International audienceIndiscriminated packet discards strongly degrade the quality perceived by end users of MPEG video transmissions. This paper investigates different Quality of Service (QoS) schemes and the tradeoffs of jointly adopting such schemes to improve the delivery quality of an MPEG stream. From an analytical model, we evaluate the impact of frame losses on the quality of MPEG streams and on the waste of network resources. Our assessment considers issues such as the use of redundancy by applying a Forward Error Correction (FEC) scheme to tolerate losses, the changing of the compression factor in MPEG encoding, the unequal protection of MPEG frames in a Differentiated Services environment, and how to evaluate the impact of network losses onto application quality. Results provide predicted bounds on the quality to be expected by end users as well as guidelines on how to take the best advantage from the joint adoption of the investigated QoS schemes

Reliable routing of packets in a Mobile Ad Hoc Network (MANET) has always been a major concern. The open medium and the susceptibility of the nodes of being fault-prone make the design of protocols for these networks a challenging task. The faults in these networks, which occur either due to the failure of nodes or due to reorganization, can eventuate to packet loss. Such losses degrade the performance of the routing protocols running on them. In this paper, we propose a routing algorithm, named as learning automata based faulttolerant routing algorithm (LAFTRA), which is capable of routing in the presence of faulty nodes in MANETs using multipath routing. We have used the theory of Learning Automata (LA) for optimizing the selection of paths, reducing the overhead in the network, and for learning about the faulty nodes present in the net- S. Misra ( ) SchoolA learning automata-based fault-tolerant routing algorithm 5 work. The proposed algorithm can be juxtaposed to any existing routing protocol in a MANET. The results of simulation of our protocol using network simulator 2 (ns-2) shows the increase in packet delivery ratio and decrease in overhead compared to the existing protocols. The proposed protocol gains an edge over FTAR, E2FT by nearly 2% and by more than 10% when compared with AODV in terms of packet delivery ratio with nearly 30% faulty nodes in the network. The overhead generated by our protocol is lesser by 1% as compared to FTAR and by nearly 17% as compared to E2FT when there are nearly 30% faulty nodes.

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Abstract-The possibility of using flexible and cost-efficient commodity hardware instead of expensive custom hardware has triggered wide interest in software routers. Performance measurement and simulation are important approaches for identifying bottlenecks of such systems to predict and improve the performance. We measure the performance of software routers using current multi-core hardware architectures. We introduce an innovative and validated node model for intra-node resource contention and realized a resource management extension for the widely-used network simulator ns-3 which allows to evaluate and predict the performance of current and future software router architectures.

Abstract-Most systems connected to the Internet are general purpose machines (except specialized routers and switches in the network core) that handle packet processing in software. Even in the network core, there is a trend towards packet processing in software, e.g. using OpenFlow or virtual switches. While packet processing in software is flexible and offers many capabilities, it also represents a challenge to evaluate, optimize, or predict the performance of such complex systems. This makes it hard to evaluate the networking performance of servers, end user hosts, or home routers. We present a study that investigates the packet latency caused by packet processing in the Linux network stack. We develop a simulation model in ns-3 for packet processing via the Linux network stack that helps understanding of its performance implications. We validate our simulation model based on measurements with nanosecond accuracy and software profiling.