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

• US 8,948,210 B2
• Filed: 03/03/2014
• Issued: 02/03/2015
• 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:
  US14/194,885
• Publication Number:
  US 20140177654A1
• Time in Patent Office: 337 Days
• Field of Search: 709/224, 713/400, 370/503
• US Class Current: 370/503
• 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-synchronisation step, a measuring step, a post-synchronisation 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 method 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:

pre-synchronizing said first clock of said first computer node (A) with said second clock of said second computer node (B),

said pre-synchronizing further comprising obtaining a first clock difference value and a first absolute clock value;

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

post-synchronizing said first clock of said first computer node (A) with said second clock of said second computer node (B),

said post-synchronizing further comprising obtaining a second clock difference value and a second absolute clock value;

interpolating, comprising

adjusting the sending time associated with each measurement message,

said adjusting based on

the sending time,

the said first and second clock difference values, and

the said first and second absolute clock values,

further wherein said adjusting comprises calculating a ratebias,

said calculating of ratebias comprising calculating a numberator=(CDIFF1−

CDIFF0) wherein

CDIFF1 is the second clock difference value, and

CDIFF0 is the first clock difference value,

calculating 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) as the difference between

the receiving time associated with the measurement message, and

the adjusted sending time associated with the measurement message; and

generating a latency profile.

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

3. The method of claim 2, wherein said shift is calculated using

said ratebias,

said first clock difference value, and

said first absolute clock value.

4. The method of claim 3, wherein said shift is calculated further based on

the sending time associated with a measurement message and

an overhead required to send the measurement message.

5. A method for generating 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:

pre-synchronizing 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,

said pre-synchronizing carried out using a plurality of synchronization request and synchronization response messages;

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

following said collecting, post-synchronizing 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,

said post-synchronizing carried out using a plurality of synchronization request and synchronization response messages;

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

said interpolating comprising adjusting said time measurements using said first and second absolute clock values and said first and second clock difference values,

wherein said adjusting comprises calculating a ratebias; and

said calculating of ratebias comprising calculating a numberator=(CDIFF1−

CDIFF0) wherein

CDIFF1 is the second clock difference value, and

CDIFF0 is the first clock difference value,

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

6. The method of claim 5, wherein said adjusting further comprises calculating a shift.

7. The method of claim 6, wherein said shift is calculated using

said ratebias,

said first clock difference value, and

said first absolute clock value.

8. The method of claim 7, wherein said shift is calculated further based on

the sending time associated with a measurement message and

an overhead required to send the measurement message.