Applying Formal Methods to Networking: Theory, Techniques and Applications

Despite its great importance, modern network infrastructure is remarkable for the lack of rigor in its engineering. The Internet which began as a research experiment was never designed to handle the users and applications it hosts today. The lack of formalization of the Internet architecture meant limited abstractions and modularity, especially for the control and management planes, thus requiring for every new need a new protocol built from scratch. This led to an unwieldy ossified Internet architecture resistant to any attempts at formal verification, and an Internet culture where expediency and pragmatism are favored over formal correctness. Fortunately, recent work in the space of clean slate Internet design---especially, the software defined networking (SDN) paradigm---offers the Internet community another chance to develop the right kind of architecture and abstractions. This has also led to a great resurgence in interest of applying formal methods to specification, verification, and synthesis of networking protocols and applications. In this paper, we present a self-contained tutorial of the formidable amount of work that has been done in formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial

Formal Probabilistic Analysis of a Wireless Sensor Network for Forest Fire Detection

Wireless Sensor Networks (WSNs) have been widely explored for forest fire detection, which is considered a fatal threat throughout the world. Energy conservation of sensor nodes is one of the biggest challenges in this context and random scheduling is frequently applied to overcome that. The performance analysis of these random scheduling approaches is traditionally done by paper-and-pencil proof methods or simulation. These traditional techniques cannot ascertain 100% accuracy, and thus are not suitable for analyzing a safety-critical application like forest fire detection using WSNs. In this paper, we propose to overcome this limitation by applying formal probabilistic analysis using theorem proving to verify scheduling performance of a real-world WSN for forest fire detection using a k-set randomized algorithm as an energy saving mechanism. In particular, we formally verify the expected values of coverage intensity, the upper bound on the total number of disjoint subsets, for a given coverage intensity, and the lower bound on the total number of nodes.Comment: In Proceedings SCSS 2012, arXiv:1307.802

Comparison of 18F FDG PET / CT, MRI (DWI + DCE) and MRI + 18F FDG PET/CT in the detection of axillary metastatic lymph nodes in patients with newly diagnosed breast cancer

Aim: We visually and quantitatively investigated the success of using 2-deoxy-2-[fluorine-18] fluoro-Dglucose integrated with computed tomography ( 18F-FDG PET/CT) and magnetic resonance imaging (MRI) [Dynamic contrast enhancement (DCE) and diffusion weighted imaging (DWI)] separately and together in detecting axillary lymph node metastasis in patients with newly diagnosed breast cancer. Methods: One hundred and thirteen patients who underwent 18F FDG PET/CT were evaluated, 102 patients of these patients had also MRI (DEC + DWI). Primary tumour size (Tsize), SUVmax of primary tumour (SUVmaxT), short diameter of largest axillary lymph node on PET/CT (LnDPET/CT), SUVmax of axillary lymph node (SUVmaxLn), metabolic tumour volume of the primary tumour (MTV), short diameter of largest axillary lymph node on MRI (LnDMRI), the presence of fatty hilum absence and apparent diffusion coefficient (ADC) were evaluated. Results: In visual analysis, sensitivity and specificity values of 18F FDG PET/CT, MRI and MRI+18F FDG PET/CT were 78.85, 94% – 72.27%, 96.15 – 83.87%, 98.04%, respectively. In the quantitative evaluation, ADC≤1.2 x 10-3 mm2 /sec (OR = 6.665, p = 0.001, 95CI%: 2.181–20.370) and LnSUVmax> 2 (OR = 15.2, p<0.001, 95CI%: 4.587–50.376) were independent predictors in detecting axillary lymph node metastasis. Conclusion: LnSUVmax >2 and ADC ≤ 1.2 x 10-3 mm2 /sec can be used as independent predictors of detecting axillary lymph node metastasis in patients with newly diagnosed breast cancer