Abstract-Since the identification of long-range dependence in network traffic ten years ago, its consistent appearance across numerous measurement studies has largely discredited Poissonbased models. However, since that original data set was collected, both link speeds and the number of Internet-connected hosts have increased by more than three orders of magnitude. Thus, we now revisit the Poisson assumption, by studying a combination of historical traces and new measurements obtained from a major backbone link belonging to a Tier 1 ISP. We show that unlike the older data sets, current network traffic can be well represented by the Poisson model for sub-second time scales. At multi-second scales, we find a distinctive piecewise-linear non-stationarity, together with evidence of long-range dependence. Combining our observations across both time scales leads to a time-dependent Poisson characterization of network traffic that, when viewed across very long time scales, exhibits the observed long-range dependence. This traffic characterization reconciliates the seemingly contradicting observations of Poisson and long-memory traffic characteristics. It also seems to be in general agreement with recent theoretical models for large-scale traffic aggregation.

Self-similarity and scaling phenomena have dominated Internet traffic analysis for the past decade. With the identification of long-range dependence (LRD) in network traffic, the research community has undergone a mental shift from Poisson and memory-less processes to LRD and bursty processes. Despite its widespread use, though, LRD analysis is hindered by our difficulty in actually identifying dependence and estimating its parameters unambiguously.The authors outline LRD findings in network traffic and explore the current lack of accuracy and robustness in LRD estimation. In addition, the authors present recent evidence that packet arrivals appear to be in agreement with the Poisson assumption in the Internet core.

In wireless cellular networks, in order to ensure that ongoing calls are not dropped while the owner mobile stations roam among cells, handoff calls may be admitted with a higher priority as compared with new calls. Since the wireless bandwidth is scarce and therefore precious, efficient schemes which allow a high utilization of the wireless channel, while at the same time guarantee the QoS of handoff calls are needed. In this paper, we propose a new scheme that uses GPS measurements to determine when channel reservations are to be made. It works by sending channel reservation request for a possible handoff call to a neighboring cell not only based on the position and orientation of that call's mobile station, but also depends upon the relative motion of the mobile station with respect to that target cell. The scheme integrates threshold time and various features of prior schemes to minimize the effect of false reservations and to improve the channel utilization of the cellular system. Simulation results show that our scheme performs better in almost all typical scenarios than prior schemes.

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