Multihop lightwave networks: a comparison of store-and-forward andhot-potato routing

The achievable aggregate capacity for a variant of the basic multihop approach in which minimum distance store-and-forward routing is replaced by a hot-potato routing algorithm is determined. With hot-potato routing, all packets simultaneously arriving at a given node and not intended for reception at that node are immediately placed onto the outbound links leaving that node; if two or more packets contend for the same outgoing link to achieve a minimum distance routing, then all but one will be misrouted to links which produce longer paths to the eventual destination. Attention is confined to the development of an analytical methodology for finding the probability distribution of the number of hops with hot potato routing for symmetric networks under uniform traffic load. Results show that the maximum throughput achievable with hot-potato routing can be as low as 25% of that for store-and-forward routing, and that the relative degradation increases as the number of nodes grows larger. This implies that the link speed up needed to produce a significant overall capacity advantage with hot potato should be at least a factor of 10     

Sharp approximate models of deflection routing in mesh networks

Deflection routing is a simple, decentralized, and adaptive method for routing data packets in communication networks. The focus of this work is on deflection routing in the Manhattan street network (a two-dimensional directed mesh), although the analytic approach should apply to any regular network. Two approximate performance models that give sharp estimates of the steady-state throughput and the average packet delay for packets admitted to the network are presented. The results of extensive simulation experiments are reported, which corroborate the models' predictions. The results show that deflection routing is very effective. Two measures of the merit of a network for deflection routing are its diameter and its deflection index. Networks are presented whose diameter and deflection index are near the optimal values     

On the stability of shuffle-exchange and bidirectionalshuffle-exchange deflection networks

In a stable packet-switched network, throughput equals offered load and packet backlogs do not build up in an unbounded manner. A network with an unstable operating region poses the problem that it may evolve eventually to a stable but saturated operating point with a low throughput. This paper considers the shuffle-exchange and bidirectional shuffle networks when operated with deflection routing. It is shown that both networks exhibit instability when packet contention is resolved in a random manner. However, instability can be avoided if contention is resolved in a manner that favors packets closest to their destinations. This obviates the need for complicated network access control to prevent instability     

采用偏射路由算法的全光分组网络的性能分析

本文提出采用统一的马尔可夫链方法分析存储转发路由和偏射路由算法的网络，并在具体计算偏射概率时，采用了递推的算法。着重分析了偏射路由算法在无存储器、有单个存储器及有两个存储器的情况下，ＭａｎｈａｔｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和ＳｈｕｆｌｅＮｅｔ网络的性能，包括网络吞吐量、数据包的平均跳转次数和数据包跳转次数的概率分布，并对ＭａｎｈａｔａｎＳｔｒｅｅｔＮｅｔｗｏｒｋ和Ｓｈｕｆ－ｆｌｅＮｅｔ两种网络进行了简单的比较。     

Packet scheduling algorithms and performance of a bufferedshufflenet with deflection routing

In a multihop network, packets go through a number of hops before they are absorbed at their destinations. In routing to its destination using minimum path, a packet at a node may have a preferential output link (the so-called “care” packet) or may not (the so-called “don't care” packet). Since each node in an optical multihop network may have limited buffer, when such buffer runs out, contention among packets for the same output link can be resolved by deflection. In this paper, we study packet scheduling algorithms and their performance in a buffered regular network with deflection routing. Using shufflenet as an example, we show that high performance (in terms of throughput and delay) can he achieved if “care” packets can be scheduled with higher priority than “don't care” packets. We then analyze the performance of a shufflenet with this priority scheduling given the buffer size per node. Traditionally, the deflection probability of a packet at a node is solved from a transcendental equation by numerical methods which quickly becomes very cumbersome when the buffer size is greater than one packet per node. By exploiting the special topological properties of the shufflenet, we are able to simplify the analysis greatly and obtain a simple closed-form approximation of the deflection probability. The expression allows us to extract analytically the performance trend of the shufflenet with respect to its buffer and network sizes. We show that a shufflenet indeed performs very well with only one buffer, and can achieve performance close to the store-and-forward case using a buffer size as small as four packets per node     

Analytical evaluation of improved access techniques in deflectionrouting networks

