分布式拒绝服务(DDoS)攻击一直是互联网的主要威胁之一,在软件定义网络(SDN)中会导致控制器资源耗尽,影响整个网络正常运行。针对SDN网络中的DDoS攻击问题,文章设计并实现了一种两级攻击检测与防御方法。基于控制器北向接口采集交换机...分布式拒绝服务(DDoS)攻击一直是互联网的主要威胁之一,在软件定义网络(SDN)中会导致控制器资源耗尽,影响整个网络正常运行。针对SDN网络中的DDoS攻击问题,文章设计并实现了一种两级攻击检测与防御方法。基于控制器北向接口采集交换机流表数据并提取直接特征和派生特征,采用序贯概率比检验(Sequential Probability Ratio Test,SPRT)和轻量级梯度提升机(LightGBM)设计两级攻击检测算法,快速定位攻击端口和对攻击类型进行精准划分,通过下发流表规则对攻击流量进行实时过滤。实验结果表明,攻击检测模块能够快速定位攻击端口并对攻击类型进行精准划分,分类准确率达到98%,攻击防御模块能够在攻击发生后2 s内迅速下发防御规则,对攻击流量进行过滤,有效保护SDN网络的安全。展开更多
Da Qaidam salt lake is known for its both liquid and solid boron resource.Data from previous investigation of the Da Qaidam salt lake provided a comparable framework for this study that focused on investigating the se...Da Qaidam salt lake is known for its both liquid and solid boron resource.Data from previous investigation of the Da Qaidam salt lake provided a comparable framework for this study that focused on investigating the section beneath the bottom of the perennial salt lake,including the timing,展开更多
Seismic energy decays while propagating subsurface, which may reduce the resolution of seismic data. This paper studies the method of seismic energy dispersion compensation which provides the basic principles for mult...Seismic energy decays while propagating subsurface, which may reduce the resolution of seismic data. This paper studies the method of seismic energy dispersion compensation which provides the basic principles for multi-scale morphology and the spectrum simulation method. These methods are applied in seismic energy compensation. First of all, the seismic data is decomposed into multiple scales and the effective frequency bandwidth is selectively broadened for some scales by using a spectrum simulation method. In this process, according to the amplitude spectrum of each scale, the best simulation range is selected to simulate the middle and low frequency components to ensure the authenticity of the simulation curve which is calculated by the median method, and the high frequency component is broadened. Finally, these scales are reconstructed with reasonable coefficients, and the compensated seismic data can be obtained. Examples are shown to illustrate the feasibility of the energy compensation method.展开更多
文摘分布式拒绝服务(DDoS)攻击一直是互联网的主要威胁之一,在软件定义网络(SDN)中会导致控制器资源耗尽,影响整个网络正常运行。针对SDN网络中的DDoS攻击问题,文章设计并实现了一种两级攻击检测与防御方法。基于控制器北向接口采集交换机流表数据并提取直接特征和派生特征,采用序贯概率比检验(Sequential Probability Ratio Test,SPRT)和轻量级梯度提升机(LightGBM)设计两级攻击检测算法,快速定位攻击端口和对攻击类型进行精准划分,通过下发流表规则对攻击流量进行实时过滤。实验结果表明,攻击检测模块能够快速定位攻击端口并对攻击类型进行精准划分,分类准确率达到98%,攻击防御模块能够在攻击发生后2 s内迅速下发防御规则,对攻击流量进行过滤,有效保护SDN网络的安全。
文摘Da Qaidam salt lake is known for its both liquid and solid boron resource.Data from previous investigation of the Da Qaidam salt lake provided a comparable framework for this study that focused on investigating the section beneath the bottom of the perennial salt lake,including the timing,
文摘Seismic energy decays while propagating subsurface, which may reduce the resolution of seismic data. This paper studies the method of seismic energy dispersion compensation which provides the basic principles for multi-scale morphology and the spectrum simulation method. These methods are applied in seismic energy compensation. First of all, the seismic data is decomposed into multiple scales and the effective frequency bandwidth is selectively broadened for some scales by using a spectrum simulation method. In this process, according to the amplitude spectrum of each scale, the best simulation range is selected to simulate the middle and low frequency components to ensure the authenticity of the simulation curve which is calculated by the median method, and the high frequency component is broadened. Finally, these scales are reconstructed with reasonable coefficients, and the compensated seismic data can be obtained. Examples are shown to illustrate the feasibility of the energy compensation method.
