Network Working Group                                       E. Gray, Ed.
Internet-Draft                                                  Ericsson
Intended status: Informational                             J. Drake, Ed.
Expires: 14 January 2021                                Juniper Networks
                                                            13 July 2020

                 Framework for Transport Network Slices


   This memo discusses setting up special-purpose transport connections
   using existing IETF technologies.  These connections are called
   transport 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 transport 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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 14 January 2021.

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Copyright Notice

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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Transport Slice Objectives  . . . . . . . . . . . . . . . . .   4
   3.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Management systems or other applications  . . . . . . . .   6
     3.2.  Expressing connectivity intents . . . . . . . . . . . . .   6
     3.3.  Transport Slice Controller (TSC)  . . . . . . . . . . . .   8
       3.3.1.  Northbound Interface (NBI)  . . . . . . . . . . . . .   9
     3.4.  Mapping . . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.5.  Underlying technology . . . . . . . . . . . . . . . . . .   9
   4.  Applicability of ACTN to Transport 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 transport slices, as
   defined in [I-D.nsdt-teas-transport-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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   *  Transport Slice

   *  Transport Slice Controller (TSC)

   *  Transport Network Controller (TNC)

   *  Northbound Interface (NBI)

   *  Southbound Interface (SBI)

   This framework is intended as a structure for discussing interfaces
   and technologies.  It is not intended to be 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 ideas expressed here.

   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 transport 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).
   Transport network 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 transport
   network can be very different, which requires the transport network
   to have the capability of supporting multiple different transport

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

   A transport slice could span multiple technologies and multiple
   administrative domains.  Depending on the transport slice consumer's
   requirements, a transport slice could be isolated from other, often
   concurrent transport slices in terms of data, control and management

   The consumer expresses requirements for a particular transport slice
   by specifying what is required rather than how the requirement is to
   be fulfilled.  That is, the transport slice consumer's view of a
   transport 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 transport 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 transport 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.  Transport Slice Objectives

   It is intended that transport 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 transport 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 transport slices,
   see [I-D.ietf-teas-enhanced-vpn] (in particular, section 3).

3.  Framework

   A number of transport slice services will typically be provided over
   a shared underlying network infrastructure.  Each transport 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 transport 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 transport slices.

   Transport Slice Definition
   ([I-D.nsdt-teas-transport-slice-definition]) defines the role of a
   Customer (or User) and a Transport Slice Controller.  That draft also
   defines a TSC Northbound Interface (NBI).

   A transport slice user is served by the Transport Slice Controller
   (TSC), as follows:

   *  The TSC takes requests from a management system or other
      application, which are then communicated via an NBI.  This
      interface carries data objects the transport slice user provides,
      describing the needed transport 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 transport 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 transport
      slice instances on top of an underlying network infrastructure.

   *  The TSC 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

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

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3.1.  Management systems or other applications

   The transport 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 transport slices.

3.2.  Expressing connectivity intents

   The Transport Slice Controller (TSC) northbound interface (NBI) can
   be used to communicate between transport slice users (or consumers)
   and the TSC.

   A transport slice user may be a network operator who, in turn,
   provides the transport slice to another transport slice user or

   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

   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 transport slice
   consumers and other users of the transport network infrastructure.

   The benefits of this model can include:

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

   *  Layered Implementation: the transport 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
      TSC NBI, even if that information is available);

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

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   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
   transport 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 transport
   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 transport 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

   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

   *  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,

   While several generic formats and data models for specific purposes
   exist, it is expected that transport slice management may require
   enhancement or augmentation of existing data models.

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3.3.  Transport Slice Controller (TSC)

   The transport slice controller takes abstract requests for transport
   slices and implements them using a suitable underlying technology.  A
   transport slice controller is the key building block for control and
   management of the transport slice.  It provides the
   creation/modification/deletion, monitoring and optimization of
   transport Slices in a multi-domain, a multi-technology and multi-
   vendor environment.

   A TSC northbound interface (NBI) is needed for communicating details
   of a transport slice (configuration, selected policies, operational
   state, etc.), as well as providing information to a slice requester/
   consumer about transport 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 transport slices.  The API exposed by this NBI
      communicates the endpoints of the transport slice, transport 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
      transport slice that meets criteria specified via the NBI.The TSC
      also retains information about the mapping of this abstract
      topology to underlying components of the transport slice as
      necessary to monitor transport slice status and performance.

   *  Provides "Mapping Functions" for the realization of transport
      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 transport slice.

