A YANG Data Model for NTP
draft-ietf-ntp-yang-data-model-02

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 September 6, 2018.

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
• 1.1. Operational State
• 1.2. Terminology
• 1.3. Tree Diagrams
• 2. NTP data model
• 3. Relationship with NTPv4-MIB
• 4. Relationship with RFC 7317
• 5. NTP YANG Module
• 6. Usage Example
• 6.1. Unicast association
• 6.2. Refclock master
• 6.3. Authentication configuration
• 6.4. Access configuration
• 6.5. Multicast configuration
• 6.6. Manycast configuration
• 6.7. Clock state
• 6.8. Get all association
• 6.9. Global statistic
• 7. IANA Considerations
• 8. Security Considerations
• 9. Acknowledgments
• 10. References
• 10.1. Normative References
• 10.2. Informative References
• Authors' Addresses

1. Introduction

This document defines a YANG [RFC6020] 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 [I-D.ietf-netmod-revised-datastores]. 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 [I-D.ietf-netmod-yang-tree-diagrams].

2. NTP data model

module: ietf-ntp
    +--rw ntp!
       +--rw port?                    uint16 {ntp-port}?
       +--rw refclock-master!
       |  +--rw master-stratum?   ntp-stratum
       +--rw authentication
       |  +--rw auth-enabled?          boolean
       |  +--rw trusted-keys* [key-id]
       |  |  +--rw key-id    leafref
       |  +--rw authentication-keys* [key-id]
       |     +--rw key-id       uint32
       |     +--rw algorithm?   identityref
       |     +--rw password?    ianach:crypt-hash
       +--rw access-rules
       |  +--rw access-rule* [access-mode]
       |     +--rw access-mode    access-modes
       |     +--rw acl?           -> /acl:access-lists/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?             uint16 {ntp-port}?
       |  +--rw version?          ntp-version
       +--ro associations* [address local-mode isConfigured]
       |  +--ro address           inet:host
       |  +--ro local-mode        association-modes
       |  +--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?             uint16 {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?             uint16 {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?             uint16 {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?             uint16 {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

       

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 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

YANG NTP Configuration Data Nodes and counterparts in RFC 7317 Objects

5. NTP YANG Module

   <CODE BEGINS> file "ietf-ntp@2018-03-05.yang"
 module ietf-ntp {

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

   prefix "ntp";

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

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

   import ietf-interfaces {
     prefix "if";
   }
   
   import iana-crypt-hash {
     prefix "ianach";
   }
   
   import ietf-key-chain {
     prefix "key-chain";
   }

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

   import ietf-routing-types {
     prefix "rt-types";
   }

   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 YANG module defines essential components for the
      management of a routing subsystem.

      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 2018-03-05 {
     description
       "Updated revision.";
     reference
       "RFC XXXX: A YANG Data Model for NTP Management";
   }

   /* Typedef Definitions */
   
   typedef ntp-stratum {
     type uint8 {
       range "1..16";
     }
     description
       "The level of each server in the hierarchy is defined by
       a stratum number. Primary servers are assigned stratum
       one; secondary servers at each lower level are assigned
       stratum numbers one 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 maximul poll exponent for this NTP association.";
   }

   typedef access-modes {
     type enumeration {
       enum peer {
         value "0";
         description
           "Sets the fully access authority. Both time
           request and control query can be performed
           on the local NTP service, and the local clock
           can be synchronized to 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 to 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
           "Sets the maximum access limitation.
           Control query can be performed only on the
           local NTP service.";
       }
     }
     description
       "This defines NTP acess 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-modes {
     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 learnt this asso dynamically.
           This device may synchronize with its NTP peer.";
       }
       enum broadcast {
         value "3";
         description
           "Use broadcast mode(mode 5). 
           This mode defines that its eigther working
           as broadcast-server or multicast-server.";
       }
       enum broadcast-client {
         value "4";
         description
           "This mode defines that its eigther working
           as broadcast-client or multicast-client.";
       }
     }
     description
       "This defines 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.";
   }

  /* feature */
  feature ntp-port {
    description
      "Indicates that the device supports the configuration of
       the port for NTP.

