Framework for IETF Network Slices
draft-ietf-teas-ietf-network-slices-02

Document Type Active Internet-Draft (teas WG)
Authors Adrian Farrel  , Eric Gray  , John Drake  , Reza Rokui  , Shunsuke Homma  , Kiran Makhijani  , Luis Contreras  , Jeff Tantsura 
Last updated 2021-05-04
Replaces draft-ietf-teas-ietf-network-slice-framework, draft-ietf-teas-ietf-network-slice-definition
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Network Working Group                                     A. Farrel, Ed.
Internet-Draft                                        Old Dog Consulting
Intended status: Informational                                   E. Gray
Expires: November 5, 2021                                    Independent
                                                                J. Drake
                                                        Juniper Networks
                                                                R. Rokui
                                                                   Nokia
                                                                S. Homma
                                                                     NTT
                                                            K. Makhijani
                                                               Futurewei
                                                           LM. Contreras
                                                              Telefonica
                                                             J. Tantsura
                                                        Juniper Networks
                                                             May 4, 2021

                   Framework for IETF Network Slices
                 draft-ietf-teas-ietf-network-slices-02

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

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   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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

   This Internet-Draft will expire on November 5, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terms and Abbreviations . . . . . . . . . . . . . . . . . . .   5
   3.  IETF Network Slice Objectives . . . . . . . . . . . . . . . .   6
     3.1.  Definition and Scope of IETF Network Slice  . . . . . . .   6
   4.  IETF Network Slice System Characteristics . . . . . . . . . .   7
     4.1.  Objectives for IETF Network Slices  . . . . . . . . . . .   7
       4.1.1.  Service Level Objectives  . . . . . . . . . . . . . .   8
       4.1.2.  Service Level Expectations  . . . . . . . . . . . . .   9
     4.2.  IETF Network Slice Endpoints  . . . . . . . . . . . . . .  12
       4.2.1.  IETF Network Slice Connectivity Types . . . . . . . .  13
     4.3.  IETF Network Slice Decomposition  . . . . . . . . . . . .  13
   5.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  IETF Network Slice Stakeholders . . . . . . . . . . . . .  14
     5.2.  Expressing Connectivity Intents . . . . . . . . . . . . .  15
     5.3.  IETF Network Slice Controller (NSC) . . . . . . . . . . .  17
       5.3.1.  IETF Network Slice Controller Interfaces  . . . . . .  18
       5.3.2.  Northbound Interface (NBI)  . . . . . . . . . . . . .  19
     5.4.  IETF Network Slice Structure  . . . . . . . . . . . . . .  20
   6.  Realizing IETF Network Slices . . . . . . . . . . . . . . . .  21
     6.1.  Procedures to Realize IETF Network Slices . . . . . . . .  21

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     6.2.  Applicability of ACTN to IETF Network Slices  . . . . . .  22
     6.3.  Applicability of Enhanced VPNs to IETF Network Slices . .  22
     6.4.  Network Slicing and Slice Aggregation in IP/MPLS Networks  23
   7.  Isolation in IETF Network Slices  . . . . . . . . . . . . . .  23
     7.1.  Isolation as a Service Requirement  . . . . . . . . . . .  23
     7.2.  Isolation in IETF Network Slice Realization . . . . . . .  24
   8.  Management Considerations . . . . . . . . . . . . . . . . . .  24
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  25
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   12. Informative References  . . . . . . . . . . . . . . . . . . .  26
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  30
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

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 over a shared network infrastructure.
   Services that might benefit from IETF Network Slices include, but are
   not limited to:

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

   o  Network wholesale services

   o  Network infrastructure sharing among operators

   o  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 network infrastructure.  A
   request for an IETF Network Slice is technology-agnostic so as to
   allow a customer to describe their network connectivity objectives in
   a common format, independent of the underlying technologies used.

