Delay constraint multipath routing for wireless multimedia ad hoc networks

According to the disadvantages of real time and continuity for multimedia services in ad hoc networks, a delay constraint multipath routing protocol for wireless multimedia ad hoc networks, which can satisfy quality of service (QoS) requirement (QoS multipath optimized link state routing [MOLSR]), is proposed. The protocol firstly detects and analyzes the link delay among the nodes and collects the delay information as the routing metric by HELLO message and topology control message. Then, through using the improved multipath Dijkstra algorithm for path selection, the protocol can gain the minimum delay path from the source node to the other nodes. Finally, when the route is launched, several node‐disjoint or link‐disjoint multipaths will be built through the route computation. The simulation and test results show that QoS‐MOLSR is suitable for large and dense networks with heavy traffic. It can improve the real time and reliability for multimedia transmission in wireless multimedia ad hoc networks. The average end‐to‐end delay of QoS‐MOLSR is four times less than the optimized link state routing. Copyright © 2014 John Wiley & Sons, Ltd.     

Study of LSP arrangement schemes in label switch networks

Label switch paths (LSP) are regarded as the routing components of an end‐to‐end connection in label switching network from the traffic engineering point of view. Thus, an end‐to‐end connection may travel more than one LSP. The QoS of this end‐to‐end connection relies on the performance of each LSP it travels. Therefore, to carefully arrange LSP is an essential step towards QoS networks. Generally speaking, the capacity of a specific link is not allocated for high‐priority LSP because it will cause inflexibility in the scheduling process. In this paper, the best‐fit shortest path (BSP) assignment and the worst shortest path (WSP) assignment schemes are proposed for the arrangement of label switch paths. In order to provide flexibility in packet scheduling, we propose that the BSP scheme to be applied for allocation of low‐priority LSP and the WSP scheme is used for the arrangement of LSP with high priority. Based on these two schemes, we extend them with elastic bandwidth allocation to prevent the bandwidth of the link from being occupied by the higher priority LSP. The experimental results indicate that, compared to the BSP‐only scheme, the proposed hybrid scheme demonstrates a more efficient way of arranging prioritized LSP. Moreover, the proposed elastic constrained bandwidth allocation scheme also illustrates a rather good performance in smoothing the link utilization of high‐priority LSP. Copyright © 2005 John Wiley & Sons, Ltd.     

Performance Analysis of an Adaptive Link Status Update Scheme Based on Link‐Usage Statistics for QoS Routing

In the global Internet, a constraint‐based routing algorithm performs the function of selecting a routing path while satisfying some given constraints rather than selecting the shortest path based on physical topology. It is necessary for constraint‐based routing to disseminate and update link state information. The triggering policy of link state updates significantly affects the volume of update traffic and the quality of services (QoS). In this letter, we propose an adaptive triggering policy based on link‐usage statistics in order to reduce the volume of link state update traffic without deterioration of QoS. Also, we evaluate the performance of the proposed policy via simulations.     

A delay‐centric parallel multi‐path routing protocol for cognitive radio ad hoc networks

In this paper, we develop a delay‐centric parallel multi‐path routing protocol for multi‐hop cognitive radio ad hoc networks. First, we analyze the end‐to‐end delay of multi‐path routing based on queueing theory and present a new dynamic traffic assignment scheme for multi‐path routing with the objective of minimizing end‐to‐end delay, considering both spectrum availability and link data rate. The problem is formulated as a convex problem and solved by a gradient‐based search method to obtain optimal traffic assignments. Furthermore, a heuristic decentralized traffic assignment scheme for multi‐path routing is presented. Then, based on the delay analysis and the 3D conflict graph that captures spectrum opportunity and interference among paths, we present a route discovery and selection scheme. Via extensive NS2‐based simulation, we show that the proposed protocol outperforms the benchmark protocols significantly and achieves the shortest end‐to‐end delay. Copyright © 2015 John Wiley & Sons, Ltd.     

