Quality of Time: A New Perspective in Designing Cyber-Physical Systems
Quality of Time: A New Perspective in Designing Cyber-Physical Systems
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时间质量：设计网络物理系统的新视角
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发表时间：
2019
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通讯作者：
F. Anwar
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作者：
F. Anwar
作者(S)：Anwar，Fatima Muhammad|Advisor(S)：Sriastava，Mani B|摘要：前所未有的网络物理系统(CP)和物联网(IoT)应用，如医疗保健、联网车辆和增强/虚拟现实正在给智能空间带来革命性的变化，并改变我们构建和管理系统的方式。这些应用跨越了云和边缘设备，并催生了新的系统设计，其关键依赖于时间上的用例。因此，云服务需要提供及时的响应和可调度的需求，而边缘设备则需要跨分布式实体同步观察和编排动作。云和边缘通常都需要时间感知，特别是时间索引查询、精确的时间戳和动态时钟同步。然而，当代的分布式系统设计本质上是“无时钟的”，并且变得越来越复杂。它们不能满足底层应用程序的一致性、因果关系和调度需求，但对于运行在商用平台和操作系统(OS)上的各种应用程序来说，启用时间感知本身就是一个挑战。在本文中，我们通过引入时间质量(Qot)的概念来设计一种新的获取时间信息的方法，该Qot集合了分辨率、准确性、稳定性和完整性等各种时间度量。类似于网络中的服务质量(Qos)，Qot将时间视为具有可观察到的性能的可控操作系统原语。为了向应用程序提供QOT，我们提出了第一个操作系统抽象-时间线-它响应应用程序的时间需求，并以易于使用、安全和可扩展的方式向应用程序公开QOT。这种程度的信息丰富度从未提供给协调的应用程序，这些应用程序的活动是跨时间和空间编排的。这种信息流立即与更广泛的物联网领域相关，以安全的方式解决云和边缘应用程序的新兴临时用例。因此，Qot在没有显著开销的情况下将分布式应用扩展到全球规模，并且不会对性能造成影响。在本论文的第一部分，我们设计了可扩展的抽象来刻画存在时序变化时的时序不确定性。为了降低当前分布式数据库设计的复杂性和开销，我们的抽象和系统以简化的设计、低开销和不损失性能的方式支持全局复制的无锁事务。第二部分揭示了可信执行技术和网络安全机制中的计时漏洞，并通过在存在漏洞的情况下设计安全的时间体系结构来提供计时完整性。从而在商品系统中实现可信的时间戳，以保护个人的数字权利和数字信号。第三部分重点是重新设计硬件、操作系统和网络接口，以帮助计时信息在应用程序和系统之间流动，并实现计时精度。这种精度提高了大规模分布式实体的高速测量。最后一节讨论了在安全关键环境中部署的时间同步协议测试机制的无效。目前的分布式系统设计依赖于基于消息传递的协议，具有巨大的能量和带宽开销以及较高的系统复杂度。相比之下，我们设计的基于QOT的系统以较低的计算和通信开销支持新的全球分布式应用的时态用例。我们发布了我们的系统设计，以支持新兴分布式应用程序中的各种时间管理和时钟同步用例。
Author(s): Anwar, Fatima Muhammad | Advisor(s): Srivastava, Mani B | Abstract: Unprecedented Cyber-Physical Systems (CPS) and Internet of Things (IoT) applications such as health care, connected vehicles, and augmented/virtual reality are revolutionizing smart spaces and change how we build and manage our systems. These applications span the cloud and the edge devices and give birth to new system designs with critical dependence on temporal use cases. As such, cloud services are expected to provide timely responses and schedulable demands, while edge devices are required to synchronize observations and choreograph actions across distributed entities. Both cloud and edge demand time awareness in general, and time-indexed queries, precise timestamping, and dynamic clock synchronization in particular. However, contemporary distributed system designs are inherently “clockless” and becoming increasingly complex. They fail to meet consistency, causality, and scheduling demands of underlying applications yet enabling time awareness for various applications running on commodity platforms and operating systems (OS) is a challenge in itself.In this dissertation, we devise a new way of acquiring time information by introducing the notion of Quality of Time (QoT) that collectively captures various time metrics such as resolution, accuracy, stability, and integrity. Analogous to Quality of Service (QoS) in networking, QoT treats time as a controllable OS primitive with observable performance. To provide QoT to applications, we proposed the first OS abstraction – timeline – that reacts to application timing demands and exposes QoT to applications in an easy-to-use, secure, and scalable way. This degree of richness of information had never been available to coordinated applications whose activities are choreographed across time and space. This flow of information was immediately relevant to the broader field of IoT addressing the emerging temporal use cases for applications at the cloud and the edge in a secure fashion. As such, QoT expanded distributed applications to a global scale with no significant overhead and no performance compromise.This dissertation focuses on covering various aspects of QoT. In the first part of this thesis, we design extensible abstractions to characterize timing uncertainty in the presence of timing variations. In an effort to reduce complexity and overhead of current distributed database designs, our abstractions and systems enable globally replicated lockless transactions with simplified design, low overhead and no loss in performance. The second part exposes timing vulnerabilities in trusted execution technologies and network security mechanisms and provides timing integrity by designing secure time architectures in the presence of vulnerabilities. Thus enabling trusted timestamping in commodity systems to preserve one’s digital rights and digital signals. The third part focuses on redesigning the hardware, OS and network interfaces that help time information flow between applications and systems, and enable timing precision. This precision boosts high-speed measurements at large-scale distributed entities. The final section addresses the inefficacy of testing mechanisms for time synchronization protocols deployed in safety-critical environments. We then propose a customized testbed for testing timing robustness under failures and adversarial attacks.Current designs in distributed systems rely on message-passing based protocols and come at a huge energy and bandwidth cost along with high system complexity. In contrast, our designed systems based on QoT support new temporal use cases of globally distributed applications with low computation and communication overhead. We released our system designs to support various time management and clock synchronization use cases in emerging distributed applications.