  We study the information freshness under three different source aware packet
management policies in a status update system consisting of two independent
sources and one server. The packets of each source are generated according to
the Poisson process and the packets are served according to an exponentially
distributed service time. We derive the average age of information (AoI) of
each source using the stochastic hybrid systems (SHS) technique for each packet
management policy. In Policy 1, the queue can contain at most two waiting
packets at the same time (in addition to the packet under service), one packet
of source 1 and one packet of source 2. When the server is busy at an arrival
of a packet, the possible packet of the same source waiting in the queue
(hence, source-aware) is replaced by the arrived fresh packet. In Policy 2, the
system (i.e., the waiting queue and the server) can contain at most two
packets, one from each source. When the server is busy at an arrival of a
packet, the possible packet of the same source in the system is replaced by the
fresh packet. Policy 3 is similar to Policy 2 but it does not permit preemption
in service, i.e., while a packet is under service all new arrivals from the
same source are blocked and cleared. Numerical results are provided to assess
the fairness between sources and the sum average AoI of the proposed policies.
