MPLS网络中保证服务质量的多径路由选择策略

本文提出了一种在多协议标签交换(MPLS, Multiple Protocol Label Switching) 网络中保证服务质量 (QoS,Quality-of-Service) 的多径路由选择策略,其核心思想是引入多路径分散业务量机制,在保证用户服务质量要求的同时达到增加网络呼叫接受率和平衡网络负载的目的.文中着重讨论了用户端对端服务质量要求的多路分解和分配问题,在此基础上提出了多径路由的分支路径选择策略,并研究了策略中的关键参数K对该策略性能的影响.数值结果显示出多路径分散业务量在网络负载均衡方面的重要意义,并且表明用户的要求相对网络资源越高使用多径传输的优势越明显.     

VoIP traffic in wireless mesh networks: a MOS‐based routing scheme

Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd.     

Routing Strategies to Minimize Packet Loss in an Optical Packet Switched Network with Recirculating FDL Buffers

The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. We study optical packet switches with recirculating fiber delay line (FDL) buffers. Through simulation, we have assessed the logical performance of a single optical packet router (OPR), focusing on packet loss rate (PLR). By verifying that our scheduling algorithm does not alter the traffic profile characteristics from in- to output, we illustrate how the single node results can be used to assess network-wide performance. We use the capability of assessing end-to-end PLRs to develop network-wide routing algorithms designed to minimize the maximal PLR occurring in the network. In case studies on pan-European networks, we first compare two algorithm variants and thereafter we compare the PLR-based routing algorithm with both load balancing and shortest path routing. While load balancing achieves PLRs that are multiple orders of magnitude lower than shortest path routing, the PLR-based algorithm can reach PLRs up to two orders of magnitude better. The improvement in PLR comes at the price of only a small increase in used bandwidth (a few percent). Subsequently we show that the discussed PLR-based routing algorithm can be easily extended to multiple priorities. By introducing multiple priorities we can keep the loss rates for high priority traffic very low. However, it may lead to an increase of the obtained minimal max-PLR value for low priority traffic. But as we prove this increase to be limited, the cost of introducing multiple priorities is small.     

光网络中基于流量均衡的SRLG分离路由算法

基于共享风险链路组(SRLG,shared risk link group)和流量均衡的概念,研究了光网络抗毁设计中基于流量均衡的SRLO尽量分离路由问题,利用网络流量的实际分布来评价链路和SRLG重要性,提出基于流量均衡的SRIG分离算法TBDR.通过计算机仿真表明,TBDR算法性能优于保护路优先算法,该算法能有效降低网络阻塞率,提高网络资源利用率和网络抗毁能力,达到流量均衡的目标.     

Performance analysis for hierarchical multirate loss networks

The reduced load approximation technique has been extensively applied to flat networks, but the feasibility of applying it to hierarchical network model has seldom been described. Hierarchical routing is essential for large networks such as the Internet inter/intra-domain routing hierarchy and the Private Network to Node Interface (PNNI) standard. Therefore, this paper proposes an efficient and accurate analytical model for evaluating the performance of hierarchical networks with multiple classes of traffic. A performance analysis model with considering multiple classes of traffic, the complexity of analytical and explosion of computation will be extremely increased, and hence, result in inaccurate analytical. The issue of multiple classes of traffic has to be addressed in performance analysis model. In this paper, we first study the reduced load approximation model for loss networks, and then propose a novel performance evaluation model for large networks with multirate hierarchical routing. The hierarchical evaluation model is based on decomposing a hierarchical route into several analytic hierarchical segments. Once the blockings of these hierarchical segments are accurately determined, the blocking of the hierarchical path can be estimated accurately from these segments blocking. Numerical results indicate that the proposed hierarchical reduced load approximation yields quite accurate blocking probabilities as compared to that of simulation results. Furthermore, the accuracy of the proposed hierarchical reduced load approximation heuristic is independent of the blocking or the offered traffic load. Finally, we also draw some remarks on the convergence of the reduced load based approximation analysis model.     

