YANG Data Model for IEEE 1588-2008
draft-ietf-tictoc-1588v2-yang-11

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Internet Working Group                                   Y. Jiang, Ed.
                                                                Huawei
Internet-Draft                                                  X. Liu
                                                           Independent
Intended status: Standards Track                                 J. Xu
                                                                Huawei
                                                      R. Cummings, Ed.
                                                  National Instruments
Expires: July 2019                                    January 3, 2019

                    YANG Data Model for IEEE 1588-2008
                     draft-ietf-tictoc-1588v2-yang-11

Abstract

   This document defines a YANG data model for the configuration of
   IEEE 1588-2008 devices and clocks, and also retrieval of the
   configuration information, data set and running states of IEEE
   1588-2008 clocks. The YANG module in this document conforms to the
   Network Management Datastore Architecture (NMDA).

Status of this Memo

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

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   This Internet-Draft will expire on July 3, 2019.

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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   warranty as described in the Simplified BSD License.

Table of Contents

   1.   Introduction .............................................. 2
      1.1. Conventions used in this document ...................... 4
      1.2. Terminology ............................................ 4
   2.   IEEE 1588-2008 YANG Model hierarchy ....................... 5
      2.1. Interpretations from IEEE 1588 Working Group ........... 8
      2.2. Configuration and state ................................ 8
   3.   IEEE 1588-2008 YANG Module ................................ 9
   4.   Security Considerations .................................. 22
   5.   IANA Considerations ...................................... 23
   6.   References ............................................... 23
      6.1. Normative References .................................. 23
      6.2. Informative References ................................ 24
   7.   Acknowledgments .......................................... 25
   Appendix A  Transferring YANG Work to IEEE 1588 WG ............ 26
      A.1. Assumptions for the Transfer .......................... 27
      A.2. Intellectual Property Considerations .................. 27
      A.3. Namespace and Module Name ............................. 28
      A.4. IEEE 1588 YANG Modules in ASCII Format ................ 29

1. Introduction

   As a synchronization protocol, IEEE 1588-2008 [IEEE1588] is widely
   supported in the carrier networks, industrial networks, automotive
   networks, and many other applications. It can provide high
   precision time synchronization as fine as nano-seconds. The
   protocol depends on a Precision Time Protocol (PTP) engine to
   decide its own state automatically, and a PTP transportation layer
   to carry the PTP timing and various quality messages. The

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   configuration parameters and state data sets of IEEE 1588-2008 are
   numerous.

   According to the concepts described in [RFC3444], IEEE 1588-2008
   itself provides an information model in its normative
   specifications for the data sets (in IEEE 1588-2008 clause 8). Some
   standardization organizations including the IETF have specified
   data models in MIBs (Management Information Bases) for IEEE 1588-
   2008 data sets (e.g. [RFC8173], [IEEE8021AS]). These MIBs are
   typically focused on retrieval of state data using the Simple
   Network Management Protocol (SNMP), furthermore, configuration of
   PTP data sets is not considered in [RFC8173].

   Some service providers and applications require that the management
   of the IEEE 1588-2008 synchronization network be flexible and more
   Internet-based (typically overlaid on their transport networks).
   Software Defined Network (SDN) is another driving factor, which
   demands an improved configuration capability of synchronization
   networks.

   YANG [RFC7950] is a data modeling language used to model
   configuration and state data manipulated by network management
   protocols like the Network Configuration Protocol (NETCONF)
   [RFC6241]. A small set of built-in data types are defined in
   [RFC7950], and a collection of common data types are further
   defined in [RFC6991]. Advantages of YANG include Internet based
   configuration capability, validation, rollback and so on. All of
   these characteristics make it attractive to become another
   candidate modeling language for IEEE 1588-2008.

   This document defines a YANG data model for the configuration of
   IEEE 1588-2008 devices and clocks, and retrieval of the state data
   of IEEE 1588-2008 clocks. The data model is based on the PTP data
   sets as specified in [IEEE1588]. The technology specific IEEE 1588-
   2008 information, e.g., those specifically implemented by a bridge,
   a router or a telecom profile, is out of scope of this document.

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

   When used in practice, network products in support of
   synchronization typically conform to one or more IEEE 1588-2008
   profiles.  Each profile specifies how IEEE 1588-2008 is used in a
   given industry (e.g. telecom, automotive) and application.  A
   profile can require features that are optional in IEEE 1588-2008,
   and it can specify new features that use IEEE 1588-2008 as a
   foundation.

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   It is expected that the IEEE 1588-2008 YANG module be used as
   follows:

   o  The IEEE 1588-2008 YANG module can be used as-is for products
   that conform to one of the default profiles specified in IEEE 1588-
   2008.

   o  When the IEEE 1588 standard is revised (e.g. the IEEE 1588
   revision in progress at the time of writing this document), it will
   add some new optional features to its data sets.  The YANG module
   of this document can be revised and extended to support these new
   features. Moreover, the YANG "revision" MUST be used to indicate
   changes to the YANG module under such a circumstance.

   o  A profile standard based on IEEE 1588-2008 may create a
   dedicated YANG module for its profile. The profile's YANG module
   SHOULD use YANG "import" to import the IEEE 1588-2008 YANG module
   as its foundation.  Then the profile's YANG module SHOULD use YANG
   "augment" to add any profile-specific enhancements.

   o  A product that conforms to a profile standard may also create
   its own YANG module. The product's YANG module SHOULD "import" the
   profile's module, and then use YANG "augment" to add any product-
   specific enhancements.

