limits are applied to how the provider routes traffic
      for the IETF Network Slice service.  For example, the customer may
      have a preference that its traffic does not pass through a
      particular country for political or security reasons.

      Whether or not the provider has met this SLE is generally not
      directly observable by the customer and cannot be measured as a
      quantifiable metric.

   Maximal Occupancy Level:  The maximal occupancy level specifies the
      number of flows to be admitted and optionally a maximum number of
      countable resource units (e.g., IP or MAC addresses) an IETF
      Network Slice service can consume.  Since an IETF Network Slice
      service may include multiple connection constructs, this SLE
      should also say whether it applies for the entire IETF Network
      Slice service, for group of connections, or on a per connection
      basis.

      Again, a customer may not be able to fully determine whether this
      SLE is being met by the provider.

   Isolation:  As described in Section 7, a customer may request that
      its traffic within its IETF Network Slice service is isolated from
      the effects of other network services supported by the same
      provider.  That is, if another service exceeds capacity or has a
      burst of traffic, the customer's IETF Network Slice service should
      remain unaffected and there should be no noticeable change to the
      quality of traffic delivered.

      In general, a customer cannot tell whether a service provider is
      meeting this SLE.  They cannot tell whether the variation of an
      SLI is because of changes in the underlying network or because of
      interference from other services carried by the network.  And if
      the service varies within the allowed bounds of the SLOs, there
      may be no noticeable indication that this SLE has been violated.

   Diversity:  A customer may request that traffic on the connection
      between one set of SDPs should use different network resources
      from the traffic between another set of SDPs.  This might be done
      to enhance the availability of the IETF Network Slice service.

      While availability is a measurable objective (see Section 4.1.1.1)
      this SLE requests a finer grade of control and is not directly
      measurable (although the customer might become suspicious if two
      connections fail at the same time).



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4.2.  IETF Network Slice Service Demarcation Points

   As noted in Section 3.1, an IETF Network Slice is a logical network
   topology connecting a number of endpoints.  Section 3.2 goes on to
   describe how the IETF Network Slice service is composed of a set of
   one or more connectivity constructs that describe connectivity
   between the service demarcation points across the underlying network.

   The characteristics of IETF Network Slice Service Demarcation Points
   (SDPs) are as follows:

   *  SDPs are conceptual points of connection to an IETF Network Slice.
      As such, they serve as the IETF Network Slice ingress/ egress
      points.

   *  Each SDP maps to a device, application, or a network function,
      such as (but not limited to) routers, switches, firewalls, WAN,
      4G/5G RAN nodes, 4G/5G Core nodes, application accelerators,
      server load balancers, NAT44 [RFC3022], NAT64 [RFC6146], HTTP
      header enrichment functions, and Performance Enhancing Proxies
      (PEPs) [RFC3135].

   *  An SDP is identified by a unique identifier in the context of an
      IETF Network Slice customer.

   *  Each SDP is associated with a set of provider-scope identifiers
      such as IP addresses, encapsulation-specific identifiers (e.g.,
      VLAN tag, MPLS Label), interface/port numbers, node ID, etc.

   *  SDPs are mapped to endpoints of services/tunnels/paths within the
      IETF Network Slice during its initialization and realization.

      -  A combination of the SDP identifier and SDP provider-network-
         scope identifiers define an SDP in the context of the Network
         Slice Controller (NSC).

      -  The NSC will use the SDP provider-network-scope identifiers as
         part of the process of realizing the IETF Network Slice.

   For a given IETF Network Slice service, the IETF Network Slice
   customer and provider agree where the endpoint (i.e., the service
   demarcation point) is located.  This determines what resources at the
   edge of the network form part of the IETF Network Slice and are
   subject to the set of SLOs and SLEs for a specific endpoint.

   Figure 1 shows different potential scopes of an IETF Network Slice
   that are consistent with the different SDP positions.  For the
   purpose of example and without loss of generality, the figure shows



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   customer edge (CE) and provider edge (PE) nodes connected by
   attachment circuits (ACs).  Notes after the figure give some
   explanations.


             |<---------------------- (1) ---------------------->|
             |                                                   |
             | |<-------------------- (2) -------------------->| |
             | |                                               | |
             | |        |<----------- (3) ----------->|        | |
             | |        |                             |        | |
             | |        |  |<-------- (4) -------->|  |        | |
             | |        |  |                       |  |        | |
             V V   AC   V  V                       V  V   AC   V V
         +-----+   |    +-----+                 +-----+    |   +-----+
         |     |--------|     |                 |     |--------|     |
         | CE1 |   |    | PE1 |. . . . . . . . .| PE2 |    |   | CE2 |
         |     |--------|     |                 |     |--------|     |
         +-----+   |    +-----+                 +-----+    |   +-----+
            ^              ^                       ^              ^
            |              |                       |              |
            |              |                       |              |
         Customer       Provider                Provider       Customer
         Edge 1         Edge 1                  Edge 2         Edge 2



           Figure 1: Positioning IETF Service Demarcation Points

   Explanatory notes for Figure 1 are as follows:

   1.  If the CE is operated by the IETF Network Slice service provider,
       then the edge of the IETF Network Slice may be within the CE.  In
       this case the slicing process may utilize resources from within
       the CE such as buffers and queues on the outgoing interfaces.

   2.  The IETF Network Slice may be extended as far as the CE, to
       include the AC, but not to include any part of the CE.  In this
       case, the CE may be operated by the customer or the provider.
       Slicing the resources on the AC may require the use of traffic
       tagging (such as through Ethernet VLAN tags) or may require
       traffic policing at the AC link ends.

