3132692
Distributed Database Systems in High-Speed Wide-Area Networks
The issues involved in developing a distributed database system (DDBS) in a high-speed environment are discussed. The inadequacy of existing database protocols in utilizing the gigabit network is described. A concurrency control protocol that performs better than traditional DDBSs in high-speed networks is developed. Both analytical and simulation results are presented. The focus is on the concurrency control aspect of DDBS since this protocol is at the heart of the overall functioning of the distributed system. >
14976055
A new token passing distributed mutual exclusion algorithm
Eliminating interference between concurrently executing activities through mutual exclusion is one of the most fundamental problems in computer systems. The problem of mutual exclusion in a distributed system is especially interesting owing to the lack of global knowledge in the presence of variable communication delays. In this paper, a new token-based distributed mutual exclusion algorithm is proposed. The algorithm incurs approximately three messages at high loads, irrespective of the number of nodes N in the system. At low loads, it requires approximately N messages. The paper also addresses failure recovery issues, such as token loss.
30095382
Performance Analysis of Generalized Selective Packet Discarding Schemes
Selective packet discarding schemes have been mostly developed and analyzed in the context of ATM networks. However, similar schemes could be applied to non-ATM or more general networks. The analysis of selective packet discarding schemes in a general packet switching environment has been limited to the basic dropping schemes, i.e., Partial Packet Discard (PPD) and Early Packet Discard (EPD), and for only the single traffic source case. In this paper, we extend the mathematical analysis of PPD and EPD for multiple sources and include simulation results to verify the analytical results. Finally, to place the performance of the generalized EPD and PPD in the context of other packet dropping schemes, we also provide simulation results of the Drop from Front (DfF), and preemptive Partial Packet Discard (pPPD) schemes.
40446138
A distributed hierarchical management framework for heterogeneous WANs
The scope of network management is expanding in multiple dimensions. Local area networks (LANs) have more nodes than ever before, enterprise networks span national boundaries, wide area networks (WANs) cover the globe, and administrators want to manage their LANs all the way down to a PC’s network interface and application software. In order to centrally manage these networks, the network manager faces the complexity of heterogeneous management tools and the difficulty of managing vast amount of data generated by network elements.
13442653
Establishing virtual enterprises by means of mobile agents
Electronic commerce is expanding from the simple notion of electronic stores to the notion of virtual enterprises (VE), where existing enterprises dynamically form temporary alliances, joining their businesses in order to share their costs, skills and resources in supporting certain activities. Two fundamental problems in VE are: (1) how a VE is established, and (2) how information is shared among the VE participants in a controlled and efficient manner. Currently, existing enterprises are using workflows to automate their operations by integrating their information systems and human resources. Thus, in this paper, we view the establishment of a VE as a problem of dynamically expanding and integrating workflows in decentralized, autonomous and interacting workflow management systems. The focus is on the idea of mobile agents called "adlets" and their use in establishing VEs that involves advertising, negotiating and exchanging control information and data as well as its management.
25726525
A survey of TCP-friendly router-based AQM schemes
Although the majority of the traffic over the Internet is still TCP-based, applications such as voice over IP and video-conferencing are changing this very rapidly. While TCP-based applications react to network congestion, UDP-based streaming applications usually do not have any type of flow and congestion control mechanisms. UDP, the transport layer protocol used by audio and video streaming applications, does not react to network congestion thus stealing bandwidth from the responsive TCP-based connections. Several solutions have been suggested to combat this TCP-friendliness problem, mostly applied either in the end systems (end-to-end) at the transport layer of the protocol stack or inside the network (routers) at the network layer. This article surveys the state-of-the-art in router-based mechanisms to address the TCP-friendliness problem and presents a description of the most important algorithms, design issues, advantages and disadvantages, and a performance evaluation. The article also describes ways to estimate the number of active flows traversing a core router and points to further sources on this subject, which is widely used by many mechanisms, including several described in this survey.
206616812
The Design, Implementation, and Use of the Ngram Statistics Package
The Ngram Statistics Package (NSP) is a flexible and easy-to-use software tool that supports the identification and analysis of Ngrams, sequences of N tokens in online text. We have designed and implemented NSP to be easy to customize to particular problems and yet remain general enough to serve a broad range of needs. This paper provides an introduction to NSP while raising some general issues in Ngram analysis, and summarizes several applications where NSP has been successfully employed. NSP is written in Perl and is freely available under the GNU Public License.
3056111
An Analysis of Wireless Network Coding for Unicast Sessions: The Case for Coding-Aware Routing
A recent approach, COPE, for improving the throughput of unicast traffic in wireless multi-hop networks exploits the broadcast nature of the wireless medium through opportunistic network coding. In this paper, we analyze throughput improvements obtained by COPE-type network coding in wireless networks from a theoretical perspective. We make two key contributions. First, we obtain a theoretical formulation for computing the throughput of network coding on any wireless network topology and any pattern of concurrent unicast traffic sessions. Second, we advocate that routing be made aware of network coding opportunities rather than, as in COPE, being oblivious to it. More importantly, our work studies the tradeoff between routing flows "close to each other" for utilizing coding opportunities and "away from each other" for avoiding wireless interference. Our theoretical formulation provides a method for computing source-destination routes and utilizing the best coding opportunities from available ones so as to maximize the throughput. We handle scheduling of broadcast transmissions subject to wireless transmit/receive diversity and link interference in our optimization framework. Using our formulations, we compare the performance of traditional unicast routing and network coding with coding-oblivious and coding-aware routing on a variety of mesh network topologies, including some derived from contemporary mesh network testbeds. Our evaluations show that a route selection strategy that is aware of network coding opportunities leads to higher end-to-end throughput when compared to coding-oblivious routing strategies.
17614044
Measurement Approaches to Evaluate Performance Optimizations for Wide-Area Wireless Networks
We present measurement approaches to evaluate performance optimizations, employed at different layers of the protocol stack, to enhance application performance over wide-area wireless networks (WWANs). Applications running over WWAN cellular environments (e.g web browsing) are significantly affected by the vagaries of the cellular wireless links. Much of the prior research has focussed on variety of isolated performance optimizations and their measurements over wired and wireless environments. In this paper we introduce experiment-based measurement approaches to benchmark application performance using optimizations performed at individual layers of the protocol stack.
11158
SenseRelate: : TargetWord-A Generalized Framework for Word Sense Disambiguation
Many words in natural language have different meanings when used in different contexts. Sense Relate: Target Word is a Perl package that disambiguates a target word in context by finding the sense that is most related to its neighbors according to a WordNet: Similarity measure of relatedness.
14498501
A clustering scheme for hierarchical control in multi-hop wireless networks
In this paper we present a clustering scheme to create a hierarchical control structure for multi-hop wireless networks. A cluster is defined as a subset of vertices, whose induced graph is connected. In addition, a cluster is required to obey certain constraints that are useful for management and scalability of the hierarchy. All these constraints cannot be met simultaneously for general graphs, but we show how such a clustering can be obtained for wireless network topologies. Finally, we present an efficient distributed implementation of our clustering algorithm for a set of wireless nodes to create the set of desired clusters.