Transport Network Path Switch-Back During Simultaneous Link Restoration
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Solution Overview
Problem
The G.841 protocol fails to enable switch-back to a working path from a protection path when links in both directions of a working path between nodes in a transport network are restored simultaneously, leading to incomplete restoration of network functionality.
Innovation Solution
A method and apparatus where a local node determines simultaneous restoration of failed links by identifying Reverse Request (RR) protection switching requests, enters a Wait To Restore (WTR) state, and switches the signal back to the working path when the WTR state ends, ensuring proper switch-back even in scenarios of simultaneous link restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the G.841 protocol is used for protection switching, then protection switching can be achieved, but switch-back cannot be performed when links in both directions are restored simultaneously
Solution Approach 1:
The patent applies preliminary action by introducing a preliminary judgment step before executing switch-back operations. When a node receives an RR request, it first judges whether the local working path is normal. This preliminary check prevents the switch-back failure that occurs in simultaneous restoration scenarios, as the node can identify that both directions are restored and avoid erroneous switch-back attempts.
2Productivity
If priority comparison of protection switching requests is performed according to G.841, then protection switching requests are processed, but RR requests are excluded from comparison causing switch-back failure
Solution Approach 1:
The patent applies inversion by reversing the traditional approach to handling RR requests. Instead of excluding RR requests from priority comparison as per G.841, the patent specifically includes RR requests in the priority comparison process. When a node receives an RR request, it compares the priority of the RR request with local protection switching requests, and this inverted approach enables successful switch-back operations by properly recognizing restoration conditions.
3Reliability
If nodes respond to remote protection switching requests with higher priority, then protection switching is executed, but simultaneous response to RR requests prevents proper switch-back
Solution Approach 1:
The patent applies feedback by introducing a local working path status check as a feedback mechanism before executing switch-back. When a node receives an RR request and determines through priority comparison that switch-back should occur, it first checks whether the local working path is actually normal. This feedback loop ensures that switch-back is only executed when appropriate, preventing the operational complexity and failures associated with simultaneous restoration scenarios.
Data Source
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AI summary
The disclosure discloses a path switch-back method and apparatus in a transport network, belongs to the field of communications, and is used for avoiding the problem that signals can not be switched back to a working path from a protection path when the links in two directions of the working path between nodes in the transport network are restored from fault simultaneously. The path switch-back method in a transport network provided by the disclosure includes: a local node determines two failed links on the working path between an opposite node and itself are restored to normal simultaneously (S101); the local node enters a Wait To Restore (WTR) state (S102); and the local node switches signals back to the working path when the WTR state ends (S103). The disclosure is used for realizing that signals are switched back to the working path from the protection path when the links in two directions of the working path between nodes in the transport network are restored from fault simultaneously.