   This document also provides a framework for discussing IETF Network
   Slices.  This framework is intended as a structure for discussing

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   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], [TS28530],
   and [BBF-SD406]).  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 traditional 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 terms and abbreviations used in this document are listed below.

   o  NBI: NorthBound Interface

   o  NSC: Network Slice Controller

   o  NSE: Network Slice Endpoint

   o  SBI: SouthBound Interface

   o  SLA: Service Level Agreement

   o  SLI: Service Level Indicator

   o  SLO: Service Level Objective

   The above terminology is defined in greater details in the remainder
   of this document.

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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 in accordance with specified characteristics.

3.1.  Definition and Scope of IETF Network Slice

   The definition of a network slice in IETF context is as follows:

   An IETF Network Slice is a logical network topology connecting a
   number of endpoints using a set of shared or dedicated network
   resources that are used to satisfy specific Service Level Objectives
   (SLOs).

   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.  IETF Network Slices are independent of the
   underlying infrastructure connectivity and technologies used.  This
   is to allow an IETF Network Slice customer to describe their network
   connectivity and relevant objectives in a common format, independent
   of the underlying technologies used.

   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 is technology-agnostic, and the means for IETF
   Network Slice realization can be chosen depending on several factors
   such as: service requirements, specifications or capabilities of
   underlying infrastructure.  The structure and different
   characteristics of IETF Network Slices are described in the following
   sections.

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   Term "Slice" refers to a set of characteristics and behaviours that
   separate one type of user-traffic from another.  IETF Network Slice
   assumes that an underlying 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 to
   all of the traffic in the slice or to specific flows.

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:

   o  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.

   o  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.

   o  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.

   o  A Service Level Agreement (SLA) is an explicit or implicit
      contract between the customer of an IETF Network Slice and the
      provider of the slice.  The SLA is expressed in terms of a set of
      SLOs and SLEs that are to be applied to the connections between
      the service endpoints, and may include commercial terms as well as
      the consequences of missing/violating the SLOs they contain.

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4.1.1.  Service Level Objectives

   SLOs define a set of network attributes and characteristics that
   describe an IETF Network Slice.  SLOs do not describe how the IETF
   Network Slices are 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 can have one or more SLOs associated with it.
   The SLOs are combined in an SLA.  The SLOs are defined for sets of
   two or more endpoints and apply to specific directions of traffic
   flow.  That is, they apply to specific source endpoints and specific
   connections between endpoints within the set of endpoints and
   connections in the IETF Network Slice.

   SLOs define a set of measurable network attributes and
   characteristics that describe an IETF Network Slice service.  SLOs do
   not describe how the IETF network slices are 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 can have one or more
   SLOs associated with it.  The SLOs are combined with Service Level
   Expectations in an SLA.

   An IETF network slice service may include multiple connection
   constructs that associate sets of endpoints.  SLOs apply to sets of
   two or more endpoints and apply to specific directions of traffic
   flow.  That is, they apply to a specific source endpoint and the
   connection to specific destination endpoints.

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'.

   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

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         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).

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

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   cannot usually be determined 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.  An IETF network slice service can have one or more SLEs
   associated with it.  The SLEs are combined with SLOs in an SLA.

   An IETF Network Slice service may include multiple connection
   constructs that associate sets of endpoints.  SLEs apply to sets of
   two or more endpoints and apply to specific directions of traffic
   flow.  That is, they apply to a specific source endpoint and the
   connection to specific destination endpoints.  However, being more
   general in nature, 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 endpoints
         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 endpoints 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.

         Please see further discussion on security in Section 9.

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      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 Service slice,
         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 endpoints should use different network resources
         from the traffic between another set of endpoints.  This might

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         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).

4.2.  IETF Network Slice Endpoints

   As noted in Section 3.1, an IETF Network Slice describes connectivity
   between multiple endpoints across the underlying network.  These
   connectivity types are: point-to-point, point-to-multipoint,
   multipoint-to-point, multipoint-to-point, or multipoint-to-
   multipoint.

