NTP Working Group N. Wu
Internet-Draft D. Dhody
Intended status: Standards Track Huawei
Expires: June 20, 2019 A. Sinha
A. Kumar S N
RtBrick Inc.
Y. Zhao
Ericsson
December 17, 2018

A YANG Data Model for NTP
draft-ietf-ntp-yang-data-model-05

Abstract

This document defines a YANG data model for Network Time Protocol (NTP) implementations. The data model includes configuration data and state data.

Requirements Language

The key words "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] [RFC8174] when, and only when, they appear in all capitals, as shown here.

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 June 20, 2019.

Copyright Notice

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

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


Table of Contents

1. Introduction

This document defines a YANG [RFC7950] data model for Network Time Protocol [RFC5905] implementations.

The data model convers configuration of system parameters of NTP, such as access rules, authentication and VPN Routing and Forwarding (VRF) binding, and also associations of NTP in different modes and parameters of per-interface. It also provides information about running state of NTP implementations.

1.1. Operational State

NTP Operational State is included in the same tree as NTP configuration, consistent with Network Management Datastore Architecture [RFC8342]. NTP current state and statistics are also maintained in the operational state. Additionally, the operational state also include the associations state.

1.2. Terminology

The terminology used in this document is aligned to [RFC5905].

1.3. Tree Diagrams

A simplified graphical representation of the data model is used in this document. This document uses the graphical representation of data models defined in [RFC8340].

1.4. Prefixes in Data Node Names

In this document, names of data nodes 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.

Prefixes and corresponding YANG modules
Prefix YANG module Reference
yang ietf-yang-types [RFC6991]
inet ietf-inet-types [RFC6991]
if ietf-interfaces [RFC8343]
ianach iana-crypt-hash [RFC7317]
key-chain ietf-key-chain [RFC8177]
acl ietf-access-control-list [I-D.ietf-netmod-acl-model]
rt-types ietf-routing-types [RFC8294]

2. NTP data model

module: ietf-ntp
 +--rw ntp!
    +--rw port?                    inet:port-number {ntp-port}?
    +--rw refclock-master!
    |  +--rw master-stratum?   ntp-stratum
    +--rw authentication
    |  +--rw auth-enabled?          boolean
    |  +--rw authentication-keys* [key-id]
    |     +--rw key-id       uint32
    |     +--rw algorithm?   identityref
    |     +--rw key?         ianach:crypt-hash
    |     +--rw istrusted?   boolean
    +--rw access-rules
    |  +--rw access-rule* [access-mode]
    |     +--rw access-mode    access-mode
    |     +--rw acl?           -> /acl:acls/acl/name
    +--ro clock-state
    |  +--ro system-status
    |     +--ro clock-state                  ntp-clock-status
    |     +--ro clock-stratum                ntp-stratum
    |     +--ro clock-refid                  union
    |     +--ro associations-address?
    |     |       -> /ntp/associations/address
    |     +--ro associations-local-mode?
    |     |       -> /ntp/associations/local-mode
    |     +--ro associations-isconfigured?
    |     |       -> /ntp/associations/isconfigured
    |     +--ro nominal-freq                 decimal64
    |     +--ro actual-freq                  decimal64
    |     +--ro clock-precision              uint8
    |     +--ro clock-offset?                decimal64
    |     +--ro root-delay?                  decimal64
    |     +--ro root-dispersion?             decimal64
    |     +--ro reference-time?              yang:date-and-time
    |     +--ro sync-state                   ntp-sync-state
    +--rw unicast-configuration* [address type]
    |  +--rw address           inet:host
    |  +--rw type              unicast-configuration-type
    |  +--rw authentication
    |  |  +--rw (authentication-type)?
    |  |     +--:(symmetric-key)
    |  |        +--rw key-id?   leafref
    |  +--rw prefer?           boolean
    |  +--rw burst?            boolean
    |  +--rw iburst?           boolean
    |  +--rw source?           if:interface-ref
    |  +--rw minpoll?          ntp-minpoll
    |  +--rw maxpoll?          ntp-maxpoll
    |  +--rw port?             inet:port-number {ntp-port}?
    |  +--rw version?          ntp-version
    +--ro associations* [address local-mode isconfigured]
    |  +--ro address           inet:host
    |  +--ro local-mode        association-mode
    |  +--ro isconfigured      boolean
    |  +--ro stratum?          ntp-stratum
    |  +--ro refid?            union
    |  +--ro authentication?
    |  |       -> /ntp/authentication/authentication-keys/key-id
    |  +--ro prefer?           boolean
    |  +--ro peer-interface?   if:interface-ref
    |  +--ro minpoll?          ntp-minpoll
    |  +--ro maxpoll?          ntp-maxpoll
    |  +--ro port?             inet:port-number {ntp-port}?
    |  +--ro version?          ntp-version
    |  +--ro reach?            uint8
    |  +--ro unreach?          uint8
    |  +--ro poll?             uint8
    |  +--ro now?              uint32
    |  +--ro offset?           decimal64
    |  +--ro delay?            decimal64
    |  +--ro dispersion?       decimal64
    |  +--ro originate-time?   yang:date-and-time
    |  +--ro receive-time?     yang:date-and-time
    |  +--ro transmit-time?    yang:date-and-time
    |  +--ro input-time?       yang:date-and-time
    |  +--ro ntp-statistics
    |     +--ro packet-sent?        yang:counter32
    |     +--ro packet-sent-fail?   yang:counter32
    |     +--ro packet-received?    yang:counter32
    |     +--ro packet-dropped?     yang:counter32
    +--rw interfaces
    |  +--rw interface* [name]
    |     +--rw name                if:interface-ref
    |     +--rw broadcast-server!
    |     |  +--rw ttl?              uint8
    |     |  +--rw authentication
    |     |  |  +--rw (authentication-type)?
    |     |  |     +--:(symmetric-key)
    |     |  |        +--rw key-id?   leafref
    |     |  +--rw minpoll?          ntp-minpoll
    |     |  +--rw maxpoll?          ntp-maxpoll
    |     |  +--rw port?             inet:port-number {ntp-port}?
    |     |  +--rw version?          ntp-version
    |     +--rw broadcast-client!
    |     +--rw multicast-server* [address]
    |     |  +--rw address
    |     |  |       rt-types:ip-multicast-group-address
    |     |  +--rw ttl?              uint8
    |     |  +--rw authentication
    |     |  |  +--rw (authentication-type)?
    |     |  |     +--:(symmetric-key)
    |     |  |        +--rw key-id?   leafref
    |     |  +--rw minpoll?          ntp-minpoll
    |     |  +--rw maxpoll?          ntp-maxpoll
    |     |  +--rw port?             inet:port-number {ntp-port}?
    |     |  +--rw version?          ntp-version
    |     +--rw multicast-client* [address]
    |     |  +--rw address    rt-types:ip-multicast-group-address
    |     +--rw manycast-server* [address]
    |     |  +--rw address    rt-types:ip-multicast-group-address
    |     +--rw manycast-client* [address]
    |        +--rw address
    |        |       rt-types:ip-multicast-group-address
    |        +--rw authentication
    |        |  +--rw (authentication-type)?
    |        |     +--:(symmetric-key)
    |        |        +--rw key-id?   leafref
    |        +--rw ttl?              uint8
    |        +--rw minclock?         uint8
    |        +--rw maxclock?         uint8
    |        +--rw beacon?           uint8
    |        +--rw minpoll?          ntp-minpoll
    |        +--rw maxpoll?          ntp-maxpoll
    |        +--rw port?             inet:port-number {ntp-port}?
    |        +--rw version?          ntp-version
    +--ro ntp-statistics
       +--ro packet-sent?        yang:counter32
       +--ro packet-sent-fail?   yang:counter32
       +--ro packet-received?    yang:counter32
       +--ro packet-dropped?     yang:counter32

