module ietf-twamp-light {
   namespace "urn:ietf:params:xml:ns:yang:ietf-twamp-light";
    //namespace need to be assigned by IANA
   prefix "ietf-twamp-light";

   import ietf-inet-types {
     prefix inet;
   }
   import ietf-yang-types {
     prefix yang;
   }
   organization
     "IETF IPPM (IP Performance Metrics) Working Group";

   contact
     "draft-mirsky-ippm-twamp-light-yang@tools.ietf.org";

   description "TWAMP Light Data Model";

   revision "2016-06-17" {
     description "01 version. RFC5357 is covered,
     including Appendix I and the Errata";
     reference "draft-mirsky-ippm-twamp-light-yang";
   }

   feature session-sender-light {
     description "This feature relates to the device functions as the
     TWAMP Light Session-Sender";
   }

   feature session-reflector-light {
     description "This feature relates to the device functions as the
     TWAMP Light Session-Reflector";
   }

   typedef enable {
      type boolean;
      description "enable";
   }

   grouping maintenance-statistics {
     description "Maintenance statistics grouping";
     leaf sent-packets {
       type uint32;
       description "Packets sent";
     }
     leaf rcv-packets {
       type uint32;
       description "Packets received";
     }
     leaf sent-packets-error {
       type uint32;
       description "Packets sent error";
     }
     leaf rcv-packets-error {
       type uint32;
       description "Packets received error";
     }
     leaf last-sent-seq {
       type uint32;
       description "Last sent sequence number";
     }
     leaf last-rcv-seq {
       type uint32;
       description "Last received sequence number";
     }
   }

   grouping delay-statistics {
     description "delay statistics grouping";
     container delay {
       description "Packets transmitted delay";
                 leaf min {
                   type yang:gauge32;
                   units microseconds;
                   description "Min of Packets transmitted delay";
                 }
                 leaf max {
                    type yang:gauge32;
                    units microseconds;
                    description "Max of Packets transmitted delay";
                 }
                 leaf avg {
                    type yang:gauge32;
                    units microseconds;
                    description "Avg of Packets transmitted delay";
                 }
     }

         container delay-variation {
                 description "Packets transmitted delay variation";
                 leaf min {
                   type uint32;
                   units microseconds;
                   description "Min of Packets
                   transmitted delay variation";
                 }
                 leaf max {
                   type uint32;
                   units microseconds;
                   description "Max of Packets
                   transmitted delay variation";
                 }
                 leaf avg {
                   type uint32;
                   units microseconds;
                   description "Avg of Packets
                   transmitted delay variation";
                 }
          }
   }

   grouping session-light-parameters {
     description "Parameters common among
     Session-Sender and Session-Reflector";
     leaf sender-ip {
       type inet:ip-address;
       mandatory true;
       description "Sender IP address";
     }
     leaf sender-udp-port {
       type inet:port-number {
         range "49152..65535";
       }
       mandatory true;
       description "Sender UDP port number";
     }
     leaf reflector-ip {
       type inet:ip-address;
       mandatory true;
       description "Reflector IP address";
     }
     leaf reflector-udp-port {
       type inet:port-number{
         range "49152..65535";
       }
       mandatory true;
       description "Reflector UDP port number";
     }
     leaf dscp {
       type inet:dscp;
       default "0";
       description "The DSCP value to be placed in the header of
       TWAMP UDP test packets generated by the Session-Sender.
       Whether Session-Reflector uses this value depends upon its
       local configuration";
     }
   }

   /*Configuration Data*/
   container twamp-light {
     description "Top level container for TWAMP-Light configuration";

    container twamp-light-session-sender {
       if-feature session-sender-light;
       description "TWAMP-Light Session-Sender container";

       leaf sender-light-enable {
         type enable;
         default "true";
         description "Whether this network element is enabled to
         act as TWAMP-Light Sender";
       }

       list test-session {
         key "session-id";
               unique "sender-ip sender-udp-port reflector-ip"
         +" reflector-udp-port dscp";
         description "This structure is a container of test session
         managed objects";

         leaf session-id {
           type uint32;
           description "Session ID";
         }

         leaf test-session-enable {
           type enable;
           default "true";
           description "Whether this TWAMP Test session is enabled";
         }

         leaf number-of-packets {
           type uint32;
           description "The overall number of UDP test packets to be
             transmitted by the sender for this test session";
         }

         leaf packet-padding-size {
           type uint32;
           default 27;
           description "Size of the Packet Padding. Suggested to run
           Path MTU Discovery to avoid packet fragmentation in IPv4
           and packet blackholing in IPv6";
         }

          leaf session-authentication-mode {
            type enumeration {
              enum unauthenticated {
                description "Unauthenticated TWAMP-Light
                   test session";
              }
              enum authenticated {
                description "Authenticated TWAMP-Light test session";
              }
              enum encrypted {
                description "Encrypted TWAMP-Light test session";
              }
            }
            default unauthenticated;
            description "Authentication mode of the TWAMP-Light test
            session";
          }

         leaf interval  {
           type uint32;
           description "Time interval between transmission of two

           consecutive packets in the test session";
         }

         uses session-light-parameters;
       }
     }

     container twamp-light-session-reflector {
       if-feature session-reflector-light;
       description "TWAMP-Light Session-Reflector container";
         leaf reflector-light-enable {
           type enable;
           default "true";
           description "Whether this network element is enabled to
           act as TWAMP-Light Reflector";
         }

         leaf ref-wait {
         type uint32 {
           range 1..604800;
         }
         units seconds;
         default 900;
         description "REFWAIT(TWAMP test session timeout in seconds),
         the default value is 900";
       }

       leaf reflector-light-mode-state {
         type enumeration {
           enum stateful {
             description "When the Session-Reflector Light is
             stateful, i.e. is aware of test session state";
           }
           enum stateless {
             description "When the Session-Reflector is stateless
             and uses sequence number of the received TWAMP-Test
             packet as its own";
           }
         }
         default stateless;
         description "The state of the mode of the TWAMP-Light
         Session-Reflector";
        }

        leaf dscp-handling-mode {
          type enumeration {
            enum copy-received-value {
              description "Use DSCP value copied from received TWAMP
              test packet of the test session";
              }
              enum use-configured-value {
                description "Use DSCP value configured for this test
                session on the Session-Reflector";
                }
             }
             default copy-received-value;
             description "Session-Reflector handling of DSCP:
                 - use value copied from received TWAMP-Test packet;
                 - use value explicitly configured";
        }
        list test-session {
          key "session-id";
                unique "sender-ip sender-udp-port reflector-ip"
          +" reflector-udp-port dscp";
          description "This structure is a container of test session
          managed objects";

        leaf session-id {
          type uint32;
          description "Session ID";
        }

        uses session-light-parameters;
       }
     }
   }

 /*Operational state data nodes*/
 container twamp-light-state{
   config "false";
   description "Top level container for TWAMP-Light state data";

   container twamp-light-session-sender-state {
     if-feature session-sender-light;
     description "Session-Sender container for state data";
     list test-session-state{
       key "session-id";
       description "This structure is a container of test session
       managed objects";

       leaf session-id {
         type uint32;
         description "Session ID";
       }

       leaf sender-session-state {
         type enumeration {
           enum active {
             description "Test session is active";
           }
           enum ready {
             description "Test session is idle";
           }
         }
         description "State of the particular TWAMP-Light test
         session at the sender";
       }

       container current-stats {
         description
         "This container contains the results for the current
          Measurement Interval in a Measurement session ";
          leaf start-time {
            type yang:date-and-time;
            mandatory true;
            description
            "The time that the current Measurement Interval started";
          }
          leaf number-of-packets {
            type uint32;
            description "The overall number of UDP test packets to be
            transmitted by the sender for this test session";
          }

          leaf packet-padding-size {
            type uint32;
            default 27;
            description "Size of the Packet Padding. Suggested to run
            Path MTU Discovery  to avoid packet fragmentation in IPv4
            and packet backholing in IPv6";
          }

          leaf interval  {
            type uint32;
           description "Time interval between transmission of two
           consecutive packets in the test session";
          }

          leaf duplicate-packets  {
            type uint32;
           description "Duplicate packets";
          }
          leaf reordered-packets  {
            type uint32;
           description "Reordered packets";
          }
          leaf loss-packets  {
            type uint32;
           description "Loss packets";
          }
          uses session-light-parameters;
          uses maintenance-statistics;

          container two-way-delay{
            description "two way delay result of the test session";
            uses delay-statistics;
          }
          container one-way-delay-far-end{
            description "one way delay far end of the test session";
            uses delay-statistics;
          }
          container one-way-delay-near-end{
            description "one way delay near end of the test session";
            uses delay-statistics;
          }
       }

       list history-stats {
         key id;
         description
         "This container contains the results for the history
          Measurement Interval in a Measurement session ";
          leaf id {
            type uint32;
            description
            "The identifier for the Measurement Interval within this
             session";
          }
          leaf end-time {
            type yang:date-and-time;
            mandatory true;
            description
            "The time that the Measurement Interval ended";
          }
          leaf number-of-packets {
            type uint32;
            description "The overall number of UDP test packets to be
            transmitted by the sender for this test session";
          }

          leaf packet-padding-size {
            type uint32;
            default 27;
            description "Size of the Packet Padding. Suggested to run
            Path MTU Discovery  to avoid packet fragmentation in IPv4
            and packet blackholing in IPv6";
          }

          leaf interval  {
            type uint32;
           description "Time interval between transmission of two
           consecutive packets in the test session";
          }
          leaf duplicate-packets  {
            type uint32;
           description "Duplicate packets";
          }
          leaf reordered-packets  {
            type uint32;
           description "Reordered packets";
          }
          leaf loss-packets  {
            type uint32;
           description "Loss packets";
          }

          uses session-light-parameters;
          uses maintenance-statistics;

          container two-way-delay{
            description "two way delay result of the test session";
            uses delay-statistics;
          }
          container one-way-delay-far-end{
            description "one way delay far end of the test session";
            uses delay-statistics;
          }
          container one-way-delay-near-end{
            description "one way delay near end of the test session";
            uses delay-statistics;
          }
       }
     }
   }

   container twamp-light-session-reflector-state {
     if-feature session-reflector-light;
     description "TWAMP-Light Session-Reflector container for
     state data";
     leaf reflector-light-admin-status {
       type boolean;
       mandatory "true";
       description "Whether this network element is enabled to
       act as TWAMP-Light Reflector";
     }

     list test-session-state {
       key "session-id";
       description "This structure is a container of test session
       managed objects";

       leaf session-id {
         type uint32;
         description "Session ID";
       }

       uses maintenance-statistics;
       uses session-light-parameters;

       container one-way-delay {
         description "one way delay of the test session";
         uses delay-statistics;
       }
     }
   }
 }

 rpc twamp-sender-start {
   description
         "start the configured sender session";
   input {
         leaf session-id {
           type uint32;
           mandatory true;
           description
                 "The session to be started";
         }
   }
 }

 rpc twamp-sender-stop {
   description
         "stop the configured sender session";
   input {
         leaf session-id {
           type uint32;
           mandatory true;
           description
                 "The session to be stopped";
         }
   }
 }
}