—The feasibility of a message in a network concerns if its timing property can be satisfied without jeopardizing any messages already in the network to meet their timing properties. We present a novel feasibility analysis for real-time (RT) and nonrealtime (NT) messages in wormhole-routed networks on chip. For RT messages, we formulate a contention tree that captures contentions in the network. For coexisting RT and NT messages, we propose a simple bandwidth partitioning method that allows us to analyze their feasibility independently.