Network Working Group                                     A. Farrel, Ed.
Internet-Draft                                        Old Dog Consulting
Intended status: Informational                                   E. Gray
Expires: October 16, 18, 2021                                       Ericsson
                                                                J. Drake
                                                        Juniper Networks
                                                                R. Rokui
                                                                   Nokia
                                                                S. Homma
                                                                     NTT
                                                            K. Makhijani
                                                               Futurewei
                                                           LM. Contreras
                                                              Telefonica
                                                             J. Tantsura
                                                        Juniper Networks
                                                          April 14, 16, 2021

                   Framework for IETF Network Slices
                 draft-ietf-teas-ietf-network-slices-00
                 draft-ietf-teas-ietf-network-slices-01

Abstract

   <FAb>

   This memo discusses setting up special-purpose document describes network connections
   using existing slicing in the context of networks
   built from IETF technologies.  These connections are called IETF
   network slices for  It defines the purposes term "IETF Network
   Slice" and establishes the general principles of this memo. network slicing in
   the IETF context.

   The memo document discusses the general framework for this setup, 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 memo
   document also discusses related considerations with monitoring and
   security.

   This memo is intended for discussing interfaces and technologies.  It
   is not intended to be a new set of concrete interfaces or
   technologies.  Rather, it should be seen as an explanation of how
   some existing, concrete IETF VPN and traffic-engineering technologies
   can be used to create IETF network slices.  Note that there are a
   number of these technologies, and new technologies or capabilities
   keep being added.  This memo is also not intended presume any
   particular technology choice.

   <DAb>

   This document also provides a definition definitions of the term "IETF Network Slice"
   for use within the IETF and specifically as a reference for related terms to enable
   consistent usage in other IETF documents that describe or use aspects
   of network slices.

   The document also describes the characteristics of an IETF network
   slice, related terms and their meanings, and explains how IETF
   network slices can be used in combination with end-to-end network
   slices or independent of them. 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/.

   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 October 16, 18, 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terms and Abbreviations . . . . . . . . . . . . . . . . . . .   6   5
   3.  IETF Network Slice Objectives . . . . . . . . . . . . . . . .   7   6
     3.1.  Definition and Scope of IETF Network Slice  . . . . . . .   7   6
   4.  IETF Network Slice System Characteristics . . . . . . . . . .   8   7
     4.1.  Objectives for IETF Network Slices  . . . . . . . . . . .   8   7
       4.1.1.  Service Level Objectives  . . . . . . . . . . . . . .   9
       4.1.2.  Minimal Set of SLOs   8
     4.2.  IETF Network Slice Endpoints  . . . . . . . . . . . . . .  10
       4.2.1.  IETF Network Slice Connectivity Types . . .   9
       4.1.3.  Other Objectives . . . . .  12
     4.3.  IETF Network Slice Decomposition  . . . . . . . . . . . . .  11

     4.2.  IETF Network Slice Endpoints  . . . . . . . . . . . . . .  11
       4.2.1.  IETF Network Slice Connectivity Types . . . . . . . .  13
     4.3.  IETF Network Slice Composition  . . . . . . . . . . .  12
   5.  Framework . .  13
   5.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .  14  12
     5.1.  IETF Network Slice Stakeholders . . . . . . . . . . . . .  15  12
     5.2.  Management Systems or Other Applications  . . . . . . . .  15
     5.3.  Expressing Connectivity Intents . . . . . . . . . . . . .  16
     5.4.  IETF Network Slice Structure  . . . . . . . . . . . . . .  17
     5.5.  13
     5.3.  IETF Network Slice Controller (NSC) . . . . . . . . . . .  19
       5.5.1.  15
       5.3.1.  IETF Network Slice Controller Interfaces  . . . . . .  20
       5.5.2.  17
       5.3.2.  Northbound Interface (NBI)  . . . . . . . . . . . . .  21
     5.6.  Mapping . . . . . . . . . . .  17
     5.4.  IETF Network Slice Structure  . . . . . . . . . . . . . .  22
     5.7.  18
     5.5.  Realizing IETF Network Slice  . . . . . . . . . . . . . .  22
       5.7.1.  20
       5.5.1.  Underlying Technology . . . . . . . . . . . . . . . .  22  20
   6.  Applicability of ACTN to IETF Network Slices  . . . . . . . .  23  21
   7.  Isolation in IETF Network Slices  . . . . . . . . . . . . . .  25  23
     7.1.  Isolation as a Service Requirement  . . . . . . . . . . .  25  23
     7.2.  Isolation in IETF Network Slice Realization . . . . . . .  26  24
   8.  Management Considerations . . . . . . . . . . . . . . . . . .  26  24
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  26  24
     9.1.  Privacy Considerations  . . . . . . . . . . . . . . . . .  28  25
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28  26
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  28  26
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  29  26
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30  27
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  30  27
     13.2.  Informative References . . . . . . . . . . . . . . . . .  30  27
   Appendix A.  Unused Material  . . . . . . . . . . . . . . . . . .  34  31
     A.1.  Abstract  . . . . . . . . . . . . . . . . . . . . . . . .  32
     A.2.  Management Systems or Other Applications  . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  34  32

