This is the second of five papers comprising The Semantic Arrow of Time. Part I established that computing's arrow of time is semantic rather than thermodynamic, and that the Forward-In-Time-Only (FITO) assumption constitutes a category mistake. This paper develops the constructive alternative. We present the semantics of Open Atomic Ethernet (OAE) links as a concrete realization of a non-FITO protocol architecture. The key insight is that causal order is not assumed a priori but created through transaction structure: the link state machine progresses through TENTATIVE to REFLECTING to COMMITTED, with the option to abort at any point before commitment. Delivery does not imply commitment; commitment requires reflective acknowledgment -- proof that information has round-tripped and been semantically validated by both endpoints. We formalize this through three frameworks. First, the OAE link state machine, a six-state finite automaton whose normative invariants guarantee that semantic corruption cannot occur at the link level. Second, Indefinite Logical Timestamps (ILT), a four-valued causal structure that admits a genuinely indefinite relation between concurrent events, resolving only after symmetric link-level exchange. Third, the Slowdown Theorem applied to links, which establishes that round-trip measurement is the minimum interaction required to establish causal order. We show that ILT is strictly more expressive than Definite Causal Order systems for reversible link protocols. We connect these results to the Knowledge Balance Principle from quantum information theory. The paper concludes with a comparative analysis showing that OAE achieves infinite consensus number while RDMA, NVLink, and UALink remain limited to finite consensus numbers due to their FITO semantics.

翻译：本文是《语义时间箭头》系列五篇论文中的第二篇。第一部分论证了计算的时间箭头本质上是语义的而非热力学的，且“仅向前时间”（FITO）假设构成了一种范畴错误。本文则构建了建设性的替代方案。我们提出开放原子以太网（OAE）链路的语义学，作为非FITO协议架构的具体实现。核心洞见在于：因果顺序并非先验假设，而是通过事务结构创建的——链路状态机经历从“暂定”（TENTATIVE）到“反射”（REFLECTING）再到“提交”（COMMITTED）的演进，并可在提交前的任何阶段中止。交付不意味着提交；提交需要反射式确认——即信息已完成往返并被两端点语义验证的证明。我们通过三个框架对此进行形式化。首先，OAE链路状态机，一个六状态有限自动机，其规范性不变性保证了语义损坏无法在链路层级发生。其次，不定逻辑时间戳（ILT），一种四值因果结构，允许并发事件间存在真正的不定关系，仅在对等链路层级交换后才得以解析。第三，应用于链路的减速定理，该定理确立了往返测量是建立因果顺序所需的最小交互。我们证明，对于可逆链路协议，ILT的表达能力严格强于确定因果顺序系统。我们将这些结果与量子信息论中的知识平衡原理联系起来。论文最后通过比较分析表明，OAE实现了无限共识数，而RDMA、NVLink和UALink由于其FITO语义，仍局限于有限共识数。