Simple models of network access,with applications to the design of joint rate and admission control

At the access to networks, in contrast to the core, distances and feedback delays, as well as link capacities are small, which has network engineering implications that are investigated in this paper. We consider a single point in the access network which multiplexes several bursty users. The users adapt their sending rates based on feedback from the access multiplexer. Important parameters are the user’s peak transmission rate p, which is the access line speed, the user’s guaranteed minimum rate r, and the bound ϵ on the fraction of lost data.Two feedback schemes are proposed. In both schemes the users are allowed to send at rate p if the system is relatively lightly loaded, at rate r during periods of congestion, and at a rate between r and p, in an intermediate region. For both feedback schemes we present an exact analysis, under the assumption that the users’ job sizes and think times have exponential distributions. We use our techniques to design the schemes jointly with admission control, i.e., the selection of the number of admissible users, to maximize throughput for given p, r, and ϵ. Next we consider the case in which the number of users is large. Under a specific scaling, we derive explicit large deviations asymptotics for both models. We discuss the extension to general distributions of user data and think times.     

移动网络中心云计算存储数据访问安全自动监测系统设计

为了提高移动网络中心云计算存储数据访问和安全监测能力,提出一种基于深度学习和交叉编译控制的移动网络中心云计算存储数据访问安全自动监测系统设计方法。采用混合属性数据模糊加权聚类方法进行移动网络中心云计算存储数据的优化访问控制模型设计,根据云计算存储数据之间的属性相似度进行离散化数值属性分解,提取移动网络中心云计算存储数据的混合属性特征量,根据最小化云存储数据访问成本为代价进行移动网络中心云计算存储数据访问的安全监测。结合深度学习方法进行数据访问的自适应控制,在交叉编译环境下实现云计算存储数据访问安全自动监测系统开发设计。测试结果表明,采用该方法进行移动网络中心云计算存储数据访问的安全性较好,自动化控制能力较强。     

Secure three-party key distribution protocol for fast network access in EAP-based wireless networks

In this paper, we present a solution that reduces the time spent on providing network access in multi-domain mobile networks where the authentication process is based on the Extensible Authentication Protocol (EAP). The goal is to achieve fast and smooth handoffs by reducing the latency added by the authentication process. This process is typically required when a mobile user moves from one authenticator to another regardless of whether the new authenticator is in the same domain (intra-domain) or different domain (inter-domain). To achieve an efficient solution to this problem, it has been generally recognized that a fast and secure key distribution process is required. We propose a new fast re-authentication architecture that employs a secure three-party key distribution protocol which reduces the number of message exchanges during the network access control process. Our approach is proved to preserve security and verified by means of a formal tool. The resulting performance benefits are shown through our extensive simulations.     

Access regulation mechanism for switch-based LAN

This paper describes a mechanism that regulates access of bursty traffic sources to a switch-based LAN. This regulation mechanism ensures global fairness, such that, within a well-defined global control cycle each node can transmit a predefined number of data units over its adjacent links, i.e., it provides deterministic access delay bound and bandwidth. The global control cycle is created over a tree that spans a network with an arbitrary topology, in contrast with previous works, in which a global control cycle was created over a ring (e.g., token-ring, MetaRing). As a result, in this work the global control cycle can be shorter and the access mechanism to the network is more efficient. The regulation mechanism is based on exchanging control signals between neighboring nodes. The proposed mechanism has the following properties: (i) time-driven automatic stabilization, (ii) automatic tolerance of one control signal loss in every global control cycle, and (iii) only two bits of information required for the control signals.     

An H∞ approach to congestion control design for AQM routers supporting TCP flows in wireless access networks

In this paper, we aim at developing an H_∞ approach, from control-theoretic viewpoint, to the design of an active queue management (AQM) based congestion control algorithm for wireless networks supporting the Internet Protocol. We study networks in which the backbone is a traditional wired network supporting Internet TCP, while end user access is via wireless. First, a dynamic model for the congestion control problem of wireless networks is built up, which enables the application of modern control theory on time-delay systems to this problem. Second, an H_∞ design approach for general time-delay systems is presented. Finally, the proposed approach is applied to the congestion control algorithm design of wireless networks, yielding an effective and systematic way for the design problem. Simulation results are provided to illustrate the design procedure and the effectiveness of the proposed method. Our design method is described by linear matrix inequalities (LMI), which can be solved very efficiently by LMI toolbox in Matlab.     