This paper presents an extension of a known analytical model for the performance evaluation of nonpriority deflection routing networks in uniform traffic. The extension allows the analysis of improved access techniques. The key features of the analytical technique are described by casting it in a very simple setting: nonpriority hot-potato in a two-connected slotted shufflenet (SN) network. Results are presented for three access techniques: transmit-no-hold (TXNH), transmit-hold (TXH), and bypass queuing (BQ)     

A performance model of deflection routing in multibuffer networkswith nonuniform traffic

Deflection routing can be used in networks whose stations have the same number of input and output links. Fixed length packets arrive synchronously on the station's input links at the beginning of time slots, and each packet is routed via the output link that offers the shortest path to its destination. Since the number of packet buffers at each output link is finite, the simultaneous contention of two packets for the last buffer of a common output link must be resolved by “deflecting” one of the packets to another output link. Thus, the deflection of a packet could result in the packet following a route that is not a shortest path. The potentially unbounded number of routes that a given packet can take makes analyzing the performance of such networks difficult. In particular, there are no analytical models that can analyze multibuffer deflection-routing networks with nonuniform traffic. Using independence assumptions, the authors develop a performance model of deflection routing that allows to estimate accurately and efficiently the mean transport time and throughput in a network that has any given two-connected topology, multiple buffers at each output port, and an arbitrary traffic matrix     

规则全光分组网络中偏射路由算法的分析

就在ShuffleNet和Manhattan Street Network两种规则网络中使用偏射路由算法后的网络性能以及允许一个时隙插入多个数据包对该算法的影响进行了分析。结果说明，偏射路由算法不仅能使网络得到较高的性能，而且发挥了网状网具有迂回路由的能力。当采用允许插入多个数据包的策略时，网络的吞吐量和平均跳转次数都有小幅度的增加。     

A fast and reliable routing technique for wireless mesh networks

In wireless mesh networks (WMNs), real time communications (e.g., Voice over IP (VoIP) and interactive video communications) may often be interrupted as packets are frequently lost or delayed excessively. This usually happens due to the unreliability of wireless links or buffer overflows along the routing paths. The mesh connectivity within the WMN enables the capability to enhance reliability and reduce delay for such applications by using multiple paths for routing their packets. The vital components in multi‐path routing for achieving this are the pre‐determined formation of paths and the technique that the paths are deployed for packet traversal. Therefore, we propose a novel multi‐path routing protocol by introducing a new multi‐path organization and a traffic assignment technique. The designed technique dubbed as FLASH (Fast and reLiAble meSH routing protocol) discovers one primary path between a pair of source and destination based on a new proposed metric, and thereafter selects mini‐paths, which connect pairs of intermediate nodes along the primary path. The primary path and mini‐paths are concurrently deployed, as multiple copies of packets are routed through. This technique compensates for possible outage at intermediate wireless nodes or their corresponding wireless links along the primary path. Routing along mini‐paths is performed in such a way that redundant copies do not cause an excessive congestion on the network. The effectiveness of the proposed scheme is evaluated analytically and through extensive simulations under various load conditions. The results demonstrate the superiority of the proposed multi‐path organization in terms of reliability and satisfactory achievements of the protocol in enhancing delay and throughput compared to the existing routing protocols, especially for long distances and in congested conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance of hypercube routing schemes with or without buffering

Considers two different hypercube routing schemes, which are called the simple and the priority schemes. The authors evaluate the throughput of both the unbuffered and the buffered version of these schemes for random multiple node-to-node communications. The results obtained are approximate, but very accurate as simulations indicate, and are given in particularly interesting forms. They find that little buffer space (between one and three packets per link) is necessary to achieve throughput close to that of the infinite buffer case. They also consider two deflection routing schemes, called the simple nonwasting deflection and the priority nonwasting deflection schemes. They evaluate their throughput-using simulations, and compare them to the priority scheme     

OBS网络中基于拥塞避免的提前偏射路由研究

突发竞争是OBS(光突发交换)网络需要解决的关键问题,偏射路由作为一种有效的竞争解决方案而被广泛研究。文章提出了一种基于拥塞避免的提前偏射路由算法,利用周期性反馈的网络拥塞信息按一定概率提前偏射部分突发包。与传统的最短偏射路由算法相比,本算法达到了避免拥塞以及均衡网络负载的目的。仿真结果表明:文章所提算法在突发丢失率、吞吐量以及平均链路利用率方面性能都有所提高。     

