多光纤WDM网中支持QoS的波长重路由算法

在WDM网上，波长连续性限制会降低网络的信道利用率，增加光路建立请求的阻塞率。采用波长重路由技术可以减少波长连续性限制对网络性能的影响。该文采用波长图模型，对多光纤WDM网中支持QoS的波长重路由算法进行了探讨，提出一种支持QoS的波长重路由算法－－动态选择法，并采用两种网络模型，在不同负载的动态业务下对所提算法进行了仿真研究；仿真结果表明所提算法既满足了上层业务不同的QoS要求，同时又充分利用了有限的网络资源，使全网的平均阻塞率降低。     

一种新的基于业务等级的波长分配算法

提出了一种新的基于业务等级的WDM波长分配算法-MIT(最小影响门限法),并采用三种网络拓扑,在不同负载的动态业务下对所提算法进行了研究,仿真结果表明该算法既满足了上层业务不同QoS需要,同时又充分利用了有限的网络资源,使全网的平均阻塞率降低。     

支持多优先级QoS的业务量疏导算法

针对当前业务量疏导研究中很少涉及的QoS约束的问题,提出并研究了一种支持多优先级QoS的业务量疏导算法（Differentiated Traffic Grooming Algorithm,DTGA）,该算法综合考虑了对不同等级业务QoS和网络资源利用率的优化。与目前实用的WDM光网络业务量疏导算法的性能仿真对比表明,DTGA能有效地降低高服务等级需求业务的阻塞率和节省网络资源。     

WDM光网络中支持QoS的波长分配算法

基于在波长可变光网络中的波长分层图模型,本文提出了一种在动态业务情况下的支持不同QoS要求的路由波长分配算法,根据客户层业务不同的QoS要求,通过分层图模型中参数的不同取值,对其光路建立请求区别对待,提供不同级别的光路建立.仿真结果表明该算法具有很好的性能,提高了全网的资源利用率,满足了客户层业务在建立光通路时不同的QoS要求对网络阻塞率的要求.     

支持多优先级QoS的业务量疏导算法

文章针对当前波分复用(WDM)光网络中业务量疏导技术研究的局限性,提出支持多优先级服务质量(QoS)的业务量疏导算法--MTGA.该算法基于业务流QoS的需求,将业务标记为不同等级,然后尽量选择占用跳数最少的通路来建立连接.仿真结果显示,与已有算法相比,MTGA能够有效地降低有时延约束连接请求的阻塞率.     

多光纤WDM网中的QoS路由算法

利用区分光业务(DOS)模型可以将WDM光传送网中客户层(如IP)具有不同QoS要求的业务汇聚力较粗粒度的流,直接映射到光信道上,从而使客户层业务的不同QoS要求可以体现在DOS域的边缘光节点处的光路建立请求的不同优先级上。该文首先探讨了如何将多光纤WDM网转化为波长图,从而一次性解决选路和分配波长(RWA)问题,在此基础上,提出两种用于多光纤WDM网的QoS路由算法,对二者进行了比较,并进行了计算机仿真。     

抗毁WDM网络中支持多优先级的波长分配算法

WDM网络将在未来的骨干网中扮演重要的角色,具备抗毁能力和支持多优先级都很必要.本文提出了两种基于优先级的波长分配算法——波长编号法和分配限额法,并研究了动态业务下,抗毁WDM网络使用这两种波长分配方法后网络的阻塞率性能.研究的内容包括业务量负载、光纤链路的波长通道数和每条链路包含的光纤数对网络性能的影响.本文还给出了仿真结果.     

