Two-Way Active Measurement Protocol (TWAMP) Light

This features is the light version of TWAMP, which is an industry standard (RFC 5357) for measuring round-trip performance between two devices that support the TWAMP protocols. TWAMP defines two protocols: the TWAMP-Control protocol and the TWAMP-Test protocol. The TWAMP-Control protocol is used to set up test sessions. The test sessions use the TWAMP-Test protocol to transmit and reflect performance measurement packets. The TWAMP-Control protocol uses TCP for communication, while the TWAMP-Test protocol uses UDP.

TWAMP defines four logical roles; Session-Sender, Session-Reflector, Server, and Control-Client. These logical roles can be split between two entities to form a client/server paradigm (referred to as the two-host implementation in the RFC). The logical roles of the Control-Client and the Server communicate using the TWAMP-Control protocol to set up test sessions. Each test session consists of a transmitter and a reflector, fulfilled by the logical roles of Session-Sender and Session-Reflector respectively.

The Control-Client initiates a TCP connection to the well-known TWAMP-Control port 862. After the TCP connection is established, the Server transmits the first message by sending the ?Server Greetings‘ message. The Control-Client responds with a ?Setup Response‘ message. The three-way TWAMP-Control handshake is completed when the Server responds with the ?Server Start‘ message. The ?Control-Client‘ is now able to transmit command messages to the Server.

The test sessions are set up using the ?Request-Session‘ command message, sent from the Control-Client to the Server. The Server replies with an ?Accept Session‘ message, which indicates if the Server is capable of accommodating the request. The Control-Client may send several ?Request-Session‘ command messages to set up multiple test sessions. To begin the tests, the Control-Client transmits a ?Start-Session‘ command message. The Server replies with a ?Start-Ack‘ message. The Control-Client does not begin its test until it receives the ?Start-Ack‘ message. This allows the Server ample time to configure the test sessions. The Control-Client stops the test sessions with a ?Stop-Sessions‘ message. The Server does not respond to this message.

This feature, TWAMP Light, consists of the TWAMP logical role of the Session-Reflector as defined in Appendix I of RFC 5357. This light version of TWAMP contains two entities: the Client entity takes on the TWAMP logical roles of Session-Sender, Server, and Control-Client, while the Server takes on the TWAMP logical role of the Session-Reflector. To establish TWAMP Light, you must configure endpoints, which define the destination of TWAMP-Test packets generated by the Client. An endpoint receiving a new TWAMP-Test packet creates a test session consisting of the following four-part tuple; client IP address, client UDP port, endpoint IP address, and endpoint UDP port. The tuple does not include the VR because it requires the Default VR for the first phase. A session timeout value, configured globally, determines the amount of time test sessions exist after the last reception of a TWAMP-Test packet. Test sessions are used to keep track of the session data, such as the sequence number. The Session-Reflector still responds to TWAMP-Test packets that do not match an existing test session or if a new test session cannot be created due to lack of resources.

Session Information
  Used: 165 of 200
  Timeout: 300 seconds
Endpoints 	Port  Sessions Rx Packets Tx Packets
----------------------------------------------------------
19.1.1.100 	5000  5         3091          3091        
19.1.1.100 	5001  40        5521          5521        
19.1.1.100 	5002  40        4728          4728        
19.1.1.100 	5003  40        3916          3916        
18.1.1.100 	5000  40        9266          9266        

Displayed 5 endpoints

TWAMP Endpoint
Endpoint Information
    Local Address: 19.1.1.100		Listening Port: 			5000
    Received Packets: 7948		Transmitted Packets: 7948
    Active Sessions: 5  

Session created on Thu Nov 13 15:41:49 2014
    Peer Address: 19.1.1.2  		Port: 11001
    Sequence Number: 1575  		Last recv'd packet: 84ms

Session created on Thu Nov 13 15:41:49 2014
    Peer Address: 19.1.1.2		Port: 11002
    Sequence Number: 1555		Last recv'd packet: 16ms
Session created on Thu Nov 13 15:41:49 2014
    Peer Address: 19.1.1.2		Port: 11003
    Sequence Number: 1595		Last recv'd packet: 241ms

Session created on Thu Nov 13 15:41:49 2014
    Peer Address: 19.1.1.2		Port: 11004
    Sequence Number: 1729		Last recv'd packet: 249ms

Session created on Thu Nov 13 15:41:49 2014
    Peer Address: 19.1.1.2		Port: 11005
    Sequence Number: 1489		Last recv'd packet: 15ms

Displayed 5 sessions