1.1. Conventions used in this document

   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.

1.2. Terminology

   Most terminologies used in this document are extracted from
   [IEEE1588].

   BC     Boundary Clock, see Section 3.1.3 of [IEEE1588]

   DS     Data Set

   E2E     End-to-End

   EUI     Extended Unique Identifier

   GPS     Global Positioning System

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   IANA    Internet Assigned Numbers Authority

   IP      Internet Protocol

   NIST    National Institute of Standards and Technology

   NTP     Network Time Protocol

   OC      Ordinary Clock, see Section 3.1.22 of [IEEE1588]

   P2P     Peer-to-Peer

   PTP     Precision Time Protocol

   TAI     International Atomic Time

   TC      Transparent Clock, see Section 3.1.46 of [IEEE1588]

   UTC     Coordinated Universal Time

   PTP data set
            Structured attributes of clocks (an OC, BC or TC) used for
            PTP protocol decisions and for providing values for PTP
            message fields, see Section 8 of [IEEE1588].

   PTP instance
            A PTP implementation in the device (i.e., an OC or BC)
            represented by a specific PTP data set.

2. IEEE 1588-2008 YANG Model hierarchy

   This section describes the hierarchy of an IEEE 1588-2008 YANG
   module. Query and configuration of device wide or port specific
   configuration information and clock data set are described for this
   version.

   Query and configuration of clock information include:

   (Note: The attribute names are consistent with IEEE 1588-2008, but
   changed to the YANG style, i.e., using all lower-case, with dashes
   between words.)

   - Clock data set attributes in a clock node, including: current-ds,
   parent-ds, default-ds, time-properties-ds, and transparent-clock-
   default-ds.

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   - Port-specific data set attributes, including: port-ds and
   transparent-clock-port-ds.

   The readers are assumed to be familiar with IEEE 1588-2008. As all
   PTP terminologies and PTP data set attributes are described in
   details in IEEE 1588-2008 [IEEE1588], this document only outlines
   each of them in the YANG module.

   A simplified YANG tree diagram [RFC8340] representing the data
   model is typically used by YANG modules. This document uses the
   same tree diagram syntax as described in [RFC8340].

   module: ietf-ptp
     +--rw ptp
        +--rw instance-list* [instance-number]
        |  +--rw instance-number      uint32
        |  +--rw default-ds
        |  |  +--rw two-step-flag?    boolean
        |  |  +--ro clock-identity?   clock-identity-type
        |  |  +--rw number-ports?     uint16
        |  |  +--rw clock-quality
        |  |  |  +--rw clock-class?                  uint8
        |  |  |  +--rw clock-accuracy?               uint8
        |  |  |  +--rw offset-scaled-log-variance?   uint16
        |  |  +--rw priority1?        uint8
        |  |  +--rw priority2?        uint8
        |  |  +--rw domain-number?    uint8
        |  |  +--rw slave-only?       boolean
        |  +--rw current-ds
        |  |  +--rw steps-removed?        uint16
        |  |  +--rw offset-from-master?   time-interval-type
        |  |  +--rw mean-path-delay?      time-interval-type
        |  +--rw parent-ds
        |  |  +--rw parent-port-identity
        |  |  |  +--rw clock-identity?   clock-identity-type
        |  |  |  +--rw port-number?      uint16
        |  |  +--rw parent-stats?                 boolean
        |  |  +--rw observed-parent-offset-scaled-log-variance? uint16
        |  |  +--rw observed-parent-clock-phase-change-rate?    int32
        |  |  +--rw grandmaster-identity?         clock-identity-type
        |  |  +--rw grandmaster-clock-quality
        |  |  |  +--rw clock-class?                  uint8
        |  |  |  +--rw clock-accuracy?               uint8
        |  |  |  +--rw offset-scaled-log-variance?   uint16
        |  |  +--rw grandmaster-priority1?           uint8

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        |  |  +--rw grandmaster-priority2?           uint8
        |  +--rw time-properties-ds
        |  |  +--rw current-utc-offset-valid?   boolean
        |  |  +--rw current-utc-offset?         int16
        |  |  +--rw leap59?                     boolean
        |  |  +--rw leap61?                     boolean
        |  |  +--rw time-traceable?             boolean
        |  |  +--rw frequency-traceable?        boolean
        |  |  +--rw ptp-timescale?              boolean
        |  |  +--rw time-source?                uint8
        |  +--rw port-ds-list* [port-number]
        |     +--rw port-number              uint16
        |     +--rw port-state?              port-state-enumeration
        |     +--rw underlying-interface?         if:interface-ref
        |     +--rw log-min-delay-req-interval?   int8
        |     +--rw peer-mean-path-delay?         time-interval-type
        |     +--rw log-announce-interval?        int8
        |     +--rw announce-receipt-timeout?     uint8
        |     +--rw log-sync-interval?            int8
        |     +--rw delay-mechanism?       delay-mechanism-enumeration
        |     +--rw log-min-pdelay-req-interval?   int8
        |     +--rw version-number?                uint8
        +--rw transparent-clock-default-ds
        |  +--ro clock-identity?    clock-identity-type
        |  +--rw number-ports?      uint16
        |  +--rw delay-mechanism?   delay-mechanism-enumeration
        |  +--rw primary-domain?    uint8
        +--rw transparent-clock-port-ds-list* [port-number]
           +--rw port-number                    uint16
           +--rw log-min-pdelay-req-interval?   int8
           +--rw faulty-flag?                   boolean
           +--rw peer-mean-path-delay?          time-interval-type