1.  Introduction

   ===================== EDITOR'S NOTE =====================

   This document is a merge of the text in
   [I-D.ietf-teas-ietf-network-slice-definition] and
   [I-D.ietf-teas-ietf-network-slice-framework].  In this version, the
   text is presented as a simple inclusion of all text included from the contributing documents.  The only work performed by the Editor in
   this revision is the assignment of text documents has been re-arranged to
   rationalise the sections of the
   document, and structure, but no substantive changes have been made.
   Additionally, the marking Editor has made a number of the text to indicate its origin, as well
   as stylistic edits and
   fixed further simple editorial fixes to resolve the most basic typographic and formatting issues.

   For this purpose,

   In the case that the source text in this revision is tagged to show its
   origin using the format <D1.3> or <F2.4> where the letters 'D' and
   'F' indicate the definitions draft
   [I-D.ietf-teas-ietf-network-slice-definition] and the framework draft

   [I-D.ietf-teas-ietf-network-slice-framework] respectively, and the
   subsequent numbers indicate the the section of the source document.

   In the case that the source text is not used within not used within the document, it
   is presented in Appendix A.

   It is expected that this is a short term measure and that later
   revisions will be presented as text in its own right.

   =================== END EDITOR'S NOTE ===================

   <D1.>

   A number of use cases benefit from network connections that along
   with the connectivity provide assurance of meeting a specific set of
   objectives wrt with respect to network resources use.  In this document, as detailed
   in the subsequent sections, we refer to this  This connectivity
   and resource commitment is referred to as an 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 Slice. 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 the network slices include 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

   The use cases are further described in
   [I-D.ietf-teas-ietf-network-slice-framework].

   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.  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.

   IETF network slices 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 Network Slice is technology-agnostic so as to
   allow a consumer to describe their network connectivity objectives in
   a common format, independent of the underlying technologies used.

   <F1.>

   This document also provides a framework for discussing IETF network
   slices, Network
   Slices.  This framework is intended as defined in [I-D.ietf-teas-ietf-network-slice-definition]. a structure for discussing
   interfaces and technologies.  It is the intention in this document to use terminology consistent
   with this and other definitions provided in that document.

   In particular, this document uses the following terminology defined
   in the definitions document:

   o  IETF Network Slice

   o  IETF Network Slice Controller (NSC)

   o  Network Controller (NC)

   o  Northbound Interface (NBI)

   o  Southbound Interface (SBI)

   This framework is intended as a structure for discussing interfaces
   and technologies.  It is not intended 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 provide the VPNs is often referred to as an underlay
   network, and the VPN is often called an overlay network.  As an
   example technology, a VPN may in turn serve as an underlay network
   for IETF network slices.

   Note: It Network Slices.

   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, but at least in the beginning there
   is no plan for the creation of new protocols or interfaces.

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).  IETF
   network slice
   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 consumer's use
   of IETF network slice Network Slice can be very different, which requires the
   underlay network to have the capability of supporting multiple
   different IETF network slices. Network Slices.

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

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

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

   Thus, there is a need to create logical network structures with
   required characteristics.  The consumer 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 Network Slice consumer 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 a framework for the use of existing
   technologies as components to provide a an IETF network slice Network Slice service,
   and might also discuss (or reference) modified and potential new
   technologies, as they develop (such as candidate technologies
   described in section 5 of [I-D.ietf-teas-enhanced-vpn]).

2.  Terms and Abbreviations

   <D2.>

   The terms and abbreviations used in this document are listed below.

   o  NBI: NorthBound Interface

   o  NS: Network Slice

   o  NSC: Network Slice Controller
   o  NBI: NorthBound Interface  NSE: Network Slice Endpoint

   o  SBI: SouthBound Interface

   o  SLA: Service Level Agreement

   o  SLI: Service Level Indicator

   o  SLO: Service Level Objective

   o  SLA: Service Level Agreement

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

3.  IETF Network Slice Objectives

   <F2.>

   It is intended that IETF network slices 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.

