Buffer Occupancies in Tandem Networks with Size-Retaining Data Packets

In communication networks data packets are often transmitted via multiple hops on certain destined source-destination paths. The topological structure of such a scenario can be modeled by multi-node tandem queueing networks, but the standard independence assumption of queueing theory does not hold, that is, modeling the packet processing times at the successive nodes as independent and identically distributed random variables is not appropriate. While the packet sizes may vary among different packets, each single packet retains its size on its route through the network, also referred to as static packet size. For this realistic scenario, we study buffer occupancies in terms of the average number of packets buffered in each queue of a tandem network topology and investigate the model failure introduced by the independence assumption. In order to efficiently obtain accurate numerical results we use a recursive estimation scheme that does not require the independence assumption. Numerical studies reveal that buffer occupancies for size-retaining packets significantly differ from those obtained under the independence assumption, so that results obtained from analytical models working with the independence assumption should be taken with much care, in particular with regard to buffer dimensioning and related QoS guarantees.