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Asynchronous Byzantine fault tolerance (ABFT)

When a decentralized network is Byzantine Fault Tolerance (BFT), it means that the honest members, or Nodes, of a Node Network can be guaranteed to agree on the timing and order (consensus) of a set of Transactions. Regardless, whether there are some Nodes maliciously trying to prevent that consensus — even if as many as 1/3 of nodes are trying to negatively affect consensus by delaying transactions or otherwise corrupting things. This is the “Fault Tolerance” of the network, meaning how many nodes can the network tolerate acting maliciously, but still come to an honest consensus.

The asynchronous property of BFT overcomes a challenge of fault tolerance, which is that of timing. Many forms of BFT assume there is a maximum threshold of message latency when coming to a consensus. An ABFT network eliminates this assumption and allows for some messages to be lost or indefinitely delayed.

An ABFT network allows for messages to be lost or indefinitely delayed and assumes only that at some point an honest node’s messages will eventually get through. It is much more challenging for an honest node to assess whether another node is not following the rules, if that node’s messages can be indeterminately delayed, but this scenario much better reflects that of network reliability in the real world.

Source: https://hedera.com/learning/what-is-asynchronous-byzantine-fault-tolerance-abft