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Versions: 00 01 02

Network Working Group                                         I. Bryskin
Internet-Draft                                       Huawei Technologies
Intended status: Informational                                 V. Beeram
Expires: August 30, 2019                                Juniper Networks
                                                                 T. Saad
                                                       Cisco Systems Inc
                                                                  X. Liu
                                                          Volta Networks
                                                                  Y. Lee
                                                     Huawei Technologies
                                                       February 26, 2019


    Basic YANG Model for Steering Client Services To Server Tunnels
          draft-bryskin-teas-service-tunnel-steering-model-02

Abstract

   This document describes a YANG data model for managing pools of
   transport tunnels and steering client services on them.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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

   This Internet-Draft will expire on August 30, 2019.

Copyright Notice

   Copyright (c) 2019 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



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   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
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Prefixes in Data Node Names . . . . . . . . . . . . . . .   4
   2.  Explicit vs. Implicit Service2tunnel Mapping. Steering
       Services to Transport Tunnel Pools  . . . . . . . . . . . . .   4
   3.  The purpose of the model  . . . . . . . . . . . . . . . . . .   5
   4.  Model Design  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Tree Structure  . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  YANG Modules  . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Client layer services/signals are normally mapped onto carrying them
   across the network transport tunnels via client/server layer
   adaptation relationships.  Such relationships are usually modeled as
   multi-layer topologies, whereas tunnels set up in underlay (server)
   topologies support links in respective overlay (client) topologies.
   In this respect having a link in a client topology means that the
   client layer traffic could be forwarded between link termination
   points (LTPs) terminating the link on opposite sides by the
   supporting tunnel(s) provisioned in the server layer topology.

   This said there are numerous use cases in which describing the client
   service to server tunnel bindings via the topology formalism is
   impractical.  Below are some examples of such use cases:

   o  Mapping client services onto tunnels within the same network
      layer, for example, mapping L3 VPNs or MPLS-SR services onto IP
      MPLS tunnels;

   o  Mapping client services onto tunnels provisioned in the highest
      layer topology supported by the network.  For example, mapping
      L2VPNs or E(V)PL services onto IP MPLS tunnels provisioned in an
      IP network;



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   o  Mapping client services to tunnels provisioned in separate network
      layers at the network's access points.  Consider, for example, an
      OTN/ODUk network that is used to carry client signals of, say, 20
      different types (e.g.  Ethernet, SDH, FKON, etc.) entering and
      exiting the network over client facing interfaces.  Although it is
      possible to describe such a network as a 21-layer TE topology with
      the OTN/ODUk topology serving each of the 20 client layer
      topologies [I-D.ietf-teas-yang-te-topo], such a description would
      be verbose, cumbersome, difficult to expand to accommodate
      additional client signals and unnecessary, because the client
      layer topologies would have zero switching flexibility inside the
      network (i.e. contain only unrelated links connecting access
      points across respective layer networks), and all what is required
      to know from the point of view of a management application is what
      ODUk tunnels are established or required, which client signals the
      tunnels could carry and at which network border nodes and how the
      client signals could be bound (i.e. adopted) to the tunnels.

   It is worth noting that such non-topological client-service-to-
   server-tunnel mapping almost always happens on network border nodes.
   However, there are also important use cases where such a mapping is
   required in the middle of the network.  One such use case is
   controlling on IP/MPLS FRR PLRs which LSPs are mapped onto which
   backup tunnels.

   It is important to bear in mind that service2tunnel mappings could be
   very complex: large number of instances of services of the same or
   different types (possibly governed by different models) could be
   mapped on the same set of tunnels, with the latter being set in
   different network layers and of either TE or non-TE nature, P2P or
   P2MP or MP2MP type.  Furthermore, the mappings could be hierarchical:
   tunnels carrying services could be clients of other tunnels.

   Despite of the differences of transport tunnels and of services they
   carry the srvice2tunnel mappings could be modeled in a simple uniform
   way.  Access to a data store of such mappings could be beneficial to
   network management applications.  It would be possible, for example,
   to discover which services depend on which tunnels, which services
   will be affected if a given tunnel goes out of service, how many more
   services could be placed onto a given TE tunnel without the latter
   violating its TE commitments (such as bandwidth and delay).  It would
   be also possible to demand in a single request moving numerous
   (ranges of) service instances from one set of tunnels to another.

   This document defines a YANG data model for facilitating said
   xervice2tunnel mappings.





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   The YANG model in this document conforms to the Network Management
   Datastore Architecture (NMDA) [RFC8342].

