One document matched: draft-tissa-lime-yang-oam-model-05.xml


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<rfc category="std" docName=" draft-tissa-lime-yang-oam-model-05"
     ipr="trust200902">
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  <front>
    <title abbrev="Generic OAM YANG Model">Generic YANG Data Model for
    Operations, Administration, and Maintenance (OAM)</title>

    <author fullname="Tissa Senevirathne" initials="T." surname="Senevirathne">
      <organization abbrev="Cisco">CISCO Systems</organization>

      <address>
        <postal>
          <street>375 East Tasman Drive.</street>

          <street/>

          <city>San Jose</city>

          <region>CA</region>

          <code>95134</code>

          <country>USA</country>
        </postal>

        <phone>408-853-2291</phone>

        <email>tsenevir@cisco.com</email>
      </address>
    </author>

    <author fullname="Norman Finn" initials="N." surname="Finn">
      <organization abbrev="Cisco">CISCO Systems</organization>

      <address>
        <postal>
          <street>510 McCarthy Blvd</street>

          <street/>

          <city>Milpitas</city>

          <region>CA</region>

          <code>95035</code>

          <country>USA</country>
        </postal>

        <email>nfinn@cisco.com</email>
      </address>
    </author>

    <author fullname="Deepak Kumar" initials="D." role="editor"
            surname="Kumar">
      <organization abbrev="Cisco">CISCO Systems</organization>

      <address>
        <postal>
          <street>510 McCarthy Blvd</street>

          <street/>

          <city>Milpitas</city>

          <region>CA</region>

          <code>95035</code>

          <country>USA</country>
        </postal>

        <email>dekumar@cisco.com</email>
      </address>
    </author>

    <author fullname="Samer Salam" initials="S." surname="Salam">
      <organization abbrev="Cisco">CISCO Systems</organization>

      <address>
        <postal>
          <street>595 Burrard St. Suite 2123</street>

          <street/>

          <city>Vancouver</city>

          <region>BC</region>

          <code>V7X 1J1</code>

          <country>Canada</country>
        </postal>

        <email>ssalam@cisco.com</email>
      </address>
    </author>

    <author fullname="Qin Wu" initials="Q." role="editor" surname="Wu">
      <organization>Huawei</organization>

      <address>
        <postal>
          <street>101 Software Avenue, Yuhua District</street>

          <city>Nanjing</city>

          <region>Jiangsu</region>

          <code>210012</code>

          <country>China</country>
        </postal>

        <email>bill.wu@huawei.com</email>
      </address>
    </author>

    <author fullname="Michael Wang" initials="M." surname="Wang">
      <organization abbrev="Huawei">Huawei Technologies,Co.,Ltd</organization>

      <address>
        <postal>
          <street>101 Software Avenue, Yuhua District</street>

          <street/>

          <city>Nanjing</city>

          <region/>

          <code>210012</code>

          <country>China</country>
        </postal>

        <email>wangzitao@huawei.com</email>
      </address>
    </author>

    <date year="2015"/>

    <area>OPS Area</area>

    <workgroup/>

    <abstract>
      <t>This document presents base YANG Data model for OAM. It provides a
      protocol-independent and technology-independent abstraction of key OAM
      constructs. Based model presented here can be extended to include
      technology specific details. Leading to uniformity between OAM
      technologies and support nested OAM workflows (i.e., performing OAM
      functions at different layers through a unified interface). </t>
    </abstract>
  </front>

  <middle>
    <section title="Introduction">
      <t>Operations, Administration, and Maintenance (OAM) are important
      networking functions that allow operators to: <list style="numbers">
          <t>Monitor networks (Connectivity Verification, Continuity
          Check).</t>

          <t>Troubleshoot failures (Fault verification and isolation).</t>

          <t>Measure Performance</t>
        </list></t>

      <t>An overview of OAM tools is presented at [RFC7276].</t>

      <t>Ping and Traceroute [RFC792], [RFC4443] are well-known fault
      verification and isolation tools, respectively, for IP networks. Over
      the years, different technologies have developed similar tools for
      similar purposes.</t>

      <t>[IEEE802.1Q] Connectivity Fault Management is a well-established OAM
      standard that is widely adopted for Ethernet networks. ITU-T
      [Y.1731]<xref target="Y.1731"/>, MEF Service OAM, MPLS-TP [RFC6371],
      TRILL [RFC7455]<xref target="RFC7455"/> all define OAM methods based on
      manageability frame work of [IEEE802.1Q] <xref
      target="IEEE802.1Q"/>CFM.</t>

      <t>Given the wide adoption of the underlying OAM concepts defined in
      [IEEE802.1Q]<xref target="IEEE802.1Q"/> CFM, it is a reasonable choice
      to develop the unified management framework based on those concepts. In
      this document, we take the [IEEE802.1Q]<xref target="IEEE802.1Q"/> CFM
      model and extend it to a technology independent framework and build the
      corresponding YANG model accordingly. The YANG model presented in this
      document is the base model and supports generic continuity check,
      connectivity verification and path discovery. The generic OAM YANG model
      is designed such that it can be extended to cover various technologies.
      Technology dependent nodes and RPC commands are defined in technology
      specific YANG models, which use and extend the base model defined here.
      As an example, VXLAN uses source UDP port number for flow entropy, while
      MPLS [RFC4379] uses IP addresses or the label stack for flow entropy in
      the hashing for multipath selection. To capture this variation,
      corresponding YANG models would define the applicable structures as
      augmentation to the generic base model presented here. This accomplishes
      three purposes: first it keeps each YANG model smaller and manageable.
      Second, it allows independent development of corresponding YANG models.
      Third, implementations can limit support to only the applicable set of
      YANG models. (e.g. TRILL RBridge may only need to implement Generic OAM
      model and the TRILL YANG model).</t>

      <t>All implementations that follow the YANG framework presented in this
      document MUST implement the generic OAM YANG model presented here.</t>

      <t>The YANG data model presented in this document occurs at the
      management layer. Encapsulations and state machines may differ according
      to each OAM protocol. A user who wishes to issues a Ping command or a
      Traceroute or initiate a performance monitoring session can do so in the
      same manner regardless of the underlying protocol or technology or
      specific vendor implementation.</t>

      <t>As an example, consider a scenario where an IP ping from device A to
      Device B failed. Between device A and B there are IEEE 802.1 bridges a,b
      and c. Let's assume a,b and c are using [IEEE802.1Q] CFM. A user upon
      detecting the IP layer ping failures may decide to drill down to the
      Ethernet layer and issue the corresponding fault verification (LBM) and
      fault isolation (LTM) tools, using the same API. This ability to go up
      and down to different layers for troubleshooting is referred to as
      "nested OAM workflow" and is a useful concept that leads to efficient
      network troubleshooting and maintenance. The OAM YANG model presented in
      this document facilitates that without needing changes to the underlying
      protocols.</t>
    </section>

    <section title="Conventions used in this document">
      <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
      "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
      document are to be interpreted as described in <xref
      target="RFC2119"/>.</t>

      <t>In this document, these words will appear with that interpretation
      only when in ALL CAPS. Lower case uses of these words are not to be
      interpreted as carrying RFC-2119 significance.</t>

      <section title="Terminology">
        <t><list style="hanging">
            <t hangText="CCM">Continuity Check Message [IEEE802.1Q].<vspace
            blankLines="1"/></t>

            <t hangText="ECMP"><vspace blankLines="0"/>Equal Cost
            Multipath.<vspace blankLines="1"/></t>

            <t hangText="LBM"><vspace blankLines="0"/>Loopback Message
            [IEEE802.1Q].<vspace blankLines="1"/></t>

            <t hangText="MP"><vspace blankLines="0"/>Maintenance Point
            [IEEE802.1Q].<vspace blankLines="1"/></t>

            <t hangText="MEP"><vspace blankLines="0"/>Maintenance End Point
            [RFC7174] [IEEE802.1Q] [RFC6371].<vspace blankLines="1"/></t>

