Oblivious Routing in Fat-Tree Based System Area Networks With Uncertain Traffic Demands

In optical burst switching (OBS) networks, the contention of optical bursts is the most serious problem due to the lack of buffers within the networks. Various deflection routing schemes and a routing scheme based on pre-calculated multiple paths have been proposed to resolve the contention. The latter routing scheme can successfully maintain a relatively limited transfer delay of optical bursts. This paper proposes a new decentralized routing scheme based on multiple paths to effectively resolve the contention of optical bursts. In this scheme, each source node splits the traffic load into pre-calculated multiple paths adaptively according to the measured loss rate of the optical bursts transferred through each path. This scheme does not require frequent notification of the measured loss rate because each source node selects one of the multiple paths probabilistically. In the OBS networks, the average transfer delay in the multi-path routing always exceeds that in a single-path routing because alternative paths with a larger transfer delay are also utilized in the multi-path routing. Thus, this paper proposes an adaptive load splitting method in which load splitting ratios for the multiple paths are autonomously adjusted to minimize the average transfer delay based on the condition that the required loss rate of optical bursts is satisfied. The performance of the proposed scheme was evaluated by computer simulation and based on the evaluation results; the ability of the proposed scheme to adjust the load splitting ratios for the multiple paths autonomously and avoid the contention of optical bursts adaptively is clarified even if the traffic load applied to the OBS network changes.

Variable speed limits (VSL) stands out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways. It allows variable message signs (VMSs) to dynamically determine the speed limits according to real-time traffic states. This paper introduces an innovative online feedback control approach designed to regulate speed limit values on VMSs, addressing multiple bottlenecks while considering their spatiotemporal constraints. Moreover, we offline optimize the gain coefficients of this feedback control approach in the simulation-based optimization (SBO) framework. Specifically, with average and variance of space-mean speeds as bi-objectives, a stochastic SBO model considering uncertain traffic demands and compliance behaviours is established and solved by a bi-objective surrogate-based promising area search (BOSPAS) algorithm. Real-field experiments conducted in Edmonton, Canada, demonstrate the well-performing bi-objectives of the proposed approach, especially in handling uncertain compliance behaviours and traffic demands. Compared with the uncontrolled scenario, the feedback control schemes with the offline optimized gain coefficients improve the average and variance of space-mean speeds by up to 16.2% and 20.8%, respectively. Meanwhile, by the comparison of detailed performances, it is found that the optimized control schemes perform better than the uncontrolled scheme from the overall and local aspects. In conclusion, this study puts forward a general framework that applies an online feedback control approach with gain coefficients optimized offline by an SBO method to deal with real-time decision-making problems under uncertainties.

The current state of security and availability of the Internet is far from being commensurate with its importance. The number and strength of DDoS attacks conducted at the network layer have been steadily increasing. However, the single path (SP) routing used in today’s Internet lacks a mitigation scheme to rapidly recover from network attacks or link failure. In case of a link failure occurs, it can take several minutes until failover. In contrast, multi-path routing can take advantage of multiple alternative paths and rapidly switch to another working path. According to the level of available path control, we classfy the multi-path routing into two types, first-hop multi-path (FMP) and multi-hop multi-path (MMP) routing. Although FMP routing supported by networks, such as SD-WAN, shows marginal improvements over the current SP routing of the Internet, MMP routing supported by a global Internet architecture provides strong improvement under network attacks and link failure. MMP routing enables changing to alternate paths to mitigate the network problem in other hops, which cannot be controlled by FMP routing. To show this comparison with practical outcome, we evaluate network performance in terms of latency and loss rate to show that MMP routing can mitigate Internet hazards and provide high availability on global networks by 18 participating ASes in six countries. Our evaluation of global networks shows that, if network attacks or failures occur in other autonomous systems (ASes) that FMP routing cannot avoid, it is feasible to deal with such problems by switching to alternative paths by using MMP routing. When the global evaluation is under a transit-link DDoS attack, the loss rates of FMP that pass the transit-link are affected significantly by a transit-link DDoS attack, but the other alternative MMP paths show stable status under the DDoS attack with proper operation.