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。     

MPLS over WDM光互联网中多优先级标记交换路径路由算法研究

该文针对分层图模型的局限,设计了结点光收发器数受限的MPLS over WDM光互联网的扩展分层图。提出并研究了MPLS over WDM光互联网中具有不同QoS约束的多种优先级标记交换路径的路由算法区分综合路由算法(Differentiating Integrated Routing Algorithm , DIRA)。该算法综合考虑了对标记交换路径QoS的满足和网络资源的优化利用。与目前实用的WDM光网络路由算法的性能仿真对比表明,DIRA在提高网络总的吞吐量,降低有时延约束标记交换路径的阻塞率方面,性能更优。     

WDM抗毁网中考虑链路故障相关性的双链路失效保护算法

光纤链路由于共享了相同的物理资源,因此具有一定的故障相关性。这种故障相关性可以用相关链路失效概率(Correlated Link Failure Probability,CLFP)来表示。在CLFP基础上,该文研究了WDM抗毁网中双链路失效问题,提出了一种新的支持用户区分可靠性(Differentiated Reliability,DiR)的共享通路保护算法:SPPDLF-DiR (Shared-Path Protection for Dual-Link Failures with DiR)。仿真表明,SPPDLF-DiR在满足用户区分可靠性要求的前提下,能有效地提高资源利用率和降低业务阻塞率。     

Improved EDF-based management of the setup of connections in opaque and transparent optical networks

The need to support the diverse quality-of-service (QoS) requirements of the ever-emerging Internet applications is a major challenge for optical network operators. This paper tackles such a challenge through the definition of a QoS-aware optical connection setup management scheme. The proposed scheme utilizes the Earliest Deadline First (EDF) queueing discipline to schedule the setup of optical connections that cannot be established due to lack of optical resources. The EDF-based approach aims at minimizing blocking probability while realizing QoS differentiation. Blocking probability reduction is realized through the insertion of blocked connection requests into a queue giving them thus a second chance with respect to network access. QoS differentiation on the other hand is achieved as follows. The blocked connection requests are ranked in the EDF queue according to their connection setup requirements, which are viewed as deadlines during connection setup. In this way, pending connection requests having shorter setup time requirements are guaranteed to experience better QoS compared to the ones having longer setup time requirements. The performance of the EDF-based strategy is analyzed through extensive simulations in the context of both opaque and transparent NSFNET network topologies. The reported results show that the proposed strategy yields remarkable reduction in terms of blocking probability while effecting QoS differentiation.     

Quality-of-Service Based Protection in MPLS Control WDM Mesh Networks

Intelligent methods for automatic protection and restoration are critical in optical transport mesh networks. This paper discusses the problem of quality-of-service (QoS)-based protection in terms of the protection-switching time and availability for end-to-end lightpaths in a WDM mesh network. We analyze the backup lightpath-sharing problem in such networks and study the correlation of the working lightpaths and the impact of the correlation on the sharing of the backup lightpaths. We present a multi-protocol-label-switching (MPLS) control-based fully distributed algorithm to solve the protection problem. The proposed algorithm includes intelligent and automatic procedures to set up, take down, activate, restore, and manage backup lightpaths. It greatly reduces the required resources for protection by allowing the sharing of network resources by multiple backup lightpaths. At the same time, it guarantees, if possible, to satisfy the availability requirement even with resource sharing by taking the correlation of working lightpaths into consideration. A simple analysis of the proposed algorithm in terms of computation time and message complexity indicates that the implementation of the algorithm is practical. The illustrative studies that compare the performance of 1:1, unlimited sharing, and QoS-based backup sharing algorithms indicate that QoS-based sharing achieves comparable performance as unlimited sharing, which is much better than the 1:1 backup scheme in terms of connection blocking probability, average number of connections in the network for a given offered load, and network resource utilization.     

