BIER Fast Reroute Using Backup BIRT and Loop-Free Alternates

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Solution Overview

Problem

Existing fast reroute mechanisms in Bit Index Explicit Replication (BIER) domains are inefficient and fail to prevent redundant packet transmission, especially when a neighbor bit forwarding router (BFR-NBR) fails without a pre-established routing underlay tunnel.

Innovation Solution

A fast reroute procedure is implemented by copying the bit index routing table (BIRT) to generate a backup BIRT, replacing the neighbor node with backup neighbor nodes, and deriving a backup bit index forwarding table (BIFT) to forward packets using loop-free alternates, reducing redundant packets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing fast reroute mechanisms are used in BIER domains, then routing protection is provided, but redundant packet transmission occurs and routing efficiency deteriorates

Engineering Contradiction:

Improverouting protectionVSAvoidrouting efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent pre-calculates and stores backup next-hop information in the BIRT table before any failure occurs. When a neighbor BFR fails, the network node can immediately switch to the pre-computed backup next-hop without performing real-time calculations, thus eliminating redundant packet transmission while maintaining routing protection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a backup copy of the routing information in the BIRT table that contains alternative next-hop candidates. This copied backup information is maintained separately from the primary routing table, allowing fast switching without affecting the original routing structure and preventing redundant transmissions.

Inventive Principle:

Principle #26Copying

2Adaptability or versatility

If routing underlay tunnel is not pre-established, then network flexibility is maintained, but fast reroute capability is lost

Engineering Contradiction:

Improvenetwork flexibilityVSAvoidfast reroute capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent enables network nodes to autonomously compute backup next-hops using their own BIRT tables and local topology information. Each node independently generates backup routing information without requiring pre-established tunnels or external assistance, thereby maintaining network flexibility while ensuring fast reroute capability.

Inventive Principle:

Principle #25Self-service

3Speed

If backup neighbor nodes are pre-configured, then rerouting speed is improved, but device complexity increases

Engineering Contradiction:

Improvererouting speedVSAvoidtable management complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent merges the backup next-hop information storage directly into the existing BIRT (Bit Index Routing Table) structure. By integrating backup information into the already-deployed BIRT rather than creating separate backup tables, the solution achieves fast rerouting while minimizing additional device complexity and leveraging existing table management mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12603831B2Bit index explicit replication fast reroute

Publication Date: 2026.04.14 HUAWEI TECH CO LTD

AI summary

A method implemented by a network node in a Bit Index Explicit Replication (BIER) domain is used to provide fast reroute protection. The method includes copying a bit index routing table (BIRT) of the network node, changing a neighbor node in the copied BIRT to one of a plurality of backup neighbor nodes to generate a backup BIRT, deriving a backup bit index forwarding table (BIFT) from the backup BIRT, and forwarding a packet in accordance with the backup BIFT when the neighbor node has failed.