Networking for manufacturing is gaining importance as a nerve system of computer-integrated manufacturing (CIM). Among the various network types, the most inexpensive type called fieldbus is specifically aimed to interconnect simple devices such as sensors and actuators. For this purpose, there are several choices of the protocols such as Profibus. WorldFIP, Foundation Fieldbus, and IEC/ISA fieldbus. This paper presents the simulation results of Profibus and WorldFIP. Both protocols have been simulated in order to evaluate the performance such as transmission delay and throughput under different protocol parameter settings and traffic conditions.