            <t hangText="MIP"><vspace blankLines="0"/>Maintenance Intermediate
            Point [RFC7174] [IEEE802.1Q] [RFC6371].<vspace
            blankLines="1"/></t>

            <t hangText="MA"><vspace blankLines="0"/>Maintenance Association
            [IEEE802.1Q] [RFC7174].<vspace blankLines="1"/></t>

            <t hangText="MD"><vspace blankLines="0"/>Maintenance Domain
            [IEEE802.1Q]<vspace blankLines="1"/></t>

            <t hangText="MTV"><vspace blankLines="0"/> Multi-destination Tree
            Verification Message.<vspace blankLines="1"/></t>

            <t hangText="OAM"><vspace blankLines="0"/>Operations,
            Administration, and Maintenance [RFC6291].<vspace
            blankLines="1"/></t>

            <t hangText="TRILL"><vspace blankLines="0"/>Transparent
            Interconnection of Lots of Links [RFC6325].<vspace
            blankLines="1"/></t>
          </list></t>
      </section>
    </section>

    <section title="Architecture of Generic YANG Model for OAM">
      <t>In this document we define a generic YANG model for OAM. The YANG
      model defined here is generic such that other technologies can extend it
      for technology specific needs. The Generic OAM YANG model acts as the
      root for other OAM YANG models. This allows users to traverse between
      OAM of different technologies at ease through a uniform API set. This is
      also provides a nested OAM workflow. Figure 1 depicts the relationship
      of different OAM YANG models to the Generic OAM YANG Model. Some
      technologies may have different sub-technologies. As an example,
      consider Network Virtualization Overlays. These could employ either
      vXLAN or NVGRE as encapsulation. The Generic OAM YANG model provides a
      framework where technology-specific YANG models can inherit constructs
      from the base YANG models without needing to redefine them within the
      sub-technology.</t>

      <t>Figure 1 depicts relationship of different YANG modules.</t>

      <figure title="Relationship of OAM YANG model to generic (base) YANG model">
        <artwork>                          +-+-+-+-+-+
                          |  gen    |
                          |OAM YANG |
                          +-+-+-+-+-+
                               |
                               O
                               |
       +---------------------------------------------------------+
       |              |               |         |                |
   +-+-+-+-+-+   +-+-+-+-+-+   +-+-+-+-+-+ +-+-+-+-+-+      +-+-+-+-+-+
   | TRILL   |   | NVO3    |   | MPLS    | | IP      | . . .|  foo    |
   |OAM YANG |   |OAM YANG |   |OAM YANG | |OAM YANG |      |OAM YANG |
   +-+-+-+-+-+   +-+-+-+-+-+   +-+-+-+-+-+ +-+-+-+-+-+      +-+-+-+-+-+
         |             |             |           |              |
         |       +-+-+-+-+-+   +-+-+-+-+-+       |          +-+-+-+-+-+
         |       | NVO3    |   | MPLS    |       |     . . .|  foo    |
         |       |sub tech |   |sub tech |       |          |sub tech |
         |       +-+-+-+-+-+   +-+-+-+-+-+       |          +-+-+-+-+-+
         |             |             |           |              |
         |             |             |           |              |
       +------------------------------------------------------------+
       |             Uniform API                                    |
       +------------------------------------------------------------+
</artwork>
      </figure>
    </section>

    <section title="Overview of the OAM Model">
      <t>In this document we adopt the concepts of the [IEEE802.1Q] CFM model
      and structure it such that it can be adapted to different
      technologies.</t>

      <t>At the top of the Model is the Maintenance Domain. Each Maintenance
      Domain is associated with a Maintenance Name and a Domain Level.</t>

      <t>Under each Maintenance Domain there is one or more Maintenance
      Association (MA). In IP, the MA can be per IP Subnet, in NVO3 this can
      be per VNI and for TRILL this can be per Fine-Grained Label or for VPLS
      this can be per VPLS instance.</t>

      <t>Under each MA, there can be two or more MEPs (Maintenance End
      Points). MEPs are addressed by their respective technology specific
      address identifiers. The YANG model presented here provides flexibility
      to accommodate different addressing schemes.</t>

      <t>In a parallel vertical, presented are the commands. Those, in YANG
      terms, are the rpc commands. These rpc commands provide uniform APIs for
      continuity check,connectivity verification, path discovery and their
      equivalents as well as other OAM commands.</t>

      <t>[IEEE802.1Q] CFM framework requires explicit configuration of OAM
      entities prior to using any of the OAM tools. Users of Ping and
      Traceroute tools within IP devices are expecting ability to use OAM
      tools with no explicit configuration. In order to facilitate zero-touch
      experience, this document defines a default mode of OAM. The default
      mode of OAM is referred to as the Base Mode and specifies default values
      for each of the [IEEE802.1Q] CFM parameters, such as Maintenance Domain
      Level, Name of the Maintenance Association and Addresses of MEP and so
      on. The default values of these depend on the technology. Base Mode for
      TRILL is defined in [RFC7455]. Base mode for other technologies such as
      NVO3, MPLS and future extensions will be defined in their corresponding
      documents.</t>

      <t>It is important to note that, no specific enhancements are needed in
      the YANG model to support Base Mode. Implementations that comply with
      this document, by default implement the data nodes of the applicable
      technology. Data nodes of the Base Mode are read-only nodes.</t>

      <section title="Maintenance Domain (MD) configuration">
        <t>The container "domains" is the top level container within the
        gen-oam module. Within the container "domains", separate list is
        maintained per MD. The MD list uses the key MD-name-string for
        indexing. MD- name-string is a leaf and derived from type string.
        Additional name formats as defined in [IEEE802.1Q] or other standards
        can be included by association of the MD-name-format with an
        identity-ref. MD-name- format indicates the format of the augmented
        MD-names. MD-name is presented as choice/case construct. Thus, it is
        easily augmentable by derivative work.</t>

        <figure title="Snippet of data hierarchy related to OAM domains">
          <artwork>    module: ietf-gen-oam
      +--rw domains
         +--rw domain* [technology MD-name-string]
            +--rw technology        identityref
            +--rw MD-name-string    MD-name-string
            +--rw MD-name-format?   identityref
            +--rw (MD-name)?
            |  +--:(MD-name-null)
            |     +--rw MD-name-null?     empty
            +--rw md-level          MD-level  .
</artwork>
        </figure>
      </section>

      <section title="Maintenance Association (MA) configuration">
        <t>Within a given Maintenance Domain there can be one or more
        Maintenance Associations (MA). MAs are represented as a list and
        indexed by the MA-name-string. Similar to MD-name defined previously,
        additional name formats can be added by augmenting the name-format
        identity-ref and adding applicable case statements to MA-name.</t>

        <figure title="Snippet of data hierarchy related to Maintenance Associations (MA) ">
          <artwork>   module: ietf-gen-oam
      +--rw domains
         +--rw domain* [technology MD-name-string]
            .
            .
            +--rw MAs
               +--rw MA* [MA-name-string]
                  +--rw MA-name-string       MA-name-string
                  +--rw MA-name-format?      identityref
                  +--rw (MA-name)?
                  |  +--:(MA-name-null)
                  |     +--rw MA-name-null?        empty</artwork>
        </figure>
      </section>

      <section title="Maintenance Endpoint (MEP) configuration">
        <t>Within a given Maintenance Association (MA), there can be one or
        more Maintenance End Points (MEP). MEPs are represented as a list
        within the data hierarchy and indexed by the key MEP-name.</t>

