Performance evaluation of adaptive routing algorithms in packet‐switched intersatellite link networks

This paper addresses the performance evaluation of adaptive routing algorithms in non‐geostationary packet‐switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network‐uniform source/destination distribution model and a uniform source–destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri‐like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd.     

A middleware service for employing and evaluating resource management algorithms in distributed networks

The first part of this paper introduces the design of a middleware‐based service which is valuable for distributed networks for mainly managing their resources. The second part evaluates the performance of a distributed intelligent network (D‐IN), which comprises the proposed service together with a resource management algorithm. We test the network's performance by building and emulating its basic functionality, based on distributed object technology (DOT), in a real environment. The resource management algorithm mainly aims at avoiding congestion and balancing load. Its implementation uses the ICALB algorithm (Comput. Commun. 2002; 25 (17):1548–1556) model. Its incorporation is succeeded through the use and implementation of the distributed middleware‐based service. It is a CORBA‐based service that is used for successfully managing resource management algorithms, such as ICALB, facilitate their operation, and solving classes of problems related to communications over the distributed network, sharing of resources spread over the network, scheduling, synchronization, and management of various tasks. By this means we argue that the method that we use can be employed for operating in various distributed networks. We also evaluate the network's performance by measuring various D‐IN node parameters with critical meaning and by showing the improvements that appeared to the D‐IN from the operation of both the ICALB algorithm and the proposed service. Copyright © 2005 John Wiley & Sons, Ltd.     

下一代网络的体系结构及关键技术研究

网络技术的迅猛发展导致网络的异构性问题越来越突出,而各层次用户都要求新网络能够提供更加开放和稳定、高性能、可重用、可灵活定制的服务,这是原来相对封闭的专用服务平台和业务环境所无法提供的。基于各种考虑,下一代网络采用开放的网络架构体系,由业务驱动基于统一协议的分组网络。文中通过研究网络体系结构的演进,得出下一代网络体系结构应具有的特点及发展趋势,并对实现时所要求的关键技术进行了探讨。     

一种动态检测和解决下一代智能网中业务冲突的方法

在OSA/Parlay框架下，业务序列触发执行引起的业务冲突是一种常见的业务冲突，本文针对这种业务冲突的特点冲突提出一种通过业务请求重现来检测业务冲突的新方法。本文详细描述该方法的具体内容并介绍如何在基于Parlay／OSA API框架下——应用服务器与软交换的实验环境实现该方法，同时利用Parlay Specifications3．0中的部分增值业务检验该方法的有效性。实验结果表明：该方法能有效检测和解决由于业务序列触发而引起的业务冲突。     

业务光网络中光服务等级协定的研究

从业务光网络的角度对比服务等级协定(SLA)定义了光服务等级协定(O-SLA)的框架结构,在此基础上重点分析了O-SLA协商机制并提出一种动态协商的概念,对动态协商机制的实现流程进行了分析研究.随后总结了O-SLA得以有效实施的关键技术,并提出一种支持区分服务的O-SLA实施流程,此流程对于向端用户提供可定制化的光层业务提供了一种新思路.     

Reliability‐aware service chaining mapping in NFV‐enabled networks

Network function virtualization can significantly improve the flexibility and effectiveness of network appliances via a mapping process called service function chaining. However, the failure of any single virtualized network function causes the breakdown of the entire chain, which results in resource wastage, delays, and significant data loss. Redundancy can be used to protect network appliances; however, when failures occur, it may significantly degrade network efficiency. In addition, it is difficult to efficiently map the primary and backups to optimize the management cost and service reliability without violating the capacity, delay, and reliability constraints, which is referred to as the reliability‐aware service chaining mapping problem. In this paper, a mixed integer linear programming formulation is provided to address this problem along with a novel online algorithm that adopts the joint protection redundancy model and novel backup selection scheme. The results show that the proposed algorithm can significantly improve the request acceptance ratio and reduce the consumption of physical resources compared to existing backup algorithms.     

