A conceptual model of service customization and its implementation

With the development of Internet and next generation networks in telecommunications, more and more new services are required to be introduced into networks. Introducing new services into traditional network is always associated with standardizing new protocols. The progress of protocol standardization usually takes several years, which cannot meet the increasing demands of the applications in Internet and next generation networks. Service customization in network systems may be one possible solution to cope with this problem. Based on the principle that network service is provided by interactions among protocol entities, this paper proposes a conceptual model of service customization (SECUM) by separating the service logic from protocol interactive logic within existing network architecture. The theory of Communicating Sequential Processes (CSP) is used to formalize the SECUM in order to locate exactly the service logic and to define precisely the SECUM. For validating the SECUM‘s usability in practical network systems, this paper also proposes an implementation model for SECUM: a component-based protocol implementation model (CPIM). CPIM discomposes protocol entity into application component, service component, message component and communication component. Service component associates application component with message component. Users or network managers can customize network services by configuring service component. The paper shows respectively the applications of SECUM and CPIM by proposing a customizable IP service model based on SECUM and describing an implementation of Session Initiation Protocol (SIP) based on CPIM. Compared with the existing service-customization techniques, SECUM is a service customization model internal to network system and may provide more powerful capabilities of service customization.     

一个基于服务层叠网的分层服务组合框架

随着Internet上Web服务数量的不断增长,这些服务能够互联形成一个应用层的逻辑网络--服务层叠网(service overlay network,简称SON).基于SON,通过服务的组合提供增值服务,是满足用户动态、多变的功能及非功能需求的一种有效的方法.但是,已有基于SON的QoS感知的服务组合研究主要是面向服务间具有简单交互行为的应用领域,难以支持电子商务等具有复杂业务协作特征的应用场景.为此,通过使用业务协议刻画服务间的组合关系,从而构建更具普适性的SON;建立主动服务层叠网(active service overlay network,简称ASON)以实现可编程的服务层叠网,支持按需的服务组合;提出了一个基于主动服务层叠网的分层服务组合框架(hierachical service composition framework based on service overlay networks,简称HOSS),通过将业务协议(而不是消息)作为需求描述的基本单元,提升软件开发效率,并将服务组合需求映射为SON的动态用户视图以实现按需的组合.     

Synthesizing Distributed Protocol Specifications from a UML State Machine Modeled Service Specification

The object-oriented paradigm is widely applied in designing and implementing communication systems.Unified Modeling Language(UML) is a standard language used to model the design of object-oriented systems.A protocol state machine is a UML adopted diagram that is widely used in designing communication protocols.It has two key attractive advantages over traditional finite state machines:modeling concurrency and modeling nested hierarchical states.In a distributed communication system,each entity of the system has its own protocol that defines when and how the entity exchanges messages with other communicating entities in the system.The order of the exchanged messages must conform to the overall service specifications of the system.In object-oriented systems,both the service and the protocol specifications are modeled in UML protocol state machines.Protocol specification synthesis methods have to be applied to automatically derive the protocol specification from the service specification.Otherwise,a time-consuming process of design,analysis,and error detection and correction has to be applied iteratively until the design of the protocol becomes error-free and consistent with the service specification.Several synthesis methods are proposed in the literature for models other than UML protocol state machines,and therefore,because of the unique features of the protocol state machines,these methods are inapplicable to services modeled in UML protocol state machines.In this paper,we propose a synthesis method that automatically synthesizes the protocol specification of distributed protocol entities from the service specification,given that both types of specifications are modeled in UML protocol state machines.Our method is based on the latest UML version(UML2.3),and it is proven to synthesize protocol specifications that are syntactically and semantically correct.As an example application,the synthesis method is used to derive the protocol specification of the H.323 standard used in Internet calls.     

