Exploring online virtual networks mapping with stochastic bandwidth demand in multi-datacenter

Network virtualization serves as a promising technique for providing a flexible and highly adaptable shared substrate network to satisfy the diversity of demands and overcoming the ossification of Internet infrastructure. As a key issue of constructing a virtual network (VN), various state-of-the-art algorithms have been proposed in many research works for addressing the VN mapping problem. However, these traditional works are efficient for mapping VN which with deterministic amount of network resources required, they even deal with the dynamic resource demand by using over-provisioning. These approaches are obviously not advisable, since the network resources are becoming more and more scarce. In this paper, we investigate the online stochastic VN mapping (StoVNM) problem, in which the VNs are generated as a Poisson process and each bandwidth demand x _i follows a normal distribution, i.e., x _i ~ N(μ _i , σ _i ²). Firstly, we formulate the model for StoVNM problem by mixed integer linear programming, which with objective including minimum-mapping-cost and load balance. Then, we devise a sliding window approach-based heuristic algorithm w-StoVNM for tackling this NP-hard StoVNM problem efficiently. The experimental results achieved from extensive simulation experiments demonstrate the effectiveness of the proposed approach and superiority than traditional solutions for VN mapping in terms of VN mapping cost, blocking ratio, and total net revenue in the long term.     

Upgrade-aware virtual infrastructure mapping in software-defined elastic optical networks

An emerging use case in software-defined networking is to provide efficient mapping of multiple virtual infrastructures (VIs) simultaneously over the same physical substrate (PS) which can increase the resource utilization of the PS, thus improving its provider’s revenue. In this paper, for the first time, we investigate a practical and yet theoretically challenging issue related to dynamic VI mapping in software-defined elastic optical networks while considering the presence of possible upgrade of the VIs and the optical layer constraints, which has not been addressed in any of the existing studies. More specifically, we investigate the following aspects: (1) Which revenue models are appropriate? (2) How to map a new VI request or to upgrade an existing VI to maximize the PS providers revenue? In particular, we study two different revenue models in terms of the incremental pricing policy and the binding pricing policy and propose a number of efficient heuristics to solve the upgrade-aware VI mapping (U-VIM) problem. We also perform comprehensive performance evaluation in different scenario, and the results show that plan-ahead is a desirable strategy when conducting VI mapping in the presence of VI upgrade.     

An algorithm of virtual network mapping for underwater wireless optical networks

Optical networks have been considered as the most capable technology for supplying the ever-increasing network bandwidth demand generated by the new Internet services. However, a significant challenge for optical networks is to provide an efficient manner to recover the lost communications due to failures. A failure in a system component or an optical fiber link can shut down all the crossing lightpaths, which may lead to a decrease in the revenue for clients or some sanctions to the providers due to an unattended agreed service level. In this work, we propose an adaptive–alternative path restoration algorithm, named NrPSR-R. The proposal has an adaptation capability according to the network state. NrPSR-R finds the Nr routes with minimum cost and selects one of them using a pre-defined policy. We performed a parametric analysis of the NrPSR-R algorithm. We also compared our proposal to other well-known restoration algorithms on different scenarios and NrPSR-R outperformed the others.     

Survivable virtual topology mapping in IP-over-WDM networks using differential evolution optimization

In IP-over-wavelength division multiplexing networks, a virtual topology is placed over the physical topology of the optical network. Given that a simple link failure or a node failure on the physical topology can cause a significant loss of information, an important challenge is to make the routing of the virtual topology on to the physical topology survivable. This problem is known as survivable virtual topology mapping (SVTM) and is known to be an NP-complete problem. So far, this problem has been optimally solved for small instances by the application of integer linear programming and has been sub-optimally solved for more realistic instances by heuristic strategies such as ant colony optimization and genetic algorithms. In this paper, we introduce the application of differential evolution (DE) to solve the SVTM problem and enhancements based on DE are proposed as well. Three algorithms based on DE are developed. The enhanced variants have better convergence rate, get better quality of solutions and require few control parameters. We present the impact of these parameters on the system’s performance improvement. Algorithms are evaluated in different test bench optical networks, as NSFnet and USA, demonstrating that the enhanced DE algorithm overcomes the other two, for small instances. The three algorithms reach a 100  survivable mapping for small instances. The three algorithms also find positive survivable mappings and reduce the network wavelength links. Results show the effectiveness and efficiency of the proposed algorithms.     

