METHOD, A COMPUTER PROGRAM PRODUCT, AND A CARRIER FOR INDICATING ONE-WAY LATENCY IN A DATA NETWORK

• US 20180316586A1
• Filed: 07/04/2018
• Published: 11/01/2018
• 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
• Granted Patent: US 10,425,309 B2
• Time in Patent Office: Days
• 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

1-15. -15. (canceled)

16. A method for generating a one-way latency profile in a network comprising:

transmitting a plurality of pre-synchronization messages between a requester node comprising a first clock and a responder node comprising a second clock;

calculating, a pre-synchronization offset value between said first clock and said second clock, using data in one of said pre-synchronization messages;

transmitting a plurality of measuring messages comprising a sending time between said requester node and said responder node;

recording, by said responder node, said sending time and a receiving time of each of said measuring messages;

transmitting a plurality of post-synchronization messages between said requester node and said responder node;

calculating, using a post-synchronization data set contained in one of said post-synchronization messages, a post-synchronization offset value between said first clock and said second clock;

interpolating said sending and receiving times of said measuring messages with said pre-synchronization offset value and said post-synchronization offset value to generate said one-way latency profile.

17. The method of claim 16, wherein each pre-synchronization message has a minimum round trip time.

18. The method of claim 17, wherein said round trip time is calculated according to T_1.4−

T_i.1−

(T_1.3−

T_i.2), where i is in an interval [1 . . . N], N is the number of said pre-synchronization messages sent by said requester node, T is a first timestamp of said requester node sending said pre-synchronization messages, T_i.2 is a second timestamp of said responder node receiving said pre-synchronization messages, T_i.3 is a third timestamp of said responder node sending said pre-synchronization messages, and T_i.4 is a fourth timestamp of said requester node receiving said pre-synchronization messages.

19. The method of claim 16, wherein said pre-synchronization offset value is calculated according to ((T₂−

T₁)+(T₃−

T₄))/2, where T₁ is a first timestamp of said requester node sending said pre-synchronization messages, T₂ is a second timestamp of said responder node receiving said pre-synchronization messages, T₃ is a third timestamp of said responder node sending said pre-synchronization messages, and T₄ is a fourth timestamp of said requester node receiving said pre-synchronization messages.

20. The method of claim 16, further comprising:

setting a pre-synchronization absolute clock value as said fourth timestamp of said requester node receiving said pre-synchronization messages.

21. The method of claim 16, further comprising:

measuring an overhead of said requester node to send said measuring messages.

22. The method of claim 16, wherein each post-synchronization message has a minimum round trip time.

23. The method of claim 16, wherein said round trip time is calculated according to T_i.4−

T_i.1−

(T_i.3−

T_i.2), where i is in an interval [1 . . . N], N is the number of said post-synchronization messages sent by said requester node, T_i.1 is a first timestamp of said requester node sending said post-synchronization messages, T_i.2 is a second timestamp of said responder node receiving said post-synchronization messages, T_i.3 is a third timestamp of said responder node sending said post-synchronization messages, and T_i.4 is a fourth timestamp of said requester node receiving said post-synchronization messages.

24. The method of claim 16, wherein said post-synchronization offset value is calculated according to ((T₂−

T₁)+(T₃−

T₄))/2, where T₁ is a first timestamp of said requester node sending said post-synchronization messages, T₂ is a second timestamp of said responder node receiving said post-synchronization messages, T₃ is a third timestamp of said responder node sending said post-synchronization messages and T₄ is a fourth timestamp of said requester node receiving said post-synchronization messages.

25. The method of claim 24, further comprising:

setting a post-synchronization absolute clock value as said fourth timestamp of said requester node receiving said post-synchronization messages.

26. A system to calculate a one-way latency profile between a requester node coupled to a first clock and a responder node coupled to a second clock, comprising:

a first network module executing on said responder node to calculate a pre-synchronization offset value between said first clock and second clock based on one or more of a plurality of pre-synchronization messages transmitted by a second network module executing on a second processor on said requester node to said first module;

said second network module transmitting a plurality of measuring messages comprising a sending time to said first network module;

said first network module recording the sending time and a receiving time of the measuring messages;

said first network module calculating a post-synchronization offset value between said first clock and second clock based on a plurality of post-synchronization messages transmitted between said requester node and a second network module executing on said responder node; and

said first network module interpolating said sending and receiving times with said pre-synchronization offset value and post-synchronization offset value to generate said one-way latency profile from said plurality of latency measurements.

27. The system of claim 26, wherein said pre-synchronization offset value and said pre-synchronization absolute clock value are calculated from said pre-synchronization messages.

28. The system of claim 26, wherein each pre-synchronization message has a minimum round trip time.

29. The system of claim 26, wherein said pre-synchronization offset value is calculated according to ((T₂−

T₁)−

(T₃−

T₄))/2, where T₁ is a first timestamp of said requester node sending said pre-synchronization messages, T₂ is a second timestamp of said responder node receiving said pre-synchronization messages, T₃ is a third timestamp of said responder node sending said pre-synchronization messages, and T₄ is a fourth timestamp of said requester node receiving said pre-synchronization messages.

30. The system of claim 26, wherein said pre-synchronization absolute clock value is set as said fourth timestamp of said requester node receiving said pre-synchronization messages.

31. The system of claim 26, wherein said post-synchronization offset value and said post-synchronization absolute clock value are calculated from said post-synchronization messages.

32. The system of claim 26, wherein said round trip time is calculated according to T_1.4−

T_i.1−

(T_i.3−

T_i.2), where i is in an interval [1 . . . N], N is the number of said post-synchronization messages sent by said requester node, T_i.1 is a first timestamp of said requester node sending said post-synchronization messages, T_i.2 is a second timestamp of said responder node receiving said post-synchronization messages, T_i.3 is a third timestamp of said responder node sending said post-synchronization messages, and T_i.4 is a fourth timestamp of said requester node receiving said post-synchronization messages.

33. The system of claim 26, wherein said post-synchronization offset value is calculated according to ((T₂−

T₁)+(T₃−

T₄))/2, where T₁ is a first timestamp of said requester node sending said post-synchronization messages, T₂ is a second timestamp of said responder node receiving said post-synchronization messages, T₃ is a third timestamp of said responder node sending said post-synchronization messages, and T₄ is a fourth timestamp of said requester node receiving said post-synchronization messages.

34. A system to determine a one-way latency between nodes in a network, comprising:

a first node, wherein the first node is configured to send a first message and determine a first value T1 indicative of a time the first message is sent, and wherein the first node is configured to receive a second message and determine a second value indicative of a time T4 the second message is received;

a second node, wherein the second node is configured to receive the first message from the first node and determine a third value T2 indicative of a time the first message is received, and wherein the second node is configured to send the second message to the first node and determine a fourth value indicative of a time T3 the second message is sent;

a first clock, wherein the first clock determines time T1 and time T4;

a second clock, wherein the second clock determines time T2 and time T4; and

said first node generating said one-way latency profile from a combination of the times, T1, T2, T3, and T4.

35. The system of claim 34, wherein the first clock and the second clock are not synchronized.