Shared versus Dedicated Buffers for Real-Time Traffic in Optical Routers with Very Small Buffers

Abstract — When TCP and real-time (UDP) traffic multiplex at an optical packet router with very small buffers (less than 50 KiloBytes), we recently showed that UDP packet losses can increase with buffer size. In this paper we explore if this anomalous loss behaviour can be alleviated by dedicating (pre-allocating) buffers to UDP traffic. We show that while dedicating buffers to UDP traffic protects it from TCP’s greedy behaviour, it can also reduce the overall efficiency of buffer usage. Our simulations using trace data indicate that buffer sharing yields better performance when the total buffer capacity is below a critical value of around 20 KiloBytes, and dedicated buffers are desirable otherwise. Our study informs designers and operators of optical packet switched networks with very small buffering capacity of the relative merits of shared and dedicated buffers for real-time traffic. I