   And it

   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 Network Slices to move packets between the specified
   end-points in accordance with specified characteristics.

   As an example of requirements that might apply to IETF network
   slices, Network
   Slices, see [I-D.ietf-teas-enhanced-vpn] (in particular, section 3).

3.1.  Definition and Scope of IETF Network Slice

   <D3.>

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

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

   IETF network slices 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 Network Slice is technology-agnostic, and the means for IETF
   network slice
   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 Network Slices are described in the following
   sections.

   Term "Slice" refers to a set of characteristics and behaviours that
   separate one type of user-traffic from another.  IETF network slice 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

   <D4.>

   The following subsections describe the characteristics of IETF
   network slices.
   Network Slices.

4.1.  Objectives for IETF Network Slices

   <D4.1.>

   An IETF network slice Network Slice is defined in terms of several quantifiable
   characteristics or service level objectives Service Level Objectives (SLOs).  SLOs along with
   the terms Service Level Indicator (SLI) and Service Level Agreement
   (SLA) are used to define the performance of a service at different
   levels.

   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.

   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 network slice is expressed in terms of the set of SLOs
   that are to be delivered for the different connections between
   endpoints.

   A Service Level Agreement (SLA) is an explicit or implicit contract
   between the consumer of an IETF network slice Network Slice and the provider of the
   slice.  The SLA is expressed in terms of a set of SLOs and may
   include commercial terms as well as the consequences of missing/
   violating the SLOs they contain.

   Additional descriptions of IETF network slice Network Slice attributes is covered
   in [I-D.contreras-teas-slice-nbi].

4.1.1.  Service Level Objectives

   <D4.1.1.>

   SLOs define a set of network attributes and characteristics that
   describe an IETF network slice. Network Slice.  SLOs do not describe 'how' how the IETF
   network slices
   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 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 network slice.

4.1.2. IETF Network Slice.

4.1.1.1.  Minimal Set of SLOs

   <D4.1.2.>

   This document defines a minimal set of SLOs and later systems or
   standards could extend this set as per described in Section 4.1.3. 4.1.1.2.

   SLOs can be categorized in to 'Directly Measurable Objectives' or
   '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'.  While 'Indirectly
   Measurable Objectives' include security, geographical restrictions,
   maximum occupancy level objectives.  The later standard might define
   other SLOs as needed.

   Editor's Note TODO: replace Minimal set to most commonly used
   objectives to describe network behavior.  Other directly or
   indirectly measurable objectives may be requested by that consumer of
   an IETF network slice. Network Slice.

   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 Network Slice is available in
         accordance with the SLOs associated with it.

      Security

         An IETF network slice Network Slice consumer may request that the network
         applies encryption or other security techniques to traffic
         flowing between endpoints.

         Note that the use of security or the violation of this SLO is
         not directly observable by the IETF network slice Network Slice consumer and
         cannot be measured as a quantifiable metric.

         Also note that the objective may include request for encryption
         (e.g., [RFC4303]) between the two endpoints explicitly to meet
         architecture recommendations as in [TS33.210] or for compliance
         with [HIPAA] and/or [PCI].

         Editor's Note:

         Please see more discussion on security in Section 9.

4.1.3.

4.1.1.2.  Other Service Level Objectives

   <D4.1.3.>

   Additional SLOs may be defined to provide additional description of
   the IETF network slice Network Slice that a consumer requests.

   If the IETF network slice Network Slice consumer 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).

   Maximal occupancy for an IETF network slice Network Slice should be provided.
   Since it carries traffic for multiple flows between the two
   endpoints, the objectives should also say if they are for the entire
   connection, group of flows or on per flow basis.  Maximal occupancy
   should specify the scale of the flows (i.e., maximum number of flows
   to be admitted) and optionally a maximum number of countable resource
   units, e.g., IP or MAC addresses a slice might consume.

4.2.  IETF Network Slice Endpoints

   <D4.2.>

   As noted in Section 3.1, an IETF network slice 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, multipoint-to-point, or multipoint-to-multipoint. multipoint-to-
   multipoint.

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

   The characteristics of IETF network slice endpoints (NSEs) NSEs are as follows:

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

   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. Network Slice Controller (NSC).