1.1.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14, [RFC2119].

   The following terms are defined in [RFC7950] and are not redefined
   here:

   o  augment

   o  data model

   o  data node

1.2.  Tree Diagrams

   A simplified graphical representation of the data model is presented
   in this document, by using the tree format defined in [RFC8340].

1.3.  Prefixes in Data Node Names

   In this document, names of data nodes, actions, and other data model
   objects are often used without a prefix, as long as it is clear from
   the context in which YANG module each name is defined.  Otherwise,
   names are prefixed using the standard prefix associated with the
   corresponding YANG module, as shown in Table 1.

         +----------+-----------------+-------------------------+
         | Prefix   | YANG module     | Reference               |
         +----------+-----------------+-------------------------+
         | inet     | ietf-inet-types | [RFC6991]               |
         | te-types | ietf-te-types   | [I-D.ietf-teas-yang-te] |
         +----------+-----------------+-------------------------+

             Table 1: Prefixes and Corresponding YANG Modules

2.  Explicit vs. Implicit Service2tunnel Mapping.  Steering Services to
    Transport Tunnel Pools

   There are use cases in which client services require hard separation
   of the transport carrying them from the transport carrying other
   services.  However, environment in which the services may share the
   same transport tunnels is far more common.  For this reason the model



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   defined in this document suggests replacing (or at least augmenting)
   the explicit service2tunnel mapping configuration (in which the
   tunnels are referred to by their IDs/names) with an implicit mapping.
   Specifically, the model introduces the notion of tunnel pool.  A
   tunnel pool could be referred to by its network unique color and
   requires a service2tunnel mapping configuration to specify the tunnel
   pool color(s) instead of tunnel IDs/names.  The model governs tunnel
   pool data store independently from the services steered on the
   tunnels.  It is assumed (although not required) that the tunnels -
   constituents/components of a tunnel pool - are of the same type,
   provisioned using a common template.  Importantly they could be
   dynamically added to/removed from the pool without necessitating
   service2tunnel mapping re-configuration.  Such a service to tunnel
   pool steering approach has the following advantages:

   o  Scalability and efficiency: pool component bandwidth utilization
      could be monitored, tunnels could be added to/removed from the
      pool if/when detected that current component bandwidth utilization
      has crossed certain thresholds.  This allows for a very efficient
      network resource utilization and obviates the network management
      application from a very difficult task of service to tunnel
      mapping planning;

   o  Automation and elasticity: pool component attributes could be
      modified - bandwidth auto-adjusted, protection added, delay
      constrained, etc.. The tunnels could be completely or partially
      replaced with tunnels of different types (e.g.  TE vs. non-TE, P2P
      vs. P2MP, etc.) or even provisioned in different network layers
      (OTN/ODUk tunnels replacing IP TE tunnels).  Importantly, all such
      modifications do not require service2tunell mapping re-
      configurations as long as the modified or new tunnels remain
      within the same tunnel pool(s);

   o  Transparency: new service sites supported by additional PEs could
      be added without service2tunnel mapping re-configuration.

3.  The purpose of the model

   The model is targeted to facilitate for network management
   applications, such as service orchestrators, the control of pools of
   transport tunnels and steering onto them client services
   independently of network technology/layer specifics of both the
   services and the tunnels.  The model could be applied to/implemented
   on physical devices, such as IP routers, as well as on abstract
   topology nodes.  Furthermore, the model could be supported by a
   network (domain) controller, such as ACTN PNC, to act as a proxy
   server on behalf of any network element/node (physical or abstract)
   under its control.



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4.  Model Design

   The data store described/governed by the model is comprised of a
   single top level list - TunnelPools.  A TunnelPool, list element, is
   a container describing a set of transport tunnels (presumably with
   similar characteristics) identified by a network unique ID (color).

   The TunnelPool container has the following fields:

   o  Color [uint32 list key];

   o  Tunnels list;

   o  Services list.

   The Tunnels list describes the pool constituents - active transport
   tunnels.  The list members - Tunnel containers - include the
   following information:

   o  tunnel type [e.g.  P2P-TE, P2MP-TE, SR-TE, SR P2P, LDP P2P, LDP
      MP2MP, GRE, PBB, etc]

   o  tunnel type specific tunnel ID [provided that a data store of the
      tunnel type, e.g.  TE tunnels, is supported, the tunnelID allows
      for the management application to look up the tunnel in question
      to obtain detailed information about the tunnel];

   o  topology ID [ identifies the topology over which the tunnel's
      connection paths are defined];

   o  tunnel encapsulation [e.g.  MPLS label stack, Ethernet STAGs, GRE
      header, PBB header, etc].

