+-----------------------+
| twampSessionReflector |
+-----------------------+   0..* +------------------------------------+
| refwait               |<>------| twampReflectorTestSession          |
+-----------------------+        +------------------------------------+
                                 | sid                           {ro} |
                                 | senderIp                      {ro} |
                                 | senderUdpPort                 {ro} |
                                 | reflectorIp                   {ro} |
                                 | reflectorUdpPort              {ro} |
                                 | parentConnectionClientIp      {ro} |
                                 | parentConnectionClientTcpPort {ro} |
                                 | parentConnectionServerIp      {ro} |
                                 | parentConnectionServerTcpPort {ro} |
                                 | dscp                          {ro} |
                                 | sentPackets                   {ro} |
                                 | rcvPackets                    {ro} |
                                 | lastSentSeq                   {ro} |
                                 | lastRcvSeq                    {ro} |
                                 +------------------------------------+

Figure 6: TWAMP Session-Reflector UML class diagram

The twampSessionReflector configuration items are:

refwait

The Session-Reflector MAY discontinue any session that has been started when no packet associated with that session has been received for REFWAIT seconds. The default value of REFWAIT SHALL be 900 seconds, and this waiting time MAY be configurable. This timeout allows a Session-Reflector to free up resources in case of failure.

Instances of twampSessionReflector:twampReflectorTestSession are indexed by a session identifier (SID). This is a value that is auto-allocated by the Server as test session requests are received, and communicated back to the Control-Client in the SID field of the Accept-Session message; see Section 4.3 of [RFC6038].

When attempting to retrieve operational data for active test sessions from a Session-Reflector device, the user will not know what sessions are currently active on that device, or what SIDs have been auto-allocated for these test sessions. If the user has network access to the Control-Client device, then it is possible to read the data for this session under twampClient:twampClientCtrlConnection:twampSessionRequest and obtain the SID (see Figure 3). The user may then use this SID value as an index to retrieve an individual twampSessionReflector:twampReflectorTestSession instance on the Session-Reflector device.

If the user has no network access to the Control-Client device, then the only option is to retrieve all twampReflectorTestSession instances from the Session-Reflector device. This could be problematic if a large number of test sessions are currently active on that device.

Each Session-Reflector test session contains the following 4-tuple: {parentConnectionClientIp, parentConnectionClientTcpPort, parentConnectionServerIp, parentConnectionServerTcpPort}. This 4-tuple corresponds to the equivalent 4-tuple {clientIp, clientTcpPort, serverIp, serverTcpPort} in the twampServerCtrlConnection object. This four4-tuple allows the user to trace back from the test session to the parent control connection that negotiated this test session.

All data under twampReflectorTestSession is read-only:

sid

An auto-allocated identifier for this test session, that is unique within the context of this Server/Session-Reflector device only. This value will be communicated to the Control-Client that requested the test session in the SID field of the Accept-Session message.

senderIp

The IP address on the remote device, which is the source IP address used in the TWAMP UDP test packets belonging to this test session.

senderUdpPort

The source UDP port used in the TWAMP UDP test packets belonging to this test session.

reflectorIp

The IP address of the local Session-Reflector device, which is the destination IP address used in the TWAMP UDP test packets belonging to this test session.

reflectorUdpPort

The destination UDP port used in the TWAMP UDP test packets belonging to this test session.

parentConnectionClientIp

The IP address on the Control-Client device, which is the source IP address used in the TWAMP TCP control packets belonging to the parent control connection that negotiated this test session.

parentConnectionClientTcpPort

The source TCP port used in the TWAMP TCP control packets belonging to the parent control connection that negotiated this test session.

parentConnectionServerIp

The IP address of the Server device, which is the destination IP address used in the TWAMP TCP control packets belonging to the parent control connection that negotiated this test session.

parentConnectionServerTcpPort

The destination TCP port used in the TWAMP TCP control packets belonging to the parent control connection that negotiated this test session.

dscp

The DSCP value present in the UDP header of TWAMP test packets belonging to this test session.

sentPackets

The number of UDP test response packets that have been sent by the Session-Reflector for this test session.

rcvPackets

The number of UDP test packets that have been received by the Session-Reflector for this test session. Since the Session-Reflector should respond to every test packet it receives, the sentPackets and rcvPackets values should always be identical.

lastSentSeq

The value in the sequence number field of the last UDP test response packet transmitted for this test session.

lastRcvSeq

The value in the sequence number field of the last UDP test packet received for this test session.