groupings:
authentication
    +---- (authentication-type)?
       +--:(symmetric-key)
          +---- key-id?
                  -> /ntp/authentication/authentication-keys/key-id

statistics
    +---- packet-sent?        yang:counter32
    +---- packet-sent-fail?   yang:counter32
    +---- packet-received?    yang:counter32
    +---- packet-dropped?     yang:counter32

authentication-key
    +---- key-id?      uint32
    +---- algorithm?   identityref
    +---- key?         ianach:crypt-hash
    +---- istrusted?   boolean

association-ref
    +---- associations-address?        -> /ntp/associations/address
    +---- associations-local-mode?     -> /ntp/associations/local-mode
    +---- associations-isconfigured?
            -> /ntp/associations/isconfigured

common-attributes
    +---- minpoll?   ntp-minpoll
    +---- maxpoll?   ntp-maxpoll
    +---- port?      inet:port-number {ntp-port}?
    +---- version?   ntp-version

     

This document defines the YANG module "ietf-ntp", which has the following structure:

This data model defines one top-level container which includes both the NTP configuration and the NTP running state including access rules, authentication, associations, unicast configurations, interfaces, system status and associations.

3. Relationship with NTPv4-MIB

If the device implements the NTPv4-MIB [RFC5907], data nodes from YANG module can be mapped to table entries in NTPv4-MIB.

The following tables list the YANG data nodes with corresponding objects in the NTPv4-MIB.

YANG NTP Configuration Data Nodes and Related NTPv4-MIB Objects

YANG data nodes in /ntp/clock-state/system-status NTPv4-MIB objects
clock-state ntpEntStatusCurrentMode
clock-stratum ntpEntStatusStratum
clock-refid ntpEntStatusActiveRefSourceId
ntpEntStatusActiveRefSourceName
clock-precision ntpEntTimePrecision
clock-offset ntpEntStatusActiveOffset
root-dispersion ntpEntStatusDispersion

YANG data nodes in /ntp/associations/ NTPv4-MIB objects
address ntpAssocAddressType
ntpAssocAddress
stratum ntpAssocStratum
refid ntpAssocRefId
offset ntpAssocOffset
delay ntpAssocStatusDelay
dispersion ntpAssocStatusDispersion
ntp-statistics/packet-sent ntpAssocStatOutPkts
ntp-statistics/packet-received ntpAssocStatInPkts
ntp-statistics/packet-dropped ntpAssocStatProtocolError

YANG NTP State Data Nodes and Related NTPv4-MIB Objects

4. Relationship with RFC 7317

This section describes the relationship with NTP definition in Section 3.2 System Time Management of [RFC7317] . YANG data nodes in /ntp/ also supports per-interface configurations which is not supported in /system/ntp. If the yang model defined in this document is implemented, then /system/ntp SHOULD NOT be used and MUST be ignored.

YANG data nodes in /ntp/ YANG data nodes in /system/ntp
ntp! enabled
unicast-configuration server
server/name
unicast-configuration/address server/transport/udp/address
unicast-configuration/port server/transport/udp/port
unicast-configuration/type server/association-type
unicast-configuration/iburst server/iburst
unicast-configuration/prefer server/prefer

YANG NTP Configuration Data Nodes and counterparts in RFC 7317 Objects

5. Access Rules

As per [RFC1305], NTP could include an access-control feature that prevents unauthorized access and controls which peers are allowed to update the local clock. Further it is useful to differentiate between the various kinds of access (such as peer or server; refer access-mode) and attach different acl-rule to each. For this, the YANG module allow such configuration via /ntp/access-rules. The access-rule itself is configured via [I-D.ietf-netmod-acl-model].

6. Key Management

As per [RFC1305], when authentication is enabled, NTP employs a crypto-checksum, computed by the sender and checked by the receiver, together with a set of predistributed algorithms, and cryptographic keys indexed by a key identifier included in the NTP message. This key-id is 32-bits unsigned integer that MUST be configured on the NTP peers before the authentication could be used. For this reason, this YANG modules allow such configuration via /ntp/authentication/authentication-keys/. Further at the time of configuration of NTP association (for example unicast-server), the key-id is specefied.

