Due to a ransomware attack, the wiki was reverted to a July 2022 version. . We apologize for the lack of a more recent valid backup.
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- An anti-entropy mechanism based on Gossip protocol, which works as follows: at fixed intervals (usually 3-5 seconds), a controller randomly picks another controller and they both synchronize their respective topology views. If one controller is aware of more recent information that the other controller does not have, they exchange that information and at the end of that interaction, their respectively respective topology views are mutually consistent. Most of the time the anti-entropy interaction will be uneventful, as each controller already knows about every event that happened in the network. But when a controller state drifts slightly, this mechanism quickly detects that and brings the controllers back in sync. This approach has the added benefit of quickly synchronizing a newly-joining controller with the rest. The first anti-entropy interaction that a newly joining controller has with an existing controller will bring it up to speed, without the need for a separate backup/discovery mechanism.
- For detecting and recovering from complete loss of topology updates, each controller periodically probes the devices for which it is the master. If it detects that the device state is different from the information it has, it promptly updates its local topology state and replicates that update to all other controllers in the cluster.
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