A location‐based service advertisement algorithm for pervasive service discovery in wireless mobile networks

The practical success of pervasive services running in mobile wireless networks relies largely on its flexibility in providing adaptive and cost‐effective services. Service discovery is an essential mechanism to achieve this goal. As an enhancement to our previous work for service discovery, that is, model‐based service discovery (MBSD), this paper proposes a location‐based service advertisement (SA) algorithm named as MBSD‐sa. MBSD‐sa advocates the importance of service location to the service availability and integrates the service location information together with the service semantic information into service information for advertisement. MBSD‐sa utilizes prediction to estimate the service location so as to reduce the number of SA messages (SAMs). Two complementary types of SA mechanisms (Types 1 and 2) are employed by MBSD‐sa to strike the balance between the SAM overhead and the accuracy of service information. The performance of MBSD‐sa is analyzed both numerically and using simulations. Copyright © 2008 John Wiley & Sons, Ltd.     

Quality‐of‐service‐aware cluster‐based service discovery approach for mobile ad hoc networks

This paper presents a quality‐of‐service (QoS) distributed service discovery approach for mobile ad hoc network environments. The approach builds upon a clustered topology, where the clusterhead (CH) is assigned additional roles having to do with maintaining a directory of services in the network and aggregating and computing QoS scores about service providers (SPs) from requesting nodes (RNs) and the providers themselves. To reduce the amount of overhead traffic, the design makes extensive use of piggybacking for relaying and updating the CHs with QoS scores. A mobile device that is interested in a certain service submits a request to its CH, which uses cached QoS data to return a ranked list of SPs that offer the type of requested service. On the basis of its interaction with the SP, the device sends the CH next time it makes a request a score reflecting its perception of the SP's QoS. Over time, the CH develops robust QoS data that it uses to help devices obtain the best available service. Theoretical analysis and experimental evaluation based on simulations prove the advantages of the proposed system and the effectiveness of its operations. Copyright © 2013 John Wiley & Sons, Ltd.     

智能光网络的业务特征和业务构架

在光网络上直接提供宽带、优质、动态、灵活、可控的新型传送业务是智能光网络未来发展的重要方向之一。依托智能化的控制平台、综合化的管理系统，能够充分挖掘光网络的带宽潜力，直接由光域生成各类新型业务，满足多样化、个性化的用户需求。有两类业务提供构架：基于管理的业务提供方案和基于扩展业务平面的业务提供方案。基于业务平面的业务提供方案是智能光网络的重要发展方向之一。     

VoIP traffic in wireless mesh networks: a MOS‐based routing scheme

Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd.     

TOPVISOR: Two‐level controller‐based approach for service advertisement and discovery in vehicular cloud network

Vehicular cloud is a kind of mobile cloud in which vehicles share their resources and provide services for each other. The first step in establishing a vehicular cloud network is the service advertisement and discovery. Due to the dynamic nature of vehicular cloud networks, services are not continuous and the service location may vary at any time depending on the vehicle location. Therefore, higher network traffic is generated to access the consistent and up‐to‐date information. In this paper, a two‐level hierarchical approach is proposed for service advertisement and discovery in vehicular cloud networks. To register the services' specification in this approach, the distributed directories in RSUs and central controllers are used. Moreover, a method is used to avoid extra update packets by localizing the updates. The simulation results show improvement in the packet delivery rate as well as a reduction in transmission bandwidth preventing the network congestion.     

Performance of fiber delay‐line buffers in asynchronous packet‐based optical switching networks with wavelength conversion

A major challenge in asynchronous packet‐based optical networks is packet contention, which occurs when two or more packets head to the same output at the same time. To resolve contention in the optical domain, two primary approaches are wavelength conversion and fiber delay line (FDL) buffering. In wavelength conversion, a contending packet can be converted from one wavelength to another in order to avoid conflict. In FDL buffering, contending packets can be delayed for a fixed amount of time. While the performance of wavelength conversion and FDL buffering has been evaluated extensively in synchronous networks with fixed‐sized packets, in this paper, we study the performance of FDL buffers in asynchronous packet‐based optical networks with wavelength conversion. An analytical model is proposed to evaluate the performance in terms of packet loss probability and average delay. Extensive simulation and analytical results show that, with appropriate settings, FDL buffers can perform much better in switches with wavelength conversion than in switches with no conversion. Copyright © 2014 John Wiley & Sons, Ltd.     

