BFD Session Link Failure Detection EVPN Multihoming

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Solution Overview

Problem

In Ethernet virtual private network (EVPN) multihoming topologies, the time taken for a backup designated forwarder to become the designated forwarder after a link failure is too long, leading to network traffic disruption and loss, as it currently takes around ten to twenty seconds.

Innovation Solution

Implementing a bidirectional forwarding detection (BFD) session between network devices to quickly detect link failures and trigger a BFD message that causes the backup designated forwarder to immediately become the new designated forwarder, leveraging data plane mechanisms independent of control plane load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional EVPN multihoming mechanism is used, then network redundancy is provided, but the time for backup designated forwarder to become designated forwarder is too long (10-20 seconds), causing network traffic disruption and loss

Engineering Contradiction:

Improvenetwork redundancyVSAvoidrole switching time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent establishes BFD sessions between designated forwarder and backup designated forwarder in advance, so that when a link failure occurs, the backup can immediately detect the failure and switch roles without waiting for traditional EVPN detection mechanisms, thus reducing the 10-20 second delay

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the designated forwarder continuously monitors link status and immediately notifies the backup designated forwarder of link failures through BFD messages, enabling the backup to rapidly assume the designated forwarder role and minimize traffic loss

Inventive Principle:

Principle #23Feedback

2Measurement precision

If traditional link failure detection mechanism is used, then link failures are detected, but the detection time is too long leading to traffic loss

Engineering Contradiction:

Improvelink failure detection accuracyVSAvoiddetection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the traditional control-plane-based link failure detection mechanism with a data-plane-based BFD mechanism, which uses dedicated detection packets sent through the forwarding path to detect link failures, achieving faster and more accurate detection independent of control plane load

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10771317B1Reducing traffic loss during link failure in an ethernet virtual private network multihoming topology

Publication Date: 2020.09.08 JUNIPER NETWORKS INC

AI summary

A first network device permits a bidirectional forwarding detection (BFD) session with a second network device. The first network device is a designated forwarder for a third network device, a first link is provided between the first network device and the third network device, the second network device is a backup designated forwarder for the third network device, a second link is provided between the second network device and the third network device. The first network device detects a link failure associated with the first link between the first network device and the third network device, and provides, via the BFD session, a BFD message to the second network device. The BFD message includes an indication of the link failure, and the BFD message is to cause the second network device to be a new designated forwarder for the third network device.