Supporting Real-Time Services Research Articles

Bidirectional and Malleable Proof-of-Ownership for Large File in Cloud Storage

Cloud storage is a cost-effective platform to accommodate massive data at low cost. However, advances of cloud services propel data generation, which pushes storage servers to its limit. Deduplication is a popular technique enjoyed by most current cloud servers, which detects and deletes redundant data to save storage and bandwidth. For security concerns, proof-of-ownership (PoW) can be used to guarantee ownership of data such that no malicious user could pass deduplication easily or utilize such mechanism for malicious purposes. Generally, PoW is implemented in static data archive where the data file is supposed to be read-only. However, to satisfy users’ needs for dynamical manipulation on data and support real-time data services, it is required to devise efficient PoW for dynamic archive. Inspired by malleable signature, which offers authentication even after its committed message changes, we propose the notion of bidirectional and malleable proof-of-ownership ( <inline-formula><tex-math notation="LaTeX">$\sf {BM\mbox{-}PoW}$</tex-math></inline-formula> ) for the above challenge. Our proposed <inline-formula><tex-math notation="LaTeX">$\sf {BM\mbox{-}PoW}$</tex-math></inline-formula> consists of bidirectional PoW ( <inline-formula><tex-math notation="LaTeX">${\mbox{B-PoW}}$</tex-math></inline-formula> ), malleable PoW ( <inline-formula><tex-math notation="LaTeX">${\mbox{M-PoW}}$</tex-math></inline-formula> ) and dispute arbitration protocol <inline-formula><tex-math notation="LaTeX">$\sf {DAP}$</tex-math></inline-formula> . While our <inline-formula><tex-math notation="LaTeX">${\mbox{B-PoW}}$</tex-math></inline-formula> is proposed for a static setting, the <inline-formula><tex-math notation="LaTeX">${\mbox{M-PoW}}$</tex-math></inline-formula> caters specifically for dynamic manipulation of data. In addition, our proposed arbitration protocol <inline-formula><tex-math notation="LaTeX">$\sf {DAP}$</tex-math></inline-formula> achieves accountable redaction which can arbitrate the originality of file ownership. We provide the security analysis of our proposal, and performance evaluation that suggests our proposed <inline-formula><tex-math notation="LaTeX">${\mbox{B-PoW}}$</tex-math></inline-formula> is secure and efficient for large file in static data archive. In addition, our proposed <inline-formula><tex-math notation="LaTeX">${\mbox{M-PoW}}$</tex-math></inline-formula> achieves acceptable performance under dynamic setting where data is supposed to be outsourced first and updated later in dynamic data archive.

A Hierarchical Game Framework for Resource Management in Fog Computing

Supporting real-time and mobile data services, fog computing has been considered as a promising technology to overcome long and unpredicted delay in cloud computing. However, as resources in FNs are owned by independent users or infrastructure providers, the ADSSs cannot connect and access data services from the FNs directly, but can only request data service from the DSOs in the cloud. Accordingly, in fog computing, the DSOs are required to communicate with FNs and allocate resources from the FNs to the ADSSs. The DSOs provide virtualized data services to the ADSSs, and the FNs, motivated by the DSOs, provide data services in the physical network. Nevertheless, with fog computing added as the intermediate layer between the cloud and users, there are challenges such as the resource allocation in the virtualized network between the DSOs and ADSSs, the asymmetric information problem between DSOs and ADSSs, and the resource matching from the FNs to the ADSSs in the physical network. In this article, we propose a three-layer hierarchical game framework to solve the challenges in fog computing networks. In the proposed framework, we apply the Stackelberg sub-game for the interaction between DSOs and ADSSs, moral hazard modeling for the interaction between DSOs and FNs, and the student project allocation matching sub-game for the interaction between FNs and ADSSs. The purpose is to obtain stable and optimal utilities for each DSO, FN, and ADSS in a distributed fashion.

Advanced Performance Enhancing Mechanisms for Supporting Real-Time Services on DVB-RCS System Environments

This paper describes two way satellite system environments on geostationary orbit (GEO) and performance enhancement mechanisms which reduces round trip time (RTT) and supports real-time services. We use performance enhancing proxy (PEP) for reducing round trip time and user-level real-time scheduler for reducing deadline violation tasks. The user-level real-time scheduling method classifies priority of user process into four types and those are reflected in kernel. With these dual performance enhancement mechanisms, we can improve quality of service (QoS) of end-user who connects to the DVB-RCS system.

Performance of Single-Hop WDM LANs Supporting Real-Time Services

Optical wavelength division multiplexing (WDM) local area networks are capable of fulfilling the enormous bandwidth demands of present and future applications. Up to now, the WDM LAN world is primarily dominated by the passive-star coupler (PSC) based architectures, for which many medium access control (MAC) protocols have been proposed. However, an arrayed waveguide grating multiplexer (AWGM)-based single-hop WDM network seems to be a very promising alternative. One of the most critical issues in designing next generation photonic LANs is the support of real-time services for applications with different time constraints. In this paper, different basic access protocols for the PSC as well as AWGM-based single-hop WDM LANs are considered and their performance in supporting real-time traffic is analyzed by means of extensive computer simulations. For evaluation of real-time performance, packet drop rates and deadline missing rates are taken as performance measures. Furthermore, new real-time message scheduling schemes are proposed which improve the performance of protocols accommodating mixed traffic. They can be differentiated between message scheduling at the source nodes’ transmit queues and scheduling based upon control information from a control channel. It is shown that both types of priority scheduling significantly improve the overall real-time performance.