Browse Prior Art Database

Clock Synchronization of a New Processor Joining a Network

IP.com Disclosure Number: IPCOM000043139D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Dolev, D: AUTHOR [+4]

Abstract

This invention relates to a method of establishing clock synchronization in a processor joining a network, and more particularly, to a method of resolving which clock value to adopt among two or more clock values manifested by counterpart subsets of processors, all but one of the clock values being faulty. The method is an aspect of a decentralized method for periodically synchronizing local clocks in a network of counterpart communicating processors. Both the drift rate between the clocks and the network message transit and processing times between sending and receiving processors are assumed to be bounded. In this invention, provision for joining and for initializing must be made. Each processor is assumed to belong initially to a synchronized cluster of size 1.

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Clock Synchronization of a New Processor Joining a Network

This invention relates to a method of establishing clock synchronization in a processor joining a network, and more particularly, to a method of resolving which clock value to adopt among two or more clock values manifested by counterpart subsets of processors, all but one of the clock values being faulty. The method is an aspect of a decentralized method for periodically synchronizing local clocks in a network of counterpart communicating processors. Both the drift rate between the clocks and the network message transit and processing times between sending and receiving processors are assumed to be bounded. In this invention, provision for joining and for initializing must be made. Each processor is assumed to belong initially to a synchronized cluster of size 1. It is assumed that the communicating processors can decide which processor is to join which cluster. However, outside intervention by an operator can also be assumed. Byzantine Agreement is used to establish both that a join protocol is about to be initiated and the identity of the joining processor(s). Any number of processors may join simultaneously as long as they are all included in the same agreement. One limitation is that the provision for joining agreement cannot take place within the maximum deviation of clocks (dmax) after a scheduled synchronization or (f+1)*dmax before a scheduled synchronization, f being the number of allowable faul...