   3.  In another model, the SDPs of the IETF Network Slice are the
       customer-facing ports on the PEs.  This case can be managed in a
       way that is similar to a port-based VPN: each port (AC) or
       virtual port (e.g., VLAN tag) identifies the IETF Network Slice
       and maps to an IETF Network Slice SDP.



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   4.  Finally, the SDP may be within the PE.  In this mode, the PE
       classifies the traffic coming from the AC according to
       information (such as the source and destination IP addresses,
       payload protocol and port numbers, etc.) in order to place it
       onto an IETF Network Slice.

   The choice of which of these options to apply is entirely up to the
   network operator.  It may limit or enable the provisioning of
   particular managed services and the operator will want to consider
   how they want to manage CEs and what control they wish to offer the
   customer over AC resources.

   Note that Figure 1 shows a symmetrical positioning of SDP, but this
   decision can be taken on a per-SDP basis through agreement between
   the customer and provider.

   In practice, it may be necessary to map traffic not only onto an IETF
   Network Slice, but also onto a specific connectivity construct if the
   IETF Network Slice supports more than one connectivity construct with
   a source at the specific SDP.  The mechanism used will be one of the
   mechanisms described above, dependent on how the SDP is realized.

   Finally, note (as described in Section 2.1) that an SDP is an
   abstract endpoint of an IETF Network Slice service and as such may be
   a device or software component and may, in the case of netork
   functions virtualization (for example), be an abstract function
   supported within the provider's network.

4.3.  IETF Network Slice Decomposition

   Operationally, an IETF Network Slice may be composed of two or more
   IETF Network Slices as specified below.  Decomposed network slices
   are independently realized and managed.

   *  Hierarchical (i.e., recursive) composition: An IETF Network Slice
      can be further sliced into other network slices.  Recursive
      composition allows an IETF Network Slice at one layer to be used
      by the other layers.  This type of multi-layer vertical IETF
      Network Slice associates resources at different layers.

   *  Sequential composition: Different IETF Network Slices can be
      placed into a sequence to provide an end-to-end service.  In
      sequential composition, each IETF Network Slice would potentially
      support different dataplanes that need to be stitched together.







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5.  Framework

   A number of IETF Network Slice services will typically be provided
   over a shared underlying network infrastructure.  Each IETF Network
   Slice consists of both the overlay connectivity and a specific set of
   dedicated network resources and/or functions allocated in a shared
   underlay network to satisfy the needs of the IETF Network Slice
   customer.  In at least some examples of underlying network
   technologies, the integration between the overlay and various
   underlay resources is needed to ensure the guaranteed performance
   requested for different IETF Network Slices.

5.1.  IETF Network Slice Stakeholders

   An IETF Network Slice and its realization involves the following
   stakeholders and it is relevant to define them for consistent
   terminology.  The IETF Network Slice customer and IETF Network Slice
   provider (see Section 2.1) are also stakeholders.

   Orchestrator:  An orchestrator is an entity that composes different
      services, resource and network requirements.  It interfaces with
      the IETF NSC.

   IETF Network Slice Controller (NSC):  The NSC realizes an IETF
      Network Slice in the underlying network, and maintains and
      monitors the run-time state of resources and topologies associated
      with it.  A well-defined interface is needed to support
      interworking between different NSC implementations and different
      orchestrator implementations.

   Network Controller:  The Network Controller is a form of network
      infrastructure controller that offers network resources to the NSC
      to realize a particular network slice.  These may be existing
      network controllers associated with one or more specific
      technologies that may be adapted to the function of realizing IETF
      Network Slices in a network.

5.2.  Expressing Connectivity Intents

   An IETF Network Slice customer communicates with the NSC using the
   IETF Network Slice Service Interface.

   An IETF Network Slice customer may be a network operator who, in
   turn, provides the IETF Network Slice to another IETF Network Slice
   customer.






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   Using the IETF Network Slice Service Interface, a customer expresses
   requirements for a particular slice by specifying what is required
   rather than how that is to be achieved.  That is, the customer's view
   of a slice is an abstract one.  Customers normally have limited (or
   no) visibility into the provider network's actual topology and
   resource availability information.

   This should be true even if both the customer and provider are
   associated with a single administrative domain, in order to reduce
   the potential for adverse interactions between IETF Network Slice
   customers and other users of the underlay network infrastructure.

   The benefits of this model can include:

   *  Security: because the underlay network (or network operator) does
      not need to expose network details (topology, capacity, etc.) to
      IETF Network Slice customers the underlay network components are
      less exposed to attack;

   *  Layered Implementation: the underlay network comprises network
      elements that belong to a different layer network than customer
      applications, and network information (advertisements, protocols,
      etc.) that a customer cannot interpret or respond to (note - a
      customer should not use network information not exposed via the
      IETF Network Slice Service Interface, even if that information is
      available);

   *  Scalability: customers do not need to know any information beyond
      that which is exposed via the IETF Network Slice Service
      Interface.

   The general issues of abstraction in a TE network is described more
   fully in [RFC7926].

   This framework document does not assume any particular layer at which
   IETF Network Slices operate as a number of layers (including virtual
   L2, Ethernet or, IP connectivity) could be employed.

   Data models and interfaces are of course needed to set up IETF
   Network Slices, and specific interfaces may have capabilities that
   allow creation of specific layers.

