  We provide an analytical study of the impact of packet skipping and
opportunistic network coding on the timely communication of messages through a
single network element. In a first step, we consider a single-server queueing
system with Poisson arrivals, exponential service times, and a single buffer
position. Packets arriving at a network node have a fixed deadline before which
they should reach the destination. To preserve server capacity, we introduce a
thresholding policy, based on remaining time until deadline expiration, to
decide whether to serve a packet or skip its service. The obtained goodput
improvement of the system is derived, as well as the operating conditions under
which thresholding can enhance performance. Subsequently, we focus our analysis
on a system that supports network coding instead of thresholding. We
characterize the impact of network coding at a router node on the delivery of
packets associated with deadlines. We model the router node as a queueing
system where packets arrive from two independent Poisson flows and undergo
opportunistic coding operations. We obtain an exact expression for the goodput
of the system and study the achievable gain. Finally, we provide an analytical
model that considers both network coding and packet skipping, capturing their
joint performance. A comparative analysis between the aforementioned approaches
is provided.
