Method for measuring delay parameters in a network

• US 6,445,681 B1
• Filed: 09/15/1999
• Issued: 09/03/2002
• Est. Priority Date: 09/15/1999
• Status: Expired due to Term

• Current Assignee: OL Security LLC (Intellectual Ventures LLC)
• Original Assignee: VocalTec Communications Incorporated (B. Riley Financial, Inc.)
• Inventors: Pogrebinsky, Vladimir
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): LEE, CHI HO A
• Application Number:
  US09/395,975
• Time in Patent Office: 1,084 Days
• Field of Search: 370/235, 370/503, 370/252-3, 370/508, 370/509, 370/514, 370/516, 370/518, 370/519, 370/389, 370/392, 370/520, 370/229, 370/230, 370/230.1, 370/231, 455/67.1, 455/67.6, 455/1.15, 375/224, 375/354, 375/356, 375/359
• US Class Current: 370/252
• 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 43/50 Testing arrangements
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]

Abstract

A method for measuring delay parameters in a packet switched network between node A and node B, each having a clock, is disclosed The method includes the steps of: measuring a first relative one way delay (ROWD1) from node A to node B, measuring a second relative one way delay (ROWD2) from nude B to node A and calculating the difference between the first and second relative one way delays for providing a relative one way delay (ROWD) parameter. Methods for improving TCP protocol and detecting congestion in a packet switched network using ROWD measurements are also provided.

Claims

1. A method for measuring delay in a packet switched network between node A and node B, each having a clock comprising the steps of:

measuring a first relative one way delay (ROWD1) from node A to node B by using said clocks at node A and node B which are unsynchronized with respect to each other;

measuring a second relative one way delay (ROWD2) from node A to node B by using said clocks at node A and node B which are unsynchronized with respect to each other, and

determining relative one way delay (ROWD) parameter by subtracting said first relative one way delay from said second relative one way delay in accordance with the following equation;

2. The method of claim 1, wherein the step of determining ROWD1 comprising the steps of:

node A sending to node B a first probe packet at a time A1;

node B receiving said first probe packet at time B1; and

calculating ROWD1 as ROWD1=B1−

A1.

3. The method of claim 1, wherein the step of determining ROWD2 comprising the steps of:

node A sending to node B a second probe packet at a time A2;

node B receiving said second probe packet at time B2; and

calculating ROWD2 as ROWD2=B2−

A2.

4. The method of claim 1, wherein said packet switched network is the Internet.

5. The method of claim 2, wherein said first probe packet includes packets of Real Time Transport Control Protocol (RTCP).

6. The method of claim 1, wherein an absolute parameter of one way delay (OWD) Is calculated by subtracting a clock difference (CD) of said clocks of said node A and said node B from said ROWD, which calculation is provided by the following equation:

7. The method of claim 1, wherein the difference between consecutive measurements of ROWD (Δ

ROWD) is used for learning a network behavior.

8. The method of claim 3, wherein said second probe packet includes packets of Real Time Transport Control Protocol (RTCP).

9. A method for detecting congestion in a packet switched network by measuring relative one way delay (ROWD), comprising the steps of:

measuring a first relative one way delay (ROWD1) from node A to node B;

measuring a second relative one way delay (ROWD2) from node A to node B;

calculating the difference between said first and second relative one way delays for providing a relative one way delay (ROWD) parameter by using the following equation;

10. The method of claim 9, wherein the step of estimating A_n is according to the equation:

$A_n=A_{n-1}·<br><br>\left(\frac{15}{16}\right)+\mathrm{ROWDn}·<br><br>\frac{1}{16}.$

11. The method of claim 9 wherein the step of estimating J_n is according to the equation:

$J_n=J_{n-1}·<br><br>\frac{4}{5}+<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{ROWD}}_n<br><br>·<br><br>\frac{1}{5}.$

12. The method of claim 9 wherein said dynamic threshold T_d is vary according to the equation;

13. The method of claim 11, wherein the step of detecting congestion includes analyzing the growth of said ROWD in comparison to T_d.

14. A method for improving bit rate control of Transmission Control Protocols (TCPs) by employing a relative one way delay (ROWD) parameter comprising the steps of:

providing clocks at node A and node B, said clocks unsynchronized with respect to each other;

measuring a first relative one way delay (ROWD1) from node A to node B;

measuring a second relative one way delay (ROWD2) from node A to node B;

determining the difference between said first and second relative one way delays for providing a relative one way delay (ROWD) parameter by using the following equation;