Generalized load sharing for packet-switching networks. I. Theory and packet-based algorithm

In this paper, we propose a framework to study how to effectively perform load sharing in multipath communication networks. A generalized load sharing (GLS) model has been developed to conceptualize how traffic is split ideally on a set of active paths. A simple traffic splitting algorithm, called packet-by-packet weighted fair routing (PWFR), has been developed to approximate GLS with the given routing weight vector by transmitting each packet as a whole. We have developed some performance bounds for PWFR and found that PWFR is a deterministically fair traffic splitting algorithm. This attractive property is useful in the provision of service with guaranteed performance when multiple paths can be used simultaneously to transmit packets which belong to the same flow. Our simulation studies, based on a collection of Internet backbone traces, reveal that PWFR outperforms two other traffic splitting algorithms, namely, packet-by-packet generalized round robin routing (PGRR), and packet-by-packet probabilistic routing (PPRR).     

Generalized load sharing for packet-switching networks. II. Flow-based algorithms

For pt.1 see ibid., p.694-702 (2006). In this paper, we extend the load sharing framework to study how to effectively perform flow-based traffic splitting in multipath communication networks. The generalized load sharing (GLS) model is employed to conceptualize how traffic is split ideally on a set of active paths. A simple flow-based weighted fair routing (WFR) algorithm, called call-by-call WFR (CWFR), has been developed to imitate GLS so that all packets belonging to a single flow are sent on the same path. We have investigated how to couple the proposed basic packet-by-packet WFR (PWFR) and CWFR algorithms so as to permit a traffic splitter to handle both connection-oriented and connectionless traffic simultaneously. Our simulation studies, based on a collection of Internet backbone traces, reveal that WFR outperforms two other traffic splitting algorithms, namely, generalized round robin routing (GRR), and probabilistic routing (PRR). These promising results form a basis for designing future adaptive constraint-based multipath routing protocols.     

基于应用层流量优化的中继路径选择方案

基于网络层路由协议的缺省单一路径难以满足高带宽应用的端到端传输需求,多径传输是一种有效方式。在基于应用层中继的多径传输系统的基础上,提出基于应用层流量优化的中继路径选择方案：借助于应用层流量优化机制,提出中继路径选择过程中遵循的规则,提出基于运营商定义域的最优中继路径生成算法,为数据传输分配优质的中继路径,同时在运营商定义域之间以及中继服务转发器之间保持负载均衡。仿真结果表明,提出的方案在选择优质中继路径方面具有较优性能,同时能够灵活地均衡运营商定义域之间的负载。     

On the resource utilization and traffic distribution of multipath transmission control

There is growing interest in the development and deployment of multipath rate and route control mechanisms for the Internet, due to their ability to exploit bandwidth resources, alleviate network congestion, and provide robustness against failures. However, two performance issues have been uncovered: low link utilization when the number of flows is small, and route flappiness, namely the traffic of a flow tends to concentrate on one path and then another. In this paper we study these issues with respect to several variations of multipath rate and route control algorithms. We demonstrate the qualitatively different impacts that the couplings of the increase and decrease phases have on link utilization. We also demonstrate how the coupling strength affects both the long-term and short-term traffic distributions among different paths. In particular, we show that the flappy behavior is prominent only when there is strong coupling in both the increase and decrease phases, and when the number of good paths is small.     

基于生命期预测的移动Ad hoc网络多径路由策略

在移动自组网中,由于网络节点的移动性和拓扑结构的多态性,多路径路由在稳定性,均衡负载方面优于单路径路由,非常适合Ad hoc网络。考虑到移动自组网中节点能量的局限性,在DSR协议的基础上提出了一种新型的多径路由算法。该算法结合节点路径的能量消耗率,预测出链路的生命期,以求找到多条有效路径并进行传输。仿真结果表明,该协议比DSR具有更好的吞吐量和端到端延迟。     

Routing Internet traffic in heterogeneous mesh networks: Analysis and algorithms

In practical wireless mesh networks (WMNs), gateways are subject to hard capacity limits on the aggregate number of flows (in terms of bit rate) that they can support. Thus, if traffic is routed in the mesh network without considering those constraints, as well as the traffic distribution, some gateways or intermediate mesh routers may rapidly get overloaded, and the network resources can be unevenly utilized. To address this problem, in this paper we firstly develop a multi-class queuing network model to analyze feasible throughput allocations, as well as average end-to-end delay, in heterogeneous WMNs. Guided by our analysis, we design a Capacity-Aware Route Selection algorithm (CARS), which allocates network paths to downstream and upstream Internet flows so as to ensure a more balanced utilization of wireless network resources and gateways’ fixed connections. Through simulations in a number of different network scenarios we show that the CARS scheme significantly outperforms conventional shortest path routing, as well as an alternative routing method that distributes the traffic load on the gateway nodes to minimize its variance.     

