基于节点行为特征分析的网络流量分类方法

针对基于加密分组数据的网络流量分类问题,该文提出两种基于行为特征的分析方法。结合流量矩阵和网络结构熵技术,定义了出入度熵指数等参数用于描述节点间的连接行为和数据传输特征,并利用多个周期和时间尺度下的熵指数分析不同流量特征。通过可视图建网方法将流量序列转化为连接网络,利用网络结构相关参数分析流量中蕴含的节点间交互行为的差异。实验表明不同业务流量矩阵的熵指数变化趋势差别较大,而流量序列对应连接网络的聚集系数等存在明显差异。两种方法对于不同业务流量具有较好的分类效果。     

基于贡献矩阵的超网络关键节点评估方法

超网络能够从多维度反映出现实世界事物的多元联系,关键节点有利于分析超网络的拓扑结构和网络功能。针对如何确定超网络中关键节点的问题,通过贡献矩阵提出了两种超网络关键节点的评估方法：基于介数中心性的贡献矩阵方法和基于接近中心性的贡献矩阵方法。两种方法均结合了超图的邻接矩阵、关联矩阵和多个中心性评估指标,综合考虑了节点的全局性影响和局部性影响,并在两个超网络中进行实验验证。结果表明,两种贡献矩阵方法均能准确有效地评估出超网络中的关键节点,且基于接近中心性的贡献矩阵方法改进了基于介数中心性的贡献矩阵方法中存在的缺陷,更加贴近真实世界的事物特性。     

SDN中基于全局拓扑感知的自适应流量均衡算法

针对软件定义网络(Software-Defined Networking,SDN)中控制平面和数据平面之间的控制链路性能受限导致的Packet_In传输瓶颈问题,提出了一种自适应的流量均衡算法,利用SDN网络控制平面拥有全局拓扑和交换机实时状态的特点,运用阈值对流量均衡起止条件进行控制,通过将超载交换机中流量重定向到邻居交换机的一跳转发的自适应方法,解决上行控制链路瓶颈问题.与现有方法相比,减小了33％的上行控制链路负载与50％的Packet-In消息丢包率,且部署开销小.     

野战分组交换网的性能分析

本文提出了一种评价野战分组交换性能的分析方法，其基本原理是根据网络的拓扑结构和每个节点产生的业务量计算出每个节点的总业务量以及每条链路上的业务流量，然后依据排队理论计算野战分组交换网的性能，本文对一种规划的栅格状网络进行了理论分析，并分别针对两种路由准则，采用递归方法推导出了评价网络性能的计算公式。     

BRAS业务测试系统

电信网络中各业务控制点与核心节点间存在两张不同路由的网络,利用其中一张网络为另一张网络铺设测试链路,完成不同BRAS设备远程业务测试的功能。在核心节点处,通过城域网、点对点网络以及维护内网三网整合,将测试链路直接连通维护终端,通过汇聚交换机VLAN的切换,以达到测试链路快速切换的原则。     

应急通信网拓扑模型及其分析

为了解决应急通信网络拓扑特性分析问题,从拓扑模型建立、容量分析、拓扑分析等几方面对应急通信网络模型进行了研究。在模型建立方面,主要考虑了骨干节点、接入节点和终端节点在应急通信网络中的不同之处,并进行分别建模;在容量分析方面,分别给出了任意网络和随机网络的网络容量数量级;在拓扑分析方面,主要从最短路径、节点度、富人俱乐部特性、介数、流中心性、偏心度、紧密活性等拓扑特性入手,通过多次实验进行应急通信网络特性研究。容量分析和拓扑分析的结果表明,提出的应急通信网络模型建立方法具有较高的容量,并符合实际应急通信网络特性。     

SDN中一种基于拓扑变换的功能组合方法

现有软件定义网络(SDN)中的功能组合方法大多都在单节点内进行,均未考虑单节点交换机的功能承载力.为此,首先提出一种基于拓扑变换的功能组合方法,通过拓扑变换将功能组合分散到多个节点中进行处理.其次,将拓扑变换建模成0-1线性规划问题并提出了综合搜索算法进行求解.最后,基于NetFPGA-10G和Ryu控制器完成了所提功能组合方法的原型系统实现.实验结果表明,与现有方法相比,所提出的功能组合方法在降低流处理时延和存储开销的同时提高了组合效率.     