Ant colony optimization based load balancing routing and wavelength assignment for optical satellite networks

An ant colony optimization (ACO) based load balancing routing and wavelength assignment (RWA) algorithm (ALRWA) was put forward for the sake of achieving a fairy load balancing over the entire optical satellite networks. A multi-objective optimization model is established considering the characteristic of global traffic distribution. This not only employs the traffic intensity to modify the light path cost, but also monitors the wavelength utilization of optical inter-satellite links (ISLs). Then an ACO algorithm is utilized to solve this model, leading to finding an optimal light path for every connection request. The optimal light path has the minimum light path cost under satisfying the constraints of wavelength utilization, transmission delay and wavelength-continuity. Simulation results show that ALRWA performs well in blocking probability and realizes efficient load balancing. Meanwhile, the average transmission delay can meet the basic requirement of real-time business transmission.     

A novel domain-by-domain survivable mechanism in multi-domain wavelength-division-multiplexing optical networks

In multi-domain wavelength-division-multiplexing (WDM) optical networks, the inter-domain routing is a challenge since each single-domain cannot view the full network topology. At the same time, survivability is also an important issue in optical networks since the failures of fiber links or network nodes may lead to a lot of traffic being blocked. In this paper, we study the survivability in multi-domain WDM optical networks, and propose a new survivable mechanism called load balanced domain-by-domain routing (LBDDR). In LBDDR, in order to obtain the efficient inter-domain survivable routes, we present the domain-by-domain routing (DDR) method which can find the intra-domain sub-working path and sub-backup path in each single-domain to form the inter-domain working path and backup path for each demand. In order to reduce the blocking probability, we present the load balanced routing method which can encourage the traffic to be uniformly distributed on the links with more free wavelengths. Simulation results show that, compared with conventional mechanism, LBDDR can obtain better performances.     

The maximum mean time to blocking routing in circuit-switchednetworks

The Maximum Mean Time to Blocking (MTB) Routing is a state- and time-dependent adaptive routing scheme. In this scheme, overflowed calls are routed to an alternate path having the longest mean time to blocking. The mean time to blocking of a link is a function of the trunk group size, the traffic rate, and the instantaneous trunk group occupancy and is a particularly suitable measure of the busy status of links in networks with nonuniform trunk group sizes and asymmetric traffic rates. The computation of the mean time to blocking of a path is very demanding and two approximations are proposed. A comparative performance evaluation through a call-by-call computer simulation shows that the MTB routing can give a superior throughput-blocking performance     

Inter-domain optical path provisioning with blocking avoidance by intra-domain immediate reroute-based semi-proactive hierarchical PCE

Optical fiber networks have become the foundations of communication system to provide enormous transmission capacity with less cost. Connection blocking is an inherent attribute and influences optical networks’ performance, especially in multi-domain network scenarios. We analyze the reason and effect of blockings including routing blockings and signaling blockings. We regard the cause of signaling blockings as the information asynchronization in resource reservation process. We define the concept of Information Asynchronization Period to describe the effect of signaling blockings. To reduce signaling blockings in end-to-end optical path provisioning for multi-domain scenarios, we propose a novel network routing and control scheme, named Intra-Domain Immediate Reroute based Semi-Proactive Hierarchical Path Computation Element (IDIRSP H-PCE). The proposed routing and control scheme mainly consists of two parts, Semi-Proactive routing and Intra-Domain Immediate Reroute mechanism. Dynamic network simulations verify our proposed scheme. We compare the network performance with Reactive Backward Recursive PCE-based Computation (BRPC) based PCE, Reactive H-PCE and Proactive H-PCE. Simulation results indicate that IDIRSP H-PCE can provide connection with a very low blocking probability in light load case, which is close to Proactive H-PCE, and obviously better than BRPC based Reactive PCE and Reactive H-PCE. For heavy load case, IDIRSP H-PCE has a remarkably lower blocking probability than other three methods. Moreover, we test our proposed routing and control scheme when facing link faults. Simulation results indicate that IDIRSP H-PCE can greatly improve the traffic access rate and optimize the network performance.     

