MPLS LSP State Cleanup via Remote PathTear Signaling
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Solution Overview
Problem
The existing Multi-Protocol Label Switching (MPLS) protocols, such as RSVP-TE, face challenges in scaling to manage a high volume of Label Switched Paths (LSPs) due to the high rate of RSVP protocol messages, leading to issues like stale state information buildup and inefficient handling of link or node failures.
Innovation Solution
The proposed solution extends the refresh interval of MPLS protocol messages and introduces modifications to enable point of local repair routers to signal link or node protection to merge point routers, allowing selective cleanup of LSP states and conditional deletion of stale information, while maintaining backwards compatibility with non-modified routers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the refresh interval of MPLS protocol messages is extended to reduce message exchange volume, then scalability is improved, but stale state information accumulates on network devices
Solution Approach 1:
The patent applies preliminary action by having the Point of Local Repair (PLR) router proactively send a remote PathTear message to the Merge Point (MP) router before the LSP state times out. This preemptive teardown notification allows the MP router to clean up stale state information immediately upon receiving the message, rather than waiting for the refresh interval to expire. This resolves the contradiction by maintaining long refresh intervals for scalability while preventing stale state accumulation through proactive cleanup signaling.
2Loss of energy
If the refresh interval is extended to reduce the number of protocol messages, then message overhead is reduced, but the handling of link or node failures becomes less efficient
Solution Approach 1:
The patent enables efficient failure handling by allowing the PLR router to immediately detect link or node failures and send a remote PathTear message to the MP router. This triggers immediate LSP state teardown at the MP router, bypassing the need to wait for refresh interval expiration. This resolves the contradiction by maintaining long refresh intervals for reduced overhead while enabling rapid failure response through on-demand teardown signaling.
Solution Approach 2:
The patent implements feedback mechanisms where the PLR router monitors the status of LSPs and provides real-time feedback to the MP router through PathTear messages when failures are detected. This feedback loop allows the network to dynamically adjust state maintenance based on actual network conditions, resolving the contradiction between reduced message overhead and efficient failure handling.
3Productivity
If MPLS protocols are modified to enable selective cleanup of LSP states, then scalability is improved, but backwards compatibility with non-modified routers is lost
Solution Approach 1:
The patent applies universality by designing the remote PathTear message mechanism to work within the existing RSVP-TE protocol framework. The modified routers can send and process PathTear messages using standard protocol procedures, while non-modified routers continue to operate with default behavior. This allows the system to support both modified and non-modified routers simultaneously, maintaining backwards compatibility while enabling scalability improvements for modified devices.
Data Source
AI summary
In one example, techniques of this disclosure may enable a point of local repair (PLR) network device to signal availability of link protection or node protection to a merge point (MP) network device and enable a network device to actively determine whether or not it is a merge point router. Based on whether or not the network device determines it is a MP, the network device may selectively clean up LSP states when there is an upstream link or node failure. The RSVP-TE protocol may be extended to enable a network device to send a tear down message to a downstream router, which may enable the downstream router to conditionally delete locale LSP state information. In some instances, a PLR network device may directly send a tear down message to a MP network device even though the PLR network device may not have a working bypass LSP.