In the “network-as-a-service” paradigm, network operators have a strong need to know the metrics of critical paths running services to their users/tenants. However, it is usually prohibitive to directly measure the metrics of all such paths due to the measuring overhead. A practical solution is to use network tomography to infer the metrics of such paths based on observations from a small number of monitoring nodes. This problem is termed as path identifiability problem, a new problem that largely differs from existing link identifiability problems. we show that the new problem is harder than link identifiability problems, in the sense that fewer monitors are required for identifying the metrics of given paths than for identifying the metrics of links along the paths. To solve the problem, we develop sufficient and necessary conditions for the identifiability of a given set of interested paths, and design an efficient algorithm that deploys the minimum number of monitors. Experiments show a saving of up to 40% fewer monitors that guarantee the identifiability of a given set of paths.

With the advances of Internet of Things technologies, individual vehicles can now exchange information to improve traffic safety, and some vehicles can further improve safety and efficiency by coordinating their mobility via cooperative driving. To facilitate these applications, many studies have been focused on the design of inter-vehicle message dissemination protocols. However, most existing designs either assume individual driving pattern or consider cooperative driving only. Moreover, few of them fully exploit infrastructures, such as cameras, sensors, and road-side units. In this paper, we address the design of message dissemination that supports heterogeneous driving patterns. Specifically, we first propose an infrastructure-assisted message dissemination framework that can utilize the capability of infrastructures. We then present a novel beacon scheduling algorithm that aims at guaranteeing the timely and reliable delivery of both periodic beacon messages for cooperative driving and event-triggered safety messages for individual driving. To evaluate the performance of the protocol, we develop both theoretical analysis and simulation experiments. Extensive numerical results confirm the effectiveness of the proposed protocol.

To efficiently provide cloud storage services, most providers implement data deduplication schemes so as to reduce storage and network bandwidth consumption. Due to its broad application, many security issues about data deduplication have been investigated, such as data security, user privacy, etc. Nevertheless, we note that the threat of establishing covert channel over cloud storage has not been fully investigated. In particular, existing studies only demonstrate the potential of a single-bit channel, in which a sender can upload one of the two predefined files for a receiver to infer the information of "0" and "1". In this paper, we design a more powerful deduplicationbased covert channel that can be used to transmit a complete message. Specifically, the key features of our design include: (1) a synchronization scheme that can establish a covert channel between a sender and a receiver, and (2) a novel coding scheme that allows each file to represent multiple bits in the message. To evaluate the proposed design, we implement the covert channel and conduct extensive experiments in different cloud storage systems. Our work highlights a more severe security threat in cloud storage services.