5. Data Model

5.1. Tree Diagram

This section presents the TWAMP YANG data tree defined in this document. Readers should keep in mind that the limit of 72 characters per line forces us to introduce artificial line breaks in some tree nodes.

module: twamp
   +--rw twamp
      +--rw twampClient {controlClient}?
      |  +--rw clientAdminState             boolean
      |  +--rw modePreferenceChain* [priority]
      |  |  +--rw priority    uint16
      |  |  +--rw mode?       enumeration
      |  +--rw keyChain* [keyId]
      |  |  +--rw keyId        string
      |  |  +--rw secretKey?   string
      |  +--rw twampClientCtrlConnection* [ctrlConnectionName]
      |     +--rw ctrlConnectionName     string
      |     +--rw clientIp?              inet:ip-address
      |     +--rw serverIp?              inet:ip-address
      |     +--rw serverTcpPort?         inet:port-number
      |     +--rw dscp?                  inet:dscp
      |     +--rw keyId?                 string
      |     +--rw dkLen?                 uint32
      |     +--ro clientTcpPort?         inet:port-number
      |     +--ro serverStartTime?       uint64
      |     +--ro ctrlConnectionState?   enumeration
      |     +--ro selectedMode?          enumeration
      |     +--ro token?                 string
      |     +--ro clientIv?              string
      |     +--rw twampSessionRequest* [testSessionName]
      |        +--rw testSessionName     string
      |        +--rw senderIp?           inet:ip-address
      |        +--rw senderUdpPort?      inet:port-number
      |        +--rw reflectorIp?        inet:ip-address
      |        +--rw reflectorUdpPort?   inet:port-number
      |        +--rw timeout?            uint64
      |        +--rw paddingLength?      uint32
      |        +--rw startTime?          uint64
      |        +--rw repeat?             boolean
      |        +--rw repeatInterval?     uint32
      |        +--rw pmIndex?            uint16
      |        +--ro testSessionState?   enumeration
      |        +--ro sid?                string
      +--rw twampServer {server}?
      |  +--rw serverAdminState             boolean
      |  +--rw serverTcpPort?               inet:port-number
      |  +--rw servwait?                    uint32
      |  +--rw dscp?                        inet:dscp
      |  +--rw count?                       uint32
      |  +--rw maxCount?                    uint32
      |  +--rw modes?                       bits
      |  +--ro salt?                        string
      |  +--ro serverIv?                    string
      |  +--ro challenge?                   string
      |  +--rw keyChain* [keyId]
      |  |  +--rw keyId        string
      |  |  +--rw secretKey?   string
      |  +--ro twampServerCtrlConnection* \
                      [clientIp clientTcpPort serverIp serverTcpPort]
      |     +--ro clientIp                     inet:ip-address
      |     +--ro clientTcpPort                inet:port-number
      |     +--ro serverIp                     inet:ip-address
      |     +--ro serverTcpPort                inet:port-number
      |     +--ro serverCtrlConnectionState?   enumeration
      |     +--ro dscp?                        inet:dscp
      |     +--ro selectedMode?                enumeration
      |     +--ro keyId?                       string
      |     +--ro dkLen?                       uint32
      |     +--ro count?                       uint32
      |     +--ro maxCount?                    uint32
      +--rw twampSessionSender {sessionSender}?
      |  +--rw twampSenderTestSession* [testSessionName]
      |     +--rw testSessionName         string
      |     +--ro ctrlConnectionName?     string
      |     +--rw dscp?                   inet:dscp
      |     +--rw dot1dPriority?          uint8
      |     +--rw fillMode?               enumeration
      |     +--rw numberOfPackets?        uint32
      |     +--rw (packetDistribution)?
      |     |  +--:(fixed)
      |     |  |  +--rw fixedInterval?          uint32
      |     |  |  +--rw fixedIntervalUnits?     enumeration
      |     |  +--:(poisson)
      |     |     +--rw lambda?                 uint32
      |     |     +--rw lambdaUnits?            uint32
      |     |     +--rw maxInterval?            uint32
      |     |     +--rw truncationPointUnits?   enumeration
      |     +--ro senderSessionState?     enumeration
      |     +--ro sentPackets?            uint32
      |     +--ro rcvPackets?             uint32
      |     +--ro lastSentSeq?            uint32
      |     +--ro lastRcvSeq?             uint32
      +--rw twampSessionReflector {sessionReflector}?
         +--rw refwait?                     uint32
         +--ro twampReflectorTestSession* \
                [senderIp senderUdpPort reflectorIp reflectorUdpPort]
            +--ro sid?                             string
            +--ro senderIp                         inet:ip-address
            +--ro senderUdpPort                    inet:port-number
            +--ro reflectorIp                      inet:ip-address
            +--ro reflectorUdpPort                 inet:port-number
            +--ro parentConnectionClientIp?        inet:ip-address
            +--ro parentConnectionClientTcpPort?   inet:port-number
            +--ro parentConnectionServerIp?        inet:ip-address
            +--ro parentConnectionServerTcpPort?   inet:port-number
            +--ro dscp?                            inet:dscp
            +--ro sentPackets?                     uint32
            +--ro rcvPackets?                      uint32
            +--ro lastSentSeq?                     uint32
            +--ro lastRcvSeq?                      uint32
	  

5.2. YANG Module

This section presents the TWAMP YANG module defined in this document.

