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OPSAWG Working Group                                            N. Sambo
Internet-Draft                                              M. Dallaglio
Intended status: Standards Track                             P. Castoldi
Expires: December 29, 2017                    Scuola Superiore Sant'Anna
                                                             G. Fioccola
                                                            A. Di Giglio
                                                          Telecom Italia
                                                               F. Cugini
                                                                    CNIT
                                                              G. Bernini
                                                             P. Giardina
                                                               Nextworks
                                                           June 27, 2017


      Extending YANG for events, actions, and finite state machine
             draft-sambo-opsawg-ccamp-supa-ext-yang-fsm-00

Abstract

   Network operators and service providers are facing the challenge of
   deployment of systems from different vendors while looking for a
   trade-off among transmission performance, network device reuse, and
   capital expenditure without the need of being tied to single vendor
   equipment.  The deployment and operation of more dynamic and
   programmable transport optical network infrastructures can be driven
   by adopting model-driven and software-defined control and management
   paradigms.  In this context, YANG enables to compile a set of
   consistent vendor-neutral data models for optical networks and
   components based on actual operational needs emerging from
   heterogeneous use cases.  This document extends YANG from data to
   functional modeling in order to describe events, operations, and
   finite state machine of YANG-defined network elements.  The proposed
   models can be applied in the context of optical networks to pre-
   instruct data plane devices (e.g., an optical transponder) on the
   actions to be performed (e.g., code adaptation) in case some events,
   such as physical layer degradations, occur.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.




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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 29, 2017.

Copyright Notice

   Copyright (c) 2017 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Example of application  . . . . . . . . . . . . . . . . . . .   4
   5.  Extending YANG for events and reactions . . . . . . . . . . .   7
   6.  Extending YANG for finite state machine (FSM) . . . . . . . .   9
   7.  Implementation for the considered use case of application . .   9
   8.  Appendix  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  YANG model for events and actions - Tree  . . . . . . . .  10
     8.2.  YANG model for FSM - Tree . . . . . . . . . . . . . . . .  11
     8.3.  YANG model for events and actions - Code  . . . . . . . .  12
     8.4.  YANG model for FSM - Code . . . . . . . . . . . . . . . .  16
     8.5.  Example of values for the YANG model  . . . . . . . . . .  19
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  20
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  20
     11.2.  Informative References . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21








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1.  Introduction

   Networks are evolving toward more programmability, flexibility, and
   multi-vendor interoperability.  Multi-vendor interoperability can be
   applied in the context of nodes, i.e. a node composed of components
   provided by different vendors (named white box) is assembled under
   the same control system.  This way, operators can optimize costs and
   network performance without the need of being tied to single vendor
   equipment.  NETCONF protocol RFC6241 [RFC6241] based on YANG data
   modeling language RFC6020 [RFC6020] is emerging as a candidate
   Software Defined Networking (SDN) enabled protocol.  First, NETCONF
   supports both control and management functionalities, thus permits
   high programmability.  Then, YANG enables data modeling in a vendor-
   neutral way.  Some recent works have provided YANG models to describe
   attributes of links (e.g., identification), nodes (e.g., connectivity
   matrix), media channels, and transponders (e.g., supported forward
   error correction - FEC) of networks
   ([I-D.ietf-i2rs-yang-network-topo] [I-D.vergara-ccamp-flexigrid-yang]
   [I-D.zhang-ccamp-l1-topo-yang]), also including optical technologies.
   Such draft mainly refers to elastic optical networks (EONs), i.e.
   optical networks based on flexible grid where circuits with different
   bandwidth requirements are switched.  EONs are expected to employ
   flexible transponders, i.e. transponders supporting multiple bit
   rates, multiple modulation formats, and multiple codes.  Such
   transponders permits the (re-) configuration of the bit rate value
   based on traffic requirements, as well as the configuration of the
   modulation format and code based on the physical characteristics of a
   path (e.g., quadrature phase shift keying is more robust than 16
   quadrature amplitude modulation).  This document extends YANG from
   data to functional modeling in order to describe events, operations,
   and finite state machine of YANG-defined network elements.  Such
   models can be applied to a case of transponder reconfiguration in
   EONs.  In particular, the model enables a centralized remote network
   controller (managed by a network operator) to instruct a transponder
   controller about the actions to perform when certain events (e.g.,
   failures) occur.  The actions to be taken and the events can be re-
   programmed on the device.

