  We consider a communication system in which status updates arrive at a source
node, and should be transmitted through a network to the intended destination
node. The status updates are samples of a random process under observation,
transmitted as packets, which also contain the time stamp to identify when the
sample was generated. The age of the information available to the destination
node is the time elapsed since the last received update was generated. In this
paper, we model the source-destination link using queuing theory, and we assume
that the time it takes to successfully transmit a packet to the destination is
an exponentially distributed service time. We analyze the age of information in
the case that the source node has the capability to manage the arriving
samples, possibly discarding packets in order to avoid wasting network
resources with the transmission of stale information. In addition to
characterizing the average age, we propose a new metric, called peak age, which
provides information about the maximum value of the age, achieved immediately
before receiving an update.