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2.1. Interpretations from IEEE 1588 Working Group

   The preceding model and the associated YANG module have some subtle
   differences from the data set specifications of IEEE Std 1588-2008.
   These differences are based on interpretation from the IEEE 1588
   Working Group, and are intended to provide compatibility with
   future revisions of the IEEE 1588 standard.

   In IEEE Std 1588-2008, a physical product can implement multiple
   PTP clocks (i.e., ordinary, boundary, or transparent clock). As
   specified in 1588-2008 subclause 7.1, each of the multiple clocks
   operates in an independent domain. However, the organization of
   multiple PTP domains was not clear in the data sets of IEEE Std
   1588-2008. This document introduces the concept of PTP instance as
   described in the new revision of IEEE 1588. The instance concept is
   used exclusively to allow for optional support of multiple domains.
   The instance number has no usage within PTP messages.

   Based on statements in IEEE 1588-2008 subclauses 8.3.1 and 10.1,
   most transparent clock products have interpreted the transparent
   clock data sets to reside as a singleton at the root level of the
   managed product, and this YANG model reflects that location.

2.2. Configuration and state

   The information model of IEEE Std 1588-2008 classifies each member
   in PTP data sets as one of the following:

   - Configurable: Writable by management.

   - Dynamic: Read-only to management, and the value is changed by
   1588 protocol operation.

   - Static: Read-only to management, and the value typically does not
   change.

   For details on the classification of each PTP data set member,
   refer to the IEEE Std 1588-2008 specification for that member.

   Under certain circumstances, the classification of an IEEE 1588
   data set member may change for a YANG implementation, for example,
   a configurable member needs to be changed to read-only. In such a
   case, an implementation SHOULD choose to return a warning upon
   writing to a read-only member, or use the deviation mechanism to
   develop a new deviation model as described in Section 7.20.3 of
   [RFC7950].

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3. IEEE 1588-2008 YANG Module

   This module imports typedef "interface-ref" from [RFC8343]. Most
   attributes are based on the information model defined in [IEEE1588],
   but their names are adapted to the YANG style of naming.

   <CODE BEGINS> file "ietf-ptp@2018-09-10.yang"
   //Note to RFC Editor: update the date to date of publication
   module ietf-ptp {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-ptp";
     prefix "ptp";

     import ietf-interfaces {
       prefix if;
       reference
          "RFC8343: A YANG Data Model for Interface Management";
     }

     organization "IETF TICTOC Working Group";
     contact
         "WG Web:   http://tools.ietf.org/wg/tictoc/
          WG List:  <mailto:tictoc@ietf.org>
          Editor:   Yuanlong Jiang
                    <mailto:jiangyuanlong@huawei.com>
          Editor:   Rodney Cummings
                    <mailto:rodney.cummings@ni.com>";
     description
       "This YANG module defines a data model for the configuration
        of IEEE 1588-2008 clocks, and also for retrieval of the state
        data of IEEE 1588-2008 clocks.";

     revision "2018-09-10" {
       //Note to RFC Editor: update the date to date of publication
       description "Initial version";
       reference "RFC XXXX: YANG Data Model for IEEE 1588-2008";
       //Note to RFC Editor: update RFC XXXX to the actual RFC number

     }

     typedef delay-mechanism-enumeration {
       type enumeration {
         enum e2e {
           value 1;
           description
             "The port uses the delay request-response mechanism.";
         }

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         enum p2p {
           value 2;
           description
             "The port uses the peer delay mechanism.";
         }
         enum disabled {
           value 254;
           description
             "The port does not implement any delay mechanism.";
         }
       }
       description
         "The propagation delay measuring option used by the
          port. Values for this enumeration are specified
          by the IEEE 1588 standard exclusively.";
       reference
         "IEEE Std 1588-2008: 8.2.5.4.4";
     }

     typedef port-state-enumeration {
       type enumeration {
         enum initializing {
           value 1;
           description
             "The port is initializing its data sets, hardware, and
              communication facilities.";
         }
         enum faulty {
           value 2;
           description
             "The port is in the fault state.";
         }
         enum disabled {
           value 3;
           description
             "The port is disabled, and is not communicating PTP
              messages (other than possibly PTP management
              messages).";
         }
         enum listening {
           value 4;
           description
             "The port is listening for an Announce message.";
         }
         enum pre-master {
           value 5;
           description

