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TEAS Working Group                                         D. King (Ed.)
Internet-Draft                                        Old Dog Consulting
Intended status: Informational                              Y. Lee (Ed.)
Expires: July 2, 2018                                             Huawei

                                                         January 2, 2018


                Applicability of Abstraction and Control
        of Traffic Engineered Networks (ACTN) to Network Slicing
              draft-king-teas-applicability-actn-slicing-02

Abstract

   Network abstraction is a technique that can be applied to a network
   domain to select network resources by policy to obtain a view of
   potential connectivity

   Network slicing is an approach to network operations that builds on
   the concept of network abstraction to provide programmability,
   flexibility, and modularity.  It may use techniques such as Software
   Defined Networking (SDN) and Network Function Virtualization (NFV)
   to create multiple logical (virtual) networks, each tailored for a
   set of services that are sharing the same set of requirements, on
   top of a common network.

   These logical networks are referred to as transport network slices.
   A transport network slice does not necessarily represent dedicated
   resources in the network, but does constitute a commitment by the
   network provider to provide a specific level of service.

   The Abstraction and Control of Traffic Engineered Networks (ACTN)
   defines an SDN-based architecture that relies on the concepts of
   network and service abstraction to detach network and service
   control from the underlying data plane.

   This document outlines the applicability of ACTN to transport
   network slicing in an IETF technology network.  It also identifies
   the features of network slicing not currently within the scope of
   ACTN, and indicates where ACTN might be extended.

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 http://datatracker.ietf.org/drafts/current/.





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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on July 2, 2018.

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   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1. Introduction....................................................3
     1.1.  Terminology................................................4
   2. Requirements for Network Slicing................................4
     2.1.  Resource Slicing...........................................4
     2.2.  Network and Function Virtualization........................5
     2.3.  Resource Isolation.........................................5
     2.4.  Control and Orchestration..................................6
   3. Abstraction and Control of Traffic Engineered (TE)
      Networks (ACTN).................................................6
     3.1.  ACTN Virtual Network as a "Network Slice"..................8
     3.2.  Examples of ACTN Delivering Types of Network Slices........8
       3.2.1.  ACTN Used for Virtual Private Line Model...............9
       3.2.2.  ACTN Used for VPN Delivery Model.......................10
       3.2.3.  ACTN Used to Deliver a Virtual Customer Network........10
     3.3.  Network Slice Service Mapping from TE to ACTN VN Models....11
     3.4.  ACTN VN KPI Telemetry Models...............................12
   4. IANA Considerations.............................................12
   5. Security Considerations.........................................12
   6. Acknowledgements................................................12
   7. References......................................................13
   8. Contributors....................................................15
   Authors' Addresses.................................................15





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1.  Introduction

   The principles of network resource separation are not new.  For
   years, separated overlay and logical (virtual) networking have
   existed, allowing multiple connectivity services to be deployed over
   a single physical network comprised of single or multiple layers.
   However, several key differences exist that differentiate overlay and
   virtual networking from network slicing.

   A transport network slice construct provides an end-to-end logical
   network, often with compute functions and utilising shared underlying
   (physical or virtual) network resources.  This logical network is
   separated from other, often concurrent, logical networks each with
   independent control and management, and each of which can be created
   or modified on demand.

   At one end of the spectrum, a virtual private wire or a virtual
   private network (VPN) may be used to build a network slice. In these
   cases, the network slices do not require the service provider to
   isolate network resources for the provision of the service - the
   service is "virtual".

   At the other end of the spectrum there may be a detailed description
   of a complex service that will meet the needs of a set of
   applications with connectivity and service function requirements that
   may include compute resource, storage capability, and access to
   content. Such a service may be requested dynamically (that is,
   instantiated when an application needs it, and released when the
   application no longer needs it), and modified as the needs of the
   application change.

   Each example represents a self-contained network that must be
   flexible enough to simultaneously accommodate diverse business-driven
   use cases from multiple players on a common network infrastructure.

