Csaba Kiraly

On the Optimal Scheduling of Streaming Applications in Unstructured Meshes

Unstructured, chunk-based P2P streaming (TV and Video) systems are becoming popular and are subject of intense research. Chunk and peer selection strategies (or scheduling) are among the main driver of performance. This work presents the formal proof that there exist a distributed scheduling strategy which is able to distribute every chunk to all N peers in exactly ***log2 (N ) *** + 1 steps. Since this is the minimum number of steps needed to distribute a chunk, the proposed strategy is optimal. Such a strategy is implementable and an entire class of deadline-based schedulers realize it. We show that at least one of the deadline-based schedulers is resilient to the reduction of the neighborhood size down to values as small as log2 (N ). Selected simulation results highlighting the properties of the algorithms in realistic scenarios complete the paper.

Architecture of a network-aware P2P-TV application: the NAPA-WINE approach

Peer to Peer streaming (P2P-TV) applications have recently emerged as cheap and efficient solutions to provide real time streaming services over the Internet. For the sake of simplicity, typical P2P-TV systems are designed and optimized following a pure layered approach, thus ignoring the effect of design choices on the underlying transport network. This simple approach, however, may constitute a threat for the network providers, due to the congestion that P2P-TV traffic can potentially generate. In this article, we present and discuss the architecture of an innovative, network cooperative P2PTV application that is being designed and developed within the STREP Project NAPA WINE1 Our application is explicitly targeted to favor cooperation between the application and the transport network layer.

Effects of P2P Streaming on Video Quality

P2P TV distribution is going commercial, and the video quality delivered to users becomes of the utmost importance. However, the impact of P2P distribution on the video quality is not completely understood yet, especially in live streaming situations. This work addresses the impact of P2P distribution when the delay of the playout is limited, as it must be in any true live TV service. A methodology for the evaluation (using standard objective video quality metrics) is proposed, showing that different ways of grouping frames in chunks for the distribution can lead to very different quality when the system is overloaded.

RPL: The Routing Standard for the Internet of Things... Or Is It?

RPL, the IPv6 Routing Protocol for low-power and lossy networks, is considered the de facto routing protocol for the Internet of Things (IoT). Since its standardization, RPL has contributed to the advancement of communications in the world of tiny, embedded networking devices by providing, along with other standards, a baseline architecture for IoT. Several years later, we analyze the extent to which RPL has lived up to the expectations defined by the IETF requirements, and tie our analysis to current trends, identifying the challenges RPL must face to remain on the forefront of IoT technology.

Traffic Flow Confidentiality in IPsec: Protocol and Implementation

Traffic Flow Confidentiality (TFC) mechanisms are techniques devised to hide/masquerade the traffic pattern to prevent statistical traffic analysis attacks. Their inclusion in widespread security protocols, in conjunction with the ability for deployers to flexibly control their operation, might boost their adoption and improve privacy of future networks. This paper describes a TFC protocol integrated, as a security protocol, in the IPsec security architecture. A Linux-based implementation has been developed, supporting a variety of perpacket treatments (padding, fragmentation, dummy packet generation, and artificial alteration of the packet forwarding delay), in an easily combinable manner. Experimental results are reported to demonstrate the flexibility and the effectiveness of the TFC implementation.

Is RPL Ready for Actuation? A Comparative Evaluation in a Smart City Scenario

Low-power wireless actuation is attracting interest in many domains, yet it is significantly less investigated than its sensing counterpart, especially in large-scale scenarios. As a consequence, guidelines about which protocol, among the few existing ones, is best suited to a given scenario are generally lacking.

Design and implementation of a generic library for P2P streaming

Practical implementation of new P2P streaming systems requires a lot of coding and is often tedious and costly, slowing down the technology transfer from the research community to real users. GRAPES aims at solving this problem by providing a set of open-source components conceived as basic building blocks for building new P2P streaming applications which have in mind the savvy usage of network resources as well as the Quality of Experience of final users. GRAPES is designed to be usable in different environments and situations, to have a minimum set of pre-requisites and dependencies, and not to impose any particular constraints on applications using it. Our experience shows that GRAPES allows the rapid development of P2P streaming applications by writing a small amount of glue code to connect the desired functionalities. Some examples (including some simple P2P streamers) are also discussed as a means to show code usage.

SSSim: a Simple and Scalable Simulator for P2P Streaming Systems

This paper describes SSSim, the Simple and Scalable Simulator for P2P streaming systems. SSSim is designed for performance and scalability, and allows the simulation of the diffusion of a very large number of chunks over large number of peers in reasonable times. This result has been obtained by optimising the simulator for recurrent workloads and minimizing the memory footprint. After describing the simulators structure and the most important design decisions, the paper presents some experimental results comparing the simulation times of SSSim and a traditional simulator.

Robust Scheduling of Video Streams in Network-Aware P2P Applications

P2P TV and video streaming are among the most bandwidth-hungry applications running over the Internet. One of the main reasons is that the scheduling of information transfer between peers is extremely aggressive and does not take network characteristics into account. Moreover, schedulers are not designed to be robust and configurable, so that their performance is greatly affected by networking conditions. This work first analyzes the impact of network heterogeneity on the streaming performance and then proposes a novel, robust, configurable, network-aware scheduler that outperforms the other schedulers in all networking scenarios.

D-RPL: Overcoming memory limitations in RPL point-to-multipoint routing

RPL, the IPv6 Routing Protocol for Low-Power and Lossy Networks, supports both upward and downward traffic. The latter is fundamental for actuation, for queries, and for any bidirectional protocol such as TCP, yet its support is compromised by memory limitation in the nodes. In RPL storing mode, nodes store routing entries for each destination in their sub-graph, limiting the size of the network, and often leading to unreachable nodes and protocol failures. We propose here D-RPL, a mechanism that overcomes the scalability limitation by mending storing mode forwarding with multicast-based dissemination. Our modification has minimal impact on code size and memory usage. D-RPL is activated only when memory limits are reached, and affects only the portion of the traffic and the segments of the network that have exceeded memory limits. We evaluate our solution using Cooja emulation over different synthetic topologies, showing a six-fold improvement in scalability.