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             "The port is in the pre-master state.";
         }
         enum master {
           value 6;
           description
             "The port is behaving as a master port.";
         }
         enum passive {
           value 7;
           description
             "The port is in the passive state.";
         }
         enum uncalibrated {
           value 8;
           description
             "A master port has been selected, but the port is still
              in the uncalibrated state.";
         }
         enum slave {
           value 9;
           description
             "The port is synchronizing to the selected master port.";
         }
       }

       description
         "The current state of the protocol engine associated
          with the port.  Values for this enumeration are specified
          by the IEEE 1588 standard exclusively.";
       reference
         "IEEE Std 1588-2008: 8.2.5.3.1, 9.2.5";
     }

     typedef time-interval-type {
       type int64;
       description
         "Derived data type for time interval, represented in units of
           nanoseconds and multiplied by 2^16";
       reference
         "IEEE Std 1588-2008: 5.3.2";
     }

     typedef clock-identity-type {
       type binary {
         length "8";
       }
       description

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         "Derived data type to identify a clock";
       reference
         "IEEE Std 1588-2008: 5.3.4";
     }

     grouping clock-quality-grouping {
       description
         "Derived data type for quality of a clock, which contains
          clockClass, clockAccuracy and offsetScaledLogVariance.";
       reference
         "IEEE Std 1588-2008: 5.3.7";

       leaf clock-class {
         type uint8;
         default 248;
         description
           "The clockClass denotes the traceability of the time
            or frequency distributed by the clock.";
       }

       leaf clock-accuracy {
         type uint8;
         description
           "The clockAccuracy indicates the expected accuracy
            of the clock.";
       }

       leaf offset-scaled-log-variance {
         type uint16;
         description
           "The offsetScaledLogVariance provides an estimate of
            the variations of the clock from a linear timescale
            when it is not synchronized to another clock
            using the protocol.";
       }
     }

     container ptp {
       description
         "The PTP struct containing all attributes of PTP data set,
           other optional PTP attributes can be augmented as well.";

       list instance-list {

         key "instance-number";

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         description
           "List of one or more PTP data sets in the device (see IEEE
            Std 1588-2008 subclause 6.3).
            Each PTP data set represents a distinct instance of
            PTP implementation in the device (i.e., distinct
            Ordinary Clock or Boundary Clock).";

         leaf instance-number {
           type uint32;
           description
              "The instance number of the current PTP instance.
               This instance number is used for management purposes
               only. This instance number does not represent the PTP
               domain number, and is not used in PTP messages.";
         }

         container default-ds {
           description
             "The default data set of the clock (see IEEE Std
              1588-2008 subclause 8.2.1). This data set represents
              the configuration/state required for operation
              of Precision Time Protocol (PTP) state machines.";

           leaf two-step-flag {
             type boolean;
             description
               "When set to true, the clock is a two-step clock;
                otherwise,the clock is a one-step clock.";
           }

           leaf clock-identity {
             type clock-identity-type;
             config false;
             description
               "The clockIdentity of the local clock";
           }

           leaf number-ports {
             type uint16;
             description
               "The number of PTP ports on the instance.";
           }

           container clock-quality {
             description
               "The clockQuality of the local clock.";

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             uses clock-quality-grouping;
           }

           leaf priority1 {
             type uint8;
             description
               "The priority1 attribute of the local clock.";
           }

           leaf priority2{
             type uint8;
             description
               "The priority2 attribute of the local clock.";
           }

           leaf domain-number {
             type uint8;
             description
               "The domain number of the current syntonization
                domain.";
           }

           leaf slave-only {
             type boolean;
             description
               "When set to true, the clock is a slave-only clock.";
           }

         }

         container current-ds {
           description
             "The current data set of the clock (see IEEE Std
              1588-2008 subclause 8.2.2). This data set represents
              local states learned from the exchange of
              Precision Time Protocol (PTP) messages.";

           leaf steps-removed {
             type uint16;
             default 0;
             description
               "The number of communication paths traversed
                between the local clock and the grandmaster clock.";
           }

           leaf offset-from-master {
             type time-interval-type;

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             description
               "The current value of the time difference between
                a master and a slave clock as computed by the slave.";
           }

           leaf mean-path-delay {
             type time-interval-type;
             description
               "The current value of the mean propagation time between
                a master and a slave clock as computed by the slave.";

           }

         }

         container parent-ds {
           description
             "The parent data set of the clock (see IEEE Std 1588-2008
              subclause 8.2.3).";

           container parent-port-identity {
             description
               "The portIdentity of the port on the master, it
                contains two members: clockIdentity and portNumber.";
             reference
               "IEEE Std 1588-2008: 5.3.5";

             leaf clock-identity {
               type clock-identity-type;
               description
                 "Identity of the clock";
             }

             leaf port-number {
               type uint16;
               description
                 "Port number";
             }
           }

           leaf parent-stats {
             type boolean;
             default false;
             description
               "When set to true, the values of
                observedParentOffsetScaledLogVariance and
                observedParentClockPhaseChangeRate of parentDS