Investigating the performance of TCP in mobile ad hoc networks

Mobile ad hoc networks have several inherent characteristics (e.g. dynamic topology, time-varying and bandwidth constrained wireless channels, multi-hop routing, and distributed control and management). The goal of this work is to investigate the impact of these characteristics on the performance of TCP. First, we investigate throughput performance of TCP as a function of path length (i.e. multiple wireless hops), node mobility, and traffic intensity. Next, we examine the ‘fairness’ of the ad hoc network with regard to equal sharing of network bandwidth among multiple TCP flows. Third, we evaluate the impact of two on-demand routing protocols (i.e. AODV and DSR) on the throughput of TCP. Finally, a factorial design experiment is conducted to quantify the effects and interactions of three factors, which influence the throughput of TCP. These factors include routing, node speed, and node pause time. Two key results were observed. Results show that traffic intensity (e.g. number of concurrent flows) is significantly affects TCP throughput, suggesting the need for congestion control, scheduling and traffic management schemes. Second, source routing achieves higher throughputs while also generating significantly less routing overhead than AODV. Results also show that in some instances, the fairness of the network is very uneven among concurrent TCP flows, resulting in several sending stations achieving very little or no throughput.     

Game Theoretic Stochastic Routing for Fault Tolerance and Security in Computer Networks

We introduce the game-theoretic stochastic routing (GTSR) framework, a proactive alternative to today's reactive approaches to route repair. GTSR minimizes the impact of link and router failure by 1) computing multiple paths between source and destination and 2) selecting among these paths randomly to forward packets. Besides improving fault tolerance, the fact that GTSR makes packets take random paths from source to destination also improves security. In particular, it makes connection eavesdropping attacks maximally difficult as the attacker would have to listen on all possible routes. The approaches developed are suitable for network layer routing, as well as for application layer overlay routing and multipath transport protocols such as the stream control transmission protocol (SCTP). Through simulations, we validate our theoretical results and show how the resulting routing algorithms perform in terms of the security/fault-tolerant/delay/throughput trade-off. We also show that a beneficial side effect of these algorithms is an increase in throughput, as they make use of multiple paths.     

一种混和路径选择准则下的多径路由协议

在Ad Hoc无线网络环境下，提出了一种基于DSDV的多径路由协议HC-MRP。HC-MRP路由协议利用跨层的思想，提出了一种基于最短路径准则和最佳信道状态准则的混和路径选择准则，并通过建立一个邻居节点表结构，实现了多径扩展，多径的传输模式采用多径独立传输模式。仿真表明，HC-MRP协议以少量的递交率性能为代价，提高了整个网络的吞吐量。     

无线网状网络的多路径路由与调度算法

提出了一种保障服务质量的多路径路由算法,数据分组可通过多条不同的路径进行传输,以提升网络总吞吐量性能.进一步提出了一种多路径调度策略.通过使用调度策略,基于当前可用带宽信息和路径所引入的时延信息,数据分组在传输前可被分成多段并通过不同的路径发送,根据路径时延调整优化调度策略,从而使得数据可通过在不同的路径上进行更高效地传输.仿真实验进一步验证了本文提出的路由机制和调度策略在不同网络负载下的优越性.     

