This is the third of five papers comprising The Semantic Arrow of Time. Parts I and II identified computing's hidden semantic arrow of time, the FITO category mistake, and presented the constructive alternative: the OAE link state machine with its mandatory reflecting phase. This paper examines what happens when those principles are violated at industrial scale. Remote Direct Memory Access (RDMA) is the highest-performance data movement technology in production, deployed across Meta's 24,000-GPU clusters, Google's data centers, and Microsoft's Azure infrastructure. We argue that RDMA's completion semantics contain a category mistake: they guarantee placement (data written to a remote NIC buffer) but not commitment (data semantically integrated by the receiving application). We call this the completion fallacy. We document the fallacy through seven temporal stages of an RDMA Write operation, showing that the gap between completion signal and application semantic satisfaction can be arbitrarily large. We trace consequences through four case studies: Meta's RoCE fabric, Google's 1RMA redesign, Microsoft's DCQCN failures, and SDR-RDMA partial completions. A comparative analysis shows CXL 3.0, NVLink, and UALink each address parts of the completion fallacy but none eliminates it entirely. Only a protocol architecture with a mandatory reflecting phase can close the gap between delivery and commitment.

翻译：本文是《语义时间箭头》系列五篇论文中的第三篇。前两部分揭示了计算中隐藏的语义时间箭头、FITO范畴错误，并提出了建设性替代方案：包含强制反射阶段的OAE链路状态机。本文探讨当这些原则在工业规模上被违反时的后果。远程直接内存访问（RDMA）是生产环境中最高性能的数据传输技术，已部署于Meta的24,000-GPU集群、谷歌数据中心及微软Azure基础设施。我们论证RDMA的完成语义存在范畴错误：它保证数据放置（写入远程网卡缓冲区）但未保证数据提交（被接收端应用语义整合）。我们称之为完成谬误。通过分析RDMA写操作的七个时序阶段，我们记录了这一谬误，证明完成信号与应用程序语义满足之间的间隔可能无限大。我们通过四个案例研究追踪其后果：Meta的RoCE架构、谷歌的1RMA重新设计、微软DCQCN故障以及SDR-RDMA部分完成问题。比较分析表明，CXL 3.0、NVLink和UALink各自解决了完成谬误的部分问题，但均未完全消除。唯有采用强制反射阶段的协议架构才能弥合数据交付与语义提交之间的鸿沟。