Stabilizing data-link over non-FIFO channels with optimal fault-resilience

Self-stabilizing systems have the ability to converge to a correct behavior when started in any configuration. Most of the work done so far in the self-stabilization area assumed either communication via shared memory or via FIFO channels.This paper is the first to lay the bases for the design of self-stabilizing message passing algorithms over unreliable non-FIFO channels. We propose an optimal stabilizing data-link layer that emulates a reliable FIFO communication channel over unreliable capacity bounded non-FIFO channels (the channel capacity is known to the protocol).     

Data mining middleware for wide-area high-performance networks

In this paper, we describe two distributed, data intensive applications that were demonstrated at iGrid 2005 (iGrid Demonstration US109 and iGrid Demonstration US121). One involves transporting astronomical data from the Sloan Digital Sky Survey (SDSS) and the other involves computing histograms from multiple high-volume data streams. Both rely on newly developed data transport and data mining middleware. Specifically, we describe a new version of the UDT network protocol called Composible-UDT, a file transfer utility based upon UDT called UDT-Gateway, and an application for building histograms on high-volume data flows called BESH (for Best Effort Streaming Histogram). For both demonstrations, we include a summary of the experimental studies performed at iGrid 2005.     

Boundary feedback control in networks of open channels

This article deals with the regulation of water flow in open-channels modelled by Saint-Venant equations. By means of a Riemann invariants approach, we deduce stabilizing control laws for a single horizontal reach without friction. The stability condition is extended to a general class of hyperbolic systems which can describe canal networks with more general topologies. A control law design based on this condition is illustrated with a simple case study: two reaches in cascade. The proof of the main stability theorem is based on a previous result from Li Ta-tsien concerning the existence and decay of classical solutions of hyperbolic systems.     

Fault-tolerant design for wide-area Mobile IPv6 networks

Mobile IPv6 provides the mobility management for IPv6 protocol. To establish a reliable Mobile IPv6 network, fault tolerance should be also considered in the network design. This paper presents an efficient fault-tolerant approach for Mobile IPv6 networks. In the proposed approach, if a failure is detected in the home agent (HA) of a mobile node, a preferable survival HA is selected to continuously serve the mobile node. The preferable survival HA is the HA that does not incur failure and is neighboring the current location of the mobile node. The proposed approach is based on the preference of each mobile node to achieve the fault tolerance of the HA. Finally, we perform simulations to evaluate the performance of the proposed approach.     

Suboptimal decentralized control over noisy communication channels

In this paper we present a technique for the design of decentralized controllers for mean square stability of a large scale system with cascaded clusters of subsystems. Each subsystem is linear and time-invariant and both system and measurement are subject to Gaussian noise. For stability analysis of this system we consider the effects of Additive White Gaussian Noise (AWGN) channels used for exchanging information between subsystems.     

Arise: operating PCTE over a wide-area network

A case study in which the feasibility of operating the Portable Common Tools Environment (PCTE) across a wide-area network was determined as part of the Arise project is discussed. Simple benchmarks and experiments with a configuration-management application indicate that a wide-area PCTE is feasible, provided there is a suitable data-distribution strategy     

Increasing wide-area download throughputs on the roads by trunking multiple cellular channels over a vehicular ad hoc network

To obtain infotainment services (e.g., traffic, maps, accidents, weather, etc.) on the roads, vehicle drivers and back-seat passengers may want to use wide-area networks (e.g., GPRS) to download useful information from the Internet when needed. In this paper, we design and implement a scheme to increase GPRS download throughput for a vehicle user while he (she) is moving on the roads. This scheme integrates inter-vehicle communication with trunking mechanisms to achieve this goal. This scheme can be readily deployed for any real-world GPRS network or any 3G network without any support from the network operator. Our field trial results show that when this scheme is applied in a motorcade of four vehicles and all of the GPRS channel provided by each vehicle are used to download a file simultaneously, the download speed is 3.92 times faster than that achieved when only one GPRS channel is used.     

Utility-based scheduling in wireless multi-hop networks over non-deterministic fading channels

In this paper, an innovative scheduling scheme is proposed for interference-limited wireless multi-hop networks with non-deterministic fading channels. The scheduling problem is considered as a network utility maximization (NUM) problem subject to link rate constraints. By jointly taking into account of the link scheduling and the statistical variations of signal and interference power, the convex sets for the NUM are derived. Two types of non-deterministic fading channels (i.e., Rayleigh fading channel and Ricean fading channel) are characterized into our NUM models as examples. To solve the convex optimization problem, the subgradient projection method based on dual decomposition is employed. Then, a heuristic algorithm is designed for the TDM mode wireless multi-hop networks by minimizing the discrepancy between the expected network cost and the optimal one in each timeslot. At last, the source–destination session rate and network utility are evaluated in a dedicated wireless multi-hop network scenario. The numerical results demonstrate that the session rates convergence and the network utility is improved by our proposed scheme.     

