基于GMPLS的光突发交换网络的研究

文章基于通用多协议标签交换(GMPLS)的光突发交换(OBS)网络的体系结构,研究了如何将GMPLS引入OBS,并使两者能够高效协调地工作.重点讨论了GMPLS与OBS技术相结合的网络(GMPLS-based OBS)的各种关键技术和解决机制.特别在处理突发数据包(BDP)冲突竞争机制上提出了新的方法.最后,指出了GMPLS-based OBS进一步研究的方向.     

基于GMPLS的光突发交换体系及其关键技术

文章给出了基于通用多协议标签交换(GMPLS)的光突发交换(OBS)对等体系(GLOBS)的功能结构和分层视图.在此范畴内,针对标签空间减小和流量工程两方面,结合国内外最新的研究动态,比较了各种已有技术的优缺点,并提出了适合于GLOBS体系的可能的解决方案以及今后工作的重要技术问题.     

混合光突发交换网络的研究

提出了一种新的混合光突发交换（HOBS）网络，并且使用环网对网络进行了仿真比较研究。仿真结果表明HOBS的丢包率远低于OBS，并且下降的程度决定于拆分比例、缓存的大小以及节点的处理速率等参数。     

基于MPLS的光突发交换技术

介绍了这种网络的结构以及特点,重点讨论了目前国内外在LOBS研究中的最新进展,以及MPLS的扩展(GMPLS)对传统OBS的支持和改进。     

基于标签的光突发交换网络

先进的OBS(optical burst switching)技术和MPLS的强大控制能力结合产生了一种灵活紧凑的IP/DWDM集成模型LOBS.(labeled optical burst switching).它充分发挥了电子处理的高智能和光子交换的大容量优势,是未来数据网络的理想光交换方案.文中从OBS技术的优越性开始,分析了LOBS实现的网络结构和控制协议,探讨了LOBS流量工程和网络生存性.     

基于GMPLS的OBS网络技术

GMPLS(通用多协议标签交换)是MPLS技术向光网络发展的产物。描述GMPLS和MPLS控制平台的区别,介绍引用GMPLS协议作为控制平面的OBS网络。提出的网络结构是在OBS的突发控制包中用通用标签代替源节点和目的节点地址,并使用GMPLS协议栈对路由协议、信令功能以及链路管理协议进行增强和扩展以便更好地支持OBS网络。     

光标签突发包交换技术

光标签突发包交换是一种新出现的光交换技术。它把基于标签转发的速度优势、QoS(服务质量)保证及流量工程与光突发包交换控制机制(更长的转发数据单元、光网络边缘缓存、带外信令控制)结合起来。全面介绍了这种光交换技术，重点描述了其网络结构。另外，还对其所涉及到的关键技术进行了讨论，并结合下一代互联网的技术趋势，对光标签突发包交换的前景进行了评价。     

基于标签的光交换网的QoS实现

基于标签技术的全光交换网是下一代光网络发展的重要方向,而将该技术推向实用则必须实现其对服务质量(QoS)的支持。文章着重描述并讨论了在3种基于标签技术的光交换网中实现QoS的方法和要求。     

基于光GMPLS接入网中区分服务的QoS研究

通过配置区分服务体系实现基于光GMPLS环状网络的QoS测量,涉及到不同的实时多媒体服务.讨论并分析区分服务结构的三种服务级别的特性.仿真结果表明,在网络过载的情况下,快速转发类和保证转发类都有很好的保护作用.加速转发类适合于实时服务,而最大努力类对任何类型的服务}生能都非常低,同时保证转发非常适合于视频流.     

基于GMPLS的OBS关键节点的技术

主要从硬件方面设计了一种满足GLOBS网络要求的OXC节点和边缘节点方案,并通过OPNET仿真验证了它们的功能.     

Hop constraint based admission and fairness control in IP-over-WDM networks

From both user and operator perspectives, fairness is an important aspect in IP-over-WDM networks where Label Switched Paths (LSPs) are dynamically groomed over optical networks. The setup of LSPs with long distances experiences a higher blocking probability due to both lightpath establishment unfairness in the optical layer and link cascading effect in the IP/MPLS layer. A simple LSP connection admission and fairness control mechanism is proposed in this article. This control mechanism is based on hop constraint, in which an LSP is accepted with a pre-assigned probability according to its distance and the hops of its route. Through suppressing connection of short-distance LSPs that overuse bandwidth to facilitate the setup of LSPs with long distances, this proposal achieves fine distance fairness performance with a slight overall blocking probability increment.     

