  Internet performance is tightly related to the properties of TCP and UDP
protocols, jointly responsible for the delivery of the great majority of
Internet traffic. It is well understood how these protocols behave under FIFO
queuing and what the network congestion effects. However, no comprehensive
analysis is available when flow-aware mechanisms such as per-flow scheduling
and dropping policies are deployed. Previous simulation and experimental
results leave a number of unanswered questions. In the paper, we tackle this
issue by modeling via a set of fluid non-linear ODEs the instantaneous
throughput and the buffer occupancy of N long-lived TCP sources under three
per-flow scheduling disciplines (Fair Queuing, Longest Queue First, Shortest
Queue First) and with longest queue drop buffer management. We study the system
evolution and analytically characterize the stationary regime: closed-form
expressions are derived for the stationary throughput/sending rate and buffer
occupancy which give thorough understanding of short/long-term fairness for TCP
traffic. Similarly, we provide the characterization of the loss rate
experienced by UDP flows in presence of TCP traffic.