Multi-criteria decision-making for controller placement in software-defined wide-area networks

The Journal of Supercomputing - Software-defined networks have many benefits such as more control over the control plane and reduced operating costs through separating the control plane from the...     

Event-triggered transmission for linear control over communication channels

We consider an exponentially stable closed loop interconnection between a continuous-time linear plant and a continuous-time linear controller, and we study the problem of interconnecting the plant output to the controller input through a digital channel. We propose an event-triggered transmission policy whose goal is to transmit the measured plant output information as little as possible while preserving closed-loop stability. Global asymptotic stability is guaranteed when the plant state is available or when an estimate of the state is available (provided by a classical continuous-time linear observer). Under further assumptions, the transmission policy guarantees global exponential stability of the origin.     

Supporting constant-bit-rate-encoded MPEG-2 transport over local ATM networks

As one of the fast-developing switch-based high-speed networks, asynchronous transfer mode (ATM) is a promising network standard which may satisfy various requirements of multimedia computing. The Moving Picture Experts Group (MPEG) standard was designed to support full motion video stored on digital storage media at compression ratios up to 200:1. MPEG-2 is the second development phase of the MPEG standard and is designed for higher resolutions (including but not restricted to interlaced video) and higher bit rates (up to 20 Mbits/s). In this paper, the ATM adaptation layer type 5 (AAL-5) protocol was used to encapsulate constant-bit-rate-encoded MPEG-2 transport packets because of AAL-5's general availability. However, there is a mismatch of size between MPEG-2's transport packets (188 bytes) and ATM AAL-5's protocol data units (up to 65 535 bytes). In this paper, we examine and analyze four different packing schemes, 1TP, 2TP, nTP-Tight, and nTP-Loose (the scheme we propose), which encapsulated a certain number of MPEG-2 transport packets into one AAL-5 PDU. nTP-Loose scheme is proposed to have (1) better end-to-end performance than schemes 1TP and 2TP, (2) better error-recovery capability than scheme nTP-Tight, and (3) the same buffer requirement as scheme 2TP. A Power Macintosh ATM platform was used to identify the range of possible ways of packing MPEG-2 transport packets into one ATM AAL-5 PDU, when schemes with more than two MPEG-2 transport packets are chosen. Based on the test results, 10 or 12 MPEG-2 transport packets, which can yield throughputs of 70.36 and 78.98 Mbits/s, respectively, are recommended. Fast forward and backward playing of MPEG-2 movies (several times the video display speed) can be easily achieved via ATM networks.     

Stabilizing maximum matching in bipartite networks

A matching ${E_\mathcal{M}}$ of graph G =  (V, E) is a subset of the edges E, such that no vertex in V is incident to more than one edge in ${E_\mathcal{M}}$ . The matching ${E_\mathcal{M}}$ is maximum if there is no matching in G with size strictly larger than the size of ${E_\mathcal{M}}$ . In this paper, we present a distributed stabilizing algorithm for finding maximum matching in bipartite graphs based on the stabilizing PIF algorithm of Cournier et al. (Proceedings of 21st IEEE international conference on distributed computing systems, 91–98, 2001). Since our algorithm is stabilizing, it does not require initialization and withstands transient faults. The complexity of the proposed algorithm is O(d × n) rounds, where d is the diameter of the communication network and n is the number of nodes in the network. The space complexity is O(log Δ +  log d), where Δ is the largest degree of all the nodes in the communication network. In addition, an optimal version of the proposed algorithm finding maximum matching in linear time is also presented.     

Optimization and performance of restoration schemes for wide-area teletraffic networks

In the event of a major network outage such as a fiber cable cut, a network can experience significant deterioration of network performance. To address such a situation, a network can be equipped with restoration capacity. We present here a mathematical model and design algorithm for determination of transmission network restoration capacity. We then present models for two restoration options-connection-based restoration and load directed restoration (for restoration of bundle of circuits)-and consider their impact on a wide-area dynmic call routing teletraffic network when the restoration capacity is limited (tight). Our network simulation of failure and restoration of a dynamic call routing teletraffic network shows that the load directed approach generally performs better than the connection based approach.     

Secrecy outage analysis for underlay cognitive radio networks over correlated channels

This paper investigates the secrecy outage performance of underlay cognitive radio networks, in which a source in a secondary system transmits its confidential information to a legitimate destination in the presence of an eavesdropper. Specifically, the main (the source-to-destination) and eavesdropping (the sourceto- eavesdropper) channels are assumed to be correlated. Moreover, it is also assumed that the main channel and the channel from the source to the primary user’s receiver are correlated. Tight closed-form analytical expression for secrecy outage probability and the closed-form analytical expression for the probability of non-zero secrecy capacity are derived and validated by simulation results when the interference temperature limit is comparably large.     