Dynamic fragments awareness based virtual network mapping strategy of elastic optical networks

As virtual networks services emerge increasingly with higher diversification, the issue of spectrum fragments presents great challenge to the elastic optical networks (EON), especially under heaven services burdens. Aimed to solve this problem, this article proposes a dynamic fragments awareness based virtual network mapping (DFA-VNM) strategy of elastic optical network. In this proposed approach, the dynamic fragments awareness model of it is established, which takes available bandwidth demand and spectrum fragment degree into consideration. Moreover, the dynamic fragments awareness based virtual network mapping strategy makes full advantage of real-time fragments awareness result to conduct virtual network service mapping operation with less fragments and lower blocking rate. Testing results show that the proposed approach is able to improved services supporting ability of EON.     

Physical impairments awareness based virtual network mapping strategy of elastic optical networks

As virtual networks services emerge increasingly with higher requirement of flexibility and robust, great complex challenges caused by physical-layer impairments are presented to the elastic optical networks(EON). Aimed to solve this problem, this paper proposes a physical impairment awareness based virtual network mapping stragegy of EON. The physical impairments awareness model is established, including both of linear factors and nonlinear ones. On this basis, this paper proposes a virtual network mapping strategy with detailed procedures, combined with node importance factors during the virtual network mapping procedure. Test results show that the proposed approach is able to reduce blocking rate and enhance services supporting ability of EON.     

区分服务QoP的可生存虚拟网络映射算法研究

用户对虚拟网保护需求呈现多样化的趋势,针对如何实现不同需求的可生存虚拟网映射是当前研究亟待解决的问题。建立了区分保护质量（QoP）的可生存虚拟网络映射问题的数学模型,然后提出了一种启发式算法进行求解。该算法包括广度优先搜索的节点映射策略和区分QoP的链路映射策略。模拟实验表明,该算法不仅能满足用户不同的虚拟网保护需求,而且相比现有算法降低了底层网络资源开销。     

Avoiding collision with hidden nodes in IEEE 802.11 wireless networks

In wireless networks, collision is a major factor of performance degradation. In this letter, we propose a scheme for reducing collision in IEEE 802.11 networks. Each node can avoid collision by maintaining a disjoint set of time slots for transmission. Through simulation, we show that the proposed scheme is effective to reduce collision even in the presence of hidden nodes.     

Resource management with virtual paths in ATM networks

A virtual path connection (VPC) is a labelled path which can be used to transport a bundle of virtual channel connections (VCCs) and to manage the resources used by these connections. The virtual network is organized as a collection of VPCs which form a VPC, or logical, overlay network. If the VPCs are permanent or semi-permanent and have reserved capacity, establishing new VCCs requires simple connection admission decisions at the VPC terminators of existing VPCs. This would enable faster connection establishment since transit nodes are not involved in the connection setup. The virtual path concept also allows the possibility of segregating traffic types according to quality of service requirements. However, the extent to which VPC provisioning is able to improve network efficiency is dependent on the resource management decisions that determine the VPC topology and capacity allocations. The article surveys resource management using virtual paths in an ATM network. Of interest are techniques which modify the VPC topology and capacity assignments in order to adapt to changing traffic conditions and possible network failures. The resource management activities employed to facilitate such adaptation can be categorized by the timescale on which they operate. On the shortest timescale are strategies for dynamically making minor changes to the VPC topology or capacity assignments. On a somewhat longer timescale are strategies for making more widespread modifications to the VPC overlay network. This would be appropriate for traffic changes based on time of day and for recovering from network failures. Finally, on an even longer timescale, strategies may be employed to design a general VPC overlay network, to be used at startup or after major network upgrades. Solutions to VPC resource management for each of these timescales are discussed     

Routing in ad hoc networks: a case for long hops

For multihop wireless networks, a fundamental question is whether it is advantageous to route over many short hops (short-hop routing) or over a smaller number of longer hops (long-hop routing). Short-hop routing has gained a lot of support, and its proponents mainly produce two arguments: reduced energy consumption and higher signal-to-interference ratios. Both arguments stem from a simplified analysis based on crude channel models that neglects delay, end-to-end reliability, bias power consumption, the impact of channel coding, mobility, and routing overhead. In this article we shed more light on these issues by listing 18 reasons why short-hop routing is not as beneficial as it seems to be. We also provide experimental evidence to support this claim. The conclusion is that for many networks, long-hop routing is in every aspect a very competitive strategy.     

