Method, a computer program product, and a carrier for indicating one-way latency in a data network

• US 9,300,556 B2
• Filed: 06/22/2015
• Issued: 03/29/2016
• Est. Priority Date: 09/22/2004
• Status: Active Grant

• Current Assignee: Accedian Networks Inc. (Cisco Systems, Inc.)
• Original Assignee: Accedian Networks Inc. (Cisco Systems, Inc.)
• Inventors: Hansson, Kjell, Hagsand, Olof
• Primary Examiner(s): Rinehart, Mark
• Assistant Examiner(s): ONAMUTI, GBEMILEKE J
• Application Number:
  US14/745,676
• Publication Number:
  US 20150288582A1
• Time in Patent Office: 281 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 2212/00 Encapsulation of packets
• CPC Class Codes: H04L 43/067 using time frame reporting
• CPC Class Codes: H04L 43/0852 Delays
• CPC Class Codes: H04L 43/0858 One way delays
• CPC Class Codes: H04L 65/65 Network streaming protocols, e.g. real-time transport protocol [RTP] or real-time control protocol [RTCP]
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 7/10 Arrangements for initial synchronisation

Abstract

Disclosed herein is a method, a computer program product, and a carrier for indicating one-way latency in a data network (N) between a first node (A) and a second node (B), wherein the data network (N) lacks continuous clock synchronization, comprising: a pre-synchronization step, a measuring step, a post-synchronization step, an interpolation step, and generating a latency profile. The present invention also relates to a computer program product incorporating the method, a carrier comprising the computer program product, and a method for indicating server functionality based on the first aspect.

Claims

1. A system for determining one-way latency between a first computer node (A) having a first clock and a second computer node (B) having a second clock, comprising:

a network module running on said first computer node (A) to

pre-synchronize said first clock of said first computer node (A) with said second clock of said second computer node (B), to determine a first clock difference and a first absolute clock value;

measure a sending time and a receiving time associated with each measurement message within a plurality of measurement messages;

post-synchronize said first clock of said first computer node (A) with said second clock of said second computer node (B), to determine a second clock difference and a second absolute clock value;

perform interpolating, comprising

adjusting the sending time associated with each measurement message by an additive adjustment value, the adjustment value calculated with use of an interpolation between the first clock difference and the second clock difference, the interpolation performed with use of the first clock difference and the sending time of the measurement message and a calculation of a ratebias as a rate of change in clock difference over time; and

calculate the one-way latency associated with a measurement message in the data network between said first computer node (A) and said second computer node (B); and

generate a latency profile.

2. The system of claim 1, wherein said adjusting further comprises calculating a shift.

3. The system of claim 2, wherein said shift is calculated further based on

an overhead required to send the measurement message.

4. The system of claim 1, wherein the ratebias is calculated as a fraction comprising a numerator calculated from the second clock difference minus the first clock difference divided by a denominator calculated from the second absolute clock value minus the first absolute clock value.

5. The system of claim 4, wherein the interpolation comprises:

calculating a time difference between the second absolute clock value and the sending time of the measurement message; and

adding the first clock difference to a product of the ratebias and the time difference.

6. The system of claim 5, wherein the adjustment value is further calculated by the addition of an overhead required to send the measurement message.

7. A system to generate a one-way latency profile between a first computer node (A) having a first clock and a different second computer node (B) having a second clock, located in a data network without continuous clock synchronization, comprising:

a network module running on said first computer node (A) to

pre-synchronize said first clock of said first computer node (A) with said second clock of said second computer node (B) to

generate pre-synchronization values representing one or more absolute clock values and one or more clock difference values, and

obtain a first absolute clock value and a first clock difference value from said one or more absolute clock values and one or more clock difference values;

collect, following said pre-synchronizing, a predetermined number of time measurements, using a plurality of measurement messages;

post-synchronize, following said collecting, said first clock of said first computer node (A) with said second clock of said second computer node (B) to

generate post-synchronization values representing one or more absolute clock values and one or more clock difference values, and

obtain a second absolute clock value and a second clock difference value from said one or more absolute clock values and one or more clock difference values,

interpolate said plurality of time measurements to create a predetermined number of latency measurements,

said interpolating comprising adjusting said time measurements by an additive adjustment value, the adjustment value calculated with use of an interpolation between the first clock difference and the second clock difference, the interpolation performed with use of the first clock difference and the sending time of the measurement message and a calculation of a ratebias as a rate of change in clock difference over time; and

generate said one-way latency profile based on said latency measurements.

8. The system of claim 7, wherein said adjusting further comprises calculating a shift.

9. The system of claim 8, wherein said shift is calculated further based on

an overhead required to send the measurement message.

10. The system of claim 7, wherein said pre-synchronizing is carried out using a plurality of synchronization request and synchronization response messages.

11. The system of claim 7, wherein said post-synchronizing is carried out using a plurality of synchronization request and synchronization response messages.

12. The system of claim 7, wherein the ratebias is calculated as a fraction comprising a numerator calculated from the second clock difference minus the first clock difference divided by a denominator calculated from the second absolute clock value minus the first absolute clock value.

13. The system of claim 12, wherein the interpolation comprises:

calculating a time difference between the second absolute clock value and the sending time of the measurement message; and

adding the first clock difference to a product of the ratebias and the time difference.

14. The system of claim 13, wherein the adjustment value is further calculated by the addition of an overhead required to send the measurement message.