Sharif Digital Repository

The peer to peer (P2P) file sharing applications have allocated a significant amount of today's Internet traffic. Among various P2P file sharing protocols, BitTorrent is the most common and popular one that attracts monthly a quarter of a billion users from all over the world. Similar to other P2P file sharing protocols, BitTorrent is mostly used for illegal sharing of copiright protected files such as movies, music and TV series. To impede this huge amount of illegal file distributions, anti-P2P companies have arisen to stand against these applications (specially the BitTorrent). To this end, they have begun to fire large-scale Internet attacks against BitTorrent networks. In this paper, we... 

In this paper, one of the most important parameters in performance evaluation and protocol design of wireless networks, Link Excess Life (LEL), is investigated. An analytical model for LEL is proposed and evaluated. Evaluation of the proposed model leads to the first closed form expression for the excess life PDF. The closed form expression affords ease of further evaluations, e.g, an interesting result is that the average excess life is infinite for the proposed model. The effect of relative velocity distribution on the link excess life PDF is also investigated. The superposition property of LEL is mentioned and used to explore a systematic method for evaluation of the effect of stationary... 

Recently XML has become a standard for data representation and the preferred method of encoding structured data for exchange over the Internet. Moreover it is frequently used as a logical format to store structured and semi-structured data in databases. We propose a model-driven and configurable approach for modeling hierarchical XML data using object role modeling (ORM) as a flat conceptual model. First a non-hierarchical conceptual schema of the problem domain is built using ORM and then different hierarchical views of the conceptual schema or parts of it are specified by the designer using transformation rules. A hierarchical modeling notation called H-ORM is proposed to show these... 

Artificial Immune System (AIS) models have outstanding properties, such as learning, adaptivity and robustness, which make them suitable for learning in dynamic and noisy environments such as the web. In this study, we tend to apply AIS for tracking evolving patterns of web usage data. The definition of the similarity of web sessions has an important impact on the quality of discovered patterns. Many prevalent web usage mining approaches ignore the sequential nature of web navigations for defining similarity between sessions. We propose the use of a new web sessions' similarity measure for investigating the usage data from web access log files. In this similarity measure, in addition to the...