  Latency is becoming a key factor of performance for Internet applications and
has triggered a number of changes in its protocols. Our work revisits the
impact on latency of address family selection in dual-stack hosts. Through RIPE
Atlas measurements, we analyse the address families latency difference and
establish two requirements based on our findings for a latency-focused
selection mechanism. First, the address family should be chosen per
destination. Second, the choice should be able to evolve over time dynamically.
We propose and implement a solution formulated as an online learning problem
balancing exploration and exploitation. We validate our solution in simulations
based on RIPE Atlas measurements, implement and evaluate our prototype in four
access networks using Chrome and popular web services. We demonstrate the
ability of our solution to converge towards the lowest-latency address family
and improve the latency of transport connections used by applications.
