{"id":1185660,"date":"2026-09-09T09:37:37","date_gmt":"2026-09-09T16:37:37","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/?post_type=msr-research-item&#038;p=1185660"},"modified":"2026-09-09T09:37:39","modified_gmt":"2026-09-09T16:37:39","slug":"ssr-synchronous-state-machine-replication-with-a-timing-aligned-split-architecture","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/ssr-synchronous-state-machine-replication-with-a-timing-aligned-split-architecture\/","title":{"rendered":"SSR: Synchronous State Machine Replication with a Timing-Aligned Split Architecture"},"content":{"rendered":"\n\n\n<p class=\"wp-block-paragraph\">Modern datacenters exhibit different timing properties across the network fabric and the host software stack: the former offers bounded-delay delivery and precise clock synchronization, whereas the latter provides greater flexibility but substantially greater timing variability. This substrate-level separation matches the functional structure of State Machine Replication (SMR), whose normal case is timing-sensitive and repetitive while recovery requires flexible coordination, state transfer, and membership reconfiguration. We present SSR, a synchronous state machine replication protocol. SSR exploits this alignment with a split protocol design: normal-case replication runs as a round-based synchronous SMR protocol close to the network fabric, where replicas propose concurrently and commit from per-round local evidence without a steady-state leader, while recovery remains in a host-side path. Preliminary results show that SSR improves common-case throughput by 14.9<math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mo>\u00d7<\/mo><\/mrow><\/semantics><\/math>\u00d7&nbsp;with three replicas and 24.9<math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mo>\u00d7<\/mo><\/mrow><\/semantics><\/math>\u00d7&nbsp;with five replicas, completes recovery in about 0.15ms, and commits on the fast path after two rounds.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Modern datacenters exhibit different timing properties across the network fabric and the host software stack: the former offers bounded-delay delivery and precise clock synchronization, whereas the latter provides greater flexibility but substantially greater timing variability. This substrate-level separation matches the functional structure of State Machine Replication (SMR), whose normal case is timing-sensitive and repetitive while [&hellip;]<\/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":"","msr-author-ordering":[{"type":"user_nicename","value":"Paolo Costa","user_id":"33218"}],"msr_publishername":"","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"","msr_editors":"","msr_how_published":"","msr_isbn":"","msr_issue":"","msr_journal":"","msr_number":"","msr_organization":"ACM","msr_pages_string":"","msr_page_range_start":"","msr_page_range_end":"","msr_series":"","msr_volume":"","msr_copyright":"","msr_conference_name":"17th ACM SIGOPS Asia-Pacific Workshop on Systems 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