   Layered virtual connections are comprehensively discussed in other
   IETF documents.  See, for instance, GMPLS-based networks [RFC5212]
   and [RFC4397], or Abstraction and Control of TE Networks (ACTN)
   [RFC8453] and [RFC8454].  The principles and mechanisms associated
   with layered networking are applicable to IETF Network Slices.




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   There are several IETF-defined mechanisms for expressing the need for
   a desired logical network.  The IETF Network Slice Service Interface
   carries data either in a protocol-defined format, or in a formalism
   associated with a modeling language.

   For instance:

   *  Path Computation Element (PCE) Communication Protocol (PCEP)
      [RFC5440] and GMPLS User-Network Interface (UNI) using RSVP-TE
      [RFC4208] use a TLV-based binary encoding to transmit data.

   *  Network Configuration Protocol (NETCONF) [RFC6241] and RESTCONF
      Protocol [RFC8040] use XML and JSON encoding.

   *  gRPC/GNMI [I-D.openconfig-rtgwg-gnmi-spec] uses a binary encoded
      programmable interface;

   *  For data modeling, YANG ([RFC6020] and [RFC7950]) may be used to
      model configuration and other data for NETCONF, RESTCONF, and GNMI
      - among others; ProtoBufs can be used to model gRPC and GNMI data.

   While several generic formats and data models for specific purposes
   exist, it is expected that IETF Network Slice management may require
   enhancement or augmentation of existing data models.  Further, it is
   possible that mechanisms will be needed to determine the feasibility
   of service requests before they are actually made.

5.3.  IETF Network Slice Controller (NSC)

   The IETF NSC takes abstract requests for IETF Network Slices and
   implements them using a suitable underlying technology.  An IETF NSC
   is the key building block for control and management of the IETF
   Network Slice.  It provides the creation/modification/deletion,
   monitoring and optimization of IETF Network Slices in a multi-domain,
   a multi-technology and multi-vendor environment.

   The main task of the IETF NSC is to map abstract IETF Network Slice
   requirements to concrete technologies and establish required
   connectivity, and ensuring that required resources are allocated to
   the IETF Network Slice.

   The IETF Network Slice Service Interface is needed for communicating
   details of a IETF Network Slice (configuration, selected policies,
   operational state, etc.), as well as providing information to a slice
   requester/customer about IETF Network Slice status and performance.
   The details for this IETF Network Slice Service Interface are not in
   scope for this document.




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   The controller provides the following functions:

   *  Provides an IETF Network Slice Service Interface for
      creation/modification/deletion of the IETF Network Slices tht is
      agnostic to the technology of the underlying network.  The API
      exposed by this interface communicates the Service Demarcation
      Points of the IETF Network Slice, IETF Network Slice SLO
      parameters (and possibly monitoring thresholds), applicable input
      selection (filtering) and various policies, and provides a way to
      monitor the slice.

   *  Determines an abstract topology connecting the SDPs of the IETF
      Network Slice that meets criteria specified via the IETF Network
      Slice Service Interface.  The NSC also retains information about
      the mapping of this abstract topology to underlying components of
      the IETF Network Slice as necessary to monitor IETF Network Slice
      status and performance.

   *  Provides "Mapping Functions" for the realization of IETF Network
      Slices.  In other words, it will use the mapping functions that:

      -  map IETF Network Slice Service Interface requests that are
         agnostic to the technology of the underlying network to
         technology-specific network configuration interfaces

      -  map filtering/selection information as necessary to entities in
         the underlay network.

   *  Via a network configuration interface, the controller collects
      telemetry data (e.g., OAM results, statistics, states, etc.) for
      all elements in the abstract topology used to realize the IETF
      Network Slice.

   *  Using the telemetry data from the underlying realization of a IETF
      Network Slice (i.e., services/paths/tunnels), evaluates the
      current performance against IETF Network Slice SLO parameters and
      exposes them to the IETF Network Slice customer via the IETF
      Network Slice Service Interface.  The IETF Network Slice Service
      Interface may also include a capability to provide notification in
      case the IETF Network Slice performance reaches threshold values
      defined by the IETF Network Slice customer.

   An IETF Network Slice customer is served by the IETF Network Slice
   Controller (NSC), as follows:

   *  The NSC takes requests from a management system or other
      application, which are then communicated via the IETF Network
      Slice Service Interface.  This interface carries data objects the



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      IETF Network Slice customer provides, describing the needed IETF
      Network Slices in terms of topology, applicable service level
      objectives (SLO), and any monitoring and reporting requirements
      that may apply.  Note that - in this context - "topology" means
      what the IETF Network Slice connectivity is meant to look like
      from the customer's perspective; it may be as simple as a list of
      mutually (and symmetrically) connected SDPs, or it may be
      complicated by details of connection asymmetry, per-connection SLO
      requirements, etc.

   *  These requests are assumed to be translated by one or more
      underlying systems, which are used to establish specific IETF
      Network Slice instances on top of an underlying network
      infrastructure.

   *  The NSC maintains a record of the mapping from customer requests
      to slice instantiations, as needed to allow for subsequent control
      functions (such as modification or deletion of the requested
      slices), and as needed for any requested monitoring and reporting
      functions.

5.3.1.  IETF Network Slice Controller Interfaces

   The interworking and interoperability among the different
   stakeholders to provide common means of provisioning, operating and
   monitoring the IETF Network Slices is enabled by the following
   communication interfaces (see Figure 2).

