  This letter analyzes the Low-latency Region (LLR) of a best-effort link
(i.e., no traffic differentiation, and first come first serve scheduling)
carrying both delay-sensitive (DS) streaming and non-delay-sensitive (NDS)
background traffic. Moreover, inside the LLR, we show it exists a proportional
fair arrival rate allocation for both the DS and NDS traffic streams. This
optimal operating point results from maximizing a simple throughput-delay
trade-off that considers the NDS traffic load, and the mean delay of the DS
packets. To show how the presented trade-off could be used to allocate NDS
traffic in a realistic scenario, we use Google Stadia traffic traces to
generate the DS flow. Results from this use-case confirm that the
throughput-delay trade-off also works regardless the distribution of the packet
arrival and packet service times.
