Calculating Latency in Computer Networks

• US 20150281028A1
• Filed: 03/31/2014
• Published: 10/01/2015
• Est. Priority Date: 03/31/2014
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Akhter, Aamer, Nedeltchev, Plamen, Pignataro, Carlos M.
• Granted Patent: US 10,250,474 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps

Abstract

In one implementation, data is communicated along a communications route in a network. A mediatrace request is generated for the communications route. Responses to the mediatrace request are received from along the communications route. The hop-by-hop latency is passively measured, from the responses, with one-way delay along the communications route in the network.

Claims

1. A method comprising:

communicating data from a source device to a destination device along a flow path;

transmitting a request from the source device to an intermediary device of the flow path, the request includes an identification of packets of the data and includes a timestamp query;

receiving, from the intermediary device and in response to the request, timestamps for the identified packets of the data received by the intermediary device from the source device; and

calculating, by the source device, a latency of the identified packets of the data on the flow path from the source device to the intermediary device using the timestamps.

2. The method of claim 1 wherein communicating data comprises communicating audio, video, or audio and video data, the packets comprising packets of the audio, video, or audio and video data.

3. The method of claim 1 wherein transmitting the request comprises transmitting a route discovery request for the flow path.

4. The method of claim 3 wherein transmitting the route discovery request comprises transmitting a mediatrace request.

5. The method of claim 3 wherein transmitting the route discover request comprises transmitting the identification as filter and sampling parameters of the data.

6. The method of claim 1 wherein transmitting the request with the timestamp query comprises transmitting the request as a one-way delay request for the packets of the data.

7. The method of claim 1 wherein receiving comprises receiving the timestamps with packet signatures for the identified packets.

8. The method of claim 1 wherein calculating the latency comprises calculating a delay from the packets leaving the source device to arrival at the intermediary device.

9. The method of claim 1 wherein receiving further comprises receiving, in response to the request, other timestamps from other intermediary devices and from the destination device, the other timestamps being for the identified packets of the data received by the other intermediary devices and the destination device, and wherein calculating comprises calculating the latency from the source to the destination.

10. The method of claim 1 wherein communicating the data comprises communicating different types of packets, wherein transmitting the request with the identification comprises transmitting with the identification of the packets of the different types, wherein receiving comprises receiving the timestamps for the different types, and wherein calculating comprises calculating separate latencies for the different types.

11. The method of claim 1 further comprising receiving, by the source device and from a requestor device outside the flow path, an instruction to initiate the request, and providing the latency to the requestor device.

12. The method of claim 1 wherein transmitting the request comprises transmitting the request with a reverse request for the destination device to gather timestamps for destination device to source device latency.

13. The method of claim 12 wherein calculating comprises calculating a round trip travel time.

14. The method of claim 13 wherein calculating the round trip travel time comprises calculating the latency from the source device to the intermediary device, from the intermediary device to the source device, and from receipt by the intermediary device of the request to a response from the intermediary device to the source device.

15. A network device comprising:

a communication interface configured to transmit path discovery requests for one-way delay for nodes along a flow path of data; and

a controller configured to gather timestamps from the nodes along the flow path and calculate latency from the timestamps.

16. The network device of claim 15 wherein the controller is a controller of a source of data of the flow path, the source comprising an initiator of the path discovery requests configured to gather the timestamps and calculate the latency.

17. The network device of claim 15 wherein the controller is configured to gather the timestamps from the nodes as part of path discovery using mediatrace, the timestamps being for passive, path aware monitoring of the flow path.

18. The network device of claim 15 wherein the controller is configured to calculate the latency for each hop in the flow path from a source to a destination, the latency for reverse direction communications from the destination to the source, and a round trip travel time between the source and the destination.

19. A method comprising:

communicating data along a communications route in a network;

generating a mediatrace request for the communications route;

receiving responses to the mediatrace request from along the communications route; and

passively measuring, from the responses, hop-by-hop latency with one-way delay along the communications route in the network.

20. The method of claim 19 wherein communicating the data comprises communicating user traffic, wherein passively measuring comprises measuring the hop-by-hop latency of the user traffic, wherein generating and receiving comprise obtaining timestamps for hops where the communications route is dynamically established.