The connected and autonomous systems (CAS) and auto-driving era is coming into our life. To support CAS applications such as AI-driven decision-making and blockchain-based smart data management platform, data and message exchange/dissemination is a fundamental element. The distributed message broadcast and forward protocols in CAS, such as vehicular ad hoc networks (VANET), can suffer from significant message loss and uncertain transmission delay, and faulty nodes might disseminate fake messages to confuse the network. Therefore, the consensus mechanism is essential in CAS with distributed structure to guaranteed correct nodes agree on the same parameter and reach consistency. However, due to the wireless nature of CAS, traditional consensus cannot be directly deployed. This article reviews several existing consensus mechanisms, including average/maximum/minimum estimation consensus mechanisms that apply on quantity, Byzantine fault tolerance consensus for request, state machine replication (SMR) and blockchain, as well as their implementations in CAS. To deploy wireless-adapted consensus, we propose a Directed Acyclic Graph (DAG)-based message structure to build a non-equivocation data dissemination protocol for CAS, which has resilience against message loss and unpredictable forwarding latency. Finally, we enhance this protocol by developing a two-dimension DAG-based strategy to achieve partial order for blockchain and total order for the distributed service model SMR.

翻译：互联自主系统（CAS）与自动驾驶时代正逐步融入我们的生活。为支撑AI驱动决策、基于区块链的智能数据管理平台等CAS应用，数据与消息的交换/传播是基础要素。在CAS（如车载自组织网络VANET）中，分布式消息广播与转发协议可能面临显著的消息丢失和不确定的传输延迟，而故障节点可能传播虚假消息以混淆网络。因此，在具有分布式结构的CAS中，共识机制对于保证正确节点就同一参数达成一致并实现一致性至关重要。然而，由于CAS的无线特性，传统共识无法直接部署。本文综述了多种现有共识机制，包括应用于数量估计的平均/最大/最小共识机制、用于请求处理的拜占庭容错共识、状态机复制（SMR）与区块链，及其在CAS中的实现。为部署无线自适应的共识，我们提出了一种基于有向无环图（DAG）的消息结构，用于构建CAS中具备抗消息丢失与不可预测转发延迟能力的非欺骗数据传播协议。最后，我们通过开发一种基于二维DAG的策略来增强该协议，从而为区块链实现偏序，为分布式服务模型SMR实现全序。