   This document outlines the application of the ACTN architecture
   [actn-framework] and enabling technologies to provide transport
   network slicing in an IETF technology network.  It describes how the
   ACTN functional components can be used to support model-driven
   partitioning of variable-sized bandwidth to facilitate network
   sharing and virtualization.  Furthermore, the use of model-based
   interfaces to dynamically request the instantiation of virtual
   networks could be extended to encompass requesting and instantiation
   of specific service functions (which may be both physical and/or
   virtual), and to partition network resources such as compute
   resource, storage capability, and access to content.

   In an IETF context, there are works in progress that have some
   bearing with network slicing such as Enhanced VPN (VPN+) and DetNet. Both
   works are an independent work in their own scope while



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   This document highlights how the ACTN approach might be extended to
   address these other requirements of network slicing where TE is
   required.

1.1. Terminology

   Resource: Any features that can be delivered, including connectivity,
   compute, storage, and content delivery.

   Service Functions (SFs): Components that provide specific function
   within a network.  SFs are often combined in a specific sequence,
   service function chain, to deliver services.

   Infrastructure Resources: The hardware and necessary software for
   hosting and connecting SFs. These resources may include computing
   hardware, storage capacity, network resources (e.g. links and
   switching/routing devices enabling network connectivity), and
   physical assets for radio access.

   Service Provider: A server network or collection of server
   networks.

   Consumer: Any application, client network, or customer of a network
   provider.

   Service Level Agreement (SLA): An agreement between a consumer and
   network provider that describes the quality with which features
   and functions are to be delivered.  It may include measures of
   bandwidth, latency, and jitter; the types of service (such as the
   network service functions or billing) to be executed; the location,
   nature, and quantities of services (such as the amount and location
   of compute resources and the accelerators require).

   Network Slice: An agreement between a consumer and a service
   provider to deliver network resources according to a specific service
   level agreement. A slice could span multiple technology (e.g., radio,
   transport and cloud) and administrative domains.

   IETF Technology: A TE network slice or transport network slice.

2. Requirements for Network Slicing

   The concept of network slicing is considered a key capability for
   future networks and, to serve customers with a wide variety of
   different service needs, in term of latency, reliability, capacity,
   and service function specific capabilities.

   This section outlines the key capabilities required, and further
   discussed in [ngmn-network-slicing], [network-slice-5g],
   [3gpp.28.801] and [onf-tr526], to realise network slicing in an IETF
   technology network.


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2.1. Resource Slicing

   For network slicing, it is important to consider both infrastructure
   resources and servic functions.  This allows a flexible approach to
   deliver a range of services both by partitioning (slicing) the
   available network resources to present them for use by a consumer,
   but also by providing instances of SFs at the right locations and in
   the correct chaining logic, with access to the necessary hardware,
   including specific compute and storage resources.

   Mapping of resources to slices may 1-to-1, or resources may be shared
   among multiple slices.

2.2. Network and Function Virtualization

   Virtualization is the abstraction of resources where the abstraction
   is made available for use by an operations entity, for example, by
   the Network Management Station (NMS) of a consumer network.  The
   resources to be virtualized can be physical or already virtualized,
   supporting a recursive pattern with different abstraction layers.
   Therefore, Virtualization is critical for network slicing as it
   enables effective resource sharing between network slices.

   Just as server virtualization makes virtual machines (VMs)
   independent of the underlying physical hardware, network
   Virtualization enables the creation of multiple isolated virtual
   networks that are completely decoupled from the underlying physical
   network, and can safely run on top of it.

2.3. Resource Isolation

   Isolation of data and traffic is a major requirement that must be
   satisfied for certain applications to operate in concurrent network
   slices on a common shared underlying infrastructure. Therefore,
   isolation must be understood in terms of:

   o Performance: Each slice is defined to meet specific service
     requirements, usually expressed in the form of Key Performance
     Indicators (KPIs).  Performance isolation requires that service
     delivery on one network slice is not adversely impacted by
     congestion and performance levels of other slices;

   o Security: Attacks or faults occurring in one slice must not have an
     impact on other slices, or customer flows are not only isolated on
     network edge, but multiple customer traffic is not mixed across the
     core of the network. Moreover, each slice must have independent
     security functions that prevent unauthorised entities to have read
     or write access to slice-specific configuration, management,
     accounting information, and able to record any of these attempts,
     whether authorised or not;



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   o Management: Each slice must be independently viewed, utilised and
     managed as a separate network.