7. NTP YANG Module

<CODE BEGINS> file "ietf-ntp@2018-12-17.yang"
module ietf-ntp {

  yang-version 1.1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-ntp";

  prefix "ntp";

  import ietf-yang-types {
    prefix "yang";
    reference "RFC 6991";
  }

  import ietf-inet-types {
    prefix "inet";
    reference "RFC 6991";
  }

  import ietf-interfaces {
    prefix "if";
    reference "RFC 8343";
  }

  import iana-crypt-hash {
    prefix "ianach";
    reference "RFC 7317";
  }

  import ietf-key-chain {
    prefix "key-chain";
    reference "RFC 8177";
  }

  import ietf-access-control-list {
    prefix "acl";
    reference "RFC XXXX";
  }

  /* Note: The RFC Editor will replace XXXX with the number assigned
  to the RFC once draft-ietf-netmod-acl-model becomes an RFC.*/

  import ietf-routing-types {
    prefix "rt-types";
    reference "RFC 8294";

  }

  organization
    "IETF NTP (Network Time Protocol) Working Group";

  contact
    "WG Web:  <http://tools.ietf.org/wg/ntp/>
    WG List:  <mailto: ntpwg@lists.ntp.org
    Editor:   Eric Wu
              <mailto:eric.wu@huawei.com>
    Editor:   Anil Kumar S N
              <mailto:anil.ietf@gmail.com>
    Editor:   Yi Zhao
              <mailto:yi.z.zhao@ericsson.com>
    Editor:   Dhruv Dhody
              <mailto:dhruv.ietf@gmail.com>
    Editor:   Ankit Kumar Sinha
              <mailto:ankit.ietf@gmail.com>";
  description
    "This document defines a YANG data model for Network Time Protocol
    (NTP) implementations. The data model includes configuration data 
    and state data.

    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 YYYY;
    see the RFC itself for full legal notices.";

  revision 2018-12-17 {
    description
      "Updated revision.";
    reference
      "RFC YYYY: A YANG Data Model for NTP.";
  }

  /* Note: The RFC Editor will replace YYYY with the number assigned  
  to this document once it becomes an RFC.*/

  /* Typedef Definitions */

  typedef ntp-stratum {
    type uint8 {
      range "1..16";
    }
    description
      "The level of each server in the hierarchy is defined by
      a stratum. Primary servers are assigned with stratum
      one; secondary servers at each lower level are assigned with
      one stratum greater than the preceding level";
  }

  typedef ntp-version {
    type uint8 {
      range "1..4";
    }
    default "3";
    description
      "The current NTP version supported by corresponding
      association.";
  }

  typedef ntp-minpoll {
    type uint8 {
      range "4..17";
    }
    default "6";
    description
      "The minimum poll exponent for this NTP association.";
  }

  typedef ntp-maxpoll {
    type uint8 {
      range "4..17";
    }
    default "10";
    description
      "The maximum poll exponent for this NTP association.";
  }

  typedef access-mode {
    type enumeration {
      enum peer {
        value "0";
        description
          "Enables the full access authority. Both time
          request and control query can be performed
          on the local NTP service, and the local clock
          can be synchronized with the remote server.";
      }
      enum server {
        value "1";
        description
          "Enables the server access and query.
          Both time requests and control query can be
          performed on the local NTP service, but the
          local clock cannot be synchronized with the
          remote server.";
      }
      enum synchronization {
        value "2";
        description
          "Enables the server to access.
          Only time request can be performed on the
          local NTP service.";
      }
      enum query {
        value "3";
        description
          "Enables the maximum access limitation.
          Control query can be performed only on the
          local NTP service.";
      }
    }
    description
      "This defines NTP access modes.";
  }

  typedef unicast-configuration-type {
    type enumeration {
      enum server {
        value "0";
        description
          "Use client association mode. This device
          will not provide synchronization to the
          configured NTP server.";
      }
      enum peer {
        value "1";
        description
          "Use symmetric active association mode.
          This device may provide synchronization
          to the configured NTP server.";
      }
    }
    description
      "This defines NTP unicast mode of operation.";
  }
  typedef association-mode {
    type enumeration {
      enum client {
        value "0";
        description
          "Use client association mode(mode 3).
          This device will not provide synchronization
          to the configured NTP server.";
      }
      enum active {
        value "1";
        description
          "Use symmetric active association mode(mode 1).
          This device may synchronize with its NTP peer,
          or provide synchronization to configured NTP peer.";
      }
      enum passive {
        value "2";
        description
          "Use symmetric passive association mode(mode 2).
          This device has learned this association dynamically.
          This device may synchronize with its NTP peer.";
      }
      enum broadcast {
        value "3";
        description
          "Use broadcast mode(mode 5).
          This mode defines that its either working
          as broadcast-server or multicast-server.";
      }
      enum broadcast-client {
        value "4";
        description
          "This mode defines that its either working
          as broadcast-client or multicast-client.";
      }
    }
    description
      "The NTP association modes.";
  }

  typedef ntp-clock-status {
    type enumeration {
      enum synchronized {
        value "0";
        description
          "Indicates that the local clock has been
          synchronized with an NTP server or
          the reference clock.";
      }
      enum unsynchronized {
        value "1";
        description
          "Indicates that the local clock has not been
          synchronized with any NTP server.";
      }
    }
    description
      "This defines NTP clock status.";
  }

  typedef ntp-sync-state {
    type enumeration {
      enum clock-not-set {
        value "0";
        description
          "Indicates the clock is not updated.";
      }
      enum freq-set-by-cfg {
        value "1";
        description
          "Indicates the clock frequency is set by
          NTP configuration.";
      }
      enum clock-set {
        value "2";
        description
          "Indicates the clock is set.";
      }
      enum freq-not-determined {
        value "3";
        description
          "Indicates the clock is set but the frequency
          is not determined.";
      }
      enum clock-synchronized {
        value "4";
        description
          "Indicates that the clock is synchronized";
      }
      enum spike {
        value "5";
        description
          "Indicates a time difference of more than 128
          milliseconds is detected between NTP server
          and client clock. The clock change will take
          effect in XXX seconds.";
      }
    }
    description
      "This defines NTP clock sync states.";
  }

