Routing of multicast audio/video streams in reconfigurable WDM optical networks

Due to its low attenuation, fiber has become the medium of choice for point-to-point links. Using Wavelength-Division Multiplexing (WDM), many independent channels can be created in the same fiber. A network node equipped with a tunable optical transmitter can select any of these channels for sending data. An optical interconnection combines the signal from the various transmitters in the network, and makes it available to the optical receivers, which may also be tunable. By properly tuning transmitters and/or receivers, point-to-point links can be dynamically created and destroyed. Therefore, in a WDM network, the routing algorithm has an additional degree of freedom compared to traditional networks: it can modify the netowrk topology to create the routes. In this paper, we consider the problem of routing multicast audio/video streams in WDM networks and propose heuristic algorithms to solve it. The performance of these heuristics is evaluated in a number of scenarios, with a realistic traffic model, and from the evaluation we derive guidelines for usage of the proposed algorithms.This work was supported in part by NASA under grant NAG2-842, by the National Science Foundation under grant NCR-9016032 and by Pacific Bell. Ciro Noronha was supported by a graduate scholarship from FAPESP from Sept/89 to Aug/93 under grant 89/1658.     

受限网络中基于转发历史异步路由及中继数量研究

由于节点的移动性、稀疏链路和节点的不可靠,受限网络节点之间在大部分时间处于断开状态,现有的同步路由方法不能适用这种实际情况,所以必须从异步角度来考虑这类网络环境下的路由问题.文章完全从异步的角度思考无线自组织网中的路由问题,利用分组转发的历史信息智能做出路由决策,并研究中继节点数量对性能的影响,以减少由于复制大量分组而产生的网络流量.文章详细介绍了作者提出的方法,并通过仿真实验和一些相关算法进行比较,分析算法性能.     

基于关键网络状态的域内路由可用性研究

业界通常采用路由保护方案来提高域内路由可用性.然而已有的路由保护方案存在下面两个方面的问题:a)没有考虑网络中链路的失效概率,同等对待网络中所有的链路,事实上在互联网中,不同链路的失效概率是不同的,因此应该在路由保护方案中考虑链路的失效概率;b)将保护链路的数量作为设计目标,事实上方面某些链路出错的概率非常低,保护这些链路反而会增加开销,而另一方面某些链路出错的概率非常高,需要重点保护这些链路.因此应该将路由可用性作为路由保护方案的设计目标.针对上述两个问题,提出了一种基于关键网络状态的域内路由保护方案(RPBCNS),该算法首先通过链路失效概率计算出所有的关键网络状态,然后在每种关键网络状态下计算节点对之间相应的路径,保证节点对之间路径的多样性,从而使得尽可能多的节点对满足路由可用性需求.仿真实验将RPBCNS算法与主流算法ECMP、DC、path splicing分别在三个真实网络中进行对比,在网络可用性和节点对可用性满足率上RPBCNS的性能明显优于其他三种算法.仿真结果表明,RP-BCNS不仅具有较高的网络可用性,并且能够使得尽可能多的节点对满足路由可用性目标,更符合实时应用的实际需求.     

具有不确定性路径概率的闭排队网络鲁棒控制策略

The paper is concerned with the robust control problems for exponential controlled closed queuing networks (CCQNs) under uncertain routing probabilities. As the rows of some parameter matrices such as infinitesimal generators may be dependent, we first transform the objective vector under discounted-cost criteria into a weighed-average cost. Through the solution to Poisson equation, i.e., Markov performance potentials, we then unify both discounted-cost and average-cost problems to study, and derive the gradient formula of the new objective function with respect to the routing probabilities. Some solution techniques are related for searching the optimal robust control policy. Finally, a numerical example is presented and analyzed.     

Robust Control Policy for Closed Queuing Networks with Uncertain Routing Probabilities

The paper is concerned with the robust control problems for exponential controlled closed queuing networks (CCQNs) under uncertain routing probabilities.As the rows of some parameter matrices such as infinitesimal generators may be dependent,we first transform the objective vector under discounted-cost criteria into a weighed-average cost.Through the solution to Poisson equation, i.e.,Markov performance potentials,we then unify both discounted-cost and average-cost problems to study,and derive the gradient formula of the new objective function with respect to the routing probabilities.Some solution techniques are related for searching the optimal robust control policy. Finally,a numerical example is presented and analyzed.     