Proactive multipath routing with a predictive mechanism in software‐defined networks

With the growth of network traffic volume, link congestion cannot be avoided efficiently with conventional routing protocols. By utilizing the single shortest‐path routing algorithm from link state advertisement information, standard routing protocols lack of global awareness and are difficult to be modified in a traditional network environment. Recently, software‐defined network (SDN) provided innovative architecture for researchers to program their own network protocols. With SDN, we can divert heavy traffic to multiple paths in order to resolve link congestion. Furthermore, certain network traffics come in periodic fashion such as peak hours at working days so that we can leverage forecasting for resource management to improve its performance. In this paper, we propose a proactive multipath routing with a predictive mechanism (PMRP) to achieve high‐performance congestion resolution. PMRP has two main concepts: (a) a proactive mechanism where PMRP deploys M/M/1 queue and traffic statistics to simulate weighted delay for possible combinations of multipaths placement of all subnet pairs, and leverage genetic algorithm for accelerating selection of optimized solution, and (b) a predictive mechanism whereby PMRP uses exponential smoothing for demand traffic volumes and variance predictions. Experimental results show a 49% reduction in average delay as compared with single shortest routing, and a 16% reduction in average delay compared with utilization & topology‐aware multipath routing (UTAMP). With the predictive mechanism, PMRP can decrease an additional 20% average delay. Furthermore, PMRP reduces 93% of flow table usage on average as compared with UTAMP.     

Minimum delay algorithm based on time aggregated graph in DTN network

The DTN network has the characteristics of dynamic topology change,thus the routing algorithm of static network can not solve the routing problem of time-varying network,and can not support fast transmission of given tasks.The existing time-variant routing algorithm CGR (contact graph routing) uses the earliest contact to obtain the shortest path,but because of the influence of the order of the connectivity period,the CGR algorithm has low link utilization.To solve this problem,the method of finding the shortest path was proposed.Besides,in order to characterize the relation between the different connect periods of the same link,the time series of node cache was added to the time aggregated graph.Based on this,the end-to-end multi-path shortest delay routing algorithm for the known task requirements was proposed.Finally,the feasibility of the algorithm was proved by an example.     

A Bandwidth Guaranteed Integrated Routing Algorithm in IP over WDM Optical Networks

In this paper, we have developed an integrated online algorithm for dynamic routing of bandwidth guaranteed label switched paths (LSPs) in IP-over-WDM optical networks. Traditionally, routing at an upper layer (e.g., IP layer) is independent of wavelength routing at the optical layer. Wavelength routing at the optical layer sets up a quasi-static logical topology which is then used at the IP layer for IP routing. The coarse-grain wavelength channels and the pre-determined virtual topologies with respect to some a priori assumed traffic distribution are barriers to efficient resource use and inflexible to changing traffic. We take into account the combined knowledge of resource and topology information at both IP and optical layers. With this added knowledge, an integrated routing approach may extract better network efficiencies, be more robust to changing traffic patterns at the IP layer than schemes that either use dynamic routing information at the IP layer or use a static wavelength topology only. LSP set-up requests are represented in terms of a pair of ingress and egress routers as well as its bandwidth requirement, and arrive one-by-one. There is no a priori knowledge regarding the arrivals and characteristics of future LSP set-up requests. Our proposed algorithm considers not only the importance of critical links, but also their relative importance to routing potential future LSP set-up requests by characterizing their normalized bandwidth contribution to routing future LSP requests with bandwidth requirements. Moreover, link residual bandwidth information that captures the link's capability of routing future LSPs is also incorporated into route calculation. Extensive simulation was conducted to study the performance of our proposed algorithm and to compare it with some existing ones, such as the integrated minimum hop routing algorithm and the maximum open capacity routing algorithm. Simulation results show that our proposed algorithm performs better than both routing algorithms in terms of the number of LSP set-up requests rejected and the total available bandwidth between router pairs.     

流量工程中静态路由算法的研究

该文提出了一种应用于流量工程环境中的静态路由算法。考虑当前的网络资源情况,分优先级别在网络中计算并配置标记交换路径(Label Switched Path,LSP),当某一优先级有多条 LSP需要并行配置时,利用遗传算法搜索最优或较优的配置方案,使得网络的链路带宽使用率低于管理员定义的某个限定值,达到合理分布资源的目的。此外,提出了一种改进的 Dijkstra 算法计算 LSP的最短路径。     

Load balance in hierarchical routing network

In this article, the problem of load balance in hierarchical routing network is studied. Since conventional shortest path first (SPF) algorithm over aggregated topology in hierarchical routing network may result in worse routing performance, a traffic sharing path selection algorithm and a variable weight scheme are put forward for hierarchical routing network, which can equilibrate the utilities of link resources and reduce the blocking probability of connections with the improvement on survivability. Simulations are conducted to evaluate proposed variable weight and traffics balance (VWTB) algorithm, which combines traffic sharing and variable weight. From the simulation results, it can be found that the proposed VWTB algorithm can balance the traffics and equilibrate the utilities of link resources significantly.     

