LSP Preemption Avoidance via Bandwidth Thresholding
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Solution Overview
Problem
In computer networks, lower priority Multi-Protocol Label Switching (MPLS) paths often face preemption when higher priority paths require bandwidth, leading to frequent path changes and increased network overhead, which negatively impacts traffic and resource utilization.
Innovation Solution
Implementing techniques that allow routers or path computation elements to selectively avoid bandwidth-constrained links for lower priority paths by adjusting available bandwidth reports, ensuring lower priority paths are only established on links with sufficient threshold bandwidth, without modifying other routers, thereby reducing preemption and network overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lower priority LSPs are established on paths with available bandwidth, then bandwidth utilization is improved, but preemption occurs when higher priority LSPs need the same links
Solution Approach 1:
The patent changes the bandwidth parameter reporting mechanism by introducing a threshold value. Routers report available bandwidth to the IGP, and when bandwidth drops below the threshold, the router is configured to report reduced or zero available bandwidth for lower priority LSPs. This parameter change prevents lower priority LSPs from being established on links that are likely to cause preemption, thus improving path stability while maintaining reasonable bandwidth utilization.
2Reliability
If lower priority LSPs avoid bandwidth-constrained links, then preemption is reduced, but network resource utilization decreases
Solution Approach 1:
The patent applies partial action by selectively applying bandwidth threshold constraints only to lower priority LSPs, not higher priority ones. The threshold mechanism partially restricts bandwidth availability reporting based on priority level, allowing lower priority LSPs to use available bandwidth up to the threshold while avoiding links that would cause preemption. This partial restriction achieves the goal of reducing preemption without completely blocking bandwidth utilization.
3Measurement precision
If routers report accurate available bandwidth, then path selection is optimized, but preemption occurs on constrained links
Solution Approach 1:
The patent applies local quality by differentiating bandwidth reporting based on LSP priority and link conditions. Instead of uniformly reporting all available bandwidth, the system locally adjusts the reported bandwidth availability for lower priority LSPs on links where bandwidth is below the threshold. This localized adjustment maintains accurate reporting for higher priority LSPs and links with sufficient bandwidth, while preventing preemption on constrained links for lower priority traffic.
Data Source
AI summary
Techniques are described for establishing lower priority LSPs on paths determined to be less likely to include bandwidth constrained links. In one example, a router includes a plurality of physical interfaces each having at least one link interconnecting the router as one of a plurality of routers in a network and a processor. The processor is configured to determine whether a link of one of the plurality of physical interfaces is congested based at least in part on an amount of available bandwidth on the link, and, responsive to determining that the link is congested, set a bandwidth subscription for the link, wherein the bandwidth subscription specifies that the amount of available bandwidth on the link for label switched paths having a lower priority is less than the amount of available bandwidth on the link for label switched paths having a higher priority.