  The emergence of new applications brings multi-class traffic with diverse
quality of service (QoS) requirements to wide area networks (WANs), motivating
research in traffic engineering (TE). In recent years, novel centralized and
hierarchical TE schemes have used heuristic or machine learning techniques to
orchestrate resources in closed systems such as datacenter networks. However,
these schemes suffer from long delivery delays and high control overhead when
applied to general WANs. To provide low-delay services, this paper proposes an
asynchronous multi-class traffic management (AMTM) scheme. We first establish
an asynchronous TE paradigm in which distributed nodes locally perform
low-complexity and low-delay traffic control based on link prices, and the TE
server updates link prices to eliminate decision conflicts between edge nodes.
By modeling the asynchronous TE paradigm as a control system with
non-negligible control loop delay, we find that the traditional pricing
strategy cannot simultaneously achieve a low packet loss rate and a low flow
delivery delay. To address this issue, we propose a new pricing strategy based
on the observations of virtual queues in intermediate nodes. We also present a
system design and related algorithms that utilize a dynamic step size mechanism
of link price update. Simulation results show that AMTM can effectively reduce
the end-to-end flow delivery delay.