BGP-XM: BGP eXtended Multipath for transit Autonomous Systems

Multipath interdomain routing has been proposed to enable flexible traffic engineering for transit Autonomos Systems (ASes). Yet, there is a lack of solutions providing maximal path diversity and backwards compatibility at the same time. The BGP-XM (Border Gateway Protocol-eXtended Multipath) extension presented in this paper is a complete and flexible approach to solve many of the limitations of previous BGP multipath solutions. ASes can benefit from multipath capabilities starting with a single upgraded router, and without any coordination with other ASes. BGP-XM defines an algorithm to merge into regular BGP updates information from paths which may even traverse different ASes. This algorithm can be combined with different multipath selection algorithms, such as the K-BESTRO (K-Best Route Optimizer) tunable selection algorithm proposed in this paper. A stability analysis and stable policy guidelines are provided. The performance evaluation of BGP-XM, running over an Internet-like topology, shows that high path diversity can be achieved even for limited deployments of the multipath mechanism. Further results for large-scale deployments reveal that the extension is suitable for large deployment since it shows a low impact in the AS path length and in the routing table size.     

A real-time traffic control scheme of multiple AGV systems forcollision free minimum time motion: a routing table approach

A two-staged traffic control scheme, in which sets of candidate paths are prepared off-line prior to overall motion planning process, has been widely adopted for motion planning of mobile robots, but relatively little attention has been given to the application of the two-staged scheme to multiple automated guided vehicle systems (MAGVSs). In the paper, a systematic two-staged traffic control scheme is presented to obtain collision-free minimum-time motions of AGVs along loopless paths. The overall structure of the controller is divided into two tandem modules of off-line routing table generator (RTG) and an online traffic controller (OTC). First, an induced network model is established considering the configurational restrictions of guide-paths. With this model and a modified k-shortest path algorithm, RTG finds sets of k candidate paths from each station nodes to all the other station nodes off-line and stores them in the form of routing tables. Each time a dispatch command for an AGV is issued, OTC utilizes these routing tables to generate a collision-free minimum-time motion along a loopless path. Real-time computation is guaranteed in that the time-consuming graph searching process is executed off-line by RTG, and OTC looks for the minimum time motion among the k candidate paths. The traffic control scheme proposed is suitable for practical application in centralized MAGVS with zone blocking technique     

一种基于QoS的无线传感器网络路由协议

针对无线传感器网络中不同应用的QoS需求,提出了一种路由协议QMR。该协议使用节点剩余能量、可用缓存以及信道质量等度量值综合评估路径传输可靠性,根据量化的评估值构建自源节点至目的节点的多条路径;并引入路径选取模型,允许数据包依据优先级同时在多条路径上传输;接着采用按通信量更新策略,根据网络流量情况动态调整路由更新频率。通过仿真实验分析得出,该协议在降低网络能耗、提供差别服务方面具有良好的性能。     

移动WSN节点不相交多路径路由算法

针对移动无线传感器网络不相交多路径路由中的路径断裂问题,提出基于HSV色彩空间的节点不相交多路径路由算法。采用HSV色彩空间模型为每条链路建立数值化的（h,s,v）三元组,使其属于不同的色彩平面,以寻找从源节点到目标节点的多条节点不相交路径。针对节点移动问题,设计基于可变时间间隔链路接收信号强度指示值探测的不相交多路径维护机制,该机制无需借助地理位置信息。实验结果表明,当使用3条路径传输时,该算法的数据传输成功率可达到80％以上,而对比的经典算法均低于70％。此外,其在网络吞吐量、能量消耗等方面也具有较好的性能。     

Network coding based reliable disjoint and braided multipath routing for sensor networks

This paper presents network coding based reliable disjoint and braided multipath routing (NC-RMR ) for sensor networks, which forms multipath by hop-by-hop method and only maintains local path information of each node without establishing end-to-end paths. Neighbors of each local node are divided into groups according to their hops to sink nodes to improve the network load balancing. For further performance improvement of NC-RMR with disjoint multipath model, local nodes select their own backup nodes in neighbor nodes to form additional logical paths, which implement a braided multipath model. Security advantages of NC-RMR with multipath and network coding mechanisms are analyzed. Analytical and simulation results prove that braided multipath routing model has better performance over disjoint model, and NC-RMR protocol can reduce the required number of transmission paths, ensure load balance of sensor network system, reduce the energy consumption of nodes.     

Scalable and fair forwarding of elephant and mice traffic in software defined networks

A software defined network decouples the control and data planes of the networking devices and places the control plane of all the switches in a central server. These flow based networks do not scale well because of the increased number of switch to controller communications, limited size of flow tables and increased size of flow table entries in the switches. In our work we use labels to convey control information of path and policy in the packet. This makes the core of the network simple and all routing and policy decisions are taken at the edge. The routing algorithm splits the elephant traffic into mice and distributes them across multiple paths, thus ensuring latency sensitive mice traffic is not adversely affected by elephant traffic. We observed that label based forwarding and traffic splitting work well together to enable scalable and fair forwarding. Our approach is topology independent. We present here a few preliminary simulation results obtained by running our routing algorithm on random network topologies.     

