LACP Fallback Coordination Using Designated Forwarder Election
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Solution Overview
Problem
In Ethernet Virtual Private Network (EVPN) multihoming scenarios, the Link Aggregation Control Protocol (LACP) fallback mechanism can cause traffic drops or blackholing due to the lack of coordination between network devices, especially when establishing Link Aggregation Groups (LAGs) without complete configuration, leading to inconsistent link status and management challenges.
Innovation Solution
A designated forwarder election mechanism is implemented to determine a single designated forwarder within an ES LAG through a deterministic procedure using router IDs, ensuring only one switch maintains an active link while others disable their links, thereby stabilizing traffic routing before full configuration is complete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LACP fallback mechanism is used to establish LAGs without complete configuration, then connectivity can be established quickly, but traffic may be dropped or blackholed due to lack of coordination between network devices
Solution Approach 1:
The patent applies preliminary action by having network devices independently determine their role (designated forwarder or backup) before full LACP configuration is complete. Each device uses pre-established criteria (such as router ID comparison) to decide whether to activate its link, ensuring coordinated behavior from the outset rather than attempting coordination after traffic issues arise.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a designated forwarder election process that mediates between multiple network devices. This intermediary role assignment system coordinates link activation decisions among devices, preventing traffic blackholing by ensuring only the designated forwarder actively forwards traffic initially, while others remain in backup state.
2Adaptability or versatility
If multiple network devices independently manage LAG links, then configuration flexibility is improved, but inconsistent link status and traffic routing occur
Solution Approach 1:
The patent applies local quality by allowing each network device to independently determine its own role in the LAG based on local criteria (such as its router ID), while this local determination collectively ensures global consistency. Each device makes a localized decision about whether to activate its link based on the predetermined designated forwarder status, resulting in coordinated and consistent link status across the network.
3Productivity
If LACP fallback is used before complete configuration, then initial connectivity is enabled, but operational complexity and management burden increase
Solution Approach 1:
The patent applies self-service by enabling network devices to autonomously determine their own role in the LAG formation process without requiring manual configuration or complex coordination protocols. Each device independently evaluates its router ID and determines whether it should be the designated forwarder or backup, automatically managing the link activation decisions and reducing operational management complexity.
Data Source
AI summary
Systems and methods for allowing network devices in an Ethernet Segment(ES) Link Aggregation Group (LAG) to independently perform a deterministic designated forwarder determination. Only one of the devices in the LAG will determine that it is the designated forwarder for the LAG, while the remaining devices will determine that they are not the designated forwarder for the LAG. The device that determines it is the designated forwarder may enable (or maintain) a link to a particular network device while all other devices in the LAG that make the determination they are not the designated forwarder may disable a link to that particular network device.