低轨卫星网络的航点分段路由及业务性能分析

提出一种基于卫星航点的分段路由（waypoint-segmentrouting,WSR）算法，WSR算法以可预测的卫星网络拓扑运动周期为基础，根据卫星节点链路状态确定卫星航点的位置；利用分段路由灵活规划分组传输路径的机制，提前响应网络拓扑变化，计算得到一条不受网络拓扑快照切换影响的传输路径。基于NS-3仿真平台进行仿真实验，设置源节点与目标节点在反向缝同侧与不同侧两种场景，选取优化链路状态路由（optimized link state routing,OLSR）算法和最短路径算法与WSR进行时延抖动与分组丢失率的对比分析。实验证明WSR与OLSR相比，两种场景下最大时延抖动分别降低46 ms与126 ms，分组丢失率分别降低30%和21%，并且能够解决拓扑快照切换导致分组传输路径中断的问题。     

Route selection in IEEE 802.11 wireless mesh networks

This paper addresses the problem of route selection in IEEE 802.11 based Wireless Mesh Networks (WMNs). Traditional routing protocols choose the shortest path between two routers. However, recent research reveals that there can be enormous differences between links in terms of quality (link loss ratio, interference, noise etc) and therefore selecting the shortest path (hop count metric) is a poor choice. We propose a novel routing metric—Expected Link Performance (ELP) metric for wireless mesh networks which takes into consideration multiple factors pertaining to quality (link loss ratio, link capacity and link interference) to select the best end-to-end route. Simulation based performance evaluation of ELP against contemporary routing metrics shows an improvement in terms of throughput and delay. Moreover, we propose an extension of the metric called ELP-Gateway Selection (ELP-GS) which is an extension meant for traffic specifically oriented towards the gateway nodes in the mesh network. We also propose a gateway discovery protocol which facilitates the dissemination of ELP-GS in the network. Simulation results for ELP-GS show substantial improvement in performance.     

面向动态拓扑网络的深度强化学习路由技术

针对现有智能路由技术无法适用于动态拓扑的不足,提出了一种面向动态拓扑的深度强化学习智能路由技术,通过使用图神经网络近似PPO(Proximal Policy Optimization)强化学习算法中的策略函数与值函数、策略函数输出所有链路的权值、基于链路权值计算最小成本路径的方法,实现了路由智能体对不同网络拓扑的泛化....     

一种基于跳数和时延的MPLS自适应流量工程算法

提出了一种基于跳数和时延的MPLS自适应流量工程算法，该算法根据LSP的跳数和时延来进行流量分配，从而减少由传统路由算法而引起的网络拥塞，优化网络资源的利用。仿真结果表明，该算法简单易行，性能良好。     

Avoidance of multicast incapable branching nodes for multicast routing in WDM networks

In this article we study the multicast routing problem in all-optical WDM networks under the spare light splitting constraint. To implement a multicast session, several light-trees may have to be used due to the limited fanouts of network nodes. Although many multicast routing algorithms have been proposed in order to reduce the total number of wavelength channels used (total cost) for a multicast session, the maximum number of wavelengths required in one fiber link (link stress) and the end-to-end delay are two parameters which are not always taken into consideration. It is known that the shortest path tree (SPT) results in the optimal end-to-end delay, but it can not be employed directly for multicast routing in sparse light splitting WDM networks. Hence, we propose a novel wavelength routing algorithm which tries to avoid the multicast incapable branching nodes (MIBs, branching nodes without splitting capability) in the shortest-path-based multicast tree to diminish the link stress. Good parts of the shortest-path-tree are retained by the algorithm to reduce the end-to-end delay. The algorithm consists of tree steps: (1) a DijkstraPro algorithm with priority assignment and node adoption is introduced to produce a SPT with up to 38% fewer MIB nodes in the NSF topology and 46% fewer MIB nodes in the USA Longhaul topology, (2) critical articulation and deepest branch heuristics are used to process the MIB nodes, (3) a distance-based light-tree reconnection algorithm is proposed to create the multicast light-trees. Extensive simulations demonstrate the algorithm’s efficiency in terms of link stress and end-to-end delay.     