   Figure 1 shows an IETF Network Slice along with its Network Slice
   Endpoints (NSEs).

   The characteristics of IETF NSEs are as follows:

   o  The IETF NSE are conceptual points of connection to IETF network
      slice.  As such, they serve as the IETF Network Slice ingress/
      egress points.

   o  Each endpoint could map to a device, application or a network
      function.  A non-exhaustive list of devices, applications or
      network functions might include but not limited to: routers,
      switches, firewalls, WAN, 4G/5G RAN nodes, 4G/5G Core nodes,
      application acceleration, Deep Packet Inspection (DPI), server
      load balancers, NAT44 [RFC3022], NAT64 [RFC6146], HTTP header
      enrichment functions, and TCP optimizers.

   o  An NSE should be identified by a unique ID in the context of an
      IETF Network Slice customer.

   o  In addition to an identifier, each NSE should contain a subset of
      attributes such as IPv4/IPv6 addresses, encapsulation type (i.e.,
      VLAN tag, MPLS Label etc.), interface/port numbers, node ID etc.

   o  A combination of NSE unique ID and NSE attributes defines an NSE
      in the context of the IETF Network Slice Controller (NSC).

   o  During the realization of the IETF Network Slice, in addition to
      SLOs, all or subset of IETF NSE attributes will be utilized by the
      IETF NSC to find the optimal realization in the IETF network.

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   o  Similarly to IETF Network Slices, the IETF Network Slice Endpoints
      are logical entities that are mapped to services/tunnels/paths
      endpoints in IETF Network Slice during its initialization and
      realization.

   Note that there are various IETF TE terms such as access points (AP)
   defined in [RFC8453], Termination Point (TP) defined in [RFC8345],
   and Link Termination Point (LTP) defined in [RFC8795] which are
   tightly coupled with TE network type and various realization
   techniques.  At the time of realization of the IETF Network Slice,
   the NSE could be mapped to one or more of these based on the network
   slice realization technique in use.

                        |----------------------------------|
                   NSE1 |                                  | NSE2
                  O.....|                                  |.....O
                    .   |                                  |  .
                    .   |                                  |  .
                    .   |                                  |  .
                        |                                  |
                   NSEm |                                  | NSEn
                  O.....|                                  |.....O
                        |                                  |
                        |----------------------------------|

                  <------------ IETF Network Slice -------------->
                           between endpoints NSE1 to NSEn

            Legend:
                 NSE: IETF Network Slice Endpoint
                   O: Represents IETF Network Slice Endpoints

              Figure 1: An IETF Network Slice Endpoints (NSE)

4.2.1.  IETF Network Slice Connectivity Types

   The IETF Network Slice connection types can be point to point (P2P),
   point to multipoint (P2MP), multi-point to point (MP2P), or multi-
   point to multi-point (MP2MP).  They will requested by the higher
   level operation system.

4.3.  IETF Network Slice Decomposition

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

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   o  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.

   o  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.

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.

   Customer:  A customer is the requester of an IETF Network Slice.
      Customers may request monitoring of SLOs.  A customer may manage
      the IETF Network Slice service directly by interfacing with the
      IETF NSC or indirectly through an orchestrator.

   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):  It realizes an IETF Network
      Slice in the underlying network, maintains and monitors the run-
      time state of resources and topologies associated with it.  A
      well-defined interface is needed between different types of IETF
      NSCs and different types of orchestrators.  An IETF Network Slice
      operator (or slice operator for short) manages one or more IETF
      Network Slices using the IETF NSCs.

   Network Controller:  is a form of network infrastructure controller
      that offers network resources to the NSC to realize a particular

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      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

   The NSC northbound interface (NBI) can be used to communicate between
   IETF Network Slice users (or customers) and the NSC.

