{"id":338561,"date":"2016-12-19T13:26:36","date_gmt":"2016-12-19T21:26:36","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/?post_type=msr-research-item&p=338561"},"modified":"2018-10-16T21:02:14","modified_gmt":"2018-10-17T04:02:14","slug":"synchronizing-clocks-presence-faults","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/synchronizing-clocks-presence-faults\/","title":{"rendered":"Synchronizing Clocks in the Presence of Faults"},"content":{"rendered":"

Practical implementation of Byzantine agreement requires synchronized clocks. For an implementation to tolerate Byzantine faults, it needs a clock synchronization algorithm that can tolerate those faults. When I arrived at SRI, there was a general feeling that we could synchronize clocks by just having each process use a Byzantine agreement protocol to broadcast its clock value. I was never convinced by that hand waving. So, at some point I tried to write down precise clock-synchronization algorithms and prove their correctness. The two basic Byzantine agreement algorithms from [46]<\/a> did generalize to clock-synchronization algorithms. In addition, Melliar-Smith had devised the interactive convergence algorithm, which is also included in the paper. (As I recall, that algorithm was his major contribution to the paper, and I wrote all the proofs.)<\/p>\n

Writing the proofs turned out to be much more difficult than I had expected (see [27]<\/a>). I worked very hard to make them as short and easy to understand as I could. So, I was rather annoyed when a referee said that the proofs seemed to have been written quickly and could be simplified with a little effort. In my replies to the reviews, I referred to that referee as a “supercilious bastard”. Some time later, Nancy Lynch confessed to being that referee. She had by then written her own proofs of clock synchronization and realized how hard they were.<\/p>\n

Years later, John Rushby and his colleagues at SRI wrote mechanically verified versions of my proofs. They found only a couple of minor errors. I’m rather proud that, even before I knew how to write reliable, structured proofs (see [101]<\/a>), I was sufficiently careful and disciplined to have gotten those proofs essentially correct.<\/p>\n","protected":false},"excerpt":{"rendered":"

Practical implementation of Byzantine agreement requires synchronized clocks. For an implementation to tolerate Byzantine faults, it needs a clock synchronization algorithm that can tolerate those faults. When I arrived at SRI, there was a general feeling that we could synchronize clocks by just having each process use a Byzantine agreement protocol to broadcast its clock […]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","footnotes":""},"msr-content-type":[3],"msr-research-highlight":[],"research-area":[13561],"msr-publication-type":[193715],"msr-product-type":[],"msr-focus-area":[],"msr-platform":[],"msr-download-source":[],"msr-locale":[268875],"msr-post-option":[],"msr-field-of-study":[],"msr-conference":[],"msr-journal":[],"msr-impact-theme":[],"msr-pillar":[],"class_list":["post-338561","msr-research-item","type-msr-research-item","status-publish","hentry","msr-research-area-algorithms","msr-locale-en_us"],"msr_publishername":"","msr_edition":"","msr_affiliation":"","msr_published_date":"1985-01-01","msr_host":"","msr_duration":"","msr_version":"","msr_speaker":"","msr_other_contributors":"","msr_booktitle":"","msr_pages_string":"52-78","msr_chapter":"","msr_isbn":"","msr_journal":"Journal of the Association for Computing Machinery","msr_volume":"32","msr_number":"","msr_editors":"","msr_series":"","msr_issue":"1","msr_organization":"","msr_how_published":"","msr_notes":"","msr_highlight_text":"","msr_release_tracker_id":"","msr_original_fields_of_study":"","msr_download_urls":"","msr_external_url":"","msr_secondary_video_url":"","msr_longbiography":"","msr_microsoftintellectualproperty":1,"msr_main_download":"460596","msr_publicationurl":"","msr_doi":"","msr_publication_uploader":[{"type":"file","title":"synchronizing-clocks-in-the-presence-of-faults","viewUrl":"https:\/\/www.microsoft.com\/en-us\/research\/uploads\/prod\/2016\/12\/Synchronizing-Clocks-in-the-Presence-of-Faults.pdf","id":460596,"label_id":0}],"msr_related_uploader":"","msr_attachments":[],"msr-author-ordering":[{"type":"user_nicename","value":"lamport","user_id":32614,"rest_url":"https:\/\/www.microsoft.com\/en-us\/research\/wp-json\/microsoft-research\/v1\/researchers?person=lamport"},{"type":"text","value":"P. 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