Patent ID: 7512069

Claim:
A method of measuring jitter characteristics of a specific data packet flow of normal network traffic, including one or more packets, at a first location on a network relative to a second location on the network, comprising: identifying at each one of the first and second locations on the network, a specific IP packet flow of normal network traffic by analyzing data in one or more data fields of each of the IP packets in the IP packet flow and identifying each IP packet in the IP data flow at said locations; associating passively a transmit time code with each identifed IP packet in the IP packet flow transmitted from the first location associating passively a receive time code with each of the identified IP packets received at the second location the transmit and receive time codes derived from respective time code generators without requiring synchronization therebetween, and calculating, for each consecutive pair of IP packets, an inter-arrival time by (i) subtracting the transmit time code associated with the first IP packet from the transmit time code associated with the second IP packet so as to produce a transmit time delta, (ii) subtracting the receive time code associated with the first IP packet from the receive time code associated with the second IP packet so as to produce a receive time delta, and (iii) subtracting the transmit delta from the receive delta; and calculating a jitter value as a smoothed version of two or more inter-arrival times, smoothed over a predetermined number of pairs of consecutive IP packets, wherein the jitter value is indicative of network performance, wherein the smoothed version of the two or more inter-arrival times is characterized as J n =J nâˆ’1 +(|D(p nâˆ’1 ,p n )|âˆ’J nâˆ’1 )/G, wherein J n is an average jitter value, J nâˆ’1 is a previously calculated average jitter value, D(p nâˆ’1 ,p n ) is a variance in delay computed using the n th and nâˆ’1 th packets, and G is a gain parameter.