   The Services list describes services currently steered on the tunnel
   pool.  The list members - Service containers - have the following
   attributes:

   o  service type [e.g. fixed/transparent, L3VPN, L2VPN, EVPN, ELINE,
      EPL, EVPL, L1VPN, ACTN VN, etc.];

   o  service type specific service ID [provided that a data store of
      the service type, e.g.  L2VPN, is supported, the service ID allows
      for the management application to look up the service in question
      to obtain detailed information about the service];

   o  client ports (source/destination node LTPs over which the service
      enters/exits the node/network, relevant only for fixed/transparent
      services);



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   o  service encapsulation [e.g.  MPLS label stack, Ethernet CTAGs,
      etc.] - for service multiplexing/de-multiplexing on/from a
      statistically shared tunnel].

5.  Tree Structure


   module: ietf-tunnel-steering
     +--rw tunnel-pools
        +--rw tunnel-pool* [color]
           +--rw color          uint32
           +--rw description?   string
           +--rw service* [service-type id]
           |  +--rw service-type     identityref
           |  +--rw id               string
           |  +--rw encapsulation
           |  |  +--rw type?    identityref
           |  |  +--rw value?   binary
           |  +--rw access-point* [node-address link-termination-point]
           |     +--rw node-address              inet:ip-address
           |     +--rw link-termination-point    string
           |     +--rw direction?                enumeration
           +--rw tunnel*
                   [provider-id client-id topology-id tunnel-type source
    destination tunnel-id]
              +--rw provider-id      te-types:te-global-id
              +--rw client-id        te-types:te-global-id
              +--rw topology-id      te-types:te-topology-id
              +--rw tunnel-type      identityref
              +--rw source           inet:ip-address
              +--rw destination      inet:ip-address
              +--rw tunnel-id        binary
              +--rw encapsulation
                 +--rw type?    identityref
                 +--rw value?   binary



6.  YANG Modules


   <CODE BEGINS> file "ietf-tunnel-steering@2019-02-15.yang"
   module ietf-tunnel-steering {
     yang-version 1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tunnel-steering";

     prefix "tnl-steer";




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     import ietf-inet-types {
       prefix inet;
     }

     import ietf-te-types {
       prefix "te-types";
     }

     organization
       "IETF Traffic Engineering Architecture and Signaling (TEAS)
        Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/teas/>
        WG List:  <mailto:teas@ietf.org>

        Editors:  Igor Bryskin
                  <mailto:Igor.Bryskin@huawei.com>

        Editor:   Vishnu Pavan Beeram
                  <mailto:vbeeram@juniper.net>

        Editor:   Tarek Saad
                  <mailto:tsaad@cisco.com>

        Editor:   Xufeng Liu
                  <mailto:xufeng.liu.ietf@gmail.com>

        Editor:   Young Lee
                  <mailto:leeyoung@huawei.com> ";

     description
       "This data model is for steering client service to server
        tunnels.

        Copyright (c) 2018 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).";

     revision 2019-02-15 {
       description "Initial revision";
       reference "TBD";



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     }

     /*
      * Typedefs
      */

     /*
      * Identities
      */
     identity service-type {
       description "Base identity for client service type.";
     }
     identity service-type-l3vpn {
       base service-type;
       description
         "L3VPN service.";
     }
     identity service-type-l2vpn {
       base service-type;
       description
         "L2VPN service.";
     }
     identity service-type-evpn {
       base service-type;
       description
         "EVPN service.";
     }
     identity service-type-eline {
       base service-type;
       description
         "ELINE service.";
     }
     identity service-type-epl {
       base service-type;
       description
         "EPL service.";
     }
     identity service-type-evpl {
       base service-type;
       description
         "EVPL service.";
     }
     identity service-type-l1vpn {
       base service-type;
       description
         "L1VPN service.";
     }
     identity service-type-actn-vn {