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                have been measured and are valid.";
           }

           leaf observed-parent-offset-scaled-log-variance {
             type uint16;
             default 65535;
             description
               "An estimate of the parent clock's PTP variance
                as observed by the slave clock.";
           }

           leaf observed-parent-clock-phase-change-rate {
             type int32;
             description
               "An estimate of the parent clock's phase change rate
                as observed by the slave clock.";
           }

           leaf grandmaster-identity {
             type clock-identity-type;
             description
               "The clockIdentity attribute of the grandmaster clock.";
           }

           container grandmaster-clock-quality {
             description
               "The clockQuality of the grandmaster clock.";
             uses clock-quality-grouping;
           }

           leaf grandmaster-priority1 {
             type uint8;
             description
               "The priority1 attribute of the grandmaster clock.";
           }

           leaf grandmaster-priority2 {
             type uint8;
             description
               "The priority2 attribute of the grandmaster clock.";
           }

         }

         container time-properties-ds {
           description
             "The timeProperties data set of the clock (see

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              IEEE Std 1588-2008 subclause 8.2.4).";

           leaf current-utc-offset-valid {
             type boolean;
             description
               "When set to true, the current UTC offset is valid.";
           }
           leaf current-utc-offset {
             when "../current-utc-offset-valid='true'";
             type int16;
             description
               "The offset between TAI and UTC when the epoch of the
                PTP system is the PTP epoch in units of seconds, i.e.,
                when ptp-timescale is TRUE; otherwise, the value has
                no meaning.";
           }

           leaf leap59 {
             type boolean;
             description
               "When set to true, the last minute of the current UTC
                day contains 59 seconds.";
           }

           leaf leap61 {
             type boolean;
             description
               "When set to true, the last minute of the current UTC
                day contains 61 seconds.";
           }

           leaf time-traceable {
             type boolean;
             description
               "When set to true, the timescale and the
                currentUtcOffset are traceable to a primary
                reference.";
           }

           leaf frequency-traceable {
             type boolean;
             description
               "When set to true, the frequency determining the
                timescale is traceable to a primary reference.";
           }

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           leaf ptp-timescale {
             type boolean;
             description
               "When set to true, the clock timescale of the
                grandmaster clock is PTP; otherwise, the timescale is
                ARB
                (arbitrary).";
           }

           leaf time-source {
             type uint8;
             description
               "The source of time used by the grandmaster clock.";
           }
         }

         list port-ds-list {
           key "port-number";
           description
             "List of port data sets of the clock (see IEEE Std
              1588-2008 subclause 8.2.5).";

           leaf port-number {
             type uint16;

             description
               "Port number.
                The data sets (i.e., information model) of IEEE Std
                1588-2008 specify a member portDS.portIdentity, which
                uses a typed struct with members clockIdentity and
                portNumber.

                In this YANG data model, portIdentity is not modeled
                in the port-ds-list, however, its members are provided
                as follows:
                portIdentity.portNumber is provided as this port-
                number leaf in port-ds-list; and
                portIdentity.clockIdentity is provided as the clock-
                identity leaf in default-ds of the instance
                (i.e., ../../default-ds/clock-identity).";
           }

           leaf port-state {
             type port-state-enumeration;
             default "initializing";
             description
               "Current state associated with the port.";

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           }

           leaf underlying-interface {
            type if:interface-ref;
            description
               "Reference to the configured underlying interface that
                is used by this PTP Port (see RFC 8343).";
           }

           leaf log-min-delay-req-interval {
             type int8;
             description
               "The base-two logarithm of the minDelayReqInterval
                (the minimum permitted mean time interval between
                successive Delay_Req messages).";
           }

           leaf peer-mean-path-delay {
             type time-interval-type;
             default 0;
             description
               "An estimate of the current one-way propagation delay
                on the link when the delayMechanism is P2P; otherwise,
                it is zero.";
           }

           leaf log-announce-interval {
             type int8;
             description
               "The base-two logarithm of the mean
                announceInterval (mean time interval between
                successive Announce messages).";
           }

           leaf announce-receipt-timeout {
             type uint8;
             description
               "The number of announceInterval that have to pass
                without receipt of an Announce message before the
                occurrence of the event ANNOUNCE_RECEIPT_TIMEOUT_
                EXPIRES.";
           }

           leaf log-sync-interval {
             type int8;
             description
               "The base-two logarithm of the mean SyncInterval

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                for multicast messages.  The rates for unicast
                transmissions are negotiated separately on a per port
                basis and are not constrained by this attribute.";
           }

           leaf delay-mechanism {
             type delay-mechanism-enumeration;
             description
               "The propagation delay measuring option used by the
                port in computing meanPathDelay.";
           }

           leaf log-min-pdelay-req-interval {
             type int8;
             description
               "The base-two logarithm of the
                minPdelayReqInterval (minimum permitted mean time
                interval between successive Pdelay_Req messages).";

           }

           leaf version-number {
             type uint8;
             description
               "The PTP version in use on the port.";
           }

