Flood and Contain: An Optimized Repeal-Based Flooding Algorithm for Wireless Ad Hoc and Sensor Networks.

Flooding is a simple yet reliable way of discovering resources in wireless ad hoc networks such as mobile ad hoc networks (MANETs), ad hoc sensors, and recently, IoT networks. However, its operation is resource-intensive, especially in densely populated networks. Several approaches can be found in the literature to reduce the impact of flooding. Many of these approaches follow a repeal-based operation, chasing and stopping further propagation of flooding packets once the target is found. However, repeal-based protocols might end up transmitting even more packets than the original flooding. This work characterizes a maximum repeal-flooding boundary beyond which it is counterproductive to chase the original flooding. We present the Flood and Contain (F&C) algorithm, a method that can quickly establish the maximum repeal-flooding boundary for each node while making no assumptions on the underlying network. F&C's packet overhead increases linearly with the hop count up to the maximum repeal-flooding boundary, in which case there is no attempt to chase the original flooding. In this latter case, F&C generates only as many packets as the original flooding. Simulations show that, on average, F&C reduces the total flooding overhead (compared to traditional flooding) up to 35 percent once considering all possible destinations, with only a slight increase in resource discovery latency, and it outperforms all other repeal-based protocols, particularly for longer routes.

Prevalence of Pneumococcal Nasopharyngeal Carriage Among Children 2-18 Months of Age: Baseline Study Pre Introduction of Pneumococcal Vaccination in Cuba.

BACKGROUND: A new vaccine candidate against pneumococcus is being developed in Cuba, and it is a priority of the national health system. There is limited information on nasopharyngeal colonization burden, though it is essential for monitoring the impact of the vaccine. The study aims to estimate the prevalence of nasopharyngeal colonization in children 2-18 months of age and identify circulating serotypes, antimicrobial resistance and its association with selected risk factors. METHODS: A cross-sectional study was conducted between October and December 2013 in Cienfuegos municipality. Inclusion criteria were evaluated, and informed consent was obtained from the parents. Clinical and epidemiologic data were collected through a semistructured questionnaire. Nasopharyngeal swabs according to established protocols were taken. Data analysis included frequency distributions and comparison of proportions. The association between colonization and selected risk factors was assessed by multivariate analysis. RESULTS: A total of 984 children (87.2% living in urban areas) were included. The overall prevalence of colonization was 21.6%. The most frequent serotypes isolated were 6A (23.1%), 23F (10.8%), 6B (10.3%), 19F (8.5%) and 14 (3.3%). We found no resistance to ß-lactamases in circulating serotypes. Living with sibling younger than 5 years, previous respiratory infections, previous hospitalization and day-care attendance were determinants of nasopharyngeal carriage. CONCLUSIONS: The findings suggest that the burden of pneumococcal disease and colonization in Cuba could be significantly affected after vaccine introduction.