多层卫星通信网络自适应路由策略

单层卫星网络由于轨道高度和覆盖能力的不同,以至构成通信的单层系统往往不能满足不同业务服务质量的需求。分析了Walkerdelta型星座构建多层卫星通信网络的拓扑结构和ISL性能,提出了在统计分布模型下的多层卫星自适应路由策略,综合考虑了路径时延和ISL链路负载。仿真结果表明了多层网络自适应路由策略能够更加有效地分配网络通信量,网络具有较小的丢包率、网络平均归一化链路负载和特定路径综合路径权重,有利于降低网络平均阻塞概率和特定路径阻塞概率,获得更高的可靠性,较传统的单层非自适应路由更加有效、可靠。     

Comparison of Routing Procedures for Circuit-Switched Traffic in Nonhierarchical Networks

In this paper, we compare the use of different types of routing procedures for circuit-switched traffic in nonhierarchical networks. The main performance criterion used is the end-to-end blocking probability. The results show that if the network traffic is light, alternate routing performs better than nonalternate routing, but if the network traffic is heavy, the situation is reversed. To improve the performance of networks using alternate routing, different types of strategies varying from fixed control to dynamic control are introduced. A comparison based on numerical examples shows the improvement in performance attained by using a dynamic control strategy compared to fixed control. Good control techniques result in nonalternate routing under heavy traffic loads; nonalternate routing is the most viable alternative in nonhierarchical networks under heavy traffic conditions.     

LEO星座中基于不完全信息的路由联盟博弈策略

针对LEO卫星网络在多跳转发数据包时流量分布不均问题,提出了一种基于不完全信息的最优收益路由联盟博弈算法.各节点协同联盟邻居节点,共同确定数据报文当前最优转发路径,从而分配和平衡节点间流量负载.仿真结果表明,与最短路径卫星路由DSP或智能路由TLR相比,本文算法的平均数据传输延迟降低了18.5%,节点流量负载均衡度提高了65.6%.     

Fixed point approximation for multirate multihop loss networks with state-dependent routing

In this paper we consider a class of loss networks that have arbitrary topologies and routes of arbitrary length. Multiple traffic classes are present, each with different bandwidth requirement, and each routed according to a state-dependent routing scheme. In particular, we consider the least loaded routing method generalized to routes of arbitrary number of hops. The connection level performance metric of interest is the end-to-end blocking probability. We are interested in developing fast evaluation methods to provide reasonably accurate estimates of the blocking probability, especially under heavy traffic load. Our algorithms are based on the fixed-point method framework, also known as the reduced load approximation. In addition to what commonly examined by previous work, two more factors contribute to the complexity of the computation in the scenario under consideration in this paper. One is the state-dependent nature of the routing mechanism, the other is the possible overlapping between routes due to the general multihop topology of the network. We present two fast approximation algorithms to evaluate the blocking probability with state-dependent routing by simplifying the route overlapping computation. We discuss the computational complexity of our algorithms as well as sources of approximation error. We then compare the numerical results with that of simulation and show that our algorithms provide fairly accurate blocking probability estimates especially under heavy traffic load.     

Reinforcement learning based routing in wireless mesh networks

This paper addresses the problem of efficient routing in backbone wireless mesh networks (WMNs) where each mesh router is equipped with multiple radio interfaces and a subset of nodes serve as gateways to the Internet. Most routing schemes have been designed to reduce routing costs by optimizing one metric, e.g., hop count and interference ratio. However, when considering these metrics together, the complexity of the routing problem increases drastically. Thus, an efficient and adaptive routing scheme that takes into account several metrics simultaneously and considers traffic congestion around the gateways is needed. In this paper, we propose an adaptive scheme for routing traffic in WMNs, called Reinforcement Learning-based Distributed Routing (RLBDR), that (1) considers the critical areas around the gateways where mesh routers are much more likely to become congested and (2) adaptively learns an optimal routing policy taking into account multiple metrics, such as loss ratio, interference ratio, load at the gateways and end-to end delay. Simulation results show that RLBDR can significantly improve the overall network performance compared to schemes using either Metric of Interference and Channel switching, Best Path to Best Gateway, Expected Transmission count, nearest gateway (i.e., shortest path to gateway) or load at gateways as a metric for path selection.     

