  WLAN devices have become a fundamental component of nowadays network
deployments. However, even though traditional networking applications run
mostly unchanged over wireless links, the actual interaction between these
applications and the dynamics of wireless transmissions is not yet fully
understood. An important example of such applications are bandwidth estimation
tools. This area has become a mature research topic with well-developed
results. Unfortunately recent studies have shown that the application of these
results to WLAN links is not straightforward. The main reasons for this is that
the assumptions taken to develop bandwidth measurements tools do not hold any
longer in the presence of wireless links (e.g. non-FIFO scheduling). This paper
builds from these observations and its main goal is to analyze the interaction
between probe packets and WLAN transmissions in bandwidth estimation processes.
The paper proposes an analytical model that better accounts for the
particularities of WLAN links. The model is validated through extensive
experimentation and simulation and reveals that (1) the distribution of the
delay to transmit probing packets is not the same for the whole probing
sequence, this biases the measurements process and (2) existing tools and
techniques point at the achievable throughput rather than the available
bandwidth or the capacity, as previously assumed.