2.  Conventions used in this document

   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 RFC2119 [RFC2119].








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3.  Terminology

   ABNO: Application-Based Network Operations

   BER: Bit Error Rate

   EON: Elastic Optical Network

   FEC: Forward Error Correction

   FSM: Finite State Machine

   NETCONF: Network Configuration Protocol

   OAM: Operation Administration and Maintenance

   SDN: Software Defined Network

   YANG: Yet Another Network Generator

4.  Example of application

   Flexible transponders enable several settings of transmission
   parameters' configuration, through the support of multiple modulation
   formats and forward error correction (FEC) schemes.  This way,
   transmission parameters can be (re-)configured based on the physical
   layer conditions.  The YANG model presented in this draft enables to
   pre-program reconfiguration settings of data plane devices in case of
   failures or physical layer degradations.  In particular, soft
   failures are assumed.  Soft failures imply transmission performance
   degradation, in turns a bit error rate (BER) increase, e.g. due to
   the ageing of some network devices.  Without loosing generality, the
   ABNO architecture is assumed for the control and management of EONs
   (RFC7491 [RFC7491]).  Considering the state of the art, when pre-FEC
   BER passes above a predefined threshold, it is expected that an alarm
   is sent to the OAM Handler, which communicates with the ABNO
   controller that may trigger an SDN controller (that could be the
   Provisioning Manager of ABNO RFC7491 [RFC7491]) for computing new
   transmission parameters.  The involved ABNO modules are shown in the
   simplified ABNO architecture of Fig. 1.  Then, transponders are
   reconfigured.  When alarms related to several connections impacted by
   the soft failure are generated, this procedure may be particularly
   time consuming.  The related workflow for transponder reconfiguration
   is shown in Fig. 2.  The proposed model enables an SDN controller to
   instruct the transponder about reconfiguration of new transmission
   parameters values if a soft failure occurs.  This can be done before
   the failure occurs (e.g., during the connection instantiation phase
   or during the connection service), so that data plane devices can



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   promptly reconfigure themselves without querying the SDN controller
   to trigger an on-demand recovery.  This is expected to speed up the
   recovery process from soft failures.  The related flow chart is shown
   in Fig. 3.

          ___________            ___________
         |  ABNO     |          |   OAM     |
         |controller |  ------  |  Handler  |
         |___________|          |___________|

           |                         |
           |                         |
           |                         |
        ____________                 |
       |    SDN     |                |
       | controller |                |
       |____________|                |
                                     |
            |                        |
            |                        |
            |                        |
          _____________________________
         |            Client           |
         |            network          |
         |_____________________________|


                 Figure 1: Assumed ABNO functional modules























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              _____________________
             |         1           |
             |Sending alarm to the |
             |        OAM Handler  |
             |                     |
             |_____________________|
                       |
                       |
                       |
             _____________________
            |          2          |
            |       Trigger       |
            |  SDN Controller     |
            |                     |
            |_____________________|
                       |
                       |
                       |
             _____________________
            |          3          |
            |   Computation of    |
            |  new transmission   |
            |    parameters       |
            |_____________________|
                      |
                      |
                      |
             _____________________
            |         4           |
            |    Data plane       |
            |    reconfiguration  |
            |                     |
            |_____________________|


      Figure 2: Flow chart of the expected state-of-the-art approach















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             _______________________
            |          1            |
            | Instructing the local |
            |   controller of       |
            |  data plane devices   |
            |_______________________|
                       |
                       |
                       |
             _______________________
            |          2            |
            | Local reconfiguration |
            |     upon failure      |
            |       detection       |
            |_______________________|
                       |
                       |
                       |
             _______________________
            |          3            |
            |                       |
            |     notification      |
            |                       |
            |_______________________|


    Figure 3: Flow chart of the approach exploiting YANG models in this
                                   draft

5.  Extending YANG for events and reactions

   The model extends YANG to define a list of events associated with
   specific reactions.  The related code and tree are shown in the
   Appendix.