<CODE BEGINS> file "ietf-twamp@2015-03-06.yang"
module twamp {
  namespace "urn:ietf:params:xml:ns:yang:ietf-twamp";
   //namespace need to be assigned by IANA
  prefix "twamp";
  
  import ietf-inet-types {
    prefix inet;
  }
  
  organization
    "IETF IPPM (IP Performance Metrics) Working Group";
        
  contact
    "draft-cmzrjp-ippm-twamp-yang@tools.ietf.org";

  description "TWAMP Data Model";
  
  revision "2015-03-06" {
    description "Initial version. RFC5357 is covered.
      RFC5618, RFC5938 and RFC6038 are not covered.";
  }
  
  feature controlClient {
    description "This feature relates to the device functions as the
      TWAMP Control-Client.";
  }

  feature server {
    description "This feature relates to the device functions as the
      TWAMP Server.";
  }
  
  feature sessionSender {
    description "This feature relates to the device functions as the
      TWAMP Session-Sender.";
  }
  
  feature sessionReflector {
    description "This feature relates to the device functions as the
      TWAMP Session-Reflector.";
  }
  
  grouping maintenanceStatistics {
    leaf sentPackets {
      config "false";
      type uint32;
    }
    leaf rcvPackets {
      config "false";
      type uint32;
    }
    leaf lastSentSeq {
      config "false";
      type uint32;
    }
    leaf lastRcvSeq {
      config "false";
      type uint32;
    }
  }

  container twamp {
    container twampClient {
      if-feature controlClient;
      leaf clientAdminState {
        mandatory "true";
        type boolean;
        description "Indicates whether this device is allowed to run
          TWAMP to initiate control/test sessions";
      }
      
      list modePreferenceChain {
        key "priority";
        unique "mode";
          
        leaf priority {
          type uint16;
        }
        leaf mode {
          type enumeration {
            enum unauthenticated {
              value "1";
            }
            enum authenticated {
              value "2";
              }
            enum encrypted {
              value "4";
            }
            enum unauthtestencrpytcontrol {
              value "8";
            }
            enum individualsessioncontrol {
              value "16";
              }
            enum reflectoctets {
              value "32";
            }
            enum symmetricalsize {
              value "64";
            }
          }
        }
      }
      
      list keyChain {
        key "keyId";
        leaf keyId {
          type string {
            length "1..80";
          }
        }
        leaf secretKey {
          type string;
        }
      }

      list twampClientCtrlConnection {
        key "ctrlConnectionName";
        leaf ctrlConnectionName {
          type "string";
          description "A unique name used as a key to identify this
            individual TWAMP control connection on the
            Control-Client device.";
        }
        leaf clientIp {
          type inet:ip-address;
        }
        leaf serverIp {
          config "true";
          type inet:ip-address;
        }
        leaf serverTcpPort {
          type inet:port-number;
        }
        leaf dscp{
          type inet:dscp; 
          description "The DSCP value to be placed in the IP header
            of the TWAMP TCP Control packets generated
            by the Control-Client";
        }
        leaf keyId {
          type string {
            length "1..80";
          }
        }
        leaf dkLen {
          type uint32;
        }
        leaf clientTcpPort {
          config "false";
          type inet:port-number;
        }
        leaf serverStartTime {
          config "false";
          type uint64;
        }
        leaf ctrlConnectionState {
          config "false";
          type enumeration {
            enum active {
              description "Control session is active.";
            }
            enum idle {
              description "Control session is idle.";
            }
          }
        }
        leaf selectedMode {
          config "false";
          type enumeration {
            enum unauthenticated {
              value "1";
            }
            enum authenticated {
              value "2";
              }
            enum encrypted {
              value "4";
            }
            enum unauthtestencrpytcontrol {
              value "8";
            }
            enum individualsessioncontrol {
              value "16";
              }
            enum reflectoctets {
              value "32";
            }
            enum symmetricalsize {
              value "64";
            }
          }
        }
        leaf token {
          config "false";
          type string {
            length "1..64";
          }
          description "64 octets, containing the concatenation of a 
            16-octet challenge, a 16-octet AES Session-key used
            for encryption, and a 32-octet HMAC-SHA1 Session-key
            used for authentication";
        }
        leaf clientIv{
          config "false";
          type string {
            length "1..16";
          }
          description "16 octets, Client-IV is generated randomly 
            by the Control-Client.";
        }
        
