Abstract: Making use of flow label and traffic class fields in the IPv6 header, an original end-to-end measurement method, called Humble-Burst, is presented to estimate available bandwidth in IPv6 networks. This method overcomes some of the problems common to many types of the existing probing methods, e.g., the long latency and large probe traffic; thus it can be applied to many real-time applications. This method is evaluated in different scenarios using NS2. And simulations show this method is accurate, efficient, quick and really non-intrusive, i.e., without affecting the existing traffic in the path.