Method and apparatus of estimating available bandwidth on a packet network

Apparatus for estimating available bandwidth of a packet network comprising:

• means for determining the inter-packet intervals in a received train of packets that were injected into the network with known inter-packet intervals;
• means for determining a variance of a distribution of sojourn times through the network of the packets in the received train of packets from the determined inter-packet intervals in the received train and the known inter-packet intervals;
• and
• means for estimating the available bandwidth of the packet network from the determined variance;
• wherein the means for determining a variance of sojourn times comprises:
• means for calculating for each packet j in the received train of N packets the sum over each packet k of the difference between the inter-packet interval between packets j and k and the known inter-packet interval between packets j and k in the train of packets injected into the network to determine the difference of sojourn times for packet j against all other packets in the received train;
• means for dividing by N the sum for each packet j of the calculated differences between inter-packet intervals in the output train and corresponding intervals in the input train to determining the deviation of the sojourn time for each packet j from the mean sojourn time;
• and
• means for determining the variance of the sojourn times for all the packets in the received train by calculating the average over N of the sum of the squares of the deviations determined for each packet j by the means for dividing.

A computer readable media tangibly embodying a program of instructions executable by a computer to perform a method, the method comprising the steps of:

• determining the inter-packet intervals in a received train of packets that were injected into the network with known inter-packet intervals;
• determining a variance of a distribution of sojourn times through the network of the packets in the received train of packets from the determined inter-packet intervals and the known inter-packet intervals;
• and
• estimating the available bandwidth of the packet network from the determined variance;
• wherein in the method the step of determining a variance of sojourn times comprises:
• a) determining for each packet j in the received train of N packets the difference of sojourn times for packet j against all other packets in the received train by calculating the sum over each packet k of the difference between the inter-packet interval between packets j and k and the known inter-packet interval between packets j and k in the train of packets injected into the network;
• b) determining the deviation of the sojourn time for each packet j from the mean sojourn time of the packets in the train by dividing the sum calculated in step a) for each packet j by N;
• and
• c) determining the variance of the sojourn times of all the packets in the received train by calculating the average over N of the sum of the squares of the deviations determined in step b) of each packet j.