用于IP追踪的包标记的注记

拒绝服务攻击是一类最难对付的网络安全问题.近来,人们提出了多种对策.其中由Savage等人提出的一类基于概率的包标记方案比较有研究价值.这里先对拒绝服务攻击的对策作一简述,然后分析了几种包标记方案,指出了它们的一些缺陷,并提出了一些改进措施.其中,对基本型概率包标记方案的一个修改使得计算量大大减少.

IP追踪中的自适应包标记

拒绝服务(DoS)攻击是目前最难处理的网络难题之一.最近,研究人员针对DoS攻击提出了多种方案,这些方案都各有优缺点.其中,由Savage等人提出的概率包标记方案受到了广泛的重视,也有不少的变种出现.在这一类的标记方案中,路由器以固定的概率选择是否标记一个数据包,这导致受害需要较多的数据包进行攻击路径的重构.本文提出一种自适应的标记策略,经实验验证受害者用较少的数据包即可重构攻击路径,这不仅为受害者及早地响应攻击争取了更多的时间,还限制了攻击者的伪造能力.

基于路由器编码的自适应包标记

拒绝服务攻击由于其高发性、大危害、难防范而成为因特网上的一大难题.研究人员为此提出了各种各样的对策,其中概率包标记具有较大的潜力.然而,现有的标记方案都存在各种各样的缺点.提出了一个新的标记方案,与其他标记方法相比,该方案具有反映灵敏,误报率低和计算量小的优点.此外,该方法还限制了攻击者伪造追踪信息的能力.

一种分块包标记的IP追踪方案

DDoS攻击以其高发性、高破坏力和难以防范的特点，近年来成为互联网的主要安全威胁之一．研究者们提出了多种对抗DDoS攻击的方法．：乓中，Savage等人提出的概率包标记方案以其易于实施、消耗资源小等优点，引起人们的重视．然而概率包标记方案存在两个明显缺陷：多攻击路径重构时的高误报率和高计算复杂度．在概率包标记的基础上，提出了一种分块包标记方案，该方案与概率包标记方案相比具有较低的误报率和较低的计算复杂度，因而具有更高的实际应用意义．

A stochastic jump and deterministic dynamics model of impact failure evolution with rate effect

Motivated by the observation of the rate effect on material failure, a model of nonlinear and nonlocal evolution is developed, that includes both stochastic and dynamic effects. In phase space a transitional region prevails, which distinguishes the failure behavior from a globally stable one to that of catastrophic. Several probability functions are found to characterize the distinctive features of evolution due to different degrees of nucleation, growth and coalescence rates. The results may provide a better understanding of material failure.

Direct dynamical test for deterministic chaos and optimal embedding of a chaotic time-series

We propose here a local exponential divergence plot which is capable of providing an alternative means of characterizing a complex time series. The suggested plot defines a time-dependent exponent and a ''plus'' exponent. Based on their changes with the embedding dimension and delay time, a criterion for estimating simultaneously the minimal acceptable embedding dimension, the proper delay time, and the largest Lyapunov exponent has been obtained. When redefining the time-dependent exponent LAMBDA(k) curves on a series of shells, we have found that whether a linear envelope to the LAMBDA(k) curves exists can serve as a direct dynamical method of distinguishing chaos from noise.

Direct dynamical test for deterministic chaos

We present a direct and dynamical method to distinguish low-dimensional deterministic chaos from noise. We define a series of time-dependent curves which are closely related to the largest Lyapunov exponent. For a chaotic time series, there exists an envelope to the time-dependent curves, while for a white noise or a noise with the same power spectrum as that of a chaotic time series, the envelope cannot be defined. When a noise is added to a chaotic time series, the envelope is eventually destroyed with the increasing of the amplitude of the noise.

Transmission properties through a double quantum dot with a wave packet

The transmiss on time and tunneling probability of an electron through a double quantum dot are studied using the transfer matrix technique. The time-dependent Schrodinger equation is applied for a Gaussian wave packet passing through the double quantum clot. The numerical calculations are carried out for a double quantum clot consisting of GaAs/InAs material. We find that the electron tunneling resonance peaks split when the electron transmits through the double quantum dot. The splitting energy increases as the distance between the two quantum dots decreases. The transmission time can be elicited from the temporal evolution of the Gaussian wave packet in the double quantum dot. The transmission time increases quickly as the thickness of tire barrier increases. The lifetime of the resonance state is calculated tram the temporal evolution of the Gaussian-state at the centers of quantum dots.

Deterministic Column-Based Matrix Decomposition

In this paper, we propose a deterministic column-based matrix decomposition method. Conventional column-based matrix decomposition (CX) computes the columns by randomly sampling columns of the data matrix. Instead, the newly proposed method (termed as CX_D) selects columns in a deterministic manner, which well approximates singular value decomposition. The experimental results well demonstrate the power and the advantages of the proposed method upon three real-world data sets.

The effect of human rhythm on packet delivery

In communication networks such as the Internet, the relationship between packet generation rate and time is similar to a rectangle wavefunction due to the rhythm of humans. Thus, we investigate the traffic dynamics on a network with a rectangle wavepacket generation rate. It is found that the critical delivering capacity parameter beta(c) (which separates the congested phase and the free phase) decreases significantly with the duty cycle r of the rectangle wave for package generation. And, in the congested phase, more collective generation of packets (smaller r) is helpful for decreasing the packet aggregation rate. Moreover, it is found that the congested phase can be divided into two regions, i.e., region1 and region2, where the distributions of queue lengths are nonlinear and linear, respectively. Also, the linear expression for the distribution of queue lengths in region2 is obtained analytically. Our work reveals an obvious effect of the rectangle wave on the traffic dynamics and the queue length distribution in the system, which is of essential interest and may provide insights into the designing of work-rest schedules and routing strategies.