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

   o  Similarly to IETF network slices, Network Slices, the IETF network slice endpoints Network Slice Endpoints
      are logical entities that are mapped to services/tunnels/paths
      endpoints in IETF network slice 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, 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

   <D4.2.1.>

   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 Composition

   <D4.3.> Decomposition

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

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

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

5.  Framework

   <F3.>

   A number of IETF network slice Network Slice services will typically be provided
   over a shared underlying network infrastructure.  Each IETF network
   slice 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 Network Slice
   consumer.  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. Network Slices.

   Section 3 of [I-D.ietf-teas-enhanced-vpn] provides an example
   architecture that might apply in using the technology described in
   this document.

5.1.  IETF Network Slice Definition
   ([I-D.ietf-teas-ietf-network-slice-definition] defines the role of a
   Customer (or User) and a Stakeholders

   An IETF Network Slice Controller.  That
   document also defines a NSC Northbound Interface (NBI). and its realization involves the following
   stakeholders and it is relevant to define them for consistent
   terminology.

   Consumer:  A IETF network slice user consumer is served by the requester of an IETF Network Slice.
      Consumers may request monitoring of SLOs.  A consumer may manage
      the IETF Network Slice
   Controller (NSC), as follows:

   o  The service directly by interfacing with the
      IETF NSC takes requests from a management system or other
      application, which are then communicated via indirectly through an NBI.  This
      interface carries data objects the IETF orchestrator.

   Orchestrator:  An orchestrator is an entity that composes different
      services, resource and network slice user
      provides, describing requirements.  It interfaces with
      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.

   Section 3 of [I-D.ietf-teas-enhanced-vpn] provides an example
   architecture that might apply in using the technology described in
   that document.

5.1.  IETF Network Slice Stakeholders

   <D6.>

   An IETF network slice and its realization involves the following
   stakeholders and it is relevant to define them for consistent
   terminology.

   Consumer:  A consumer is the requester of an IETF network slice.
      Consumers may request monitoring of SLOs.  A consumer may manage
      the IETF network slice service directly by interfacing with the
      IETF network slice controller or indirectly through an
      orchestrator.

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

   IETF Network Slice Controller (NSC):  It realizes an IETF network
      lice 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
      network slice controllers
      NSCs and different types of orchestrators.  An IETF network slice Network Slice
      operator (or slice operator for short) manages one or more IETF network slices
      Network Slices using the IETF network
      slice Controller(s). NSCs.

   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 Network Slices in a
      network.

5.2.  Management Systems or Other Applications

   <F3.1.>

   The IETF network slice system is used by a management system or other
   application.  These systems and applications may also be a part of a
   higher level function in the system, e.g., putting together network
   functions, access equipment, application specific components, as well
   as the IETF network slices.

5.3.  Expressing Connectivity Intents

   <F3.2.>

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

   A

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

   Using the NBI, a consumer expresses requirements for a particular
   slice by specifying what is required rather than how that is to be
   achieved.  That is, the consumer's view of a slice is an abstract
   one.  Consumers 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 consumer and provider are
   associated with a single administrative domain, in order to reduce
   the potential for adverse interactions between IETF network slice Network Slice
   consumers 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 Network Slice consumers 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 consumer
      applications, and network information (advertisements, protocols,
      etc.) that a consumer cannot interpret or respond to (note - a
      consumer should not use network information not exposed via the
      NSC NBI, even if that information is available);

   o  Scalability: consumers 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].

   This framework document does not assume any particular layer at which
   IETF network slices 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,
   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 ACTN ([RFC8453] and
   [RFC8454]).  The principles and mechanisms associated with layered
   networking are applicable to IETF network slices. 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 Network Slice management may require
   enhancement or augmentation of existing data models.

5.4.

5.3.  IETF Network Slice Structure

   <D5.>

   Editor's note: This content of this section merged with Relationship
   with E2E slice discussion. Controller (NSC)

   The IETF NSC takes abstract requests for IETF Network Slices and
   implements them using a suitable underlying technology.  An IETF network slice 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 set multi-domain,
   a multi-technology and multi-vendor environment.

   The main task of connections among various endpoints the IETF NSC is to form a logical network map abstract IETF Network Slice
   requirements to concrete technologies and establish required
   connectivity, and ensuring that meets required resources are allocated to
   the SLOs agreed upon.

                 |------------------------------------------|
       NSE1 O....|                                          |....O NSE2
         .       |                                          |    .
         .       | IETF Network Slice.