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

   Using the NBI, 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:

   o  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;

   o  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
      NSC NBI, even if that information is available);

   o  Scalability: customers do not need to know any information beyond
      that which is exposed via the NBI.

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

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   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 IETF
   documents and are widely supported.  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.

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

   For instance:

   o  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.

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

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

   o  SNMP ([RFC3417], [RFC3412] and [RFC3414] uses binary encoding
      (ASN.1).

   o  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;
      Structure of Management Information (SMI) [RFC2578] may be used to
      define Management Information Base (MIB) modules for SNMP, using
      an adapted subset of OSI's Abstract Syntax Notation One (ASN.1,
      1988).

   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.

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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.

   An NSC northbound interface (NBI) 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 NBI are not in scope for this document.

   The controller provides the following functions:

   o  Provides a technology-agnostic NBI for creation/modification/
      deletion of the IETF Network Slices.  The API exposed by this NBI
      communicates the endpoints 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.

   o  Determines an abstract topology connecting the endpoints of the
      IETF Network Slice that meets criteria specified via the NBI.  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.

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

      *  map technology-agnostic NBI request to technology-specific SBIs

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

   o  Via an SBI, 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.

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   o  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 NBI.  The
      NSC NBI 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 user is served by the IETF Network Slice
   Controller (NSC), as follows:

   o  The NSC takes requests from a management system or other
      application, which are then communicated via an NBI.  This
      interface carries data objects the IETF Network Slice user
      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 user's perspective; it
      may be as simple as a list of mutually (and symmetrically)
      connected end points, or it may be complicated by details of
      connection asymmetry, per-connection SLO requirements, etc.

   o  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.

   o  The NSC maintains a record of the mapping from user 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).

   NSC Northbound Interface (NBI):  The NSC Northbound Interface is an
      interface between a customer's higher level operation system
      (e.g., a network slice orchestrator) and the NSC.  It is a
      technology agnostic interface.  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

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      NSC can use the interface to report the operational state of an
      IETF Network Slice to the customer.

   NSC Southbound Interface (SBI):  The NSC Southbound 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.

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

           Figure 2: Interface of IETF Network Slice Controller

5.3.2.  Northbound Interface (NBI)

   The IETF Network Slice Controller provides a Northbound Interface
   (NBI) 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 NBI complements various IETF services, tunnels, path models by
   providing an abstract layer on top of these models.

   The NBI 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 NBI 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

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   well-defined data model, and should include at least endpoint and
   connectivity information, SLO specification, and status information.

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

5.4.  IETF Network Slice Structure

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

                 |------------------------------------------|
       NSE1 O....|                                          |....O NSE2
         .       |                                          |    .
         .       |             IETF Network Slice           |    .
         .       |  (SLOs e.g.  B/W > x bps, Delay < y ms)  |    .
       NSEm O....|                                          |....O NSEn
                 |------------------------------------------|

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

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

       Legend
         NSE: IETF Network Slice Endpoints
         EP:  Serivce/tunnels/path Endpoints used to realize the
              IETF Network Slice

                       Figure 3: IETF Network Slice

   Figure 3 illustrates a case where an IETF Network Slice provides
   connectivity between a set of IEFT network slice endpoints (NSE)
   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 underlay IETF Network Slice Endpoints
   (NEPs).  Also, the IETF NSEs on 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

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   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].

   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 SBI.

   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, endpoints (NSEs) may be realized as physical or logical
   service or network functions.

6.1.  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 initiated with following three steps:

   o  Step 1: A higher level system requests connections with specific
      characteristics via the NBI.

   o  Step 2: This request will be processed by an IETF NSC which
      specifies a mapping between northbound request to any IETF
      Services, Tunnels, and paths models.

   o  Step 3: A series of requests for creation of services, tunnels and
      paths will be sent to the network to realize the transport slice.

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   It is very clear that, 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 some existing architectural approaches that can be
   applied to realize IETF Network Slices.

