The formal analysis of a data-transfer protocol based on the novel idea of periodic state exchange has been presented by Gouda et al. (see IEEE Trans. Commun., vol.43, no.9, p.2475-84, 1995). In certain environments, such as the Internet, the requirements for the correctness of the protocol may impose impractical constraints. We present an alternative specification of the periodic state-exchange protocol based on the discovery that the protocol can be treated as a special sliding-window protocol. Although our protocol behaves better in an Internet-like environment it has other shortcomings with respect to the original. The comparison of the alternatives reveals the trade-offs in their design.

The authors comment on a class of minimum-latency transport protocols that have been analyzed by Shankar and Lee (see ibid., vol.3, no.3, p.255, 1995). The protocols use unique incarnation numbers and caching schemes to reduce the latency of connection setup whenever possible. They discuss three modifications to the protocol. (1) A modification to the opening procedure which eliminates some constraints for the correctness of the protocol. (2) A modification which allows data messages in the opening state of the client to be sent. This reduces the latency in some situations for the price of stricter constraints for correctness. (3) An alternate way of closing connections. Apart from these modifications, they also show that the proofs can be refined to get somewhat less restrictive constraints for the correctness of the protocol.