2.4. Control and Orchestration

   Orchestration is the overriding control method for network slicing.
   We may define orchestration as combining and coordinating multiple
   control methods to provide an operational mechanism that can deliver
   services and control underlying resources.  In a network slicing
   environment, an orchestrator is needed to coordinate disparate
   processes and resources for creating, managing, and deploying the
   end-to-end service. Two scenarios are outlined below where
   orchestration would be required:

   1. Multi-domain Orchestration: Managing connectivity setup of the
      transport service, across multiple administrative domains;

   2. End-to-end Orchestration: Combining resources for an "end-to-end
      service (e.g., transport connectivity with firewalling and
      guaranteed bandwidth and minimum delay for premium radio users
      (spanning multiple domains).

   In addition, 3GPP has also developed Release 14 "Study on
   management and orchestration of network slicing for next generation
   network" [3gpp.28.801], which defines an information model where the
   network slice as well as physical and virtualized network functions
   belong to the network operator domain, while the virtualized
   resources belong to another domain operated by a Virtualization
   infrastructure service provider.



3. Abstraction and Control of Traffic Engineered (TE) Networks (ACTN)

   The framework for ACTN [actn-framework] includes a reference
   architecture that has been adapted for Figure 1 in this document, it
   describes the functional entities and methods for the coordination of
   resources across multiple domains, to provide end-to-end services,
   components include:

   o Customer Network Controller (CNC);

   o Multi-domain Service Coordinator (MDSC);

   o Physical Network Controller (PNC).







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      ---------                 ---------                  ---------
      | CNC-A |                 | CNC-B |                  | CNC-C |
      ---------                 ---------                  ---------
            \                       |                        /
             \__________            |-CMI I/F     __________/
                        \           |            /
                         -------------------------
                         |         MDSC          |
                         -------------------------
                          /      /    |         \
                         /      /     |-MPI I/F  \
                        /      /      |           \
                  -------   -------  -------       -------
                  | PNC |   | PNC |  | PNC |       | PNC |
                  -------   -------  -------       -------

   CMI - (CNC-MDSC Interface )
   MPI - (MDSC-PNC Interface)

                         Figure 1: ACTN Hierarchy

   ACTN facilitates end-to-end connections and provides them to the
   user. The ACTN framework highlights how:

   o Abstraction of the underlying network resources are provided to
     higher-layer applications and customers;

   o Virtualization of underlying resources, whose selection criterion
     is the allocation of those resources for the customer, application,
     or service;

   o Creation of a virtualized environment allowing operators to view
     and control multi-domain networks as a single virtualized network;

   o The presentation to customers of networks as a virtual network via
     open and programmable interfaces.

   The ACTN managed infrastructure are traffic engineered network
   resources, which may include:

   o Statistical packet bandwidth;

   o Physical forwarding plane sources, such as: wavelengths and
     time slots;

   o Forwarding and cross connect capabilities.

   The ACTN type of network virtualization provides customers and
   applications (tenants) to utilise and independently control



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   allocated virtual network resources as if resources as if they
   were physically their own resource. The ACTN network is "sliced",
   with tenants being given a different partial and abstracted
   topology view of the physical underlying network. The capabilities
   that ACTN provides to enable slicing are outlined in Section 2
   (Requirements for Network Slicing).


3.1. ACTN Virtual Network as a "Network Slice"

   To support multiple clients each with its own view of and control
   of the server network, a network operator needs to partition (or
   "slice") the network resources.  The resulting slices can be
   assigned to each client for guaranteed usage which is a step
   further than shared use of common network resources. See
   [actn-vn] for detailed ACTN VN and VNS.

   An ACTN Virtual Network (VN) is a client view that may be considered
   a "network slice" of the ACTN managed infrastructure, and is
   presented by the ACTN provider as a set of abstracted resources.

