Scalable Web Server Clustering Technologies

The exponential growth of the Internet, coupled with the increasing popularity of dynamically generated content on the World Wide Web, has created the need for more and faster Web servers capable of serving the over 100 million Internet users. Server clustering has emerged as a promising technique to build scalable Web servers. In this article we examine the seminal work, early products, and a sample of contemporary commercial offerings in the field of transparent Web server clustering. We broadly classify transparent server clustering into three categories.

A Generic Autonomous Clustering-Based Heterogeneous Waveband Switching Architecture in WDM Networks

Heterogeneous waveband switching (HeteroWBS) in WDM networks reduces the network operational costs. We propose an autonomous clustering-based HeteroWBS architecture to support the design of efficient HeteroWBS algorithms under dynamic traffic requests in such a network.

Layered Clustering Communication Protocol for Wireless Sensor Networks

In this paper, we propose a Layered Clustering Hierarchy (LCH) communication protocol for Wireless Sensor Networks (WSNs). The design of LCH has two goals: scalability and energy-efficiency. In LCH, the sensor nodes are organized as a layered clustering structure. Each layer runs a distributed clustering protocol. By randomizing the rotation of cluster heads in each layer, the energy load is distributed evenly across sensors in the network. Our simulations show that LCH is effective in densely deployed sensor networks. On average, 70% of live sensor nodes are involved directly in the clustering communication hierarchy. Moreover, the simulations also show that the energy load and dead nodes are distributed evenly over the network. As studies prove that the performance of LCH depends mainly on the distributed clustering protocol, the location of cluster heads and cluster size are two critical factors in the design of LCH.

Distribution and Specificity of Helminths in Microtine Rodents: Evolutionary Implications

The taxonomic status of anoplocephaline cestodes of microtine rodents has been reviewed. Of the genus Andrya Railliet, 1883, five species are considered valid: A. macrocephala Douthitt, 1915; A. primordialis Douthitt, 1915; A. montana Kirshenblat, 1941 ; A. arctica Rausch, 1952; A. bairdi Schad, 1954. Of the genus Paranoplocephala Luehe, 1910, six species are regarded as valid: P. omphalodes (Hermann, 1783); P. blanchardi (Moniez, 1891); P. infrequens (Douthitt, 1915); P. variabilis (Douthitt, 1915); P. lemmi Rausch, 1952; P. neofibrinus Rausch, 1952. Andrya caucasica Kirshenblat, 1938, and A. bialowizensis Soltys, 1949, are regarded as synonyms of A. macrocephala. Paranoplocephala brevis Kirshenblat, 1938, is regarded as a synonym of P. infrequens. Three species, A. macrocephala, P. omphalodes, and P. infrequens, are holarctic in distribution, occurring mainly in species of Microtus. The uniformity of microtine rodents as hosts for various helminths has been discussed. It is concluded that Dicrostonyx is the most isolated genus from this standpoint, having two nematodes which have not been recorded from members of other genera, and harboring few helminths in common with others. This agrees with Hinton's conclusions, based on morphological characters of Dicrostonyx. From the present concept of Pleistocene glaciations, it is concluded that P. omphalodes and P. infrequens reached the St. Matthew Islands, in Bering Sea, as parasites of a vole from which Microtus abbreviatus has evolved. It appears that this vole arrived on these islands before North America was invaded, in the late Pleistocene, by the palearctic M. oeconomus and Clethrionomys rutilus,/i>. The present known distribution of P. omphalodes in North America corresponds about to that of M. oeconomus on the continent.