Logical Path Remapping for Link-Down Multipath Routing

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Solution Overview

Problem

In multipath routing, data loss occurs when a physical link goes down due to the delay in recalculating forwarding tables, causing packets to be routed to unavailable links until the update is completed.

Innovation Solution

Implementing logical path remapping in forwarding tables, where logical paths are associated with physical links, allowing immediate rerouting to available links when a physical link becomes unavailable, thus continuing packet delivery without packet loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If forwarding tables are recalculated when a physical link goes down, then routing accuracy is improved, but packet loss occurs during the recalculation delay

Engineering Contradiction:

Improverouting accuracyVSAvoidrecalculation delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent pre-calculates and stores alternative paths in the forwarding table before any link failure occurs. When a link goes down, the system immediately switches to a pre-computed alternative path without needing to recalculate routing, thus eliminating packet loss during recalculation delay while maintaining routing accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system prepares backup routing paths in advance as a cushion against potential link failures. These pre-prepared alternative paths are stored in the forwarding table and can be immediately activated when a link failure occurs, cushioning against the harmful effect of packet loss during recalculation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If forwarding tables are updated immediately when a link down event occurs, then packet loss is reduced, but forwarding plane consistency is compromised

Engineering Contradiction:

Improvepacket delivery reliabilityVSAvoidforwarding table consistency

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent segments the forwarding table into multiple independent path entries (primary path and alternative paths) for each destination. When a link fails, only the affected path entry is updated while other entries remain unchanged, maintaining forwarding plane consistency while enabling immediate packet rerouting

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system introduces an intermediary mechanism that decouples the control plane routing calculation from the forwarding plane packet switching. The forwarding table acts as an intermediary buffer that can be updated independently, allowing the forwarding plane to maintain consistency while the control plane performs routing calculations

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If multiple physical links are monitored for link down events, then network reliability is improved, but system complexity increases

Engineering Contradiction:

Improvenetwork availabilityVSAvoidlink monitoring complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements a universal link monitoring mechanism that can monitor multiple physical links using the same hardware and software infrastructure. The forwarding table structure is designed to handle multiple paths uniformly, allowing the system to monitor and manage numerous links without proportionally increasing complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system changes the state parameter of path entries in the forwarding table from static to dynamic, allowing paths to be activated or deactivated based on link status. This parameter-based management approach simplifies the monitoring of multiple links by reducing it to simple state transitions in the forwarding table

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12506684B2Link down event management with logical path remapping

Publication Date: 2025.12.23 ARISTA NETWORKS INC

AI summary

A networking device uses multipath routing for paths designated as logical paths having associated physical interfaces, such that link down events are processed by remapping related logical paths to other physical links. The networking device includes a forwarding table that is generated according to a multipath algorithm, such as an equal-cost multipath (ECMP) algorithm. The forwarding table specifies different logical paths mapped to physical links, which may include different physical interfaces and related processing information. Packets are processed by selecting a logical path and applying the mapped profile information and/or physical egress interface of the selected logical path. When a link down monitor detects a link down event, a logical path mapped to the now-unavailable physical link is remapped to another physical link, enabling packets to be selected for the affected logical path and successfully processed before re-calculation of forwarding table to account for the unavailable physical link.