On the applicability of the on-off type approximation of the effective bandwidth function

Abstract

This paper reviews the applicability of simplified bandwidth requirement estimators that need only the mean and the peak rates of traffic flows as input, instead of the full statistical description of the traffic required by their original form. The estimators approximate the effective bandwidth function, the key component of the bandwidth requirement estimate, with the logarithmic moment generating function of an on-off source. It is demonstrated that this on-off type approximation has to be used with care as it results in a loss of information about the traffic streams. This is manifested in the reduction of the advanced bandwidth estimator method of the many sources asymptotics into the basic Chernoff-type technique. As a consequence bandwidth requirement estimators built on the onoff type approximation overlook the multiplexing gain occurring in the buffers, which results in overly conservative estimates close or equal to the peak rate when applied to traffic aggregates.