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Multiplicative Cascades for Non-Stationary Computer Network Traffic. Patricia H. Carter Naval Surface Warfare Center Dahlgren June 11, 2002. data. internet. Firewall. Enclave. traffic. data collector. Packet Rate Process. TCP packets entering/leaving protected network
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Multiplicative Cascades for Non-Stationary Computer Network Traffic Patricia H. Carter Naval Surface Warfare Center Dahlgren June 11, 2002
data internet Firewall Enclave traffic data collector Statistis & Machine Learning in Computer Intrusion Detection
Packet Rate Process • TCP packets entering/leaving protected network • raw data is arrival times • packet rate process is # of packets/unit time Statistis & Machine Learning in Computer Intrusion Detection
Multiplicative cascade: pros and con Motivation: packet rate process roughly lognormal hierarchal model of user sessions Anti-motivation: central role of multiplexing for aggregate traffic Statistis & Machine Learning in Computer Intrusion Detection
Packet Rate Process “approximately” Log Normal – Hour 12 Statistis & Machine Learning in Computer Intrusion Detection
Individual IP user model - web session pages connections packets Statistis & Machine Learning in Computer Intrusion Detection
e.g., One Web Page Statistis & Machine Learning in Computer Intrusion Detection
Multiplexing on-off – “connections” Statistis & Machine Learning in Computer Intrusion Detection
Random Multiplicative Cascade synthesis – three realizations Statistis & Machine Learning in Computer Intrusion Detection
On/Off model for single process implies self-similarity for aggregate Suppose the each individual process is modeled by a On/Off process with Pareto distribution: Then the aggregate cumulative packet rate process behaves statistically like fractional Brownian motion – it is self-similar with scaling parameter: Taqqu, Willinger, Sherman, Proof of a Fundamental Result in Self-Similar Traffic Modeling 1997 Statistis & Machine Learning in Computer Intrusion Detection
Multiplicative Cascade:synthesis m p 1-p pm (1-p)m p is a random variable from a distribution(s) supported on [0,1] conservative cascade: pm+(1-p)m=m Statistis & Machine Learning in Computer Intrusion Detection
Multiplicative Cascade:analysis a+b 1-p=b/(a+b) p=a/(a+b) a b If (a+b)=0 then choose p uniformly from {0,1} . The values 0 and 1 are markers for empty subintervals. Statistis & Machine Learning in Computer Intrusion Detection
Multifractal Aggregate Traffic ModelRandom Multiplicative Cascade 1 p p 1-p p0,p1 V1 p (1-p0) p p0 (1-p1) (1-p) p1 (1-p) p00,p01,p10,p11 [m, p, p0, p1, p00, p01, p10, p11] Statistis & Machine Learning in Computer Intrusion Detection
the vector P of multipliers Suppose packet rate process R has 2L samples next smallest scale p’s smallest scale p’s in time order Finally P and R are a transform pair. Statistis & Machine Learning in Computer Intrusion Detection
Packet Rate Process:Three Resolutions Statistis & Machine Learning in Computer Intrusion Detection
Multipliers calculated via inverse cascade procedure Statistis & Machine Learning in Computer Intrusion Detection
Multipliers Plotted as a Function of Scale – hour 0 Statistis & Machine Learning in Computer Intrusion Detection
Multipliers Plotted as a Function of Scale – hour 12 Statistis & Machine Learning in Computer Intrusion Detection
Histograms of variance-normalized Multipliers and fitted Beta distribution Statistis & Machine Learning in Computer Intrusion Detection
Log Variances of Multipliers versus Log Scale - Hour 12 Statistis & Machine Learning in Computer Intrusion Detection
Multiple Scale Empirical Structure Function where are the multipliers calculated at level M. Statistis & Machine Learning in Computer Intrusion Detection
Multiple Scale Structure Functions From Variance-Normalized Multipliers Statistis & Machine Learning in Computer Intrusion Detection