Synchronized multi-hop scheduling for real-time traffic on SDNs

Although supporting Quality of Service (QoS) on the traditional Internet has been extremely challenging, QoS supports are still highly desirable for many real-time applications. While existing QoS schemes often show poor scalability, low efficiency, and limited QoS supports, the fast development of Software Define Networks (SDNs) provides new opportunities to address QoS support with its centralized network control. In this paper, we propose a synchronized architecture to exploit the unique features of SDNs without conducting static reservations. Assume all routers are synchronized in time, we can precisely determine the upstream delay of a packet at a router. Meanwhile, because we also know the fairly accurate resource availability on its downstream routers (from the SDN controller), we can determine the packet's service priority on its current router based on its end-to-end (e2e) delay requirement and the expected delay that the packet may experience in its downstream. In particular, we propose a synchronized multi-hop scheduling (SMS) scheme to exploit both upstream information and downstream resource availability to speed up or slow down a packet. This is completely different from all existing per-hop or multi-hop schemes that mostly utilize upstream information. Furthermore, we propose to selectively drop a packet that is unlikely to meet its deadline. Our simulation results show that the proposed scheme outperforms existing schemes in packet missing rates.