Caching Secondary UMH Path for MoFRR Traffic Loss Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In multicast routing protocols like PIM and mLDP, restoration of a link or node on the path to the multicast source can result in traffic loss due to the normal operation of these protocols, which defeats the purpose of Multicast Only Fast Re-Route (MoFRR) in minimizing convergence times and avoiding excessive traffic losses.

Innovation Solution

A router is configured to cache the secondary Upstream Multicast Hop (UMH) path for a predetermined period and continue forwarding traffic over this path until traffic from the primary path is restored, thereby minimizing data loss during link or node failures and restorations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If normal PIM or mLDP functions are used when a link or node is restored, then the routing protocol operates normally, but traffic loss occurs

Engineering Contradiction:

Improvetraffic continuityVSAvoidtraffic loss

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent applies preliminary action by caching the secondary UMH path information in advance and maintaining it in the forwarding plane during a predetermined hold time period. This ensures that when the primary path is restored, the secondary path is already prepared and can be immediately switched to, preventing traffic loss during the transition.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by maintaining the cached secondary UMH path in the forwarding plane during the hold time period. This allows the system to continue forwarding traffic through the secondary path without interruption while waiting for the primary path to fully stabilize, eliminating traffic loss during restoration.

Inventive Principle:

Principle #20Continuity of useful action

2Reliability

If the secondary UMH path is cached for a predetermined period, then traffic loss is avoided during restoration, but the forwarding plane complexity increases

Engineering Contradiction:

Improvetraffic continuityVSAvoidforwarding plane complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies partial action by implementing the caching mechanism only for the secondary UMH path during the hold time period, rather than permanently modifying the forwarding plane. This limited scope reduces the complexity increase while still achieving the traffic continuity goal.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent implements dynamics by making the caching behavior temporary and conditional, governed by the hold time parameter. The forwarding plane dynamically adjusts its behavior based on the restoration state, automatically transitioning from caching the secondary path to normal operation when the hold time expires or the primary path is fully restored.

Inventive Principle:

Principle #15Dynamics

3Loss of time

If MoFRR is implemented with primary and secondary UMH paths, then convergence time is reduced, but traffic loss occurs when the primary path is restored

Engineering Contradiction:

Improveconvergence timeVSAvoidtraffic loss

Core Design Contradiction:

Loss of timeVSLoss of substance

Solution Approach 1:

The patent extends the preliminary action principle by maintaining the cached secondary UMH path information during the hold time period after restoration detection. This ensures that the secondary path remains ready for immediate use, preventing traffic loss during the transition back to the primary path while preserving the fast convergence benefits of MoFRR.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9699073B2System and method for reducing traffic loss while using loop free alternate routes for multicast only fast reroute (MoFRR)

Publication Date: 2017.07.04 ALCATEL LUCENT SA

AI summary

A system, method and apparatus for adapting operation of a router configured to receive commonly sourced traffic via primary and secondary Upstream Multicast Hop (UMH) links, wherein the secondary path is cached for a predetermined period of time to avoid data loss upon restoration of the primary path.