Output synchronization for heterogeneous networks of non-introspective agents

In this paper we consider the output synchronization problem for heterogeneous networks of linear agents. The network’s communication infrastructure provides each agent with a linear combination of its own output relative to that of neighboring agents, and it allows the agents to exchange information about their own internal observer estimates. We design decentralized controllers based on setting the control input of a single root agent to zero and letting the remaining agents synchronize to the root agent. A distinguishing feature of our work is that the agents are assumed to be non-introspective, meaning that they possess no knowledge about their own state or output separate from what is received via the network. We also consider the problem of regulating the agreement trajectory according to an a priori specified reference model. In this case we assume that some of the agents have access to their own output relative to the reference trajectory.     

A per-application mobility management platform for application-specific handover decision in overlay networks

With the advance of various wireless access technologies, the demand for a mobile user equipped with multiple air interfaces simultaneously executing diverse applications emerged. In such network environments, per-application mobility management is a key to allow each application of an end user device to dynamically and fully take advantage of the most suitable access technology. In this paper, we devised a comprehensive architectural platform with cross-layer techniques to realize this disruptive technology, i.e., per-application mobility management. The proposed platform enables the triggering of vertical handover decisions based on the dynamic measurements from the entire protocol stack. For per-application, the handover decision as well as the mobility management and the transport/application protocol control adaptation for handover performance optimization are made with cross-layer techniques. Through the simulation results, it is shown that multi-layer handover triggering of the proposed platform enhances the QoS of the application services by making handover decisions when the QoS requirements of an application is not satisfied as well as when a mobile user moves out of the current access network in overlay network environments. It is also presented that per-application handover based on the proposed platform enhances the QoS of the application services compared to the handover approaches which make every on-going service flows handover together to the same access network.     

Saturated throughput analysis of IEEE 802.11e EDCA

IEEE 802.11e standard has been published to introduce quality of service (QoS) support to the conventional IEEE 802.11 wireless local area network (WLAN). Enhanced distributed channel access (EDCA) is used as the fundamental access mechanism for the medium access control (MAC) layer in IEEE 802.11e. In this paper, a novel Markov chain based model with a simple architecture for EDCA performance analysis under the saturated traffic load is proposed. Compared with the existing analytical models of EDCA, the proposed model incorporates more features of EDCA into the analysis. Firstly, we analyze the effect of using different arbitration interframe spaces (AIFSs) on the performance of EDCA. That is, the time interval from the end of the busy channel can be classified into different contention zones based on the different AIFSs used by different sets of stations, and these different sets of stations may have different transmission probabilities in the same contention zone. Secondly, we analyze the possibility that a station’s backoff procedure may be suspended due to transmission from other stations. We consider that the contention zone specific transmission probability caused by the use of different AIFSs can affect the occurrence and the duration of the backoff suspension procedure. Based on the proposed model, saturated throughput of EDCA is analyzed. Simulation study is performed, which demonstrates that the proposed model has better accuracy than those in the literature.     

Distributed adaptive top-k monitoring in wireless sensor networks

Top-k monitoring queries are useful in many wireless sensor network applications. A query of this type continuously returns a list of k ordered nodes with the highest (or lowest) sensor readings. To process these queries, a well-known approach is to install a filter at each sensor node to avoid unnecessary transmissions of sensor readings. In this paper, we propose a new top-k monitoring method, named Distributed Adaptive Filter-based Monitoring. In this method, we first propose a new query reevaluation algorithm that works distributedly in the network to reduce the communication cost of sending probe messages. Then, we present an adaptive filter updating algorithm which is based on predicted benefits to lower down the transmission cost of sending updated filters to the sensor nodes. Experimental results on real data traces show that our proposed method performs much better than the other existing methods in terms of both network lifetime and average energy consumption.     

Access control in feature-oriented programming

In feature-oriented programming (FOP) a programmer decomposes a program in terms of features. Ideally, features are implemented modularly so that they can be developed in isolation. Access control mechanisms in the form of access or visibility modifiers are an important ingredient to attain feature modularity as they allow programmers to hide and expose internal details of a module’s implementation. But developers of contemporary feature-oriented languages have not considered access control mechanisms so far. The absence of a well-defined access control model for FOP breaks encapsulation of feature code and leads to unexpected program behaviors and inadvertent type errors. We raise awareness of this problem, propose three feature-oriented access modifiers, and present a corresponding access modifier model. We offer an implementation of the model on the basis of a fully-fledged feature-oriented compiler. Finally, by analyzing ten feature-oriented programs, we explore the potential of feature-oriented modifiers in FOP.     