IP网中约束路由的一种算法研究

Internet的迅猛发展对网络提出了更高的要求,而原有的最努力服务不能适应新的应用的需求。为了使Internet继续发展,必须能够提供有服务质量(QoS)保证的服务。IETF提出了几种服务模型和机制来满足用户的需求,比较典型的有集成服务模型、区分服务模型和流量工程。约束路由是流量工程中的一个重要工具。该文分析了延迟的主要组成部分,用M/M/1模型来分析通过节点的时间和节点负荷率的关系,通过限制各节点负荷率提出了一种新的约束路由算法,这种尝试性的算法对约束路由的研究具有一定的启发意义。     

基于SMTP、POP3协议的电子邮件自动收发系统的开发

电子邮件是Internet上应用最多和最广的服务项目,SMTP(Simple Mail Transport protocol)和POP3(Post office protocol)是在电子邮件服务中分别负责收信和发信的两种协议。本文介绍了电子邮件系统的工作原理及相关协议,并基于这些协议设计和开发了一个实用的邮件系统。     

区分服务体系的服务质量机制浅析

一、前言随着Internet的应用和发展,特别是多媒体应用的需求,对服务质量的要求越来越高,端到端的服务质量已成为其发展的瓶颈,为此Internet工程任务小组(IETF)提出了不少相关保证Internet服务质量的体系模型,其中IntServ/RSVP(综合服务体系/资源预留协议)体系模型的服务质量最完善,但由于其需要复杂     

一种基于业务生成图的Web服务工作流构造方法

针对互联网中Web服务具有动态变化且迅速增长的特点,提出了一种面向用户需求的服务工作流构造模型.该模型将功能相同或相似的服务聚集成一类服务集合,每类服务集合采用生成树的方式组织,并依据工作流的业务逻辑关系形成业务生成图;同时,在重定义粒子群算法的位置、速度、加/减法和乘法的基础上,结合遗传算法中的交叉、变异操作,设计了基于混合粒子群的QoS(quality of service)调度方法,保证在可选服务不断增长时能够满足用户的个性化需求.实验结果表明,该模型能够有效地屏蔽组成工作流的Web服务物理上的变化与差异,较好地组合了Internet中的Web服务资源,适合于虚拟计算环境的应用要求.     

基于位置预查询的因特网移动支持方案

提出一种预查询移动支持方案(mobile Internet protocol_based on location pre-query,简称MIP_Q),以解决家乡网络的流量瓶颈和单点故障问题,从而提高移动通信的效率和可靠性.MIP_Q通过扩展域名服务系统管理和跟踪移动节点的当前位置信息,省去了家乡代理;采用并行切换控制方式,同时避免了MIP(mobile Internet protocol,简称MIP)中的三角路由和隧道路由问题;借助有效的计算方法,分析和比较了MIP_Q与MIP,MIP_LR的平均移动通信成本和切换时延;在实现方面与广泛应用的广域蜂窝移动网络进行了类比.结果表明:MIP_Q在切换效率和新增实体数等方面优于同类方案;MIP_Q可以极大地降低节点的移动通信成本,减小切换时延;MIP_Q具有良好的可行性.最后提出MIP_Q的仿真和实现方案.     

基于密码技术的网络安全服务的实现机制

随着网络的发展,安全服务日益成为影响网络效能的重要问题,解决这一问题的基础就是密码技术。介绍了密码技术,五类安全服务：认证服务(authentication service)、访问控制服务(access control service)、数据保密服务(data confidentiality service)、数据完整性服务(data integrity service)和不可否认服务(non-repudiation service)。在研究密码技术的五类安全服务基础上,通过对网络安全服务的分析,提出了基于密码技术的网络安全服务的实现机制。     