       This is a 'feature', since many implementations do not 
       support any port other than the default port.";
  }  

   /* 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 password {
       type ianach:crypt-hash;
       description "Clear or encrypted mode for password text.";
     }
   }
   
   grouping authentication-type-param {
     description
         "Authentication type.";
     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
         "Indicates the total number of packets sent.";
     }
     leaf packet-sent-fail {
       type yang:counter32;
       description
         "Indicates the number of times packet
         sending failed.";
     }
     leaf packet-received {
       type yang:counter32;
       description
         "Indicates the total number of packets received.";
     }
     leaf packet-dropped {
       type yang:counter32;
       description
         "Indicates the number of packets dropped.";
     }
   }

   grouping comman-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 maximul poll interval used in this association.";
     }
     leaf port {
       if-feature ntp-port;
       type uint16 {
         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 node";
     leaf associations-address {
         type leafref {
             path "/ntp:ntp/ntp:associations/ntp:address";
         }
         description
           "Indicates the association address 
           which result in clock synchronization.";
     }
     leaf associations-local-mode {
         type leafref {
             path "/ntp:ntp/ntp:associations/ntp:local-mode";
         }
         description
           "Indicates the association local-mode 
           which result in clock synchronization.";
     }
     leaf associations-isConfigured {
         type leafref {
             path "/ntp:ntp/ntp:associations/"
                  + "ntp:isConfigured";
         }
         description
           "Indicates the association was configured or 
           dynamic which result in clock synchronization.";
     }
   }

   /* Configuration data nodes */
   container ntp {
     presence
       "NTP is enable";
     description
       "Configuration parameters for NTP.";
     leaf port {
       if-feature ntp-port;
       type uint16 {
         range "123 | 1025..max";
       }
       default "123";
       description
         "Specify the port used to send NTP packets.";
     }
     container refclock-master {
       presence
          "NTP master clock is enable";
       description
          "Configures the 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 trusted-keys {
           key "key-id";
           description
             "List of keys trusted by NTP.";
           leaf key-id {
             type leafref {
               path "/ntp:ntp/ntp:authentication/"
                   + "ntp:authentication-keys/ntp:key-id";
             }
             description
             "The key trusted by NTP.";
           }
         }
         list authentication-keys {
           key "key-id";
           uses authentication-key;
           description
             "List of authentication key.";
         }
    }

    container access-rules {
      description
        "Configuration of access rules.";
         list access-rule {
           key "access-mode";
           description
             "List of access rules.";
           leaf access-mode {
             type access-modes;
             description
               "NTP access mode.";
            }
           leaf acl {
             type leafref {
              path "/acl:access-lists/acl:acl/acl:name";
             }
             description
               "NTP ACL.";
            }
          }
    }

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

      container system-status {
        description
           "System status of NTP.";
        leaf clock-state {
          type ntp-clock-status;
          mandatory true;
          description "Indicates the state of system clock.";
        }
        leaf clock-stratum {
            type ntp-stratum;
            mandatory true;
            description
              "Indicates the stratum of the reference clock.";
        }
        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 node";
        } 
        leaf nominal-freq {
            type decimal64 {
                fraction-digits 4;
            }
            mandatory true;
            description
              "Indicates the nominal frequency of the
              local clock, in Hz.";
        }
        leaf actual-freq {
            type decimal64 {
                fraction-digits 4;
            }
            mandatory true;
            description
              "Indicates the actual frequency of the
              local clock, in Hz.";
        }
        leaf clock-precision {
            type uint8;
            mandatory true;
            description
              "Precision of the clock of this system
              in Hz.(prec=2^(-n))";
        }
        leaf clock-offset {
            type decimal64 {
                fraction-digits 4;
            }
            description
              "Offset of clock to synchronized peer,
              in milliseconds.";
        }
        leaf root-delay {
            type decimal64 {
                fraction-digits 2;
            }
            description
              "Total delay along path to root clock,
              in milliseconds.";
        }
        leaf root-dispersion {
            type decimal64 {
                fraction-digits 2;
            }
            description
              "Indicates the dispersion between the local clock
              and the master reference clock, in milliseconds.";
        }
        leaf reference-time {
            type yang:date-and-time;
            description
              "Indicates reference timestamp.";
        }
        leaf sync-state {
          type ntp-sync-state;
          mandatory true;
          description
            "Indicates the synchronization status of
            the local clock.";
        }
      }
    }
  list unicast-configuration {
    key "address type";
    description
      "list of unicast-configuration.";
    leaf address {
      type inet:host;
      description
        "The address of this association.";
    }
    leaf type {
      type unicast-configuration-type;
      description
        "Type for this NTP configuration";
    }
    container authentication{
      description
        "Authentication type.";
      uses authentication-type-param;
    }
    leaf prefer {
      type boolean;
      default "false";
      description
        "Whether this association is preferred.";
    }
    leaf burst {
      type boolean;
      default "false";
      description
        "Sends a series of packets instead of a single packet
        within each synchronization interval to achieve faster
        synchronization.";
    }
    leaf iburst {
      type boolean;
      default "false";
      description
        "Sends a series of packets 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 this association used
        as source address.";
    }
    uses comman-attributes {
      description
        "Common attribute like port, version, min and max 
        poll.";
    }
  }

