Nested Subnet Overhead Modification to Prevent Simultaneous Switching
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Solution Overview
Problem
In optical transport networks, subnets with protection switching functions in a nesting relationship can mistakenly trigger protection switching in outer subnets, leading to extended service transient interruptions and increased maintenance workload due to simultaneous switching events.
Innovation Solution
An overhead change method is implemented in network elements of embedded optical transport subnets, where a fault detection system temporarily changes the overhead values of TCMn-STAT or PM-STAT signals to prevent triggering protection switching in outer subnets, and reverts the changes after a set time, ensuring only necessary subnets perform protection switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection switching functions are implemented in nested subnets, then network reliability is improved, but simultaneous switching events occur causing extended service transient interruptions
Solution Approach 1:
The patent applies preliminary action by having the inner subnet preemptively modify the TCM overhead before the outer subnet can trigger its protection switching. When a fault is detected in the inner subnet, it immediately changes the TCM overhead to a value that prevents the outer subnet from initiating simultaneous protection switching, thereby avoiding extended service interruptions.
Solution Approach 2:
The TCM overhead acts as an intermediary mechanism between the inner and outer subnets. The inner subnet uses this intermediary to communicate its fault state and prevent the outer subnet from triggering unnecessary protection switching, thus coordinating the protection switching actions across nested subnets.
2Reliability
If protection switching is triggered in all nested subnets, then comprehensive protection is achieved, but maintenance workload increases due to simultaneous switching events
Solution Approach 1:
The patent applies local quality by enabling protection switching only where necessary. The inner subnet selectively modifies the TCM overhead to prevent outer subnet switching, ensuring that protection switching occurs only in subnets where actual faults exist, thereby reducing unnecessary maintenance operations while maintaining comprehensive protection.
3Loss of time
If TCM overhead is modified to prevent outer subnet switching, then service transient interruptions are reduced, but the overhead change must be temporary and coordinated
Solution Approach 1:
The patent applies dynamics by implementing a temporary and reversible modification of the TCM overhead. The inner subnet dynamically changes the overhead value to prevent outer subnet switching, and subsequently restores the original value after the protection switching event, allowing the system to adapt to changing network conditions while maintaining coordination.
Data Source
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AI summary
A method and an apparatus for changing an overhead and preventing subnets from switching simultaneously, a network element, and a network are disclosed. The method for changing an overhead includes: detecting that a fault occurs, and the fault triggering an embedded optical transport subnet and an outer subnet thereof to perform protection switching; changing a value of an overhead which will trigger protection switching of the outer subnet in a signal to be transmitted to a downstream network element to a value which will not trigger protection switching of the outer subnet; and cancelling the change after the change lasts for a period of time, wherein the period of time is less than or equal to a set change lasting time. A network element of an embedded subnet in multiple nested subnets performs said method for changing an overhead, and meanwhile sets a protection switching delay trigger time of a network element performing protection switching in the outer subnet to be less than a longest service transient interruption time possibly caused during the protection switching of the embedded subnet, so as to prevent subnets from switching simultaneously and reduce the protection switching delay caused by a fault outside the embedded subnet and in the outer subnet. The present application further provides a corresponding apparatus, network element, and network.