N+N DSL Link Protection Switching for Transmission Integrity
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Solution Overview
Problem
Digital subscriber line (DSL) communication networks face challenges in maintaining data transmission integrity when DSL links fail, particularly in M-pair mode, where the reduction in available timeslots affects elastic services like Ethernet, which can adapt to varying bandwidth, while non-elastic services like Nx64k or E1 require fixed timeslots, leading to transmission failures.
Innovation Solution
The implementation of a communication system with two groups of DSL links, where one group acts as a backup to the active group, allowing for seamless switching and remapping of PCM timeslots across remaining DSL pairs in case of failures, ensuring continuous data transmission by interleaving timeslots across multiple DSL pairs and using protocols like 802.3x Ethernet flow control to manage bandwidth adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If M-pair mode is used to reduce the number of active DSL links, then device complexity is reduced, but reliability deteriorates because non-elastic services fail when timeslots are reduced
Solution Approach 1:
The system divides DSL links into two distinct groups: a first group of N active DSL links for primary data transmission and a second group of N backup DSL links for protection. This segmentation allows the system to maintain reliability by having dedicated backup links while operating with reduced complexity using only the active group under normal conditions.
Solution Approach 2:
The system prepares backup DSL links in advance before any failure occurs. When a failure is detected in the active group, the backup group is immediately activated to cushion against the loss, ensuring continuous data transmission without interruption. This prior cushioning mechanism protects non-elastic services from timeslot reductions by providing alternative transmission paths.
2Reliability
If backup DSL links are added to provide N+N protection, then reliability is improved, but device complexity increases due to additional links and switching mechanisms
Solution Approach 1:
The system merges the backup switching functionality into the existing DSL controller architecture, combining the control of active and backup links within a single node. This integration reduces operational complexity by eliminating the need for separate backup control mechanisms while maintaining the reliability benefits of N+N protection.
Solution Approach 2:
The system implements dynamic switching between active and backup DSL links based on real-time failure detection. The controller automatically transitions from the first group to the second group when failures occur, providing adaptive protection that maintains reliability without requiring static, complex switching configurations.
3Loss of time
If automatic switching between active and backup groups is implemented, then response time to failures is reduced, but device complexity increases due to failure detection and switching control mechanisms
Solution Approach 1:
The DSL controller performs self-diagnosis and automatic failure detection without requiring external intervention. When a failure is detected in the active DSL links, the controller autonomously switches to the backup group, reducing failure response time while minimizing the complexity of external control mechanisms through self-service operation.
Data Source
AI summary
A communication system comprises a plurality of DSL links comprising a first group and second group of DSL links, each group comprising more than one DSL link. The communication system also comprises a first node and a second node each having at least one application port and a plurality of DSL ports. Each DSL port is coupled to a respective one of the DSL links such that the first and second nodes are communicatively coupled via the DSL links. Each of the first and second nodes is configured to interleave a first copy of data received over the respective application port across the first group and to interleave a second copy of the data across the second group. When a failure is detected on a DSL link in the first group, each of the first and second nodes is configured to switch from the first group to the second group.