Sink Node CBR Rate Adaptation via Path Overhead Insertion
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Solution Overview
Problem
Existing solutions for transporting constant bit rate (CBR) clients in telecom networks face challenges such as high overhead bandwidth requirements, complexity in deriving client signal rates, and latency issues due to the lack of ITU-T Generic Mapping Procedure (GMP) overhead in server channels, particularly in the MTN project of ITU-T SG15, which complicates clock domain compatibility and requires significant processing at intermediate nodes.
Innovation Solution
The solution involves using a mechanism that allows variable spacing between GMP windows by inserting a special ordered set (OS) of path overhead (POH) blocks into the 64B/66B block stream, enabling rate adaptation through the insertion or removal of idle blocks, allowing the sink node to recover the client signal rate accurately by combining GMP overhead and idle block information, and using existing nodes for padding adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If GMP overhead is used in server channels for CBR client transport, then client signal rate derivation is simplified and bandwidth efficiency is improved, but intermediate nodes require complex processing capabilities that are not available in legacy nodes
Solution Approach 1:
The patent extracts the GMP overhead processing function from intermediate nodes and relocates it to the sink node. The path overhead containing rate adaptation information is inserted at the source node and transmitted through intermediate nodes without modification, allowing the sink node to perform all GMP processing and client signal rate derivation independently.
Solution Approach 2:
The patent introduces path overhead as an intermediary carrier that transports rate adaptation information from the source node through intermediate nodes to the sink node. This path overhead acts as a mediator that enables GMP functionality without requiring intermediate nodes to process or understand GMP protocols.
2Adaptability or versatility
If packet encapsulation is used for CBR client transport, then network compatibility is improved, but overhead bandwidth increases and latency increases
Solution Approach 1:
The patent segments the CBR client signal into fixed-size blocks and organizes them into structured path frames with embedded GMP overhead. This segmentation approach maintains the efficiency of block-based processing while adding minimal overhead compared to full packet encapsulation, and enables direct GMP rate adaptation without packet processing complexity.
3Reliability
If fixed number of bits per GMP window is maintained, then GMP protocol compliance is ensured, but clock domain differences between source and intermediate nodes cannot be accommodated
Solution Approach 1:
The patent introduces dynamic rate adaptation within GMP windows by allowing variable numbers of data blocks per window based on actual client signal rate measurements. The path overhead dynamically adjusts the number of data blocks to transmit in each window to accommodate clock domain differences, while maintaining GMP protocol structure and compliance.
Data Source
AI summary
A method and apparatus includes receiving at a sink node a path signal frame and a modified set of idle character 64B/66B blocks. The path signal frame includes encoded client data signal 64B/66B blocks, path overhead 64B/66B data blocks and a control 64B/66B block. The link bit rate is measured. The number of idle character 64B/66B blocks is determined. The data blocks of the CBR client signal are extracted from the encoded client data signal 64B/66B blocks and the CBR client signal is regenerated from the extracted data blocks. A bit rate of the CBR client signal is determined using the measured link bit rate and the number of idle character 64B/66B blocks. The rate of a CBR signal clock is adjusted for transmitting the CBR client signal at the determined bit rate.