A system, method, and computer program product are provided for optimal packet flow in a multi-processor system on a chip. In operation, a credit is allocated for each of a plurality of agents coupled to a messaging network, the allocating including reserving one or more entries in a receive queue of at least one of the plurality of agents. Additionally, a first credit is decremented in response to a first agent sending a message to a second agent, the plurality of agents including the first and second agents. Furthermore, one of the first credit or a second credit is incremented in response to a signal from the second agent.