光纤通道拓扑结构冗余方法研究

对于采用光纤通道(FC)互连的航空电子系统,在FC3种基本拓扑结构的基础上,分别给出了FC组合拓扑结构和由多个FC交换机组成的FC交换式网络的通信模型。针对航空电子系统的分布式网络模型,给出了基于任务的可靠性分析方法。根据航空电子系统容错功能和提高可靠性的需要,提出了FC的3种基本冗余结构:双环结构、双交换机结构和交换机仲裁环冗余结构,专门针对FC交换式网络提出了两种冗余结构:基本路径冗余和全网络冗余,专门针对FC组合拓扑结构提出了桥端口冗余结构;通过基于任务的可靠性分析,对各种容错拓扑结构进行了比较。对FC各种冗余拓扑结构的研究对于航空电子系统设计阶段的容错设计和冗余结构设计都将起到一定作用。     

下一代网络8端口交换机体系结构设计

为了满足下一代有线电视网络对驻地用户多终端服务的要求,构建用户驻地8端口交换机,设计交换机内部拓扑结构和交换机内部的带宽配置,根据多种业务的不同需求,确定每个端口特定的带宽。借助OPNET仿真软件进行仿真,结果表明,该8端口交换机很好地满足了技术指标的要求和用户业务的需求,从而保证了下一代有线电视网络在骨干传送网和用户驻地之间更加有效的传输。     

航电FC交换网络可靠性建模与仿真研究

针对典型航电FC交换网络的架构,综合考虑了节点、交换机整体故障和各个端口独立故障对网络可靠性的影响差异以及多种余度数量的分析需求,建立了节点、交换机和链路故障模型、端口-端口网络故障模型以及节点-节点网络故障模型,提供了一种基于矩阵的直观建模思路;给出了基于仿真的故障样本生成方法和网络可靠性计算方法,并结合案例对航电FC交换网络的可靠性进行了定量分析,以上模型和方法可为航电FC交换网络的可靠性设计提供理论数据支持。     

Some principles for designing a wide-area WDM optical network

We explore design principles for next-generation optical wide-area networks, employing wavelength-division multiplexing (WDM) and targeted to nationwide coverage. This optical network exploits wavelength multiplexers and optical switches in routing nodes, so that an arbitrary virtual topology may be embedded on a given physical fiber network. The virtual topology, which is used as a packet-switched network and which consists of a set of all-optical “lightpaths”, is set up to exploit the relative strengths of both optics and electronics-viz. packets of information are carried by the virtual topology “as far as possible” in the optical domain, but packet forwarding from lightpath to lightpath is performed via electronic switching, whenever required. We formulate the virtual topology design problem as an optimization problem with one of two possible objective functions: (1) for a given traffic matrix, minimize the network-wide average packet delay (corresponding to a solution for present traffic demands), or (2) maximize the scale factor by which the traffic matrix can be scaled up (to provide the maximum capacity upgrade for future traffic demands). Since simpler versions of this problem have been shown to be NP-hard, we resort to heuristic approaches. Specifically, we employ an iterative approach which combines “simulated annealing” (to search for a good virtual topology) and “flow deviation” (to optimally route the traffic-and possibly bifurcate its components-on the virtual topology). We do not consider the number of available wavelengths to be a constraint, i.e., we ignore the routing of lightpaths and wavelength assignment for these lightpaths. We illustrate our approaches by employing experimental traffic statistics collected from NSFNET     

Design of wavelength-routed optical networks for packet switchedtraffic

We consider the problem of designing a logical optical network topology for a given physical topology (or fiber layout) and a given traffic demand matrix between the end-users. Traffic between the end-users is carried in a packet-switched form and the objective of our logical topology design is to minimize the maximum congestion on the logical connections in the logical topology. The logical connections are realized by wavelength continuous paths or lightpaths between end-users and they are routed via wavelength-selective routers. Note that a topology with lower maximum link congestion will allow its traffic demand matrix to be scaled up by a larger factor. In the logical topology each node is equipped with a limited number of optical transceivers, hence logical connections cannot be set up between every pair of nodes. In this paper we present an improved lower bound for maximum congestion on any link In the logical topology. The bound is shown to be up to 50% higher than the existing ones. An analytical model for obtaining the maximum and average logical connection loads for a given logical network and traffic demand matrix is also formulated, and it has been confirmed via simulation. Finally, two heuristic algorithms for constructing a logical topology that reduces maximum logical connection congestion are presented     

Comprehensive design methodology for control and data planes in wavelength-routed optical networks

