Hybrid Timing Source for Synchronous GFP Mapping Over OTN
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for distributing timing between Ethernet switched networks and optical transport networks lack phase stability and frequency accuracy, making them unsuitable for synchronous Ethernet applications, particularly with 10GBASE-R clients, as they result in asynchronous timing sources and require additional circuitry and complex network management.
Innovation Solution
An interworking device with a client GFP/OTN mapping block and a hybrid synchronous equipment timing source that recovers a reference timing signal from one network and transforms it to a phase and frequency-locked signal for the other network, ensuring synchronized timing across both networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If 10GBASE-R clients are over-clocked to produce a pseudo-OTU2 signal, then the data rate is improved to match OTN requirements, but device complexity increases due to additional circuitry and protocol layers
Solution Approach 1:
The patent changes the clocking parameter from over-clocking (11.09557 Gb/s) to synchronous clocking at the standard OTU2 rate (10.709225 Gb/s). This is achieved by using a hybrid synchronous equipment timing source that phase-locks the Ethernet clock to the OTN clock, eliminating the need for over-clocking circuitry while maintaining data integrity.
Solution Approach 2:
The patent uses GFP mapping to create a standardized copy of the 10GBASE-R signal structure that fits the OTN framework. By encapsulating Ethernet frames in GFP containers with proper timing recovery mechanisms, the system avoids direct over-clocking and uses standard OTU2 signaling instead.
2Speed
If 10GBASE-R clients are over-clocked to produce a pseudo-OTU2 signal, then the data rate is improved to match OTN requirements, but network management difficulty increases due to potential traffic issues at OTU2 interfaces
Solution Approach 1:
The patent standardizes the operating frequency parameter to the official OTU2 rate of 10.709225 Gb/s, eliminating pseudo-OTU2e signals. This ensures compatibility with standard OTN equipment and simplifies network management by avoiding interface compatibility issues between different equipment providers.
3Speed
If native Ethernet traffic is mapped using framed GFP mapping, then the standard OTU2 line rate is maintained, but timing stability deteriorates due to clock accuracy mismatch between Ethernet (±100 ppm) and OTN (±20 ppm)
Solution Approach 1:
The patent implements a feedback mechanism through the hybrid synchronous equipment timing source, which continuously monitors the Ethernet clock and adjusts it to match the OTN clock frequency. This closed-loop timing synchronization ensures that the ±100 ppm Ethernet clock is corrected to meet the ±20 ppm OTN stability requirements while maintaining the standard OTU2 line rate.
Solution Approach 2:
The patent introduces a hybrid synchronous equipment timing source as an intermediary between the Ethernet client and the OTN network. This intermediary device performs phase-locking and frequency adjustment, translating the less stable Ethernet timing to the more stable OTN timing domain without changing the standard OTU2 line rate.
4Device complexity
If asynchronous timing sources are used in Ethernet to OTN mapping, then device complexity increases with additional circuitry, but phase stability is maintained poorly
Solution Approach 1:
The patent uses the hybrid synchronous equipment timing source as a mediator that actively synchronizes the Ethernet timing domain with the OTN timing domain. This intermediary performs phase-locking to ensure phase stability while using standard GFP mapping circuitry, avoiding the need for complex asynchronous timing handling mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution maintains phase stability and frequency accuracy, meeting ITU G.8261 requirements, and simplifies network management by synchronizing the timing sources, enabling reliable transport of 10GBASE-R signals over OTN networks while reducing the need for additional circuitry and potential traffic issues.
Implementation Method 1
transforms the first reference timing signal to a second reference timing signal that is phase and frequency locked to the first reference timing signal
Implementation Method 2
transforms the first reference timing signal to a second reference timing signal that is phase and frequency locked to the first reference timing signal
Data Source
AI summary
An interworking device, method and system distribute reference timing between at least two communication networks. The interworking device includes a first communication interface operable to communicate with a first communication network operating using a first communication protocol and a second communication interface operable to communicate with a second communication network operating using a second communication protocol. The interworking device also includes a client generic framing procedure/optical transport network (“GFP/OTN”) mapping block in communication with the first communication interface and the second communication interface. The client GFP/OTN mapping block recovers a first reference timing signal from data received from the first communication network. At least one hybrid synchronous equipment timing source transforms the first reference timing signal into a second reference timing signal that is phase and frequency locked to the first reference timing signal, and supplies the second reference timing signal to the client GFP/OTN mapping block to clock the second communication network.