业务量疏导WDM网状网中的动态子通路保护算法

该文研究了业务量疏导WDM网状网中的生存性问题,提出一种自适应子通路保护(ASPP)算法。该算法根据网络当前状态以及到达业务连接请求的带宽要求动态调整链路权值;在此基础上选择一条最短路作为工作通路,然后将该通路分为互不重叠的n段子通路(每段经过的链路数为m),并分别找出各自的保护通路。仿真结果表明:ASPP既可以保证业务连接的可靠性要求,同时又允许网络管理者根据一定优化策略调整m值,从而可以在资源利用率和恢复时间之间进行折中。     

GMPLS网络中的混合共享光路保护算法

提出了一种混合共享光路保护(HSLP)算法,用以解决通路保护方法中备份路径建立成功率低的问题.在本算法中,首先执行通路保护方法,如果备份路径建立失败,则动态划分工作路径段.用户的服务请求,包括恢复时间和可靠性等,可以通过限制备份路径的跳数来满足.仿真结果表明,HSLP 算法不仅能够获得较低的保护失败率,而且可以使资源利用率与平均恢复时间获得更好的折中.     

WDM网状网中基于共享风险链路组限制的业务量疏导算法

该文研究了业务量疏导WDM网状网中如何建立可靠的业务连接问题,提出一种新的基于共享风险链路组(SRLG)限制的共享通路保护算法。该算法既可以保证用户业务不同的可靠性要求,同时又能够有效提高全网的资源利用率,从而大大降低全网的业务阻塞率。该文还对所提算法进行了仿真研究,并给出了仿真结果。     

云计算中SLA的分层监测研究

在云计算这个松耦合的服务环境中,为了保证服务的质量,用户和服务提供者之间必须签订SLA协议,来保证服务的正常交互。对于服务提供者来说,他们不知道这些高层的SLA属性怎么转化到底层的度量值或者参数上去,云中服务实现方式的多样性导致这个问题更加复杂。文章首先定义了云中常用的QoS属性,然后提出了一个基于分层、自下而上的SLA监测模型,最后根据模型建立系统实现框架。     

IP/MPLSoverWDM网中基于共享风险链路组限制的共享通路保护算法

本文研究了IP/MPLS over WDM网中,如何建立两条共享风险链路组(SRLG)分离的标记交换路径(LSP)问题,提出一种新的基于SRLG分离的共享通路保护算法.该算法既可以保证用户业务的可靠性要求,同时又能够有效提高全网的资源利用率,从而大大降低全网LSP建立请求的阻塞率.本文还对所提算法进行了仿真研究,并给出了仿真结果.     

IP骨干路由器的速率限制和信息流管制功能

人们为了更好地得到服务提供者（SP）网络提供的服务,愿意在承担合理费用的前提下和服务提供者约定服务等级（SLA）服务提供者网络必须为用户提供相应的服务,而且服务质量不能受网络负载变化的影响,因此,服务提供者必须找到一种方法能够将共享网络资源分发给不同的用户和应用,而且必须能够管理进入SP网络信息流的流量和速率,因为只有这样才能保证每一个用户的基本服务。本文介绍了在Juniper Networks M系列路由器上实现的并受到JUNOS Internet软件支持的速率限制和信息流管制工具,同时也介绍了一些有关速率限制和信息流管制的基础知识。     

WDM疏导网络的共享子通路保护算法

研究了WDM疏导网络中的生存性问题,提出一种支持多粒度业务的共享子通路保护算法(GSSP)。GSSP首先根据网络当前状态动态调整链路权值,在此基础上选择一条最短路作为工作通路;然后将该通路分为互不重叠的等长子通路,分别找出它们的保护通路,并且允许共享保护资源。GSSP可以保证业务连接的可靠性,又允许网络管理者根据不同的优化策略调整子通路长度,可以在恢复时间和资源利用率之间进行折中。最后对GSSP进行了仿真研究,给出了仿真结果。     

基于改进SLA的运营支撑系统服务模型研究

针对当前静态SLA不能满足越来越普遍的用户实时服务请求的问题,本文提出一种改进的动态SLA服务模型,并应用到广西移动的运营支撑系统中,解决业务层SLA参数与系统层进程及设备属性参数映射问题。并根据该模型实现了一个原型系统,可根据支撑系统的当前状态自适应调整业务层SLA参数,实时响应用户对移动服务的在线请求,提高系统资源利用率,实现在系统资源有限的情况下最大限度满足用户在线请求,并确保对于用户申请业务的不同,提供相应的服务质量保证。     

网管系统中的服务水平管理

消费者对运营商的选择促使运营商开始对其服务质量进行承诺,导致了服务等级协议(SLA)的产生和发展.在建设新的业务支撑系统时,需要按照SLA管理的思路,在用户业务层、用户网络层、运营商内部业务层、运营商网络层和运营商的其它运营、维护和支撑系统之间建立SLA管理系统.在对已经部署的网管进行改造提供SLA支撑时,需要从服务性能数据收集和分析以及服务故障后服务恢复时间的度量两个方面着手进行.     