RATES: a server for MPLS traffic engineering

It has been suggested that one of the most significant reasons for multiprotocol label switching (MPLS) network deployment is network traffic engineering. The goal of traffic engineering is to make the best use of the network infrastructure, and this is facilitates by the explicit routing feature of MPLS, which allows many of the shortcomings associated with current IP routing schemes to be addressed. This article describes a software system called Routing and Traffic Engineering Server (RATES) developed for MPLS traffic engineering. It also describes some new routing ideas incorporated in RATES for MPLS explicit path selection. The RATES implementation consists of a policy and flow database, a browser-based interface for policy definition and entering resource provisioning requests, and a Common Open Policy Service protocol server-client implementation for communicating paths and resource information to edge routers. RATES also uses the OSPF topology database for dynamically obtaining link state information. RATES can set up bandwidth-guaranteed label-switched (LSPs) between specified ingress-egress pairs. The path selection for LSPs is on a new minimum-interference routing algorithm aimed at making the best use of network infrastructure in an online environment where LSP requests arrive one by one with no a priori information about future requests. Although developed for an MPLS application, the RATES implementation has many similarities in components to an intradomain differentiated services bandwidth broker     

Wavelength Routing Algorithm of All Optical Network Based on Traffic Engineering

General multi-protocol label switching （GMPLS） based on traffic engineering is one of the possible methods to implement all-optical network. This method implements the network with IP technique and guarantees the quality of service with traffic engineering. Based on the establishment of selecting schemes of optical path and methods of traffic calculation, the wavelength routing algorithm of all-optical network based on traffic engineering is presented by combining with prior route of shortest path and traffic engineering, the algorithm procedures are given, and the actual examples are introduced as well as the analysis on simulation calculation. This research results have certain significance for the achievement of optical switching technique of all-optical network.     

Historical data learning based dynamic LSP routing for overlay IP/MPLS over WDM networks

Overlay IP/MPLS over WDM network is a promising network architecture starting to gain wide deployments recently. A desirable feature of such a network is to achieve efficient routing with limited information exchanges between the IP/MPLS and the WDM layers. This paper studies dynamic label switched path (LSP) routing in the overlay IP/MPLS over WDM networks. To enhance network performance while maintaining its simplicity, we propose to learn from the historical data of lightpath setup costs maintained by the IP-layer integrated service provider (ISP) when making routing decisions. Using a novel historical data learning scheme for logical link cost estimation, we develop a new dynamic LSP routing method named Existing Link First (ELF) algorithm. Simulation results show that the proposed algorithm significantly outperforms the existing ones under different traffic loads, with either limited or unlimited numbers of optical ports. Effects of the number of candidate routes, add/drop ratio and the amount of historical data are also evaluated.     

Performance evaluation of adaptive routing algorithms in packet‐switched intersatellite link networks

This paper addresses the performance evaluation of adaptive routing algorithms in non‐geostationary packet‐switched satellite communication systems. The dynamic topology of satellite networks and variable traffic load in satellite coverage areas, due to the motion of satellites in their orbit planes, pose stringent requirements to routing algorithms. We have limited the scope of our interest to routing in the intersatellite link (ISL) segment. In order to analyse the applicability of different routing algorithms used in terrestrial networks, and to evaluate the performance of new algorithms designed for satellite networks, we have built a simulation model of a satellite communication system with intersatellite links. In the paper, we present simulation results considering a network‐uniform source/destination distribution model and a uniform source–destination traffic flow, thus showing the inherent routing characteristics of a selected Celestri‐like LEO satellite constellation. The updates of the routing tables are centrally calculated according to the Dijkstra shortest path algorithm. Copyright © 2002 John Wiley & Sons, Ltd.     

MPLS流量工程及基于约束路由计算的研究

论述了 MPLS 网络的架构及其对流量工程的支持,研究了基于 MPLS 流量工程要解决的几个主要问题：如何把数据包映射为转发等价类等,并对其中最重要的一个——通过 LSP 把流量中继映射到实际网络拓扑,提出了一种约束最短路径优先算法的实现方法。     

RPR高生存性网络的约束路由算法的研究

在分析RPR高生存性网络的拓扑结构的特性基础上,引进了约束路由算法的概念,并且提出了一种以跨环次数和跳数为约束条件的最短路径的路由选择算法.通过网络仿真工具OPNET仿真验证,结果表明该算法在网络时延方面有一定优越性.