   Depending on the agreement between client and provider various VN
   operations and VN views are possible.

   o Network Slice Creation: A VN could be pre-configured and created
     via static or dynamic request and negotiation between customer and
     provider. It must meet the specified SLA attributes which satisfy
     the customer's objectives.

   o Network Slice Operations: The network slice may be further modified
     and deleted based on customer request to request changes in the
     network resources reserved for the customer, and used to construct
     the network slice. The customer can further act upon the network
     slice to manage traffic flow across the network slice.

   o Network Slice View: The VN topology from a customer point of view.
     These may be a variety of tunnels, or an entire VN topology. Such
     connections may comprise of customer end points, access links,
     intra domain paths and inter-domain links.

   Primitives (capabilities and messages) have been provided to support
   the different ACTN network control functions that will enable network
   slicing. These include: topology request/query, VN service request,
   path computation and connection control, VN service policy
   negotiation, enforcement, routing options. [actn-info]

3.2. Examples of ACTN Delivering Types of Network Slices

   In examples below the ACTN framework is used to provide


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   control, management and orchestration for the network slice
   life-cycle, the connectivity . These dynamic and highly flexible,
   end-to-end and dedicated network slices utilising common physical
   infrastructure, and according to vertical-specific requirements.

   The rest of this section provides three examples of using ACTN to
   achieve different scenarios of ACTN for network slicing. All three
   scenarios can be scaled up in capacity or be subject to topology
   changes as well as changes from customer requirements perspective.

3.2.1. ACTN Used for Virtual Private Line Model

   ACTN Provides virtual connections between multiple customer
   locations, requested via Virtual Private Line (VPL) requester
   (CNC-A). Benefits of this model include:

   o Automated: the service set-up and operation is network provider
     managed;

   o Virtual: the private line is seamlessly extended from customers
     Site A (vCE1 to vCE2) and Site B (vCE2 to vCE3) across the
     ACTN-managed WAN to Site C;

   o Agile: on-demand where the customer needs connectivity and
     fully adjustable bandwidth.

                     (Customer VPL Request)
                                |
                            ---------
                            | CNC-A |
   Boundary                 ---------
   Between  ====================|====================
   Customer &                   |
   Network Provider          --------
                             | MDSC |
                             --------
                              __|__
        Site A               ( PNC )              Site B
         ------             (       )             ------
         |vCE1|=============( Phys. )=============|vCE2|
         ------              ( Net )              ------
               \              -----               /
                \               ||               /
                 \              ||              /
            VPL 1 \__           ||           __/ VPL 2
                     \          ||          /
                      \         ||         /
                       \      ------     /
                        ------|vCE3|-----
                              ------
                              Site C

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               Figure 2: Virtual Private Line Model

3.2.2. ACTN Used for VPN Delivery Model

   ACTN Provides VPN connections between multiple sites, requested via
   a VPN requestor (CNC-A), which is managed by the customer
   themselves. The CNC will then interact with the network providers
   MDSC. Benefits of this model include:


   o Provides edge-to-edge VPN multi-access connection;
   o Mostly network provider managed, with some flexibility delegated to
     the customer managed CNC.

          ----------------                            ----------------
          | Site-A Users |___________     ____________| Site-B Users |
          ----------------           |   |            ----------------
                                    -------
                                    |CNC-A|
   Boundary                         -------
   Between   ==========================|==========================
   Customer &                          |
   Network Provider                    |
                                       |
                                ---------------
                                |     MDSC    |
                                ---------------
                      _________/       |       \__________
                     /                 |                  \
                    /                  |                   \
               ---------           ---------            ---------
               |  PNC  |           |  PNC  |            |  PNC  |
               ---------           ---------            ---------
                  |                    |                 /
                  |                    |                /
                -----                -----           -----
               (     )              (     )         (     )
  <Site A>----( Phys. )------------( Phys. )-------( Phys. )----<Site B>
               ( Net )              ( Net )         ( Net )
                -----                -----           -----