Internet网络的主动分布管理模型

Internet正在高速发展,它将逐渐取代POTS（plain old telephony service）网络。目前的Internet服务模型是简单的、自带寻址信息的服务。在这种环境下,对网络管理功能的需求是有限的,仅限于单元管理和对端对端能力的诊断。未来的Internet将是一个多服务的平台,支持实时通信和复杂的多用户服务。从技术角度看,这意味着需要扩展目前的Internet模型,需要加入服务质量（QoS）保证、资源预留方案（例如,资源预留协议,RSVP）、可靠性方案、安全框架、虚拟专用的网络服务和一个服务层协议（SLA）,并允许Internet服务提供商（ISP…     

主动Overlay物联网QoS服务路由算法研究

在物联网环境中,服务可能由任意多个结点汇聚而成,而传统的尽力而为的通信服务不能保证服务质量(QoS)。为此,首先提出了主动Overlay物联网服务路由逻辑拓扑结构,然后对物联网服务路由问题进行了建模。在此基础上,设计了基于Agent和蚁群优化(ACO)的主动Overlay物联网QoS蚁群服务路由算法。该算法结合移动A-gent对ACO进行了改进,实现了保证QoS的服务路径选择。最后从理论上证明了该算法的正确性和收敛性,同时通过仿真实验对该算法的实际性能进行了验证和比较。     

基于蚁群系统的动态QoS多播路由算法

基于蚁群系统的自组织能力,提出了一个分布式的动态QoS多播路由的算法。与其他算法不同,在该算法中,蚁群从多播组的目的结点出发进行搜索,将每次迭代选中的符合QoS约束且具有最小代价的路径加入到多播树中,而多播树以“拉”的模式分布式地被构造。仿真结果表明,与其他两种算法相比,该算法具有更好的性能,能够快速有效地找到动态QoS多播路由问题的全局最（近）优解。     

基于免疫遗传算法的多约束QoS路由选择算法

该文针对多约束Qos路由选择问题，将其转化为一个多约束赋权图最短路径问题，选择费用、带宽、时延、丢失率为Qos参数。设计了一个基于免疫遗传算法的Qos路由选择算法，该算法主要利用生物免疫机制中的抗原识别、抗原记忆和抗体的抑制、促进作用来控制收敛方向，促进快速求解。实验表明本文提出的算法具有较好的性能，大幅度地提高Qos路由选择的效率。     

基于SDN分级分域架构的QoS约束路由算法

传统分布式的网络架构制约路由算法的创新,软件定义网络的出现为路由算法的优化提供了新思路。已有研究中,启发式算法广泛应用于服务质量路由,但由于计算复杂度高而无法在大型网络中应用。而其他算法均存在不同程度的问题,要么复杂度较高,要么算法性能较差,如最短路径算法。基于 SDN 分级分域架构,提出了 LC-LD 路由算法,综合时延条件和代价度量约束并在计算复杂度和算法性能之间保持平衡。仿真分析表明,LC-LD路由算法在有较低的计算复杂度的同时还有较高的服务质量路由选路性能。     

Preemption-Aware Instantaneous Request Call Routing for Networks With Book-Ahead Reservation

This paper presents a new preemption-aware quality of service (QoS) routing algorithm for instantaneous request (IR) call connections in a QoS-enabled network where resources are shared between IR and book-ahead (BA) call connections. BA reservation, which confirms the availability of resources in advance, is a highly attractive technique for time sensitive applications that require high amount of bandwidth with guaranteed QoS. One of the major concerns for the implementation of BA reservation is the need for preemption of on-going IR calls to accommodate BA calls when resource scarcity arises. Preemption disrupts service continuity of on-going calls which is considered as severely detrimental from users' perceived QoS definition found in recent studies. Existing QoS routing algorithms focus on resource conservation or load balancing as the key objective to attain in addition to guaranteed QoS. No works have yet focused on the preemption problem of on-going IR calls at routing stage in the presence of BA calls. We present a mathematical formulation to compute the preemption probability of an incoming IR call at routing stage based on the current IR and future BA load information. We propose a routing strategy by formulating a link cost function comprising of the calculated preemption probability of the incoming IR call and hop count. Simulation results confirm that QoS routing based on the proposed link cost function significantly outperforms widely recommended shortest path and widest path routing algorithms in terms of IR call preemption and blocking rate. The proposed approach also yields higher network utilization and IR effective throughput.     