   A NSC northbound interface (NBI) is needed for communicating details
   of a 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 2: IETF Network slice

   Figure 2 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 networks endpoints (EP).
   Also, the IETF network slice endpoints 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
   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 consumer [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.

5.5.  IETF Network Slice Controller (NSC)

   <F3.3.>

   The IETF Network Slice Controller takes abstract requests for IETF
   network slices and implements them using a suitable underlying
   technology.  A IETF Network Slice Controller 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.

   A 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/consumer about IETF network slice 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. Network Slices.  The API exposed by this NBI
      communicates the endpoints of the IETF network slice, IETF network
      slice 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 Network Slice that meets criteria specified via the NBI.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 Network Slice status and performance.

   o  Provides "Mapping Functions" for the realization of IETF network
      slices. 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 states, etc.) for all elements in the
      abstract topology used to realize the IETF network slice. Network Slice.

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

   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 consumer.

5.5.1. 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

   <D7.>

   The interworking and interoperability among the different
   stakeholders to provide common means of provisioning, operating and
   monitoring the IETF network slices Network Slices is enabled by the following
   communication interfaces (see Figure 3). 2).

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

   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.

                        +------------------------------------------+
                        | Consumer 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 consumers of network slices to request and monitor
   IETF Network Slices.  Consumers 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 slice, Network Slices and
   their status.  The information is expected to be represented as a
   well-defined data model, and should include at least endpoint and
   connectivity information, SLO specification, and status information.

   To accomplish this, the
      NSC can use the interface NBI needs to report convey information needed to
   support communication across the operational state NBI, in terms of an
      IETF network slice to identifying the consumer.

   NSC Southbound Interface (SBI):  The NSC Southbound Interface is an
      interface between
   IETF Network Slices, as well providing the NSC and network controllers.  It above model information.

5.4.  IETF Network Slice Structure

   An IETF Network Slice is
      technology-specific and may be built around the many a set of connections among various endpoints
   to form a logical network
      models defined within that meets the IETF.

                        +------------------------------------------+
                        | Consumer higher level operation system   |
                        |   (e.g E2E network slice orchestrator) SLOs agreed upon.

                 |------------------------------------------|
       NSE1 O....|                                          |....O NSE2
         .       |
                        +------------------------------------------+
                                             A                                          | NSC NBI
                                             V
                        +------------------------------------------+    .
         .       |             IETF Network Slice Controller (NSC)           |
                        +------------------------------------------+
                                             A    .
         .       | NSC SBI
                                             V
                        +------------------------------------------+  (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 Controllers            |
                        +------------------------------------------+ Slice Endpoints
         EP:  Serivce/tunnels/path Endpoints used to realize the
              IETF Network Slice

                       Figure 3: Interface of 3: IETF Network Slice Controller

5.5.2.  Northbound Interface (NBI)

   <F3.3.1.>

   The

   Figure 3 illustrates a case where an IETF Network Slice Controller provides
   connectivity between a Northbound Interface
   (NBI) that allows consumers set of IEFT network slices to request slice endpoints (NSE)
   pairs with specific SLOs (e.g., guaranteed minimum bandwidth of x bps
   and monitor
   IETF network slices.  Consumers operate on abstract guaranteed delay of no more than y ms).  The IETF network
   slices, with details related Network Slice
   endpoints are mapped to their realization hidden.

   The NBI complements various the underlay IETF services, tunnels, path models by
   providing an abstract layer Network Slice Endpoints
   (NEPs).  Also, the IETF NSEs on top of these models.

   The NBI is independent of type of the same IETF network functions or services that
   need to be connected, i.e., it is independent of any specific
   storage, software, protocol, or platform used slice may
   belong to realize physical or
   virtual network connectivity the same or functions in support of different address spaces.

   IETF Network Slice structure fits into a broader concept of end-to-
   end network slices.

   The NBI uses protocol mechanisms and information passed over those
   mechanisms to convey desired attributes for IETF  A network slices and
   their status.  The information is expected to operator may be represented as responsible for
   delivering services over a
   well-defined data model, and should include at least endpoint number of technologies (such as radio
   networks) and
   connectivity information, SLO specification, for providing specific and status information.

   To accomplish this, the NBI needs fine-grained services (such
   as CCTV feed or High definition realtime traffic data).  That
   operator may need to convey information needed combine slices of various networks to
   support communication across the NBI, in terms produce an
   end-to-end network service.  Each of identifying the
   IETF these networks may include
   multiple physical or virtual nodes and may also provide network slices, as well providing the above model information.

5.6.  Mapping

   <F3.4.>

   The main task
   functions beyond simply carrying of the IETF technology-specific protocol data
   units.  An end-to-end network slice controller is to map abstract
   IETF defined by the 3GPP as a
   complete logical network slice requirements to concrete technologies and
   establish required connectivity, and ensuring that required resources
   are allocated provides a service in its entirety with
   a specific assurance to the consumer [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 slice.

5.7. slices and the
   sequential (or stitched) combination of slices of different networks.

5.5.  Realizing IETF Network Slice

   <D8.>

   Realization of IETF network slices Network Slices is out of scope of this document.
   It is a mapping of the definition of the IETF network slice 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 through VPNs (see, for example,
   [I-D.ietf-teas-enhanced-vpn], a variety of tunneling technologies
   such as Segment Routing, MPLS, etc.  Accordingly, endpoints may be
   realized as physical or logical service or network functions.

5.7.1.

5.5.1.  Underlying Technology

   <F3.5.>

   There are a number of different technologies that can be used,
   including physical connections, MPLS, TSN, Flex-E, etc.

   See Section 5 of [I-D.ietf-teas-enhanced-vpn] for instance, for
   example underlying technologies.

   Also, as outlined in "applicability of ACTN to IETF Network Slices"
   below, ACTN ([RFC8453]) offers a framework that is used elsewhere in
   IETF specifications to create virtual network (VN) services similar
   to IETF network slices. Network Slices.

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

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

   o  Step 2: This request will be processed by a an IETF Network Slice
      Controller 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 trasport slice.

   It is very clear that regardless of how IETF network slice Network Slice is
   realized in the network (i.e., using tunnels of type RSVP or SR), the
   definition of IETF network slice Network Slice does not change at all but rather
   its realization.

6.  Applicability of ACTN to IETF Network Slices

   <F4.>

   Abstraction and Control of TE Networks (ACTN - [RFC8453]) is an
   example of similar IETF work.  ACTN defines three controllers to
   support virtual network (VN) services -

   o  Customer Network Controller (CNC),

   o  Multi-Domain Service Coordinator (MDSC) and

   o  Provisioning Network Controller (PNC).

   A CNC is responsible for communicating a customer's VN requirements.

   A MDSC is responsible for multi-domain coordination, virtualization
   (or abstraction), customer mapping/translation and virtual service
   coordination to realize the VN requirement.  Its key role is to
   detach the network/service requirements from the underlying
   technology.

   A PNC oversees the configuration, monitoring and collection of the
   network topology.  The PNC is a underlay technology specific
   controller.

   While the ACTN framework is a generic VN framework that is used for
   various VN service beyond the IETF network slice, Network Slice, it is still a
   suitable basis to understand how the various controllers interact to
   realize a IETF network slice. Network Slice.

   One possible mapping between the IETF network slice, Network Slice, and ACTN,
   definitions is as shown in Figure 4.

                   IETF Network Slice                |   ACTN analogous
                 Terminology / Concepts                  Terminology
                                                     |    and Concepts
          +--------------------------------------+
          |Consumer higher level operation system|   |    +-----+
          | (e.g E2E network slice orchestrator) | =====> | CNC |
          +--------------------------------------+   |    +-----+
                            ^                                ^
                            | NSC NBI                |       | CMI
                            v                                v
          +-------------------------------------+    |    +------+
          | IETF Network Slice Controller (NSC) |  =====> | MDSC |
          +-------------------------------------+    |    +------+
                            ^                                ^
                            | NSC SBI                |       | MPI
                            v                                v
          +-------------------------------------+    |    +-----+
          |        Network Controller(s)        |  =====> | PNC |
          +-------------------------------------+    |    +-----+

          Figure 4: Mapping between IETF network slices Network Slices and ACTN

   Note that the left-hand side of this figure comes from IETF Network
   Slice Definition ([I-D.ietf-teas-ietf-network-slice-definition]).

   The NSC NBI conveys the generic IETF network slice Network Slice requirements.
   These may then be realized using an SBI within the NSC.

   As per [RFC8453] and [I-D.ietf-teas-actn-yang], the CNC-MDSC
   Interface (CMI) is used to convey the virtual network service
   requirements along with the service models and the MDSC-PNC Interface
   (MPI) is used to realize the service along network configuration
   models.  [I-D.ietf-teas-te-service-mapping-yang] further describe how
   the VPN services can be mapped to the underlying TE resources.