 <event>: this element defines an event and it is composed by a set
          of leaves' attributes as follows.
       <name>: this attribute defines the name of the event.
       <type>: this attribute defines the type of the event from
               a pool of possible event types predefined inside
               the YANG model. Together with the <name> attribute,
               it uniquely identifies the event.
       <description>: this optional attribute is a "string" describing
               the event
       <filters>: this leaf is a list that enhances the description
               of an event. Given that an event does not necessary
               means a particular degradation or faults, this list
               can be used to define thresholds to express a measure



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               of the event.
            <filter>: this leaf of <filters> defines a threshold to
                         characterize the event.
            <filter-id>: this leaf of <filters> define the
                         identifier number associated with the <filter>
                         attribute.
       <reaction>: this attribute defines a list of operations to take
               if the event occurs.
               <operations>: this list defines the set of operations
                         that have to be taken if the event occurs.
                           <id>: this leaf of <operations> defines the
                                 identifier number of an operation.
                           <type>: this leaf of <operations> defines
                                 the type of an operation.
                           <simple>: this leaf defines (differently
                                 from <conditional> detailed below) an
                                 operation that has to be directly
                                 executed.
                                  <execute>: this attribute recalls an
                                         RPC encapsulating the effective
                                         task (operation) to be executed
                                         by the data plane hardware.
                                  <next-operation>: this attribute
                                         defines the identification
                                         number of a next operation that
                                         has to be taken.
                           <conditional>: this leaf enables a check
                                 ("true" or "false") to be verified
                                 before executing the operation. Based
                                 on the check, the proper attributes
                                 <execute> and <next-operation> are
                                 considered.
                                  <statement>: this leaf of
                <conditional> defines the
                                        condition to be verified before
                                        executing the operation.
                                  <true>: this leaf of <conditional>
                                         defines a result of the check
                                         associated to <statement>.
                                         Proper <execute> and
                                         <next-operation> attributes are
                                         associated with this result of
                                         the check.
                                  <false>: this leaf of <conditional>
                                         defines a result of the check
                                         associated to <statement>.
                                         Proper <execute> and
                                         <next-operation> attributes are



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                                         associated with this result of
                                         the check.


6.  Extending YANG for finite state machine (FSM)

   This model extends the one of the events and reactions by adding the
   state information and state transition.  More precisely, the model
   defines a list of states associated with events.  Each state has a
   description attribute and it is identified through an id.  Each state
   includes a list of events as defined in the event model, with the
   additional next-state attribute, which points to the next state.  The
   related code and tree are shown in the Appendix.

 <current-state>: it defines the current state of the FSM.
 <states>: this element defines the FSM as follows.
        <state>: this list defines all the FSM states.
              <id>: this leaf attribute of <state> defines the
                    identifier of the state
              <name>: this leaf attribute of <state> defines the name of
                    the state
              <description>: this leaf is a "string" describing the
                    state
              <events>: this attribute is the one described in the
                    previous section. In particular, this attribute
                    defines a list of events that may induce a
                    transition to another state in the FSM.
                     <next-state>: this attribute is included in the
                              model <events> and defines the next state
                              of FSM when an operation is executed.


7.  Implementation for the considered use case of application

   The models defined in this document are an extension of YANG through
   functions, events, and FSM, besides data modeling.  These models can
   be used to enable a centralized network controller, managed by a
   network operator, to instruct data plane hardware on its
   reconfiguration if some events, such as a failure or physical layer
   degradation, occur.  As an example, an optical signal impacted by a
   soft failure (i.e., a physical layer degradation inducing a pre
   forward error correction bit error rate increase - pre-FEC) can be
   maintained by adapting the FEC of the signal itself.  This action to
   be taken and, more in general operations to be executed depending on
   critical events, can be (re-) programmed on the transponder by (re-)
   sending a NETCONF <edit-config> message to the device controller
   including a FSM defined by the YANG model.  Such a system has the
   main goal to speed up the reaction of the network to certain events/