   IETF Network Slice Service Interface:  The IETF Network Slice Service
      Interface is an interface between a customer's higher level
      operation system (e.g., a network slice orchestrator) and the NSC.
      It is agnostic to the technology of the underlying network.  The
      customer can use this interface to communicate the requested
      characteristics and other requirements (i.e., the SLOs) for the
      IETF Network Slice, and the NSC can use the interface to report
      the operational state of an IETF Network Slice to the customer.

   Network Configuration Interface:  The Network Configuration Interface
      is an interface between the NSC and network controllers.  It is
      technology-specific and may be built around the many network
      models defined within the IETF.

   These interfaces can be considered in the context of the Service
   Model and Network Model described in [RFC8309] and, together with the
   Device Configuration Interface used by the Network Controllers,
   provides a consistent view of service delivery and realization.





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          +------------------------------------------+
          | Customer higher level operation system   |
          |   (e.g E2E network slice orchestrator)   |
          +------------------------------------------+
                               A
                               | IETF Network Slice Service Interface
                               V
          +------------------------------------------+
          |    IETF Network Slice Controller (NSC)   |
          +------------------------------------------+
                               A
                               | Network Configuration Interface
                               V
          +------------------------------------------+
          |           Network Controllers            |
          +------------------------------------------+


            Figure 2: Interface of IETF Network Slice Controller

5.3.1.1.  IETF Network Slice Service Interface

   The IETF Network Slice Controller provides an IETF Network Slice
   Service Interface that allows customers of network slices to request
   and monitor IETF Network Slices.  Customers operate on abstract IETF
   Network Slices, with details related to their realization hidden.

   The IETF Network Slice Service Interface complements various IETF
   services, tunnels, path models by providing an abstract layer on top
   of these models.

   The IETF Network Slice Service Interface is independent of type of
   network functions or services that need to be connected, i.e., it is
   independent of any specific storage, software, protocol, or platform
   used to realize physical or virtual network connectivity or functions
   in support of IETF Network Slices.

   The IETF Network Slice Service Interface uses protocol mechanisms and
   information passed over those mechanisms to convey desired attributes
   for IETF Network Slices and their status.  The information is
   expected to be represented as a well-defined data model, and should
   include at least SDP and connectivity information, SLO specification,
   and status information.

   To accomplish this, the IETF Network Slice Service Interface needs to
   convey information needed to support communication across the
   interface, in terms of identifying the IETF Network Slices, as well
   providing the above model information.



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5.3.2.  Management Architecture

   The management architecture described in Figure 2 may be further
   decomposed as shown in Figure 3.  This should also be seen in the
   context of the component architecture shown in Figure 5.


                  --------------
                 | Network      |
                 | Slice        |
                 | Orchestrator |
                  --------------
                   | IETF Network Slice
                   | Service Request
                   |                       Customer view
                 ..|................................
                  -v-------------------    Operator view
                 |Controller           |
                 |  ------------       |
                 | | IETF       |      |
                 | | Network    |      |
                 | | Slice      |      |
                 | | Controller |      |
                 | | (NSC)      |      |
                 |  ------------       |--> Virtual Network
                 |     | Network       |
                 |     | Configuration |
                 |     v               |
                 |  ------------       |
                 | | Network    |      |
                 | | Controller |      |
                 | | (NC)       |      |
                 |  ------------       |
                  ---------------------
                   | Device Configuration
                 ..|................................
                   v                       Underlay Network


     Figure 3: Interface of IETF Network Slice Management Architecture

5.4.  IETF Network Slice Structure

   An IETF Network Slice is a set of connections among various SDPs to
   form a logical network that meets the SLOs agreed upon.






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                 |------------------------------------------|
       SDP1 O....|                                          |....O SDP2
         .       |                                          |    .
         .       |             IETF Network Slice           |    .
         .       |  (SLOs e.g.  B/W > x bps, Delay < y ms)  |    .
       SDPm O....|                                          |....O SDPn
                 |------------------------------------------|

       == == == == == == == == == == == == == == == == == == == == == ==

                         .--.               .--.
               [EP1]    (    )- .          (    )- .    [EP2]
                 .    .' IETF    '  SLO  .' IETF    '     .
                 .   (  Network-1 ) ... (  Network-p )    .
                     `-----------'      `-----------'
               [EPm]                                    [EPn]

       Legend
         SDP: IETF Network Slice Service Demarcation Point
         EP:  Serivce/tunnel/path Endpoint used to realize the
              IETF Network Slice


                        Figure 4: IETF Network Slice

   Figure 4 illustrates a case where an IETF Network Slice provides
   connectivity between a set of IETF Network Slice Service Demarcation
   Point (SDP) pairs with specific SLOs (e.g., guaranteed minimum
   bandwidth of x bps and guaranteed delay of no more than y ms).  The
   IETF Network Slice endpoints are mapped to the service/tunnel/path
   Endpoints (EPs) in the underlay network.  Also, the SDPs in the same
   IETF Network Slice may belong to the same or different address
   spaces.

   IETF Network Slice structure fits into a broader concept of end-to-
   end network slices.  A network operator may be responsible for
   delivering services over a number of technologies (such as radio
   networks) and for providing specific and fine-grained services (such
   as CCTV feed or High definition realtime traffic data).  That
   operator may need to combine slices of various networks to produce an
   end-to-end network service.  Each of these networks may include
   multiple physical or virtual nodes and may also provide network
   functions beyond simply carrying of technology-specific protocol data
   units.  An end-to-end network slice is defined by the 3GPP as a
   complete logical network that provides a service in its entirety with
   a specific assurance to the customer [TS23501].





