共查询到20条相似文献,搜索用时 31 毫秒
1.
《Optical Switching and Networking》2008,5(2-3):107-122
This paper presents a study on the Grade-of-Service (GoS) differentiation of static resource allocation in lightpath routed WDM networks, where lightpath requests between node pairs are given. Each request is associated with a service grade. The goal is to maintain certain service levels for the requests of all grades. The service levels are measured in terms of their acceptance ratios. We solve this network optimization problem by adopting a penalty-based framework, in which network design and operation goals can be evaluated based on cost/revenue. We propose a static GoS differentiation model as one minimizing the total rejection and cost penalty, in which the rejection penalty reflects the revenue of accepting a request, and the cost penalty reflects the resource consumption of providing a lightpath to a request. Then, a solution based on the Lagrangian relaxation and subgradient methods is used to solve the proposed optimization problem. Three different application scenarios are presented: static GoS differentiation of requests between the same node pair, static GoS differentiation of requests between different node pairs, and an integration of static GoS differentiation into the network profit objective. The fairness issues and the impact of relative penalty factors are discussed to provide guidelines for network planning. 相似文献
2.
Dynamic establishment of restorable connections in WDM networks is an important problem that has received much study. We propose a dynamic restorable connection establishment scheme that uses p-cycles to protect a connection’s working lightpath. For a given connection request, our scheme first computes a working lightpath and then computes a set of p-cycles to protect the links on the working lightpath so that the connection can survive any single link failure. The key advantage of the proposed scheme is that it enables fast failure recovery while requiring very simple online computation at connection establishment time. Our scheme consists of three components for connection establishment: offline computation of primary cycles, online computation of the working lightpath, and online computation of p-cycles for working lightpath protection. Our scheme also includes a connection teardown procedure that computes and releases all p-cycles that are no longer needed. Simulation study shows that our scheme significantly outperforms an existing p-cycle-based dynamic restorable connection establishment scheme. 相似文献
3.
We consider the problem of establishing dependable connections in WDM networks with dynamic traffic demands. We call a connection with fault-tolerant requirements a dependable connection (D-connection). We consider the single-link failure model in our study and recommend the use of a proactive approach, wherein a D-connection is identified with the establishment of the primary lightpath and a backup lightpath at the time of honouring the connection request. We develop algorithms to select routes and wavelengths to establish D-connections with improved blocking performance. The algorithms use the backup multiplexing technique to efficiently utilize the wavelength channels. To further improve channel utilization, we propose a new multiplexing technique called primary-backup multiplexing. Here, a connection may not have its backup lightpath readily available throughout its existence. We develop algorithms based on this technique to route D-connections with a specified restoration guarantee. We present an efficient and computationally simple heuristic to estimate the average number of connections per link that do not have backup lightpaths readily available upon a link failure. We conduct extensive simulation experiments on different networks to study the performance of the proposed algorithms 相似文献
4.
In this article, we concentrate on the study of control plane and management approaches for translucent WDM networks. A hybrid optical control plane (OCP) is proposed, which needs the extensions of both routing and signaling protocol, to combine the best features of routing-based information updating and signaling-based data collection and path evaluation. Simulations are conducted to compare hybrid OCP with two existing control architectures: signaling-based OCP and routing-based OCP. Numerical results show that hybrid OCP exhibits a lower blocking probability than the other approaches, and also minimizes the stability and scalability problems under various traffic conditions. 相似文献
5.
Yunfeng Peng Weisheng Hu Weiqiang Sun Xiaodong Wang Yaohui Jin 《Photonic Network Communications》2007,13(1):93-102
The popularity of broadband streaming applications requires communication networks to support high-performance multicasting at the optical layer. Suffering from transmission impairments in multi-hop all-optical (transparent) WDM multicasting networks, the signal may be degraded beyond the receivable margin at some multicast destinations. To guarantee the signal quality, we introduce a translucent WDM multicasting network to regenerate the degraded signals at some switching nodes with electronic 3R (reamplification, reshaping and retiming) functionality. The translucent network is built by employing three kinds of multicasting capable switching architectures: (1) all-optical multicasting capable cross connect (oMC-OXC), (2) electronic switch and (3) translucent multicasting capable cross connect (tMC-OXC). Among them both the electronic switch and tMC-OXC are capable of electronic 3R regeneration. Furthermore, we propose a multicast-capable nodes placement algorithm based on regeneration weight, and two multicasting routing algorithms called nearest hub first and nearest on tree hub first to provide signal-quality guaranteed routes for the multicasting requests. The numerical simulation on two typical mesh networks shows that it is sufficient to equip 30% of the nodes or less with signal-regeneration capability to guarantee the signal quality. 相似文献
6.