We propose a comprehensive design methodology for control and data planes of wavelength-routed optical networks (WRONs) employing mixed-line-rate (MLR) transmission for cost-effective resource provisioning. The proposed approach attempts to minimize the maximum lightpath capacity demand in Gbps (representing the measure of lightpath congestion) in network for a given traffic matrix by using a mix of a heuristic scheme and linear programming (LP). In the first step of the proposed three-step design, some lightpaths are set up on a set of judiciously selected fiber links (with point-to-point lightpaths between neighboring nodes), on a specific wavelength throughout the network, and an appropriate fraction of the same set of lightpaths is utilized for carrying control information, forming therefore the control plane (CP) of the WRON. The remaining bandwidth of these lightpaths is utilized to carry the data traffic along with all other designed lightpaths of the WRON using appropriate algorithm, forming the overall data plane (DP) of the WRON. In the second step, traffic routing is carried out through LP to minimize lightpath congestion in the network. In the third step, we utilize the results of LP to assign rates to lightpaths, such that the cost (considering only the transceiver cost) of the network is minimized. This design leads to congestion-aware MLR network with due consideration to cost-effectiveness without compromising the network restoration response against link failures. We carry out simulation studies employing possible CPs using both symmetric (CP topology being same as the physical topology) as well as asymmetric (using fewer fiber links than the symmetric case) topology. The results of our simulations indicate that the proposed design of CP with symmetric/asymmetric topology and in-band transmission with sub-lightpath capacity can bring down network congestion and cost with respect to symmetric out-of-band transmission (using fully reserved lightpaths for CP), without any perceptible sacrifice in respect of the network restoration time. Failure can occur either in CP or DP, or in both the planes. We investigate the effect of design of CP with symmetric/asymmetric topology on network restoration time for single- and double-link failures. We further present DP design methodology with hybrid restoration scheme, i.e., combination of dedicated (1:1) path protection and path restoration. We analyze the effect of symmetric CP topology and degree of protection on the congestion of the network. Some lightpaths, that support more traffic, are protected against failures, while the others are left for path restoration in the event of failures. As more lightpaths are protected, the congestion and power consumption of network increase. We provide an analysis of the factors that come into play while altering the degree of protection and observe how the choice for the degree of protection in DP can be arrived at using an appropriate design methodology.     

Light trees: optical multicasting for improved performance inwavelength routed networks

We introduce the concept of a light-tree in a wavelength-routed optical network. A light-tree is a point-to-multipoint generalization of a lightpath. A lightpath is a point-to-point all-optical wavelength channel connecting a transmitter at a source node to a receiver at a destination node. Lightpath communication can significantly reduce the number of hops (or lightpaths) a packet has to traverse; and this reduction can, in turn, significantly improve the network's throughput. We extend the lightpath concept by incorporating an optical multicasting capability at the routing nodes in order to increase the logical connectivity of the network and further decrease its hop distance. We refer to such a point-to-multipoint extension as a light-tree. Light-trees can not only provide improved performance for unicast traffic, but they naturally can better support multicast traffic and broadcast traffic. In this study, we shall concentrate on the application and advantages of light-trees to unicast and broadcast traffic. We formulate the light-tree-based virtual topology design problem as an optimization problem with one of two possible objective functions: for a given traffic matrix, (i) minimize the network-wide average packet hop distance, or (ii) minimize the total number of transceivers in the network. We demonstrate that an optimum light-tree-based virtual topology has clear advantages over an optimum lightpath-based virtual topology with respect to the above two objectives     

Dynamic load balancing in WDM packet networks with and without wavelength constraints

We develop load balancing algorithms for WDM-based packet networks where the average traffic between nodes is dynamically changing. In WDM-based packet networks, routers are connected to each other using wavelengths (lightpaths) to form a logical network topology. The logical topology may be reconfigured by rearranging the lightpaths connecting the routers. Our algorithms reconfigure the logical topology to minimize the maximum link load. In this paper, we develop iterative reconfiguration algorithms for load balancing that track rapid changes in the traffic pattern. At each reconfiguration step, our algorithms make only a small change to the network topology hence minimizing the disruption to the network. We study the performance of our algorithms under several dynamic traffic scenarios and show that our algorithms perform near optimally. We further show that these large reconfiguration gains are achievable in systems with a limited number of wavelengths.     

Design Method of Logical Topologies with Quality of Reliability in WDM Networks

As the bandwidth capacity of WDM networks continues to grow rapidly,traffic loss caused by a failure of network components is becoming unacceptable. To prevent such traffic loss and thus enhance network reliability, a protection method that prepares backup lightpaths for each working path is now being developed. In this paper, we first introduce the concept of QoR (quality of reliability), which is a realization of QoS with respect to the reliability needed in a WDM network. We define QoR in terms of the recovery time from when a failure occurs to when traffic on the affected primary lightpath is switched to the backup lightpath. After that, we propose a heuristic algorithm that can be used to design a logical topology that satisfies the QoR requirement for every node pair. The objective is to minimize the number of wavelengths needed for a fiber in the logical topology to carry the traffic with the required QoR. We compare this algorithm with two existing algorithms and show that it enables more effective use of wavelength resources; with the proposed algorithm, up to 25% fewer wavelengths are needed than with the other algorithms.     

