41314743
Resilient Network Coding in the Presence of Byzantine Adversaries
Network coding substantially increases network throughput. But since it involves mixing of information inside the network, a single corrupted packet generated by a malicious node can end up contaminating all the information reaching a destination, preventing decoding. This paper introduces the first distributed polynomial-time rate-optimal network codes that work in the presence of Byzantine nodes. We present algorithms that target adversaries with different attacking capabilities. When the adversary can eavesdrop on all links and jam zO links , our first algorithm achieves a rate of C - 2zO, where C is the network capacity. In contrast, when the adversary has limited snooping capabilities, we provide algorithms that achieve the higher rate of C - zO. Our algorithms attain the optimal rate given the strength of the adversary. They are information-theoretically secure. They operate in a distributed manner, assume no knowledge of the topology, and can be designed and implemented in polynomial-time. Furthermore, only the source and destination need to be modified; non-malicious nodes inside the network are oblivious to the presence of adversaries and implement a classical distributed network code. Finally, our algorithms work over wired and wireless networks.
52850401
Optimization Based Rate Control for Multicast with Network Coding
Recent advances in network coding have shown great potential for efficient information multicasting in communication networks, in terms of both network throughput and network management. In this paper, we address the problem of rate control at end-systems for network coding based multicast flows. We develop two adaptive rate control algorithms for the networks with given coding subgraphs and without given coding subgraphs, respectively. With random network coding, both algorithms can be implemented in a distributed manner, and work at transport layer to adjust source rates and at network layer to carry out network coding. We prove that the proposed algorithms converge to the globally optimal solutions for intra-session network coding. Some related issues are discussed, and numerical examples are provided to complement our theoretical analysis.
32811638
Timing of Software Replacement
Analogous to the replacement of an old machine, such as a car, replacing an aged softwitre may contain its escalating cost of maintenance. Prior research has assumed that increasing maintenance cost is due to the deterioration of the system maintainability. However, cost of maintenance depends also on the number of incoming maintenance requests. While software maintainability is determined by its complexity and development environment, number of maintenance requests is affected by the business environment. This distinction is significant in analyzing economic tradeoffs in software maintenance because replacement improves system maintainability but will not affect the number of maintenance requests. Unlike replacement of hardware, rewriting software takes an extended length of time, Thus, the old software must still be maintained before the new software is ready. We develop an economic model that considers the number of maintenance requests and the rewriting period explicitly. The model is an extension of Gode, Barua, and Mukhopadhyay (1990), which assumes a constant number of maintenance requests and instantaneous replacement. Our model allows us to draw some additional policy implications about software inaintenatice aild replacement. For instance, we show that in certain situations delaying a system replacement can be inore cost effective when the user environment changes more rapidly, contrary to our intuition. Moreover, it is shown that rewriting should begin earlier when the instantane(,us replacement assumption is relaxed.
14896427
Multilevel full-chip routing for the X-based architecture
As technology advances into the nanometer territory, the interconnect delay has become a first-order effect on chip performance. To handle this effect, the X-architecture has been proposed for high-performance integrated circuits. The X-architecture presents a new way of orienting a chip's microscopic interconnect wires with the pervasive use of diagonal routes. It can reduce the wire-length and via count, and thus improve performance and routability. Furthermore, the continuous increase of the problem size of IC routing is also a great challenge to existing routing algorithms. In this paper, we present the first multilevel framework for full-chip routing using the X-architecture. To take full advantage of the X-architecture, we explore the optimal routing for three-terminal nets on the X-architecture and develop a general X-Steiner tree algorithm based on the Delaunay triangulation approach for the X-architecture. The multilevel routing framework adopts a two-stage technique of coarsening followed by uncoarsening, with a trapezoid-shaped track assignment embedded between the two stages to assign long, straight diagonal segments for wirelength reduction. Compared with the state-of-the-art multilevel routing for the Manhattan architecture, experimental results show that our approach reduced wirelength by 18.7% and average delay by 8.8% with similar routing completion rates and via counts.
10011305
Group decision support systems: the cultural factor
Information technologies are socio-technical in that they consist of people (the human or "socio" side), non-human resources (the technical side), and the interaction between these two. They cannot be culture-free because the cultural factor associated with the human component will always be present. An information technology that is appropriate in one national culture is not necessarily appropriate in another. This paper reports an empirical study of group decision support systems (GDSS) conducted in Singapore. It describes the cultural differences between the USA and Singapore and discusses how these differences may affect the application of the existing body of GDSS findings to Singapore. This cross-cultural analysis of GDSS research findings is based on two studies carried out in the USA and Singapore. By adopting a very similar research design and employing the same GDSS software and research task, the authors are able to eliminate most of the contextual variables and the situational factors that might possibly account for the differences in research findings and explain these differences in terms of cultural factors. The key findings of the cross-cultural analysis are: 1. The anonymity feature of a GDSS allowed dominant members in Singaporean GDSS groups to openly express negative opinions about other group members' contributions, a behavior that would otherwise be culturally unacceptable. This, in turn, led to dissatisfaction and lower post-meeting consensus among group members. This phenomenon was not obvious in the American GDSS groups. 2. While structure facilitated expression of agreement or conflict in the American groups, it did not help Singaporean groups. Structure forced group members to be direct and open, a feature that is undesirable in Singaporean culture in which members prefer to express disagreement in an indirect manner so as to preserve harmony. 3. Use of a GDSS led to more even member influence in American groups but resulted in less even member influence in Singaporean groups. The anonymity feature of a GDSS allowed more equal member participation in both cultures. However, it also allowed a dominant member in a Singaporean group to gain influence without direct confrontation with other group members. This resulted in lower equality of influence in the Singaporean GDSS groups.