  Given the rapid increase in traffic, greater demands have been put on
high-speed switching systems. Such systems have to simultaneously meet several
constraints, e.g., high throughput, low delay and low complexity. This makes it
challenging to design an efficient scheduling algorithm, and has consequently
drawn considerable research interest. However, previous results either cannot
provide a $100\%$ throughput guarantee without a speedup, or require a complex
centralized scheduler. In this paper, we design a {\it distributed} $100 \%$
throughput algorithm for crosspoint buffered switches, called DISQUO, with very
limited message passing. We prove that DISQUO can achieve $100\%$ throughput
for any admissible Bernoulli traffic, with a low time complexity of $O(1)$ per
port. To the best of our knowledge, it is the first distributed algorithm that
can provide a $100\%$ throughput for a crosspoint buffered switch.
