Coscheduling has been gained a resurgence of interest as an effective technique to enhance the performance of parallel applications in multi-programmed clusters. However, existing coscheduling schemes do not adequately handle priority boost conflicts, leading to significantly degraded performance. To address this problem, in our previous study, we devised a novel algorithm that reorders the scheduling sequence of conflicting processes based on the rescheduling latency of their correspondents in remote nodes. In this paper, we exhaustively explore the design issues and implementation details of our contention-aware coscheduling scheme over Myrinet-based cluster system. We also practically analyze the impact of various system parameters and job characteristics on the performance of all considered schemes on a heterogeneous Linux cluster using a generic coscheduling framework. The results show that our approach outperforms existing schemes (by up to 36.6% in avg. job response time), reducing both boost conflict ratio and overall message delay.

In this paper, we propose the window-based congestion control mechanism using explicit feedback in TCP over ATM ABR service. The proposed scheme is based on notifying the network status as the free buffer length at the congested link to the IP station which informs the window rate by modifying the receivers' advertised window field in TCP ACK returning to the source. Results from simulation show that our proposed algorithm improves the fairness and stability of TCP connections in general network environments even if they have the different round trip times.

IEEE 802.11 MAC is the most commonly used MAC layer protocol in multi-hop ad hoc networks. When the network load becomes heavy, the throughput performance of IEEE 802.11 MAC is decreased because of the high collision rates and the low spatial reuse of the channel. In this letter, we analyze the throughput of multi-hop ad hoc networks and propose a supervisory control framework to maximize the throughput.

This paper describes a max-min fair rate allocation scheme in multicast networks based on the supervisory control framework for discrete event systems. Based on the discrete event model of multicast networks, we design a supervisor to guarantee the max-min fair allocation of bandwidth. Analysis and simulations are used to show that the controlled networks guarantee the max-min fair sharing with a low message exchange overhead and fast convergence time.

In this letter, we suggest APMAC (Adaptive Power Control MAC) for wireless ad hoc networks. APMAC is based on the single channel environment and improves the throughput and the energy efficiency simultaneously. Furthermore, the APMAC prevents the unfair channel starvation among the transmission pairs. We verify the performance of the APMAC through simulations.

We discuss a new high performance computing service (HPCS) platform that has been developed to provide domain-neutral computing service under the governmental support from “EDucation-research Integration through Simulation On the Net” (EDISON) project. With a first focus on technical features, we not only present in-depth explanations of the implementation details, but also describe the strengths of the EDISON platform against the successful nanoHUB.org gateway. To validate the performance and utility of the platform, we provide benchmarking results for the resource virtualization framework, and prove the stability and promptness of the EDISON platform in processing simulation requests by analyzing several statistical datasets obtained from a three-month trial service in the initiative area of computational nanoelectronics. We firmly believe that this work provides a good opportunity for understanding the science gateway project ongoing for the first time in Republic of Korea, and that the technical details presented here can be served as an useful guideline for any potential designs of HPCS platforms.

In this letter, we suggest a rate-based supervisory congestion control scheme for the ad hoc networks that use TCP as the transport protocol. This scheme makes it possible for the TCP sender to distinguish the causes of packet loss. In addition, this scheme guarantees the fair sharing of the available bandwidth among the connections. We show the reliability of our scheme by using the supervisory control framework and simulations confirm the effectiveness of our scheme.

Explicit Congestion Notification (ECN) supports the binary congestion information of the network for adjusting the window size. However, this results in the oscillation of the window size and the queue length due to the insufficient congestion information. In this paper, we propose the window-based congestion control mechanism with the modified ECN mechanism. The proposed scheme is based on extracting the network status from the consecutive binary congestion information provided by ECN. From the explicit network information, we estimate the allowable window size to achieve better performance. Through the simulations, the effectiveness of the proposed algorithm is shown as compared with the ECN algorithm.

In addition to high bit error rates, large and sudden variations in delay often occur in wireless cellular networks. The delay can be several times the typical round-trip time, which can cause the spurious timeout. In this letter, we propose a new window control algorithm to improve TCP performance in wireless cellular networks with large delay variation and high bit error rates. Simulation results illustrate that our proposal improves the performance of TCP in terms of fairness and link utilization.