        <figure title="Snippet of data hierarchy related to Maintenance Endpoint (MEP) ">
          <artwork>   module: ietf-gen-oam
      +--rw domains
         +--rw domain* [technology MD-name-string]
            +--rw technology        identityref
            .
            .
            +--rw MAs
               +--rw MA* [MA-name-string]
                  +--rw MA-name-string       MA-name-string
                  .
                  .
                  +--rw MEP* [mep-name]
                  |  +--rw mep-name             MEP-name
                  |  +--rw (MEP-ID)?
                  |  |  +--:(MEP-ID-int)
                  |  |     +--rw MEP-ID-int?          int32
                  |  |  +--:(MEP-ID-tlv)
                  |  |     +--rw MEP-ID-type?         int16
                  |  |     +--rw MEP-ID-len?          int16
                  |  |     +--rw MEP-ID-value?        binary
                  |  +--rw MEP-ID-format?       identityref
                  |  +--rw (mp-address)?
                  |  |  +--:(mac-address)
                  |  |  |  +--rw mac-address?   yang:mac-address
                  |  |  +--:(ipv4-address)
                  |  |  |  +--rw ipv4-address?  inet:ipv4-address
                  |  |  +--:(ipv6-address)
                  |  |     +--rw ipv6-address?  inet:ipv6-address
       .          .
       .          .
       .          .</artwork>
        </figure>
      </section>

      <section title="rpc definitions">
        <t>The rpc model facilitates issuing commands to a NETCONF server (in
        this case to the device that need to execute the OAM command) and
        obtain a response. rpc model defined here abstracts OAM specific
        commands in a technology independent manner.</t>

        <t>There are several rpc commands defined for the purpose of OAM. In
        this section we present a snippet of the ping command for illustration
        purposes. Please refer to Section 4 for the complete data hierarchy
        and Section 5 for the YANG model.</t>

        <figure title="Snippet of data hierarchy related to rpc call continuity-check">
          <artwork>   module: ietf-gen-oam
      +--rw domains
            +--rw domain* [technology MD-name-string]
            +--rw technology        identityref
      .
      .
   rpcs:
      +---x continuity-check
      |  +--ro input
      |  |  +--ro technology             identityref
      |  |  +--ro MD-name-string         MD-name-string
      |  |  +--ro MA-name-string?        MA-name-string
      |  |  +--ro (flow-entropy)?
      |  |  |  +--:(flow-entropy-null)
      |  |  |     +--ro flow-entropy-null?     empty
      |  |  +--ro priority?              uint8
      |  |  +--ro ttl?                   uint8
      |  |  +--ro session-type           enumeration
      |  |  +--ro ecmp-choice?           ecmp-choices
      |  |  +--ro sub-type?              identityref
      |  |  +--ro outgoing-interfaces* [interface]
      |  |  |  +--ro interface          if:interface-ref
      |  |  +--ro source-mep?            MEP-name
      |  |  +--ro destination-mp
      |  |  |  +--ro (mp-address)?
      |  |  |  |  +--:(mac-address)
      |  |  |  |  |  +--ro mac-address?     yang:mac-address
      |  |  |  |  +--:(ipv4-address)
      |  |  |  |  |  +--ro ipv4-address?    inet:ipv4-address
      |  |  |  |  +--:(ipv6-address)
      |  |  |  |     +--ro ipv6-address?    inet:ipv6-address
      |  |  |  +--ro (MEP-ID)?
      |  |  |  |  +--:(MEP-ID-int)
      |  |  |  |     +--ro MEP-ID-int?      int32
      |  |  |  +--ro MEP-ID-format?   identityref
      |  |  +--ro count?                 uint32
      |  |  +--ro interval?              Interval
      |  |  +--ro packet-size?           uint32
      |  +--ro output
      |     +--ro tx-packt-count?    oam-counter32
      |     +--ro rx-packet-count?   oam-counter32
      |     +--ro min-delay?         oam-counter32
      |     +--ro average-delay?     oam-counter32
      |     +--ro max-delay?         oam-counter32</artwork>
        </figure>
      </section>

      <section title="OAM data hierarchy">
        <t>The complete data hierarchy related to the OAM YANG model is
        presented below. The following notations are used within the data tree
        and carry the meaning as below.</t>

        <t>Each node is printed as:<figure>
            <artwork>
<status> <flags> <name> <opts> <type>

<status> is one of:
     +  for current
     x  for deprecated
     o  for obsolete


<flags> is one of:

    rw for configuration data 
    ro for non-configuration data
    -x for rpcs
    -n for notifications


<name> is the name of the node</artwork>
          </figure></t>

        <t>If the node is augmented into the tree from another module, its
        name is printed as <prefix>:<name>. <figure>
            <artwork><opts> is one of:

     ?  for an optional leaf or choice
     !  for a presence container
     *  for a leaf-list or list
     [<keys>] for a list's keys

<type> is the name of the type for leafs and leaf-lists</artwork>
          </figure></t>