SWER: small world-based efficient routing for wireless sensor networks with mobile sinks

The interest in small-world network has highlighted the applicability of both the graph theory and the scaling theory to the analysis of network systems. In this paper, we introduce a new routing protocol, small world-based efficient routing (SWER), dedicated to supporting sink mobility and small transfers. The method is based on the concept of the small worlds where the addition of a small number of long-range links in highly clustered networks results in significant reduction in the average path length. Based on the characteristic of sensor networks, a cluster-based small world network is presented, and an analytical model is developed to analyze the expected path length. SWER adopts a simple and effective routing strategy to forward data to the mobile sink in a small transfer scene and avoid expensive mechanisms to construct a high quality route. We also study the routing scheme and analyze the expected path length in the case where every node is aware of the existence of p long-range links. In addition, we develop a hierarchical mechanism in which the mobile sink only transmits its location information to the cluster heads when it enters a new cluster. Thus we also avoid expensive cost to flood the location of the mobile sink to the whole network.     

Management,control, and design of integrated networks with real-time dynamic routing

Integrated real-time dynamic routing (IRR) networks provide dynamic routing features for multiple classes-of-service on an integrated transport network. In this paper it is shown that IRR networks allow reduced network management costs since with real-time dynamic routing a number of network operations are simplified or eliminated. These simplifications include eliminating the storage of voluminous routing tables in the network switches, eliminating the calculation of routing tables in network design, simplifying the routing administration operations which require downloading new routing information to the network, and eliminating the automatic rerouting function in on-line traffic management. A new bandwidth allocation technique is described here which is based on the optimal solution of a network bandwidth allocation model for IRR networks. The model achieves significant improvement in both the average network blocking and node pair blocking distribution when the network is in a congested state such as under peak-day loads. In a paper to appear in the next Journal issue we further describe a new algorithm for the transport design of IRR networks which achieves near-optimal capacity engineering. These optimization techniques attain significant capital cost reductions and network performance improvements by properly modeling the more efficient operation of IRR networks.     

SWER:small world-based efficient routing for wireless sensor networks with mobile sinks

The interest in small-world network has highlighted the applicability of both the graph theory and the scaling theory to the analysis of network systems. In this paper, we introduce a new routing protocol, small world-based efficient routing (SWER), dedicated to supporting sink mobility and small transfers. The method is based on the concept of the small worlds where the addition of a small number of long-range links in highly clustered networks results in significant reduction in the average path length. Based on the characteristic of sensor networks, a cluster-based small world network is presented, and an analytical model is developed to analyze the expected path length. SWER adopts a simple and effective routing strategy to forward data to the mobile sink in a small transfer scene and avoid expensive mechanisms to construct a high quality route. We also study the routing scheme and analyze the expected path length in the case where every node is aware of the existence of p longrange links. In addition, we develop a hierarchical mechanism in which the mobile sink only transmits its location information to the cluster heads when it enters a new cluster. Thus we also avoid expensive cost to flood the location of the mobile sink to the whole network.     

Route Maintenance in IEEE 802.11 wireless mesh networks

In this paper, we propose a novel Route Maintenance scheme for IEEE 802.11 wireless mesh networks. Despite lack of mobility and energy constraints, reactive routing protocols such as AODV and DSR suffer from frequent route breakages in 802.11 based infrastructure wireless mesh networks. In these networks, if any intermediate node fails to successfully transmit a packet to the next hop node after a certain number of retransmissions, the link layer reports a transmission problem to the network layer. Reactive routing protocols systematically consider this as a link breakage (and therefore a route breakage). Transmission failures can be caused by a number of factors e.g. interference or noise and can be transient in nature. Frequent route breakages result in significant performance degradation. The proposed mechanism considers multiple factors to differentiate between links with transient transmission problems from those links which have permanent transmission problems and takes a coherent decision on link breakage. The proposed mechanism is implemented in AODV for single-radio single-channel mesh network and an extension is incorporated in multi-radio multi-channel scenarios. Simulation results show substantial performance improvement compared to classical AODV and local route repair schemes.     

Multi-Service Dynamic QoS Routing Schemes with Call Admission Control: A Comparative Study

In this paper we consider wide-area backbone networks where multiple connection-oriented guaranteed services with differing bandwidth/flow requirements are offered. Specifically, we consider the case where each service requires a quality-of-service (QoS) peak rate bandwidth/flow allocation (different rate for different services) for the duration of the connection in a loss network environment. We present several dynamic routing schemes in such multi-service settings along with an admission control policy. The routing schemes cover issues such as crankback, periodicity of computation of routing, what type of information is to be used in routing decision, and whether to use centralized or decentralized computation. We present results for various measures, i.e., in addition to well-known call blocking performance, we also address and quantify measures such as signaling loads impact due to alternate routing, crankback impact, and revenue impact, and provide a comparative evaluation of various dynamic routing schemes in multi-service settings.     