MPLS网络中QoS路由算法研究

论文着重研究了MPLS网络中QoS路由算法的设计问题。MPLS协议本身提供了QoS路由的机制,但有效的QoS路由算法却是其实现的保证。论文首先推导出代价函数公式,然后在此基础上提出了最小代价路由算法(LCR),根据MPLS网络节点获得的信息计算满足特定的QoS需求条件的最小代价路径。在模拟环境中,通过与SPF算法对比,此算法在保持路径利用率和平衡网络负载等方面具有明显优势。     

基于禁忌搜索的集成式QoS组播路由算法

研究了IP／DWDM光因特网中的集成式QoS组播路由算法,在考虑负载均衡的前提下,针对用户组播请求与柔性QoS需求,寻找一棵QoS组播路由树。由于该问题的NP难属性,因此基于禁忌搜索算法来构造费用近优QoS组播路由树,同时集成一种基于分段和波长图思想的波长分配算法,一体化解决路由与波长分配问题。仿真结果表明,提出的算法是可行和有效的。     

A Hybrid End-to-End QoS Path Computation Algorithm for PCE-Based Multi-Domain Networks

Inter-domain quality of service (QoS) routing is a challenging problem for today’s Internet. This problem requires the computation of paths that cross multiple domains and meet different QoS constraints. In addition, the used computation methods must meet the constraints of confidentiality and autonomy imposed by the domains of different operators. Path computation element (PCE)-based architecture offers a promising solution for inter-domain QoS routing. It ensures the computation of end-to-end QoS paths while preserving the confidentiality and the autonomy of the domains. In this paper, we propose a novel hybrid end-to-end QoS path computation algorithm, named HID-MCP, for PCE-based networks. HID-MCP is a hybrid algorithm that combines the advantages of pre-computation and on-demand computation to obtain end-to-end QoS paths. Moreover, it integrates a crankback mechanism for improving path computation results in a single domain or in multiple domains based on the PCE architecture. Detailed analyses are provided to assess the performance of our algorithm in terms of success rate and computational complexity. The simulation results show that our algorithm has an acceptance rate of the requests very close to the optimal solution; precisely, the difference is lower than 1 % in a realistic network. Moreover, HID-MCP has a low computational complexity. Besides, our solution relies on the PCE architecture to overcome the limitations related to inter-domain routing such as domain autonomy and confidentiality.     

An ant based multi constraints QoS aware service selection algorithm in Wireless Mesh Networks

Over the years, multihop Wireless Mesh Networks (WMNs) are providing cost effective services to the end users such as Video on demand (VoD), Voice over IP (VoIP), and Video conferencing in an efficient manner. Most of these services require an efficient service selection mechanism that can provide Quality of Service (QoS) in presence of various constraints such as delay, jitter, and service availability. In presence of these constraints, multi-constraint QoS aware service selection in WMNs is an NP-hard problem. In this paper, we propose an ant colony based multi constraints QoS aware service selection (QSS) algorithm. In the proposed algorithm, ants are launched from source node. The best path is chosen based upon the defined cost effective (CE) metric in presence of constraints. The constraints are chosen both from network and user perspectives. The goodness of the chosen path is determined by the CE metric. Moreover, ants are not launched randomly from the source node. They are launched based upon the guided search evaluation (GSE) criterion. This criterion is also used if the two paths have the same CE metric. The simulation results show that the proposed algorithm is more effective than the earlier improved ant colony QoS routing algorithm (IAQR) algorithm with respect to convergence, end-to-end delay (jitter), and service availability. Specifically, the service availability increases by 35–50% in the proposed QoS aware scheme compared to IAQR algorithm.