多跳无线网络中基于网络编码的多路径路由

提出了一种基于网络编码的多路径路由机制CAMP(network coding-aware multi-path routing).该机制能够根据路径的可靠性和编码机会,动态地在多条路径上进行数据包的传输.CAMP的路由发现机制能够向源节点返回多条可能的路径以及各条路径的每条边上的ETX(expected transmission count).与以往的多路径路由机制不同, CAMP可以通过转换它的传输路径来动态地创造而非仅仅等待编码机会.利用这一独特的路由机制,CAMP可以让多条路径分摊网络流量负载,并且最大化路径转换收益,从而改进网络的吞吐量.实验结果表明,在无线网络的数据传输过程中,CAMP能够取得比其他路由机制高得多的网络吞吐量.     

All-to-all disjoint multipath routing using cycle embedding

In this paper, we evaluate the performance of disjoint multipath routing approaches for all-to-all routing in packet-switched networks with respect to packet overhead, path length, and routing table size. We develop a novel approach based on cycle embedding to obtain two node-disjoint paths between all source–destination pairs with reduced number of routing table entries maintained at a node (hence the reduced lookup time), small average path length, and less packet overhead. We study the trade-off between the number of routing table entries maintained at a node and the average length of the two disjoint paths by: (a) formulating the cycle-embedding problem as an integer linear program; and (b) developing a heuristic. We show that the number of routing table entries at a node may be reduced to at most two per destination using cycle-embedding approach if the average length of the disjoint paths are allowed to exceed the minimum by 25%.     

Transient chaotic neural network-based disjoint multipath routing for mobile ad-hoc networks

Due to mobility of wireless hosts, routing in mobile ad-hoc networks (MANETs) is a challenging task. Multipath routing is employed to provide reliable communication, load balancing, and improving quality of service of MANETs. Multiple paths are selected to be node-disjoint or link-disjoint to improve transmission reliability. However, selecting an optimal disjoint multipath set is an NP-complete problem. Neural networks are powerful tools for a wide variety of combinatorial optimization problems. In this study, a transient chaotic neural network (TCNN) is presented as multipath routing algorithm in MANETs. Each node in the network can be equipped with a neural network, and all the network nodes can be trained and used to obtain optimal or sub-optimal high reliable disjoint paths. This algorithm can find both node-disjoint and link-disjoint paths with no extra overhead. The simulation results show that the proposed method can find the high reliable disjoint path set in MANETs. In this paper, the performance of the proposed algorithm is compared to the shortest path algorithm, disjoint path set selection protocol algorithm, and Hopfield neural network (HNN)-based model. Experimental results show that the disjoint path set reliability of the proposed algorithm is up to 4.5 times more than the shortest path reliability. Also, the proposed algorithm has better performance in both reliability and the number of paths and shows up to 56% improvement in path set reliability and up to 20% improvement in the number of paths in the path set. The proposed TCNN-based algorithm also selects more reliable paths as compared to HNN-based algorithm in less number of iterations.     

Congestion control based dynamic routing in ATM networks

In this paper we describe briefly a dynamic multi-path algorithm that has been considered for connection oriented asynchronous transfer mode (ATM) networks. Our scheme takes advantage of a cell multiplexing capability that has particular advantage in networks supporting variable bit rate (VBR) traffic. The fundamental objective of the scheme is to propose a congestion control based scheme that bridges the gap between routing and congestion control as the network becomes congested. The proposed routing scheme works as a shortest path first algorithm under light traffic conditions. However, as the shortest path becomes congested under unbalanced heavy traffic, the source uses multiple paths when and if available to distribute the calls and reduce cell loss. This mechanism will provide good Quality of Service for clients within the given constraints. We compare the performance of the proposed scheme with other competitive schemes. The throughput and cell loss performance are compared via simulations. These have been carried out concentrating on a five node network, each with varying traffic patterns, with the intention of gaining insight into the strengths and weaknesses of the various schemes.