   The Network Controller is depicted as a single block, analogous to a
   Provisioning Network Controller (PNC - in this example).  In the ACTN
   framework, however, it is also possible that the NC function is
   decomposed into MDSC and PNC - that is, the NC may comprise hierarchy
   as needed to handle the multiple domains and various underlay
   technologies, whereas a PNC in ACTN is intended to be specific to at
   most a single underlay technology and (likely) to individual devices
   (or functional components).

   Note that the details of potential implementations of everything that
   is below the NSC in Section 6 are out of scope in this document -
   hence the specifics of the relationship between NC and PNC, and the
   possibility that the MDSC and PNC may be combined are at most
   academically interesting in this context.  Another way to view this
   is that, in the same way that ACTN might combine MDSC and PNC, the
   NSC might also directly include NC functionality.

   [RFC8453] also describes TE Network Slicing in the context of ACTN as
   a collection of resources that is used to establish a logically
   dedicated virtual network over one or more TE networks.  In case of
   TE enabled underlying network, ACTN VN can be used as a base to
   realize the IETF network slicing Network Slicing by coordination among multiple peer
   domains as well as underlay technology domains.

   Section 6 shows only one possible mapping as each ACTN component (or
   interface) in the figure may be a composed differently in other
   mappings, and the exact role of both components and subcomponents
   will not be always an exact analogy between the concepts used in this
   document and those defined in ACTN.

   This is - in part - shown in a previous paragraph in this section
   where it is pointed out that the NC may actually subsume some aspects
   of both the MDSC and PNC.

   Similarly, in part depending on how "customer" is interpreted, CNC
   might merge some aspects of the higher level system and the NSC.  As
   in the NC/PNC case, this way of comparing ACTN to this work is not
   useful as the NSC and NSC NBI are the focus on this document.

7.  Isolation in IETF Network Slices

   <D9.>

   An IETF network slice Network Slice consumer may request, that the IETF Network
   Slice delivered to them is isolated from any other network slices of
   services delivered to any other consumers.  It is expected that the
   changes to the other network slices of services do not have any
   negative impact on the delivery of the IETF network slice. Network Slice.

7.1.  Isolation as a Service Requirement

   <D9.1.>

   Isolation may be an important requirement of IETF network slices Network Slices for
   some critical services.  A consumer may express this request as an
   SLO.

   This requirement can be met by simple conformance with other SLOs.
   For example, traffic congestion (interference from other services)
   might impact on the latency experienced by an IETF network slice. Network Slice.
   Thus, in this example, conformance to a latency SLO would be the
   primary requirement for delivery of the IETF network slice Network Slice service,
   and isolation from other services might be only a means to that end.

   It should be noted that some aspects of isolation may be measurable
   by a consumer who have the information about the traffic on a number
   of IETF network slices Network Slices or other services.

7.2.  Isolation in IETF Network Slice Realization

   <D9.2.>

   Delivery of isolation is achieved in the realization of IETF network
   slices, Network
   Slices, with existing, in-development, and potential new technologies
   in IETF.  It depends on how a network operator decides to operate
   their network and deliver services.

   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, Network Slice, to sharing or resources
   with safeguards.  For example, traffic separation between different
   IETF network slices 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 network slices, etc.

8.  Management Considerations

   <F5.1.>

   IETF network slice 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
   Network Slice as requirements change.  Dynamic reconfiguration might
   be needed.

9.  Security Considerations

   <D10.>

   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 consumer defined IETF network slices Network Slices will be mapped to their
      realization in the unerlay networks.  It will be required by
      underlay networks to have capabilities to conform to consumer's
      requests as some aspects of security may be expressed in SLOs.

   o  IETF network slice controller NSC authentication: Unerlying networks need to be protected
      against the attacks from an adversary NSC as they can destablize
      overall network operations.  It is particularly critical since an
      IETF network slice Network Slice may span across different networks, therefore,
      IETF NSC should have strong authentication with each those
      networks.  Futhermore, 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 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 Network
      Slice security.

   o  Data Integrity of an IETF network slice: Network Slice: A consumer 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. Network
      Slice.  It is expected that for data integrity, a consumer 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.

   <F5.2.>

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

9.1.  Privacy Considerations

   <F5.3.>

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

10.  IANA Considerations

   <F5.4.>

   There are no requests to IANA in this framework document.

11.  Acknowledgments

   <D12.>

   The entire TEAS NS design team and everyone participating in those
   discussion has contributed to this draft.  Particularly, Eric Gray,
   Xufeng Liu, Jie Dong, Adrian Farrel, and Jari Arkko for a thorough
   review among other contributions.

