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Versions: (draft-zheng-netmod-tacacs-yang) 00 01

Network Working Group                                           G. Zheng
Internet-Draft                                                   M. Wang
Intended status: Standards Track                                   B. Wu
Expires: September 11, 2019                                       Huawei
                                                          March 10, 2019


  Yang data model for Terminal Access Controller Access Control System
                                  Plus
                   draft-zheng-opsawg-tacacs-yang-01

Abstract

   This document defines two YANG modules that augment the System data
   model defined in the [RFC 7317] with TACACS+ client model and
   additional AAA model.  The data model of Terminal Access Controller
   Access Control System Plus (TACACS+) client allows the configuration
   of TACACS+ servers for centralized Authentication, Authorization and
   Accouting.  While the current system model only supports
   authentication configuration, the additional AAA model allows system
   authorization and accouting configuration.

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

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 September 11, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
   3.  TACACSPLUS Client Model . . . . . . . . . . . . . . . . . . .   4
   4.  AAA Model Augmentation  . . . . . . . . . . . . . . . . . . .   5
     4.1.  User Authorization Model  . . . . . . . . . . . . . . . .   6
     4.2.  User Accounting Model . . . . . . . . . . . . . . . . . .   6
   5.  TACACS+ Module  . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  AAA Module  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   This document defines two YANG modules that augment the System data
   model defined in the [RFC 7317] with TACACS+ client model and
   additional AAA model.  The data model of Terminal Access Controller
   Access Control System Plus (TACACS+) client allows the configuration
   of TACACS+ servers for centralized Authentication, Authorization and
   Accouting.  While the current system model only supports
   authentication configuration, the additional AAA model allows system
   authorization and accouting configuration.

   TACACS+ provides Device Administration for routers, network access
   servers and other networked computing devices via one or more
   centralized servers which is defined inthe TACACS+ Protocol.
   [I-D.ietf-opsawg-tacacs]

   A YANG Data Model for System Management [RFC7317]defines two YANG
   features to support local or RADIUS authentication:

   o  User Authentication Model: Define a list of usernames and
      passwords and control the order in which local or RADIUS
      authentication is used.



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   o  RADIUS Client Model: Defines a list of RADIUS server that a device
      used.

   Since TACACS+ is also used for device management and the feature is
   not contained in the system model, this document defines a YANG data
   model that allows users to configure TACACS + client functions on a
   device.

   Additionally, to support full AAA feature, the "ietf-aaa" YANG module
   defined in this document provides user authorization model and user
   accouting model.  The additional AAA model is intended to be used
   together with the authentication feature of the System model, to
   authorize what services that a user is allowed to use, and to
   maintain a record of the actions performed when a user logging on.

   The YANG models can be used with network management protocols such as
   NETCONF[RFC6241] to install, manipulate, and delete the configuration
   of network devices.

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

2.  Conventions used in this document

   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
   BCP14, [RFC2119], [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following terms are defined in [RFC6241] and are used in this
   specification:

   o  client

   o  configuration data

   o  server

   o  state data

   The following terms are defined in [RFC7950] and are used in this
   specification:

   o  augment

   o  data model




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   o  data node

   The terminology for describing YANG data models is found in
   [RFC7950].

2.1.  Tree Diagrams

   Tree diagrams used in this document follow the notation defined in
   [RFC8340].

3.  TACACSPLUS Client Model

   This model is used to configure TACACS+ client on the device to
   support deployment scenarios with centralized authentication,
   authorization, and accounting servers.  Authentication is used to
   validates a user's name and password, authorization allows the user
   to access and execute commands at various command levels assigned to
   the user and accounting keeps track of the activity of a user who has
   accessed the device.

   The ietf-tacacs module is intended to augment the "/sys:system" path
   defined in the ietf-system module with "tacacs" grouping.  Therefore,
   a device can use local, Remote Authentication Dial In User Service
   (RADIUS), or Terminal Access Controller Access Control System Plus
   (TACACS+) to validate users who attempt to access the router by
   several mechanisms, e.g. a command line interface or a web-based user
   interface.