  /* features */
  feature ntp-port {
    description
      "Support for NTP port configuration";
    reference "RFC1305 - 3.2.7 Parameters";
  }

  feature authentication {
    description
      "Support for NTP symmetric key authentication";
    reference "RFC1305 - 3.2.6 Authentication Variables";
  }

  feature access-rules {
    description
      "Support for NTP access control";
    reference "RFC1305 - 3.6 Access Control Issues";
  }

  feature unicast-configuration {
    description
      "Support for NTP client/server or active/passive
      in unicast";
    reference "RFC1305 - 3.3 Modes of Operation";
  }

  feature broadcast-server {
    description
      "Support for broadcast server";
    reference "RFC1305 - 3.3 Modes of Operation";
  }

  feature broadcast-client {
    description
      "Support for broadcast client";
    reference "RFC1305 - 3.3 Modes of Operation";
  }

  feature multicast-server {
    description
      "Support for multicast server";
    reference "RFC1305 - 3.3 Modes of Operation";
  }

  feature multicast-client {
    description
      "Support for multicast client";
    reference "RFC1305 - 3.3 Modes of Operation";
  }

  feature manycast-server {
    description
      "Support for manycast server";
    reference "RFC5905 - 3.1 Dynamic Server Discovery";
  }

  feature manycast-client {
    description
      "Support for manycast client";
    reference "RFC5905 - 3.1 Dynamic Server Discovery";
  }

  /* Groupings */
  grouping authentication-key {
    description
      "To define an authentication key for a Network Time
      Protocol (NTP) time source.";
    leaf key-id {
      type uint32 {
        range "1..max";
      }
      description
        "Authentication key identifier.";
    }
    leaf algorithm {
      type identityref {
        base key-chain:crypto-algorithm;
      }
      description
        "Authentication algorithm.";
    }
    leaf key {
      type ianach:crypt-hash;
      description
        "The key";
    }
    leaf istrusted {
      type boolean;
      description
        "Key-id is trusted or not";
    }
  }

  grouping authentication {
    description
      "Authentication.";
    choice authentication-type {
      description
        "Type of authentication.";
      case symmetric-key {
        leaf key-id {
          type leafref {
            path "/ntp:ntp/ntp:authentication/"
            + "ntp:authentication-keys/ntp:key-id";
          }
          description
            "Authentication key id referenced in this
            association.";
        }
      }
    }
  }

  grouping statistics {
    description
      "NTP packet statistic.";
    leaf packet-sent {
      type yang:counter32;
      description
        "The total number of NTP packets delivered to the
        transport service by this NTP entity for this
        association.
        Discountinuities in the value of this counter can occur
        upon cold start or reinitialization of the NTP entity, the
        management system and at other times as indicated by
        discontinuities in the value of sysUpTime.";
    }
    leaf packet-sent-fail {
      type yang:counter32;
      description
        "The number of times NTP packets sending failed.";
    }
    leaf packet-received {
      type yang:counter32;
      description
        "The total number of NTP packets delivered to the
        NTP entity from this association.
        Discountinuities in the value of this counter can occur
        upon cold start or reinitialization of the NTP entity, the
        management system and at other times as indicated by
        discontinuities in the value of sysUpTime.";
    }
    leaf packet-dropped {
      type yang:counter32;
      description
        "The total number of NTP packets that were delivered
        to this NTP entity from this association and this entity
        was not able to process due to an NTP protocol error.
        Discountinuities in the value of this counter can occur
        upon cold start or reinitialization of the NTP entity, the
        management system and at other times as indicated by
        discontinuities in the value of sysUpTime.";
    }
  }

  grouping common-attributes {
    description
      "NTP common attributes for configuration.";
    leaf minpoll {
      type ntp-minpoll;
      description
        "The minimum poll interval used in this association.";
    }
    leaf maxpoll {
      type ntp-maxpoll;
      description
        "The maximum poll interval used in this association.";
    }
    leaf port {
      if-feature ntp-port;
      type inet:port-number {
        range "123 | 1025..max";
      }
      default "123";
      description
        "Specify the port used to send NTP packets.";
    }
    leaf version {
      type ntp-version;
      description
        "NTP version.";
    }
  }

  grouping association-ref {
    description
      "Reference to NTP association mode";
    leaf associations-address {
      type leafref {
        path "/ntp:ntp/ntp:associations/ntp:address";
      }
      description
        "Indicates the association's address
        which result in clock synchronization.";
    }
    leaf associations-local-mode {
      type leafref {
        path "/ntp:ntp/ntp:associations/ntp:local-mode";
      }
      description
        "Indicates the association's local-mode
        which result in clock synchronization.";
    }
    leaf associations-isconfigured {
      type leafref {
        path "/ntp:ntp/ntp:associations/"
        + "ntp:isconfigured";
      }
      description
        "The association was configured or dynamic 
        which result in clock synchronization.";
    }
  }

  /* Configuration data nodes */
  container ntp {
    presence
      "NTP is enabled and system should attempt to
      synchronize the system clock with an NTP server
      from the 'ntp/associations' list.";
    description
      "Configuration parameters for NTP.";
    leaf port {
      if-feature ntp-port;
      type inet:port-number {
        range "123 | 1025..max";
      }
      default "123";
      description
        "Specify the port used to send and receive NTP packets.";
    }
    container refclock-master {
      presence
        "NTP master clock is enabled.";
      description
        "Configures the local clock of this device as NTP server.";
      leaf master-stratum {
        type ntp-stratum;
        default "16";
        description
          "Stratum level from which NTP
          clients get their time synchronized.";
      }
    }
    container authentication {
      description
        "Configuration of authentication.";
      leaf auth-enabled {
        type boolean;
        default false;
        description
          "Controls whether NTP authentication is enabled
          or disabled on this device.";
      }
      list authentication-keys {
        key "key-id";
        uses authentication-key;
        description
          "List of authentication keys.";
      }
    }

    container access-rules {
      description
        "Configuration to control access to NTP service 
        by using NTP access-group feature.
        The access-mode identifies how the acl is 
        applied with NTP.";
      list access-rule {
        key "access-mode";
        description
          "List of access rules.";
        leaf access-mode {
          type access-mode;
          description
            "NTP access mode. The defination of each possible values:
            peer(0): Both time request and control query can be 
            performed.
            server(1): Enables the server access and query.
            synchronization(2): Enables the server access only.
            query(3): Enables control query only.";
        }
        leaf acl {
          type leafref {
            path "/acl:acls/acl:acl/acl:name";
          }
          description
            "Control access configuration to be used.";
        }
        reference
          "RFC 1305";
      }
    }