        <figure title="data hierarchy of OAM">
          <artwork>
module: ietf-gen-oam
   +--rw domains
      +--rw domain* [technology MD-name-string]
         +--rw technology        identityref
         +--rw MD-name-string    MD-name-string
         +--rw MD-name-format?   identityref
         +--rw (MD-name)?
         |  +--:(MD-name-null)
         |     +--rw MD-name-null?     empty
         +--rw md-level?         MD-level
         +--rw MAs
            +--rw MA*  [MA-name-string]
               +--rw MA-name-string       MA-name-string
               +--rw MA-name-format?      identityref
               +--rw (MA-name)?
               |  +--:(MA-name-null)
               |     +--rw MA-name-null?        empty
               +--rw (connectivity-context)?
               |  +--:(context-null)
               |     +--rw context-null?        empty
               +--rw mep-direction        MEP-direction
               +--rw interval?            Interval
               +--rw loss-threshold?      uint32
               +--rw ttl?                 uint8
               +--rw (flow-entropy)?
               |  +--:(flow-entropy-null)
               |     +--rw flow-entropy-null?   empty
               +--rw priority?            uint8
               +--rw MEP* [mep-name]
               |  +--rw mep-name             MEP-name
               |  +--rw (MEP-ID)?
               |  |  +--:(MEP-ID-int)
               |  |  |  +--rw MEP-ID-int?          int32
               |  |  +--:(MEP-ID-tlv)
               |  |     +--rw MEP-ID-type?         int16
               |  |     +--rw MEP-ID-len?          int16
               |  |     +--rw MEP-ID-value?        binary
               |  +--rw MEP-ID-format?       identityref
               |  +--rw (mp-address)?
               |  |  +--:(mac-address)
               |  |  |  +--rw mac-address?         yang:mac-address
               |  |  +--:(ipv4-address)
               |  |  |  +--rw ipv4-address?        inet:ipv4-address
               |  |  +--:(ipv6-address)
               |  |     +--rw ipv6-address?        inet:ipv6-address
               |  +--rw (connectivity-context)?
               |  |  +--:(context-null)
               |  |     +--rw context-null?        empty
               |  +--rw Interface?                 if:interface-ref
               |  +--rw (topology)?
               |  |  +--:(topo-null)
               |  |     +--rw topo-null?           empty
               |  +--ro admin-status?        leafref
               |  +--ro oper-status?         leafref
               |  +--rw (flow-entropy)?
               |  |  +--:(flow-entropy-null)
               |  |     +--rw flow-entropy-null?   empty
               |  +--rw priority?            uint8
               |  +--rw session* [session-cookie]
               |     +--rw session-cookie             uint32
               |     +--rw ttl?                       uint8
               |     +--rw interval?                  Interval
               |     +--rw enable?                    boolean
               |     +--rw ecmp-choice?               ecmp-choices
               |     +--rw source-mep?                MEP-name
               |     +--rw destination-mep
               |     |  +--rw (MEP-ID)?
               |     |  |  +--:(MEP-ID-int)
               |     |  |  |  +--rw MEP-ID-int?      int32
               |     |  |  +--:(MEP-ID-tlv)
               |     |  |     +--rw MEP-ID-type?     int16
               |     |  |     +--rw MEP-ID-len?      int16
               |     |  |     +--rw MEP-ID-value?    binary
               |     |  +--rw MEP-ID-format?         identityref
               |     +--rw destination-mep-address
               |     |  +--rw (mp-address)?
               |     |     +--:(mac-address)
               |     |     |  +--rw mac-address?    yang:mac-address
               |     |     +--:(ipv4-address)
               |     |     |  +--rw ipv4-address?   inet:ipv4-address
               |     |     +--:(ipv6-address)
               |     |        +--rw ipv6-address?   inet:ipv6-address
               |     +--rw (connectivity-context)?
               |     |  +--:(context-null)
               |     |     +--rw context-null?              empty
               |     +--rw (flow-entropy)?
               |     |  +--:(flow-entropy-null)
               |     |     +--rw flow-entropy-null?         empty
               |     +--rw priority?                  uint8
               |     +--rw outgoing-interface* [interface]
               |        +--rw interface         leafref
               +--rw MIP* [interface]
               |  +--rw interface               if:interface-ref
               +--rw related-oam-layer* [offset]
                  +--rw offset            int32
                  +--rw technology        identityref
                  +--rw MD-name-string    MD-name-string
                  +--rw MA-name-string?   MA-name-string
rpcs:
   +---x continuity-check           
   |  +--ro input     
   |  |  +--ro technology             identityref
   |  |  +--ro MD-name-string         MD-name-string
   |  |  +--ro MA-name-string?        MA-name-string
   |  |  +--ro (flow-entropy)?
   |  |  |  +--:(flow-entropy-null)
   |  |  |     +--ro flow-entropy-null?     empty
   |  |  +--ro priority?              uint8
   |  |  +--ro ttl?                   uint8
   |  |  +--ro session-type-enum?     enumeration
   |  |  +--ro ecmp-choice?           ecmp-choices
   |  |  +--ro sub-type?              identityref
   |  |  +--ro outgoing-interfaces* [interface]
   |  |  |  +--ro interface           if:interface-ref
   |  |  +--ro source-mep?            MEP-name
   |  |  +--ro destination-mp
   |  |  |  +--ro (mp-address)?
   |  |  |  |  +--:(mac-address)
   |  |  |  |  |  +--ro mac-address?     yang:mac-address
   |  |  |  |  +--:(ipv4-address)
   |  |  |  |  |  +--ro ipv4-address?    inet:ipv4-address
   |  |  |  |  +--:(ipv6-address)
   |  |  |  |     +--ro ipv6-address?    inet:ipv6-address
   |  |  |  +--ro (MEP-ID)?
   |  |  |  |  +--:(MEP-ID-int)
   |  |  |  |  |  +--ro MEP-ID-int?      int32
   |  |  |  |  +--:(MEP-ID-tlv)
   |  |  |  |     +--ro MEP-ID-type?     int16
   |  |  |  |     +--ro MEP-ID-len?      int16
   |  |  |  |     +--ro MEP-ID-value?    binary
   |  |  |  +--ro MEP-ID-format?      identityref
   |  |  +--ro count?                 uint32
   |  |  +--ro interval?              Interval
   |  |  +--ro packet-size?           uint32
   |  +--ro output    
   |     +--ro tx-packt-count?    oam-counter32
   |     +--ro rx-packet-count?   oam-counter32
   |     +--ro min-delay?         oam-counter32
   |     +--ro average-delay?     oam-counter32
   |     +--ro max-delay?         oam-counter32
   +---x continuity-verification     {connectivity-verification}?
   |  +--ro input     
   |  |  +--ro technology             identityref
   |  |  +--ro MD-name-string         MD-name-string
   |  |  +--ro MA-name-string?        MA-name-string
   |  |  +--ro (flow-entropy)?
   |  |  |  +--:(flow-entropy-null)
   |  |  |     +--ro flow-entropy-null?     empty
   |  |  +--ro priority?              uint8
   |  |  +--ro ttl?                   uint8
   |  |  +--ro session-type-enum?     enumeration
   |  |  +--ro ecmp-choice?           ecmp-choices
   |  |  +--ro sub-type?              identityref
   |  |  +--ro outgoing-interfaces* [interface]
   |  |  |  +--ro interface           if:interface-ref
   |  |  +--ro source-mep?            MEP-name
   |  |  +--ro destination-mp
   |  |  |  +--ro (mp-address)?
   |  |  |  |  +--:(mac-address)
   |  |  |  |  |  +--ro mac-address?     yang:mac-address
   |  |  |  |  +--:(ipv4-address)
   |  |  |  |  |  +--ro ipv4-address?    inet:ipv4-address
   |  |  |  |  +--:(ipv6-address)
   |  |  |  |     +--ro ipv6-address?    inet:ipv6-address
   |  |  |  +--ro (MEP-ID)?
   |  |  |  |  +--:(MEP-ID-int)
   |  |  |  |  |  +--ro MEP-ID-int?      int32
   |  |  |  |  +--:(MEP-ID-tlv)
   |  |  |  |     +--ro MEP-ID-type?     int16
   |  |  |  |     +--ro MEP-ID-len?      int16
   |  |  |  |     +--ro MEP-ID-value?    binary
   |  |  |  +--ro MEP-ID-format?      identityref
   |  |  +--ro count?                 uint32
   |  |  +--ro interval?              Interval
   |  |  +--ro packet-size?           uint32
   |  +--ro output    
   |     +--ro tx-packt-count?    oam-counter32
   |     +--ro rx-packet-count?   oam-counter32
   |     +--ro min-delay?         oam-counter32
   |     +--ro average-delay?     oam-counter32
   |     +--ro max-delay?         oam-counter32
   +---x path-discovery             
      +--ro input     
      |  +--ro technology             identityref
      |  +--ro MD-name-string         MD-name-string
      |  +--ro MA-name-string?        MA-name-string
      |  +--ro (flow-entropy)?
      |  |  +--:(flow-entropy-null)
      |  |     +--ro flow-entropy-null?     empty
      |  +--ro priority?              uint8
      |  +--ro ttl?                   uint8
      |  +--ro session-type-enum?     enumeration
      |  +--ro command-sub-type?      identityref
      |  +--ro ecmp-choice?           ecmp-choices
      |  +--ro outgoing-interfaces* [interface]
      |  |  +--ro interface           if:interface-ref
      |  +--ro source-mep?            MEP-name
      |  +--ro destination-mp
      |  |  +--ro (mp-address)?
      |  |  |  +--:(mac-address)
      |  |  |  |  +--ro mac-address?     yang:mac-address
      |  |  |  +--:(ipv4-address)
      |  |  |  |  +--ro ipv4-address?    inet:ipv4-address
      |  |  |  +--:(ipv6-address)
      |  |  |     +--ro ipv6-address?    inet:ipv6-address
      |  |  +--ro (MEP-ID)?
      |  |  |  +--:(MEP-ID-int)
      |  |  |  |  +--ro MEP-ID-int?      int32
      |  |  |  +--:(MEP-ID-tlv)
      |  |  |     +--ro MEP-ID-type?     int16
      |  |  |     +--ro MEP-ID-len?      int16
      |  |  |     +--ro MEP-ID-value?    binary
      |  |  +--ro MEP-ID-format?      identityref
      |  +--ro count?                 uint32
      |  +--ro interval?              Interval
      +--ro output    
         +--ro response* [response-index]
            +--ro response-index     uint8
            +--ro ttl?               uint8
            +--ro destination-mp
            |  +--ro (mp-address)?
            |  |  +--:(mac-address)
            |  |  |  +--ro mac-address?     yang:mac-address
            |  |  +--:(ipv4-address)
            |  |  |  +--ro ipv4-address?    inet:ipv4-address
            |  |  +--:(ipv6-address)
            |  |     +--ro ipv6-address?    inet:ipv6-address
            |  +--ro (MEP-ID)?
            |  |  +--:(MEP-ID-int)
            |  |  |  +--ro MEP-ID-int?      int32
            |  |  +--:(MEP-ID-tlv)
            |  |     +--ro MEP-ID-type?     int16
            |  |     +--ro MEP-ID-len?      int16
            |  |     +--ro MEP-ID-value?    binary
            |  +--ro MEP-ID-format?   identityref
            +--ro tx-packt-count?    oam-counter32
            +--ro rx-packet-count?   oam-counter32
            +--ro min-delay?         oam-counter32
            +--ro average-delay?     oam-counter32
            +--ro max-delay?         oam-counter32
notifications:
   +---n defect-condition-notification    
      +--ro technology          identityref
      +--ro MD-name-string      MD-name-string
      +--ro MA-name-string?     MA-name-string
      +--ro mep-name?           MEP-name
      +--ro defect-type?        identityref
      +--ro generating-mepid
      |  +--ro (MEP-ID)?
      |  |  +--:(MEP-ID-int)
      |  |  |  +--ro MEP-ID-int?      int32
      |  |  +--:(MEP-ID-tlv)
      |  |     +--ro MEP-ID-type?     int16
      |  |     +--ro MEP-ID-len?      int16
      |  |     +--ro MEP-ID-value?    binary
      |  +--ro MEP-ID-format?         identityref
      +--ro (error)?
         +--:(error-null)
         |  +--ro error-null?         empty
         +--:(error-code)
            +--ro error-code?         int3
            +--ro error-code?         int32
             
