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Importance sampling is a variance reduction technique that is particularly well suited for simulating rare events and, more specifically, estimating rare event probabilities. Properly applied, it often results in tremendous efficiency improvements compared to direct simulation schemes, but it can also yield unbounded variance increase. Its efficiency and robustness critically rely on a suitable change...
Critical services in a telecommunication network should survive and be continuously provided even when undesirable events like sabotage, natural disasters, or network failures happen. The network survivability is quantified as defined by the ANSI T1A1.2 committee which is the transient performance from the instant an undesirable event occurs until steady state with an acceptable performance level...
In a telecommunication network it is essential to provide virtual connections between peering nodes with performance guarantees such as minimum throughput, maximum delay or loss. Critical services in telecommunication network should be continuously provided even when undesirable events like sabotage, natural disasters, or network failures happen. The design, construction and management of network...
Our society is heavily dependent on a wide variety of communication services. These services must be available even when undesirable events like sabotage, natural disasters, or network failures happen. The network survivability as defined by the ANSI T1A1.2 committee is the transient performance from the instant an undesirable event occurs until steady state with an acceptable performance level is...
Importance Sampling is a potentially powerful variance reduction technique to speed up simulations where the objective depends on the occurrence of rare events. However, it is crucial to find a change of the underlying probability measure yielding estimators with significantly reduced variance compared to direct estimators. In this paper, we present a new dynamic and adaptive method for this purpose...
Failures in the optical transmission equipment degrade the quality of service (QoS) provided by networks. In this paper, we consider intermittent faults and their impact on transceivers in optical network nodes. Our focus is on the service unavailability, i.e. the probability that the average capacity is below a specified guaranteed level. Since appropriate network models become huge and the unavailability...
This paper compares new empirical data from mobile and IP telephony with old measurements of the Plain Old Telephony Service (POTS). The results show the impact on traffic patterns from the changes in technology from fixed to mobile phones, reduction in speech quality from fixed phone to mobile and IP phones, changes in tariffs from usage based to flat-rate subscriptions, and introduction of alternative...
Packet losses can significantly degrade the quality of service (QoS) provided by networks. In this paper, asynchronous bufferless optical packet switched networks with multiple service classes and full wavelength conversion are considered. In case of a large number of wavelengths per fibre, packet losses become rare and thus intractable by means of conventional performance methodologies. We present...
This paper describes a trace driven, fast simulation approach applicable to deal with the performance evaluation of a multiplex of heterogeneous traffic streams with variable bit rate and long lived serial correlation offered routers in the Internet. A challenge with simulations of the Internet is the huge number of events that are needed for each event of interest, e.g. the loss or excessive delay...
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