Hop constraint-based capacity fairness control in IP-over-WDM networks

In this article, we consider the capacity fairness problem in IP-over-WDM networks. Since connections with different bandwidth granularities may be established over a shared lightpath, fairness in bandwidth allocation among different users becomes a crucial problem. A simple, yet efficient hop constraint-based admission control scheme is proposed to accommodate more high-bandwidth requests. Through rejecting some of the low-capacity requests that would go through alternative paths with more hops and thus would consume a larger amount of bandwidth, the blocking probability of high-capacity requests reduces notably. Numerical results show that this proposal achieves significant improvement in capacity fairness without raising the overall blocking probability. In addition, it achieves excellent fairness performance at both light and heavy loads by selecting the rejection probability dynamically.

MPLS Recovery Mechanisms for IP-over-WDM Networks

Due to the fast increase of Internet traffic and the enormous bandwidth potential of all-optical transport networks based on wavelength division multiplexing, an IP-over-WDM network scenario is likely to be widespread in future communication networks. At the same time, IP networks are becoming more and more mission-critical. Hence, it is of paramount importance for IP-over-WDM networks to be able to recover quickly from frequently occurring network failures. This paper explains how multi-protocol label switching (both electrical and optical) recovery mechanisms can be important to reach that goal. Moreover, a novel MPLS recovery mechanism called fast topology-driven constrained-based rerouting is presented. Different MPLS recovery mechanisms are compared to each other. Special attention hereby goes to the additional capacity that is required to recover from frequently occurring failures.     

基于正交调制的IP-over-WDM光标记交换网络及其传输性能的研究

详细阐述了基于正交调制格式的IP-over-WDM光标记交换网络的网络体系结构,给出了边缘路由器的结构图与核心路由器的实现方法,数值模拟了IP-over-WDM光网络中基于频移键控/幅移键控正交调制的光标记信号/净荷的传输性能,最后给出了基于正交调制格式的IP-over-WDM光标记传输实验,实验结果表明了所述方案的可行性。     

On the Maximum Protection Problem in IP-over-WDM Networks Using IP LSP Protection

In dynamic IP-over-WDM networks efficient fault-management techniques become more difficult since as demands change with time the optimal logical topology varies as well. Changes in the virtual topology should be done with care because working IP LSPs routed on top of a virtual topology should not be interrupted. Reconfiguration of the virtual topology may also affect precomputed backup IP LSPs to be activated in case of failure meaning that backup IP LSPs would need to be recomputed after any change in the virtual topology. A good sense solution can be the dimensioning of the virtual topology for a worst case traffic scenario, having as goal the minimization of the network cost, for example, and then route dynamic IP LSPs on this virtual topology. The virtual topology would remain unchanged as long as possible, that is, until changes in the virtual topology are considered to bring considerable benefits. Since data services over IP are essentially of a best-effort nature, protection could be provided, using IP LSP protection, only when bandwidth is available in the virtual topology. The computation of backup IP LSPs does not interfere with working IP LSPs meaning that no service interruption will exist. Such a strategy, considered in this paper, allows resources to be used efficiently, since free bandwidth is used for backup purposes, while the normal delivery of traffic is guaranteed in peak traffic situations although having no protection guarantees. Our main objective is to quantify the spare capacity, which can be used for restoration (backup) purposes, over a virtual topology designed and optimized to carry a traffic scenario with no survivability and QoS requirements. We analyse the maximum protection (MP) problem in such IP-over-WDM network environment. Protection is provided to IP LSP requests whenever possible through bandwidth reservation in a backup IP LSP on the virtual topology. Besides the mathematical formalization of the MP problem, an upper bound and heuristic algorithms are proposed and evaluated. The traffic considered includes IP LSPs of different granularities and is the worst case traffic scenario for which the network should be dimensioned.     