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   faults and to alleviate the workload of the centralized controller.
   The speed up derives from the fact that the centralized controller is
   able to pre-compute and pre-configure on the network devices the
   actions to take when an event occurs taking into account a global
   view and knowledge of the network.  In this way, the device is
   already aware of the actions to be locally applied to reconfigure a
   connection, avoiding to inform the controller and to wait for the
   response indicating what to do.  Consequently, part of the workload
   is also removed from the centralized controller.  When the reaction
   is successfully completed in the data plane, the centralized
   controller can be notified about the faults and the taken action.  A
   flexible transponder supporting two FEC types, 7% and 20%, is
   considered.  A two-states FSM is also assumed.  The states have
   <name> attribute set to "Steady" and "Fec-Baud-Adapt", respectively.
   In the "Steady" state, the signal is in a healthy condition, adopting
   a 7% FEC, with a pre-FEC BER below an assigned threshold of 9 x 10-4.
   A transition from this state can be triggered by the event with
   <name>=BER_CHANGE and <filter-type>=9 x 10-4, thus expressing a
   change of the pre-FEC BER above the threshold.  In case the pre-FEC
   BER exceeds 9 x 10-4 due to a soft failure, the state machine evolves
   to the "Fec-Baud-Adapt" state and an adaptation to a more robust FEC
   of 20% (executed by the attribute <execute>) is performed.  The
   system can return to the "Steady" state if the pre-FEC BER goes below
   another pre-defined threshold and the FEC is reconfigured to 7%.

8.  Appendix

   This appendix reports the YANG models code and the related tree.

8.1.  YANG model for events and actions - Tree





















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   +--rw events
         +--rw event [name type]
            +--rw name           string
            +--rw type           event-type
            +--rw description?   string
            +--rw filters
            |  +--rw filter [filter-id]
            |     +--rw filter-id    yp:filter-id
            +--rw reaction
               +--rw operation [id]
                  +--rw id             event-id-type
                  +--rw type           enumeration
                  +--rw conditional
                  |  +--rw statement    string
                  |  +--rw true
                  |  |  +--rw execute
                  |  |  +--rw next-operation?   event-id-type
                  |  +--rw false
                  |     +--rw execute
                  |     +--rw next-operation?   event-id-type
                  +--rw simple
                     +--rw execute
                     +--rw next-operation?   event-id-type

8.2.  YANG model for FSM - Tree


























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      +--rw current-state?   leafref
      +--rw states
         +--rw state [id]
            +--rw id             state-id-type
            +--rw name             string
            +--rw description?   string
            +--rw events
               +--rw event [name type]
                  +--rw name           string
                  +--rw type           event-type
                  +--rw description?   string
                  +--rw filters
                  |  +--rw filter [filter-id]
                  |     +--rw filter-id    yp:filter-id
                  +--rw reaction
                     +--rw operation [id]
                        +--rw id             event-id-type
                        +--rw type           enumeration
                        +--rw conditional
                        |  +--rw statement    string
                        |  +--rw true
                        |  |  +--rw execute
                        |  |  +--rw next-operation?   event-id-type
                        |  |  +--rw next-state?       leafref
                        |  +--rw false
                        |     +--rw execute
                        |     +--rw next-operation?   event-id-type
                        |     +--rw next-state?       leafref
                        +--rw simple
                           +--rw execute
                           +--rw next-operation?   event-id-type
                           +--rw next-state?       leafref

8.3.  YANG model for events and actions - Code

 module events {
   namespace "http://sssup.it/events";
   prefix ev;

   import ietf-yang-push {
     prefix yp;
   }

   organization
     "Scuola Superiore Sant'Anna Network and Services Laboratory";

   contact
     " Editor: Matteo Dallaglio



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               <mailto:m.dallaglio@sssup.it>
     ";

   description
     "This module contains a YANG definitions of events and generic
      reactions.";

   revision 2016-03-15 {
     description "Initial Revision.";
     reference
       "RFC xxxx: A YANG data model for the description of events and
        reactions";
   }

