The aim of the book is to present network performance analysis techniques. The topics are presented with the aid of the J programming language, an ideal tool for analytical methods due to its richness in mathematical functionality. The first two introductive chapters are devoted to a description of J. The next six chapters are dedicated to network performance issues like traffic flow, effective bandwidth, equivalent capacity, quality of service, short or long-range dependence, congestion control and others. New models are introduced for short and long-rate dependence: autoregressive and moving average models for generating short-range dependent time series and fractional autoregressive integrated moving average models for generating long-range dependent time series. Another interesting topic approached by the author is that of traffic simulation with discrete on/off models using random number generators and chaotic maps.