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       base service-type;
       description
         "ACTN VN service.";
     }
     identity service-type-transparent {
       base service-type;
       description
         "Transparent LAN service.";
     }

     identity tunnel-type {
       description "Base identity for tunnel type.";
     }
     identity tunnel-type-te-p2p {
       base tunnel-type;
       description
         "TE point-to-point tunnel type.";
     }
     identity tunnel-type-te-p2mp {
       base tunnel-type;
       description
         "TE point-to-multipoint tunnel type.";
       reference "RFC4875";
     }
     identity tunnel-type-te-sr {
       base tunnel-type;
       description
         "Segment Rouging TE tunnel type.";
     }
     identity tunnel-type-sr {
       base tunnel-type;
       description
         "Segment Rouging tunnel type.";
     }
     identity tunnel-type-ldp-p2p {
       base tunnel-type;
       description
         "LDP point-to-point tunnel type.";
     }
     identity tunnel-type-ldp-mp2mp {
       base tunnel-type;
       description
         "Multicast LDP multipoint-to-multipoint tunnel type.";
     }
     identity tunnel-type-gre {
       base tunnel-type;
       description
         "GRE tunnel type.";



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     }
     identity tunnel-type-pbb {
       base tunnel-type;
       description
         "PBB tunnel type.";
     }

     identity service-encapsulation-type {
       description "Base identity for tunnel encapsulation.";
     }
     identity service-encapsulation-type-mpls-label {
       base service-encapsulation-type;
       description
         "Encapsulated by MPLS label stack, as an inner lable to
          identify the customer service.";
     }
     identity service-encapsulation-type-ethernet-c-tag {
       base service-encapsulation-type;
       description
         "Encapsulated by Ethernet C-TAG, to identify the customer
          service.";
     }

     identity tunnel-encapsulation-type {
       description "Base identity for tunnel encapsulation.";
     }
     identity tunnel-encapsulation-type-mpls-label {
       base tunnel-encapsulation-type;
       description
         "Encapsulated by MPLS label stack, as an outer label to
          be pushed into the tunnel.";
     }
     identity tunnel-encapsulation-type-ethernet-s-tag {
       base tunnel-encapsulation-type;
       description
         "Encapsulated by Ethernet S-TAG.";
     }
     identity tunnel-encapsulation-type-pbb {
       base tunnel-encapsulation-type;
       description
         "Encapsulated by PBB header.";
     }
     identity tunnel-encapsulation-type-gre {
       base tunnel-encapsulation-type;
       description
         "Encapsulated by GRE header.";
     }




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     /*
      * Groupings
      */

     /*
      * Configuration data and operational state data nodes
      */
     container tunnel-pools {
       description
         "A list of mappings that steer client services to transport
          tunnel pools. The tunnel pools are managed independently from
          the services steered on them.";

       list tunnel-pool {
         key "color";
         description
           "A set of transport tunnels (presumably with similar
            characteristics) identified by a network unique ID, named
            'color'.";
         leaf color {
           type uint32;
           description
             "Unique ID of a tunnel pool.";
         }
         leaf description {
           type string;
           description
             "Client provided description of the tunnel pool.";
         }
         list service {
           key "service-type id";
           description
             "A list of client services that are steered on this tunnel
              pool.";
           leaf service-type {
             type identityref {
               base service-type;
             }
             description
               "Service type required by the client.";
           }
           leaf id {
             type string;
             description
               "Unique ID of a client service for the specified
                service type.";
           }
           container encapsulation {



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             description
               "The encapsulation information used to identify the
                customer service for multiplexing over shared tunnels.";
             leaf type {
               type identityref {
                 base service-encapsulation-type;
               }
               description
                 "The encapsulation type used to identify the customer
                  service for multiplexing over shared tunnels.";
             }
             leaf value {
               type binary;
               description
                 "The encapsulation value pushed to the tunnel to
                  identify this service.
                  If not specified, the system decides what
                  value to be used for multiplexing.";
             }
           }
           list access-point {
             key "node-address link-termination-point";
             description
               "A list of client ports (Link Termination Points) for the
                service to enter or exist.";
             leaf node-address {
               type inet:ip-address;
               description
                 "Node over which the service enters or exists.";
             }
             leaf link-termination-point {
               type string;
               description
                 "Client port (Link Termination Point) over which the
                  service enters or exits.";
             }
             leaf direction {
               type enumeration {
                 enum "in" {
                   description "The service enters to the network.";
                 }
                 enum "out" {
                   description "The service exists from the network.";
                 }
                 enum "in-out" {
                   description
                     "The service enters to and exists from the
                      network.";