   <F6.>

   The entire TEAS NS 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: including the
   following people not listed elsewhere:

   o  Aihua Guo

   o  Bo Wu

   o  Greg Mirsky

   o  Jeff Tantsura

   o  Kiran Makhijani

   o  Lou Berger

   o  Luis M.  Contreras

   o  Rakesh Gandhi

   o  Ran Chen

   o  Sergio Belotti

   o  Shunsuke Homma

   o  Stewart Bryant

   o  Tomonobu Niwa

   o  Xuesong Geng

12.  Contributors

   The following authors contributed significantly to this document:

      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

13.  References

13.1.  Normative References

   [I-D.ietf-teas-ietf-network-slice-definition]
              Rokui, R., Homma, S., Makhijani, K., Contreras, L., and J.
              Tantsura, "Definition of IETF Network Slices", draft-ietf-
              teas-ietf-network-slice-definition-00 (work in progress),
              January 2021.

   [I-D.ietf-teas-ietf-network-slice-framework]
              Gray, E. and J. Drake, "Framework for IETF Network
              Slices", draft-ietf-teas-ietf-network-slice-framework-00
              (work in progress), March 2021.

13.2.  Informative References

   [BBF-SD406]
              Broadband Forum, ., "End-to-end network slicing", BBF
              SD-406 , n.d..

   [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.contreras-teas-slice-nbi]
              Contreras, L., Homma, S., and J. Ordonez-Lucena, "IETF
              Network Slice use cases and attributes for Northbound
              Interface of controller", draft-contreras-teas-slice-
              nbi-03 (work in progress), October 2020.

   [I-D.ietf-teas-actn-yang]
              Lee, Y., Zheng, H., Ceccarelli, D., Yoon, B., Dios, O.,
              Shin, J., and S. Belotti, "Applicability of YANG models
              for Abstraction and Control of Traffic Engineered
              Networks", draft-ietf-teas-actn-yang-06 (work in
              progress), August 2020.

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Service", draft-ietf-teas-enhanced-vpn-06 (work in
              progress), July 2020.

   [I-D.ietf-teas-te-service-mapping-yang]
              Lee, Y., Dhody, D., Fioccola, G., WU, Q., Ceccarelli, D.,
              and J. Tantsura, "Traffic Engineering (TE) and Service
              Mapping Yang Model", draft-ietf-teas-te-service-mapping-
              yang-05 (work in progress), November 2020.

   [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.

   [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>.

   [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>.

   [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>.

   [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.

   [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>.

Appendix A.  Unused Material

   This section includes material from the source documents that is not
   used in the body of this document.  It is intended for deletion.

   For this purpose, the text is tagged to show its origin using the
   format <D1.3> or <F2.4> where the letters 'D' and 'F' indicate the
   definitions draft [I-D.ietf-teas-ietf-network-slice-definition] and
   the framework draft [I-D.ietf-teas-ietf-network-slice-framework]
   respectively, and the subsequent numbers indicate the the section of
   the source document.

A.1.  Abstract

   <FAb>

   This memo is intended for discussing interfaces and technologies.  It
   is not intended to be a new set of concrete interfaces or
   technologies.  Rather, it should be seen as an explanation of how
   some existing, concrete IETF VPN and traffic-engineering technologies
   can be used to create IETF network slices.  Note that there are a
   number of these technologies, and new technologies or capabilities
   keep being added.  This memo is also not intended presume any
   particular technology choice.

A.2.  Management Systems or Other Applications

   <F3.1.>

   The IETF Network Slice system is used by a management system or other
   application.  These systems and applications may also be a part of a
   higher level function in the system, e.g., putting together network
   functions, access equipment, application specific components, as well
   as the IETF Network Slices.

Authors' Addresses

   Adrian Farrel (editor)
   Old Dog Consulting

   Email: adrian@olddog.co.uk

   Eric Gray
   Ericsson

   Email: ewgray@graiymage.com

   John Drake
   Juniper Networks

   Email: jdrake@juniper.net

   Reza Rokui
   Nokia

   Email: reza.rokui@nokia.com
   Shunsuke Homma
   NTT

   Email: shunsuke.homma.ietf@gmail.com

   Kiran Makhijani
   Futurewei

   Email: kiranm@futurewei.com

   Luis M. Contreras
   Telefonica
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com

   Jeff Tantsura
   Juniper Networks

   Email: jefftant.ietf@gmail.com