A framework for fiber delay‐line buffers in packet‐based asynchronous multifiber optical networks (PAMFONET)

A major challenge in packet‐based optical networks is packet contention, which occurs when two or more packets are heading to the same output at the same time. To resolve contention in the optical domain, a fundamental approach is fiber delay‐line (FDL) buffering, in which packets can be delayed for a fixed amount of time. In the literature, the performance of FDL buffering has been studied extensively. However, most existing works are based on an assumption that there is only one fiber per link in the network. In this paper, we address the architecture and performance of FDL buffers in packet‐based asynchronous multifiber optical networks (PAMFONET), in which each link in the network may consist of multiple optical fibers. We propose a framework for FDL buffers in PAMFONET, in which we provide three essential architectures and corresponding packet scheduling policies. Extensive simulation results show that, with appropriate settings, the same number of FDLs can lead to better performance in multifiber networks than in single‐fiber networks. Copyright © 2011 John Wiley & Sons, Ltd.     

Space‐time diversity‐enhanced QoS provisioning for real‐time service over MC‐DS‐CDMA based wireless networks

In order to support the quality‐of‐service (QoS) requirements for real‐time traffic over broadband wireless networks, advanced techniques such as space‐time diversity (STD) and multicarrier direct‐sequence code division multiple access (MC‐DS‐CDMA) are implemented at the physical layer. However, the employment of such techniques evidently affects the QoS provisioning algorithms at the medium access control (MAC) layer. In this paper, we propose a space‐time infrastructure and develop a set of cross‐layer real‐time QoS‐provisioning algorithms for admission control, scheduling, and subchannel‐allocations. We analytically map the parameters characterizing the STD onto the admission‐control region guaranteeing the real‐time QoS. Our analytical analyses show that the proposed algorithms can effectively support real‐time QoS provisioning. Also presented are numerical solutions and simulation results showing that the STD can significantly improve the QoS provisioning for real‐time services over wireless networks. Copyright © 2007 John Wiley & Sons, Ltd.     

Split agent‐based routing in interconnected networks

Adaptive behaviour of swarm‐based agents (BT Technol. J. 1994; 12 :104–113; AAMAS Conference '02, Melbourne, Australia, Month 1–2, 2002; Softcomput. J. 2001; 5 (4):313–317.) is being studied in this paper with respect to network throughput for a certain amount of data traffic. Algorithmically complex problems like routing data packets in a network need to be faced with a dynamically adaptive approach such as agent‐based scheme. Particularly in interconnected networks where multiple networks are participating in order to figure a large‐scale network with different QoS levels and heterogeneity in the service of delay sensitive packets, routing algorithm must adopt in frequent network changes to anticipate such situations. Split agent‐based routing technique (SART) is a variant of swarm‐based routing (Adapt. Behav. 1997; 5 :169–207; Proceedings of 2003 International Symposium on Performance Evaluation of Computer and Telecommunication Systems—SPECTS, Montreal, Canada, July 20–24, 2003; 240–247.) where agents are split after their departure to the next node on a hop‐by‐hop basis. Packets that are delay sensitive are marked as prioritized which agents recognize‐as being a part of a packet‐ and try to influence the two‐way routing tables. Thorough examination is made, for the performance of the proposed algorithm in the network and the QoS offered, taking into account a number of metrics. It is shown that the split agent routing scheme applied to interconnected networks offers a decentralized control in the network and an efficient way to increase overall performance and packet control reducing at the same time the packet loss concept. Copyright © 2004 John Wiley & Sons, Ltd.     