    container clock-state {
      config "false";
      description
        "Clock operational state of the NTP.";

      container system-status {
        description
          "System status of NTP.";
        leaf clock-state {
          type ntp-clock-status;
          mandatory true;
          description 
            "The state of system clock. The definition of each 
            possible value is:
            synchronized(0): Indicates local clock is synchronized.
            unsynchronized(1): Indicates local clock is not 
            synchronized.";
        }
        leaf clock-stratum {
          type ntp-stratum;
          mandatory true;
          description
            "The NTP entity's own stratum value. Should be a stratum 
            of syspeer + 1 (or 16 if no syspeer).";
        }
        leaf clock-refid {
          type union {
            type inet:ipv4-address;
            type binary {
              length "4";
            }
            type string {
              length "4";
            }
          }
          mandatory true;
          description
            "IPv4 address or first 32 bits of the MD5 hash of
            the IPv6 address or reference clock of the peer to
            which clock is synchronized.";
        }

        uses association-ref {
          description
            "Reference to Association.";
        }
        leaf nominal-freq {
          type decimal64 {
            fraction-digits 4;
          }
          units Hz;
          mandatory true;
          description
            "The nominal frequency of the
            local clock.";
        }
        leaf actual-freq {
          type decimal64 {
            fraction-digits 4;
          }
          units Hz;
          mandatory true;
          description
            "The actual frequency of the
            local clock.";
        }
        leaf clock-precision {
          type uint8;
          units Hz;
          mandatory true;
          description
            "Clock precision of this system in integer format 
            (prec=2^(-n)). A value of 5 would mean 2^-5 = 31.25 ms.";
        }
        leaf clock-offset {
          type decimal64 {
            fraction-digits 3;
          }
          units milliseconds;
          description
            "The time offset to the current selected reference time 
            source e.g., '0.032' or '1.232'.";
        }
        leaf root-delay {
          type decimal64 {
            fraction-digits 3;
          }
          units milliseconds;
          description
            "Total delay along the path to root clock.";
        }
        leaf root-dispersion {
          type decimal64 {
            fraction-digits 3;
          }
          units milliseconds;
          description
            "The dispersion between the local clock
            and the root clock, e.g., '6.927'.";
        }
        leaf reference-time {
          type yang:date-and-time;
          description
            "The reference timestamp.";
        }
        leaf sync-state {
          type ntp-sync-state;
          mandatory true;
          description
            "The synchronization status of
            the local clock.";
        }
      }
    }
    list unicast-configuration {
      key "address type";
      description
        "List of NTP unicast-configurations.";
      leaf address {
        type inet:host;
        description
          "Address of this association.";
      }
      leaf type {
        type unicast-configuration-type;
        description
          "Use client association mode.  This device
          will not provide synchronization to the
          configured NTP server.";
      }
      container authentication{
        description
          "Authentication used for this association.";
        uses authentication;
      }
      leaf prefer {
        type boolean;
        default "false";
        description
          "Whether this association is preferred or not.";
      }
      leaf burst {
        type boolean;
        default "false";
        description
          "If set, a series of packets are sent instead of a single
          packet within each synchronization interval to achieve faster
          synchronization.";
      }
      leaf iburst {
        type boolean;
        default "false";
        description
          "If set, a series of packets are sent instead of a single 
          packet within the initial synchronization interval to achieve
          faster initial synchronization.";
      }
      leaf source {
        type if:interface-ref;
        description
          "The interface whose IP address is used by this association
          as the source address.";
      }
      uses common-attributes {
        description
          "Common attributes like port, version, min and max
          poll.";
      }
    }
    list associations {
      key "address local-mode isconfigured";
      config "false";
      description
        "List of NTP associations. Here address, local-mode
        and isconfigured is required to uniquely identify
        a particular association. Lets take following examples - 

        1) If RT1 acting as broadcast server,
        and RT2 acting as broadcast client, then RT2
        will form dynamic association with address as RT1,
        local-mode as client and isconfigured as false.

        2) When RT2 is configured
        with unicast-server RT1, then RT2 will form
        association with address as RT1, local-mode as client
        and isconfigured as true. 

        Thus all 3 leaves are needed as key to unique identify
        the association.";
      leaf address {
        type inet:host;
        description
          "The address of this association. Represents the IP
          address of a unicast/multicast/broadcast address.";
      }
      leaf local-mode {
        type association-mode;
        description
          "Local mode of this NTP association.";
      }
      leaf isconfigured {
        type boolean;
        description
          "Indicates if this association is configured or
          dynamically learned.";
      }
      leaf stratum {
        type ntp-stratum;
        description
          "The association stratum value.";
      }
      leaf refid {
        type union {
          type inet:ipv4-address;
          type binary {
            length "4";
          }
          type string {
            length "4";
          }
        }
        description
          "The refclock driver ID, if available.
          -- a refclock driver ID like '127.127.1.0' for local clock 
             sync
          -- uni/multi/broadcast associations will look like '20.1.1.1'
          -- sync with primary source will look like 'DCN', 'NIST', 
             'ATOM'";
        reference
          "RFC 1305";
      }
      leaf authentication{
        type leafref {
          path "/ntp:ntp/ntp:authentication/"
          + "ntp:authentication-keys/ntp:key-id";
        }
        description
          "Authentication Key used for this association.";
      }
      leaf prefer {
        type boolean;
        default "false";
        description
          "Indicates if this association is preferred.";
      }
      leaf peer-interface {
        type if:interface-ref;
        description
          "The interface which is used for communication.";
      }
      uses common-attributes {
        description
          "Common attributes like port, version, min and
          max poll.";
      }
      leaf reach {
        type uint8;
        description
          "The reachability of the configured
          server or peer.";
      }
      leaf unreach {
        type uint8;
        description
          "The unreachability of the configured
          server or peer.";
      }
      leaf poll {
        type uint8;
        units seconds;
        description
          "The polling interval for current association";
      }
      leaf now {
        type uint32;
        units seconds;
        description
          "The time since the NTP packet was
          not received or last synchronized.";
      }
      leaf offset {
        type decimal64 {
          fraction-digits 3;
        }
        units milliseconds;
        description
          "The offset between the local clock
          and the peer clock, e.g., '0.032' or '1.232'";
      }
      leaf delay {
        type decimal64 {
          fraction-digits 3;
        }
        units milliseconds;
        description
          "The network delay between the local clock
          and the peer clock.";
      }
      leaf dispersion {
        type decimal64 {
          fraction-digits 3;
        }
        units milliseconds;
        description
          "The root dispersion between the local clock
           and the peer clock.";
      }
      leaf originate-time {
        type yang:date-and-time;
        description
          "This is the local time, in timestamp format,
          when latest NTP packet was sent to peer(T1).";
        reference
          "RFC 1305";
      }
      leaf receive-time {
        type yang:date-and-time;
        description
          "This is the local time, in timestamp format,
          when latest NTP packet arrived at peer(T2).
          If the peer becomes unreachable the value is set to zero.";
        reference
          "RFC 1305";
      }
      leaf transmit-time {
        type yang:date-and-time;
        description
          "This is the local time, in timestamp format,
          at which the NTP packet departed the peer(T3).
          If the peer becomes unreachable the value is set to zero.";
        reference
          "RFC 1305";
      }
      leaf input-time {
        type yang:date-and-time;
        description
          "This is the local time, in timestamp format,
          when the latest NTP message from the peer arrived(T4).
          If the peer becomes unreachable the value is set to zero.";
        reference
          "RFC 1305";
      }
      container ntp-statistics {
        description
          "Per Peer packet send and receive statistics.";
        uses statistics {
          description
            "NTP send and receive packet statistics.";
        }
      }
    }

