Autonomous System Backup Path Construction for Inter-AS Link Failures

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Solution Overview

Problem

Current methods for reducing BGP convergence time in case of inter-domain failures, such as link failures between autonomous systems, still result in unacceptably long recovery times despite efforts to minimize BGP messages and implement source routing techniques.

Innovation Solution

A method for constructing a backup path in an autonomous system by pre-computing alternate inter-AS paths and establishing protection tunnels between edge routers, allowing for immediate rerouting of packets around failed links without requiring cooperation between different autonomous systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If BGP messages are minimized and source routing techniques are implemented, then BGP convergence time is reduced, but recovery time remains unacceptably long

Engineering Contradiction:

ImproveBGP convergence timeVSAvoidrecovery time

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent pre-computes backup paths and establishes protection tunnels before failures occur. Edge routers maintain pre-calculated alternate routes to downstream ASes, so when a failure happens, traffic can be immediately redirected without waiting for BGP convergence. This preliminary preparation resolves the contradiction by making recovery time independent of BGP message exchange delays.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces protection tunnels as intermediary paths between source and destination. These tunnels act as pre-established backup channels that can carry traffic immediately when primary paths fail, bypassing the need for slow BGP route advertisement and convergence processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If protection tunnels are established between edge routers, then rerouting speed is improved, but device complexity increases

Engineering Contradiction:

Improvererouting speedVSAvoiddevice complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent implements protection tunnels locally at each edge router rather than requiring system-wide coordination. Each edge router independently computes and maintains backup paths to its own downstream ASes, reducing the complexity burden to individual routers rather than the entire BGP system.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Edge routers autonomously compute their own protection paths and establish local protection tunnels without requiring cooperation or coordination from other autonomous systems. This self-service approach simplifies implementation by making each router independently capable of fast rerouting.

Inventive Principle:

Principle #25Self-service

3Loss of time

If alternate inter-AS paths are pre-computed, then recovery time is reduced, but memory requirements increase

Engineering Contradiction:

Improverecovery timeVSAvoidmemory requirements

Core Design Contradiction:

Loss of timeVSQuantity of substance

Solution Approach 1:

The patent extracts and stores only the essential backup path information at each edge router - specifically, pre-computed alternate routes to downstream ASes and associated protection tunnel parameters. This selective extraction minimizes memory requirements while maintaining the ability to perform fast rerouting.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS7864669B2Method of constructing a backup path in an autonomous system

Publication Date: 2011.01.04 CISCO TECHNOLOGY INC

AI summary

A method of constructing a backup path in an autonomous system (AS) for failure of an inter-AS link is described. The method comprises identifying an alternate inter-AS path and constructing a tunnel to an end point on the alternate path.