The new feature TWAMP light has been introduced in version 2.15.0. TWAMP is an abbreviation for Two-Way Active Measurement Protocol and has been standardized by IETF and described in RFC 5357.
Essentially TWAMP makes it possible to send traffic from a Netrounds probe towards a TWAMP capable device (e.g. a router), which will then reflect the stream back to the Netrounds probe, so that network metrics such as loss, delay and jitter can be calculated.
TWAMP typically requires a control protocol to perform a handshake between the initiator (the Netrounds probe) and the responder (the device). TWAMP light is however briefly described in Appendix 1 in the RFC, in which no control signaling is required.