Method for devices in a network to participate in an end-to-end measurement of latency
First Claim
1. A method of determining a round trip latency of a network path in a communication network having at least two path segments, that uses multi-bit data packets, said method comprising;
- generating a test packet for use in determining the latency of each of said at least 2 path segments in said network path;
transmitting said test packet between first and second devices coupled to said network at opposite ends of a first path segment, and then between said second device and a third device coupled to opposite ends of a second path segment; and
returning said test packet to said first device by transmitting said test packet between said third and second devices and then between said second and first device;
storing in said test packet a transmit time when a first preselected bit in said test packet is transmitted from said first device;
when said test packet is received by said second device coupled to said network, storing in said second device the difference between (i) the transmit time when said first preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when a second preselected bit in said test packet is received by said second device; and
when said test packet is received by said third device coupled to said network, storing in said third device the difference between (i) the transmit time when said preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when a second preselected bit in said test packet is received by said third device; and
determining the round trip latency of the network path when said test packet is returned from the third device to said first device via the same devices traversed by said test packet during transmission from said first device to said third device.
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Abstract
A method of determining the latency of path segments in a communication network that uses multi-bit data packets comprises generating a test packet for use in determining the latency of path segments in the network; transmitting the test packet from a first device coupled to the network; storing in the test packet the time when a preselected bit in the test packet is transmitted from the first device; when the test packet is received by a second device coupled to the network, storing in the second device at least one of (a) the time when a preselected bit in the test packet is received by the second device and (b) the difference between (i) the time when the preselected bit in the test packet is transmitted from the first device and (ii) the time when the test packet is received by the second device.
57 Citations
16 Claims
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1. A method of determining a round trip latency of a network path in a communication network having at least two path segments, that uses multi-bit data packets, said method comprising;
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generating a test packet for use in determining the latency of each of said at least 2 path segments in said network path; transmitting said test packet between first and second devices coupled to said network at opposite ends of a first path segment, and then between said second device and a third device coupled to opposite ends of a second path segment; and returning said test packet to said first device by transmitting said test packet between said third and second devices and then between said second and first device; storing in said test packet a transmit time when a first preselected bit in said test packet is transmitted from said first device; when said test packet is received by said second device coupled to said network, storing in said second device the difference between (i) the transmit time when said first preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when a second preselected bit in said test packet is received by said second device; and when said test packet is received by said third device coupled to said network, storing in said third device the difference between (i) the transmit time when said preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when a second preselected bit in said test packet is received by said third device; and determining the round trip latency of the network path when said test packet is returned from the third device to said first device via the same devices traversed by said test packet during transmission from said first device to said third device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for determining a round trip latency of a network path in a communication network, having at least two path segments comprising a first and second path segment, each having a first and second end, wherein said communication network uses multi-bit data packets, comprising:
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a first network device at the first end of the first path segment being adapted to generate a test packet and transmit the test packet; a second network device at the second end of the first path segment and at the first end of the second path segment being adapted to receive the test packet, to store a first packet send time of the test packet from the first device to the second device, to use the stored first packet send time to calculate a latency of a first path segment between the first device and the second device, and to transmit the test packet; a third network device at the second end of the second path segment, said third network device adapted to receive the test packet, to store a second packet send time of the test packet from the second device to the third device, to use the second packet send time to calculate a latency of a second path segment between the second device and the third device, and to transmit the test packet back to the second network device; the second network device being adapted to receive the test packet from the third network device, to store a third packet send time of the test packet from the third device to the second device, to use the stored third packet send time to calculate a latency of the second path segment between the third and second device, and to transmit the test packet back to the first network device; the first network device being adapted to receive the test packet from the second network device, to store a fourth packet send time of the test packet from the second device to the first device, and to use the fourth packet send time to calculate a latency of the first path segment between the second device and the first device; the third network device being adapted to determine the latency of the network path in a first direction by combining the latency of the first and second path segments; and the first network device being adapted to determine the round trip latency of the network path by combining the latency in the first direction and the latency of the first and second path segments when said test packet is returned from the third device to said first device via the same devices traversed by said test packet during transmission in the first direction. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification