Failure detectors Sample Clauses

Failure detectors. There is a connection between accountability and failure de- tectors. A failure detector is designed to provide each process in the system with some advice, typically a list of processes that are faulty in some manner. However, failure detectors tend to have a different set of goals. They are used during an execution to help make progress, while accountability is usu- ally about what can be determined post hoc after a problem occurs. They provide advice to a process, rather than proofs of culpability that can be shared. Most of the work in this area has focused on detecting crash failures (see, e.g., [12]). There has been some interesting work extending this idea to detecting Byzantine failures [18, 19, 23, 28]. Malkhi and Xxxxxx [28] introduced the concept of an unreliable Byzan- tine failure detector that could detect quiet processes, i.e., those that did not send a message when they were supposed to. They showed that this was sufficient to solve Byzantine Agreement. Kihlstrom, Moser, and Xxxxxxx-Xxxxx [23] continue this direction, considering failures of both omission and commis- sion. Of note, they define the idea of a mutant message, i.e., a message that was received by multiple processes and claimed to be identical (e.g., had the same header), but in fact was not. The Polygraph Protocol is designed so that only malicious users sending a mutant message can cause disagreement. In fact, the main task of accountability in this paper is iden- tifying processes that were supposed to broadcast a single message to everyone and instead sent different messages to different processes. / / ≤ / Maziéres and Shasha propose SUNDR [29] that detects Byzantine behaviors in a network file system if all clients are honest and can communicate directly. Polygraph clients request multiple signatures from servers so that they do not need to be honest. Li and Maziéres [27] improves on SUNDR with BFT2F, a weakly consistent protocol when the number of failures is 𝑛 3 𝑡 < 2𝑛 3 and its BFTx variant that xxxxx with more than 2𝑛 3 failures but does not guarantee liveness even with less than 𝑡 failures.