中兴:以太网—城域网的未来

目前城域以太网面临着六大问题:1.端到端的QoS保证QoS保证是运营商对用户的服务承诺,如何合理的充分利用现有资源,保证用户数据所要求的QoS特性是网络性能的体现。网络必须具备端到端的服务保障,以达到目前运营商提供的专线连接水平。实现端到端QoS需要解决的几个问题是:如何快速接纳新业务;如何公平调度和监管流量;如何选择最佳路径以及拥塞情况下的包处理。中兴通讯认为这些问题的解决主要依赖于MPLS的发展,MPLS可以无缝地在以太网上运行。2.业务保护机制目前的网络拓扑中都强调了避免单点故障,同时要求故障恢复的时间要尽可能的短…     

A generalized protection framework using a new link-State availability model for reliable optical networks

This paper investigates a generalized protection framework for availability-guaranteed connection provisioning in an optical wavelength-division-multiplexed (WDM) network. Reliability is a crucial concern in high-speed optical networks. A service level agreement (SLA), which mandates high service availability even in the face of network failures must be met in provisioning a reliable connection. In this study, a new link-state-modeling mechanism is developed to form a dynamic link-state parameter called link and resource availability (LRA), which represents physical-layer availability and resource status for an optical link. Such up-to-date link-state information can be used by a standard link-state routing protocol to efficiently provision reliable connections. Based on the link-state availability model, LRA, a connection-provisioning algorithm is then proposed which can guarantee customers' availability requirements. A new generalized protection model is developed through dynamic LRA-based provisioning. Numerical results demonstrate the performance of the proposed provisioning approach to be promising.     

A novel multicast traffic engineering technique in SDN using TLBO algorithm

In recent years, multicast communication is widely used by network providers to deliver multimedia contents. Quality of service (QoS) provisioning is one of the most important issues while transmitting multimedia contents using multicast. Traditional IP multicasting techniques suffer from reliability, scalability and have limitations to provide appropriate QoS for multimedia applications based on service level agreement (SLA). Nowadays, the advent of software defined networking (SDN), enables network providers to manage their networks dynamically and guarantee QoS parameters for customers based on SLA. SDN provides capabilities to monitor network resources and allows to dynamically configure desired multicasting policies. In this paper, we proposed a novel multicasting technique to guarantee QoS for multimedia applications over SDN. To deliver multimedia contents in an efficient manner, our proposed method models multicast routing as a delay constraint least cost (DCLC) problem. As DCLC problem is NP-Complete, we proposed an approximation algorithm using teaching–learning-based optimization to solve this problem. We evaluated our proposed method under different topologies. Experimental results confirmed that our proposed method outperforms IP multicast routing protocol, and it achieves a gain of about 25% for peak signal-to-noise ratio.     

波分复用波长路由节点的阻塞特性分析

利用概率统计理论的方法，从节点层次上定量分析了节点规模、复用波长数目以及波长转换对波分复用(WDM)波长路由网络中波长路由节点的影响。提出了基于概率统计的节点阻塞模型。数值结果突出表明波长转换能力越强的全光节点，其性能越优。为了提高网络资源的使用效率并增强全光网络的灵活性，必须实现全光网络中的虚波长路由波长转换器。通过数值计算找到了阻塞性能和代价的折中，研究中发现配置较低波长转换能力波长转换器的波长路由节点将会具备更强的性价比优势，当前在构建光通信系统时使用弱波长转换能力的光节点更可行。     

Service-Centric Provisioning in WDM Backbone Networks for the Future Internet

A service level agreement (SLA) is a formal contract between the service provider (SP) and the customer. Among various specifications, the SLA states an availability requirement and a penalty the SP pays if this requirement is violated. Traditional approaches to protection use a fixed deployment of backup resources, or do not consider the status of a service. As more heterogeneous applications use optical wavelength-division multiplexing (WDM) backbone network services of the future internet, these service-agnostic approaches are unable to accommodate the differentiated availability requirements. This results in substantial revenue loss either by refusing requests, or by accepting them and then violating their SLAs. In this paper, we propose and investigate the characteristics of a centralized control and management framework for service-aware, admission, and re-provisioning (SAR) in WDM backbone networks of the future internet. Our framework aggressively admits service requests, and dynamically reprovisions existing services by exploiting knowledge of their status. We first propose a GMPLS-based architecture and a revenue model for our analysis. Then we introduce a priority index, called urgency level (UL). An UL is assigned to an existing service indicating its status and relative importance, technically and economically. We reprovision resources by shifting them from low-UL services to provide backups for higher-UL services, which are more at risk of violating their SLAs or which have higher penalties. Our framework increases the revenue for the SP by creating more sales revenue and reducing potential penalties. Numerical results show improved performance in terms of 1) lower resource overbuild; 2) lower bandwidth blocking ratio; 3) higher SLA satisfaction ratio; 4) more balanced SLA violations; and 5) higher overall net revenue. Our framework is also shown to be effective for a range of failure models and penalty strategies.      