Deflection routing in hypercube networks

An approximate analysis of the transient and steady state behavior of deflection routing in hypercube networks is presented, under a uniform traffic model. In deflection routing congestion causes packets admitted to the network to be temporarily misrouted rather than buffered or dropped. The approximations show that deflection routing performs remarkably well in hypercube networks, for small as well as large networks and for the whole range from light to heavy load. Simulations suggest that the approximations are quite accurate     

A Study on Deflection Routing in Optical Burst-Switched Networks

A major concern in optical burst-switched networks is contention,which occurs when multiple bursts contend for the same link. While a deflection routing protocol is proposed as one of the contention resolution techniques,there has been no appropriate deflection routing algorithm to find an alternate route. In this paper, we formulate a deflection routing problem based on the burst blocking rate resulting from resource contention in an optical burst-switched network. This algorithm minimizes the contention on the alternate path with the minimum distance. Furthermore, in this paper, we develop an analytical model for the deflection routing time when deflection routing is performed to resolve contention. In this model, we investigate the expected deflection routing time considering that the burst could be dropped even with deflection routing due to another contention on the alternate path. Simulations are conducted to show that there is an improvement in terms of burst loss rate and network throughput.     

Unslotted deflection routing: a practical and efficient protocolfor multihop optical networks

This paper is concerned with all-optical networks using deflection routing and time division multiplexing. Slotted networks make use of the synchronous arrival of the packets to the routers to minimize locally the number of deflections. We show that the difference in performance between slotted and unslotted networks is mainly due to the fact that unslotted networks cannot easily perform such local optimization. We also show that minimizing locally the number of deflections in unslotted networks gives rise to an NP-complete problem. To overcome this problem, we have designed a heuristic whose aim is to limit locally the number of deflections. We experimentally demonstrate that this heuristic enhances unslotted routing almost at the same performance level as slotted routing. As a consequence, we have shown that unslotted deflection routing can be implemented is a way which makes it a competitive alternative to slotted deflection routing for optical time division multiplexing deflection networks     

Congestion control in asynchronous, high-speed wormhole routingnetworks

High-speed networks use lightweight protocols and a simple switch architecture for achieving higher speeds. A lightweight switching technique for local area and campus environments is wormhole routing, in which the head of a packet (worm), upon arriving at an intermediate switch, is immediately forwarded to the next switch on the path. Thus, the packet, like a worm, may stretch across several intermediate switches and links. Wormhole routing networks provide low latency. However, they are particularly prone to congestion, thus requiring careful flow control. The authors consider high-speed, asynchronous, unslotted wormhole routing networks. For such networks, two different flow control mechanisms are compared and contrasted, namely, backpressure flow control and deflection routing (with local input rate control). With backpressure, in order to maintain deadlock-free routing, either up/down routing or shortest path routing with virtual channels is assumed. With deflection routing, to avoid livelocks, worm alignment (delayed deflection) is performed at the switches. It is shown via simulation that the throughput performance of the two schemes is comparable (except for up/down routing). The authors also discuss the tradeoffs with respect to the complexity of hardware, routing protocols and buffer requirements. The authors further examine the role of input rate control at the hosts to overcome unbounded delays typical of deflection routing, and show it is possible to achieve lower average number of hops and transit delays by employing suitable input rate control policies     

GeoDTN<Emphasis Type="Bold">+</Emphasis>Nav: Geographic DTN Routing with Navigator Prediction for Urban Vehicular Environments

Position-based routing has proven to be well suited for highly dynamic environment such as Vehicular Ad Hoc Networks (VANET) due to its simplicity. Greedy Perimeter Stateless Routing (GPSR) and Greedy Perimeter Coordinator Routing (GPCR) both use greedy algorithms to forward packets by selecting relays with the best progress towards the destination or use a recovery mode in case such solutions fail. These protocols could forward packets efficiently given that the underlying network is fully connected. However, the dynamic nature of vehicular network, such as vehicle density, traffic pattern, and radio obstacles could create unconnected networks partitions. To this end, we propose GeoDTN+Nav, a hybrid geographic routing solution enhancing the standard greedy and recovery modes exploiting the vehicular mobility and on-board vehicular navigation systems to efficiently deliver packets even in partitioned networks. GeoDTN+Nav outperforms standard geographic routing protocols such as GPSR and GPCR because it is able to estimate network partitions and then improves partitions reachability by using a store-carry-forward procedure when necessary. We propose a virtual navigation interface (VNI) to provide generalized route information to optimize such forwarding procedure. We finally evaluate the benefit of our approach first analytically and then with simulations. By using delay tolerant forwarding in sparse networks, GeoDTN+Nav greatly increases the packet delivery ratio of geographic routing protocols and provides comparable routing delay to benchmark DTN algorithms.     