Translucent wavelength-division multiplexing optical networks use sparse placement of regenerators to overcome physical impairments and wavelength contention introduced by fully transparent networks, and achieve a performance close to fully opaque networks at a much less cost. In previous studies, we addressed the placement of regenerators based on static schemes, allowing for only a limited number of regenerators at fixed locations. This paper furthers those studies by proposing a dynamic resource allocation and dynamic routing scheme to operate translucent networks. This scheme is realized through dynamically sharing regeneration resources, including transmitters, receivers, and electronic interfaces, between regeneration and access functions under a multidomain hierarchical translucent network model. An intradomain routing algorithm, which takes into consideration optical-layer constraints as well as dynamic allocation of regeneration resources, is developed to address the problem of translucent dynamic routing in a single routing domain. Network performance in terms of blocking probability, resource utilization, and running times under different resource allocation and routing schemes is measured through simulation experiments. 相似文献
7.
Virtual concatenation (VCAT) is a Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET) network functionality recently standardized by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T). VCAT provides the flexibility required to efficiently allocate network resources to Ethernet, Fiber Channel (FC), Enterprise System Connection (ESCON), and other important data traffic signals. In this article, we assess the resources' gain provided by VCAT with respect to contiguous concatenation (CCAT) in SDH/SONET mesh transport networks bearing protected scheduled connection demands (SCDs). As explained later, an SCD is a connection demand for which the set-up and tear-down dates are known in advance. We define mathematical models to quantify the add/drop and transmission resources required to instantiate a set of protected SCDs in VCAT- and CCAT-capable networks. Quantification of transmission resources requires a routing and slot assignment (RSA) problem to be solved. We formulate the RSA problem in VCAT- and CCAT-capable networks as two different combinatorial optimization problems: RSA in VCAT-capable networks (RSAv) and RSA in CCAT-capable networks (RSAc), respectively. Protection of the SCDs is considered in the formulations using a shared backup path protection (SBPP) technique. We propose a simulated annealing (SA)-based meta-heuristic algorithm to compute approximate solutions to these problems (i.e., solutions whose cost approximates the cost of the optimal ones). The gain in transmission resources and the cost structure of add/drop resources making VCAT-capable networks more economical are analyzed for different traffic scenarios. 相似文献
8.
9.
为了解决波分复用(WDM)网状网络中的动态流量疏导问题,基于收发器节约辅助图模型,提出了一种资源效率疏导策略.它同时考虑收发器和波长链路两种网络资源的有效利用,根据当前的网络状态动态改变疏导策略,使网络不会由于某一种资源的缺乏而导致阻塞所有流量,避免了另一种资源因富余而造成的浪费,从而两种资源都能得到充分利用.在辅助图模型中,根据两种资源的可用数目比值,对各条边设置不同的权值函数,可轻易地实现该策略.仿真结果证明,不管是收发器资源受限还是波长资源受限,该策略都能取得较好的性能,降低了网络的阻塞率. 相似文献
10.
Analysis of blocking probability for distributed lightpath establishment in WDM optical networks 总被引:1,自引:0,他引:1
In this paper, we analyze the blocking probability of distributed lightpath establishment in wavelength-routed WDM networks by studying the two basic methods: destination-initiated reservation (DIR) and source-initiated reservation (SIR). We discuss three basic types of connection blocking: 1) blocking due to insufficient network capacity; 2) blocking due to outdated information; and 3) blocking due to over-reservation. It is shown that the proposed models are highly accurate for both the DIR and the SIR methods, in both the regular and irregular network topologies, under the whole range of traffic loads. 相似文献
11.
The advances in wavelength division multiplexing (WDM) technology are expected to facilitate bandwidth-intensive multicast
application by establishing a light-tree, which regards the source node as the root, and involves all the destination nodes.
The light-tree is sensitive to failures, e.g., a single fiber cut may disrupt the transmission of information to several destination
nodes. Thus, it is imperative to protect multicast sessions. In this work, we investigate the problem of protecting dynamic
multicast sessions in mesh WDM networks against single link failures. Our objectives are to minimize the usage of network
resources in terms of wavelength links for provisioning survivable multicast session, and to reduce the multicast session
blocking probability. We propose two efficient multicast session protecting algorithms, called Optimal Path Pair based Removing
Residual Links (OPP-RRL) and Source Leaf Path based Avoiding Residual Links (SLP-ARL), which try to reduce the usage of network
resource by removing or avoiding residual links in the topology consisting of light-tree and its backup paths. To evaluate
the proposed algorithms, we apply Integer Linear Programming (ILP) to generate an optimal solution. We also compare the proposed
algorithms with existing algorithms through simulation. Simulation results indicate that the two proposed algorithms have
better performance than other existing algorithms in terms of wavelength links required and network blocking probability.
Furthermore, the solutions generated by the two proposed algorithms are quite close to the solutions generated by ILP in terms
of the number of wavelength links required, when the network size is small. 相似文献
12.
13.
Sun Hyok Chang Hwan Seok Chung Sang Soo Lee Kwangjoon Kim 《Photonic Network Communications》2009,18(3):355-362
We consider a multi-degree optical node configuration, which can provide multiple fiber links to the other nodes in wavelength-division-multiplexing
(WDM) mesh networks. In the node, optical transponders are utilized for the wavelength channels sources and 3R-wavelength
converters. It is shown that blocking originated from both the limited signal impairment threshold (SIT) problem and wavelength
contentions can be resolved by the optical transponders. Moreover, the number of optical transponders per fiber link can be
reduced down to half of the number of wavelength channels without degrading the network performance. 相似文献
14.
