1. A receiving node that receives sequences of probe packet pairs through a data transfer path from a sending node, the receiving node comprising: an extraction unit that extracts time stamp information and probe packet rate (u) from the probe packets; a strain calculation unit, coupled to the extraction unit, that calculates an inter-packet strain value of each pair of the probe packets and also calculates an average and variance of the inter-packet strain values; a matrix generator, coupled to the extraction unit, that produces a matrix H in response to the probe packet rate (u) where H=[u 1]; a Kalman filter, coupled to the strain calculation unit and the matrix generator, that receives the average inter-packet strain value (ε), the inter-packet strain variance (R), the matrix H, an identity matrix (I), a covariance of process noise Q matrix, initial estimates of a state vector {circumflex over (x)} 0 and an error covariance matrix P 0 and then produces an updated state vector estimate {circumflex over (x)} k ; an available bandwidth calculation unit, coupled to the Kalman filter, that uses the updated state vector estimate {circumflex over (x)} k to update an available bandwidth estimate {circumflex over (B)} and that outputs the updated available bandwidth estimate {circumflex over (B)}; and a compare unit, coupled to the extraction unit, the strain calculator, and the available bandwidth calculation unit, that receives the probe packet rate (u) and the updated available bandwidth estimate {circumflex over (B)} and outputs an indication to the strain calculator on whether or not the strain calculation unit should make calculations for a current sequence of the probe packet pairs.