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   An end-to-end network slice may be composed from other network slices
   that include IETF Network Slices.  This composition may include the
   hierarchical (or recursive) use of underlying network slices and the
   sequential (or stitched) combination of slices of different networks.

6.  Realizing IETF Network Slices

   Realization of IETF Network Slices is out of scope of this document.
   It is a mapping of the definition of the IETF Network Slice to the
   underlying infrastructure and is necessarily technology-specific and
   achieved by the NSC over the Network Configuration Interface.
   However, this section provides an overview of the components and
   processes involved in realizing an IETF Network Slice.

   The realization can be achieved in a form of either physical or
   logical connectivity using VPNs, virtual networks (VNs), or a variety
   of tunneling technologies such as Segment Routing, MPLS, etc.
   Accordingly, SDPs may be realized as physical or logical service or
   network functions.

6.1.  Architecture to Realize IETF Network Slices

   The architecture described in this section is deliberately at a high
   level.  It is not intended to be prescriptive: implementations and
   technical solutions may vary freely.  However, this approach provides
   a common framework that other documents may reference in order to
   facilitate a shared understanding of the work.

   Figure 5 shows the architectural components of a network managed to
   provide IETF Network Slices.  The customer's view is of individual
   IETF Network Slices with their CEs, PEs, and connectivity constructs.
   Requests for IETF Network Slices are delivered to the NSC.

   The figure shows, without loss of generality, the CEs, ACs, and PEs,
   that exist in the network.  The SDPs are not shown and can be placed
   in any of the ways described in Section 4.2.















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                          --      --      --
                         |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    >>>>>>>>>>>>>>>  Grouping/Mapping v     v           View
        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  |    ----------------------------------------------
      |Controller|   ( |PE|.....-.....|PE|......    |PE|.......|PE| )
      |          |  (   --     |P|     --      :-...:--     -..:--   )
       ----------  (    :       -:.............|P|.........|P|        )
           v       (    -......................:-:..-       -         )
            >>>>>>> (  |P|.........................|P|......:        )
        Program the  (  -                           -               )
          Network     ----------------------------------------------


              Figure 5: Architecture of an IETF Network Slice





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   The network itself (at the bottom of the figure) comprises an
   underlay network.  This could be a physical network, but may be a
   virtual network.  The underlay network is provisioned through network
   controllers.

   The underlay network may optionally be filtered or customized by the
   network operator to produce a number of network topologies that we
   call Filter Topologies.  Customization is just a way of selecting
   specific resources (e.g., nodes and links) from the underlay network
   according to their capabilities and connectivity in the underlay
   network.  These actions are configuration options or operator
   policies.  The resulting topologies can be used as candidates to host
   IETF Network Slices and provide a useful way for the network operator
   to know in advance that all of the resources they are using to plan
   an IETF Network Slice would be able to meet specific SLOs and SLEs.
   The creation of a Filter Topology could be an offline planning
   activity or could be performed dynamically as new demands arise.  The
   use of Filter Topologies is entirely optional in the architecture,
   and IETF Network Slices could be hosted directly on the underlay
   network.

   Recall that an IETF Network Slice is a service requested by /
   provided for the customer.  The IETF Network Slice service is
   expressed in terms of one or more connectivity constructs.  An
   implementation or operator is free to limit the number of
   connectivity constructs in a slice to exactly one.  Each connectivity
   construct is associated within the IETF Network Slice service request
   with a set of SLOs and SLEs.  The set of SLOs and SLEs does not need
   to be the same for every connectivity construct in the slice, but an
   implementation or operator is free to require that all connectivity
   constructs in a slice have the same set of SLOs and SLEs.

   One or more connectivity constructs from one or more slices are
   mapped to a set of network resources called a Network Resource
   Partition (NRP).  A single connectivity construct is mapped to only
   one NRP (that is, the relationship is many to one).  An NRP may be
   chosen to support a specific connectivity construct because of its
   ability to support a specific set of SLOs and SLEs, or its ability to
   support particular connectivity types, or for any administrative or
   operational reason.  An implementation or operator is free to map
   each connectivity construct to a separate NRP, although there may be
   scaling implications depending on the solution implemented.  Thus,
   the connectivity constructs in one slice may be mapped to one or more
   NRPs.  By implication from the above, an implementation or operator
   is free to map all the connectivity constructs in a slice to a single
   NRP, and to not share that NRP with connectivity constructs from
   another slice.




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   An NRP is simply a collection of resources identified in the underlay
   network.  The process of determining the NRP may be made easier if
   the underlay network topology is first filtered into a Filter
   Topology in order to be aware of the subset of network resources that
   are suitable for specific NRPs, but this is optional.

   The steps described here can be applied in a variety of orders
   according to implementation and deployment preferences.  Furthermore,
   the steps may be iterative so that the components are continually
   refined and modified as network conditions change and as service
   requests are received or relinquished, and even the underlay network
   could be extended if necessary to meet the customers' demands.

6.2.  Procedures to Realize IETF Network Slices

   There are a number of different technologies that can be used in the
   underlay, including physical connections, MPLS, time-sensitive
   networking (TSN), Flex-E, etc.

   An IETF Network Slice can be realized in a network, using specific
   underlying technology or technologies.  The creation of a new IETF
   Network Slice will be realized with following steps:

   *  The NSC exposes the network slicing capabilities that it offers
      for the network it manages.

