Parallel Link Substitution in Circuit Restoration
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Solution Overview
Problem
Circuit-based communication networks face significant delays in restoring circuits during failures due to insufficient network resources and the need to minimize crankbacks, which increase service outages and restoration time, especially when parallel links with diverse routes are not efficiently utilized.
Innovation Solution
Switches are enabled to substitute parallel links for specified links in a circuit path during restoration, but not during provisioning, allowing for faster restoration paths while preserving diversity by using flags or wildcard characters in setup messages to indicate permitted substitutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If parallel links are substituted during circuit restoration, then restoration time is reduced and crankbacks are minimized, but diversity requirements may be compromised
Solution Approach 1:
The patent applies dynamics by making the link substitution capability conditional rather than static. The system dynamically adjusts whether substitution is allowed based on the circuit state: restoration circuits are permitted to substitute parallel links to minimize restoration time, while new service circuits must maintain diversity requirements. This is implemented through different flag settings in setup messages depending on whether the circuit is being restored or newly provisioned.
2Device complexity
If parallel links are grouped into a single link, then information association is simplified, but diversity information is compromised
Solution Approach 1:
The patent applies segmentation by dividing links into parallel individual links rather than grouping them into a single aggregate link. Each parallel link maintains its own identity, bandwidth characteristics, and diversity information. This segmentation allows the system to preserve diversity information while still providing the flexibility to substitute between parallel links during restoration, resolving the contradiction between simplified information association and diversity preservation.
3Loss of time
If crankbacks are minimized during restoration, then service outage time is reduced, but network resource utilization may be insufficient
Solution Approach 1:
The patent applies preliminary action by pre-establishing multiple parallel links with diverse routes before failures occur. During restoration, the system can immediately substitute an alternative parallel link if resources are available, avoiding the need for crankbacks. The setup messages include flags that indicate whether substitution is permitted, allowing switches to make immediate decisions without waiting for resource availability feedback, thus reducing service outage time while efficiently utilizing pre-provisioned network resources.
Data Source
AI summary
A method and system for provisioning circuits on multiple parallel links with a single setup message is disclosed. A setup message specifying links in a circuit path is transmitted to switches along the circuit path. If a switch determines that a link specified in the setup message has insufficient bandwidth for the circuit, the switch substitutes a parallel link having sufficient bandwidth for the specified link in the circuit path. The setup message can indicate whether substitution for a link is permitted. This can be used to prevent substitution for links when provisioning service routes for new circuits in order to maintain diversity requirements, while allowing substitution for links when provisioning restoration routes for failed circuits in order to reduce restoration time.