Nowadays, dynamic service management frameworks are proposed to ensure end-to-end QoS. To achieve this goal, it is necessary to manage Service Level Agreements (SLAs), which specify quality parameters of the services operation such as availability and performance. This work is focused on the evaluation of Video-on-Demand (VoD) services in end-to-end QoS scenarios. Based on a straightforward Markov Chain, Markov-Reward Chain (MRC) models are developed in order to obtain various QoS measures of an adaptive VoD service. The MRC model has a clear understanding with the design and operation of the VoD system. In this way, new design options can be proposed and be easily evaluated. To compute performability measures of the MRC model, the randomization method is employed. Predicted model results fit well to the ones taken from a real video-streaming testbed.

In this paper, we review the workflow of the channel and physical layer modules in VANET simulations and briefly survey some of the most used propagation and packet error models in network simulators for this kind of networks. Through numerical simulations, we compare these propagation models working with a realistic and straightforward packet error model. Our results indicate that there is not a propagation model more conservative than the others and that a model is conservative or not depending on the channel capacity. Furthermore, different propagation models specifically designed for VANETs obtain very close results in channels with intermediate capacities.Keywords-Vehicular ad hoc networks (VANET), network simulators, channel modeling.

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Abstract. The provision of end-to-end Quality of Service (QoS) for multimedia services over IP-based networks is already an open issue. To achieve this goal, service providers need to manage Service Level Agreements (SLAs), which specify parameters of the services operation such as availability and performance. Additional mechanisms are needed to quantitatively evaluate the user-level SLA parameters. This work is focused on the evaluation and assessment of different design options of an adaptive VoD service providing several classes of users and fulfilling the SLA commitments. Based on a straightforward Markov Chain, Markov-Reward Chain (MRC) models are developed in order to obtain various QoS measures of the adaptive VoD service. The MRC model has a clear understanding with the design and operation of the VoD system.