         }
      }

      container transparent-clock-default-ds {
        description
          "The members of the transparentClockDefault data set (see
           IEEE Std 1588-2008 subclause 8.3.2).";

        leaf clock-identity {
          type clock-identity-type;
          config false;
          description
            "The clockIdentity of the transparent clock.";
        }

        leaf number-ports {
          type uint16;
          description
            "The number of PTP ports on the transparent clock.";
        }

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        leaf delay-mechanism {
          type delay-mechanism-enumeration;
          description
            "The propagation delay measuring option
             used by the transparent clock.";
        }

        leaf primary-domain {
          type uint8;
          default 0;
          description
            "The domainNumber of the primary syntonization domain (see
             IEEE Std 1588-2008 subclause 10.1).";
        }
      }

      list transparent-clock-port-ds-list {
        key "port-number";
        description
          "List of transparentClockPort data sets of the transparent
           clock (see IEEE Std 1588-2008 subclause 8.3.3).";

        leaf port-number {
            type uint16;
            description
              "Port number.
               The data sets (i.e., information model) of IEEE Std
               1588-2008 specify a member
               transparentClockPortDS.portIdentity, which uses a typed
               struct with members clockIdentity and portNumber.

               In this YANG data model, portIdentity is not modeled in
               the transparent-clock-port-ds-list, however, its
               members are provided as follows:
               portIdentity.portNumber is provided as this leaf member
               in transparent-clock-port-ds-list; and
               portIdentity.clockIdentity is provided as the clock-
               identity leaf in transparent-clock-default-ds
               (i.e., ../../transparent-clock-default-ds/clock-
               identity).";

        }

        leaf log-min-pdelay-req-interval {
          type int8;

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          description
            "The logarithm to the base 2 of the
             minPdelayReqInterval (minimum permitted mean time
             interval between successive Pdelay_Req messages).";
        }

        leaf faulty-flag {
          type boolean;
          default false;
          description
            "When set to true, the port is faulty.";
        }

        leaf peer-mean-path-delay {
          type time-interval-type;
          default 0;
          description
            "An estimate of the current one-way propagation delay
             on the link when the delayMechanism is P2P; otherwise,
             it is zero.";
        }

       }
     }
   }

   <CODE ENDS>

4. 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]. Furthermore,
   general security considerations of time protocols are discussed in
   [RFC7384].

   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 are
   writable, and the involved subtrees that are sensitive include:

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   /ptp/instance-list specifies an instance (i.e., PTP data sets) for
   an OC or BC.

   /ptp/transparent-clock-default-ds specifies a default data set for
   a TC.

   /ptp/transparent-clock-port-ds-list specifies a list of port data
   sets for a TC.

   Write operations (e.g., edit-config) to these data nodes without
   proper protection can have a negative effect on network operations.
   Specifically, an inappropriate configuration of them may adversely
   impact a PTP synchronization network. For example, loss of
   synchronization on a clock, accuracy degradation on a set of clocks,
   or even break down of a whole synchronization network.

5. IANA Considerations

   This document registers the following URI in the "IETF XML
   registry" [RFC3688]:
   URI: urn:ietf:params:xml:ns:yang:ietf-ptp
   Registrant Contact: The IESG
   XML: N/A; the requested URI is an XML namespace

   This document registers the following YANG module in the "YANG
   Module Names" registry [RFC6020]:
   Name:         ietf-ptp
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-ptp
   Prefix:       ptp
   Reference:    RFC XXXX

6. References

6.1.  Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997

   [RFC3688] Mealling, M., "The IETF XML Registry", RFC 3688,
             January 2004

   [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
             Network Configuration Protocol (NETCONF) ", RFC 6020,
             October 2010

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   [RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and Bierman,
             A., "Network Configuration Protocol (NETCONF)", RFC 6241,
             June 2011

   [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
             Shell (SSH)", RFC 6242, June 2011

   [RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
             July 2013

   [RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC
             7950, August 2016

   [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
             Protocol", RFC 8040, January 2017

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, May 2017

   [RFC8341] Bierman, A. and Bjorklund, M., "Network Configuration
             Protocol (NETCONF) Access Control Model", RFC 8341, March
             2018

   [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
             and R. Wilton, "Network Management Datastore Architecture
             (NMDA)", RFC 8342, March 2018

   [RFC8343] Bjorklund, M., "A YANG Data Model for Interface
             Management", RFC 8343, March 2018

   [RFC8446] Rescorla, E., "The Transport Layer Security (TLS)
             Protocol Version 1.3", RFC 8446, August 2018

   [IEEE1588] IEEE, "IEEE Standard for a Precision Clock
             Synchronization Protocol for Networked Measurement and
             Control Systems", IEEE Std 1588-2008, July 2008

6.2. Informative References

   [IEEE8021AS] IEEE, "Timing and Synchronizations for Time-Sensitive
             Applications in Bridged Local Area Networks", IEEE
             802.1AS-2001, 2011

   [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
             Information Models and Data Models", RFC 3444, January
             2003

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   [RFC4663] Harrington, D., "Transferring MIB Work from IETF Bridge
             MIB WG to IEEE 802.1 WG", RFC 4663, September 2006

   [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
             Packet Switched Networks", RFC 7384, October 2014

