  While age of Information (AoI) has gained importance as a metric
characterizing the fresh-ness of information in information-update systems and
time-critical applications, most previous studies on AoI have been theoretical.
In this chapter, we compile a set of recent works reporting API measurements in
real-life networks and experimental testbeds, and investigating practical
issues such as synchronization, the role of various transport layer protocols,
congestion control mechanisms, application of machine learning for adaptation
to network conditions, and device related bottlenecks such as limited
processing power.