Caching and optimized request routing in cloud-based content delivery systems

Geographically distributed cloud platforms enable an attractive approach to large-scale content delivery. Storage at various sites can be dynamically acquired from (and released back to) the cloud provider so as to support content caching, according to the current demands for the content from the different geographic regions. When storage is sufficiently expensive that not all content should be cached at all sites, two issues must be addressed: how should requests for content be routed to the cloud provider sites, and what policy should be used for caching content using the elastic storage resources obtained from the cloud provider. Existing approaches are typically designed for non-elastic storage and little is known about the optimal policies when minimizing the delivery costs for distributed elastic storage.In this paper, we propose an approach in which elastic storage resources are exploited using a simple dynamic caching policy, while request routing is updated periodically according to the solution of an optimization model. Use of pull-based dynamic caching, rather than push-based placement, provides robustness to unpredicted changes in request rates. We show that this robustness is provided at low cost. Even with fixed request rates, use of the dynamic caching policy typically yields content delivery cost within 10% of that with the optimal static placement. We compare request routing according to our optimization model to simpler baseline routing policies, and find that the baseline policies can yield greatly increased delivery cost relative to optimized routing. Finally, we present a lower-cost approximate solution algorithm for our routing optimization problem that yields content delivery cost within 2.5% of the optimal solution.     

Trust-based minimum cost opportunistic routing for Ad hoc networks

Recently, opportunistic routing has received much attention as a new design direction. It can exploit the wireless broadcast and more highly reliable opportunistic forwarding, so as to substantially increase the throughput of network. Due to dynamic topology, distributed collaboration, limited bandwidth and computing ability, the absence of enough physical protection in Ad hoc networks, opportunistic routing is vulnerable to attacks by malicious nodes. In order to alleviate the malicious behaviors, we incorporate the concept of trust to Ad hoc networks, build a simple trust model to evaluate neighbors’ forwarding behavior and apply this model to opportunistic routing for Ad hoc networks. A new trusted opportunistic forwarding model is proposed by choosing the trusted and highest priority candidate forwarder, then a trusted minimum cost routing algorithm (MCOR) is formally formulated, the correctness and effectiveness of this algorithm from theoretical analysis are also approved. Finally, MCOR algorithm is verified by simulation using nsclick software and compared its performance with the classic protocols: ExOR, TAODV and Watchdog-DSR. The simulation results show that MCOR scheme can detect and mitigate node misbehaviors. Furthermore, MCOR scheme outperforms the other protocols in terms of: throughput, delay, Expected ETX, security-gains and cost of routing.     

Inter-domain policy violations in multi-hop overlay routes: Analysis and mitigation

The Internet is a complex structure arising from the interconnection of numerous autonomous systems (AS), each exercising its own administrative policies to reflect the commercial agreements behind the interconnection. However, routing in service overlay networks is quite capable of violating these policies to its advantage. To prevent these violations, we see an impending drive in the current Internet to detect and filter overlay traffic. In this paper, we first present results from a case study overlay network, constructed on top of PlanetLab, that helps us gain insights into the frequency and characteristics of the different inter-domain policy violations. Further, we investigate the impact of two types of overlay traffic filtering that aim to prevent these routing policy violations: blind filtering and policy-aware filtering. We show that such filtering can be detrimental to the performance of overlay routing. We next consider two approaches that allow the overlay network to realize the full advantage of overlay routing in this context. In the first approach, overlay nodes are added so that good overlay paths do not represent inter-domain policy violations. In the second approach, the overlay acquires permits from certain ASes that allow certain policy violations to occur. We develop a single cost-sharing framework that allows the incorporation of both approaches into a single strategy. We formulate and solve an optimization problem that aims to determine how the overlay network should allocate a given budget between paying for additional overlay nodes and paying for permits (transit and exit) to ASes. We illustrate the use of this approach on our case study overlay network and evaluate its performance under varying network characteristics.     

基于OPNET的卫星网络路由仿真

具有星际链路的卫星网络将在今后发挥巨大的作用,而混合星座具有比单层星座更加优异的性能,双层星座GEO/LEO能够在物理上实现网络管理和业务的分离,便于对全网络的管理和集中式路由的实现。依据卫星网络运动的规律性,采用虚拟拓扑路由策略,在OPNET中对GEO/LEO双层星座进行了集中式路由的仿真;在定义链路权值时,除了传统上考虑的传播时延、排队时延外,还加上了地理因素的影响,使之更符合卫星网络的实际情况。     

Sensitivity analysis of an optimal routing policy in an ad hoc wireless network

We examine the sensitivity of optimal routing policies in ad hoc wireless networks with respect to estimation errors in channel quality. We consider an ad hoc wireless network where the wireless links from each node to its neighbors are modeled by a probability distribution describing the local broadcast nature of wireless transmissions. These probability distributions are estimated in real-time. We investigate the impact of estimation errors on the performance of a set of proposed routing policies.     