   The "server" list is directly under the "tacacs" container, which is
   is to hold a list of different TACACS+ server and use server-type to
   distinguish the three protocols.  The list of servers is for
   redundancy purpose.

   The "statistics" container under the "server list" is to record
   session statistics and usage information during user access which
   include the amount of data a user has sent and/or received during a
   session.

   The data model for tacacs has the following structure:












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module: ietf-aaa-tacacs
  augment /sys:system:
    +--rw tacacs {tacacs}?
       +--rw server* [name]
       |  +--rw name                 string
       |  +--rw server-type?         enumeration
       |  +--rw address              inet:host
       |  +--rw port?                inet:port-number
       |  +--rw shared-secret        string
       |  +--rw source-ip?           inet:ip-address
       |  +--rw single-connection?   boolean
       |  +--rw network-instance?    -> /ni:network-instances/network-instance/name
       |  +--ro statistics
       |     +--ro connection-opens?      yang:counter64
       |     +--ro connection-closes?     yang:counter64
       |     +--ro connection-aborts?     yang:counter64
       |     +--ro connection-failures?   yang:counter64
       |     +--ro connection-timeouts?   yang:counter64
       |     +--ro messages-sent?         yang:counter64
       |     +--ro messages-received?     yang:counter64
       |     +--ro errors-received?       yang:counter64
       +--rw options
          +--rw timeout?   uint16

4.  AAA Model Augmentation

   This document augments the system model with authorization model and
   accouting model to support full AAA feature.

   For the authentication model, if the NETCONF server advertises the
   "tacacs" feature, the device also supports user authentication using
   TACACSPLUS.  For NETCONF transport protocols that support password
   authentication, the leaf-list "user-authentication-order" is used to
   control if TACACSPLUS password authentication should be used.

   For the authorization model and accouting model, the extended AAA
   data model has the following structure:














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   module: ietf-system-aaa
     augment /sys:system:
       +--rw authorization {authorization}?
       |  +--rw user-authorization-order*   identityref
       |  +--rw events
       |     +--rw event* [event-type]
       |        +--rw event-type    identityref
       +--rw accouting {accouting}?
          +--rw user-accouting-order*   identityref
          +--rw events
             +--rw event* [event-type]
                +--rw event-type    identityref
                +--rw record?       enumeration

4.1.  User Authorization Model

   Following authentication, a user must gain authorization for doing
   certain tasks.  For instance, the user may try to issue commands.
   The authorization process determines whether the user has the
   authority to issue such commands.

   This document defines two optional authorization YANG features:
   "local-users" and "tacacs", which the server advertises to indicate
   support for configuring local users on the device and support for
   using TACACSPLUS for authorization, respectively.

   In addition, an authorization parameter is defined to indicate a
   specific authorization event, and an event can be added by defining
   other event identifiers.  Currently,
   "aaa_authorization_event_command" is used to determine whether the
   user is allowed to run commands.

4.2.  User Accounting Model

   Accounting is used to record the authorization information and
   accouting specific information such as start and stop times and
   resource usage information.

   This document defines two optional accouting YANG features: "local-
   users" and "tacacs", which the server advertises to indicate support
   for configuring local users on the device and support for using
   TACACSPLUS for accouting, respectively.

   Two accouting parameters are defined to indicate specific accouting
   event and also the record type.

   o  "event type": "aaa_accounting_event_command" is defined to record
      commands issued by the user.



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   o  "record": Start records indicate that a accouting service is about
      to begin.  Stop records indicate that a service has just
      terminated.

