Sampling test of network performance

1. A method for testing a communication network, comprising:

generating a flow of test packets, the flow comprising a series of bursts of the test packets separated by intervals having an interval duration, each burst comprising a sequence of the test packets and having a burst duration less than the interval duration, wherein generating the flow comprises generating a test packet having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP);

transmitting the flow of test packets over a path through the network;

measuring arrival characteristics of the test packets in the flow at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic; and

detecting a quality defect in the network based on the measured arrival characteristics;

said detecting a quality defect by computing a statistical feature of said arrival characteristics of the test packets over said series of bursts while disregarding the arrival characteristics of an initial test packet in each burst;

computing, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determining the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determining whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.

2. The method according to claim 1 , wherein the burst duration is no more than one tenth of the interval duration.

3. The method according to claim 1 , wherein the burst duration is no more than 1 sec.

4. The method according to claim 1 , wherein each burst comprises no more than fifty of the test packets.

5. A method for testing a communication network, comprising:

generating a burst of test packets, the burst comprising a sequence of no more than fifty of the test packets and having a burst duration no greater than 1 sec, wherein generating the flow comprises generating a test packet having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP);

transmitting the burst of test packets over a path through the network;

measuring arrival characteristics of the test packets in the burst at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic; and

detecting a quality defect in the network based on the measured arrival characteristics;

said detecting a quality defect comprising by a statistical feature of said arrival characteristics of the test packets over said series of bursts while disregarding the arrival characteristics of an initial test packet in each burst;

computing, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determining the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determining whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.

6. Apparatus for testing a communication network, comprising:

first and second traffic agents, which are coupled to respective end points of a path through the network; and

a testing center, which is coupled to instruct at least the first traffic agent to transmit a flow of test packets having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP) over the path through the network, the flow comprising a series of bursts of the test packets separated by intervals having an interval duration, each burst comprising a sequence of the test packets and having a burst duration less than the interval duration, and to instruct at least the second traffic agent to measure arrival characteristics of the test packets in the flow at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic,

said testing center being adapted to detect a quality defect in the network based on the measured arrival characteristics; and

said testing center being arranged to:

compute a statistical feature of the arrival characteristics of the test packets over the series of the bursts while disregarding the arrival characteristics of an initial test packet in each burst;

compute, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determine the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determine whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.

7. Apparatus for testing a communication network, comprising:

first and second traffic agents, which are coupled to respective end points of a path through the network; and

a testing center, which is coupled to instruct at least the first traffic agent to transmit a burst of test packets having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP) over a path through the network, the burst comprising a sequence of no more than fifty of the test packets and having a burst duration no greater than 1 sec, and to instruct at least the second traffic agent to measure arrival characteristics of the test packets in the burst at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic,

said testing center being adapted to detect a quality defect in the network based on the measured arrival characteristics;

said testing center being arranged to:

compute a statistical feature of the arrival characteristics of the test packets over the series of the bursts while disregarding the arrival characteristics of an initial test packet in each burst;

compute, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determine the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determine whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.

8. A computer software product for testing a communication network in conjunction with first and second traffic agents, which are coupled to respective end points of a path through the network, the product comprising a non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a computer, cause the computer to instruct at least the first traffic agent to transmit a flow of test packets having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP) over the path through the network, the flow comprising a series of bursts of the test packets separated by intervals having an interval duration, each burst comprising a sequence of the test packets and having a burst duration less than the interval duration, and to instruct at least the second traffic agent to measure arrival characteristics of the test packets in the flow at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic, the instructions causing the computer to detect a quality defect in the network based on the measured arrival characteristics;

the instructions causing the computer to:

compute a statistical feature of the arrival characteristics of the test packets over the series of the bursts while disregarding the arrival characteristics of an initial test packet in each burst;

compute, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determine the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determine whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.

9. A computer software product for testing a communication network in conjunction with first and second traffic agents, which are coupled to respective end points of a path through the network, the product comprising a non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a computer, cause the computer to instruct at least the first traffic agent to transmit a burst of test packets having a packet size and data rate chosen according to a predetermined codec used in Voice over Internet Protocol (VoIP) over a path through the network, the burst comprising a sequence of no more than fifty of the test packets and having a burst duration no greater than 1 sec, and to instruct at least the second traffic agent to measure arrival characteristics of the test packets in the burst at a receiving end of the path, the arrival characteristics comprising at least one of a packet loss characteristic, a packet delay characteristic, and a packet jitter characteristic, the instructions causing the computer to detect a quality defect in the network based on the measured arrival characteristics;

the instructions causing the computer to:

compute a statistical feature of the arrival characteristics of the test packets over the series of the bursts while disregarding the arrival characteristics of an initial test packet in each burst;

compute, for the predetermined codec, a Mean Opinion Score (MOS) for each burst based on the arrival characteristics of the test packets thereof;

determine the percentage of bursts in the series for which a corresponding MOS is above a predetermined threshold; and

determine whether call quality over the communication network is inadequate based on a percentage of bursts in the series for which the corresponding MOS is lower than the predetermined threshold.