  In this paper, we examine a system where status updates are generated by a
source and are forwarded in a First-Come-First-Served (FCFS) manner to the
monitor. We consider the case where the server has other tasks to fulfill, a
simple example being relaying the packets of another stream. Due to the
server's necessity to go on vacations, the age process of the stream of
interest becomes complicated to evaluate. By leveraging specific queuing theory
tools, we provide a closed form of the average age for both streams which
enables us to optimize the generation rate of packets belonging to each stream
to achieve the minimum possible average age. The tools used can be further
adopted to provide insights on more general multi-hop scenarios. Numerical
results are provided to corroborate the theoretical findings and highlight the
interaction between the two streams.