5.  TACACS+ Module

   <CODE BEGINS> file "ietf-aaa-tacacs@2019-03-06.yang"

 module ietf-aaa-tacacs {
   yang-version 1.1;
   namespace "urn:ietf:params:xml:ns:yang:ietf-aaa-tacacs";
   prefix aaa-tcs;

   import ietf-inet-types {
     prefix inet;
     reference "RFC 6991: Common YANG Data Types";
   }
   import ietf-yang-types {
     prefix yang;
     reference "RFC 6991: Common YANG Data Types";
   }
   import ietf-network-instance {
     prefix ni;
     reference "draft-ietf-rtgwg-ni-model-12: YANG Model for
     Network Instances";
   }
   import ietf-system {
     prefix sys;
     reference "RFC 7317: A YANG Data Model for System Management";
   }
   import ietf-netconf-acm {
     prefix nacm;
   }

   organization
     "IETF Opsawg (Operations and Management Area Working Group)";
   contact
     "WG Web:   <http://tools.ietf.org/wg/opsawg/>
      WG List:  <mailto:opsawg@ietf.org>

      Editor:   Guangying Zheng
                <mailto:zhengguangying@huawei.com>";
   description
     "This module provides configuration of TACACS+ client.

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




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      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).

      This version of this YANG module is part of RFC XXXX; see the RFC
       itself for full legal notices.";

   revision 2019-03-06 {
     description
       "Initial revision.";
     reference "foo";
   }

   feature tacacs {
     description
       "Indicates that the device can be configured as a TACACSPLUS
        client.";
     reference "draft-ietf-opsawg-tacacs-11: The TACACSPLUS Protocol";
   }



   grouping statistics {
     description
       "Grouping for statistics attributes";
     container statistics {
       config false;
       description
         "A collection of server-related statistics objects";
       leaf connection-opens {
         type yang:counter64;
         description
           "Number of new connection requests sent to the server, e.g.
            socket open";
       }
       leaf connection-closes {
         type yang:counter64;
         description
           "Number of connection close requests sent to the server, e.g.
            socket close";
       }
       leaf connection-aborts {
         type yang:counter64;
         description
           "Number of aborted connections to the server.  These do



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            not include connections that are close gracefully.";
       }
       leaf connection-failures {
         type yang:counter64;
         description
           "Number of connection failures to the server";
       }
       leaf connection-timeouts {
         type yang:counter64;
         description
           "Number of connection timeouts to the server";
       }
       leaf messages-sent {
         type yang:counter64;
         description
           "Number of messages sent to the server";
       }
       leaf messages-received {
         type yang:counter64;
         description
           "Number of messages received by the server";
       }
       leaf errors-received {
         type yang:counter64;
         description
           "Number of error messages received from the server";
       }
     }
   }

   grouping tacacs {
     description
       "Grouping for tacacs attributes";
     container tacacs {
       if-feature "tacacs";
       description
         "Container for TACACS+ configurations and operations.";
       list server {
         key "name";
         ordered-by user;
         description
           "List of TACACS+ servers used by the device

              When the TACACS client is invoked by a calling
              application, it sends the query to the first server in
              this list.  If no response has been received within
              'timeout' seconds, the client continues with the next
              server in the list.  If no response is received from any



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              server, the client continues with the first server again.
              When the client has traversed the list 'attempts' times
              without receiving any response, it gives up and returns an
              error to the calling application.";
         leaf name {
           type string;
           description
             "An arbitrary name for the TACACS+ server.";
         }
         leaf server-type {
           type enumeration {
             enum authentication {
               description
                 "The server is an authentication server.";
             }
             enum authorization {
               description
                 "The server is an authorization server.";
             }
             enum accounting {
               description
                 "The server is an accounting server.";
             }
           }
           description
             "Server type: authentication/authorization/accounting.";
         }
         leaf address {
           type inet:host;
           mandatory true;
           description
             "The address of the TACACS+ server.";
         }
         leaf port {
           type inet:port-number;
           default "49";
           description
             "The port number of TACACSPLUS Server port.";
         }
         leaf shared-secret {
           type string;
           mandatory true;
           nacm:default-deny-all;
           description
             "The shared secret, which is known to both the
              TACACS client and server.TACACS+ server administrators
              SHOULD configure secret keys of minimum
              16 characters length.";



