13955721
Improving bandwidth utilization based on deterministic delay bound in connection-oriented networks
Packet scheduling disciplines play an important role in providing quality of service (QoS) guarantees to applications traffic in high speed networks. Several scheduling disciplines have emerged in the literature that are capable of providing guarantees on various QoS parameters, such as packet delay, jitter, loss and throughput, while maintaining fairness among various connections. However, there is a trade-off between the performance and the simplicity of operation and implementation performance of the scheduling schemes. Thus the first-come-first-serve (FCFS) scheduling discipline has remained popular due to its overriding simplicity in spite of its poor capabilities in providing QoS guarantees. In previous work it has been shown that a practical worst case bound can be obtained for a deterministic delay guarantee in networks using the FCFS discipline, by imposing a source rate condition on each connection, that restricts the overall network utilization. In this paper, a modified source rate condition is proposed that can significantly increase the bandwidth utilization, while still maintaining the deterministic delay guarantee.
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.
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.
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.
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.
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.
17465088
An efficient channel-feedback-based adaptive protocol for scheduling variable-length messages on slotted, high-speed fiber optic LANs/MANs
This paper is based on the continuation-bit approach in conjunction with a probabilistic scheduling strategy called the p/sub i/-persistent protocol. This combination has been proposed as an efficient multiple access protocol for transmitting variable-length messages on slotted, high-speed, fiber-optic, bus-structured local and metropolitan area networks (LANs/MANs). Specifically, the authors extend the previous static model on this approach to the dynamic case so that the protocol can be implemented. A dynamic simulation model of the protocol using the continuation-bit approach has been formulated, and channel feedback information has been used to calibrate the operating parameters in real time. Since the goal was to study the operation of the dynamic protocol with variable-length messages, variable-bit-rate coded (i.e., compressed) video was chosen as the traffic to be carried by the network in the illustrative examples. The simulation model indicates that channel feedback is a good approach for dynamically adjusting the network parameters as the network loading and the message lengths fluctuate. Even at a network utilization of 0.6, it was found that almost all video messages were transmitted from the station buffers before the next video message arrived.<<ETX>>
31501132
Optical switch configuration and lightpath assignment in wavelength routing multihop lightwave networks
A wide-area transparent optical network can be constructed by using wavelength routers and switches, each dealing with only a small number of wavelengths. In this work we consider the problem of configuring the wavelength routers based on the observed traffic. Various policies for wavelength routing, and the corresponding assignment of wavelengths along the routes have been studied before, which are based on minimizing congestion, average hop-distance, and call blocking probability or on maximizing carried traffic, and the number of clear channels. However these approaches often lead to scenarios where a significant number of available wavelengths at the input/output ports of the routers cannot be used due to potential wavelength conflict. The wavelength routing and assignment algorithms presented in this paper focus on maximizing the wavelength-utilization at the switching devices which also improve the overall network performance.
206446555
Rover: Scalable Location-Aware Computing
All the components necessary for realizing location-aware computing are available in the marketplace today. What has hindered the widespread deployment of location-based systems is the lack of an integration architecture that scales with user populations. The authors have completed the initial implementation of Rover, a system designed to achieve this sort of integration and to automatically tailor information and services to a mobile user's location. Their studies have validated Rover's underlying software architecture, which achieves system scalability through high-resolution, application-specific resource scheduling at the servers and network. The authors believe that this technology will greatly enhance the user experience in many places, including museums, amusement and theme parks, shopping malls, game fields, offices, and business centers. They designed the system specifically to scale to large user populations and expect its benefits to increase with them.
2969941
SmartNotes: Implicit Labeling of Meeting Data through User Note-Taking and Browsing
We have implemented SmartNotes, a system that automatically acquires labeled meeting data as users take notes during meetings and browse the notes afterwards. Such data can enable meeting understanding components such as topic and action item detectors to automatically improve their performance over a sequence of meetings. The SmartNotes system consists of a laptop based note taking application, and a web based note retrieval system. We shall demonstrate the functionalities of this system, and will also demonstrate the labeled data obtained during typical meetings and browsing sessions.
2759775
Distributed channel management in uncoordinated wireless environments
Wireless 802.11 hotspots have grown in an uncoordinated fashion with highly variable deployment densities. Such uncoordinated deployments, coupled with the difficulty of implementing coordination protocols, has often led to conflicting configurations (e.g., in choice of transmission power and channel of operation) among the corresponding Access Points (APs). Overall, such conflicts cause both unpredictable network performance and unfairness among clients of neighboring hotspots. In this paper, we focus on the fairness problem for uncoordinated deployments. We study this problem from the channel assignment perspective. Our solution is based on the notion of channel-hopping, and meets all the important design considerations for control methods in uncoordinated deployments - distributed in nature, minimal to zero coordination among APs belonging to different hotspots, simple to implement, and interoperable with existing standards. In particular, we propose a specific algorithm called MAXchop, which works efficiently when using only non-overlapping wireless channels, but is particularly effective in exploiting partially-overlapped channels that have been proposed in recent literature. We also evaluate how our channel assignment approach complements previously proposed carrier sensing techniques in providing further performance improvements. Through extensive simulations on real hotspot topologies and evaluation of a full implementation of this technique, we demonstrate the efficacy of these techniques for not only fairness, but also the aggregate throughput, metrics.We believe that this is the first work that brings into focus the fairness properties of channel hopping techniques and we hope that the insights from this research will be applied to other domains where a fair division of a system's resources is an important consideration.