                              Figure 3: VPN Model


3.2.3. ACTN Used to Deliver a Virtual Customer Network

   In this example ACTN provides a virtual network resource to the





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   customer. This resource is customer managed. Empowering the tenant
   to control allocated slice  (recursively). Benefits of this model
   include:

   o The MDSC provides the topology as part of the customer view so
     that the customer can control their network slice to fit their
     needs;

   o Resource isolation, each customer network slice is fixed and will
     not be affected by changes to other customer network slices;

   o Applications can interact with their assigned network slice
     directly, the customer may implement their own network control
     method and traffic prioritization, manage their own addressing
     scheme, and further slice their assigned network resource;

   o The network slice may also include specific capability nodes,
     delivered as Physical Network Functions (PNFs) or Virtual Network
     Functions (VNFs).
                                             ___________
                  ---------------           (  Network  )
                  |    CNC      |---------->(  Slice 2  )
                  ---------------          _(_________  )
               ---------------            (  Network  )_)
               |    CNC      |----------->(  Slice 1  ) ^
               ---------------            (           ) :
                     ^                    (___________) :
                     |                        ^    ^    :
   Boundary          |                        :    :    :
   Between ==========|========================:====:====:========
   Customer &        |                        :    :    :
   Network Provider  |                        :    :    :
                     v                        :    :    :
               ---------------                :    :....:
               |    MDSC     |                :         :
               ---------------                :         :
                     ^                     ---^------    ...
                     |                    (          )      .
                     v                   (  Physical  )      .
                 ----------------         ( Network  )        .
                 |     PNC      |<------>  (        )      ---^------
               ---------------- |           --------      (          )
               |              |--                        (  Physical  )
               |    PNC       |<------------------------->( Network  )
               ---------------                             (        )
                                                            --------
                   Figure 4: Network Slicing






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3.3. Network Slice Service Mapping from TE to ACTN VN Models

   The role of TE-service mapping model [te-service-mapping] is to
   create a binding relationship across a Layer-3 Service Model [l3sm],
   Layer-2 Service Model and TE Tunnel model, via a generic ACTN Virtual
   Network (VN) model [actn-vn].

   The ACTN VN YANG model is a generic virtual network service
   model that allows customers (internal or external) to create a VN
   that meets the customer's service objective with various
   constraints.

   The TE-service mapping model is needed to bind L3VPN specific
   service model with TE-specific parameters. This binding
   will facilitate a seamless service operation with underlay-TE
   network visibility. The TE-service model developed in this document
   can also be extended to support other services including L2SM, and
   future transport network service models.

         -----------          ---------------         ------------
         |  L3SM   | <------> |             | <-----> | TE-Tunnel|
         -----------          |             |         |  Model   |
                              | TE-Service  |         ------^-----
                              |Mapping Model|               |
         -----------          |             |         ------v-----
         |  L2SM   | <------> |             | <-----> | ACTN VN  |
         -----------          ---------------         |  Model   |
                                                      ------------
          Figure 5: TE-Service Mapping ([te-service-mapping])

   Editors note - We plan to provide a list of models available and
   their relationships/dependencies. We will also provide a vertical
   hierarchy of how these models may be used between functional
   components in ACTN.

3.4.  ACTN VN KPI telemetry Models

   The role of ACTN VN KPI telemetry model [actn-pm-telemetry] is
   to provide YANG models so that customer can define key
   performance monitoring data relevant for its VN/network slicing
   via the YANG subscription model.

   Key characteristics of [actn-pm-telemetry] include:

   o an ability to provide scalable VN-level telemetry aggregation
     based on customer-subscription model for key performance
     parameters defined by the customer;

   o an ability to facilitate proactive re-optimization and
     reconfiguration of VNs/Netork Slices based on network
     autonomic traffic engineering scaling configuration
     mechanism.


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5. IANA Considerations

   This document makes no requests for action by IANA.


6. Security Considerations

   Network slicing involves the control of network resources in order
   to meet the service requirements of consumers.  In some deployment
   models, the consumer is able to directly request modification in
   the behaviour of resources owned and operated by a service provider.
   Such changes could significantly affect the service provider's
   ability to provide services to other consumers.  Furthermore, the
   resources allocated for or consumed by a consumer will normally be
   billable by the service provider.

   Therefore, it is crucial that the mechanisms used in any network
   slicing system allow for authentication of requests, security of
   those requests, and tracking of resource allocations.

