Selective LSP Rerouting for Bundled Link Congestion
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Solution Overview
Problem
Managing MPLS traffic over bundled links is challenging due to oversubscription and congestion, which can lead to bandwidth wastage and prolonged traffic loss, especially when a component link fails, as existing technologies lack efficient mechanisms to reroute traffic without notifying ingress routers.
Innovation Solution
A transit router selectively evicts a subset of Traffic Engineering LSPs from a congested or oversubscribed bundled link, rerouting them through a bypass LSP and notifying ingress routers to compute new paths that avoid the affected link, using techniques like soft-FRR and Path Error messages to address congestion and failure scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MPLS traffic is routed over bundled links to improve network utilization, then bandwidth efficiency is improved, but congestion and oversubscription occur leading to traffic loss
Solution Approach 1:
The patent segments the bundled link into individual component links and treats them separately. When congestion is detected on the bundled link, the system identifies and isolates affected component links, allowing selective rerouting of LSPs over alternative paths while maintaining traffic flow over healthy component links. This segmentation enables partial utilization of the bundled link rather than complete failure.
Solution Approach 2:
The patent implements preliminary congestion detection and notification mechanisms. Before traffic loss occurs, the system detects congestion conditions on bundled links and proactively notifies ingress routers. This allows ingress routers to pre-compute alternative paths and reroute traffic before the congestion causes actual traffic loss, preventing the problem rather than reacting to it.
2Reliability
If all LSPs are rerouted when congestion is detected, then traffic loss is prevented, but network stability deteriorates due to widespread rerouting
Solution Approach 1:
The patent applies local quality by treating each LSP independently based on its specific congestion situation. Instead of uniformly rerouting all LSPs when congestion is detected, the system selectively identifies which LSPs are affected by congestion and routes only those through alternative paths. Healthy LSPs continue to use the original bundled link path, maintaining network stability while preventing traffic loss for affected flows.
Solution Approach 2:
The patent changes the routing parameter (path selection) dynamically based on congestion conditions. When congestion is detected on a bundled link, the system modifies the routing parameters for only the affected LSPs, changing their paths to avoid the congested link. This selective parameter change prevents widespread rerouting and maintains overall network stability.
3Adaptability or versatility
If ingress routers are notified of congestion, then selective rerouting is enabled, but signaling overhead increases
Solution Approach 1:
The patent applies partial action by notifying ingress routers only when necessary - specifically when congestion is detected on bundled links that have LSPs traversing them. The system does not continuously notify ingress routers or notify them for every minor condition, but only when actual congestion requires rerouting. This reduces unnecessary signaling overhead while maintaining the adaptability to reroute when needed.
Data Source
AI summary
In one example, a method includes establishing a plurality of label switched paths (LSPs) having a common transit network device other than an ingress network device or an egress network device of any of the plurality of LSPs, and, by the transit network device along the plurality of LSPs, detecting a congestion condition on a link along the plurality of LSPs and coupled to the transit network device. The method also includes, responsive to detecting the congestion condition, and by the transit network device, selecting a subset of the plurality of LSPs to evict from the link, wherein the subset comprises less than all of the plurality of LSPs, and updating a forwarding plane of the transit network device to reroute network traffic received for the selected subset of the plurality of the LSPs for forwarding to a next hop on a bypass LSP that avoids the link.