Hop-count fairness-aware protocols for improved bandwidth utilization in WDM burst-switched networks
In this paper, we propose and evaluate two schemes for improving bandwidth utilization in optical burst-switched (OBS) networks employing timer-based burst assembly routines. The first scheme adjusts the size of the search space for a free wavelength in optical switches using a balancing formula that promotes throughput and hop-count fairness. The formula achieves controllable increase in the size of the search space either when the size of the burst increases or when the hop count of the traveling burst increases. The second scheme proactively discards bursts at the source network access station using a dropping probability matrix that satisfies certain horizontal and vertical constraints. The matrix assigns smaller dropping probabilities to bursts with larger sizes and longer lightpaths. The results of extensive performance tests to evaluate the two schemes and compare them with previous schemes for improving fairness and throughput are presented and discussed. The results show that the two schemes improve the throughput of optical OBS networks and enhance the hop-count fairness. 相似文献
15.
研究了WDM网状网中双链路失效的保护设计问题,在双链路失效保护时采用"裁剪相继最短路"算法计算工作通路和保护通路,而预留波长时利用波长预留矩阵预留资源,并进行仿真实验.实验结果表明,基于BRM的波长预留方法与已有的两步计算法相比大大减少预留资源. 相似文献
16.
A dynamic routing algorithm with load balancing heuristics for restorable connections in WDM networks 总被引:1,自引:0,他引:1
Dynamic routing of a restorable connection requires a pair of link-disjoint primary and backup lightpaths to be found online when a connection request arrives at the network. We present a distributed dynamic routing algorithm for restorable connections that uses load balancing heuristics in both primary and backup path computations to achieve low demand blocking. The key idea is to assign costs to links so that heavily loaded links will be avoided in the routing of the primary and backup paths and links with a high chance of including a sharable backup channel will be included in the backup path. Simulation results showed that the algorithm performs significantly better than a simple distributed algorithm and achieves comparable performance as a centralized algorithm. 相似文献
17.
To provide a comprehensive network access service to wireless users, a network operator may operate different types of wireless
networks (such as GPRS, Wi-Fi, HSDPA, UMTS, WiMAX and 3GPP LTE) simultaneously to become a heterogeneous wireless network
operator, such as Vodafone and T-Mobile. With convenience of accessing wireless networks, ubiquitous services would stimulate
the bandwidth expenditure in the network backbone. Lots of various demanded traffic from heterogeneous access networks may
converge toward Internet through the common backbone in the operator. Efficiently utilizing the common backbone can offer
a better quality of service to users and maximize the revenues for the operator. To our best knowledge, few studies had ever
been made in such a contemporary wireless network environment in the past. In this study, we propose solutions to efficiently
allocate the bandwidth for user requests and fully utilize the unused bandwidth in the network backbone owned by the heterogeneous
wireless network operator. Our simulation results show that our scheme can increase the utilization of the backbone bandwidth,
shorten the request completion time for users and generate more revenue for the operator. 相似文献
18.
E. Salvadori V.S. Chava A. Zanardi D. Siracusa G. Galimberti A. Tanzi G. Martinelli O. Gerstel 《Optical Switching and Networking》2013,10(1):3-15
In transparent optical networks, physical layer impairments (PLIs) incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the optical feasibility of the lightpaths. In addition, transparent optical networks suffer from inefficient wavelength utilization, as a connection request may be rejected because of non-availability of a common wavelength on all the links along the chosen route. To increase optical reach, resource utilization, and average call acceptance ratio (and hence revenues), network operators are resort to translucent optical networks. In these networks a limited number of regenerators are placed at a selected set of nodes. In this scenario development of an optical control plane which is aware of PLIs, location and number of regenerators, is of paramount importance for on-demand lightpath provisioning. In this paper, we propose a novel approach of constructing a reachability graph of the physical network considering PLIs and regenerators. If there is no transparent path in the physical network, we route the connections with multiple transparent segments on the reachability graph. We propose efficient mechanisms and corresponding GMPLS protocol extensions for impairment and regenerator aware routing and wavelength assignment (IRA-RWA) in translucent optical networks. The simulation results suggest that our proposed approach together with LSP stitching signaling mechanism is feasible to implement and close to deployment. 相似文献
19.
20.
In this paper, we propose a service differentiation method for lightpath establishment in all-optical WDM networks. The proposed
method derives the optimal lightpath establishment policy for each serve class based on a Markov Decision Process (MDP). The
optimal policy considered here is to provide service differentiation for lightpath establishment and to utilize wavelengths
effectively. Here, we focus on two cases for wavelength conversion capability; full-range wavelength conversion and limited-range
wavelength conversion. For full-range wavelength conversion, the number of lightpaths for each class is considered as a state
of MDP. On the other hand, for limited-range wavelength conversion, the service class of lightpath that has been established
with each output wavelength is considered as the state. Based on these states, we derive the optimal policy for lightpath
establishment. In both cases, we evaluate the performance of the proposed method with simulation. In numerical examples, we
show that our proposed method can provide service differentiation and use wavelengths effectively regardless of wavelength
conversion capability. 相似文献