   // identity statements

   identity EVENT {
       description "Base for all types of event";
   }

   identity ON_CHANGE {
       base EVENT;
       description
         "The event when the database changes.";
   }

   // typedef statements

   typedef event-type {
     type identityref {
       base EVENT;
     }
   }

   typedef event-id-type {
     type uint32;
   }


   // grouping statements
   grouping operation-block {
     leaf id {
       type event-id-type;
     }
     leaf type {
       type enumeration {
         enum CONDITIONAL_OP;
         enum SIMPLE_OP;



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       }
       mandatory true;
     }

     grouping execution-top {
       anyxml execute {
         description "Represent the action to perform";
       }
       leaf next-operation {
         type event-id-type;
         description "the id of the next operation to execute";
       }
     }

     container conditional {
       when "../type = 'CONDITIONAL_OP'";
       leaf statement {
         type string;
         mandatory true;
         description
           "The statement to be evaluated before execution.
           E.g. if a=b";
       }
       container true {
         uses execution-top;
       }
       container false {
         uses execution-top;
       }
     }

     container simple {
       when "../type = 'SIMPLE_OP'";
       description
         "Simple execution of an action without checking any condition";
       uses execution-top;
     }
   }

   grouping operation-top {
     list operation {
       key "id";
       ordered-by user;
       uses operation-block;
     }
   }

   grouping on-change {



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     description
       "Event occuring when a modification of one or more
        objects occurs";

     container filters {
       description
         "This container contains a list of configurable filters
          that can be applied to subscriptions.  This facilitates
          the reuse of complex filters once defined.";
       list filter {
         key "filter-id";
         description
           "A list of configurable filters that can be applied to
            subscriptions.";
         leaf filter-id {
           type yp:filter-id;
           description
             "An identifier to differentiate between filters.";
         }
         uses yp:datatree-filter;
       }
     }
   }

   grouping event-top {
     leaf name {
       type string;
       mandatory true;
     }

     leaf type {
       type event-type;
       mandatory true;
     }

     leaf description {
       type string;
     }

     // list of all possible events
     uses on-change {
       when "type = 'ON_CHANGE'";
     }

     container reaction {
       uses operation-top;
     }
   }



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   grouping events-top {
     container events {
       list event {
         key "name type";
         uses event-top;
       }
     }
   }


   // data definition statements

   uses events-top;

   // extension statements

   // feature statements

   // augment statements

   // rpc statements

   // notification statements


 }//module events


8.4.  YANG model for FSM - Code

  module finite-state-machine {
    namespace "http://sssup.it/fsm";
    prefix fsm;

    import events {
      prefix ev;
    }

    organization
      "Scuola Superiore Sant'Anna Network and Services Laboratory";

    contact
      " Editor: Matteo Dallaglio
                <mailto:m.dallaglio@sssup.it>
      ";

    description
      "This module contains a YANG definitions of a generic finite state



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       machine.";

    revision 2016-03-15 {
      description "Initial Revision.";
      reference
        "RFC xxxx:";
    }

    // identity statements

    // typedef statements

    typedef state-id-type {
      type uint32;
    }


    // grouping statements
    grouping state-top {
      leaf id {
        type state-id-type;
      }

      leaf name {
        type string;
      }

      leaf description {
        type string;
      }


      grouping next-state-top {
        leaf next-state {
            type leafref {
              path "../../../../../../../../../states/state/id";
            }
            description "Id of the next state";
          }
      }

      uses ev:events-top {
        augment "events/event/reaction/operation/conditional/true" {
          uses next-state-top;
        }
        augment "events/event/reaction/operation/conditional/false" {
          uses next-state-top;
        }



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        augment "events/event/reaction/operation/simple" {
          //uses next-state-top;
          leaf next-state {
            type leafref {
              path "../../../../../../../../states/state/id";
            }
            description "Id of the next state";
          }
        }
      }

    }



    grouping states-top {
      leaf current-state {
        type leafref {
          path "../states/state/id";
        }
      }

      container states {
        list state {
          key "id";
          uses state-top;
        }
      }
    }


    // data definition statements



    uses states-top;

    // extension statements

    // feature statements

    // augment statements.