SocialVPN: Enabling wide-area collaboration with integrated social and overlay networks

Trusted collaborative systems require peers to be able to communicate over private, authenticated end-to-end channels. Network-layer approaches such as Virtual Private Networks (VPNs) exist, but require considerable setup and management which hinder the establishment of ad-hoc collaborative environments: trust needs to be established, cryptographic keys need to be exchanged, and private network tunnels need to be created and maintained among end users. In this paper, we propose a novel system architecture which leverages existing social infrastructures to enable ad-hoc VPNs which are self-configuring, self-managing, yet maintain security amongst trusted and untrusted third parties. The key principles of our approach are: (1) self-configuring virtual network overlays enable seamless bi-directional IP-layer connectivity to socially connected parties; (2) online social networking relationships facilitate the establishment of trust relationships among peers; and (3) both centralized and decentralized databases of social network relationships can be securely integrated into existing public-key cryptography (PKI) implementations to authenticate and encrypt end-to-end traffic flows. The main contribution of this paper is a new peer-to-peer overlay architecture that securely and autonomously creates VPN tunnels connecting social peers, where online identities and social networking relationships may be obtained from centralized infrastructures, or managed in a decentralized fashion by the peers themselves.This paper also reports on the design and performance of a prototype implementation that embodies the SocialVPN architecture. The SocialVPN router builds upon IP-over-P2P (IPOP) virtual networks and a PKI-based tunneling infrastructure, which integrates with both centralized and decentralized social networking systems including Facebook, the Drupal open-source content management system, and emailing systems with PGP support. We demonstrate our prototype’s ability to support existing, unmodified TCP/IP applications while transparently dealing with user connectivity behind Network Address Translators (NATs). We also present qualitative and quantitative analyses of functionality and performance based on wide-area network experiments using PlanetLab and Amazon EC2.     

Unreliable transport protocol using congestion control for high-speed networks

Currently there is no control for the real-time traffic of multimedia applications using UDP (User Datagram Protocol) in high-speed networks. Therefore, although a number of high-speed TCP (Transmission Control Protocol) protocols have been developed for gigabit-speed (or faster) links, the real-time traffic could also congest the network and result in unfairness and throughput degradation of TCP traffic. In this paper, a new unreliable transport protocol, FAST DCCP, is presented for the real-time traffic in high-speed networks. FAST DCCP is based on the DCCP protocol and adopts the FAST scheme to realize congestion control. Some modifications have been made to the mechanisms inherited from DCCP so as to let the proposed protocol can efficiently operate under a large size window. In addition, an enhanced protocol, EEFAST DCCP, using the measurements of one-way delay to dynamically adjust the window size is also proposed to improve the throughput of FAST DCCP with the effect of reverse traffic. Simulation results show that FAST DCCP not only can satisfy the requirements of real-time data delivery, but also perform well in bandwidth utilization and fairness in high-speed networks. Meanwhile, EEFAST DCCP is able to effectively conquer the throughput degradation caused by the reverse traffic.     

Diversity order of multiuser two-way relay networks with beamforming over Nakagami-m fading channels

The diversity performance of multiuser two-way relay networks is investigated over Nakagami-m fading channels.We consider an amplify-and-forward relay network with beamforming at the base station and all the mobile stations,and derive closed-form lower and upper bounds on the outage probabilities of two unidirectional links,respectively.Moreover,the exact expression for the diversity order and the asymptotic expressions for the outage probabilities of two unidirectional links are given too.Finally,simulatio...     

Reliable fault-tolerant model predictive control of drinking water transport networks

This paper proposes a reliable fault-tolerant model predictive control applied to drinking water transport networks. After a fault has occurred, the predictive controller should be redesigned to cope with the fault effect. Before starting to apply the fault-tolerant control strategy, it should be evaluated whether the predictive controller will be able to continue operating after the fault appearance. This is done by means of a structural analysis to determine loss of controllability after the fault complemented with feasibility analysis of the optimization problem related to the predictive controller design, so as to consider the fault effect in actuator constraints. Moreover, by evaluating the admissibility of the different actuator-fault configurations, critical actuators regarding fault tolerance can be identified considering structural, feasibility, performance and reliability analyses. On the other hand, the proposed approach allows a degradation analysis of the system to be performed. As a result of these analyses, the predictive controller design can be modified by adapting constraints such that the best achievable performance with some pre-established level of reliability will be achieved. The proposed approach is tested on the Barcelona drinking water transport network.     

Remote control of LTI systems over networks with state quantization

We consider a remote control system, where the plant and the controller are connected by a network cable, and study the problem of designing quantizers for its stabilization. It is assumed that the computation available on the plant side in the sensor/actuator is limited and also that broadcast of messages is allowed over the channel.     

基于反馈的Ad Hoc网络传输控制增强机制

ATP是专门针对AdHoc网络的特点制定的传榆协议,当路由中断后,ATP源端立即进入探测状态,周期性地向目的端发送探测包,造成吞吐量的降低。EATP是一种基于反馈的ATP增强机制,它通过在ATP源端设置定时器,路由中断时限制源端发送探测包的数量,避免了多个重复确认问题。性能分析与仿真实验结果显示,与传统TCP—ELFN相比,EATP能有效地提高AdHoc网络的吞吐量,减少不必要的能源消耗。