  CHOKe is a simple and stateless active queue management (AQM) scheme. Apart
from low operational overhead, a highly attractive property of CHOKe is that it
can protect responsive TCP flows from unresponsive UDP flows. Particularly,
previous works have proven that CHOKe is able to bound both bandwidth share and
buffer share of (a possible aggregate) UDP traffic (flow) on a link. However,
these studies consider, and pertain only to, a steady state where the queue
reaches equilibrium in the presence of many (long-lived) TCP flows and an
unresponsive UDP flow of fixed arrival rate. If the steady state conditions are
perturbed, particularly when UDP traffic rate changes over time, it is unclear
whether the protection property of CHOKe still holds. Indeed, it can be
examined, for example, that when UDP rate suddenly becomes 0 (i.e., flow
stops), the unresponsive flow may assume close to full utilization in sub-RTT
scales, potentially starving out the TCP flows. To explain this apparent
discrepancy, this paper investigates CHOKe queue properties in a transient
regime, which is the time period of transition between two steady states of the
queue, initiated when the rate of the unresponsive flow changes. Explicit
expressions that characterize flow throughputs in transient regimes are
derived. These results provide additional understanding of CHOKe, and give some
explanation on its intriguing behavior in the transient regime.
