Abstract
This paper describes a new message passing protocol that provides guaranteed detection of duplicate messages even when the receiver has no state stored for the sender. It also discusses how to use these messages to implement higher-level primitives such as at-most-once remote procedure calls and sequenced bytestream protocols, and describes an implementation of at-most-once RPCs using our method. Our performance measurements indicate that at-most-once RPCs can be provided at the same cost as less desirable RPCs that do not guarantee at-most-once execution. Our method is based on the assumption that clocks throughout the system are loosely synchronized. Modern clock synchronization protocols provide good bounds on clock skew with high probability; our method depends on the bound for performance but not for correctness.