Demand-oblivious routing in complex networks under uncertainty

Analysis of optimal BOT highway capacity and economic toll adjustment provisions under traffic demand uncertainty

Multipath routing in mobile ad hoc networks has recently received more research efforts, where more than one route will be searched and maintained between every source destination pair. Compared with traditional single-path routing, utilizing multiple paths in parallel would be of benefit to reduce end-to-end delivery delay as well as to split traffic for load balancing to achieve better utilization of bandwidth resources. Besides, multipath routing will enhance the route robustness in the sense of lengthening route lifetime. In this paper, we propose an analytical modeling framework to investigate multipath routing in ad hoc/multihop networks. The single-path model is considered as a multi-node M/M/1 tandem network, and the multi-path model as a set of multiple parallel paths. This proposed framework allows us to investigate issues such as optimal load distribution, end-to-end delay and multipath routing reliability in ad hoc networks. Due to the flexibility, our modeling framework is applicable to a heterogenous network as well as the homogenous case.

Multipath routing in mobile ad hoc networks has recently received more research efforts, where more than one route will be searched and maintained between every source-destination pair. Compared with traditional single-path routing, utilizing multiple paths in parallel would be of benefit to reduce end-to-end delivery delay as well as to split traffic for load balancing to achieve better utilization of bandwidth resource under moderate traffic load. Besides, multipath routing will enhance routing robustness in the sense of lengthening route lifetime. In this paper, we propose an analytical modeling framework to investigate multipath routing in ad hoc/multihop networks. The single-path model is considered as a multi-node M/M/1 tandem network with several congestion queues, and multiple paths can be viewed as several parallel rays originating from the focus of a convex lens. This proposed framework allows us to investigate issues such as optimal load distribution, end-to-end delivery delay and multipath routing reliability in ad hoc networks. Due to the flexibility, our modeling framework is applicable for heterogeneous network as well as homogeneous case

Load balancing in the provisioning of virtual private network (VPN) service in the hose model is studied. Single-path routing and tree routing for the hose model tend to aggregate bandwidth reservations on a small number of links, thus leading to congestion problems in service provider networks. If the link capacity is depleted as a result of improper routing, all future non-VPN traffic will be blocked. We propose a novel multi-objective multi-path (MOMP) routing linear program with the maximum fraction of traffic on a path (MFTP) constraint to solve the problem. The MOMP routing algorithm is able to reduce the bandwidth reservation on the most loaded link by as much as 50%, thus effectively alleviating the potential congestion problems in service provider network. The MFTP constraint provides a guarantee of the availability of multiple paths for each VPN endpoint pair. Further reduction of the bandwidth reservation can be achieved depending on the MFTP value. This is highly significant.

In ultra-dense networks (UDNs), the dense deployment of base stations (BSs) is facing challenges due to the pronounced unbalanced traffic loads, severe inter-cell interference, and uncertain traffic demands. In this paper, we tame traffic uncertainty for the joint optimization of BS activation and user association in UDNs to mitigate interference and balance traffic loads among BSs. Specifically, we address the traffic uncertainty by using chance constraint programming with the known first- and second-order statistics of the uncertain traffic. We formulate the joint BS activation and user association problem as a mixed integer non-linear programming problem, which is then decomposed into a set of user association sub-problems by modeling the BS states (active or idle) as a Markov chain. We solve the user association sub-problem at each BS state by transforming it into a convex problem over the positive orthant. In particular, at each BS state, the candidate serving BSs that lead to the optimal load balancing performance are identified for each user and parts of the user's traffic are offloaded to the identified BSs. Based on the obtained solutions, we propose a distributed near-optimal BS activation and user association scheme. Numerical results demonstrate that our proposed scheme is more robust to traffic uncertainty and provides better load-balancing performance than the existing schemes.

The Sybil attack is a particularly harmful threat to sensor networks where a single sensor node illegitimately claims multiple identities. A malicious node may generate an arbitrary number of additional node identities using only one physical device. The Sybil attack can disrupt normal functioning of the sensor network, such as the multipath routing, used to explore the multiple disjoint paths between source-destination pairs. But the Sybil attack can disrupt it when a single adversary presents multiple identities, which appear on the multiple paths. Digital certificates are a way to prove identities, but they are not suitable for the sensor network because of the large computational overheads. Researchers have proposed a light-weight identity certificate method to defeat Sybil attacks, but it is not suitable for a large scale sensor network because of the huge memory usage required at each node. In this paper, we propose a light-weight Sybil attack detection method based on a hierarchical architecture in sensor networks. The proposed method can be used in a large scale sensor network, and it only uses the symmetric cryptography avoiding the use of the public key cryptography. Simulation results show that the proposed method only needs a small memory (below 140 KB) for each node (even in a large scale sensor network). In addition, the energy consumption by new identity generations within each group is low (below 60 mJ), which is much lower than the available energy at each sensor node.