Analysis of power saving with continuous connectivity

Always-on mobile users need high bandwidth channels with negligible access delay and limited power consumption. Such a continuous connectivity mode requires the management of high-speed channels, which can turn into substantial operational costs (i.e., power consumption rate) even in presence of low traffic, unless a power saving mechanism is enforced. In this paper, we analyze the impact of 3GPP-defined power saving mechanisms on the performance of users with continuous connectivity. We develop a model for packet transmission and operational costs. We model each downlink mobile user’s traffic by means of an M/G/1 queue, and the base station’s downlink traffic as an M/G/1 PS queue with multiple classes and inhomogeneous vacations. The model is validated through packet-level simulations. Our results show that consistent power saving can be achieved in the wireless access network, as high as 75% for mobiles and 55% for base stations.     

Development of remote control and monitoring of web-based distributed OPC system

This paper focuses on implementing remote control and monitoring of a web-based distributed OLE for Process Control (OPC) system. Remote monitoring and control of OPC-based systems realized at N different local control points on the Internet are achieved by using a distributed OPC (DOPC) architecture. In this proposed architecture, every local control center can control and monitor every other control point. DOPC architecture is developed by using an OPC standard created for the automation industry. This OPC was developed as an industrial standard using Microsoft's Object Linking and Embedding (OLE) technology. OPC enables different control devices to communicate with each other by exchanging data. This proposed architecture permits different OPC-based process control architectures from a wide range of fields to communicate with each other. Thus, OPC-based local control systems located in different places can communicate with each other on the Internet without using bus architecture. The basic functions of the proposed system were implemented using the Delphi software package. Local control architectures developed at N points can communicate with each other and a remote control point on a dynamic web page constructed using Active Server Pages (ASP). Consequently, the proposed DOPC architecture allows the user to control and monitor local systems from any location with internet access, and to implement data exchange between N OPC points.     

Throughput-delay performance of packet-switching multiple-access channel with power capture

Power capture is the ability of a receiver to receive correctly the strongest of several messages that arrive during overlapping intervals. The presence of power capture in multiple-access packet switching channels introduces inequality in the access conditions to the channel when packets arrive at the receiver at different power levels. Two models for such channels under slotted ALOHA protocol with power capture are considered. In the first, a packet is transmitted at one of K possible power levels, and it is received correctly if no other packet is transmitted at the same or higher level. The second model is of a ground radio network where a received packet's power is inversely proportional to the distance it propagates. In this model, a packet transmitted from a distance r is received correctly if no other packet is transmitted from a distance smaller than a · r (a ? 1). A technique developed by Lam (1974) is generalized to obtain the throughput-delay characteristics of the channel for both models. The effect of high power traffic on the lower power traffic is discussed, and it is shown that the ‘Sisyphus distance’ phenomenon predicted by Abramson (1977) for the case a = 1 in the second model does not exist in the more realistic case of a > 1.     

An update-based step-wise optimal cache replacement for wireless data access

Many network applications requires access to most up-to-date information. An update event makes the corresponding cached data item obsolete, and cache hits due to obsolete data items become simply useless to those applications. Frequently accessed but infrequently updated data items should get higher preference while caching, and infrequently accessed but frequently updated items should have lower preference. Such items may not be cached at all or should be evicted from the cache to accommodate items with higher preference. In wireless networks, remote data access is typically more expensive than in wired networks. Hence, an efficient caching scheme considers both data access and update patterns can better reduce data transmissions in wireless networks. In this paper, we propose a step-wise optimal update-based replacement policy, called the Update-based Step-wise Optimal (USO) policy, for wireless data networks to optimize transmission cost by increasing effective hit ratio. Our cache replacement policy is based on the idea of giving preference to frequently accessed but infrequently updated data, and is supported by an analytical model with quantitative analysis. We also present results from our extensive simulations. We demonstrate that (1) the analytical model is validated by the simulation results and (2) the proposed scheme outperforms the Least Frequently Used (LFU) scheme in terms of effective hit ratio and communication cost.     

Incremental deployment of network monitors based on Group Betweenness Centrality

In many applications we are required to increase the deployment of a distributed monitoring system on an evolving network. In this paper we present a new method for finding candidate locations for additional deployment in the network. This method is based on the Group Betweenness Centrality (GBC) measure that is used to estimate the influence of a group of nodes over the information flow in the network. The new method assists in finding the location of k additional monitors in the evolving network, such that the portion of additional traffic covered is at least (1−1/e) of the optimal.     

The file allocation problem under dynamic usage

The file allocation problem considers a file and a fully connected network having n nodes. The problem assumes that the overall file usage over a unit time period is known and it asks for the optimal set of network sites at which to locate copies of the file. This paper considers the same problem but it assumes that the behavior of the user access patterns changes over v planning periods in a manner, known in advance. A model is presented which shows that there are (2ⁿ ? 1)^v possible file allocations. To assist the searching of this large solution space four theorems are presented which are subsequently utilized to analyze the problem and to solve an example case.     