        list twampSessionRequest {
          key "testSessionName";  
          leaf testSessionName {
            type "string";
          }
          leaf senderIp {
            type inet:ip-address;
          }
          leaf senderUdpPort {
            type inet:port-number;
          }
          leaf reflectorIp {
            type inet:ip-address;
          }
          leaf reflectorUdpPort {
            type inet:port-number;
          }
          leaf timeout {
            type uint64;
            description "The time Session-Reflector MUST wait after
                receiving a Stop-Session message";
          }
          leaf paddingLength {
            type uint32{
              range "64..1500";
            }
            description "The number of bytes of padding that should
                be added to the UDP test packets generated by the
                sender.";
          }
          leaf startTime {
            type uint64;
          }
          leaf repeat  {
            type boolean;
          }
          leaf repeatInterval  {
            type uint32;
            when "repeat='true'";
            description "Repeat interval (in minutes)";
          }
          leaf pmIndex {
            type uint16;
            description "Numerical index value of a Registered
                Metric in the Performance Metric Registry";
          }
          leaf testSessionState {
            config "false";
            type enumeration {
              enum ok {
                value 0;
                description "Test session is accepted.";
              }
              enum failed {
                value 1;
                description "Failure, reason unspecified
                    (catch-all).";
              }
              enum internalError {
                value 2;
                description "Internal error.";
              }
              enum notSupported {
                value 3;
                description "Some aspect of request is not
                    supported.";
              }
              enum permanentResLimit {
                value 4;
                description "Cannot perform request due to
                    permanent resource limitations.";
              }
              enum tempResLimit {
                value 5;
                description "Cannot perform request due to
                    temporary resource limitations.";
              }
            }
          }
          leaf sid{
            config "false";
            type string;
          }
        }
      }
    }

    container twampServer{
      if-feature server;
      leaf serverAdminState{
        type boolean;
        mandatory "true";
        description "Indicates whether this device is allowed to run 
          TWAMP to respond to control/test sessions";
      }
      leaf serverTcpPort {
        type inet:port-number;
        default "862";
      }
      leaf servwait {
        type uint32 {
          range 1..604800;
        }
        default 900;
        description "SERVWAIT (TWAMP Control (TCP) session timeout), 
          default value is 900";
      }
      leaf dscp {
        type inet:dscp; 
        description "The DSCP value to be placed in the IP header
          of the TWAMP TCP Control packets generated by the Server";
      }
      leaf count {
        type uint32 {
          range 1024..4294967295;
        }
      }
      leaf maxCount {
        type uint32 {
          range 1024..4294967295;
        }
        default 32768;
      }
      leaf modes {
        type bits {
          bit unauthenticated {
            position 0;
          }
          bit authenticated {
            position 1;
          }
          bit encrypted {
            position 2;
          }
          bit unauthtestencryptcontrol {
            position 3;
          }
          bit individualsessioncontrol {
            position 4;
          }
          bit reflectoctets {
            position 5;
          }
          bit symmetricalsize {
            position 6;
          }
        }
      }
      leaf salt{
        config "false";
        type string {
          length "1..16";
        }
          description "Salt MUST be generated pseudo-randomly";
      }   
      leaf serverIv {
        config "false";
        type string {
          length "1..16";
        }
        description "16 octets, Server-IV is generated randomly
          by the Control-Client.";
      }
      leaf challenge {
        config "false";
        type string {
          length "1..16";
        }
        description "Challenge is a random sequence of octets
          generated by the Server";
      }   
      
      list keyChain {
        key "keyId";
        leaf keyId {
          type string {
            length "1..80";
          }
        }
        leaf secretKey {
          type string;
        }
      }
  
      list twampServerCtrlConnection {
        key "clientIp clientTcpPort serverIp serverTcpPort";
        config "false";
        leaf clientIp {
          type inet:ip-address;
        }
        leaf clientTcpPort {
          type inet:port-number;
        }
        leaf serverIp {
          type inet:ip-address;
        }
        leaf serverTcpPort {
          type inet:port-number;
        }     
        leaf serverCtrlConnectionState {
          type enumeration {
            enum "active";
            enum "servwait";
          }
        }
        leaf dscp {
          type inet:dscp; 
          description "The DSCP value used in the header of the TCP
            control packets sent by the Server for this control
            connection. This will usually be the same value as is
            configured for twampServer:dscp under the twampServer.
            However, in the event that the user re-configures
            twampServer:dscp after this control connection is already
            in progress, this read-only value will show the actual
            dscp value in use by this control connection.";
        }
        leaf selectedMode {
          type enumeration {
            enum unauthenticated {
              value "1";
            }
            enum authenticated {
              value "2";
              }
            enum encrypted {
              value "4";
            }
            enum unauthtestencrpytcontrol {
              value "8";
            }
            enum individualsessioncontrol {
              value "16";
              }
            enum reflectoctets {
              value "32";
            }
            enum symmetricalsize {
              value "64";
            }
          }
          description "The mode that was chosen for this control
            connection as set in the Mode field of the Set-Up-Response
            message.";
        }
        leaf keyId {
          type string {
            length "1..80";
          }
          description "The keyId value that is in use by this control
            connection.";         
        }
        leaf dkLen {
          type uint32;
          description "The dkLen value that is in use by this control
            connection. This will usually be the same value as is
            configured under twampServer. In the event that the user
            re-configured twampServer:dkLen after this control
            connection is already in progress, this read-only value
            will show the actual dkLen that is in use for this
            control connection.";
        }
        leaf count {
          type uint32 {
            range 1024..4294967295;
          }
          description "The count value that is in use by this control
            connection. This will usually be the same value as is
            configured under twampServer. However, in the event that
            the user re-configured twampServer:count after this control
            connection is already in progress, this read-only value
            will show the actual count that is in use for this
            control connection.";    
        }
        leaf maxCount {
          type uint32 {
            range 1024..4294967295;
          }
          description "The maxCount value that is in use by this
            control connection. This will usually be the same value
            as is configured under twampServer. However, in the event
            that the user re-configured twampServer:maxCount after
            this control connection is already in progress, this
            read-only value will show the actual maxCount that is
            in use for this control connection.";   
        }   
      }
    }
  