    // rpc statements

    // notification statements





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  }//module fsm


8.5.  Example of values for the YANG model


   FIELD NAME       |    YANG DATA TYPE   |        VALUE
   _________________|_____________________|________________________
   Current State    |       leafref       |  "an existing state id
                    |                     |       in the FSM"
                    |                     |
   State            |                     |
   id               |        uint32       |             1
   name             |        string       |          Steady
   description      |        string       |      "whatever string"
                    |                     |
   event            |                     |
   name             |        string       |      "whatever string"
   type             |         enum        |         BER_CHANGE
   description      |        string       |      "whatever string"
                    |                     |
   filter           |                     |
   filter-id        |        uint32       |             2
   filter-type      |   anyxml or xpath   |         BER>0.0009
                    |                     |
   reaction         |                     |
   id               |        uint32       |             3
   type             |         enum        |          SIMPLE
   statement        |        string       |      "whatever string"
   execute          |        anyxml       | "this recalls an RPC
                    |                     |   where the FEC value
                    |                     |    is expressed"
   next-operation   |        uint32       |           NULL
   next-state       |       leafref       | "an existing state id
                    |                     |       in the FSM"


9.  Acknowledgements

   This work has been partially supported by the European Commission
   through the H2020 ORCHESTRA (Optical peRformanCe monitoring enabling
   dynamic networks using a Holistic cross-layEr, Self-configurable
   Truly flexible approach, grant agreement no: H2020-645360) project.
   The views expressed here are those of the authors only.  The European
   Commission is not liable for any use that may be made of the
   information in this document.





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10.  Security Considerations

   TBD

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC7491]  King, D. and A. Farrel, "A PCE-Based Architecture for
              Application-Based Network Operations", RFC 7491,
              DOI 10.17487/RFC7491, March 2015,
              <http://www.rfc-editor.org/info/rfc7491>.

11.2.  Informative References

   [I-D.ietf-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A Data Model for Network
              Topologies", draft-ietf-i2rs-yang-network-topo-13 (work in
              progress), June 2017.

   [I-D.vergara-ccamp-flexigrid-yang]
              Madrid, U., Perdices, D., Lopezalvarez, V., Dios, O.,
              King, D., Lee, Y., and G. Galimberti, "YANG data model for
              Flexi-Grid Optical Networks", draft-vergara-ccamp-
              flexigrid-yang-04 (work in progress), March 2017.

   [I-D.zhang-ccamp-l1-topo-yang]
              zhenghaomian@huawei.com, z., Fan, Z., Sharma, A., and X.
              Liu, "A YANG Data Model for Optical Transport Network
              Topology", draft-zhang-ccamp-l1-topo-yang-07 (work in
              progress), April 2017.




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Authors' Addresses

   Nicola Sambo
   Scuola Superiore Sant'Anna
   Via Moruzzi 1
   Pisa  56124
   Italy

   Email: nicola.sambo@sssup.it


   Matteo Dallaglio
   Scuola Superiore Sant'Anna
   Via Moruzzi 1
   Pisa  56124
   Italy

   Email: matteo.dallaglio@sssup.it


   Piero Castoldi
   Scuola Superiore Sant'Anna
   Via Moruzzi 1
   Pisa  56124
   Italy

   Email: piero.castoldi@sssup.it


   Giuseppe Fioccola
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148
   Italy

   Email: giuseppe.fioccola@telecomitalia.it


   Andrea Di Giglio
   Telecom Italia
   Via Reiss Romoli, 274
   Torino  10148
   Italy

   Email: andrea.digiglio@telecomitalia.it






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   Filippo Cugini
   CNIT
   Via Moruzzi 1
   Pisa  56124
   Italy

   Email: filippo.cugini@cnit.it


   Giacomo Bernini
   Nextworks
   Via Livornese 1027
   Pisa  56122
   Italy

   Email: g.bernini@nextworks.it


   Pietro G. Giardina
   Nextworks
   Via Livornese 1027
   Pisa  56122
   Italy

   Email: p.giardina@nextworks.it


























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