Survivable routing in IP-over-WDM networks: An efficient and scalable local search algorithm

In IP-over-WDM networks, a logical IP network is routed on top of a physical optical fiber network. An important challenge here is to make the routing survivable. We call a routing survivable if the connectivity of the logical network is guaranteed in the case of a failure in the physical network. In this paper we describe FastSurv, a local search algorithm for survivable routing. The algorithm works in an iterative manner: after each iteration it learns more about the structure of the logical graph and in the next iteration it uses this information to improve its solution. The algorithm can take link capacity constraints into account and can be extended to deal with multiple simultaneous link failures and node failures. In a large series of tests we compare FastSurv with current state-of-the-art algorithms for this problem. We show that it can provide better solutions in much shorter time, and that it is more scalable with respect to the number of nodes, both in terms of solution quality and run time.     

Design of Logical Topology with Effective Waveband Usage in IP-over-WDM Networks

We deal with the problem of designing the logical topology in IP-over-WDM networks. Many conventional methods for designing the logical topology assume that a constant number of wavelengths will be available on each fiber. But it is not necessary to utilize all wavelengths on each fiber in building an effective logical topology on a WDM network. Instead, several wave-bands may be considered for introduction while deploying additional wave-bands and their corresponding optical amplifiers when additional wavelengths are actually required. In this case, the number of wavelengths available on the respective fibers depends on the number of optical fiber amplifiers deployed on each fiber. In this paper, we propose a heuristic algorithm for the design of a logical topology with as few optical fiber amplifiers as possible. Our results indicate that our algorithm reduces the number of optical fiber amplifiers with a slight increase of average packet delays.     

Influence of GMPLS Recovery Mechanisms on TCP Performance

Optical networks based on wavelength-division-multiplexing (WDM) techniques are very likely to be omnipresent in future telecommunication networks. Those networks are deployed in order to face the steady growth of traffic, which is for a large part Internet related. In the resulting IP-over-WDM scenario, TCP/IP constitutes an important fraction of the traffic transported over these networks. As IP networks are becoming increasingly mission-critical, it is of the utmost importance that these networks (and hence the supporting transport networks) be able to recover quickly from failures such as cable breaks or equipment outages. To that end, several IP-over-WDM network scenarios and corresponding protection and restoration strategies have been devised. It is clear that some trade-offs will have to be made in order to choose an appropriate strategy. In this paper, we investigate the effects of such recovery actions on the behavior of TCP, being the ubiquitous protocol used by today's network users. We examine the influence of different parameters such as the speed of recovery actions, changing length of the routes followed by the client data (TCP flows), changes in available bandwidth, etc. Thereby, we focus on what the TCP end-users care about, i.e., the number of bytes transported end-to-end within a certain time interval.     

Scheduling Algorithms for a Slotted Packet Switch with either Fixed or Variable Length Packets

We address the problem of congestion resolution in optical packet switching (OPS). We consider a fairly generic all-optical packet switch architecture with a feedback optical buffer constituted of fiber delay lines (FDL). Two alternatives of switching granularity are addressed for a switch operating in a slotted transfer mode: switching at the slot level (i.e., fixed length packets of a single slot) or at the burst level (variable length packets that are integer multiples of the slot length). For both cases, we show that in spite of the limited queuing resources, acceptable performance in terms of packet loss can be achieved for reasonable hardware resources with an appropriate design of the time/wavelength scheduling algorithms. Depending on the switching units (slots or bursts), an adapted scheduling algorithm needs to be deployed to exploit the bandwidth and buffer resources most efficiently.     

Protection Schemes for IP-over-WDM Networks: Throughput and Recovery Time Comparison

This article presents a novel protection approach using Generalized Multi-Protocol Label Switching (GMPLS). This strategy provides protection at the Wavelength Division Multiplexing (WDM) layer, meaning that all Internet Protocol Label-Switched Path (IP LSPs) nested inside a lightpath are protected in an aggregated way. It uses resources efficiently since spare capacity of working primary lightpaths can be used for backup purposes whenever necessary. The IP and WDM layers are treated together as a single integrated network from a control plane point of view, so that network state information from both layers can be used. Besides discussing the strategy proposed and the key features of GMPLS that will allow its implementation, we mathematically formulate the maximum throughput problem. Thereafter, we propose and compare heuristic algorithms for IP-over-WDM networks using three protection approaches: WDM lightpath protection, IP LSP protection, and the proposed protection scheme. Their throughputs and recovery times are analyzed and compared. Our results show that, for a representative mesh network, the proposed aggregated protection scheme presents better protection efficiency and good scalability properties when compared with the other two schemes.