6.2.  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 traffic engineering (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].

6.3.  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
   Traffic Engineering (TE) technologies and adds characteristics that
   specific services require over and above traditional VPNs.

   An enhanced VPN can be used to provide enhanced connectivity services
   between customer sites (a concept similar to an IETF Network Slice)
   and can be used to create the infrastructure to underpin network
   slicing.

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

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

6.4.  Network Slicing and Slice 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 Rouing 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 slices so that
   the packet markings indicate an aggregate or grouping of IETF Network
   Slices 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.

   o  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 SLOs.

   o  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 SBI and NBI need to be secured.

   o  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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   o  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

   [BBF-SD406]
              Broadband Forum, "End-to-end network slicing", BBF SD-406,
              <https://wiki.broadband-forum.org/display/BBF/SD-406+End-
              to-End+Network+Slicing>.

   [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-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Network (VPN+)
              Services", draft-ietf-teas-enhanced-vpn-07 (work in
              progress), February 2021.

   [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", draft-
              king-teas-applicability-actn-slicing-10 (work in
              progress), March 2021.

   [I-D.openconfig-rtgwg-gnmi-spec]
              Shakir, R., Shaikh, A., Borman, P., Hines, M., Lebsack,
              C., and C. Morrow, "gRPC Network Management Interface
              (gNMI)", draft-openconfig-rtgwg-gnmi-spec-01 (work in
              progress), March 2018.

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

   [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.

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   [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>.

   [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578,
              DOI 10.17487/RFC2578, April 1999,
              <https://www.rfc-editor.org/info/rfc2578>.

   [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>.

   [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>.

   [RFC3412]  Case, J., Harrington, D., Presuhn, R., and B. Wijnen,
              "Message Processing and Dispatching for the Simple Network
              Management Protocol (SNMP)", STD 62, RFC 3412,
              DOI 10.17487/RFC3412, December 2002,
              <https://www.rfc-editor.org/info/rfc3412>.

   [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414,
              DOI 10.17487/RFC3414, December 2002,
              <https://www.rfc-editor.org/info/rfc3414>.

   [RFC3417]  Presuhn, R., Ed., "Transport Mappings for the Simple
              Network Management Protocol (SNMP)", STD 62, RFC 3417,
              DOI 10.17487/RFC3417, December 2002,
              <https://www.rfc-editor.org/info/rfc3417>.

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   [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>.

   [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>.

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   [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>.

   [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>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

   [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>.

   [RFC8795]  Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Gonzalez de Dios, "YANG Data Model for Traffic
              Engineering (TE) Topologies", RFC 8795,
              DOI 10.17487/RFC8795, August 2020,
              <https://www.rfc-editor.org/info/rfc8795>.

   [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.

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   [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.

   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:

   o  Aihua Guo

   o  Bo Wu

   o  Greg Mirsky

   o  Lou Berger

   o  Rakesh Gandhi

   o  Ran Chen

   o  Sergio Belotti

   o  Stewart Bryant

   o  Tomonobu Niwa

   o  Xuesong Geng

   Further useful comments were received from Daniele Ceccarelli, Uma
   Chunduri, Pavan Beeram, and Tarek Saad.

Contributors

   The following authors contributed significantly to this document:

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

      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
   UK

   Email: adrian@olddog.co.uk

   Eric Gray
   Independent
   USA

   Email: ewgray@graiymage.com

   John Drake
   Juniper Networks
   USA

   Email: jdrake@juniper.net

   Reza Rokui
   Nokia

   Email: reza.rokui@nokia.com

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   Shunsuke Homma
   NTT
   Japan

   Email: shunsuke.homma.ietf@gmail.com

   Kiran Makhijani
   Futurewei
   USA

   Email: kiranm@futurewei.com

   Luis M. Contreras
   Telefonica
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com

   Jeff Tantsura
   Juniper Networks

   Email: jefftant.ietf@gmail.com

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