Method for devices in a network to participate in an end-to-end measurement of latency
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.
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;
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;
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 first time corresponding to a transmission of a first preselected bit in said test packet from said first device;
when said test packet is received by said second device coupled to said network, storing in said second device a second time when the preselected bit in said test packet is received by said second device;
when said test packet is received by said third device coupled to said network, storing in said third device a third time when the preselected hit in said test packet is received by said third device; and
determining the round trip latency of the network path after said test packet is returned to said first device; wherein the pre-selected bit is a first bit of the test packet used by each device along the path to compute the delay on each path segment while determining the round trip latency.
2. 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:
a first network device at the first end of the first path segment being adapted to generate and transmit a test packet, wherein said test packet stores a first time corresponding to the transmission of a first preselected bit in said 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 said test packet from the first network device through the first path segment, store a second time when the preselected bit in said test packet is received from the first network device through the first path segment and transmit said test packet;
a third network device at the second end of the second path segment being adapted to receive said test packet from the second network device through the second path segment, store a third time when the preselected bit in said test packet is received from the second network device through the second path segment and transmit said test packet back to the second network device through the second path segment;
wherein the second network device is further adapted to receive the test packet from the third network device through the second path segment, store a fifth time when the preselected bit in said test packet is received from the third network device through the second path segment, and transmit the test packet back to the first network device;
wherein the first network device is further adapted to receive the test packet from the second network device through the first path segment, store a sixth time when the preselected bit in said test packet is received from the second network device through the first path segment and determine the round trip latency of the network path after said test packet is returned to said first device; wherein the pre-selected bit is a first bit of the test packet used by each device along the path to compute the delay on each path segment while determining the round trip latency.