    container twampSessionSender {
      if-feature sessionSender;
      list twampSenderTestSession {
        key "testSessionName";
        leaf testSessionName {
          type string;
          description "A unique name for this test session to be used
            as a key for this test session by the Session-Sender
            logical entity.";
        }
        leaf ctrlConnectionName {
          config "false";
            type "string";
            description "The name of the parent control connection
              that is responsible for negotiating this test session.";
        }
        leaf dscp {
          type inet:dscp;
          description "The DSCP value to be placed in the header of
            TWAMP UDP test packets generated by the sender."; 
        }
        leaf dot1dPriority {
          type uint8 {
            range "0..7";
          }
        }
        leaf fillMode {
          type enumeration {
            enum zero;
            enum random;
          }
          default zero;
        }
        leaf numberOfPackets {
          type uint32;
          description "The overall number of UDP test packets to be
            transmitted by the sender for this test session.";
        }
        choice packetDistribution {
          case fixed {
            leaf fixedInterval {
              type uint32;
            }
            leaf fixedIntervalUnits  {
              type enumeration {
                enum seconds;
                enum milliseconds;
                enum microseconds;
                enum nanoseconds;
              }
            }
          }
          case poisson {
            leaf lambda {
              type uint32;
            }  
            leaf lambdaUnits {
              type uint32;
            }  
            leaf maxInterval {
              type uint32;
            }
            leaf truncationPointUnits {
              type enumeration {
                enum seconds;
                enum milliseconds;
                enum microseconds;
                enum nanoseconds;
              }
            }
          }
        }
        leaf senderSessionState {
          config "false";
          type enumeration {
            enum setup {
              description "Test session is active.";
            }
            enum failure {
              description "Test session is idle.";
            }
          }
        }
        uses maintenanceStatistics;
      }
    }
    
    container twampSessionReflector {
      if-feature sessionReflector;
      leaf refwait {
        config "true";
        type uint32 {
          range 1..604800;
        }
        default 900;
        description "REFWAIT(TWAMP test session timeout),
          the default value is 900";
      }
  
      list twampReflectorTestSession {
        key "senderIp senderUdpPort reflectorIp reflectorUdpPort";
        config "false";
        leaf sid {
          type string;
        }
        leaf senderIp {
          type inet:ip-address;
        }
        leaf senderUdpPort {
          type inet:port-number;
        }
        leaf reflectorIp {
          type inet:ip-address;
        }
        leaf reflectorUdpPort {
          type inet:port-number;
        }
        leaf parentConnectionClientIp {
          type inet:ip-address;
        }
        leaf parentConnectionClientTcpPort {
          type inet:port-number;
        }
        leaf parentConnectionServerIp {
          type inet:ip-address;
        }
        leaf parentConnectionServerTcpPort {
          type inet:port-number;
        }
        leaf dscp {
          type inet:dscp;
          description "The DSCP value placed in the header of TWAMP
            UDP test packets generated by the Session-Sender.";
        }
        uses maintenanceStatistics;
      }
    }
  }
}
<CODE ENDS>
       

6. Data Model Examples

This section presents a simple but complete example of configuring all four entities in Figure 1, based on the YANG module specified in Section 5. The example is illustrative in nature, but aims to be self-contained, i.e. were it to be executed in a real TWAMP implementation it would lead to a correctly configured test session. A more elaborated example, which also includes authentication parameters, is provided in Appendix A.

6.1. Control-Client

The following configuration example shows a Control-Client with clientAdminState enabled. In a real implementation this would permit the Control-Client functional entity to initiate TWAMP control connections and test sessions.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampClient>
      <clientAdminState>True</clientAdminState>
   </twampClient>
</twamp>

The following configuration example shows a Control-Client with two instances of twampClientCtrlConnection, one called "RouterA" and another called "RouterB". Each control connection is to a different Server. The control connection named "RouterA" has two test session requests. The control connection with name "RouterB" has no test session requests.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampClient>
   
      <twampClientCtrlConnection>
         <ctrlConnectionName>RouterA</ctrlConnectionName>
         <clientIp>203.0.113.1</clientIp>
         <serverIp>203.0.113.2</serverIp>
         <twampSessionRequest>
            <testSessionName>Test1</testSessionName>
            <senderIp>10.1.1.1</senderIp>
            <senderUdpPort>4000</senderUdpPort>
            <reflectorIp>10.1.1.2</reflectorIp>
            <reflectorUdpPort>5000</reflectorUdpPort>
            <startTime>0</startTime>
         </twampSessionRequest>
         <twampSessionRequest>
            <testSessionName>Test2</testSessionName>
            <senderIp>203.0.113.1</senderIp>
            <senderUdpPort>4001</senderUdpPort>
            <reflectorIp>203.0.113.2</reflectorIp>
            <reflectorUdpPort>5001</reflectorUdpPort>
            <startTime>0</startTime>
         </twampSessionRequest>
      </twampClientCtrlConnection>
	  