Mosco: a privacy-aware middleware for mobile social computing

The proliferation of mobile devices coupled with Internet access is generating a tremendous amount of highly personal and sensitive data. Applications such as location-based services and quantified self harness such data to bring meaningful context to users’ behavior. As social applications are becoming prevalent, there is a trend for users to share their mobile data. The nature of online social networking poses new challenges for controlling access to private data, as compared to traditional enterprise systems. First, the user may have a large number of friends, each associated with a unique access policy. Second, the access control policies must be dynamic and fine-grained, i.e. they are content-based, as opposed to all-or-nothing. In this paper, we investigate the challenges in sharing of mobile data in social applications. We design and evaluate a middleware running on Google App Engine, named Mosco, that manages and facilitates sharing of mobile data in a privacy-preserving manner. We use Mosco to develop a location sharing and a health monitoring application. Mosco helps shorten the development process. Finally, we perform benchmarking experiments with Mosco, the results of which indicate small overhead and high scalability.     

Announced dynamic access probability protocol for next generation wireless networks

A multiple access protocol that is particularly suitable for cellular Internet access and satellite-based networks with on-board processing is developed in this paper. The basic idea is that when a user wishes to send a message, it transmits with probability p_access that depends on the load on the channel. Under conditions of low load, the probability p_access approaches 1, while at high load p_access is relatively low. This media access control protocol guarantees high channel utilization at high load, as well as low delay at low load periods. Using the statistical usage of the shared channel, the load is estimated with certain uncertainty. Our analysis shows that using the statistical usage of the shared channel, the optimal access probability can be well estimated for a broad class of load distribution patterns. In addition, we propose to use a central station to broadcast the value of p_access in networks with poor collision detection capability, or long feedback delay. The proposed method is particularly suitable for shared channels with poor collision detection capability, under conditions of bursty traffic and a large number of users. Examples for such channels are the reservation channel in satellite-based networks with on-board processing, and the control channel in cellular networks. Hence, the proposed method can be used for cellular Internet access and for accessing public satellite-based networks. The broadcast mechanism that already exists in such networks can be used to inform the users the dynamic access probability.     

A network rate management protocol with TCP congestion control and fairness for all

Our study is motivated by the need to enable quality of service (QoS), congestion control and fair rate allocation for all end applications. We propose a new approach to address these needs which is different from the current practice whereby end applications pursue their own rate control using TCP. Our approach comprises a network rate management protocol (RMP) that controls the rate of all flows (at an aggregate level based on routes) subject to QoS requirements. The RMP control also facilitates a new TCP sliding-window congestion control based on the fair target rates computed by the RMP. Each non-TCP aggregate flow is policed by its respective edge router and each TCP flow adapts its window size as to achieve the RMP suggested fair target rate. The stability analysis of the new TCP congestion control is performed in a linearly scalable framework, which is less restrictive than a fluid model. We show that our proposed control is linearly scalable and establish its global asymptotic stability under arbitrary and variable information time lags, aka totally asynchronous conditions. The stability and the vitality of our control is verified by two means. One is a simulation of a network comprising 74 core links and up to 768 flows, each using its own access link. The simulation is also used to compare our control with the congestion control algorithms used in Fast, Vegas and Reno TCPs. The second verification means is an actual implementation of the control in the Linux kernel and its experimentation in a WAN testbed network comprising six routers and long haul links running UDP flows as well as CUBIC, N-RENO and C-TCP flows. Our experiments demonstrate that our approach can guarantee fair rates for all flows and QoS to premium flows.     

Efficient successor retrieval operations for aggregate query processing on clustered road networks

Get-Successors (GS) which retrieves all successors of a junction is a kernel operation used to facilitate aggregate computations in road network queries. Efficient implementation of the GS operation is crucial since the disk access cost of this operation constitutes a considerable portion of the total query processing cost. Firstly, we propose a new successor retrieval operation Get-Unevaluated-Successors (GUS), which retrieves only the unevaluated successors of a given junction. The GUS operation is an efficient implementation of the GS operation, where the candidate successors to be retrieved are pruned according to the properties and state of the algorithm. Secondly, we propose a hypergraph-based model for clustering successively retrieved junctions by the GUS operations to the same pages. The proposed model utilizes query logs to correctly capture the disk access cost of GUS operations. The proposed GUS operation and associated clustering model are evaluated for two different instances of GUS operations which typically arise in Dijkstra’s single source shortest path algorithm and incremental network expansion framework. Our simulation results show that the proposed successor retrieval operation together with the proposed clustering hypergraph model is quite effective in reducing the number of disk accesses in query processing.