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           reference "tacacs protocol:";
         }
         leaf source-ip {
           type inet:ip-address;
           description
             "Source IP address for a TACACS+ server.";
         }
         leaf single-connection {
           type boolean;
           default "false";
           description
             "Whether the single connection mode is enabled for the
              server. By default, the single connection mode is
             disabled.";
         }
         leaf network-instance {
           type leafref {
             path "/ni:network-instances/ni:network-instance/ni:name";
           }
           description
             "Configure the vpn-instance name.";
         }
         uses statistics;
       }
       container options {
         description
           "TACACS+ client options.";
         leaf timeout {
           type uint16 {
             range "1..300";
           }
           units "seconds";
           default "5";
           description
             "The number of seconds the device will wait for a
              response from each TACACS+ server before trying with a
              different server.";
         }
       }
     }
   }

   augment "/sys:system" {
     description
       "Augment the system model with authorization and accounting
          attribuets
        Augment the system model with the tacacs model";
     uses tacacs;



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   }
 }

   <CODE ENDS>

6.  AAA Module

   <CODE BEGINS> file "ietf-system-aaa@2019-03-06.yang"

 module ietf-system-aaa {
   yang-version 1.1;
   namespace "urn:ietf:params:xml:ns:yang:ietf-system-aaa";
   prefix sys-aaa;


   import ietf-system {
     prefix sys;
     reference "RFC 7317: A YANG Data Model for System Management";
   }
   import ietf-netconf-acm {
     prefix nacm;
   }

   organization
     "IETF Opsawg (Operations and Management Area Working Group)";
   contact
     "WG Web:   <http://tools.ietf.org/wg/opsawg/>
      WG List:  <mailto:opsawg@ietf.org>

      Editor:   Guangying Zheng
                <mailto:zhengguangying@huawei.com>";
   description
     "This module provides configuration of system AAA.

      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).

      This version of this YANG module is part of RFC XXXX; see the RFC
       itself for full legal notices.";

   revision 2019-03-06 {



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     description
       "Initial revision.";
     reference "foo";
   }

   feature authorization {
     description
       "Indicates that the device supports configuration of
        user authorization.";
   }

   feature accouting {
     description
       "Indicates that the device supports configuration of
        user accouting.";
   }

   identity authorization-method {
     description
       "Base identity for user authorization methods.";
   }

   identity accouting-method {
     description
       "Base identity for user accouting methods.";
   }

   identity tacacs {
     base sys:authentication-method;
     base authorization-method;
     base accouting-method;
     description
       "Indicates AAA operation using TACACS+.";
     reference "draft-ietf-opsawg-tacacs-11: The TACACS+ Protocol";
   }

   identity local-users {
     base sys:authentication-method;
     base authorization-method;
     base accouting-method;
     description
       "Indicates accouting of locally
        configured users.";
   }

   identity aaa_accounting_event_type {
     description
       "Base identity for specifying events types that should be



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        sent to AAA server for accounting";
   }

   identity aaa_accounting_event_command {
     base aaa_accounting_event_type;
     description
       "Specifies interactive command events for AAA accounting";
   }

   identity aaa_authorization_event_type {
     description
       "Base identity for specifying activities that should be
        sent to AAA server for authorization";
   }

   identity aaa_authorization_event_command {
     base aaa_authorization_event_type;
     description
       "Specifies interactive command events for AAA authorization";
   }

   augment "/sys:system" {
     description
       "Augment the system model with authorization and accounting
          attribuets
        Augment the system model with the tacacs model";
     container authorization {
       nacm:default-deny-write;
       if-feature "authorization";
       description
         "The authorization configuration subtree.";
       leaf-list user-authorization-order {
         type identityref {
           base authorization-method;
         }
         ordered-by user;
         description
           "When the device authorize a user, it tries the authorization
            methods in this leaf-list in order.  If authorization with
            one method fails, the next method is used. If no method
            succeeds, the user is denied access.

