Recently Internet P2P/overlay streaming has gained increasing popularity. While plenty of research has focused
on streaming performance study, it is not quite known yet on how to efficiently serve heterogeneous devices
that have different limitations on display size, color depth, bandwidth capacities, CPU and battery power, than
desktop computers. Although previous work1 proposes to reuse intermediate information (metadata) produced
during transcoding to facilitate runtime content adaption to serve heterogeneous clients by reducing total computing
load, unbalanced resource contribution may pre-maturely exhaust the limited power of mobile devices,
and adversely affect the performance of participating nodes and subsequently threaten the robustness of the
whole system. In this work, we propose a Dynamic Bi-Overlay Rotation (DOOR) scheme, in which, we further
consider resource consumption of participating nodes to design a dynamic rotation scheme that reacts to dynamic
situations and balances across multiple types of resources on individual nodes. Based on the computing load
and transcoding quality parameters obtained through real transcoding sessions, we drive large scale simulations
to evaluate DOOR. The results show clear improvement of DOOR over earlier work.
KEYWORDS: Internet, Detection and tracking algorithms, Electroluminescence, Systems modeling, Prototyping, Data transmission, Computing systems, Information security, Video, Legal
Both research and practice have shown that BitTorrent-like (BT) P2P systems are scalable and efficient for
Internet content distribution. However, existing BT systems are mostly used for distributing non-copyrighted or
pirated digital objects on the Internet. They have not been leveraged to distribute the majority of legal media
objects because existing BT systems are incapable of copyright protection. On the other hand, existing Digital
Rights Management (DRM) techniques are mainly based on a client-server model, and cannot be directly applied
to peer-to-peer based BT systems.
To leverage the efficiency and the scalability of BT systems for Internet content distribution, we propose a
novel scheme to enable DRM in existing BT systems without demanding infrastructure changes. In our scheme,
each file piece is re-encrypted at runtime before a peer uploads it to any other peer. Thus, the decryption keys
are unique for both different peers and difference pieces. In addition, any user can take part in the content
distribution while only legitimate users can access the plaintext of being distributed content. To evaluate
the performance of our proposed scheme, we have conducted experiments on PlanetLab with an implemented
prototype and compared with the original BT system. The results show that our proposed scheme introduces
less than 10% of system throughput degradation for copyright protection when compared to BT systems without
copyright protection.
In general, existing segment-based caching strategies target one of the following two performance objectives: (1) reducing client startup delay by giving a high priority to cache the beginning segments of media objects, or (2) reducing server traffic by caching popular segments of media objects. Our previous study has shown that the approach targeting the second objective has several advantages over the first one. However, we have also observed that the effort of improving server traffic reduction can increase client startup delay, which may potentially offset the overall performance gain. Little work so far has considered these two objectives in concert. In this paper, we first build an analytical model for these two types of typical segment-based caching approaches. The analysis on the model reveals the nature of the trade-off between two performance objectives and the bounds of each are given under certain circumstances. To provide a feasible way to evaluate different strategies, we propose a new comprehensive performance metric based on the analysis. To understand this performance trade-off, we restructure the adaptive-lazy segmentation strategy with a heuristic replacement policy to improve overall performance. The evaluation results confirm our analysis and show the effectiveness of our proposed new performance metric.
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