Providing Proportional Loss Differentiation over Bandwidth on Demand Satellite Networks

Next generation Internet requires the capability of providing quality of service (QoS) with service differentiation. Broadband satellite networks as an integral part of the global broadband network infrastructure are moving towards the same goal of providing service differentiation. Due to the unique properties of the space environment, providing service differentiation in satellite networks has additional challenges such as long propagation delay. In this paper, we present an innovative profile-based probabilistic dropping scheme for the provision of relative loss differentiation in a geostationary (GEO) bandwidth on demand (BoD) satellite network which follows the DVB-RCS standard, approved and published by ETSI for interactive broadband satellite network. The network is structured to support a finite number of ordered service classes. We adopt the proportional differentiated service (PDS) model which strikes a balance between the strict QoS guarantee of Integrated Services (IntServ) and softer QoS guarantee of Differentiated Services (DiffServ) to provide proportional loss differentiation to different priority classes. Our scheme controls the loss rates by computing the appropriate packet drop probability based on the congestion level within each satellite terminal (ST) independent of operating condition of other terminals and without requiring a central controller or monitor. Unlike previous proposals designed for terrestrial and wireless networks where the correct differentiation is only achieved locally on per-hop basis (i.e. the queues for different classes must be co-located in a node sharing a common buffer and communication channel), our scheme is able to maintain network-wide proportional loss even though the queues are physically distributed. Additionally, in the design of our solution, we ensure simplicity of the algorithm to minimize overhead incurred in the satellite network and also intra- and inter-node differentiation consistency. We extend the ns-2 simulator with the BoD capability analogous to the DVB-RCS system in which STs first request for resources (i.e. time slots) and only start transmitting packets following the reception of burst time plan (BTP). We implement our loss differentiation algorithm and attach it to each ST. Simulation results show that the scheme is able to achieve the PDS model in a heterogeneous ST environment. Our results also suggest that the predictability property of the PDS model may be violated if the service provider configures the performance gaps between service classes to be too close. However, our scheme can fully achieve the controllability property of the model.

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