Talks & Seminars
Title: Revisiting Clocks in Distributed Systems
Prof. Sandeep Kulkarni, Michigan State Univ, Michigan State University
Date & Time: July 25, 2017 11:30
Venue: Conference Room, C Block, 01st Floor, Dept. of CSE, Kanwal Rekhi (KReSIT) Bldg.
When it comes to clocks in distributed systems, the theory and practice of distributed systems are often conflicting. The theory ignored the physical clocks and introduced the notion of causality that captured information flow among processes in a distributed system. The practice utilized physical clocks --often in an ad-hoc manner—using protocols such as NTP. The causality --that captures the information flow—assumes that no external communication occurs between processes and, hence, it cannot accommodate complex systems of systems where such external communication in inevitable. On the other hand, while NTP provides reasonable clock synchronization, it suffers from errors caused by link errors, varying latency, non-monontonic updates and so on. In this talk, we will discuss related work in uniting these two aspects by introducing the notion of hybrid logical clocks (HLC) and hybrid vector clocks (HVC). These clocks provide the benefits of both logical clocks and physical clocks. Specifically, we illustrate how they can be used in applications that rely on physical clocks (e.g., transaction systems or causally consistent data stores) as well as that rely on logical clocks (e.g., to provide snapshots, checkpointing and recovery and so on).
Speaker Profile:
Sandeep Kulkarni received B. Tech from Computer Science and Engineering in 1993 from IIT Bombay and MS and PhD degree from the Ohio State University in 1994 and 1999 respectively. After that, he joined Michigan State University where he is currently a Professor in the Department of Computer Science and Engineering. His interests lie in Distributed Systems, fault-tolerance, formal methods and Fault Tolerance.
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