一种具有自调整功能的多信道EDFA放大模块

为克服常规ＥＤＦＡ在波分复用系统中由于增益不平衡造成各信道功率弥散的困难，本文提出了一种具有自调整功能的多信道ＥＤＦＡ放大模块。该放大模块在一对波分复用器之间平行地放置一套共享泵浦源的掺饵光纤放大器。其主要优点是在波分复用系统应用时，各波长信道之间的功率弥散不会随着放大模块的级联而积累。相反，该模块可以自动抑制由于波分复用网络中器件和线路的不同损耗造成的接收功率的起伏。系统容量可以简单地通过分组密集波分复用的方式实现。由于采用了泵浦共享，系统的费用不会很大增加。文中利用计算机实验模拟，证明了该模块的良好性能。     

Wavelength assignment for multicast in all-optical WDM networks with splitting constraints

Multicast is an important application in all-optical WDM networks. The wavelength assignment problem for WDM multicast is to assign a set of wavelengths to the links of a given multicast tree. In an all-optical WDM network without wavelength conversions, wavelength assignment is the key to guarantee the quality of service and to reduce communication costs. In this paper, we study wavelength assignment for WDM multicast with two criteria, to cover the maximum number of destinations, and to minimize the wavelength costs. The computational complexity of the problem is studied. Three heuristic algorithms are proposed and the worst-case approximation ratios for some heuristic algorithms are given. We also derive a lower bound of the minimum total wavelength cost and an upper bound of the maximum number of reached destinations. The efficiency of the proposed heuristic algorithms and the effectiveness of the derived bounds are verified by the simulation results.     

Priority-based Dynamic Lightpath Allocation for Survivable WDM Networks

In recent years, there has been considerable research interest in the design of survivable wavelength division multiplexing (WDM) networks. Many papers have proposed mixed-integer linear program (MILP) formulations as well as heuristics to optimally allocate lightpaths, using protection based schemes. Such schemes provide quick and guaranteed recovery, but do not use resources efficiently. About 50% of allocated resources remain idle, under fault-free conditions. If these “idle” resources were used for low-priority connections (which could be pre-empted if necessary), the resource utilization would improve significantly. This paper introduces two MILP formulations for priority-based dynamic lightpath allocation in survivable WDM networks. We define three different levels of service and allocate resources based on the requested service level. An important advantage of our approach is that while we can handle multiple levels of service, the traditional (single level) shared and dedicated path protection schemes can be treated simply as a special case of the proposed formulations. The first formulation solves the problem optimally, but is quite time consuming. The second formulation makes some simplifications, and is more efficient. The results demonstrate that our approach can significantly improve resource utilization and is feasible for practical sized networks, particularly under low- to medium-traffic load. For large networks and high traffic conditions, simpler heurtistic algorithms are more appropriate. In such cases, the proposed MILP formulation can be a useful tool to validate the performance of the heuristics.     

A cost-based scheduling algorithm for differentiated service on WDM optical networks

One of the important issues in the design of future generation of high-speed networks is to provide differentiated services to different types of traffic with various time constraints. We propose an adaptive scheme to manage message transmission in single-hop passive-star coupler based wavelength-division multiplexing (WDM) optical networks. This study suggests that when scheduling message transmission in WDM networks a differentiated service should be considered in order to meet the time constraint to transmission of real-time messages while non real-time messages are being served so that the overall performance of the network could be improved.     

A balancing scheme for QoS-aware service provisioning in OPS networks

The service level agreement (SLA) specifies the service availability that a service provider promises to a customer. Through introducing SLA into optical packet switching networks, a balancing scheme for quality of service-aware service provisioning is proposed, which uses packet loss ratio as availability index to obtain a larger number of SLA-satisfied services and achieve a better balance among different level services by means of discarding packets with better packet loss capacity in priority to fully make use of the capacity of services themselves. The theoretical analysis and simulation results show that the proposed scheme outperforms the other two typical service provisioning schemes in terms of the above two aspects.     

Efficient Scheduling Algorithms for Real-Time Service on WDM Optical Networks

One of the important issues in the design of future generation high-speed networks is the provision of real-time services to different types of traffic with various time constraints. In this paper we study the problem of providing real-time service to hard and soft real-time messages in Wavelength-Division-Multiplexing (WDM) optical networks. We propose a set of scheduling algorithms which prioritize and manage message transmissions in single-hop WDM passive star networks based on specific message time constraints. In particular, we develop time-based priority schemes for scheduling message transmissions in order to increase the real-time performance of a WDM network topology. We formulated an analytical model and conducted extensive discrete-event simulations to evaluate the performance of the proposed algorithms. We compared their performances with that of the state-of-the-art WDM scheduling algorithms which typically do not consider the time constraint of the transmitted messages. This study suggests that when scheduling real-time messages in WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their time constraints.