</artwork>
        </figure>
      </section>
    </section>

    <section title="OAM YANG Module">
      <t><CODE BEGINS> file "ietf-gen-oam.yang"</t>

      <figure title="YANG module of OAM">
        <artwork>   module ietf-gen-oam {
  namespace "urn:ietf:params:xml:ns:yang:ietf-gen-oam";
  prefix goam;

  import ietf-interfaces {
    prefix if;
  }
  import ietf-yang-types {
    prefix yang;
  }
  import ietf-inet-types {
    prefix inet;
  }

  organization "IETF LIME Working Group";
  contact
    "Tissa Senevirathne tsenevir@cisco.com";
  description
    "This YANG module defines the generic configuration,
     statistics and rpc for OAM to be used within IETF in
     a protocol indpendent manner. Functional level
     abstraction is indendent with YANG modeling. It is
     assumed that each protocol maps corresponding
     abstracts to its native format.
     Each protocol may extend the YANG model defined
     here to include protocol specific extensions";

  revision 2015-04-09 {
    description
      "Initial revision. - 04 version";
    reference "draft-tissa-lime-oam";
  }

  /* features */
  feature connectivity-verification {
    description
      "This feature indicates that the server supports
       executing connectivity verification OAM command and 
       returning a response. Servers that do not advertise 
       this feature will not support executing 
       connectivity verification command or rpc model for
       connectivity verification command.";    
  }

  /* Identities */

  identity technology-types {
    description
      "this is the base identy of technology types which are
       vpls, nvo3, TRILL, ipv4, ipv6, mpls, etc";
  }

  identity ipv4 {
    base technology-types;
    description
      "technology of ipv4";
  }


  identity ipv6 {
    base technology-types;
    description
      "technology of ipv6";
  }

  identity command-sub-type {
    description
      "defines different rpc command subtypes, e.g rfc792 IP 
       ping, rfc4379 LSP ping, rfc6905 trill OAM, this is
       optional for most cases";
  }

  identity icmp-rfc792 {
    base command-sub-type;
    description
      "Defines the command subtypes for ICMP ping";
    reference "RFC 792";
  }

  identity name-format {
    description
      "This defines the name format, IEEE 8021Q CFM defines varying
      styles of names. It is expected name format as an identity ref
      to be extended with new types.";
  }

  identity name-format-null {
    base name-format;
    description
      "defines name format as null";
  }

  identity identifier-format {
    description
      "identifier-format identity can be augmented to define other
     format identifiers used in MEPD-ID etc";
  }

  identity identifier-format-integer {
    base identifier-format;
    description
      "defines identifier-format to be integer";
  }

  identity defect-types {
    description
      "defines different defect types, e.g. remote rdi, 
       mis-connection defect, loss of continuity";
  }

  /* typedefs */
  typedef MEP-direction {
    type enumeration {
      enum "Up" {
        value 0;
	description
	  "UP direction.";
      }
      enum "Down" {
        value 1;
	description
	  "Down direction.";

      }
    }
    description
      "MEP direction.";
  }

  typedef MEP-name {
    type string;
    description
      "Generic administrative name for a MEP";
  }

  typedef Interval {
    type uint32;
    units "milliseconds";
    default "1000";
    description
      "Interval between packets in milliseconds.
       0 means no packets are sent.";
  }

  typedef ecmp-choices {
    type enumeration {
      enum "ecmp-use-platform-hash" {
        value 0;
	description
	  "Use Platform hashing.";
      }
      enum "ecmp-use-round-robin" {
        value 1;
	description
	  "Use round robin hashing.";
      }
    }
    description
      "Equal cost multi Path Choices";
  }

  typedef MD-name-string {
    type string;
    default "";
    description
      "Generic administrative name for an MD";
  }

  typedef MA-name-string {
    type string;
    default "";
    description
      "Generic administrative name for an MA";
  }

  typedef oam-counter32 {
    type yang:zero-based-counter32;
    description
      "defines 32 bit counter for OAM";
  }

  typedef MD-level {
    type uint32 {
      range "0..255";
    }
    description
      "Maintenance Domain level.  The level may be restricted in
       certain protocols (eg to 0-7)";
  }

  /* groupings */

  grouping topology {
    choice topology {
      case topo-null {
        description
          "this is a placeholder when no topology is needed";
        leaf topo-null {
           type empty;
           description
             "there is no topology define, it will be defined 
              in technology specific model.";
        }
      }
      description
        "Topology choices";
    }
    description
      "Topology";
  }

  grouping error-message {
    choice error {
      case error-null {
        description
          "this is a placeholder when no error status is needed";
        leaf error-null {
           type empty;
           description
             "there is no error define, it will be defined in
              technology specific model.";
        }
      }
      case error-code {
        description
          "this is a placeholder to display error code.";
        leaf error-code {
           type int32;
           description
             "error code is integer value specific to technology.";
        }
      }
      description
        "Error Message choices."; 
    }
    description
      "Error Message.";
  }

  grouping mp-address {
    choice mp-address {
      case mac-address {
        leaf mac-address {
          type yang:mac-address;
	  description
	    "MAC Address";
        }
	description
	  "MAC Address based MP Addressing.";
      }
      case ipv4-address {
        leaf ipv4-address {
          type inet:ipv4-address;
	  description
	    "Ipv4 Address";
        }
	description
	  "Ip Address based MP Addressing.";
      }
      case ipv6-address {
        leaf ipv6-address {
          type inet:ipv6-address;
	  description
	    "Ipv6 Address";
        }
	description
	  "ipv6 Address based MP Addressing.";
      }
      description
        "MP Addressing.";
    }
    description
      "MP Address";
  }   

  grouping maintenance-domain-id {
    description
      "Grouping containing leaves sufficient to identify an MD";
    leaf technology {
      type identityref {
        base technology-types;
      }
      mandatory true;

      description
        "Defines the technology";
    }
    leaf MD-name-string {
      type MD-name-string;
      mandatory true;
      description
        "Defines the generic administrative maintenance domain name";
    }
  }

  grouping MD-name {
    leaf MD-name-format {
      type identityref {
        base name-format;
      }
      description
        "Name format.";
    }
    choice MD-name {
      case MD-name-null {
        leaf MD-name-null {
	  when "../../../MD-name-format = name-format-null" {
	     description
	       "MD name format is equal to null format.";
	  }
          type empty;
	  description
	    "MD name Null.";
        }
      }
      description
        "MD name.";
    }
    description
      "MD name";
  }

  grouping ma-identifier {
    description
      "Grouping containing leaves sufficient to identify an MA";
    leaf MA-name-string {
      type MA-name-string;
      description
        "MA name string.";
    }
  }