Design of logical topologies for wavelength-routed optical networks

The problem of designing a logical topology over a wavelength-routed all-optical network (AON) physical topology is studied. The physical topology consists of the nodes and fiber links in the network. On an AON physical topology, we can set up lightpaths between pairs of nodes, where a lightpath represents a direct optical connection without any intermediate electronics. The set of lightpaths along with the nodes constitutes the logical topology. For a given network physical topology and traffic pattern, our objective is to design the logical topology and the routing algorithm so as to minimize the network congestion while constraining the average delay seen by a source-destination pair and the amount of processing required at the nodes (degree of the logical topology). Ignoring the delay constraints can result in fairly convoluted logical topologies with very long delays. On the other hand, in all our examples, imposing it results in a minimal increase in congestion. While the number of wavelengths required to imbed the resulting logical topology on the physical all optical topology is also a constraint in general, we find that in many cases of interest this number can be quite small. We formulate the combined logical topology design and routing problem described above as a mixed integer linear programming problem which we then solve for a number of cases of a six-node network. This programming problem is split into two subproblems: logical topology design, and routing. We then compare the performance of several heuristic topology design algorithms against that of randomly generated topologies, as well as lower bounds     

On Hierarchical Traffic Grooming in WDM Networks

The traffic grooming problem is of high practical importance in emerging wide-area wavelength division multiplexing (WDM) optical networks, yet it is intractable for any but trivial network topologies. In this work, we present an effective and efficient hierarchical traffic grooming framework for WDM networks of general topology, with the objective of minimizing the total number of electronic ports. At the first level of hierarchy, we decompose the network into clusters and designate one node in each cluster as the hub for grooming traffic. At the second level, the hubs form another cluster for grooming intercluster traffic. We view each (first- or second-level) cluster as a virtual star, and we present an efficient near-optimal algorithm for determining the logical topology of lightpaths to carry the traffic within each cluster. Routing and wavelength assignment is then performed directly on the underlying physical topology. We demonstrate the effectiveness of our approach by applying it to two networks of realistic size, a 32-node, 53-link topology and a 47-node, 96-link network. Comparisons to lower bounds indicate that hierarchical grooming is efficient in its use of the network resources of interest, namely, electronic ports and wavelengths. In addition to scaling to large network sizes, our hierarchical approach also facilitates the control and management of multigranular networks.      

Resource efficient network design and traffic grooming strategy with guaranteed survivability

In WDM networks, path protection has emerged as a widely accepted technique for providing guaranteed survivability of network traffic. However, it requires allocating resources for backup lightpaths, which remain idle under normal fault-free conditions. In this paper, we introduce a new design strategy for survivable network design, which guarantees survivability of all ongoing connections that requires significantly fewer network resources than protection based techniques. In survivable routing, the goal is to find a Route and Wavelength Assignment (RWA) such that the logical topology remains connected for all single link failures. However, even if the logical topology remains connected after any single link fault, it may not have sufficient capacity to support all the requests for data communication, for all single fault scenarios. To address this deficiency, we have proposed two independent but related problem formulations. To handle our first formulation, we have presented an Integer Linear Program (ILP) that augments the concept of survivable routing by allowing rerouting of sub-wavelength traffic carried on each lightpath and finding an RWA that maximizes the amount of traffic that can be supported by the network in the presence of any single link failure. To handle our second formulation, we have proposed a new design approach that integrates the topology design and the RWA in such a way that the resulting logical topology is able to handle the entire set of traffic requests after any single link failure. For the second problem, we have first presented an ILP formulation for optimally designing a survivable logical topology, and then proposed a heuristic for larger networks. Experimental results demonstrate that this new approach is able to provide guaranteed bandwidth, and is much more efficient in terms of resource utilization, compared to both dedicated and shared path protection schemes.     

SMART: Statistically Multiplexed Adaptive Routing Technique for Ad Hoc Networks

This paper develops a common solution to the problems of discovery, maintenance, and use of multiple routes in ad hoc networks. The performance criterion is the average time taken by a packet to reach its destination through multiple hops. A source node considers each of its neighbors (reachable by direct wireless transmission) as a next-hop for every possible destination. The effect of delay at a next-hop and beyond, until the packet reaches its destination, is approximately modeled as an equivalent M/M/1 queuing system. Available neighbors at every node provide multiple routes. Multiple routes are statistically multiplexed to distribute the load as well as to deal with changes in data rates and network configuration. The potential of each next-hop neighbor of a node in providing a viable route is estimated on-line and the proportions of traffic routed through these multiple neighbors are also updated adaptively.We study this approach and conduct extensive experiments over a network with two extreme cases of simulated traffic patterns, the Poisson, and the self-similar types. Even when the network topology is static, our algorithm responds to bursts in the traffic pattern and reduces buffer losses through the use of alternative, less congested routes. We also present simulation experiments and results to demonstrate the effectiveness of our algorithm in the presence of mobility, using self-similar traffic. Mobility is simulated by means of the random waypoint model in which nodes move with varying speeds. Results show that our simple unified approach handles the problems of mobility as well as network congestion very well.