Effects of a Priority Discipline in Routing for Packet-Switched Networks

This paper addresses itself to some comparisons of adaptive routing algorithms in store-and-forward Communication nets. The intent here is to demonstrate how some relatively simple add-ons to already existing adaptive algorithms can decrease the average message delay and increase message throughput in the network. The overview of many existing routing algorithms is intended to point out that, although an algorithm may be adaptive, it is not necessarily good in terms of the performance measures addressed in this paper. The basic objective of this study is to assess the effects of endogenous priority assignment to messages that have reached some specified aging threshold while in the network and to note the effects of Such priority assignment on network performance. The performance measures are average message delay, throughput, and number of messages undelivered. The routing techniques are demonstrated via simulation on an 8node highly connected network and a 19-node Advanced Research Projects Agency (ARPA) network. The routing algorithms are applied with and without network element destruction on the selected networks.     

Adaptive wavelength routing in all-optical networks

We consider routing and wavelength assignment in wavelength-routed all-optical networks (WAN) with circuit switching. The conventional approaches to address this issue consider the two aspects of the problem disjointly by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which we consider all paths between a source-destination (s-d) pair and incorporate network state information into the routing decision. This approach performs routing and wavelength assignment jointly and adaptively, and outperforms fixed routing techniques. We present adaptive routing and wavelength assignment algorithms and evaluate their blocking performance. We obtain an analytical technique to compute approximate blocking probabilities for networks employing fixed and alternate routing. The analysis can also accommodate networks with multiple fibers per link. The blocking performance of the proposed adaptive routing algorithms are compared along with their computational complexity     

局部双环网络的拓扑优化及其路由算法

本文对局部双环网络拓扑最优化进行了研究，提出了一类适应于该网络的路由算法。     

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.     

TCP/IP网络的整体稳定性和优化研究

TCP/IP网络中有一些路由选择和流量控制方法只能保证系统局部最优。本文引入现代控制理论,提出通过对TCP/IP数据通信网非线性状态控制模型进行线性近似,并借助李亚普诺夫原理的途径判断数据通信网整体稳定性的方法;在稳定性的基础上,证明了数据网最优控制可以具有路由最短和路由不形成环路等性质。     

Evaluation of multicast routing algorithms for real-timecommunication on high-speed networks

Multicast (MC) routing algorithms capable of satisfying the quality of service (QoS) requirements of real-time applications will be essential for future high-speed networks. We compare the performance of all of the important MC routing algorithms when applied to networks with asymmetric link loads. Each algorithm is judged based on the quality of the MC trees it generates and its efficiency in managing the network resources. Simulation results over random networks show that unconstrained algorithms are not capable of fulfilling the QoS requirements of real-time applications in wide-area networks. Simulations also reveal that one of the unconstrained algorithms, reverse path multicasting (RPM), is quite inefficient when applied to asymmetric networks. We study how combining routing with resource reservation and admission control improves the RPM's efficiency in managing the network resources. The performance of one semiconstrained heuristic, MSC, three constrained Steiner tree (CST) heuristics, Kompella, Pasquale, and Polyzos (1992), constrained adaptive ordering (CAO), and bounded shortest multicast algorithm (BSMA), and one constrained shortest path tree (CSPT) heuristic, the constrained Dijkstra heuristic (CDKS) are also studied. Simulations show that the semiconstrained and constrained heuristics are capable of successfully constructing MC trees which satisfy the QoS requirements of real-time traffic. However, the cost performance of the heuristics varies. The BSMA's MC trees are lower in cost than all other constrained heuristics. Finally, we compare the execution times of all algorithms, unconstrained, semiconstrained, and constrained     

Multicommodity flow models, failure propagation, and reliable lossnetwork design

Multicommodity flow (MF) models are well known and have been widely used in the design of packet-switched networks. They have also been used as approximations in the design of circuit-switched networks with reliability constraints. We investigate the usefulness of multicommodity models both as routing models and as an integral part of design models conceived under the failure propagation strategy. First, we compare the performance measures calculated by the models with results produced by a real-time technique. Next, we study the performance of networks dimensioned with flow models and with known adaptive models under failures of transmission facilities when a real-time routing technique is used. Results obtained using realistic data show that the MF models compare favorably with exact dimensioning algorithms when failures are considered     

WDM全光网自适应路由和波长分配算法

研究了无波长转换WDM全光网的路由和波长分配算法（RWA）。通过对已有算法的分析和比较,提出了一种自适应最小跳数路由算法（ADMH）。此算法以最小跳数路由为基础,同时考虑网络状态的变化,因而不仅能尽量少使用网络资源,也能使网络资源的分布保持均衡。计算机模拟仿真的结果表明,这种算法性能在各种网络参数条件下优于或等于已有算法。     

