Node machines are added to subnet blockchains by the Network Nervous System (NNS). When the NNS forms a subnet blockchain, it combines node machines with the same standard specification. This means that every "correct" node machine in a subnet blockchain should be able to keep up with the others, since they all perform identical processing of blocks and smart contract computation. Problems should only occur in cases where nodes are using hardware that does not the meet the standard specification of the "node generation" to which they belong, if they are badly maintained within a rack, if the data centers hosting them have outages, or they are provided with insufficient bandwidth. If a node provider is dishonest, and changes a node's software from that which is automatically configured by the NNS, problems might also occur. In all such cases, the node is considered faulty, and this is revealed through its statistically deviating telemetry. For example, a faulty node might produce less blocks than the other nodes, which is a form of statistical deviance. If this happens, the NNS can levy penalties on the node or node provider, even excluding one or both from the network (if a node provider were excluded from the network, then all of their nodes would drop out of the network simultaneously). Numerous forms of telemetry can be applied in the determination of statistical deviation, which the NNS may seek to punish in the absence of other information. Although the process of determining that a node is faulty as the result of its statistical deviation, and the delivery of punishment through the NNS, is a major topic in its own right, simplified measures of correct behavior are possible. This chart shows what kind of node downtime occur before the NNS could take action to punish unacceptable deviation.
Note: Since the Internet Computer blockchain is created by a decentralized network, no service level agreement is involved, as no coordinating legal entity is involved. Instead, the NNS ensures that nodes are correctly operated as the result of cryptoeconomic incentives, which it creates by disbursing rewards to correct nodes, and punishing faulty nodes.
*Subject to change