      <twampClientCtrlConnection>
         <ctrlConnectionName>RouterB</ctrlConnectionName>
         <clientIp>203.0.113.1</clientIp>
         <serverIp>203.0.113.3</serverIp>
      </twampClientCtrlConnection>
	  
   </twampClient>
</twamp>

6.2. Server

This configuration example shows a Server with serverAdminState enabled, which permits the device to respond to TWAMP control connections and test sessions.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampServer>
      <serverAdminState>True</serverAdminState>
   </twampServer>
</twamp>

The following example presents a Server with the control connection corresponding to the control connection name (ctrlConnectionName) "RouterA" presented in Section 6.1.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampServer>
   
      <twampServerCtrlConnection>
         <clientIp>203.0.113.1</clientIp>
         <clientTcpPort>16341</clientTcpPort>
         <serverIp>203.0.113.2</serverIp>
         <serverTcpPort>862</serverTcpPort>
         <serverCtrlConnectionState>active</serverCtrlConnectionState>
      </twampServerCtrlConnection>
   
   </twampServer>
</twamp>

6.3. Session-Sender

The following configuration example shows a Session-Sender with the two test sessions presented earlier in Section 6.1.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampSessionSender>
   
      <twampSenderTestSession>
         <testSessionName>Test1</testSessionName>
         <ctrlConnectionName>RouterA</ctrlConnectionName>  // read-only
         <numberOfPackets>900</numberOfPackets>
         <packetDistribution>
            <fixedInterval>1</fixedInterval>
            <fixedIntervalUnits>seconds</fixedIntervalUnits>
         </packetDistribution>
      </twampSenderTestSession>
	  
      <twampSenderTestSession>
         <testSessionName>Test2</testSessionName>
         <ctrlConnectionName>RouterA</ctrlConnectionName>  // read-only
         <numberOfPackets>900</numberOfPackets>
         <packetDistribution>
            <lambda>1</lambda>
            <lambdaUnits>1</lambdaUnits>
            <maxInterval>2</maxInterval>
            <truncationPointunits>seconds</truncationPointunits>
      	</packetDistribution>
      </twampSenderTestSession>
	  
   </twampSessionSender>
</twamp>

6.4. Session-Reflector

The following example shows the two Session-Reflector test sessions corresponding to the test sessions presented in Section 6.3.

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampSessionReflector>
   
       <twampReflectorTestSession>
         <sid>1232</sid>
         <senderIp>10.1.1.1</senderIp>
         <reflectorIp>10.1.1.2</reflectorIp>
         <senderUdpPort>4000</senderUdpPort>
         <reflectorUdpPort>5000</reflectorUdpPort>
         <parentConnectionClientIp>
		   203.0.113.1
		 </parentConnectionClientIp>
         <parentConnectionClientTcpPort>
		   16341
		 </parentConnectionClientTcpPort>
         <parentConnectionServerIp>
		   203.0.113.2
		 </parentConnectionServerIp>
         <parentConnectionServerTcpPort>
		   862
		 </parentConnectionServerTcpPort>
         <sentPackets>2</sentPackets>
         <rcvPackets>2</rcvPackets>
         <lastSentSeq>1</lastSentSeq>
         <lastRcvSeq>1</lastRcvSeq>
      </twampReflectorTestSession>
	  
      <twampReflectorTestSession>
         <sid>178943</sid>
         <senderIp>203.0.113.1</senderIp>
         <reflectorIp>192.68.0.2</reflectorIp>
         <senderUdpPort>4001</senderUdpPort>
         <parentConnectionClientIp>
		   203.0.113.1
		 </parentConnectionClientIp>
         <parentConnectionClientTcpPort>
		   16341
		 </parentConnectionClientTcpPort>
         <parentConnectionServerIp>
		   203.0.113.2
		 </parentConnectionServerIp>
         <parentConnectionServerTcpPort>
		   862
		 </parentConnectionServerTcpPort>
         <reflectorUdpPort>5001</reflectorUdpPort>
         <sentPackets>21</sentPackets>
         <rcvPackets>21</rcvPackets>
         <lastSentSeq>20</lastSentSeq>
         <lastRcvSeq>20</lastRcvSeq>
      </twampReflectorTestSession>
	  
   </twampSessionReflector>
</twamp>

7. Security Considerations

TBD

8. IANA Considerations

This document registers a URI in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registration is requested to be made.

URI: urn:ietf:params:xml:ns:yang:ietf-twamp

Registrant Contact: The IPPM WG of the IETF.

XML: N/A, the requested URI is an XML namespace.

