DoSDefender: A Kernel-Mode TCP DoS Prevention in Software-Defined Networking

The limited computation resource of the centralized controller and communication bandwidth between the control and data planes become the bottleneck in forwarding the packets in Software-Defined Networking (SDN). Denial of Service (DoS) attacks based on Transmission Control Protocol (TCP) can exhaust the resources of the control plane and overload the infrastructure of SDN networks. To mitigate TCP DoS attacks, DoSDefender is proposed as an efficient kernel-mode TCP DoS prevention framework in the data plane for SDN. It can prevent TCP DoS attacks from entering SDN by verifying the validity of the attempts to establish a TCP connection from the source, migrating the connection, and relaying the packets between the source and the destination in kernel space. DoSDefender conforms to the de facto standard SDN protocol, the OpenFlow policy, which requires no additional devices and no modifications in the control plane. Experimental results show that DoSDefender can effectively prevent TCP DoS attacks in low computing consumption while maintaining low connection delay and high packet forwarding throughput

Ni-catalyzed asymmetric C-P cross-coupling reaction via Ni(I)/Ni(III) two-electron pathway

Nickel demonstrates excellent performance in C-C or C-X cross-coupling reactions involving a SET process. However, the Ni(I)/Ni(III) two-electron pathway, which does not require light irradiation, is still rare, particularly in the asym-metric version. Here, we disclose a Ni(II)-catalyzed asymmetric C-P cross-coupling reaction via the Ni(I)/Ni(III) two-electron redox pathway. Combined experimental and computational research reveals that Ni(II) can be readily reduced to Ni(0) by secondary phosphine oxides, resulting in the formation of a Ni(I) active catalyst through comproportiona-tion. The discovery of the Ni(I)/Ni(III) two-electron mechanism may serve as a new paradigm of Ni catalysis, offering exciting opportunities in asymmetric reactions complementary to the traditional SET process

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Sequencing of 50 human exomes reveals adaptation to high altitude

Residents of the Tibetan Plateau show heritable adaptations to extreme altitude. We sequenced 50 exornes of ethnic Tibetans, encompassing coding sequences of 92% of human genes, with an average coverage of 18x per individual. Genes showing population-specific allele frequency changes, which represent strong candidates for altitude adaptation, were identified. The strongest signal of natural selection came from endothelial Per-Arnt-Sim (PAS) domain protein 1 (EPAS1), a transcription factor involved in response to hypoxia. One single-nucleotide polymorphism (SNP) at EPASl shows a 78% frequency difference between Tibetan and Han samples, representing the fastest allele frequency change observed at any human gene to date. This SNP's association with erythrocyte abundance supports the role of EPASl in adaptation to hypoxia. Thus, a population genomic survey has revealed a functionally important locus in genetic adaptation to high altitude. Copyright 2010 by the American Association for the Advancement of Science; all rights reserved.Link_to_subscribed_fulltex