   [RFC8340] Bjorklund, M., and Berger, L., "YANG Tree Diagrams", RFC
             8340, March 2018

   [RFC8173] Shankarkumar, V., Montini, L., Frost, T., and Dowd, G.,
             "Precision Time Protocol Version 2 (PTPv2) Management
             Information Base", RFC 8173, June 2017

7. Acknowledgments

   The authors would like to thank Tom Petch, Radek Krejci, Mahesh
   Jethanandani, Tal Mizrahi, Opher Ronen, Liang Geng, Alex Campbell,
   Joe Gwinn, John Fletcher, William Zhao and Dave Thaler for their
   valuable reviews and suggestions, thank Benoit Claise and Radek
   Krejci for their validation of the YANG module, and thank Jingfei
   Lv and Zitao Wang for their discussions on IEEE 1588 and YANG
   respectively.

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Appendix A  Transferring YANG Work to IEEE 1588 WG

   This Appendix is informational.

   This appendix describes a future plan to transition responsibility
   for IEEE 1588 YANG modules from the IETF TICTOC Working Group (WG)
   to the IEEE 1588 WG, which develops the time synchronization
   technology that the YANG modules are designed to manage.

   This appendix is forward-looking with regard to future
   standardization roadmaps in IETF and IEEE.  Since those roadmaps
   cannot be predicted with significant accuracy, this appendix is
   informational, and it does not specify imperatives or normative
   specifications of any kind.

   The IEEE 1588-2008 YANG module of this standard represents a
   cooperation between IETF (for YANG) and IEEE (for 1588).  For the
   initial standardization of IEEE-1588 YANG modules, the information
   model is relatively clear (i.e., IEEE 1588 data sets), but
   expertise in YANG is required, making IETF an appropriate location
   for the standards.  The TICTOC WG has expertise with IEEE 1588,
   making it the appropriate location within IETF.

   The IEEE 1588 WG anticipates future changes to its standard on an
   ongoing basis.  As IEEE 1588 WG members gain practical expertise
   with YANG, the IEEE 1588 WG will become more appropriate for
   standardization of its YANG modules.  As the IEEE 1588 standard is
   revised and/or amended, IEEE 1588 members can more effectively
   synchronize the revision of this YANG module with future versions
   of the IEEE 1588 standard.

   This appendix is meant to establish some clear expectations between
   IETF and IEEE about the future transfer of IEEE 1588 YANG modules
   to the IEEE 1588 WG.  The goal is to assist in making the future
   transfer as smooth as possible. As the transfer takes place, some
   case-by-case situations are likely to arise, which can be handled
   by discussion on the IETF TICTOC WG mailing lists and/or
   appropriate liaisons.

   This appendix obtained insight from [RFC4663], an informational
   memo that described a similar transfer of MIB work from the IETF
   Bridge MIB WG to the IEEE 802.1 WG.

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A.1. Assumptions for the Transfer

   For the purposes of discussion in this appendix, assume that the
   IESG has approved the publication of an RFC containing a YANG
   module for a published IEEE 1588 standard.  As of this writing,
   this is IEEE Std 1588-2008, but it is possible that YANG modules
   for subsequent 1588 revisions could be published from the IETF
   TICTOC WG.  For discussion in this appendix, we use the phrase
   "last IETF 1588 YANG" to refer to the most recently published 1588
   YANG module from the IETF TICTOC WG.

   The IEEE-SA Standards Board New Standards Committee (NesCom)
   handles new Project Authorization Requests (PARs) (see
   http://standards.ieee.org/board/nes/). PARs are roughly the
   equivalent of IETF Working Group Charters and include information
   concerning the scope, purpose, and justification for
   standardization projects.

   Assume that IEEE 1588 has an approved PAR that explicitly specifies
   development of a YANG module. The transfer of YANG work will occur
   in the context of this IEEE 1588 PAR. For discussion in this
   appendix, we use the phrase "first IEEE 1588 YANG" to refer to the
   first IEEE 1588 standard for YANG.

   Assume that as part of the transfer of YANG work, the IETF TICTOC
   WG agrees to cease all work on standard YANG modules for IEEE 1588.

   Assume that the IEEE 1588 WG has participated in the development of
   the last IETF 1588 YANG module, such that the first IEEE 1588 YANG
   module will effectively be a revision of it. In other words, the
   transfer of YANG work will be relatively clean.

   The actual conditions for the future transfer can be such that the
   preceding assumptions do not hold. Exceptions to the assumptions
   will need to be addressed on a case-by-case basis at the time of
   the transfer. This appendix describes topics that can be addressed
   based on the preceding assumptions.

A.2. Intellectual Property Considerations

   During review of the legal issues associated with transferring
   Bridge MIB WG documents to the IEEE 802.1 WG (Section 3.1 and
   Section 9 of [RFC4663]), it was concluded that the IETF does not
   have sufficient legal authority to make the transfer to IEEE
   without the consent of the document authors.

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   If the last IETF 1588 YANG is published as a RFC, the work is
   required to be transferred from the IETF to the IEEE, so that IEEE
   1588 WG can begin working on the first IEEE 1588 YANG.