    container interfaces {
      description
        "Configuration parameters for NTP interfaces.";
      list interface {
        key "name";
        description
          "List of interfaces.";
        leaf name {
          type if:interface-ref;
          description
            "The interface name.";
        }

        container broadcast-server {
          presence
            "NTP broadcast-server is configured";
          description
            "Configuration of broadcast server.";
          leaf ttl {
            type uint8;
            description
              "Specifies the time to live (TTL) for a
              broadcast packet.";
          }
          container authentication{
            description
              "Authentication used for this association.";
              uses authentication;
          }
          uses common-attributes {
            description
              "Common attribute like port, version, min and
              max poll.";
          }
        }

        container broadcast-client {
          presence
            "NTP broadcast-client is configured.";
          description
            "Configuration of broadcast-client.";
        }

        list multicast-server {
          key "address";
          description
            "Configuration of multicast server.";
          leaf address {
            type rt-types:ip-multicast-group-address;
            description
              "The IP address to send NTP multicast packets.";
          }
          leaf ttl {
            type uint8;
            description
              "Specifies the time to live (TTL) for a
              multicast packet.";
          }
          container authentication{
            description
              "Authentication used for this association.";
              uses authentication;
          }
          uses common-attributes {
            description
              "Common attributes like port, version, min and
              max poll.";
          }
        }
        list multicast-client {
          key "address";
          description
            "Configuration of multicast-client.";
          leaf address {
            type rt-types:ip-multicast-group-address;
            description
              "The IP address of the multicast group to
              join.";
          }
        }
        list manycast-server {
          key "address";
          description
            "Configuration of manycast server.";
          leaf address {
            type rt-types:ip-multicast-group-address;
            description
              "The multicast group IP address to receive
              manycast client messages.";
          }
          reference
            "RFC 5905";
        }
        list manycast-client {
          key "address";
          description
            "Configuration of manycast-client.";
          leaf address {
            type rt-types:ip-multicast-group-address;
            description
              "The group IP address that the manycast client
              broadcasts the request message to.";
          }
          container authentication{
            description
              "Authentication used for this association.";
            uses authentication;
          }
          leaf ttl {
            type uint8;
            description
              "Specifies the maximum time to live (TTL) for
              the expanding ring search.";
          }
          leaf minclock {
            type uint8;
            description
              "The minimum manycast survivors in this
              association.";
          }
          leaf maxclock {
            type uint8;
            description
              "The maximum manycast candidates in this
              association.";
          }
          leaf beacon {
            type uint8;
            description
              "The maximum interval between beacons in this
              association.";
          }
          uses common-attributes {
            description
              "Common attributes like port, version, min and
              max poll.";
          }
          reference
            "RFC 5905";
        }
      }
    }
    container ntp-statistics {
      config "false";
      description
        "Total NTP packet statistics.";
      uses statistics {
        description
          "NTP send and receive packet statistics.";
      }
    }
  }
}
<CODE ENDS>

8. Usage Example

8.1. Unicast association

Below is the example on how to configure a preferred unicast server present at 192.0.2.1 running at port 1025 with authentication-key 10 and version 4

  <edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <target>
      <running/>
    </target>
    <config>
      <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
        <unicast-configuration>
          <address>192.0.2.1</address>
          <type>server</type>
          <prefer>true</prefer>
          <version>4</version>
          <port>1025</port>
          <authentication>
            <symmetric-key>
              <key-id>10</key-id>
            </symmetric-key>
          </authentication>
        </unicast-configuration>
      </ntp>
    </config>
  </edit-config>

An example with IPv6 would used the an IPv6 address (say 2001:DB8::1) in the "address" leaf with no change in any other data tree.

