14678674
Enhanced intranet management in a DHCP-enabled environment
The DHCP (dynamic host configuration protocol) is widely deployed in resource allocation and intranet management. However the DHCP mechanism is not mandatory and the DHCP server can neither force DHCP clients to release their leases, nor enforce cooperation from externally configured hosts that are DHCP-unaware. Although new DHCP options such as DHCP reconfigure extension have been proposed, the basic problems inherent in DHCP mechanism cannot be solved without first strengthening its operations. In the paper a DHCP-based infrastructure for intranet management is proposed by combining the resource allocation functions of the DHCP server with the packet filtering features of MAC (Medium Access Control) bridges such as Ethernet switches and wireless access points. DHCP clients and DHCP-unaware hosts that do not abide by the DHCP mechanism or our management policy will be denied network accesses by MAC bridges. Resource allocation and access control can be integrated and local configuration conflicts can be reduced to the minimum.
13018290
Towards Web Mining of Query Translations for Cross-Language Information Retrieval in Digital Libraries
This paper proposes an efficient client-server-based query translation approach to allowing more feasible implementation of cross-language information retrieval (CLIR) services in digital library (DL) systems. A centralized query translation server is constructed to process the translation requests of cross-lingual queries from connected DL systems. To extract translations not covered by standard dictionaries, the server is developed based on a novel integration of dictionary resources and Web mining methods, including anchor-text and search-result methods, which exploit huge amounts of multilingual and wide-scoped Web resources as live bilingual corpora to alleviate translation difficulties, and have been proven particularly effective for extracting multilingual translation equivalents of query terms containing proper names or new terminologies. The proposed approach was implemented in a query translation engine called LiveTrans, which has been shown its feasibility in providing efficient English-Chinese CLIR services for DL.
14749331
Early measurements of a cluster-based architecture for P2P systems
Peer-to-peer applications such as Napster [4], Freenet [1], and Gnutella [2], [7] have gained much attention recently. These applications are mainly designed and used for largescale sharing of MP3 files. In such systems, end-hosts self-organize into an overlay network and share content with each other. Compared to the traditional client-server model, files are served in a distributed manner and replicated among the network on demand. Since hosts participating in peer-to-peer (P2P) networks also devote some computing resources, such systems scale with the number of hosts in terms of hardware, bandwidth, and disk space. With the wide deployment of P2P applications, the P2P traffic is becoming a growing portion of the Internet traffic. There has been very little examination of P2P traffic patterns and how they differ from traditional service models. Studying and understanding P2P traffic is thus important to provide efficient application-level content location and routing within the network. The existing applications use their own approach to do content location and routing and none of them are scalable. Napster uses a centralized server to locate content, while Gnutella clients broadcast queries to all their neighbors. [8] discusses the query locality observed in Gnutella traces and suggests caching as a short-term approach to increase Gnutella’s scalability. Recent designs such as CAN [5], Chord [9], Pastry [6], and Tapestry [10] propose distributed indexing schemes based on hashing to locate content. These systems assume a flat content delivery mesh. Each object’s location is stored at one or more nodes selected deterministically by a uniform hash function; queries for the object will be routed incrementally to the node. Although hash functions can help locate content deterministically, they lack the flexibility of keyword searching—a useful operation to find content without prior knowledge of exact object names. There is no real deployment at present and thus no measurement information is available for understanding the usability and scalability of
19002258
Reconstructing manifold and non-manifold surfaces from point clouds
This paper presents a novel approach for surface reconstruction from point clouds. The proposed technique is general in the sense that it naturally handles both manifold and non-manifold surfaces, providing a consistent way for reconstructing closed surfaces as well as surfaces with boundaries. It is also robust in the presence of noise, irregular sampling and surface gaps. Furthermore, it is fast, parallelizable and easy to implement because it is based on simple local operations. In this approach, surface reconstruction consists of three major steps: first, the space containing the point cloud is subdivided, creating a voxel representation. Then, a voxel surface is computed using gap filling and topological thinning operations. Finally, the resulting voxel surface is converted into a polygonal mesh. We demonstrate the effectiveness of our approach by reconstructing polygonal models from range scans of real objects as well as from synthetic data.
15313247
Performance of a MAC protocol for WDM networks with on-line scheduling
This paper investigates the performance of media access protocols based on on-line scheduling for an optically connected star-coupled system with wavelength division multiple access channels. Hybrid access protocols combining reservation and pre-allocation of receiver channels have been previously proposed. Transmission consisted of a reservation phase followed by a data phase. Each node was allowed to place a reservation for one WDM channel. This protocol is extended in this paper by allowing reservations on multiple channels and using simple on-line scheduling algorithms. Existing scheduling algorithms (all are off-line) for similar reservation problems tend to have high implementation and computational complexity. We require that scheduling algorithms be real-time and amenable to hardware implementation. The performance of the extended protocol incorporating two simple on-line scheduling algorithms is presented in this paper. We show that the slight increased computational overhead with scheduling is justified by reduced packet latency and higher utilization, especially for client-server traffic.
2685835
Energy Consumption of Swarm Intelligence inspired Routing Algorithms in MANETs
Swarm Intelligence (SI) inspired routing algorithms have become a research focus in recent years due to their self-organizing nature, which is very suitable to the routing problems in Mobile Ad hoc Networks (MANETs). The network information can be collected and updated in a decentralized and dynamic way through the localized cooperation among these swarm agents. In this paper, we, for the first time, provide a comprehensive comparison about current SI inspired routing algorithms in MANETs in the aspects of network metrics and simulation environment. Then, we make a detailed study about the energy consumption of the SI inspired routing problem in MANETs. Based on this study, we present the selection criterion of the intermediate nodes so as to be energy efficient. Experimental results are provided with reasonable verification.
12186597
A Power-Saving Multi-Radio Multi-Channel MAC Protocol for Wireless Local Area Networks
Opportunistic spectrum access and adaptive power management are effective techniques to improve throughput, delay performance, and energy efficiency for wireless networks. In this paper, we consider the joint design of opportunistic spectrum access and adaptive power management under the setting of multi-radio nodes and multi-channel wireless local area networks (WLANs) under the distributed coordination function (DCF) mode. This design problem is particularly challenging due to the conflicting nature of the multi-radio capability of a node, i.e., multiple radios improve throughput and delay performance at the cost of increased energy consumption. To address this problem, we propose a power-saving multi-channel MAC protocol (PSM-MMAC), which is capable of reducing the collision probability and the waiting time in the ‘awake’ state of a node, resulting in improved throughput, delay performance, and energy efficiency. The key ideas of PSM-MMAC are the following: we first estimate the number of active links; given this estimation as well as queue lengths and channel conditions, we appropriately select channels, radios, and power states (i.e., awake or doze state); then we optimize the medium access probability in p-persistent CSMA used in the data exchange. Another contribution of this paper is an analytical model that characterizes the throughput performance. Simulation results validate the accuracy of our analytical model and show that our proposed protocol is able to significantly improve both throughput and energy efficiency.