Deflection routing in IP optical networks

This paper deals with optical packet switching in a full-IP transport network scenario. Given the technological limits of accomplishing packet buffering in the optical domain, deflection routing is here explored as an alternative technique for resolving packet contentions without buffering packets. Two different network topologies have been considered here, that is a regular six-node network with different connectivity factors and the classical NSF network. A limited amount of optical buffering is considered in the switching nodes that performs both input queuing and shared queuing of packets to be switched. The performance improvements that can be obtained by deflection routing have been evaluated considering different methods for choosing the alternative paths where to deflect packets that cannot be transmitted onto the shortest path to the addressed destination.     

QUACS: Routing Data Packets in Ad Hoc Networks on Buffer-Constrained Load Balancing Conditions During Emergency Rescue Crisis

Mobile wireless networks have been gaining popularity since the turn of the new millennium as they enable communication to take place without fixed communication infrastructure. This form of communication, which has been made possible by radio links proved its usefulness during emergency medical rescues such as an Ebola pandemic, battlefield communications or other emergency situations, where quick communication is of paramount importance. Nature-inspired algorithms such as AntHocNet, AntSense, among other ant inspired techniques, have been mimicked in solving the communication challenges in wireless networks, but they focus mostly on the ‘next-hop’ in determining routing of data packets from the source to the destination, which tends to suffer from congestion-related problems. Ant routing methods focus more on next-hop neighbours when choosing the shortest path which might have many data packets and are prone to congestion. Focusing on the next-hop neighbours poses a challenge of having other nodes that end up being congested. This problem of routes being heavily used, often decreases throughput rates, leading to the proposed Queuing Ant Colony System (QUACS) which is a bio-inspired, complementing the queuing optimisation approach in routing of data packets across the network. The results of simulations show that QUACS performs better in throughput, packet delivery ratio, end-to-end delay and communication overhead than other ant routing algorithms. This study is particularly beneficial in the ad hoc networks where the QUACS routing method can greatly assist in faster communication and evacuation in emergency for treatment of patients during emergency medical rescue operations.     

TIE Breaking: Tunable Interdomain Egress Selection

In a large backbone network, the routers often have multiple egress points they could use to direct traffic toward an external destination. Today's routers select the ldquoclosestrdquo egress point, based on the intradomain routing configuration, in a practice known as early-exit or hot-potato routing. In this paper, we argue that hot-potato routing is restrictive, disruptive, and convoluted and propose an alternative called TIE (Tunable Interdomain Egress selection). TIE is a flexible mechanism that allows routers to select the egress point for each destination prefix based on both the intradomain topology and the goals of the network administrators. In fact, TIE is designed from the start with optimization in mind, to satisfy diverse requirements for traffic engineering and network robustness. We present two example optimization problems that use integer-programming and multicommodity-flow techniques, respectively, to tune the TIE mechanism to satisfy networkwide objectives. Experiments with traffic, topology, and routing data from two backbone networks demonstrate that our solution is both simple (for the routers) and expressive (for the network administrators).     

Routing in frequency-hop packet radio networks with partial-bandjamming

Research in adaptive, decentralized routing for frequency-hop packet radio networks with mobile partial-band jamming. A routing technique called least-resistance routing (LRR) is developed, and various versions of this routing method are examined. LRR uses a quantitative assessment of the interference environment experienced by a radio's receiver to determine a resistance value for that radio. Two components for the interference environment are considered: transmissions from other radios and partial-band jamming. The resistances for each of the radios in a particular path are combined to form the path resistance, and packets are forwarded on the path with the smallest resistance. Comparisons are made between different versions of LRR and between LRR and previously developed adaptive routing techniques. It is found that LRR is an effective way for dealing with mobile jamming in a frequency-hop packet radio network. Significant increases in throughput and end-to-end probability of success are obtained with LRR