Dynamic connection provisioning with shared protection in IP/WDM networks

Internet protocol (IP) traffic connections arrive dynamically at wavelength‐division multiplexing (WDM) network edges with low data rates compared with the wavelength capacity, availability, and quality‐of‐service (QoS) constraints. This paper introduces a scheme to be integrated into the control and management plane of IP/WDM networks to satisfy the availability and QoS required for IP traffic connections bundled onto a single wavelength (lightpath) in WDM networks protected by shared‐backup path protection (SBPP). This scheme consists of two main operations: (i) routing multi‐granular connections and traffic grooming policies, and (ii) providing appropriate shared protection on the basis of subscribers’ service‐level agreements in terms of data rate, availability, and blocking probability. Using the Markov chain process, a probabilistic approach is developed to conceive connection blocking probability models, which can quantify the blocking probability and service utilization of M:N and 1:N SBPP schemes. The proposed scheme and developed mathematical models have been evaluated in terms of bandwidth blocking ratio, availability satisfaction rate, network utilization, and connection blocking probability performance metrics. The obtained research results in this paper provide network operators an operational setting parameter, which controls the allocation of working and backup resources to dynamic IP traffic connections on the basis of their priority and data rate while satisfying their requirements in terms of bandwidth and availability. Copyright © 2013 John Wiley & Sons, Ltd.     

A Call Admission Control Mechanism Using Mobility Graph in Mobile Multimedia Networks

One of the important issues in providing efficient multimedia traffic on a mobile computing environment is to guarantee the mobile host (client) with consistent QoS (Quality of Service). However, the QoS negotiated between the client and the network in one cell may not be honored due to client mobility, causing hand-offs between cells. In this paper, a call admission control mechanism is proposed to provide a consistent QoS guarantee for multimedia traffic on a mobile computing environment. Each cell can reserve fractional bandwidth for hand-off calls to its adjacent cells. It is important to determine the right amount of bandwidth reserved for hand-off calls because the blocking probability of new calls may increase if the amount of reserved bandwidth is more than necessary. An adaptive bandwidth reservation based on a mobility graph and a 2-tier cell structure is proposed to determine the amount of bandwidth to be reserved in the cell and to control dynamically its amount according to network conditions. We also propose a call admission control based on this bandwidth reservation and ``next-cell prediction' scheme using a mobility graph. In order to evaluate the performance of our call admission control mechanism, we measure metrics such as blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of existing mechanisms such as NR-CAT2, FR-CAT2, and AR-CAT2.     

WDM光网络的多优先级业务疏导机制

IP over WDM网络中,业务疏导能有效提高波长带宽利用率.然而,单一化的业务疏导机制难以满足不同业务的QoS要求,也很难做到经济合理地使用光路.提出了一种支持多优先级业务的疏导机制,该机制根据光路传输的时延和丢包特性来选择恰当的疏导路径,同时,该机制结合了抢占和流量分割技术,能有效地实现流量分割和多路抢占,降低了业务的阻塞概率.仿真结果显示,该疏导机制在保证业务QoS的同时,降低了高优先级业务的阻塞概率;在业务负载低时,能有效减少抢占.     

A path-disjoint approach for blocking probability analysis in hybrid dynamic wavelength routed WDM grooming networks

The present article addresses a novel approach to enhance the overall performance of a WDM optical network. Centralized and distributed approaches for dynamic lightpath establishment are well studied in the literature. Both the approaches have some drawbacks. In this article a hybrid approach is proposed to accept the advantages and discard the disadvantages of both the approaches. With the proposed hybrid approach, a WDM optical network is divided into clusters of nodes. Within a cluster centralized mechanism is applicable whereas connection requests between the node pairs from different clusters follow the distributed mechanism. Also, in this article an analytical model is proposed to compute the expected blocking probability of the proposed hybrid network. First, blocking probabilities for the centralized and distributed approaches are computed and then it is extended for the hybrid approach. The distinguished feature of the proposed analytical model is that it efficiently utilizes the path information of the calls to determine the overall blocking probability of a WDM optical network. It extracts the necessary parameters of a network by simulation and utilize the information to analytically calculate the blocking probability of the network. The NSFNET T1 backbone network is used for the simulation study. To justify the analytical model, the simulation results are compared with that of the analytical model. The simulation results establish the effectiveness of the proposed hybrid approach over the distributed approach in merits of both the call setup time and blocking probability.