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                 }
               }
               description
                 "Whether the service enters to or exits from the
                  network.";
             }
           }
         }
         list tunnel {
           key "provider-id client-id topology-id tunnel-type source "
             + "destination tunnel-id";
           description
             "A list of tunnels in the tunnel pool.";

           leaf provider-id {
             type te-types:te-global-id;
             description
               "An identifier to uniquely identify a provider.";
           }
           leaf client-id {
             type te-types:te-global-id;
             description
               "An identifier to uniquely identify a client.";
           }
           leaf topology-id {
             type te-types:te-topology-id;
             description
               "It is presumed that a datastore will contain many
                topologies. To distinguish between topologies it is
                vital to have UNIQUE topology identifiers.";
           }
           leaf tunnel-type {
             type identityref {
               base tunnel-type;
             }
             description
               "Tunnel type based on constructing technologies and
                multipoint types, including P2P-TE, P2MP-TE, SR-TE,
                SR P2P, LDP P2P, LDP MP2MP, GRE, PBB, etc";
           }
           leaf source {
             type inet:ip-address;
             description
               "For a p2p or p2mp tunnel, this is the source address;
                for a mp2mp tunnel, this is the root address.";
             reference "RFC3209, RFC4875, RFC6388, RFC7582.";
           }
           leaf destination {



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             type inet:ip-address;
             description
               "For a p2p tunnel, this is the tunnel endpoint address
                extracted from SESSION object;
                for a p2mp tunnel, this identifies the destination
                group, or p2mp-id;
                for a mp2mp tunnel identified by root and opaque-value,
                this value is set to '0.0.0.0'.";
             reference "RFC3209, RFC4875, RFC6388, RFC7582.";
           }
           leaf tunnel-id {
             type binary;
             description
               "For a p2p or p2mp tunnel, this is the tunnel identifier
                used in the SESSION that remains constant over the life
                of the tunnel;
                for a mp2mp tunnel, this is the opaque-value in the
                FEC element.";
             reference "RFC3209, RFC4875, RFC6388, RFC7582.";
           }
           container encapsulation {
             description
               "The encapsulation information used by the tunnel.";
             leaf type {
               type identityref {
                 base service-encapsulation-type;
               }
               description
                 "The encapsulation type used by the tunnel.";
             }
             leaf value {
               type binary;
               description
                 "The encapsulation value pushed to the tunnel data to
                  identify the traffic in this tunnel.
                  If not specified, the system decides what
                  value to be used.";
             }
           }
         }
       }
     }
   }
   <CODE ENDS>







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7.  IANA Considerations

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number (and remove this note).

   This document registers the following namespace URIs in the IETF XML
   registry [RFC3688]:

   --------------------------------------------------------------------
   URI: urn:ietf:params:xml:ns:yang:ietf-tunnel-steering
   Registrant Contact: The IESG.
   XML: N/A, the requested URI is an XML namespace.
   --------------------------------------------------------------------

   This document registers the following YANG modules in the YANG Module
   Names registry [RFC7950]:

   --------------------------------------------------------------------
   name:         ietf-tunnel-steering
   namespace:    urn:ietf:params:xml:ns:yang:ietf-tunnel-steering
   prefix:       tnl-steer
   reference:    RFC XXXX
   --------------------------------------------------------------------

8.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC5246].

   The NETCONF access control model [RFC6536] provides the means to
   restrict access for particular NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   /tunnel-pools/tunnel-pool



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      This subtree specifies a list of tunnel pools.  Modifying the
      configurations cause interruption to related services and tunnels.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   /tunnel-pools/tunnel-pool
      Unauthorized access to this subtree can disclose the information
      of related services and tunnels.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <https://www.rfc-editor.org/info/rfc6536>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [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>.



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   [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>.

   [I-D.ietf-teas-yang-te-topo]
              Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Dios, "YANG Data Model for Traffic Engineering (TE)
              Topologies", draft-ietf-teas-yang-te-topo-19 (work in
              progress), February 2019.

   [I-D.ietf-teas-yang-te]
              Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin,
              "A YANG Data Model for Traffic Engineering Tunnels and
              Interfaces", draft-ietf-teas-yang-te-19 (work in
              progress), February 2019.

9.2.  Informative References

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

Authors' Addresses

   Igor Bryskin
   Huawei Technologies

   EMail: Igor.Bryskin@huawei.com


   Vishnu Pavan Beeram
   Juniper Networks

   EMail: vbeeram@juniper.net


   Tarek Saad
   Cisco Systems Inc

   EMail: tsaad@cisco.com






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   Xufeng Liu
   Volta Networks

   EMail: xufeng.liu.ietf@gmail.com


   Young Lee
   Huawei Technologies

   EMail: leeyoung@huawei.com









































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