A dynamic hop count shifting RWA algorithm for wavelength routed optical networks

In this article, we find that the limiting hop count in a lightpath impacts on the performance of optical networks. Based on this observation, we propose a dynamic hop count shifting (DYHOS) algorithm that limits the hop count of lightpaths dynamically, depending on the traffic load. The proposed algorithm searches an available route, while minimizing the waste of network resources and limiting excessive traffic on the network. Hence, the proposed algorithm increases the network throughput and reduces the blocking probability. Comparing with shortest path routing and adaptive path routing algorithms, we show the performance of the proposed algorithm has the lowest blocking probability influenced by the hop count of lightpaths for a given routing algorithm.

Dynamic routing and wavelength assignment in the presence of wavelength conversion for all-optical networks

Blocking probability has been one of the key performance indexes in the design of wavelength-routed all-optical WDM networks. Existing research has demonstrated that an effective Routing and Wavelength Assignment (RWA) algorithm and wavelength conversion are two primary vehicles for improving the blocking performance. However, these two issues have largely been investigated separately; in particular the existing RWA algorithms have seldom considered the presence of wavelength conversion. In this paper, we firstly demonstrate that the existing dynamic RWA algorithms do not work well in the presence of wavelength conversion as they usually only take into account the current traffic, and do not explicitly consider the route lengths. We then propose a weighted least-congestion routing and first-fit wavelength assignment (WLCR-FF) algorithm that considers both the current traffic load and the route lengths jointly. We further introduce an analytical model that can evaluate the blocking performance for WLCR algorithm. We carry out extensive numerical studies over typical topologies including ring, mesh-torus, and the 14-node NSFNET; and compare the performance of WLCR-FF with a wide variety of existing routing algorithms including static routing, fixed-alternate routing and least-loaded routing. The results conclusively demonstrate that the proposed WLCR-FF algorithm can achieve much better blocking performance in the presence of sparse or/and full wavelength conversion.     

一种支持业务均衡的OBS自适应多可达性路由机制

针对光突发交换(OBS)网络中如何高效解决频繁发生的光突发竞争问题,提出了一种支持业务均衡的OBS自适应多可达性路由机制(AMR-LB).首先根据发送端发送业务量大小和当前网络业务承载状态,按需地为光突发确定多可达性路由;然后在非线性规划下,自适应地调整各条路由的业务承载比例.通过性能仿真,并与自适应替代路由算法(AA...     

Distributed potential field based routing and autonomous load balancing for wireless mesh networks

Congested hot spots and node failures severely degrade the performance of wireless mesh networks. However, conventional routing schemes are inefficient in mitigation of the problems. Considering analogy to physics, we propose a novel distributed potential-field-based routing scheme for anycast wireless mesh networks, which is robust to sudden traffic and network perturbations, effectively balancing load among multiple gateways and mesh nodes with little control overhead. Simulation results exhibit autonomous load balancing and failure-tolerant performance in wireless mesh networking.     

Domain load balancing routing for multi-gateway wireless mesh networks

As Wireless Mesh Networks (WMNs) are typically used for Internet access, most traffic is routed through the gateways which connect WMN to the wired network. As a result, the gateways tend to get congested and balancing of the traffic load of gateways is critical. In this paper, we consider applications that require continuous provision of a certain bandwidth to a server located at the wired network. If a path that satisfies the bandwidth request cannot be found, the request will be rejected, so that load imbalance will result underutilization of the network capacity. We present a novel load balancing routing algorithm for maximizing the network utilization (i.e., accommodating service requests as many as possible) for multi-gateway WMNs. In the proposed scheme, a WMN is divided into domains. Each domain is served by one gateway, so that all traffic of a domain is served by the corresponding gateway. Our scheme determines routing to balance the traffic load among domains, and then performs load balancing routing within each domain. Simulation results show that in square grid topologies, our intra-domain routing achieves near optimal performance with about 70% less overhead than the existing schemes. Our inter-domain load balancing scheme outperforms the existing heuristics by up to 25% while achieving about 80% performance of the optimal solution.     

An Ant-Based Approach for Dynamic RWA in Optical WDM Networks

In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection. The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables, so that the route for a connection request can be determined promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability. The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm very attractive for both the optical circuit switching networks and future optical burst switching networks