Common use of Fault Models Clause in Contracts

Fault Models. In synchronous message-based distributed systems, a fault is typically defined as a message that was not transmitted when it was expected or a message that was transmitted but not received or received but not accepted, i.e., deemed invalid by a receiver. Thus, the fault is either associated with the source node of the message, the corresponding link between the source node and the destination node, or the destination node. Consequently, there are two viewpoints, node-centric and link-centric, and thus, there are two ways of modeling faults. In the node-centric model, which we refer to as the node-fault model, the faults are associated with the source node of the message and all fault manifestations between the source and the destination nodes for the messages from that source count as a single fault, which is specially the case when the faults are associated with a Byzantine faulty node [5, 6, 16, 17]. In this model all links are assumed to be good. Miner et al. [16] for instance, model the absence of a link as a link fault and even though both nodes and links failures are considered, they abstractly model link failures as failures of the source node. In the link-centric model, which we refer to as the link-fault model, a fault is associated with the communication means connecting the source node to the destination node. In this model, all nodes are assumed to be good and an invalid message at the receiving node is counted as a single fault for the corresponding input link. Thus, from the global perspective, a Byzantine faulty node manifests as one or more link failures. A link-fault model introduced by ▇▇▇▇▇▇ et al. [18] is called perception-based hybrid fault model, where faults are viewed from the perspective of the receiving nodes. Faults are associated with their input links, and all nodes are assumed to be good. They argued that since F faulty nodes can produce at most F faulty perceptions in any node, the link-fault model is compatible with the traditional node-fault model and so, all existing lower bound and impossibility results remain valid.

Fault Models. In synchronous message-based distributed systems, a fault is typically defined as a message that was not transmitted when it was expected or a message that was transmitted but not received or received but not accepted, i.e., deemed invalid by a receiver. Thus, the fault is either associated with the source node of the message, the corresponding link between the source node and the destination node, or the destination node. Consequently, there are two viewpoints, node-centric and link-centric, and thus, there are two ways of modeling faults. In the node-node- centric model, which we refer to as the node-fault model, the faults are associated with the source node of the message and all fault manifestations between the source and the destination nodes for the messages from that source count as a single fault, which is specially the case when the faults are associated with a Byzantine faulty node [5, 6, 16, 17]node5,6,16,17. In this model all links are assumed to be good. Miner et al. [16] Miner16, Geser, Pike, and Maddalon, for instance, model the absence of a link as a link fault and even though both nodes and links failures are considered, they abstractly model link failures as failures of the source node. In the link-centric model, which we refer to as the link-fault model, a fault is associated with the communication means connecting the source node to the destination node. In this model, all nodes are assumed to be good and an invalid message at the receiving node is counted as a single fault for the corresponding input link. Thus, from the global perspective, a Byzantine faulty node manifests as one or more multiple link failures. A link-fault model introduced by ▇▇▇▇▇▇▇▇, ▇▇▇▇▇, and ▇▇▇▇▇▇ et al. [18] is called perception-based hybrid fault model, where faults are viewed from the perspective of the receiving nodes. Faults are associated with their input links, and all nodes are assumed to be good. They argued that since F faulty nodes can produce at most F faulty perceptions in any node, the link-fault model is compatible with the traditional node-fault model and so, all existing lower bound and impossibility results remain valid.