  grouping MA-name {
    description
      "MA name";
    leaf MA-name-format {
      type identityref {
        base name-format;
      }
      description
        "Ma name format";
    }
    choice MA-name {
      case MA-name-null {
        leaf MA-name-null {
          when "../../../MA-name-format = name-format-null" {
	  description
	    "MA";
	  }
	  type empty;
	  description
	    "empty";
        }
      }
      description 
        "MA name";
    }
  }

  grouping MEP-ID {
    choice MEP-ID {
      default "MEP-ID-int";
      case MEP-ID-int {
        leaf MEP-ID-int {
          type int32;
	  description
	    "MEP ID in integer format";
        }
      }
      case MEP-ID-tlv {
         leaf MEP-ID-type {
	   type int16;
	   description
	     "Type of MEP-ID";
         }
	 leaf MEP-ID-len {
	   type int16;
	   description
	     "Length of MEP-ID value";
	 }
	 leaf MEP-ID-value {
	    type binary {
	      length "12..255";
	    }
	    description
	      "Value please refer RFC6428.";
	 }
      }
      description
        "MEP-ID";
    }
    leaf MEP-ID-format {
      type identityref {
        base identifier-format;
      }
      description
        "MEP ID format.";
    }
    description
      "MEP-ID";
  }

  grouping MEP {
    description
      "Defines elements within the MEP";
    leaf mep-name {
      type MEP-name;
      mandatory true;
      description
        "Generic administrative name of the MEP";
    }
    uses MEP-ID;

    uses mp-address;
    uses connectivity-context;
    leaf Interface {
      type if:interface-ref;
      description
        "Interface name as defined by ietf-interfaces";
    }
    uses topology;
  }

  grouping session-type {
    description
      "This object indicates the current session
       definition.";
    leaf session-type-enum {
      type enumeration {
        enum proactive {
          description
            "The current session is proactive";
        }
        enum on-demand {
          description
            "The current session is on-demand.";
        }
      }
      description
        "session type enum";
    }
  }

  grouping monitor-stats {
    leaf tx-packt-count {
      type oam-counter32;
      description
        "Transmitted Packet count";
    }
    leaf rx-packet-count {
      type oam-counter32;
      description
        "Received packet count";
    }
    leaf min-delay {
      type oam-counter32;
      units milliseconds;
      description
        "Delay is specified in milliseconds";
    }
    leaf average-delay {
      type oam-counter32;
      units millisecond;
      description
        "average delay in milliseconds";
    }
    leaf max-delay {
      type oam-counter32;
      units millisecond;
      description
        "Maximum delay in milliseconds";
    }
    description
      "Monitor Statistics";
  }

  grouping MIP {
    description
      "defines MIP";
    leaf interface {
      type if:interface-ref;
      description
         "Interface";
    }
  }

  grouping related-oam-layer {
    leaf offset {
      type int32 {
        range "-255..255";
      }
      description
        "defines offset (in MD levels) to a related OAM layer
         +1 is the layer immediately above
         -1 is the layer immediately below";
    }
    uses maintenance-domain-id;
    uses ma-identifier;
    description
      "related OAM layer";
  }

  grouping interface-status {
    description
      "collection of interface related status";
    leaf admin-status {
      type leafref {
        path "/if:interfaces-state/if:interface/if:admin-status";
      }
      config false;
      description
        "oper status from ietf-interface module";
    }
    leaf oper-status {
      type leafref {
        path "/if:interfaces-state/if:interface/if:oper-status";
      }
      config false;
      description
        "oper status from ietf-interface module";
    }
  }

  grouping connectivity-context {
    description
      "Grouping defining the connectivity context for an MA; for
       example, a VRF for IP, or an LSP for MPLS.  This will be
       augmented by each protocol who use this component";
    choice connectivity-context {
      default "context-null";
      case context-null {
        description
          "this is a place holder when no context is needed";
        leaf context-null {
          type empty;
          description
            "there is no context define";
        }
      }
      description
        "connectivity context";
    }
  }

  grouping priority {
    description
      "Priority used in transmitted packets; for example, in the
       TOS/DSCP field in IP or the Traffic Class field in MPLS";
    leaf priority {
      type uint8;
      description
        "priority";
    }
  }

  grouping flow-entropy {
    description
      "defines the grouping statement for flow-entropy";
    choice flow-entropy {
      default "flow-entropy-null";
      case flow-entropy-null {
        description
          "this is a place holder when no flow entropy is needed";
        leaf flow-entropy-null {
          type empty;
          description
            "there is no flow entropy defined";
        }
      }
      description
        "Flow entropy";
    }
  }

  grouping measurement-timing-group {
     description
     "This grouping includes objects used for 
      proactive and on-demand
      scheduling of PM measurement sessions.";

     container start-time {
        description
	"This container defines the session start time.";
	choice start-time {
	  description
	  "Measurement sessions tart time can be immediate, relative, or
	  absolute.";
	  container immediate {
            presence "Start the measurement session immediately.";
            description
            "Start Time of probe immediately.";
	  }
	  leaf absolute {
	    type yang:date-and-time;
	    description
	    "This objects specifies the scheduled start time
	     to perform the on-demand monitoring operations.";
	  }
        }
     }
 
     container stop-time {
	description 
	"This container defines the session stop time.";
	choice stop-time {
	   description
	   "Measurement session stop time can be none, or absolute.";
	   container none {
              presence "Never end the measurement session.";
              description
              "Stop time is never to end.";
	      
	   }

	   leaf absolute {
	     type yang:date-and-time;
	     description
	       "This objects specifies the scheduled stop time
	         to perform the on-demand monitoring operations.";
	   }
        }
     }
  }

  container domains {
    description
      "Contains configuration related data. Within the container
       is list of fault domains. Wihin each domian has List of MA.";
    list domain {
      key "technology MD-name-string";
      ordered-by system;
      description
        "Define the list of Domains within the IETF-OAM";
      uses maintenance-domain-id;
      uses MD-name;
      leaf md-level {
        type MD-level;
        description
          "Defines the MD-Level";
      }
      container MAs {
        description
          "This container defines MA, within that have multiple MA
           and within MA have MEP, MIP";
        list MA {
	  key "MA-name-string";
          ordered-by system;
          uses ma-identifier;
          uses MA-name;
          uses connectivity-context;
          leaf mep-direction {
            type MEP-direction;
            mandatory true;
            description
              "Direction for MEPs in this MA";
          }
          leaf interval {
	    type Interval;
            default "0";
            description
              "Defines default Keepalive/CC Interval.  May be
               overridden for specific sessions if supported by the
               protocol.";
          }
          leaf loss-threshold {
	    type uint32;
            default "3";
            description
              "number of consecutive Keepalive/CC messages missed
               before declaring loss of continuity fault. This is
               monitored per each remote MEP session";
          }
          leaf ttl {
            type uint8;
            default "255";
	    description
	      "Time to Live";
          }
          uses flow-entropy {
            description
              "Default flow entropy in this MA, which may be
               overridden for particular MEPs, sessions or
               operations";
          }
          uses priority {
            description
              "Default priority for this MA, which may be overridden
               for particular MEPs, sessions or operations.";
          }
          list MEP {
            key "mep-name";
            ordered-by system;
            description
              "contain list of MEPS";
            uses MEP;
            uses interface-status {
              description
                "status of associated interface";
            }
            uses flow-entropy;
            uses priority;
            list session {
              key "session-cookie";
              ordered-by user;
              description
                "Monitoring session to/from a particular remote MEP.
                 Depending on the protocol, this could represent CC
                 messages received from a single remote MEP (if the
                 protocol uses multicast CCs) or a target to which
                 unicast echo request CCs are sent and from which
                 responses are received (if the protocol uses a
                 unicast request/response mechanism).";
              leaf session-cookie {
                type uint32;
                description
                  "Cookie to identify different sessions, when there
                   are multiple remote MEPs or multiple sessions to
                   the same remote MEP.";
              }
              leaf ttl {
                type uint8;
                default "255";
		description
		  "Time to Live.";
              }
              leaf interval {
                type Interval;
                description
                  "Transmission interval for CC packets for this
                   session.";
              }
              leaf enable {
	        type boolean;
                default "false";
                description
                  "enable or disable a monitor session";
              }
              leaf ecmp-choice {
                type ecmp-choices;
                description
                  "0 means use the specified interface
                   1 means use round robin";
              }
              leaf source-mep {
                type MEP-name;
                description
                  "Source MEP for this session, if applicable";
              }
              container destination-mep {
                uses MEP-ID;
		description
		   "Destination MEP";
              }
              container destination-mep-address {
                uses mp-address;
		description
		   "Destination MEP Address";
              }
              uses connectivity-context;
              uses flow-entropy;
              uses priority;
              list outgoing-interface {
                key "interface";
                leaf interface {
                  type leafref {
                    path "/if:interfaces/if:interface/if:name";
                  }
		  description
		    "Outgoing Interface";
                }
		description
		  "outgoing interfaces";
              }
            }
          }
          list MIP {
            key "interface";
            uses MIP;
	    description
	      "Maintenance Intermediate Point";
          }
          list related-oam-layer {
            key "offset";
            description
              "List of OAM layers above and below that are related to
               current MA. This allow users to easily navigate up and
               down to efficiently troubleshoot a connectivity
               issue";
            uses related-oam-layer;
          }
	  description
	     "Maintenance Association list";
        }
      }
    }
  }

