This paper makes an analytical performance comparison of token rings, slotted rings, register--insertion rings and RIS rings in high--speed environments. The analyses of the four protocols are carried out under the same assumptions by the method of the equilibrium point analysis. In particular, we assume that each node has a finite buffer space and then calculate the probability of buffer overflow. The analytical results of each protocol are shown to be accurate through simulation. Comparing the performance of the protocols, we determine what constitutes the most suitable protocol for a given traffic environment. In the comparison, we take the probability of buffer overflow into consideration.