This document registers a YANG module in the YANG Module Names registry [RFC6020].

name: ietf-twamp

namespace: urn:ietf:params:xml:ns:yang:ietf-twamp

prefix: twamp

reference: RFC XXXX

9. Acknowledgements

Haoxing Shen contributed to the definition of the YANG module in Section 5.

Kostas Pentikousis is partially supported by FP7 UNIFY (http://fp7-unify.eu), a research project partially funded by the European Community under the Seventh Framework Program (grant agreement no. 619609). 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.

10. References

10.1. Normative References

[RFC2119]	Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3688]	Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004.
[RFC4656]	Shalunov, S., Teitelbaum, B., Karp, A., Boote, J. and M. Zekauskas, "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, September 2006.
[RFC5357]	Hedayat, K., Krzanowski, R., Morton, A., Yum, K. and J. Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, October 2008.
[RFC6020]	Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010.
[RFC6038]	Morton, A. and L. Ciavattone, "Two-Way Active Measurement Protocol (TWAMP) Reflect Octets and Symmetrical Size Features", RFC 6038, October 2010.

10.2. Informative References

[I-D.elteto-ippm-twamp-mib]	Elteto, T. and G. Mirsky, "Two-Way Active Measurement Protocol (TWAMP) Management Information Base (MIB)", Internet-Draft draft-elteto-ippm-twamp-mib-01, January 2014.
[I-D.ietf-ippm-metric-registry]	Bagnulo, M., Claise, B., Eardley, P., Morton, A. and A. Akhter, "Registry for Performance Metrics", Internet-Draft draft-ietf-ippm-metric-registry-02, February 2015.
[I-D.ietf-netconf-restconf]	Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", Internet-Draft draft-ietf-netconf-restconf-04, January 2015.
[I-D.unify-nfvrg-challenges]	Szabo, R., Csaszar, A., Pentikousis, K., Kind, M. and D. Daino, "Unifying Carrier and Cloud Networks: Problem Statement and Challenges", Internet-Draft draft-unify-nfvrg-challenges-00, October 2014.
[NSC]	John, W., Pentikousis, K., et al., "Research directions in network service chaining", Proc. SDN for Future Networks and Services (SDN4FNS), Trento, Italy IEEE, November 2013.
[RFC4086]	Eastlake, D., Schiller, J. and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC5618]	Morton, A. and K. Hedayat, "Mixed Security Mode for the Two-Way Active Measurement Protocol (TWAMP)", RFC 5618, August 2009.
[RFC5938]	Morton, A. and M. Chiba, "Individual Session Control Feature for the Two-Way Active Measurement Protocol (TWAMP)", RFC 5938, August 2010.
[RFC6241]	Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, June 2011.
[RFC7426]	Haleplidis, E., Pentikousis, K., Denazis, S., Hadi Salim, J., Meyer, D. and O. Koufopavlou, "Software-Defined Networking (SDN): Layers and Architecture Terminology", RFC 7426, January 2015.

Appendix A. Detailed Data Model Examples

In this section we extend the example presented in Section 6 by configuring more fields such as authentication parameters, dscp values and so on.

A.1. Control-Client

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampClient>
   
      <clientAdminState>True</clientAdminState>
	  
      <modePreferenceChain>
         <priority>0</priority>
         <mode>0x00000002</mode>
      </modePreferenceChain>
      <modePreferenceChain>
         <priority>1</priority>
         <mode>0x00000001</mode>
      </modePreferenceChain>
	  
      <keychain>
         <keyid>KeyClient1ToRouterA</keyid>
         <secretKey>secret1</secretKey>
      </keychain>
      <keychain>
         <keyid>KeyForRouterB</keyid>
         <secretKey>secret2</secretKey>
      </keychain>
	  
      <twampClientCtrlConnection>
         <ctrlConnectionName>RouterA</ctrlConnectionName>
         <clientIp>203.0.113.1</clientIp>
         <serverIp>203.0.113.2</serverIp>
         <dscp>32</dscp>
         <keyId>KeyClient1ToRouterA</keyId>
         <dkLen>1024</dkLen>
         <twampSessionRequest>
            <testSessionName>Test1</testSessionName>
            <senderIp>10.1.1.1</senderIp>
            <senderUdpPort>4000</senderUdpPort>
            <reflectorIp>10.1.1.2</reflectorIp>
            <reflectorUdpPort>5000</reflectorUdpPort>
            <paddingLength>0</paddingLength>
            <startTime>0</startTime>
            <testSessionState>ok</testSessionState>
            <sid>1232</sid>
         </twampSessionRequest>
         <twampSessionRequest>
            <testSessionName>Test2</testSessionName>
            <senderIp>203.0.113.1</senderIp>
            <senderUdpPort>4001</senderUdpPort>
            <reflectorIp>203.0.113.2</reflectorIp>
            <reflectorUdpPort>5001</reflectorUdpPort>
            <paddingLenth>32</paddingLenth>
            <startTime>0</startTime>
            <testSessionState>ok</testSessionState>
            <sid>178943</sid>
         </twampSessionRequest>
      </twampClientCtrlConnection>
	  