  list associations {
    key "address local-mode isConfigured";
    config "false";
    description
      "list of NTP association.";
    leaf address {
      type inet:host;
      description
        "The address of this association.";
    }
    leaf local-mode {
      type association-modes;
      description
        "Local mode for this NTP association.";
    }
    leaf isConfigured {
      type boolean;
      description
        "Whether this association is configured or 
         dynamically learnt.";
    }
    leaf stratum {
      type ntp-stratum;
      description
        "Indicates the stratum of the reference clock.";
    }
    leaf refid {
      type union {
        type inet:ipv4-address;
        type binary {
          length "4";
        }
        type string {
          length "4";
        }
      }
      description
        "Reference clock type or address for the peer.";
    }
    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
        "Whether this association is preferred.";
    }
    leaf peer-interface {
      type if:interface-ref;
      description
        "The interface which is used for communication.";
    }
    uses comman-attributes {
      description
        "Common attribute like port, version, min and 
         max poll.";
    }
    leaf reach {
      type uint8;
      description
         "Indicates the reachability of the configured
         server or peer.";
    }
    leaf unreach {
      type uint8;
      description
        "Indicates the unreachability of the configured
        server or peer.";
    }
    leaf poll {
      type uint8;
      description
        "Indicates the polling interval for current,
        in seconds.";
    }
    leaf now {
      type uint32;
      description
        "Indicates the time since the NTP packet was
        not received or last synchronized, in seconds.";
    }
    leaf offset {
      type decimal64 {
        fraction-digits 4;
      }
      description
        "Indicates the offset between the local clock
        and the superior reference clock.";
    }
    leaf delay {
      type decimal64 {
        fraction-digits 2;
      }
      description
        "Indicates the delay between the local clock
        and the superior reference clock.";
    }
    leaf dispersion {
      type decimal64 {
        fraction-digits 2;
      }
      description
        "Indicates the dispersion between the local
        clock and the superior reference clock.";
    }
    leaf originate-time {
      type yang:date-and-time;
      description
        "Indicates packet originate timestamp(T1).";
    }
    leaf receive-time {
      type yang:date-and-time;
      description
        "Indicates packet receive timestamp(T2).";
    }
    leaf transmit-time {
      type yang:date-and-time;
      description
        "Indicates packet transmit timestamp(T3).";
    }
    leaf input-time {
      type yang:date-and-time;
      description
        "Indicates packet input timestamp(T4).";
    }
    container ntp-statistics {
      description
        "Per Peer packet send and receive statistic.";
      uses statistics {
          description
            "NTP send and receive packet statistic.";
      }
    }
  }


  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) of a 
            broadcast packet.";
        }
        container authentication{
          description
            "Authentication type.";
            uses authentication-type-param;
        }
        uses comman-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) of a 
            multicast packet.";
        }
        container authentication{
          description
            "Authentication type.";
            uses authentication-type-param;
        }
        uses comman-attributes {
          description
            "Common attribute 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 .";
        }
      }
      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 type.";
            uses authentication-type-param;
        }
        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 comman-attributes {
          description
            "Common attribute like port, version, min and 
             max poll.";
        }
      }
     }
    }
  container ntp-statistics {
    config "false";
    description
      "Total NTP packet statistic.";
    uses statistics {
        description
          "NTP send and receive packet statistic.";
    }
  }
 }
}
<CODE ENDS>

6. Usage Example

6.1. Unicast association

Below is the example on how to configure a preferred unicast server present at 1.1.1.1 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>1.1.1.1</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>

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>1.1.1.1</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>
          

6.2. 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>
          

6.3. Authentication configuration

Below is the example on how to enable authentication and configure authentication key 10 with mode as md5 and password 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>
          <password>abcd</password>
        </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>
        <password>abcd</password>
      </authentication-keys>
    </authentication>
  </ntp>
</data>
          

6.4. Access configuration

Below is the example on how to configure acess type 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>
          

6.5. 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>
          

6.6. 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>
          

6.7. 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>1.1.1.1</clock-refid>
        <associations-address>1.1.1.1
        </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>
          

6.8. 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>1.1.1.1</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>
          

6.9. 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>
          

7. 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 NETMOD 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 XXXX

8. Security Considerations

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

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

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

• /ntp/port - This data node specify the port number to be used to send NTP packets. Unexpected changes could lead to disruption and/or network misbehavior.
• /ntp/authentication and /ntp/access-rules - The entries in the list include the authentication and access control configurations. Car should be taken while setting these parameters.
• /ntp/unicast-configuration - The entries in the list include all unicast configurations (server or peer mode), and indirectly creates or modify the NTP associations. Unexpected changes could lead to disruption and/or network misbehavior.
• /ntp/interfaces/interface - The entries in the list inclide all per-interface configurations related to broadcast, multicast and manycast mode, and indirectly creates or modify the NTP associations. Unexpected changes could lead to disruption and/or network misbehavior.

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:

• /ntp/associations - The entries in the list includes all active NTP associations of all modes. Unauthorized access to this needs to be curtailed.

9. 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.

10. References

10.1. Normative References

10.2. Informative References

Authors' Addresses