Scalable QoS for XCAST Using Differentiated Services Architecture

Explicit multiunicast (XCAST) has been proposed as a multicasting scheme with complementary scaling properties which can solve the scalability problems of conventional IP Multicast. XCAST is suitable for videoconferencing, online games and IPTV. This paper deals with QoS provisioning in XCAST networks using Differentiated Services (DiffServ). We show that integration of DiffServ in XCAST is a non-trivial problem due to inherent architectural differences between XCAST and DiffServ. We then propose a scheme called QS-XCAST that uses dynamic DSCPs to adapt to the heterogeneity of receivers in an XCAST network. We also provide an algorithm for harmonizing the receiver-driven and sender-driven QoS approaches between XCAST and DiffServ thereby determining the correct DSCP-PHB for all links in an XCAST network. By simulating using OMNeT++ we evaluate QS-XCAST using four metrics: throughput, average per-hop-delay, link utilization and forwarding fairness to other traffic in the network. Our solution eliminates DSCP confusion and collusion attack problems to which naive XCAST QoS provisioning is vulnerable. It also offers a more efficient bandwidth utilization, better forwarding fairness and less traffic load compared to the existing XCAST.