  notification defect-condition-notification {
    description
      "When defect condition is met this notificiation is sent";
   uses maintenance-domain-id {
      description
        "defines the MD (Maintenance Domain) identifier, which is the
         Generic MD-name-string and the technology.";
    }
    uses ma-identifier;
    leaf mep-name {
      type MEP-name;
      description
        "Indicate which MEP is seeing the error";
    }
    leaf defect-type {
      type identityref {
        base defect-types;
      }
      description
        "The currently active defects on the specific MEP.";
    }
    container generating-mepid {
      uses MEP-ID;
      description
        "Who is generating the error (if known) if 
         unknown make it 0.";
    }
    uses error-message {
      description
         "Error message to indicate more details.";
    } 
  }
  rpc continuity-check {
    description
      "Generates continuity-check as per RFC7276 Table 4.";
    input {
      uses maintenance-domain-id {
        description
          "defines the MD (Maintenance Domain) identifier, which is
           the generic
           MD-name-string and the technology.";
      }
      uses ma-identifier {
        description
          "identfies the Maintenance association";
      }
      uses flow-entropy;
      uses priority;
      leaf ttl {
        type uint8;
        default "255";
	description
	  "Time to Live";
      }
      uses session-type;
      leaf ecmp-choice {
        type ecmp-choices;
        description
          "0 means use the specified interface
           1 means use round robin";
      }
      leaf sub-type {
        type identityref {
          base command-sub-type;
        }
        description
          "defines different command types";
      }
      list outgoing-interfaces {
        key "interface";
        leaf interface {
          type if:interface-ref;
	  description
	    "outgoing interface";
        }
	description
	  "outgoing Interfaces";
      }
      leaf source-mep {
        type MEP-name;
	description
	  "Source MEP";
      }
      container destination-mp {
        uses mp-address;
        uses MEP-ID {
          description "Only applicable if the destination is a MEP";
        }
	description
	  "Destination MEP";
      }
      leaf count {
        type uint32;
        default "3";
        description


          "Number of ping echo request message to send";
      }
      leaf interval {
        type Interval;
        description
          "Interval between echo requests";
      }
      leaf packet-size {
        type uint32 {
          range "64..10000";
        }
        default "64";
        description
          "Size of ping echo request packets, in octets";
      }
    }
    output {
      uses monitor-stats {
        description
          "Stats of continuity check is same as that of
           monitor sessions";
      }
    }
  }

  rpc continuity-verification {
    if-feature connectivity-verification;
    description
      "Generates continuity-verification as per RFC7276 Table 4.";
    input {
      uses maintenance-domain-id {
        description
          "defines the MD (Maintenance Domain) identifier, which is
           the generic
           MD-name-string and the technology.";
      }
      uses ma-identifier {
        description
          "identfies the Maintenance association";
      }
      uses flow-entropy;
      uses priority;
      leaf ttl {
        type uint8;
        default "255";
	description
	  "Time to Live";
      }
      uses session-type;
      leaf ecmp-choice {
        type ecmp-choices;
        description
          "0 means use the specified interface
           1 means use round robin";
      }
      leaf sub-type {
        type identityref {
          base command-sub-type;
        }
        description
          "defines different command types";
      }
      list outgoing-interfaces {
        key "interface";
        leaf interface {
          type if:interface-ref;
	  description
	    "outgoing interface";
        }
	description
	  "outgoing Interfaces";
      }
      leaf source-mep {
        type MEP-name;
	description
	  "Source MEP";
      }
      container destination-mp {
        uses mp-address;
        uses MEP-ID {
          description "Only applicable if the destination is a MEP";
        }
	description
	  "Destination MEP";
      }
      leaf count {
        type uint32;
        default "3";
        description
          "Number of ping echo request message to send";
      }
      leaf interval {
        type Interval;
        description
          "Interval between echo requests";
      }
      leaf packet-size {
        type uint32 {
          range "64..10000";
        }
        default "64";
        description
          "Size of ping echo request packets, in octets";
      }
    }
    output {
      uses monitor-stats {
        description
          "Stats of continuity check is same as that of
           monitor sessions";
      }
    }
  }
  rpc path-discovery {
    description
      "Generates Trace-route or Path Trace and return response. 
       Referencing RFC7276 for common Toolset name, for IP it's
       Traceroute, for MPLS OAM it's Traceroute mode, for 
       MPLS-TP OAM it's Route Tracing, for Pseudowire OAM it's
       LSP Ping, and for TRILL OAM It's Path Tracing tool.
       Starts with TTL
       of one and increment by one at each hop. Untill destination
       reached or TTL reach max valune";
    input {
      uses maintenance-domain-id {
        description
          "defines the MD (Maintenance Domain) identifier, which is
           the generic MD-name-string and the technology.";
      }
      uses ma-identifier {
        description
          "identfies the Maintenance association";
      }
      uses flow-entropy;
      uses priority;
      leaf ttl {
        type uint8;
        default "255";
	description
	  "Time to Live";
      }
      uses session-type;
      leaf command-sub-type {
        type identityref {


          base command-sub-type;
        }
        description
          "defines different command types";
      }
      leaf ecmp-choice {
        type ecmp-choices;
        description
          "0 means use the specified interface
           1 means use round robin";
      }
      list outgoing-interfaces {
        key "interface";
        leaf interface {
          type if:interface-ref;
	  description
	    "Interface.";
        }
	description
	  "Outgoing interface list.";
      }
      leaf source-mep {
        type MEP-name;
	description
	  "Source MEP";
      }
      container destination-mp {
        uses mp-address;
        uses MEP-ID {
          description "Only applicable if the destination is a MEP";
        }
	description
	  "Destination MEP";
      }
      leaf count {
        type uint32;
        default "1";
        description
          "Number of traceroute probes to send.  In protocols where a
           separate message is sent at each TTL, this is the number
           of packets to send at each TTL.";
      }
      leaf interval {
        type Interval;
        description
          "Interval between echo requests";
      }
    }
    output {
      list response {
        key "response-index";
        leaf response-index {
	  type uint8;
          description
            "Arbitrary index for the response.  In protocols that
             guarantee there is only a single response at each TTL
             (eg IP Traceroute), the TTL can be used as the response
             index.";
        }
        leaf ttl {
          type uint8;
	  description
	    "Time to Live";
        }
	description
	   "Time to Live";
        container destination-mp {
          description "MP from which the response has been received";
          uses mp-address;
          uses MEP-ID {
            description
              "Only applicable if the destination is a MEP";
          }
        }
        uses monitor-stats {
          description
            "If count is 1, there is a single delay value reported.";
        }
      }
      description
        "List of response.";
    }
  }
}

