Dynamic fault-tolerant clock synchronization

Abstract

This paper gives two simple efficient distributed algorithms: one for keeping clocks in a network synchronized and one for allowing new processors to join the network with their clocks synchronized. Assuming a fault-tolerant authentication protocol, the algorithms tolerate both link and processor failures of any type. The algorithm for maintaining synchronization works for arbitra~networks (rather than just completely connected networks) and tolerates any number of processor or communication link faults as long as the correct processors remain connected by fault-free paths. It thus represents an improvement over other clock synchronization algorithms such as those of Lamport and Melliar-Smith [1985] and Welch and Lynch [1988], although, unlike them, it does require an authentication protocol to handle Byzantine faults. Our algorithm for allowing new processors to join requires that more than half the processors be correct, a requirement that is provably necessa~.

Self-stabilization of Byzantine Protocols

“…Consider the Byzantine clock synchronization algorithm in [10]. Informally that algorithm operates as follows: The processes resynchronize their clocks every PER time period.…”

Diffusive clock synchronization in highly dynamic networks

“…Each node then sets its clock on its local outcome of the agreement procedure. Dolev et al [9] presented an algorithm that can cope with dynamic networks. However, they require that each correct node can communicate with each other correct node in bounded time; a property that is violated, e.g., in leader-based topologies like a directed star-graph.…”

Secure and resilient clock synchronization in wireless sensor networks

“…It is natural to consider fault-tolerant clock synchronization techniques, which have been studied extensively in the context of distributed systems (e.g., [12]- [16]). However, these techniques require either digital signatures (e.g., HSSD [16]and CSM [15]), exponential copies of messages (e.g., COM [15]), or a completely connected network (e.g., CNV [15]) to prevent malicious nodes from modifying or destroying clock information sent by normal nodes.…”

“…However, these techniques require either digital signatures (e.g., HSSD [16]and CSM [15]), exponential copies of messages (e.g., COM [15]), or a completely connected network (e.g., CNV [15]) to prevent malicious nodes from modifying or destroying clock information sent by normal nodes. Thus, they are not practical in wireless sensor networks.…”