Below is the example on how to get unicast configuration

<get>
  <filter type="subtree">
  <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:unicast-configuration>
      </sys:unicast-configuration>
  </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <unicast-configuration>
      <address>192.0.2.1</address>
      <type>server</type>
        <authentication>
          <symmetric-key>
            <key-id>10</key-id>
          </symmetric-key>
        </authentication>
      <prefer>true</prefer>
      <burst>false</burst>
      <iburst>true</iburst>
      <source/>
      <minpoll>6</minpoll>
      <maxpoll>10</maxpoll>
      <port>1025</port>
      <version>4</version>
      <stratum>9</stratum>
      <refid>20.1.1.1</refid>
      <reach>255</reach>
      <unreach>0</unreach>
      <poll>128</poll>
      <now>10</now>
      <offset>0.025</offset>
      <delay>0.5</delay>
      <dispersion>0.6</dispersion>
      <originate-time>10-10-2017 07:33:55.253 Z+05:30\
      </originate-time>
      <receive-time>10-10-2017 07:33:55.258 Z+05:30\
      </receive-time>
      <transmit-time>10-10-2017 07:33:55.300 Z+05:30\
      </transmit-time>
      <input-time>10-10-2017 07:33:55.305 Z+05:30\
      </input-time>
      <ntp-statistics>
        <packet-sent>20</packet-sent>
        <packet-sent-fail>0</packet-sent-fail>
        <packet-received>20</packet-received>
        <packet-dropped>0</packet-dropped>
      </ntp-statistics>
    </unicast-configuration>
  </ntp>
</data>
          

8.2. Refclock master

Below is the example on how to configure reference clock with stratum 8

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <refclock-master>
        <master-stratum>8</master-stratum>
      </refclock-master>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get reference clock configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:refclock-master>
      </sys:refclock-master>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <refclock-master>
      <master-stratum>8</master-stratum>
    </refclock-master>
  </ntp>
</data>
          

8.3. Authentication configuration

Below is the example on how to enable authentication and configure trusted authentication key 10 with mode as md5 and key as abcd

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <authentication>
        <auth-enabled>true</auth-enabled>
        <authentication-keys>
          <key-id>10</key-id>
          <algorithm>md5</algorithm>
          <key>abcd</key>
          <istrusted>true</istrusted>
        </authentication-keys>
      </authentication>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get authentication related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:authentication>
      </sys:authentication>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <authentication>
      <auth-enabled>false</auth-enabled>
      <trusted-keys/>
      <authentication-keys>
        <key-id>10</key-id>
        <algorithm>md5</algorithm>
        <key>abcd</key>
        <istrusted>true</istrusted>
      </authentication-keys>
    </authentication>
  </ntp>
</data>
          

8.4. Access configuration

Below is the example on how to configure access mode "peer" associated with acl 2000.

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <access-rules>
        <access-rule>
          <access-mode>peer</access-mode>
          <acl>2000</acl>
        </access-rule>
      </access-rules>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get access related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:access-rules>
      </sys:access-rules>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <access-rules>
      <access-rule>
        <access-mode>peer</access-mode>
        <acl>2000</acl>
      </access-rule>
    </access-rules>
  </ntp>
</data>
          

8.5. Multicast configuration

Below is the example on how to configure multicast-server with address as "224.1.1.1", port as 1025 and authentication keyid as 10

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <interfaces>
        <interface>
          <name>Ethernet3/0/0</name>
          <multicast-server>
            <address>224.1.1.1</address>
            <authentication>
              <symmetric-key>
                <key-id>10</key-id>
              </symmetric-key>
            </authentication>
            <port>1025</port>
          </multicast-server>
        </interface>
      </interfaces>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get multicast-server related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:interfaces>
        <sys:interface>
          <sys:multicast-server>
          </sys:multicast-server>
        </sys:interface>
      </sys:interfaces>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <interfaces>
      <interface>
        <name>Ethernet3/0/0</name>
        <multicast-server>
          <address>224.1.1.1</address>
          <ttl>224.1.1.1</ttl>
          <authentication>
            <symmetric-key>
              <key-id>10</key-id>
            </symmetric-key>
          </authentication>
          <minpoll>6</minpoll>
          <maxpoll>10</maxpoll>
          <port>1025</port>
          <version>3</version>
        </multicast-server>
      </interface>
    </interfaces>
  </ntp>
</data>
          

Below is the example on how to configure multicast-client with address as "224.1.1.1"

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <interfaces>
        <interface>
          <name>Ethernet3/0/0</name>
          <multicast-client>
            <address>224.1.1.1</address>
          </multicast-client>
        </interface>
      </interfaces>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get multicast-client related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:interfaces>
        <sys:interface>
          <sys:multicast-client>
          </sys:multicast-client>
        </sys:interface>
      </sys:interfaces>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <interfaces>
      <interface>
        <name>Ethernet3/0/0</name>
        <multicast-client>
          <address>224.1.1.1</address>
        </multicast-client>
      </interface>
    </interfaces>
  </ntp>
</data>
          

8.6. Manycast configuration

Below is the example on how to configure manycast-client with address as "224.1.1.1", port as 1025 and authentication keyid as 10

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <interfaces>
        <interface>
          <name>Ethernet3/0/0</name>
          <manycast-client>
            <address>224.1.1.1</address>
            <authentication>
              <symmetric-key>
                <key-id>10</key-id>
              </symmetric-key>
            </authentication>
            <port>1025</port>
          </manycast-client>
        </interface>
      </interfaces>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get manycast-client related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:interfaces>
        <sys:interface>
          <sys:manycast-client>
          </sys:manycast-client>
        </sys:interface>
      </sys:interfaces>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <interfaces>
      <interface>
        <name>Ethernet3/0/0</name>
        <manycast-client>
          <address>224.1.1.1</address>
          <authentication>
            <symmetric-key>
              <key-id>10</key-id>
            </symmetric-key>
          </authentication>
          <ttl>255</ttl>
          <minclock>3</minclock>
          <maxclock>10</maxclock>
          <beacon>6</beacon>
          <minpoll>6</minpoll>
          <maxpoll>10</maxpoll>
          <port>1025</port>
        </manycast-client>
      </interface>
    </interfaces>
  </ntp>
</data>
          

Below is the example on how to configure manycast-server with address as "224.1.1.1"

<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <target>
    <running/>
  </target>
  <config>
    <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <interfaces>
        <interface>
          <name>Ethernet3/0/0</name>
          <manycast-server>
            <address>224.1.1.1</address>
          </manycast-server>
        </interface>
      </interfaces>
    </ntp>
  </config>
</edit-config>
          

Below is the example on how to get manycast-server related configuration

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:interfaces>
        <sys:interface>
          <sys:manycast-server>
          </sys:manycast-server>
        </sys:interface>
      </sys:interfaces>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <interfaces>
      <interface>
        <name>Ethernet3/0/0</name>
        <manycast-server>
          <address>224.1.1.1</address>
        </manycast-server>
      </interface>
    </interfaces>
  </ntp>
</data>
          

