Method for devices in a network to participate in an end-to-end measurement of latency

• US 8,830,860 B2
• Filed: 07/05/2012
• Issued: 09/09/2014
• Est. Priority Date: 07/05/2012
• Status: Active Grant

• Current Assignee: Accedian Networks Inc. (Cisco Systems, Inc.)
• Original Assignee: Accedian Networks Inc. (Cisco Systems, Inc.)
• Inventors: Robitaille, Claude, Trudeau, Pierre
• Primary Examiner(s): Ton, Dang
• Assistant Examiner(s): AMBAYE, MEWALE A
• Application Number:
  US13/542,449
• Publication Number:
  US 20140010094A1
• Time in Patent Office: 796 Days
• Field of Search: 370/252, 370/465, 370/468, 709/230
• US Class Current: 370/252
• CPC Class Codes: H04B 17/00 Monitoring; Testing of line transmission systems H04B3/46; arrangements for monitoring or testing transmission systems employing electromagnetic waves other than radio waves H04B10/07
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04L 43/062 related to network traffic
• CPC Class Codes: H04L 43/0852 Delays
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 43/0864 Round trip delays
• CPC Class Codes: H04L 43/10 Active monitoring, e.g. heartbeat, ping or trace-route
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps

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.

Claims

1. A method of determining a latency of a path segment in a communication network having multiple 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 multiple path segments in said network,

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,

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.

2. The method of claim 1 in which said receipt time when a preselected bit in said test packet is received by said second device is stored in said second device, and which includes determining a latency of the path segment between said first and second devices by determining the difference between the two stored times.

3. The method of claim 1 in which said difference between (i) a transmit time when said preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when said test packet is received by said second device is stored in said second device, and which includes determining a latency of the path segment between said first and second devices by retrieving said difference from said second device.

4. The method of claim 1 in which said test packet is transmitted serially from said second device to a plurality of additional devices coupled to said network, and

each time said test packet is received by one of said additional devices, storing in said additional device at least one of (a) a receipt time when a preselected bit in said test packet is received by said additional device and (b) the difference between (i) a transit time when said preselected bit in said test packet is transmitted from said first device and (ii) a receipt time when said test packet is received by said additional device.

5. The method of claim 1 in which said test packet is returned from said second device to said first device.

6. The method of claim 4 in which said test packet is returned from one of said additional devices to said first device via the same devices traversed by said test packet during transmission from said first device to said one additional device.

7. The method of claim 1 which includes

storing in said test packet a transit time when a preselected bit in said test packet is transmitted from said second device,

when said test packet is received by a third device coupled to said network, storing in said third device a receipt time when said second preselected bit in said test packet is received by said third device, and

determining a latency of the path segment between said second and third devices by determining the difference between the second-device transmit time stored in said test packet and a receipt time stored in said third device.

8. The method of claim 7 in which said test packet has first and second timestamp fields, and which includes

storing in said first field a transit time when a preselected bit in said test packet is transmitted from said first device, and

storing in said second field a transit time when a preselected bit in said test packet is transmitted from said second device.

9. The method of claim 1 in which said test packet is transmitted from said first device to said second device while normal packets are being transported through said network.