   *  The customer may issue a request to determine whether a specific
      IETF Network Slice could be supported by the network.  The NSC may
      respond indicating a simple yes or no, and may supplement a
      negative response with information about what it could support
      were the customer to change some requirements.

   *  The customer requests an IETF Network Slice.  The NSC may respond
      that the slice has or has not been created, and may supplement a
      negative response with information about what it could support
      were the customer to change some requirements.

   *  When processing a customer request for an IETF Network Slice, the
      NSC maps the request to the network capabilities and applies
      provider policies before creating or supplementing the resource
      partition.

   Regardless of how IETF Network Slice is realized in the network
   (i.e., using tunnels of different types), the definition of the IETF
   Network Slice does not change at all.  The only difference is how the
   slice is realized.  The following sections briefly introduce how some
   existing architectural approaches can be applied to realize IETF
   Network Slices.



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6.3.  Applicability of ACTN to IETF Network Slices

   Abstraction and Control of TE Networks (ACTN - [RFC8453]) is a
   management architecture and toolkit used to create virtual networks
   (VNs) on top of a TE underlay network.  The VNs can be presented to
   customers for them to operate as private networks.

   In many ways, the function of ACTN is similar to IETF network
   slicing.  Customer requests for connectivity-based overlay services
   are mapped to dedicated or shared resources in the underlay network
   in a way that meets customer guarantees for service level objectives
   and for separation from other customers' traffic.  [RFC8453] the
   function of ACTN as collecting resources to establish a logically
   dedicated virtual network over one or more TE networks.  Thus, in the
   case of a TE-enabled underlying network, the ACTN VN can be used as a
   basis to realize an IETF network slicing.

   While the ACTN framework is a generic VN framework that can be used
   for VN services beyond the IETF Network Slice, it also a suitable
   basis for delivering and realizing IETF Network Slices.

   Further discussion of the applicability of ACTN to IETF Network
   Slices including a discussion of the relevant YANG models can be
   found in [I-D.king-teas-applicability-actn-slicing].

6.4.  Applicability of Enhanced VPNs to IETF Network Slices

   An enhanced VPN (VPN+) is designed to support the needs of new
   applications, particularly applications that are associated with 5G
   services, by utilizing an approach that is based on existing VPN and
   TE technologies and adds characteristics that specific services
   require over and above VPNs as they have previously been specified.

   An enhanced VPN can be used to provide enhanced connectivity services
   between customer sites and can be used to create the infrastructure
   to underpin a network slicing service.

   It is envisaged that enhanced VPNs will be delivered using a
   combination of existing, modified, and new networking technologies.

   [I-D.ietf-teas-enhanced-vpn] describes the framework for Enhanced
   Virtual Private Network (VPN+) services.









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6.5.  Network Slicing and Aggregation in IP/MPLS Networks

   Network slicing provides the ability to partition a physical network
   into multiple isolated logical networks of varying sizes, structures,
   and functions so that each slice can be dedicated to specific
   services or customers.

   Many approaches are currently being worked on to support IETF Network
   Slices in IP and MPLS networks with or without the use of Segment
   Routing.  Most of these approaches utilize a way of marking packets
   so that network nodes can apply specific routing and forwarding
   behaviors to packets that belong to different IETF Network Slices.
   Different mechanisms for marking packets have been proposed
   (including using MPLS labels and Segment Routing segment IDs) and
   those mechanisms are agnostic to the path control technology used
   within the underlay network.

   These approaches are also sensitive to the scaling concerns of
   supporting a large number of IETF Network Slices within a single IP
   or MPLS network, and so offer ways to aggregate the connectivity
   constructs of slices (or whole slices) so that the packet markings
   indicate an aggregate or grouping where all of the packets are
   subject to the same routing and forwarding behavior.

   At this stage, it is inappropriate to mention any of these proposed
   solutions that are currently work in progress and not yet adopted as
   IETF work.

7.  Isolation in IETF Network Slices

7.1.  Isolation as a Service Requirement

   An IETF Network Slice customer may request that the IETF Network
   Slice delivered to them is delivered such that changes to other IETF
   Network Slices or services do not have any negative impact on the
   delivery of the IETF Network Slice.  The IETF Network Slice customer
   may specify the degree to which their IETF Network Slice is
   unaffected by changes in the provider network or by the behavior of
   other IETF Network Slice customers.  The customer may express this
   via an SLE it agrees with the provider.  This concept is termed
   'isolation'










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7.2.  Isolation in IETF Network Slice Realization

   Isolation may be achieved in the underlying network by various forms
   of resource partitioning ranging from dedicated allocation of
   resources for a specific IETF Network Slice, to sharing of resources
   with safeguards.  For example, traffic separation between different
   IETF Network Slices may be achieved using VPN technologies, such as
   L3VPN, L2VPN, EVPN, etc.  Interference avoidance may be achieved by
   network capacity planning, allocating dedicated network resources,
   traffic policing or shaping, prioritizing in using shared network
   resources, etc.  Finally, service continuity may be ensured by
   reserving backup paths for critical traffic, dedicating specific
   network resources for a selected number of IETF Network Slices.

8.  Management Considerations

   IETF Network Slice realization needs to be instrumented in order to
   track how it is working, and it might be necessary to modify the IETF
   Network Slice as requirements change.  Dynamic reconfiguration might
   be needed.

9.  Security Considerations

   This document specifies terminology and has no direct effect on the
   security of implementations or deployments.  In this section, a few
   of the security aspects are identified.

   *  Conformance to security constraints: Specific security requests
      from customer defined IETF Network Slices will be mapped to their
      realization in the underlay networks.  It will be required by
      underlay networks to have capabilities to conform to customer's
      requests as some aspects of security may be expressed in SLEs.

   *  IETF NSC authentication: Underlying networks need to be protected
      against the attacks from an adversary NSC as they can destabilize
      overall network operations.  It is particularly critical since an
      IETF Network Slice may span across different networks, therefore,
      IETF NSC should have strong authentication with each those
      networks.  Furthermore, both the IETF Network Slice Service
      Interface and the Network Configuration Interface need to be
      secured.

   *  Specific isolation criteria: The nature of conformance to
      isolation requests means that it should not be possible to attack
      an IETF Network Slice service by varying the traffic on other
      services or slices carried by the same underlay network.  In
      general, isolation is expected to strengthen the IETF Network
      Slice security.



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   *  Data Integrity of an IETF Network Slice: A customer wanting to
      secure their data and keep it private will be responsible for
      applying appropriate security measures to their traffic and not
      depending on the network operator that provides the IETF Network
      Slice.  It is expected that for data integrity, a customer is
      responsible for end-to-end encryption of its own traffic.

   Note: see NGMN document [NGMN_SEC] on 5G network slice security for
   discussion relevant to this section.

   IETF Network Slices might use underlying virtualized networking.  All
   types of virtual networking require special consideration to be given
   to the separation of traffic between distinct virtual networks, as
   well as some degree of protection from effects of traffic use of
   underlying network (and other) resources from other virtual networks
   sharing those resources.

   For example, if a service requires a specific upper bound of latency,
   then that service can be degraded by added delay in transmission of
   service packets through the activities of another service or
   application using the same resources.

   Similarly, in a network with virtual functions, noticeably impeding
   access to a function used by another IETF Network Slice (for
   instance, compute resources) can be just as service degrading as
   delaying physical transmission of associated packet in the network.

   While a IETF Network Slice might include encryption and other
   security features as part of the service, customers might be well
   advised to take responsibility for their own security needs, possibly
   by encrypting traffic before hand-off to a service provider.

10.  Privacy Considerations

   Privacy of IETF Network Slice service customers must be preserved.
   It should not be possible for one IETF Network Slice customer to
   discover the presence of other customers, nor should sites that are
   members of one IETF Network Slice be visible outside the context of
   that IETF Network Slice.

   In this sense, it is of paramount importance that the system use the
   privacy protection mechanism defined for the specific underlying
   technologies used, including in particular those mechanisms designed
   to preclude acquiring identifying information associated with any
   IETF Network Slice customer.






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11.  IANA Considerations

   This document makes no requests for IANA action.

12.  Informative References

   [HIPAA]    HHS, "Health Insurance Portability and Accountability Act
              - The Security Rule", February 2003,
              <https://www.hhs.gov/hipaa/for-professionals/security/
              index.html>.

   [I-D.ietf-opsawg-sap]
              Boucadair, M., Dios, O. G. D., Barguil, S., Wu, Q., and V.
              Lopez, "A Network YANG Model for Service Attachment Points
              (SAPs)", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-sap-02, 22 February 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              sap-02>.

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Network (VPN+)
              Services", Work in Progress, Internet-Draft, draft-ietf-
              teas-enhanced-vpn-09, 25 October 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              enhanced-vpn-09>.

   [I-D.king-teas-applicability-actn-slicing]
              King, D., Drake, J., Zheng, H., and A. Farrel,
              "Applicability of Abstraction and Control of Traffic
              Engineered Networks (ACTN) to Network Slicing", Work in
              Progress, Internet-Draft, draft-king-teas-applicability-
              actn-slicing-10, 31 March 2021,
              <https://datatracker.ietf.org/doc/html/draft-king-teas-
              applicability-actn-slicing-10>.

   [I-D.openconfig-rtgwg-gnmi-spec]
              Shakir, R., Shaikh, A., Borman, P., Hines, M., Lebsack,
              C., and C. Morrow, "gRPC Network Management Interface
              (gNMI)", Work in Progress, Internet-Draft, draft-
              openconfig-rtgwg-gnmi-spec-01, 5 March 2018,
              <https://datatracker.ietf.org/doc/html/draft-openconfig-
              rtgwg-gnmi-spec-01>.

   [MACsec]   IEEE, "IEEE Standard for Local and metropolitan area
              networks - Media Access Control (MAC) Security", 2018,
              <https://1.ieee802.org/security/802-1ae>.




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   [NGMN-NS-Concept]
              NGMN Alliance, "Description of Network Slicing Concept",
              https://www.ngmn.org/uploads/
              media/161010_NGMN_Network_Slicing_framework_v1.0.8.pdf ,
              2016.

   [NGMN_SEC] NGMN Alliance, "NGMN 5G Security - Network Slicing", April
              2016, <https://www.ngmn.org/wp-content/uploads/Publication
              s/2016/160429_NGMN_5G_Security_Network_Slicing_v1_0.pdf>.

   [PCI]      PCI Security Standards Council, "PCI DSS", May 2018,
              <https://www.pcisecuritystandards.org>.

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681,
              September 1999, <https://www.rfc-editor.org/info/rfc2681>.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              DOI 10.17487/RFC3022, January 2001,
              <https://www.rfc-editor.org/info/rfc3022>.