Incomplete cooperation‐based service differentiation in WLANs

In the IEEE 802.11 wireless LAN (WLAN), the fundamental medium access control (MAC) mechanism—distributed coordination function (DCF), only supports best‐effort service, and is unaware of the quality‐of‐service (QoS). IEEE 802.11e enhanced distributed channel access (EDCA) supports service differentiation by differentiating contention parameters. This may introduce the problem of non‐cooperative service differentiation. Hence, an incompletely cooperative EDCA (IC‐EDCA) is proposed in this paper to solve the problem. In IC‐EDCA, each node that is cooperative a priori adjusts its contention parameters (e.g., the contention window (CW)) adaptively to the estimated system state (e.g., the number of competing nodes of each service priority). To implement IC‐EDCA in current WLAN nodes, a frame‐analytic estimation algorithm is presented. Moreover, an analytical model is proposed to analyze the performance of IC‐EDCA under saturation cases. Extensive simulations are also carried out to compare the performances of DCF, EDCA, incompletely cooperative game, and IC‐EDCA, and to evaluate the accuracy of the proposed performance model. The simulation results show that IC‐EDCA performs better than DCF, EDCA, and incompletely cooperative game in terms of system throughput or QoS, and that the proposed analytical model is valid. Copyright © 2010 John Wiley & Sons, Ltd.     

Demand‐driven server and service location in third generation mobile networks

In this paper, we formulate and solve the problem of how to dynamically distribute network resources in third‐generation mobile telecommunication systems, aiming to minimize the equipment maintenance and service provision costs. A mobility simulator was implemented in order to represent a hypothetical city, which was populated with different groups of users, whose mobility behavior and demand for different kinds of services was generated in order to simulate a typical 24‐h day behavior. Given the generated demand at a certain period of time, a server allocation is made in order to attend it. This is done by modeling the system as an integer‐programming problem and by, afterwards, running an optimization algorithm on it. The output from the optimization process was used to reconfigure the system by activating the selected servers and deactivating the others. The problem turned out to be NP‐hard, so a heuristic method was necessary in order to solve it. We chose the Lagrangean relaxation technique to do the task, and obtained good results in terms of the solution proximity to the optimum. The performed experiments demonstrated the model's sensitivity to different kinds of parameters, such as user mobility, demand distribution over time and space, time of day, type of area where events occur, and the relation between fixed and variable costs of the system. A significant system cost reduction was also achieved. The proposed approach allows a personalized and demand driven resource distribution. Copyright © 2006 John Wiley & Sons, Ltd.     

JPEG forensics scheme for signature embedding and packet‐level detection

As the volume of multimedia digital information transmitted over the Internet continues to rise, the problem of preventing the unauthorized tampering and dissemination of digital content has emerged as a major concern. Thus, the present study proposes a forensic scheme for tracking the dissemination of copyright‐protected JPEG images over the Internet. The proposed scheme incorporates two basic mechanisms, namely signature embedding and signature detecting. To preserve the quality of the protected JPEG images, the signature is embedded at the application layer. By contrast, the signature detection process is performed at the packet level in order to improve the scalability of the proposed mechanism. For any flows regarded as suspicious, the signatures embedded in the JPEG packet trains are compared with the known digital signatures for forensic purposes. The experimental results show that the embedded signature has no effect on the visual quality of the JPEG image. Moreover, it is shown that the computational complexity of the proposed detection scheme is significantly lower than that of existing application‐level schemes. Thus, the scheme provides an ideal solution for the forensic analysis of JPEG streams over large‐scale network environments such as the Internet. Copyright © 2013 John Wiley & Sons, Ltd.     

基于现网的VoLTE组网测试及智能网业务继承研究

简要阐述了VoLTE的原理及基本组网架构,重点研究了某通信运营商基于现网架构的VoLTE试验网、实际组网测试及主要的智能网业务在VoLTE组网中的继承测试,以期为VoLTE的商用部署时智能网业务的继承提供积极的决策参考。     

Utility‐based probabilistic call admission control for complete fairness in wireless networks

Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.