In present era, where every person has become addicted to wireless networks, MANET'S has fulfilled the demand of the people by removing the dependency of fixed network.Mobile ad-hoc networks have extended the range of mobile nodes beyond their level.Now when we talk about wireless communication, routing is the backbone of any communication.Ad hoc on demand multipath distance vector routing algorithm (AOMDV) is a very reactive protocol in MANET's.We have selected AOMDV algorithm for routing purpose as there have already been done several work with AODV.Also, in AOMDV the end to end delay is reduced by utilising several parallel paths.Various routing attacks have been identified in single path routing but here we have introduced worm hole attack in multi path routing i.e.AOMDV routing algorithm.In this paper, we have studied the performance of AOMDV algorithm under worm hole attack.Also, we have provided security and authentication to each and every node by the use of public key and private key.Different metrics of the proposed protocol has been evaluated from simulation on NS2 on different scenarios i.e. with worm hole attack and without worm hole attack and there has been a noticeable improvement in the throughput and energy consumption is also reduced.

Optical networks can benefit from multipath routing by routing traffic over diverse fiber links to fulfill bandwidth requirements, balance network load and improve resource utilization. This paper focuses on the effectiveness of multipath routing on aggregating residual bandwidth of the established lightpaths using dynamic traffic grooming. An optimization model based on Integer Linear Programing (ILP) is formulated to leverage multipath routing and grooming to serve connection requests with known duration, in a scenario where the dynamic traffic can demand bandwidth either larger or smaller than a single wavelength capacity. The impact of a balancing policy, referred to as Holding Time Balancing (HTBalancing), on multipath routing with traffic grooming in optical networks is also investigated. Numerical results show that the proposed optimization model can achieve a lower bandwidth blocking and a better load balancing with HTBalancing policy, when compared with single path routing. The proposed relaxation algorithm can effectively find near optimal solutions, and be applied in realistic scenarios.

We propose a Multiple Zones-based (M-Zone) routing protocol to discover node-disjoint multiplath routing efficiently and effectively in large-scale MANETs. Compared with single path routing, multipath routing can improve robustness, load balancing and throughput of a network. However, it is very difficult to achieve node-disjoint multipath routing in large-scale MANETs. To ensure finding node-disjoint multiple paths, the M-Zone protocol divides the region between a source and a destination into multiple zones based on geographical location and each path is mapped to a distinct zone. Performance analysis shows that M-Zone has good stability, and the control complexity and storage complexity of M-Zone are lower than those of the well-known AODVM protocol. Simulation studies show that the average end-to-end delay of M-Zone is lower than that of AODVM and the routing overhead of M-Zone is less than that of AODVM.

Multipath routes are claimed to improve throughput, end-to-end delay and the reliability of data transport in wireless sensor networks (WSNs). However we have observed that multipath routing does not perform better than single path routing because the default parameter settings in 802.11 cause high rates of packet collisions. In this paper we report the results of a series of simulations based on a full-factorial experimental design. Our results show that congestion window size and retry limit are the key factors. Simulations with the tuned parameter values show significant improvement in both zone disjoint and node disjoint multipath routing schemes.

Mobile ad hoc networks (MANETs) will play a vital role in civilian and military applications where users move around and share information with each other. The movement of users varies depending on the environment, e.g. people may move randomly in different directions (Random Waypoint and Gauss Markov mobility models); or walk, run and drive in two directions in the street (Manhattan Mobility Model); or move as a group (Reference Point Group Mobility model). The interaction between mobility patterns and routing protocols contributes significantly to vary the overall network performance. We build an analytical framework that shows an analysis structure for the overall network performance test. In this framework, we first compare the properties of the mobility models that are designated for MANETs. Second, we measure single path (proactive and reactive) and multipath (proactive and reactive) routing protocols across the mobility models by tuning into TCP and CBR traffic individually. Finally, we examine the performance of each routing protocol across mobility models and discuss the possibility of interaction between them. Most of the previous findings only evaluate the impact of mobility models and single path routing protocols with CBR traffic, whereas a significant finding of this study is that how the interaction between mobility models and single path and multipath routing protocols varies depending on the usage of traffic (TCP and CBR).