Transport network design of integrated networks with real-time dynamic routing

Integrated real-time dynamic routing (IRR) networks provide dynamic routing features for multiple classes-of-service on an integrated transport network. In a previous Journal paper it is shown that IRR networks allow reduced network management costs since with real-time dynamic routing a number of network operations are simplified or eliminated, leading to savings in operations costs and expenses. In this paper a new algorithm is described for the transport design of IRR networks which achieves near-optimal capacity engineering. In particular, a Karmarkar Algorithm optimal solution to the linear programming flow model achieves approximately a 5 to 8 percentage point reduction in network design cost in comparison to the designs of pre-planned dynamic networks solved with heuristic design techniques. The optimization techniques described in this and the previous Journal paper attain significant capital cost reductions and network performance improvements by properly modeling the more efficient operation of IRR networks.     

基于遗传算法的防止无线移动网络路由攻击策略

在无线移动网络中,恶意节点可以通过发送虚假信息和假路由信息、广播假链接等中断路由操作对网络进行攻击。本文在分析了几种常见路由攻击的基础上,提出了一种基于遗传算法的路由优化策略。实验数据表明,这种优化策略可以较好地预防路由攻击,提高网络的整体性能。     

Better Alternatives to OSPF Routing

The current standard for intra-domain network routing, Open Shortest Path First (OSPF), suffers from a number of problems-the tunable parameters (the weights) are hard to optimize, the chosen paths are not robust under changes in traffic or network state, and some network links are over-used at the expense of others. We present prototypical scenarios that illustrate these problems. Then we propose several variants of a protocol to eliminate or alleviate them and demonstrate the improvements in performance under those scenarios. We also prove that these protocols never perform significantly worse than OSPF and show that for at least a limited class of network topologies, it is possible to find efficiently the optimal weight settings. Some of the problems with OSPF are well known; indeed, there are several routing protocols that perform better than OSPF in routing quality (i.e., in terms of congestion, delay, etc.). OSPF’s popularity persists in part because of its efficiency with respect to several resource bounds. In contrast, many competing protocols that provide routing superior to OSPF are computationally prohibitive. Motivated by this consideration, we designed our protocols not only to achieve better routing quality than OSPF, but also to use resources in amount comparable with OSPF with respect to offline broadcast communication, size of and time to compute routing tables, packet delivery latency, and packet header structure and size.     

多QoS约束的层次多播路由算法框架

为了解决网络路由的扩展性问题。大型网络通常被划分成若干个不同的域。拓扑聚集是对这些域的拓扑状态信息进行汇总的过程。在拓扑聚集的基础上,QoS层次多播路由算法用来构造满足QoS要求的域闻多播树。现有的QoS层次多播路由算法在其拓扑聚集和路径计算的过程中都只考虑了存在两个QoS特征值的情况。本文提出了一种具有多QoS约束的层次多播路由算法框架HMRMQ（Hierarchical Multicast Routing with Multiple QoS constraints）,此算法框架不仅为基于多QoS特征值的拓扑状态聚集和状态信息表示提供了新的方法,而且提出了一种适应于多QoS约束的层次多播路由新算法。我们提出的状态信息表示法和拓扑聚集算法都具有很好的扩展性,分布式的路由算法也便于某些安全性策略的实施。理论分析和实验结果不仅证明了HMRMQ的正确性和有效性,同时也表明了HMRMQ在网络路由的扩展性、路由成功率、网络代价以及报文负载等方面都具有良好的性能。     

Bandwidth-aware energy efficient flow scheduling with SDN in data center networks

Nowadays the energy consumption has become one of the most urgent issues for Data center networks. For general network devices, the power is constant and independent from the actual transfer rate. Therefore the network devices are energy efficient when they are in full workload. The flow scheduling methods based on the exclusive routing can reduce the network energy consumption, as the exclusive routing paths can fully utilize all their links. However, these methods will no longer guarantee the energy efficiency of switches, as they handle flows in priority order by greedily choosing the path of available links instantaneously. In a previous work we proposed an extreme case of flow scheduling based on both link and switch utilization. Herein we consider general scenarios in data center networks and propose a novel energy efficient flow scheduling and routing algorithm in SDN. This method minimizes the overall energy for data center traffic in time dimension, and increases the utilization of switches and meet the flow requirements such as deadline. We did a series of simulation studies in the INET framework of OMNet++. The experiment results show that our algorithm can reduce the overall energy with respect to the traffic volume and reduce the flow completion time on average.