   [RFC3135]  Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
              Shelby, "Performance Enhancing Proxies Intended to
              Mitigate Link-Related Degradations", RFC 3135,
              DOI 10.17487/RFC3135, June 2001,
              <https://www.rfc-editor.org/info/rfc3135>.

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              DOI 10.17487/RFC3393, November 2002,
              <https://www.rfc-editor.org/info/rfc3393>.

   [RFC4208]  Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter,
              "Generalized Multiprotocol Label Switching (GMPLS) User-
              Network Interface (UNI): Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Support for the Overlay
              Model", RFC 4208, DOI 10.17487/RFC4208, October 2005,
              <https://www.rfc-editor.org/info/rfc4208>.

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

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.




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   [RFC4397]  Bryskin, I. and A. Farrel, "A Lexicography for the
              Interpretation of Generalized Multiprotocol Label
              Switching (GMPLS) Terminology within the Context of the
              ITU-T's Automatically Switched Optical Network (ASON)
              Architecture", RFC 4397, DOI 10.17487/RFC4397, February
              2006, <https://www.rfc-editor.org/info/rfc4397>.

   [RFC5212]  Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
              M., and D. Brungard, "Requirements for GMPLS-Based Multi-
              Region and Multi-Layer Networks (MRN/MLN)", RFC 5212,
              DOI 10.17487/RFC5212, July 2008,
              <https://www.rfc-editor.org/info/rfc5212>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <https://www.rfc-editor.org/info/rfc6146>.

   [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>.

   [RFC7679]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Delay Metric for IP Performance Metrics
              (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
              2016, <https://www.rfc-editor.org/info/rfc7679>.

   [RFC7680]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Loss Metric for IP Performance Metrics
              (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
              2016, <https://www.rfc-editor.org/info/rfc7680>.









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   [RFC7926]  Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
              Ceccarelli, D., and X. Zhang, "Problem Statement and
              Architecture for Information Exchange between
              Interconnected Traffic-Engineered Networks", BCP 206,
              RFC 7926, DOI 10.17487/RFC7926, July 2016,
              <https://www.rfc-editor.org/info/rfc7926>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [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>.

   [RFC8309]  Wu, Q., Liu, W., and A. Farrel, "Service Models
              Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
              <https://www.rfc-editor.org/info/rfc8309>.

   [RFC8453]  Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
              Abstraction and Control of TE Networks (ACTN)", RFC 8453,
              DOI 10.17487/RFC8453, August 2018,
              <https://www.rfc-editor.org/info/rfc8453>.

   [RFC8454]  Lee, Y., Belotti, S., Dhody, D., Ceccarelli, D., and B.
              Yoon, "Information Model for Abstraction and Control of TE
              Networks (ACTN)", RFC 8454, DOI 10.17487/RFC8454,
              September 2018, <https://www.rfc-editor.org/info/rfc8454>.

   [TS23501]  3GPP, "System architecture for the 5G System (5GS)",
              3GPP TS 23.501, 2019.

   [TS28530]  3GPP, "Management and orchestration; Concepts, use cases
              and requirements", 3GPP TS 28.530, 2019.

   [TS33.210] 3GPP, "3G security; Network Domain Security (NDS); IP
              network layer security (Release 14).", December 2016,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=2279>.

Acknowledgments

   The entire TEAS Network Slicing design team and everyone
   participating in related discussions has contributed to this
   document.  Some text fragments in the document have been copied from
   the [I-D.ietf-teas-enhanced-vpn], for which we are grateful.





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   Significant contributions to this document were gratefully received
   from the contributing authors listed in the "Contributors" section.
   In addition we would like to also thank those others who have
   attended one or more of the design team meetings, including the
   following people not listed elsewhere:

   *  Aihua Guo

   *  Bo Wu

   *  Greg Mirsky

   *  Lou Berger

   *  Rakesh Gandhi

   *  Ran Chen

   *  Sergio Belotti

   *  Stewart Bryant

   *  Tomonobu Niwa

   *  Xuesong Geng

   Further useful comments were received from Daniele Ceccarelli, Uma
   Chunduri, Pavan Beeram, Tarek Saad, Kenichi Ogaki, Oscar Gonzalez de
   Dios, Xiaobing Niu, Dan Voyer, Igor Bryskin, Luay Jalil, Joel
   Halpern, and John Scudder.

   This work is partially supported by the European Commission under
   Horizon 2020 grant agreement number 101015857 Secured autonomic
   traffic management for a Tera of SDN flows (Teraflow).

Contributors

   The following authors contributed significantly to this document:













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      Eric Gray (The original editor of the foundation documents)
      Independent
      Email: ewgray@graiymage.com

      Jari Arkko
      Ericsson
      Email: jari.arkko@piuha.net

      Mohamed Boucadair
      Orange
      Email: mohamed.boucadair@orange.com

      Dhruv Dhody
      Huawei, India
      Email: dhruv.ietf@gmail.com

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

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


Authors' Addresses

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


   John Drake
   Juniper Networks
   United States of America
   Email: jdrake@juniper.net


   Reza Rokui
   Ciena
   Email: rrokui@ciena.com


   Shunsuke Homma
   NTT
   Japan
   Email: shunsuke.homma.ietf@gmail.com



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   Kiran Makhijani
   Futurewei
   United States of America
   Email: kiranm@futurewei.com


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


   Jeff Tantsura
   Microsoft Inc.
   Email: jefftant.ietf@gmail.com




































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