Topic cloud/en

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Cloud and Grid Computing,Peer to Peer Systems

Cloud Computing

Multicore-Aware Fault-Tolerant Task Scheduling for Data Center

In this topic, we proposed a task scheduling algorithm for a multicore processor system which reduces the recovery time in case of a single fail-stop failure of a multicore processor. Many of the recently developed processors have multiple cores on a single die, so that one failure of a computing node results in failure of many processors. In the case of a failure of a multicore processor, all tasks which have been executed on the failed multicore processor have to be recovered at once. The proposed algorithm is based on an existing checkpointing technique, and we assume that the state is saved when nodes send results to the next node. If a series of computations that depends on former results is executed on a single die, we need to execute all parts of the series of computations again in the case of failure of the processor. The proposed scheduling algorithm tries not to concentrate tasks to processors on a die. We designed our algorithm as a parallel algorithm that achieves O(n) speedup where n is the number of processors. We evaluated our method using simulations and experiments with four PCs. We compared our method with existing scheduling method, and in the simulation, the execution time including recovery time in the case of a node failure is reduced by up to 50% while the overhead in the case of no failure was a few percent in typical scenarios.

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  • Shohei Gotoda, Naoki Shibata and Minoru Ito : "Task scheduling algorithm for multicore processor system for minimizing recovery time in case of single node fault," Proceedings of IEEE International Symposium on Cluster Computing and the Grid (CCGrid 2012), pp.260-267, DOI:10.1109/CCGrid.2012.23, May 15, 2012. [ PDF ] [ SlideShare ]

Grid Computing

Distributed Market Broker Architecture for Resource Aggregation in Grid Computing Environments

In order to allow every user to extract aggregated computational power from idle PCs in the Internet, we propose a distributed architecture to achieve a market based resource sharing among users. The advantages of our proposed architecture are the following: (i) aggregated resources can be bought by one order, (ii) resource prices are decided based on market principles, and (iii) the load is balanced among multiple server nodes to make the architecture scalable w.r.t. the number of users. Through simulations, we have confirmed that the proposed method can mitigate the load at each server node to a great extent.

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  • Tamai, M., Shibata, N., Yasumoto, K. and Ito, M.: Distributed Market Broker Architecture for Resource Aggregation in Grid Computing Environments, Proc. of CCGrid2005, CD-ROM (2005) [ PDF ].

Peer to Peer Systems

MTcast: Robust and Efficient P2P-based Video Delivery for Heterogeneous Users

In this paper, we propose a new video delivery method called MTcast (Multiple Transcode based video multicast) which achieves efficient simultaneous video delivery to multiple users with different quality requirements by relying on user nodes to transcode and forward video to other user nodes. In MTcast, each user specifies a quality requirement for a video consisting of bitrate, picture size and frame rate based on the user’s environmental resource limitation. All users can receive video with the specified quality (or near this quality) along a single delivery tree. The main characteristics of MTcast are in its scalability, high user satisfaction degree in received video quality, short startup latency and robustness against node failure. Through simulations, we have confirmed that MTcast can achieve much higher user satisfaction degree and robustness against node failure than the layered multicast method.

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Cheat Detection for MMORPG on P2P Environments

In recent years, MMORPG has become popular. In order to improve scalability of game system, several P2P-based architectures have been proposed. However, in P2P-based gaming architecture, cheats by malicious players may more likely occur than traditional centralized architecture, since most of game data is handled by player nodes. In this paper, we propose a new method for detecting cheat in MMORPG which supposes typical P2P-based event delivery architecture where the entire game space is divided into subareas and a responsible node (selected from player nodes) delivers each event happened in the subarea to player nodes there every predetermined time interval called timeslot. In the proposed method, we introduce multiple monitor nodes (selected from player nodes) which monitor the game state and detect cheat when it happens. In order to allow monitor nodes to track the correct game state for the corresponding subarea, we let monitor nodes and a responsible node retain a random number seed and player nodes send their events not only to responsible node but also monitor nodes so that the monitor nodes and the responsible node can uniquely calculate the latest game state from the previous game state and game events which happened during the current timeslot. Either responsible node, monitor nodes or player nodes can detect cheat by comparing hash values of game state which are retained by those nodes periodically, and role back events happened since the last correct game state. Through experiments in PlanetLab, we show that our method achieves practical performance to detect cheats.


  • Shibata, N., Yasumoto, K., and Mori, M.: P2P Video Broadcast based on Per-Peer Transcoding and its Evaluation on PlanetLab?, Proc. of IASTED PDCS2007 (2007). [ PDF ]
  • Sun, T., Tamai, M., Yasumoto, M., Shibata, N., Ito, M. and Mori, M.: MTcast: Robust and Efficient P2P-based Video Delivery for Heterogeneous Users, Proc. of OPODIS2005 (2005). [ PDF ]
  • Izaiku, T. Yamamoto, S., Murata, Y., Shibata, N., Yasumoto, K. and Ito, M.: Cheat Detection for MMORPG on P2P Environments, Proc. of ACM NetGames2006, CD-ROM (2006). [ PDF ]