Patent ID: 7397765

Claim:
A bandwidth monitoring device for monitoring a packet bandwidth, comprising: a counter residual quantity value determining portion which determines a current counter residual quantity value which represents a residual value of a packet length counter value by adding up inputted packet lengths and subtracting outputted packet lengths immediately prior to input of a next input packet; and a monitoring results determining portion which sets determination criteria, and determines in accordance with the determination criteria whether input packets violate or comply with a monitored bandwidth; wherein the determination criteria include a determination criterion, based on the counter residual quantity value from said counter residual quantity value determining portion, that all input packets are in compliance with the monitored bandwidth when the counter residual quantity value is equal to or less than a first threshold value; wherein the determination criteria include a determination criterion such that a drop probability, by which a determination is made that input packets violate the monitored bandwidth when the counter residual quantity value exceeds the first threshold value, becomes greater pursuant to increases in the counter residual quantity value; and wherein the determination criteria include a determination criterion that all input packets violate the monitored bandwidth when the counter residual quantity value exceeds a second threshold value which is greater than the first threshold value, wherein the counter residual quantity value determining portion determines the current counter residual quantity value by computing an elapsed time which has passed since a packet having an identical flow identifier as the inputted packet was in compliance with the monitored bandwidth, multiplying the elapsed time by the monitored bandwidth, computing a counter decrement from when the preceding packet having the identical flow identifier was determined to be in compliance with the monitored bandwidth until immediately prior to the packet being inputted, and subtracting the counter decrement from the packet length counter value to obtain the counter residual quantity value immediately prior to the packet being inputted.