</artwork>
      </figure>

      <t><CODE ENDS></t>
    </section>

    <section title="Base Mode">
      <t>The Base Mode defines default configuration that MUST be present in
      the devices that comply with this document. Base Mode allows users to
      have "zero-touch" experience. Several parameters require technology
      specific definition.</t>

      <section title="MEP Address">
        <t>In the Base Mode of operation, the MEP Address is by default the IP
        address of the interface on which the MEP is located.</t>
      </section>

      <section title="MEP ID for Base Mode">
        <t>In the Base Mode of operation, each device creates a single UP MEP
        associated with a virtual OAM port with no physical layer (NULL PHY).
        The MEPID associated with this MEP is zero (0). The choice of MEP-ID
        zero is explained below.</t>

        <t>MEPID is 2 octet field by default. It is never used on the wire
        except when using CCM. Ping, traceroute and session monitoring does
        not use the MEPID on its message header. It is important to have
        method that can derive MEP ID of base mode in an automatic manner with
        no user intervention. IP address cannot be directly used for this
        purpose as the MEP ID is much smaller field. For Base Mode of
        operation we propose to use MEP ID zero (0) as the default MEP-ID.</t>

        <t>CCM packet use MEP-ID on the payload. CCM MUST NOT be used in the
        Base Mode. Hence CCM MUST be disabled on the Maintenance Association
        of the Base Mode.</t>

        <t>If CCM is required, users MUST configure a separate Maintenance
        association and assign unique value for the corresponding MEP IDs.</t>

        <t>[IEEE802.1Q] CFM defines MEP ID as an unsigned integer in the range
        1 to 8191. In this document we propose to extend the range to 0 to
        65535. Value 0 is reserved for MEP ID of Base Mode operation and MUST
        NOT be used for other purposes.</t>
      </section>

      <section title="Maintenance Domain">
        <t>Default MD-LEVEL is set to 3.</t>
      </section>

      <section title="Maintenance Association">
        <t>MAID [IEEE802.1Q] has a flexible format and includes two parts:
        Maintenance Domain Name and Short MA name. In the Based Mode of
        operation, the value of the Maintenance Domain Name must be the
        character string "GenericBaseMode" (excluding the quotes "). In Base
        Mode operation Short MA Name format is set to 2-octet integer format
        (value 3 in Short MA Format field [IEEE802.1Q]) and Short MA name set
        to 65532 (0xFFFC).</t>
      </section>
    </section>

    <section title="Note">
      <t>This section will be removed or subject to change in the future if
      any agreement is reached. As per investigation of RFC7276 for
      performance Monitoring for Loss and Delay are defined for MPLS
      OAM(RFC6374<xref target="RFC6374"/>), OWAMP (RFC4656<xref
      target="RFC4656"/>) and TWAMP (RFC5357<xref target="RFC5357"/>) and
      TRILL OAM (RFC7456<xref target="RFC7456"/>). In case of Performance
      Monitoring Statistics are common between these technologies thus generic
      Yang model for Performance will be worked out through separate draft
      with Augmentation of Generic LIME model. In case of Other Function, it's
      technology specific and thus should be dealt in technology specific Yang
      model instead of Generic Model. </t>
    </section>

    <section title="Security Considerations">
      <t>The YANG module defined in this memo is designed to be accessed via
      the NETCONF protocol [RFC6241] <xref target="RFC6241"/>. The lowest
      NETCONF layer is the secure transport layer and the
      mandatory-to-implement secure transport is SSH [RFC6242] <xref
      target="RFC6242"/>. The NETCONF access control model [RFC6536] <xref
      target="RFC6536"/> provides the means to restrict access for particular
      NETCONF users to a pre-configured subset of all available NETCONF
      protocol operations and content. </t>

      <t>There are a number of data nodes defined in the YANG module which 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. </t>

      <t>The vulnerable "config true" subtrees and data nodes are the
      following:<figure>
          <artwork>/goam:domains/goam:domain/

/goam:domains/goam:domain/goam:MAs/goam:MA/

/goam:domains/goam:domain/goam:MAs/goam:MA/goam:MEP

/goam:domains/goam:domain/goam:MAs/goam:MA/goam:MEP/goam:session/</artwork>
        </figure></t>

      <t>Unauthorized access to any of these lists can adversely affect OAM
      management system handling of end-to-end OAM and coordination of OAM
      within underlying network layers This may lead to inconsistent
      configuration, reporting, and presentation for the OAM mechanisms used
      to manage the network.</t>
    </section>

    <section title="IANA Considerations">
      <t>This document registers a URI in the IETF XML registry [RFC3688]
      [RFC3688]. Following the format in RFC 3688, the following registration
      is requested to be made: </t>

      <figure>
        <artwork>URI: urn:ietf:params:xml:ns:yang:ietf-gen-oam

Registrant Contact: The IESG.

XML: N/A, the requested URI is an XML namespace.</artwork>
      </figure>

      <t>This document registers a YANG module in the YANG Module Names
      registry [RFC6020]. </t>

      <figure>
        <artwork>name: ietf-gen-oam namespace: urn:ietf:params:xml:ns:yang:ietf-gen-oam
   prefix: goam reference: RFC XXXX</artwork>
      </figure>
    </section>

    <section title="Acknowledgments">
      <t>Giles Heron came up with the idea of developing a YANG model as a way
      of creating a unified OAM API set (interface), work in this document is
      largely an inspiration of that. Alexander Clemm provided many valuable
      tips, comments and remarks that helped to refine the YANG model
      presented in this document.</t>

      <t>Carlos Pignataro, David Ball and others participated and contributed
      to this document.</t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      <reference anchor="RFC792">
        <front>
          <title>Internet Control Message Protocol</title>

          <author fullname="J.Postel" initials="J." surname="Postel">
            <organization/>
          </author>

          <date month="September" year="1981"/>
        </front>

        <seriesInfo name="RFC" value="792"/>
      </reference>

      <?rfc include='reference.RFC.2119'?>

      <?rfc include='reference.RFC.6241'?>

      <?rfc include='reference.RFC.6242'?>

      <?rfc include='reference.RFC.6536'?>

      <?rfc include='reference.RFC.3688'?>

      <?rfc include='reference.RFC.6020'?>
    </references>

    <references title="Informative References">
      <reference anchor="IEEE802.1Q">
        <front>
          <title>Media Access Control (MAC) Bridges and Virtual Bridged Local
          Area Networks</title>

          <author>
            <organization/>
          </author>

          <date month="August" year="2011"/>
        </front>

        <seriesInfo name="IEEE" value="Std 802.1Q-2011"/>
      </reference>

      <reference anchor="Y.1731">
        <front>
          <title>OAM functions and mechanisms for Ethernet based
          networks</title>

          <author>
            <organization/>
          </author>

          <date year="2013"/>
        </front>

        <seriesInfo name="ITU-T" value="Recommendation G.8013/Y.1731"/>
      </reference>

      <?rfc include='reference.RFC.7455'?>

      <?rfc include='reference.RFC.7276'?>

      <?rfc include='reference.RFC.7174'?>

      <?rfc include='reference.RFC.6291'?>

      <?rfc include='reference.RFC.6325'?>

      <?rfc include='reference.RFC.4443'?>

      <?rfc include='reference.RFC.4379'?>

      <?rfc include='reference.RFC.6371'?>

      <?rfc include='reference.RFC.6374'?>

      <?rfc include='reference.RFC.4656'?>

      <?rfc include='reference.RFC.5357'?>

      <?rfc include='reference.RFC.7456'?>
    </references>
  </back>
</rfc>

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