A distributed routing algorithm for multihop packet radio networkswith uni- and bi-directional links

Multihop packet radio networks require routing algorithms which are distributed in nature and which have the ability to timely detect changes in the network topology. These changes are mostly changes in connectivity caused by link or node failures and by the relative motion of the nodes. This paper describes and analyzes an adaptive decentralized routing algorithm for packet radio networks. The network connectivity, as perceived by each node, is translated into a graph representation of the network. The proposed routing mechanism then uses a breadth-first search algorithm along the inbound links of such a graph. Unlike most of the algorithms found in the open literature the one proposed here can be used in networks having both uni- and bi-directional radio links. Examples are shown to illustrate the methodology     

Region-Based Routing: A Mechanism to Support Efficient Routing Algorithms in NoCs

An efficient routing algorithm is important for large on-chip networks [network-on-chip (NoC)] to provide the required communication performance to applications. Implementing NoC using table-based switches provide many advantages, including possibility of changing routing algorithms and fault tolerance, due to the option of table reconfigurations. However, table-based switches have been considered unsuitable for NoCs due to their perceived high area and power consumption. In this paper, we describe the region-based routing (RBR) mechanism which groups destinations into network regions allowing an efficient implementation with logic blocks. RBR can also be viewed as a mechanism to reduce the number of entries in routing tables. RBR is general and can be used in conjunction with any adaptive routing algorithm. In particular, we have evaluated the proposed scheme in conjunction with a general routing algorithm, namely segment-based routing (SR) and an Application Specific Routing Algorithm (APSRA) using regular and irregular mesh topologies. Our study shows that the number of entries in the table is significantly reduced, especially for large networks. Evaluation results show that RBR requires only four regions to support several routing algorithms in a 2-D mesh with no performance degradation. Considering link failures, our results indicate that RBR combined with SR is able to tolerate up to 7 link failures in an 8 $,times,$8 mesh. RBR also reduces area and power dissipation of an equivalent table-based implementation by factors of 8 and 10, respectively. Moreover, the degradation in performance of the network is insignificant when using APSRA combined with RBR.      

QoS multicast routing scheme using QGA in IP/DWDM networks

This article studies multi-constraints least-cost multicast routing problem in internet protocol over dense wavelength division multiplexing （IP/DWDM） networks. To address this problem, an individual-difference-based quantum genetic algorithm （IDQGA） is proposed. This algorithm considers individual differences among chromosomes by introducing an adaptive rotation angle step determination scheme and a grouping-based quantum mutation operation. Simulations are conducted over network topologies. The results indicate that compared with other heuristic algorithms, IDQGA has better optimal performance on solving quality of service （QoS） multicast routing problem in IP/DWDM networks and is characterized by strong robustness, high success ratio and excellent capability on global searching.     

A fuzzy control approach for adaptive traffic routing

The application of fuzzy control to adaptive traffic routing in telephone networks is investigated. The authors use, on one hand, the properties of fuzzy control techniques and adaptive routing, on the other hand, to derive a routing system that is robust and efficient. They analyze the impact of various availability indicators on performance, which indicates that the choice of a suitable indicator must be made to characterize circuit group availability. When used in the fuzzy control framework the indicator used appears clearly to improve the performance of the routing algorithm as compared to existing routing systems. On the other hand, the use of this indicator in a classical way appears to be of poor utility. The study compares the performance of methods usually applied to adaptive traffic routing and the fuzzy control approach and shows that the fuzzy control approach could provide an effective framework for robust control of traffic routing in communications networks. Research studies still need to be carried out to develop fuzzy adaptive routing on different network structures and to evaluate its impact on performance     

Link-State-Based Algorithms for Dynamic Routing in All-Optical Networks with Ring Topologies

The increased usage of large bandwidth in optical networks raises the problems of efficient routing to allow these networks to deliver fast data transmission with low blocking probabilities. Due to limited optical buffering in optical switches and constraints of high switching speeds, data transmitted over optical networks must be routed without waiting queues along a path from source to destination. Moreover, in optical networks deprived of wavelength converters, it is necessary for each established path to transfer data from source to destination by using only one wavelength. To solve this NP-hard problem, many algorithms have been proposed for dynamic optical routing like Fixed-Paths Least Congested (FPLC) routing or Least Loaded Path Routing (LLR). This paper proposes two heuristic algorithms based on former algorithms to improve network throughput and reduce blocking probabilities of data transmitted in all-optical networks with regard to connection costs. We also introduce new criteria to estimate network congestion and choose better routing paths. Experimental results in ring networks show that both new algorithms achieve promising performance.     

