  Packet traffic in complex networks undergoes the jamming transition from
free-flow to congested state as the number of packets in the system increases.
Here we study such jamming transition when queues are operated by the priority
queuing protocol and packets are guided by the dynamic routing protocol. We
introduce a minimal model in which there are two types of packets distinguished
by whether priority is assigned. Based on numerical simulations, we show that
traffic is improved in the congested region under the priority queuing
protocol, and it is worsened in the free-flow region. Also, we find that at the
transition point, the waiting-time distribution follows a power law, and the
power spectrum of traffic exhibits a crossover between two 1/f^a behaviors with
exponent a ~ 1 and 1 < a < 2 in low and high frequency regime, respectively.
This crossover is originated from a characteristic waiting time of packets in
the queue.
