First-come-first-served packet dispersion and implications for TCP

We study the packet dispersion phenomenon that a traffic flow experiences when it passes through a router. We show that when there are competing flows and the router schedules packets first-come-first-served (FCFS), the dispersion is not described well by the bottleneck spacing effect. We therefore introduce the term FCFS-spacing effect. We also show that for a router implementing weighted fair queuing, dispersion is due either to the bottleneck spacing effect or the FCFS spacing effect. The results from real measurements and simulations corroborate each other. Finally, we discuss the implications of FCFS packet dispersion on TCP's self-clocking mechanism.