Selective LSP Eviction for MPLS Link Oversubscription
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Solution Overview
Problem
Managing MPLS traffic over bundled links is challenging, particularly when these links become oversubscribed, leading to bandwidth issues and potential traffic loss, as existing methods often require all ingress network devices to reroute LSPs, resulting in underutilization of bandwidth and prolonged traffic disruptions.
Innovation Solution
A transit network device selectively evicts a subset of LSPs from a shared resource by sending Path Error messages to ingress routers, allowing for rerouting while keeping other LSPs operational, using various algorithms to determine which LSPs to evict and notify only the affected ingress routers, thus avoiding complete rerouting of all LSPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all ingress network devices are required to reroute LSPs when a bundled link becomes oversubscribed, then bandwidth management is enforced, but network utilization decreases and traffic disruptions are prolonged
Solution Approach 1:
The patent segments the set of LSPs traversing the oversubscribed bundled link into two subsets: those that are evicted and require rerouting, and those that continue to operate without interruption. This selective segmentation allows partial maintenance of network services while enforcing bandwidth management, thereby resolving the contradiction between reliability and productivity.
Solution Approach 2:
Instead of requiring all ingress network devices to reroute all LSPs (excessive action), the patent applies partial action by selectively evicting only a subset of LSPs from the oversubscribed bundled link. This partial eviction maintains sufficient bandwidth management while preserving network utilization and minimizing traffic disruptions.
2Reliability
If all LSPs are rerouted when a bundled link is oversubscribed, then bandwidth constraints are satisfied, but traffic loss increases and rerouting time is extended
Solution Approach 1:
The patent divides LSPs into two groups: those selected for eviction and those allowed to continue. This segmentation enables bandwidth constraint satisfaction for the evicted subset while avoiding unnecessary rerouting time for the remaining subset, thereby reducing overall rerouting duration.
Solution Approach 2:
The transit network device performs preliminary identification and selection of which LSPs to evict before actual rerouting begins. By pre-determining the subset of LSPs that need rerouting based on current network state and bandwidth constraints, the system minimizes the time required for the rerouting process.
3Productivity
If selective rerouting of a subset of LSPs is implemented, then network utilization improves and traffic loss is reduced, but complexity in selecting which LSPs to evict increases
Solution Approach 1:
The patent employs algorithms that evaluate LSPs based on multiple parameters such as bandwidth requirements, priority levels, and current network state. By changing and comparing these parameters, the system intelligently selects which LSPs to evict, achieving selective rerouting that improves network utilization while managing complexity through systematic parameter evaluation.
4Reliability
If complete rerouting of all LSPs is performed, then bandwidth management is enforced, but bandwidth wastage occurs due to underutilization
Solution Approach 1:
The patent segments LSPs into evicted and non-evicted subsets, allowing continued utilization of the bundled link by LSPs that do not require rerouting. This segmentation prevents bandwidth wastage by maintaining active LSPs that can still utilize available bandwidth, while simultaneously enforcing bandwidth management on the evicted subset.
Solution Approach 2:
The patent ensures continuity of useful action by allowing non-evicted LSPs to continue traversing the bundled link without interruption. This maintains bandwidth utilization and prevents wastage, while the evicted LSPs are handled through selective rerouting to enforce bandwidth constraints.
Data Source
AI summary
In one example, a network device includes a hardware-based processor, and a Resource Reservation Protocol with Traffic Engineering extensions (RSVP-TE) module executing on the hardware-based processor that establishes a plurality of label switched paths (LSPs) having the network device as a common transit network device. The network device presents a plurality of options for selection, which each specify a different algorithm for selecting LSPs to evict from the link. In response to detecting an over-subscription condition on a link along the plurality of LSPs, the RSVP-TE module selects a subset of the plurality of LSPs to evict from the link, and the RSVP-TE module outputs an error message to one or more ingress network devices associated with the selected subset of LSPs without outputting an error message to the ingress network devices associated with those LSPs not selected for eviction.