Adaptive load-balancing in WDM mesh networks with performance guarantees

In nowadays, wavelength-division multiplexing (WDM) networks, on the one hand, increasingly more users expect the network to provide high-priority QoS services demanding no congestion and low latency. On the other hand, it is significantly more difficult for network operators to forecast future traffic demands, as the packet traffic running over WDM networks fluctuates over time for a variety of reasons. Confronted with a rough understanding of traffic patterns as well as the increasing number of time-sensitive applications, most networks today are grossly over-provisioned. Thus, designing cost-effective WDM networks in an uncertain traffic environment, which includes network planning and robust routing, is both an important and a challenging task. In this paper, we explore adaptive load-balancing to investigate the problems of network planning and robust routing for WDM mesh networks under varying traffic matrices. We first propose an efficient heuristic algorithm called Maximizing Network Capability (MNC) to provision congestion-free and cost-effective WDM networks based on load-balancing to deal with traffic uncertainty. Then, a novel traffic grooming algorithm called Adding Direct Traffic (ADT) is proposed to implement robust routing with partial traffic information. Finally, we demonstrate by simulation that MNC consumes less resources than previous methods and performs quite close to the optimal solution, while ADT achieves the desirable performance in delay, jitter (delay variation), and throughput compared with existing robust routing and traffic grooming algorithms.     

一种自适应动态缓存策略准入控制算法

针对片上网络的死锁问题,基于虚拟网络的自适应路由算法,设计了一个完全自适应片上路由器.重点介绍了路由算法及路由器的系统结构,设计实现了一个低代价、高效的完全自适应路由器,并在2DMesh拓扑结构下对其性能进行了模拟验证.实验结果表明,该路由器实现了无死锁的自适应路由,并提高了网络吞吐量,降低了平均网络延迟.     

跳频分组无线网的路由算法分析

跳频分组无线网抗干扰性好,保密性强,广泛应用于战术通信系统。讨论了几种跳频分组无线网的路由选择算法,着重分析了针对传输多类型分组跳频网的ALR路由算法,并将此路由算法的性能与DAR算法的性能进行了比较,证实了该算法在吞吐量、端-端正确传输率等方面都优于传统的方法。     

Performance comparison of trust-based reactive routing protocols

Ad hoc networks, due to their improvised nature, are frequently established in insecure environments and hence become susceptible to attacks. These attacks are launched by participating malicious nodes against different network services. Routing protocols, which act as the binding force in these networks, are a common target of these nodes. A number of secure routing protocols have recently been proposed, which make use of cryptographic algorithms to secure the routes. However, in doing so, these protocols entail a number of prerequisites during both the network establishment and operation phases. In contrast, trust-based routing protocols locate trusted rather than secure routes in the network by observing the sincerity in participation by other nodes. These protocols thus permit rapid deployment along with a dynamically adaptive operation, which conforms with the current network situation. In this paper, we evaluate the performance of three trust-based reactive routing protocols in a network with varying number of malicious nodes. With the help of exhaustive simulations, we demonstrate that the performance of the three protocols varies significantly even under similar attack, traffic, and mobility conditions. However, each trust-based routing protocol has its own peculiar advantage making it suitable for application in a particular extemporized environment.     

An approximate analysis of the performance of deflection routing inregular networks

Regular two-dimensional architectures are being considered as alternatives to the linear topology metropolitan area networks (MANs) that are popular today. Deflection routing is an adaptive routing strategy that performs well on such architectures. A general analytic model has been developed to study the performance of buffered deflection routing in regular networks. The Manhattan street network, the ShuffleNet, and the shuffle exchange network have been studied as candidate two-connected networks with different topological characteristics. The results show that deflection routing performs well on both the Manhattan street network and the ShuffleNet, even under heavy loads, while on the shuffle exchange network it does not perform as well. The introduction of just a few buffers provides significant improvement in the delay-throughput performance over unbuffered deflection routing, especially in networks with large propagation delays. The analytic results are found to match the simulations very closely in most cases     

Analysis and design of a highly reliable transport architecture forISDN frame-relay networks

The authors explore control strategies in the design of a high-performance transport architecture for integrated services digital network (ISDN) frame-relay networks. For real-time congestion control, buffer management, priority queueing, adaptive windowing, and selective frame, discard policies are described that can effectively maximize network efficiency while preventing unfair usage of shared network resources. Virtual-circuit routing strategies are proposed that ensure an efficient distribution of traffic loads across the network despite variations in traffic patterns and topology changes. It is shown that source routing provides significant performance benefits over link-by-link routing, particularly in large networks that are not so densely connected. Routing table update and call acceptance mechanisms are described that provide for efficient bandwidth management in the network. Fault-tolerant strategies are described that include fast failure detection and local reroute. These strategies are capable of restoring affected virtual circuits in less than 10 s, which is adequate for session maintenance under most application scenarios