  FIFO is perhaps the simplest scheduling discipline. For single-class FIFO,
its delay guarantee performance has been extensively studied: The well-known
results include a stochastic delay bound for $GI/GI/1$ by Kingman and a
deterministic delay bound for $D/D/1$ by Cruz. However, for multiclass FIFO,
few such results are available. To fill the gap, we prove delay bounds for
multiclass FIFO in this work, considering both deterministic and stochastic
cases. Specifically, delay bounds are presented for multiclass D/D/1, GI/GI/1
and G/G/1. In addition, examples are provided for several basic settings to
demonstrate the obtained bounds in more explicit forms, which are also compared
with simulation results.