   *  Using the telemetry data from the underlying realization of a
      transport slice (i.e. services/paths/tunnels), evaluates the
      current performance against transport slice SLO parameters and
      exposes them to the transport slice consumer via the NBI.  The TSC
      NBI may also include a capability to provide notification in case

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      the transport slice performance reaches threshold values defined
      by the transport slice consumer.

3.3.1.  Northbound Interface (NBI)

   The Transport Slice Controller provides a Northbound Interface (NBI)
   that allows consumers of network slices to request and monitor
   transport slices.  Consumers operate on abstract transport 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 transport slices.

   The NBI uses protocol mechanisms and information passed over those
   mechanisms to convey desired attributes for transport 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
   transport slices, as well providing the above model information.

3.4.  Mapping

   The main task of the transport slice controller is to map abstract
   transport slice requirements to concrete technologies and establish
   the required connectivity, and ensuring that required resources are
   allocated to the transport 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.

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

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   A transport slice can be realized in a network, using specific
   underlying technology or technologies.  The creation of a new
   transport 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 Transport 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 transport slice is realized
   in the network (i.e. using tunnels of type RSVP or SR), the
   definition of transport slice does not change at all but rather its

4.  Applicability of ACTN to Transport 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

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

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

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

       |             Customer                |  |
                         ^                      |     ACTN
                         |                         Terminology
                         v                      |  and Concepts
       | A higher level operation system     |  |   +-----+
       |(e.g. e2e network slice orchestrator)| ===> | CNC |
       +-------------------------------------+  |   +-----+
                         ^                             ^
                         | TSC NBI              |      | CMI
                         v                             v
       +-------------------------------------+  |   +------+
       |      Transport Slice Controller     | ===> | MDSC |
       +-------------------------------------+  |   +------+
                         ^                             ^
                         | TSC SBI              |      | MPI
                         v                             v
       +-------------------------------------+  |   +-----+
       |   Transport Network Controller(s)   | ===> | PNC |
       +-------------------------------------+  |   +-----+

                Terminology/Concepts            |
               Used in this Document

                              Figure 1

   Note that the left-hand side of this figure comes from Transport
   Slice Definition ([I-D.nsdt-teas-transport-slice-definition]).

   The TSC NBI conveys the generic transport slice requirements.  These
   may then be realized using an SBI within the TSC.

   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 Transport Network Controller (TNC) is depicted as a single block,
   analogous to the Provisioning Network Controller (in this example).
   In the ACTN framework, however, it is also possible that the TNC

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   function is decomposed into MDSC and PNC - that is, the TNC 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 TSC in Figure 1 are out of scope in this document -
   hence the specifics of the relationship between TNC 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
   TSC might also directly include TNC 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 transport 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 TNC 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 TSC.  As
   in the TNC/PNC case, this way of comparing ACTN to this work is not
   useful as the TSC and TSC NBI are the focus on this document.

5.  Considerations

5.1.  Monitoring

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

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5.2.  Security Considerations

   Transport 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 transport slice (for instance,
   compute resources) can be just as service degrading as delaying
   physical transmission of associated packet in the network.

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

   *  Ren Chen

   *  Sergio Belotti

   *  Shunsuke Homma

   *  Stewart Bryant

   *  Tomonobu Niwa

   *  Xuesong Geng

7.  References

7.1.  Normative References

              Rokui, R., Homma, S., Makhijani, K., Contreras, L., and J.
              Tantsura, "IETF Definition of Transport Slice", Work in
              Progress, Internet-Draft, draft-nsdt-teas-transport-slice-
              definition-03, 12 July 2020, <

7.2.  Informative References

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

              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-05, 19 February 2020, <

              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Services", Work in Progress, Internet-Draft, draft-ietf-
              teas-enhanced-vpn-05, 18 February 2020,

              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-03, 8 March 2020,

              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,

              NGMN Alliance, ., "Description of Network Slicing
              media/161010_NGMN_Network_Slicing_framework_v1.0.8.pdf ,

   [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,

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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,

   [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,

   [RFC3417]  Presuhn, R., Ed., "Transport Mappings for the Simple
              Network Management Protocol (SNMP)", STD 62, RFC 3417,
              DOI 10.17487/RFC3417, December 2002,

   [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,

   [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, <>.

   [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,

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,

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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,

   [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,

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,

   [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,

   [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, <>.

   [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.


   The following authors contributed significantly to this document:

   Jari Arkko


   Dhruv Dhody

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   Huawei, India


   Reza Rokui


   Xufeng Liu


   Jie Dong


Authors' Addresses

   Eric Gray (editor)


   John Drake (editor)
   Juniper Networks


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