基于最小化平均分组跳的波长路由环网逻辑拓扑设计

本文提出了用混合整数线性规则（ＭＩＬＰ）进行波长路由环网的逻辑拓扑设计。对于给定的通信流量矩阵,其目标函数是最小经平均分组跳。以双向环网为例,对于不同网络结构参数的情况,进行了计算分析并给出了数值结果。对双向环网和单向环网的网络性能进行了比较分析。     

Routing with hexagonal virtual coordinates in wireless sensor networks

Using geographic routing, like GPSR, is efficient for ad hoc and wireless sensor networks, but it requires that nodes be aware of their physical positions. However, if there are holes in the network, routing across them using GPSR will lead to a lot of overloaded nodes on their boundaries. In this paper, we propose a distributed protocol, named hexagonal virtual coordinate (HVC), for constructing a virtual coordinate system. After the HVC is constructed, the nodes in the network will be aware of the relative coordinates among the landmarks through the HVC chart. Based on the HVC chart, a source node can find an auxiliary routing path (ARP) to indicate the direction of the journey from the source to the destination. Simulation results show that our protocol can support geographic routing efficiently, and the landmarks found by our protocol are uniformly located in the network even if some holes exist within it. In addition, our protocol is resilient to various network shapes and can find a load balancing routing path to the destination even if this path comes across holes in the network. Copyright © 2008 John Wiley & Sons, Ltd.     

Measuring performance degradation of virtual machines based on the Bayesian network with hidden variables

In the virtualized environment, multiple virtual machines (VMs) sharing the same physical host are vulnerable to resource competition, which may cause performance interference among VMs and thus lead to VM performance degradation. This paper focuses on measuring CPU, memory, I/O, and the overall VM performance degradation caused by the performance interference according to the properties in the runtime environment of VMs. To this end, we adopt Bayesian network (BN), as the framework for uncertainty representation and inference, and construct a VM property‐performance BN (VPBN) with hidden variables, which represent the unobserved performance degradation of CPU, memory, and I/O, respectively. Then, we present the method to measure performance degradation of VMs by probabilistic inferences with the VPBN. Experimental results show the accuracy and efficiency of our method.     

Scalability implications of virtual private networks

This article gives an overview of the most promising technologies for service providers to offer virtual private network services. The focus is on the analysis of the scalability implications of these virtual private network mechanisms on existing service provider backbone networks. Very often, when deploying VPN services, service providers will be confronted with a trade-off between scalability and security. VPNs that require site-to-site interconnectivity without strong (cryptographic) security can be deployed in a scalable way based on the network-based VPN model, as long as the interaction between the customer and provider routing dynamics are controlled. VPNs that require strong (end-to-end) cryptographic security should be deployed according to the CPE-based VPN model, using the available IPsec protocol suite     

Throughput analysis considering coupling effect in ieee 802.11 networks with hidden stations

This letter investigates the throughput performance of the IEEE 802.11 networks with hidden stations. Note that the decoupling approximation of the Bianchi?s Markov chain model is valid for the IEEE 802.11 networks with a large number of the hidden stations. Hence, we propose a new analytic model to accommodate the effect of the hidden stations and estimate the network throughput based on the analytic model.     

Optimal network-aware virtual data center embedding

Recently, the virtual data center embedding (VDCE) problem has drawn significant attention because of a growing need for efficient means of data center resource allocation. By ensuring a set of virtual data center (VDC) integration requests coming from his customers, among the main concern of an infrastructure provider is the maximization of the utilization rate of data center resources and benefits. However, existing VDCE solutions mostly focus on consolidating virtual machines in a single physical data center. Therefore, in this work, we improve the consolidated targets techniques, that consider only the virtual machines integration, by the consideration of network devices and fabrics (e.g., switches and paths/links). We consider new unreleased constraints such as multiple virtual nodes of the same request co-location, and intermediate node requirements when a virtual link is mapped. To address the above problem, in this paper, we propose a binary linear programming-based model, called BLP-VDCE, to solve the VDCE problem with network-aware consideration. This model ensures a simultaneous consolidated embedding of virtual nodes and virtual links. Extensive simulations show that solving the proposed BLP-VDCE model can efficiently embed VDC requests with a high physical resource utilization rate.     

On the cost of virtual private networks

A virtual private network (VPN) is a private data network that uses a nonprivate data network to carry traffic between remote sites. An “Intranet VPN” establishes network layer connectivity between remote Intranet sites by creating an IP overlay network over the nonprivate network, using various tunneling mechanisms. There are two approaches for establishing such tunnels: a “CPE-based approach” and a “network-based approach.” In the first approach, tunnels are established only between the CPE devices, whereas in the second approach tunnels are also established between the routers of the core nonprivate network. In this paper we address the problem of determining a CPE-based and a network-based layout of VPN tunnels while taking into account two factors: the cost of the links over which the VPN tunnels are established and the cost of the core routers that serve as end points for the VPN. We define related graph algorithm problems, analyze their complexity, and present heuristics for solving these problems efficiently     

Administration of restorable virtual path mesh networks

This article addresses key issues related to the administration of ATM backbones based on virtual paths with embedded restoration capabilities. The concept of logical subnetworking according to the required reliability of service (RoS) is presented. This is followed by an investigation into alternative protocols for activating preplanned backup VPs with shared capacity protection, whereby speed and robustness are of special interest. Finally, a method for rerouting VPs by translation table alteration is presented