Propagation Delay Determination in G.709 Optical Transport Networks
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Solution Overview
Problem
Existing methods for determining propagation delay in G.709 compliant Optical Transport Networks require significant memory and time, especially when multiple Tandem Connection Monitoring (TCM) fields are used, as they rely on software calculations and storage of timing information for each field.
Innovation Solution
A method that calculates propagation delay by identifying frame numbers and byte offsets of incoming and outgoing frames, allowing for the determination of transmission time differences, which serves as a common reference for all TCM fields, reducing the need for additional memory and enabling faster calculations through hardware implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If timing information is stored for each TCM field, then propagation delay can be determined for multiple users, but memory requirements increase significantly
Solution Approach 1:
The patent merges the timing information storage for all six TCM fields into a single shared memory location rather than maintaining separate storage for each field. The initiator node stores timing data in a common memory area, and all TCM fields reference this shared storage, thereby supporting multiple users while minimizing memory consumption.
Solution Approach 2:
The patent implements a universal timing storage mechanism that serves all TCM fields simultaneously. A single memory structure is designed to handle timing information for multiple users and multiple TCM fields, making the storage system multi-functional rather than dedicated to a single field.
2Adaptability or versatility
If software is used for propagation delay calculations, then flexibility is maintained, but calculation time increases
Solution Approach 1:
The patent replaces software-based propagation delay calculations with hardware-based circuitry. Dedicated hardware circuits perform the timing measurements and delay calculations directly, eliminating the need for software processing. This substitution maintains calculation flexibility through configurable hardware while dramatically reducing calculation time.
Solution Approach 2:
The patent performs timing information storage and preliminary processing in advance using hardware circuits. The initiator node captures and stores timing data in hardware memory as frames are transmitted, preparing the data for immediate use without requiring time-consuming software processing when the propagation delay needs to be determined.
Data Source
AI summary
A propagation delay in the transmission of a frame from an initiator node to a peer node is determined by initially identifying a frame number and byte offset of a first incoming frame from the peer node at a time when the initiator node outputs a portion of a transmitted frame. The portion of the transmitted frame may be the first byte of a sub-frame within the transmitted frame. At the peer node, the frame number and byte offset of a second frame to be supplied to the initiator node is identified at a later time when the frame portion transmitted by the initiator node is received by the peer node, and such information is transmitted to the initiator node. Thus, since the frames output and received by the initiator node are typically of fixed duration, the frame number and byte offset of the incoming frame represent the time when the initiator node outputs the frame portion (a transmit time). In addition, the frame number and byte offset of the second frame represents the time at which the frame portion is received by the peer node (a receive time). Accordingly, by comparing the frame numbers and byte offsets of the first and second frames received from the peer node, a difference between transmit and receive times or propagation delay can be obtained.