Hardware Path Management for Rapid SONET/SDH Switching
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Solution Overview
Problem
In packet networks, path switching from a work path to a protection path is typically performed through software processing, leading to prolonged switching times, especially when multiple logical paths are involved, which is undesirable for ensuring rapid network reliability, particularly in SONET/SDH networks where switching within 50 milliseconds is required.
Innovation Solution
The implementation of transmission equipment with a hardware-based path management system that includes interface units and a switch to rapidly determine and switch frames based on path information, allowing for simultaneous monitoring and switching of multiple logical paths without CPU intervention, utilizing a path management frame to transmit path state information across the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If path switching is performed through software processing, then the system is easier to implement and maintain, but the switching time becomes excessively long
Solution Approach 1:
The patent replaces the software-based path switching mechanism with a hardware-based mechanism. Specifically, it introduces a path management frame transmission unit that operates in hardware to monitor path states and trigger switching actions, eliminating the need for CPU intervention in the switching decision process. This hardware substitution directly addresses the contradiction by maintaining implementation simplicity through standardized protocols while achieving rapid switching times through dedicated hardware circuits.
Solution Approach 2:
The patent extracts the path switching function from the general-purpose CPU software processing and creates a dedicated hardware subsystem. The path management frame transmission unit and path state determination unit are separated as independent hardware components that operate autonomously from the main CPU. This extraction allows the switching function to operate independently with minimal latency while the CPU continues to handle other management tasks.
2Adaptability or versatility
If multiple logical paths are monitored and switched sequentially through software, then all paths can be managed, but the total switching time increases significantly
Solution Approach 1:
The patent segments the path monitoring and switching function into individual hardware units, each capable of independently monitoring a specific logical path. Instead of one sequential software loop checking all paths, multiple parallel hardware monitoring units simultaneously track their respective paths. When a failure is detected on any path, the corresponding hardware unit immediately triggers switching for that specific path without waiting for other paths to be checked. This segmentation enables simultaneous monitoring and switching of multiple logical paths, directly resolving the time delay issue while maintaining comprehensive path management capability.
3Extent of automation
If path switching requires CPU intervention for each path, then centralized control is maintained, but the switching speed decreases
Solution Approach 1:
The patent implements preliminary action by pre-configuring path management frames that contain switching instructions and path state information. These frames are prepared and transmitted in advance through the hardware transmission unit, so that when a failure occurs, the switching decision and instruction are already in place and can be executed immediately. The hardware unit autonomously processes these pre-prepared frames without requiring real-time CPU intervention, achieving both rapid switching and centralized control through the pre-configured framework.
Solution Approach 2:
The patent introduces path management frames as an intermediary mechanism between the centralized control system and the distributed path monitoring units. These frames carry path state information and switching instructions, enabling autonomous hardware units to execute switching decisions while still being governed by centralized path management policies. The frames act as a mediator that translates centralized control intent into localized hardware actions, maintaining control hierarchy while enabling fast autonomous execution.
Data Source
AI summary
Transmission equipment includes: a first interface unit configured to receive a frame; and a second interface unit configured to transmit the received frame received by the first interface unit. The second interface unit includes a transmission circuit configured to transmit path information that represents a state of a logical path pair including a work path and a protection path provided for the received frame to the first interface unit. The first interface unit includes a destination determination circuit configured to determine a destination of the received frame based on the state of the logical path pair represented by the path information received from the second interface unit.