The Totem single-ring protocol provides reliable totally ordered multicasting of messages to processes in process groups over a single local-area network (LAN) using a logical token-passing ring. The protocol provides two levels of message delivery: delivery in agreed order and delivery in safe order. This paper presents the probability density functions (PDFs) for the latency to message delivery for the Totem single-ring protocol for these two levels of service in the presence of both message loss and token loss. These PDFs are calculated by repeated convolutions of the PDFs for the various components of the latency. The analysis shows that the mean latency to safe delivery is greater than the mean latency to agreed delivery and that the tail of the latency distribution for safe delivery is longer. It also shows that a deterministic arrival process for message generation exhibits lower mean latencies and shorter tails of the latency distribution than a Poisson arrival process.

Multicast group communication protocols provide a foundation on which distributed systems can be built. The performance of these protocols is, however, not easy to characterize or to analyze. This research determines probability density functions for the latency to message delivery for the Totem multicast protocols, which provide reliable totally ordered delivery of multicast messages across single and multiple local-area networks (LANs). Totem uses a logical token-passing ring on each LAN with gateways that forward messages selectively between LANs. Comparing the performance of single-ring, two-ring and four-ring networks shows that, with message filtering in the gateways, multiple-ring networks can achieve lower mean latency, less variability in the latency, and shorter tails of the latency distribution than an equivalent single-ring network.