The Cost of Timeliness without Synchronized Clocks

Nov 18, 1994

Abstract

Distributed systems often have the need to establish that an event has
occurred recently. Protocols that meet this timeliness requirement can
be classified into those that are based on the assumption of closely
synchronized clocks and those that are not. The latter relaxation
comes with a cost.

This talk will introduce the concepts of synchronous and asynchronous
timeliness of events, explain how the synchronous approach can be
broken by an active attack, and present a method for determining the
additional cost associated with protocols which do not require an
assumption of synchronized clocks. To illustrate the concepts we will
consider a simple data exchange scenario, establish the timeliness of
request and response in a synchronous and asynchronous approach, and
compare their cost.