A Priority Dropping Mechanism for the Multicast Delivery of Layered Video in a DiffServ Environment

Abstract:- In this paper a network-based, open loop mechanism for the multicast delivery of layered video streams is specified and experimentally evaluated for a DiffServ environment. Network oriented mechanisms for delivering layered multicast video offer simplicity and efficiency. Before the emergence of the Differentiated Services (DiffServ) framework a solid and feasible set of network mechanisms supporting such functionalities did not exist. The central idea is that once the application flow provides indications of how to scale in cases of losses, it is task of the network to manage packet drops according to their importance. The application defines priority layers within the video stream through packet marking, while the DiffServ is exploited to provide layer aware packet dropping together with a complete QoS provisioning framework. In this sense, each video stream is delivered in a single multicast group, without the need for extensive group management functions. During congestion at multicast tree nodes, packets corresponding to a lower priority layer are dropped first, thus protecting the most precious entities of the stream. In this context, congestion is handled at the node it occurs as soon as it occurs. Experiments with a DiffServ aware MPEG-4 streaming platform, were conducted over a laboratory platform validating the mechanism’s applicability. Experimental results are exposed. Key-Words:- Multicast, DiffServ, priority dropping, video, MPEG4IP, experiments