Performance Analysis of Packet Encapsulation and Aggregation

In an attempt to increase data throughput, many modern data transmission protocols provide capabilities for aggregating transmitted data fragments into larger packets at the time of encapsulation in a particular OSI layer. The decision and ability to aggregate packets into a single frame can have significant impact on the performance of the communication system. The impact can be even more substantial when the system operates under a heavy load. In this paper, we present a queuing model which describes a packet encapsulation and aggregation process. We assume Poisson arrivals and phase-type service time distributions for the transmitted packets. Using the proposed queuing model, we provide analysis of the end-to-end delay of a packet transmitted by the system. We verify analytical results with a simulation model of the system. Based on results of experiments with the analytical model, we provide the maximum number of packets in a single frame for which packet aggregation minimizes the average total delay of a packet for various system loads and sizes of the packet header. It is numerically shown that when the load is high, the higher the variability of the packet service time, the higher the maximum allowed number of packets in the frame should be to achieve the minimum average total packet delay. On the other hand, the impact of the variability of the packet service time is insignificant when the system load is moderate or low.