   </twampClient>
</twamp>

A.2. Server

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampServer>
   
      <serverAdminState>True</serverAdminState>
      <servwait>1800</servwait>
      <dscp>32</dscp>
      <modes>0x00000003</modes>
      <dkLen>1024</dkLen>
      <count>256</count>
	  
      <keychain>
         <keyid>KeyClient1ToRouterA</keyid>
         <secretKey>secret1</secretKey>
      </keychain>
      <keychain>
         <keyid>KeyClient10ToRouterA</keyid>
         <secretKey>secret10</secretKey>
      </keychain>
	  
      <twampServerCtrlConnection>
         <clientIp>203.0.113.1</clientIp>
         <clientTcpPort>16341</clientTcpPort>
         <serverIp>203.0.113.2</serverIp>
         <serverTcpPort>862</serverTcpPort>
         <serverCtrlConnectionState>active</serverCtrlConnectionState>
         <dscp>32</dscp>
         <selectedMode>0x00000002</selectedMode>
         <keyId>KeyClient1ToRouterA</keyId>
         <count>1024</count>
      </twampServerCtrlConnection>
	  
   </twampServer>
</twamp>

A.3. Session-Sender

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampSessionSender>
   
      <twampSenderTestSession>
         <testSessionName>Test1</testSessionName>
         <ctrlConnectionName>RouterA</ctrlConnectionName>  // read-only
         <dscp>32</dscp>
         <fillMode>zero</fillMode>
         <numberOfPackets>900</numberOfPackets>
         <packetDistribution>
            <fixedInterval>1</fixedInterval>
            <fixedIntervalUnits>seconds</fixedIntervalUnits>
         </packetDistribution>
         <senderSessionState>Active</senderSessionState>
         <sentPackets>2</sentPackets>
         <rcvPackets>2</rcvPackets>
         <lastSentSeq>1</lastSentSeq>
         <lastRcvSeq>1</lastRcvSeq>
      </twampSenderTestSession>
	  
      <twampSenderTestSession>
         <testSessionName>Test2</testSessionName>
         <ctrlConnectionName>RouterA</ctrlConnectionName>  // read-only
         <dscp>32</dscp>
         <fillMode>random</fillMode>
         <numberOfPackets>900</numberOfPackets>
         <packetDistribution>
       	   <lambda>1</lambda>
            <lambdaUnits>1</lambdaUnits>
            <maxInterval>2</maxInterval>
            <truncationPointunits>seconds</truncationPointunits>
         </packetDistribution>
         <senderSessionState>Active</senderSessionState>
         <sentPackets>21</sentPackets>
         <rcvPackets>21</rcvPackets>
         <lastSentSeq>20</lastSentSeq>
         <lastRcvSeq>20</lastRcvSeq>
      </twampSenderTestSession>
	  
   </twampSessionSender>
</twamp>

A.4. Session-Reflector

<twamp xmlns="urn:ietf:params:xml:ns:yang:ietf-twamp">
   <twampSessionReflector>
   
      <twampReflectorTestSession>
         <sid>1232</sid>
         <senderIp>10.1.1.1</senderIp>
         <reflectorIp>10.1.1.2</reflectorIp>
         <senderUdpPort>4000</senderUdpPort>
         <reflectorUdpPort>5000</reflectorUdpPort>
         <parentConnectionClientIp>
            203.0.113.1
         </parentConnectionClientIp>
         <parentConnectionClientTcpPort>
            16341
         </parentConnectionClientTcpPort>
         <parentConnectionServerIp>
            203.0.113.2
         </parentConnectionServerIp>
         <parentConnectionServerTcpPort>
            862
         </parentConnectionServerTcpPort>
         <dscp>32</dscp>
         <sentPackets>2</sentPackets>
         <rcvPackets>2</rcvPackets>
         <lastSentSeq>1</lastSentSeq>
         <lastRcvSeq>1</lastRcvSeq>
      </twampReflectorTestSession>
	  
      <twampReflectorTestSession>
         <sid>178943</sid>
         <senderIp>203.0.113.1</senderIp>
         <reflectorIp>192.68.0.2</reflectorIp>
         <senderUdpPort>4001</senderUdpPort>
         <parentConnectionClientIp>
            203.0.113.1
         </parentConnectionClientIp>
         <parentConnectionClientTcpPort>
            16341
         </parentConnectionClientTcpPort>
         <parentConnectionServerIp>
            203.0.113.2
         </parentConnectionServerIp>
         <parentConnectionServerTcpPort>
            862
         </parentConnectionServerTcpPort>
         <reflectorUdpPort>5001</reflectorUdpPort>
         <dscp>32</dscp>
         <sentPackets>21</sentPackets>
         <rcvPackets>21</rcvPackets>
         <lastSentSeq>20</lastSentSeq>
         <lastRcvSeq>20</lastRcvSeq>
      </twampReflectorTestSession>
	  
   </twampSessionReflector>
</twamp>

Authors' Addresses