  Low Earth Orbit (LEO) satellite constellations combine great flexibility and
global coverage with short propagation delays when compared to satellites
deployed in higher orbits. However, the fast movement of the individual
satellites makes inter-satellite routing a complex and dynamic problem. In this
paper, we investigate the limits of unipath routing in a scenario where ground
stations (GSs) communicate with each other through a LEO constellation. For
this, we present a lightweight and topology-aware routing metric that favors
the selection of paths with high data rate inter-satellite links (ISLs).
Furthermore, we analyze the overall routing latency in terms of propagation,
transmission, and queueing times and calculate the maximum traffic load that
can be supported by the constellation. In our setup, the traffic is injected by
a network of GSs with real locations and is routed through adaptive multi-rate
inter-satellite links (ISLs). Our results illustrate the benefits of exploiting
the network topology, as the proposed metric can support up to 53% more traffic
when compared to the selected benchmarks, and consistently achieves the
shortest queueing times at the satellites and, ultimately, the shortest
end-to-end latency.