8.7. Clock state

Below is the example on how to get clock current state

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:clock-state>
      </sys:clock-state>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <clock-state>
      <system-status>
        <clock-state>synchronized</clock-state>
        <clock-stratum>7</clock-stratum>
        <clock-refid>192.0.2.1</clock-refid>
        <associations-address>192.0.2.1\
        </associations-address>
        <associations-local-mode>client\
        </associations-local-mode>
        <associations-isconfigured>yes\
        </associations-isconfigured>
        <nominal-freq>100.0</nominal-freq>
        <actual-freq>100.0</actual-freq>
        <clock-precision>18</clock-precision>
        <clock-offset>0.025</clock-offset>
        <root-delay>0.5</root-delay>
        <root-dispersion>0.8</root-dispersion>
        <reference-time>10-10-2017 07:33:55.258 Z+05:30\
        </reference-time>
        <sync-state>clock-synchronized</sync-state>
      </system-status>
    </clock-state>
  </ntp>
</data>
          

8.8. Get all association

Below is the example on how to get all association present

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:associations>
      </sys:associations>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <associations>
      <address>192.0.2.1</address>
      <stratum>9</stratum>
      <refid>20.1.1.1</refid>
      <local-mode>client</local-mode>
      <isconfigured>true</isconfigured>
      <authentication-key>10</authentication-key>
      <prefer>true</prefer>
      <peer-interface>Ethernet3/0/0</peer-interface>
      <minpoll>6</minpoll>
      <maxpoll>10</maxpoll>
      <port>1025</port>
      <version>4</version>
      <reach>255</reach>
      <unreach>0</unreach>
      <poll>128</poll>
      <now>10</now>
      <offset>0.025</offset>
      <delay>0.5</delay>
      <dispersion>0.6</dispersion>
      <originate-time>10-10-2017 07:33:55.253 Z+05:30\
      </originate-time>
      <receive-time>10-10-2017 07:33:55.258 Z+05:30\
      </receive-time>
      <transmit-time>10-10-2017 07:33:55.300 Z+05:30\
      </transmit-time>
      <input-time>10-10-2017 07:33:55.305 Z+05:30\
      </input-time>
      <ntp-statistics>
        <packet-sent>20</packet-sent>
        <packet-sent-fail>0</packet-sent-fail>
        <packet-received>20</packet-received>
        <packet-dropped>0</packet-dropped>
      </ntp-statistics>
    </associations>
  </ntp>
</data>
          

8.9. Global statistic

Below is the example on how to get clock current state

<get>
  <filter type="subtree">
    <sys:ntp xmlns:sys="urn:ietf:params:xml:ns:yang:ietf-ntp">
      <sys:ntp-statistics>
      </sys:ntp-statistics>
    </sys:ntp>
  </filter>
</get>

<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <ntp xmlns="urn:ietf:params:xml:ns:yang:ietf-ntp">
    <ntp-statistics>
      <packet-sent>30</packet-sent>
      <packet-sent-fail>5</packet-sent-fail>
      <packet-received>20</packet-received>
      <packet-dropped>2</packet-dropped>
    </ntp-statistics>
  </ntp>
</data>
          

9. IANA Considerations

This document registers a URI in the "IETF XML Registry" [RFC3688]. Following the format in RFC 3688, the following registration has been made.

URI: urn:ietf:params:xml:ns:yang:ietf-ntp

Registrant Contact: The NTP WG of the IETF.

XML: N/A; the requested URI is an XML namespace.

This document registers a YANG module in the "YANG Module Names" registry [RFC6020].

Name: ietf-ntp

Namespace: urn:ietf:params:xml:ns:yang:ietf-ntp

Prefix: ntp

Reference: RFC YYYY

Note: The RFC Editor will replace YYYY with the number assigned to this document once it becomes an RFC.

10. 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 [RFC8446].

The NETCONF access control model [RFC8341] 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:

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:

11. Acknowledgments

The authors would like to express their thanks to Sladjana Zoric, Danny Mayer, Harlan Stenn, Ulrich Windl, Miroslav Lichvar, and Maurice Angermann for their review and suggestions.

12. References

12.1. Normative References

[I-D.ietf-netmod-acl-model] Jethanandani, M., Agarwal, S., Huang, L. and D. Blair, "Network Access Control List (ACL) YANG Data Model", Internet-Draft draft-ietf-netmod-acl-model-21, November 2018.
[RFC1305] Mills, D., "Network Time Protocol (Version 3) Specification, Implementation and Analysis", RFC 1305, DOI 10.17487/RFC1305, March 1992.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC5905] Mills, D., Martin, J., Burbank, J. and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010.
[RFC5907] Gerstung, H., Elliott, C. and B. Haberman, "Definitions of Managed Objects for Network Time Protocol Version 4 (NTPv4)", RFC 5907, DOI 10.17487/RFC5907, June 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8177] Lindem, A., Qu, Y., Yeung, D., Chen, I. and J. Zhang, "YANG Data Model for Key Chains", RFC 8177, DOI 10.17487/RFC8177, June 2017.
[RFC8294] Liu, X., Qu, Y., Lindem, A., Hopps, C. and L. Berger, "Common YANG Data Types for the Routing Area", RFC 8294, DOI 10.17487/RFC8294, December 2017.
[RFC8340] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.

12.2. Informative References

[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for System Management", RFC 7317, DOI 10.17487/RFC7317, August 2014.
[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.

Authors' Addresses

Nan Wu Huawei Huawei Bld., No.156 Beiqing Rd. Beijing, 100095 China EMail: eric.wu@huawei.com
Dhruv Dhody Huawei Divyashree Techno Park, Whitefield Bangalore, Kanataka 560066 India EMail: dhruv.ietf@gmail.com
Ankit kumar Sinha RtBrick Inc. Bangalore, Kanataka India EMail: ankit.ietf@gmail.com
Anil Kumar S N RtBrick Inc. Bangalore, Kanataka India EMail: anil.ietf@gmail.com
Yi Zhao Ericsson China Digital Kingdom Bld., No.1 WangJing North Rd. Beijing, 100102 China EMail: yi.z.zhao@ericsson.com