   It should also be noted that while the partitioning or slicing of
   resources is virtual, the consumers expect and require that there
   is no risk of leakage of data from one slice to another, no
   transfer of knowledge of the structure or even existence of other
   slices, and that changes to one slice (under the control of one
   consumer) should not have detrimental effects on the operation of
   other slices (whether under control of different or the same
   consumers) beyond the limits allowed within the SLA.  Thus, slices
   are assumed to be private and to provide the appearance of genuine
   physical connectivity.

   ACTN operates using the [netconf] or [restconf] protocols and
   assumes the security characteristics of those protocols.
   Deployment models for ACTN should fully explore the authentication
   and other security aspects before networks start to carry live
   traffic.


7. Acknowledgements

   Thanks to Qin Wu, Andy Jones, Ramon Casellas, and Gert Grammel for
   their insight and useful discussions about network slicing.

8.  References

8.1. Normative References

8.2. Informative References





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   [ngmn-network-slicing]
              NGMN, "Description of Network Slicing Concept", 1 2016,
              <https://www.ngmn.org/uploads/
              media/160113_Network_Slicing_v1_0.pdf>.

   [3gpp.28.801]
              3GPP, "Study on management and orchestration of network
              slicing for next generation network", 3GPP TR 28.801
              0.4.0, 1 2017,
              <http://www.3gpp.org/ftp/Specs/html-info/28801.htm>.

   [network-slice-5g]
              "Network Slicing for 5G with SDN/NFV: Concepts,
              Architectures and Challenges", Jose Ordonez-Lucena,
              Pablo Ameigeiras, Diego Lopez, Juan J. Ramos-Munoz,
              Javier Lorca, Jesus Folgueira, IEEE Communications
              Magazine 55, March 2017

   [onf-tr526]
              ONF TR-526, "Applying SDN Architecture to 5G Slicing",
              April 2016.

   [actn-framework]
              Ceccarelli, D. and Y. Lee, "Framework for Abstraction and
              Control of Traffic Engineered Networks", draft-ietf-teas-
              actn-framework, work in progress, February 2017.

   [te-service-mapping]
              Y. Lee, D. Dhody, and D. Ceccarelli, "Traffic Engineering
              and Service Mapping Yang Model",
              draft-lee-teas-te-service-mapping-yang, work in progress.

   [actn-vn] Y. Lee (Editor), "A Yang Data Model for ACTN VN
             Operation", draft-lee-teas-actn-vn-yang, work in progress.

   [actn-info] Y. Lee, S. Belotti (Editors), "Information Model for
             Abstraction and Control of TE Networks (ACTN)", draft-ietf-
             teas-actn-info-model, work in progress.

   [actn-pm-elemetry] Y. Lee, et al, "YANG models for ACTN TE
             Performance Monitoring Telemetry and Network Autonomics",
             draft-lee- teas-actn-pm-telemetry-autonomics, work in
             progress.

   [l3sm]    Litkowski, S., Tomotaki, L., and K. Ogaki, "YANG Data
             Model for L3VPN Service Delivery", RFC 8049, February 2017








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   [netconf] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
             and A. Bierman, Ed., "Network Configuration Protocol
             (NETCONF)", RFC 6241.

   [restconf] A. Bierman, M. Bjorklund, and K. Watsen, "RESTCONF
             Protocol", draft-ietf-netconf-restconf, work in progress.

   [sf-topology] I. Bryskin, et al, "Use Cases for SF Aware Topology
           Models", draft-bryskin-teas-use-cases-sf-aware-topo-model, work
           in progress.

   [vpn+]    S. Bryant and J. Dong, "Enhanced Virtual Private Networks
           (VPN+)", draft-bryant-rtgwg-enhanced-vpn, work in progress.


9. Contributors

   The following people contributed text to this document.

   Adrian Farrel
   Email: afarrel@juniper.net

   Mohamed Boucadair
   Email: mohamed.boucadair@orange.com

   Sergio Belotti
   Email: sergio.belotti@nokia.com

   Daniele Ceccarelli
   Email: daniele.ceccarelli@ericsson.com

   Haomian Zheng
   Email: zhenghaomian@huawei.com

Authors' Addresses

   Daniel King
   Email: daniel@olddog.co.uk

   Young Lee
   Email: leeyoung@huawei.com













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