            If the 'tacacs-authentication' feature is advertised by
            the NETCONF server, the 'tacacs' identity can be added to
            this list.
            If the 'local-users' feature is advertised by the
            NETCONF server, the 'local-users' identity can be
            added to this list.";



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       }
       container events {
         description
           "The container contains an set of authorization events";
         list event {
           key "event-type";
           description
             "List of events of AAA authorization";
           leaf event-type {
             type identityref {
               base aaa_authorization_event_type;
             }
             description
               "The type of event to record at the AAA authorization
                server";
           }
         }
       }
     }
     container accouting {
       nacm:default-deny-write;
       if-feature "accouting";
       description
         "The accouting configuration subtree.";
       leaf-list user-accouting-order {
         type identityref {
           base accouting-method;
         }
         ordered-by user;
         description
           "When the device audit a user with a password,
            it tries the accouting methods in this leaf-list in
            order. The accouting method may be specified as TACACS+
            servers, or the local.";
       }
       container events {
         description
           "The container contains an set of accouting events";
         list event {
           key "event-type";
           description
             "List of events of accounting";
           leaf event-type {
             type identityref {
               base aaa_accounting_event_type;
             }
             description
               "The type of activity to record at the AAA accounting



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                server";
           }
           leaf record {
             type enumeration {
               enum start_stop {
                 description
                   "Send START record to the accounting server at the
                    beginning of the activity, and STOP record at the
                    end of the activity.";
               }
               enum stop {
                 description
                   "Send STOP record to the accounting server when the
                    user activity completes";
               }
             }
             description
               "Type of record to send to the accounting server for this
                activity type";
           }
         }
       }
     }
   }
 }

   <CODE ENDS>

7.  Security Considerations

   The YANG module defined in this document 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 [RFC8446].

   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.



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   This document describes the use of TACACS+ for purposes of
   authentication, authorization and accouting, it is vulnerable to all
   of the threats that are present in TACACS+ applications.  For a
   discussion of such threats, see Section 9 of the TACACS+ Protocol
   [I-D.ietf-opsawg-tacacs].

8.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registration is
   requested to be made:

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



   This document registers a YANG module in the YANG Module Names
   registry [RFC7950].

        Name: ietf-tacacs
               Namespace: urn:ietf:params:xml:ns:yang: ietf-tacacs
               Prefix: tcs
               Reference: RFC XXXX

9.  Normative References

   [I-D.ietf-opsawg-tacacs]
              Dahm, T., Ota, A., dcmgash@cisco.com, d., Carrel, D., and
              L. Grant, "The TACACS+ Protocol", draft-ietf-opsawg-
              tacacs-12 (work in progress), December 2018.

   [RFC1492]  Finseth, C., "An Access Control Protocol, Sometimes Called
              TACACS", RFC 1492, DOI 10.17487/RFC1492, July 1993,
              <https://www.rfc-editor.org/info/rfc1492>.

   [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>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.






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   [RFC6021]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6021, DOI 10.17487/RFC6021, October 2010,
              <https://www.rfc-editor.org/info/rfc6021>.

   [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>.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <https://www.rfc-editor.org/info/rfc7317>.

   [RFC792]   Postel, J., "Internet Control Message Protocol", RFC 792,
              September 1981.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.






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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

Authors' Addresses

   Guangying Zheng
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: zhengguangying@huawei.com


   Michael Wang
   Huawei Technologies, Co., Ltd
   101 Software Avenue, Yuhua District
   Nanjing  210012
   China

   Email: wangzitao@huawei.com


   Bo Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: lana.wubo@huawei.com




















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