Internet DRAFT - draft-nsdt-teas-ns-framework

draft-nsdt-teas-ns-framework







Network Working Group                                       E. Gray, Ed.
Internet-Draft                                                  Ericsson
Intended status: Informational                             J. Drake, Ed.
Expires: 6 August 2021                                  Juniper Networks
                                                         2 February 2021


                   Framework for IETF Network Slices
                    draft-nsdt-teas-ns-framework-05

Abstract

   This memo discusses setting up special-purpose network connections
   using existing IETF technologies.  These connections are called IETF
   network slices for the purposes of this memo.  The memo discusses the
   general framework for this setup, the necessary system components and
   interfaces, and how abstract requests can be mapped to more specific
   technologies.  The memo 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.

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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   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 6 August 2021.






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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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IETF Network Slice Objectives . . . . . . . . . . . . . . . .   4
   3.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Management systems or other applications  . . . . . . . .   6
     3.2.  Expressing connectivity intents . . . . . . . . . . . . .   6
     3.3.  IETF Network Slice Controller (NSC) . . . . . . . . . . .   8
       3.3.1.  Northbound Interface (NBI)  . . . . . . . . . . . . .   9
     3.4.  Mapping . . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.5.  Underlying technology . . . . . . . . . . . . . . . . . .   9
   4.  Applicability of ACTN to IETF Network Slices  . . . . . . . .  10
   5.  Considerations  . . . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  Monitoring  . . . . . . . . . . . . . . . . . . . . . . .  12
     5.2.  Security Considerations . . . . . . . . . . . . . . . . .  13
     5.3.  Privacy Considerations  . . . . . . . . . . . . . . . . .  13
     5.4.  IANA Considerations . . . . . . . . . . . . . . . . . . .  13
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

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

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




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   *  IETF Network Slice

   *  IETF Network Slice Controller (NSC)

   *  Network Controller (NC)

   *  Northbound Interface (NBI)

   *  Southbound Interface (SBI)

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

   For example, virtual private networks (VPNs) have served the industry
   well as a means of providing different groups of users with logically
   isolated access to a common network.  The common or base network that
   is used to 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 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.

   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], 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 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 can be very different, which requires the
   underlay network to have the capability of supporting multiple
   different IETF network slices.





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   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.

   A IETF network slice could span multiple technologies and multiple
   administrative domains.  Depending on the IETF network slice
   consumer'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 consumer 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 consumer's view
   of a IETF 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 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 IETF 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.  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.

   And it is 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.




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

3.  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
   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.

   IETF Network Slice Definition
   ([I-D.ietf-teas-ietf-network-slice-definition]) defines the role of a
   Customer (or User) and a IETF Network Slice Controller.  That draft
   also defines a NSC Northbound Interface (NBI).

   A IETF network slice user is served by the IETF Network Slice
   Controller (NSC), as follows:

   *  The NSC takes requests from a management system or other
      application, which are then communicated via 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.

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

   *  The NSC maintains a record of the mapping from 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




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   architecture that might apply in using the technology described in
   that document.

3.1.  Management systems or other applications

   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.

3.2.  Expressing connectivity intents

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

   A IETF network slice user may be a network operator who, in turn,
   provides the IETF network slice to another IETF 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
   consumers and other users of the underlay network infrastructure.

   The benefits of this model can include:

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

   *  Layered Implementation: the underlay network comprises network
      elements that belong to a different layer network than 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);





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   *  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 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 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:

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

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

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

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

   *  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).




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   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.

3.3.  IETF Network Slice Controller (NSC)

   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 status and performance.
   The details for this NBI are not in scope for this document.

   The controller provides the following functions:

   *  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.

   *  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.

   *  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.

   *  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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   *  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 consumer 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 consumer.

3.3.1.  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 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 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.

3.4.  Mapping

   The main task of the IETF network slice controller 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.

3.5.  Underlying technology

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

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




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   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 netrwork slices.

   A 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:

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

   *  Step 2: This request will be processed by a IETF Network Slice
      Controller which specifies a mapping between northbound request to
      any IETF Services, Tunnels, and paths models.

   *  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 is
   realized in the network (i.e. using tunnels of type RSVP or SR), the
   definition of IETF network slice does not change at all but rather
   its realization.

4.  Applicability of ACTN to IETF Network Slices

   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 -

   *  Customer Network Controller (CNC),

   *  Multi-Domain Service Coordinator (MDSC) and

   *  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.




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

   One possible mapping between the IETF network slice, and ACTN,
   definitions is as shown in Figure 1 below.


                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 1

   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 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



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   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 Figure 1 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 by coordination among multiple peer
   domains as well as underlay technology domains.

   Figure 1 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.

5.  Considerations

5.1.  Monitoring

   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.








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5.2.  Security Considerations

   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, consumers might be well
   advised to take responsibility for their own security needs, possibly
   by encrypting traffic before hand-off to a service provider.

5.3.  Privacy Considerations

   Privacy of IETF network slice service consumers must be preserved.
   It should not be possible for one IETF network slice consumer to
   discover the presence of other consumers, 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 consumer.

5.4.  IANA Considerations

   There are no requests to IANA in this framework document.

6.  Acknowledgments

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



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   Significant contributions to this document were gratefully received
   from the contributing authors listed in the "Contributors" section.
   In addition we would like to also thank those others who have
   attended one or more of the design team meetings, including:

   *  Aihua Guo

   *  Bo Wu

   *  Greg Mirsky

   *  Jeff Tantsura

   *  Kiran Makhijani

   *  Lou Berger

   *  Luis M.  Contreras

   *  Rakesh Gandhi

   *  Ran Chen

   *  Sergio Belotti

   *  Shunsuke Homma

   *  Stewart Bryant

   *  Tomonobu Niwa

   *  Xuesong Geng

7.  References

7.1.  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", Work in
              Progress, Internet-Draft, draft-ietf-teas-ietf-network-
              slice-definition-00, 25 January 2021,
              <http://www.ietf.org/internet-drafts/draft-ietf-teas-ietf-
              network-slice-definition-00.txt>.

7.2.  Informative References





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

   [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", Work in Progress, Internet-Draft, draft-ietf-
              teas-actn-yang-06, 22 August 2020, <http://www.ietf.org/
              internet-drafts/draft-ietf-teas-actn-yang-06.txt>.

   [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", Work in Progress, Internet-Draft, draft-ietf-
              teas-enhanced-vpn-06, 13 July 2020, <http://www.ietf.org/
              internet-drafts/draft-ietf-teas-enhanced-vpn-06.txt>.

   [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", Work in Progress, Internet-Draft,
              draft-ietf-teas-te-service-mapping-yang-05, 2 November
              2020, <http://www.ietf.org/internet-drafts/draft-ietf-
              teas-te-service-mapping-yang-05.txt>.

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

   [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.

   [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>.





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   [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>.

   [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>.





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

   [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>.

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

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

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

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

Contributors

   The following authors contributed significantly to this document:

   Jari Arkko
   Ericsson

   Email: jari.arkko@piuha.net


   Dhruv Dhody




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   Huawei, India

   Email: dhruv.ietf@gmail.com


   Jie Dong
   Huawei

   Email: jie.dong@huawei.com


   Xufeng Liu

   Email: xufeng.liu.ietf@gmail.com


   Reza Rokui
   Nokia

   Email: reza.rokui@nokia.com


Authors' Addresses

   Eric Gray (editor)
   Ericsson

   Email: eric.gray@ericsson.com


   John Drake (editor)
   Juniper Networks

   Email: jdrake@juniper.net

















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