   When work on the first IEEE YANG module begins in the IEEE 1588 WG,
   that work derives from the last IETF YANG module of this RFC,
   requiring a transfer of that work from the IETF to the IEEE. In
   order to avoid having the transfer of that work be dependent on the
   availability of this RFC's authors at the time of its publication,
   the IEEE Standards Association department of Risk Management and
   Licensing provided the appropriate forms and mechanisms for this
   document's authors to assign a non-exclusive license for IEEE to
   create derivative works from this document. Those IEEE forms and
   mechanisms will be updated as needed for any future IETF YANG
   modules for IEEE 1588 (The signed forms are held by the IEEE
   Standards Association department of Risk Management and Licensing.).
   This will help to make the future transfer of work from IETF to
   IEEE occur as smoothly as possible.

   As stated in the initial "Status of this Memo", the YANG module in
   this document conforms to the provisions of BCP 78. The IETF will
   retain all the rights granted at the time of publication in the
   published RFCs.

A.3. Namespace and Module Name

   As specified in Section 5 "IANA Considerations", the YANG module in
   this document uses IETF as the root of its URN namespace and YANG
   module name.

   Use of IETF as the root of these names implies that the YANG module
   is standardized in a Working Group of IETF, using the IETF
   processes. If the IEEE 1588 Working Group were to continue using
   these names rooted in IETF, the IEEE 1588 YANG standardization
   would need to continue in the IETF. The goal of transferring the
   YANG work is to avoid this sort of dependency between standards
   organizations.

   IEEE 802 has an active PAR (IEEE P802d) for creating a URN
   namespace for IEEE use (see
   http://standards.ieee.org/develop/project/802d.html). It is likely
   that this IEEE 802 PAR will be approved and published prior to the
   transfer of YANG work to the IEEE 1588 WG. If so, the IEEE 1588 WG
   can use the IEEE URN namespace for the first IEEE 1588 YANG module,
   such as:

      urn:ieee:Std:1588:yang:ieee1588-ptp

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   where "ieee1588-ptp" is the registered YANG module name in the IEEE.

   Under the assumptions of section A.1, the first IEEE 1588 YANG
   module's prefix will be the same as the last IETF 1588 YANG
   module's prefix (i.e. "ptp"). Consequently, other YANG modules can
   preserve the same import prefix "ptp" to access PTP nodes during
   the migration from the last IETF 1588 YANG module to the first IEEE
   1588 YANG module.

   The result of these name changes are that for complete
   compatibility, a server (i.e., IEEE 1588 node) can choose to
   implement a YANG module for the last IETF 1588 YANG module (with
   IETF root) as well as the first IEEE 1588 YANG module (with IEEE
   root).  Since the content of the YANG module transferred are the
   same, the server implementation is effectively common for both.

   From a client's perspective, a client of the last IETF 1588 YANG
   module (or earlier) looks for the IETF-rooted module name; and a
   client of the first IEEE 1588 YANG module (or later) looks for the
   IEEE-rooted module name.

A.4. IEEE 1588 YANG Modules in ASCII Format

   Although IEEE 1588 can certainly decide to publish YANG modules
   only in the PDF format that they use for their standard documents,
   without publishing an ASCII version, most network management
   systems cannot import the YANG module directly from the PDF. Thus,
   not publishing an ASCII version of the YANG module would negatively
   impact implementers and deployers of YANG modules and would make
   potential IETF reviews of YANG modules more difficult.

   This appendix recommends that the IEEE 1588 WG consider future
   plans for:

   o Public availability of the ASCII YANG modules during project
      development. These ASCII files allow IETF participants to access
      these documents for pre-standard review purposes.

   o Public availability of the YANG portion of published IEEE 1588
      standards, provided as an ASCII file for each YANG module.
      These ASCII files are intended for use of the published IEEE
      1588 standard.

   As an example of public availability during project development,
   IEEE 802 uses the same repository that IETF uses for YANG module
   development (see https://github.com/YangModels/yang). IEEE branches
   are provided for experimental work (i.e. pre-PAR) as well as

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   standard work (post-PAR drafts). IEEE-SA has approved use of this
   repository for project development, but not for published standards.

   As an example of public availability of YANG modules for published
   standards, IEEE 802.1 provides a public list of ASCII files for MIB
   (see http://www.ieee802.org/1/files/public/MIBs/ and
   http://www.ieee802.org/1/pages/MIBS.html), and analogous lists are
   planned for IEEE 802.1 YANG files.

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   Authors' Addresses

   Yuanlong Jiang (Editor)
   Huawei Technologies Co., Ltd.
   Bantian, Longgang district
   Shenzhen 518129, China
   Email: jiangyuanlong@huawei.com

   Xian Liu
   Independent
   Shenzhen 518129, China
   lene.liuxian@foxmail.com

   Jinchun Xu
   Huawei Technologies Co., Ltd.
   Bantian, Longgang district
   Shenzhen 518129, China
   xujinchun@huawei.com

   Rodney Cummings (Editor)
   National Instruments
   11500 N. Mopac Expwy
   Bldg. C
   Austin, TX 78759-3504
   Email: Rodney.Cummings@ni.com

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