Triangle Loopback Packet for One-Way Delay Measurement
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Solution Overview
Problem
Conventional loopback OAM protocols cannot directly measure one-way delay in either direction, and they impose a significant computational toll on communications nodes, especially when multiple OAM sessions are required, and do not provide direction-specific fault indication or accurate one-way delay measurement without synchronized clocks.
Innovation Solution
A method involving a 'triangle' loopback test where a communications node sends a triangle loopback packet to a second node, which forwards it to a third node, allowing the first node to determine continuity and one-way delay by calculating the difference in round-trip and one-way delays across the path, using sequence numbers and packet counters to isolate packet loss ratio (PLR) and propagation delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional loopback OAM protocols are used to measure continuity and performance parameters, then basic connectivity monitoring is achieved, but one-way delay measurement in either direction cannot be directly obtained
Solution Approach 1:
The patent segments the communications path into three distinct segments (first node to second node, second node to third node, third node to first node) and uses triangle loopback packets to measure each segment's delay independently. This segmentation enables precise one-way delay measurement for each path segment without requiring complex synchronized clock systems.
Solution Approach 2:
The patent introduces a third communications node as an intermediary to enable indirect measurement of one-way delay. By having the second node forward the packet to the third node and back, the system creates a measurable path that allows calculation of one-way delay without direct point-to-point measurement, thus avoiding the need for synchronized clocks.
2Adaptability or versatility
If multiple OAM sessions are performed to monitor different packet characteristics, then comprehensive network monitoring is achieved, but computational load on communications nodes becomes significant
Solution Approach 1:
The patent makes the triangle loopback packet structure universal by incorporating multiple measurement capabilities (continuity detection, packet loss ratio calculation, one-way delay measurement, and path identification) into a single packet type. This multi-functionality allows comprehensive monitoring of different packet characteristics without requiring separate OAM sessions for each measurement type, thereby reducing computational load.
3Measurement precision
If conventional loopback protocols are used without synchronized clocks, then basic continuity checking is possible, but accurate one-way delay measurement cannot be achieved
Solution Approach 1:
The patent performs preliminary actions by having the second communications node insert its own timestamp before forwarding the packet to the third node. This preliminary timestamping allows the first node to later calculate the one-way delay by comparing timestamps, eliminating the need for synchronized clocks while maintaining measurement accuracy.
Data Source
AI summary
A method of determining packet loss ratio between two communications nodes, the method comprising: transmitting at least one loopback packet configured to be propagated from a first node through a second and third nodes back to the first node; upon traversal of the second node inserting into the loopback packet a first counter for a number of packets sent from the second node to the third node prior to receiving the loopback packet; upon traversal of the third node inserting into the loopback packet a second counter for a number of packets received by the third node from the second node prior to receiving the loopback packet; upon return of the loopback packet to the first node, determining a packet loss ratio between the second and third nodes responsive to the first counter number and the second counter number inserted into the loopback packet.