Márcio Melo

Optimal Virtual Network Embedding: Node-Link Formulation

Network Virtualization is claimed to be a key component of the Future Internet, providing the dynamic support of different networks with different paradigms and mechanisms in the same physical infrastructure. A major challenge in the dynamic provision of virtual networks is the efficient embedding of virtual resources into physical ones. Since this problem is known to be NP-hard, previous research focused on designing heuristic-based algorithms; most of them either do not consider a simultaneous embedding of virtual nodes and virtual links, or apply link-path formulation, leading to non-optimal solutions. This paper proposes an integer linear programming (ILP) formulation to solve the online virtual network embedding problem as a result of an objective function striving for the minimization of resource consumption and load balancing. To this end 3 different objective functions are proposed and evaluated. This approach applies multi-commodity flow constraint to accomplish a node-link formulation that optimizes the allocation of physical network resources. This proposal is evaluated against state of the art heuristics. The performance of the heuristics related to Virtual Network (VN) request acceptance ratio is, at least, 30% below the one of the Virtual Network Embedding Node-Link Formulation (VNE-NLF) method. From the three cost functions evaluated, the Weighted Shortest Distance Path (WSDP) is the one which embeds more VNs and also requires, on average, less physical resources per embedding.

Virtual network mapping into heterogeneous substrate networks

As the interest on Network Virtualization continues to grow, so does the awareness of the many technical obstacles to transpose before the envisioned virtualized network environment may become a reality. A significant obstacle lies on the efficient assignment of virtual resources into physical ones. Performing the so-called mapping of a virtual network into a substrate network is a computationally intensive task, due to the dual optimization required for nodes and links placement. The purpose of this paper is to tackle this problem taking into consideration real-life scenarios of network operators, where the limitations imposed by the heterogeneity of the virtual and substrate networks must be accounted for. To that end, this paper proposes a heuristic algorithm for virtual resources mapping in the physical infrastructure that supports the heterogeneity of networks, in both links and nodes. The mapping heuristic was evaluated both through simulation and in a real experimental virtualization platform. Through the simulation results, it is shown that the mapping approach is able to embed a high percentage of the Virtual Network (VNet) requests respecting all links and node constraints. With respect to the experimental results, the proposed algorithm was shown to be fast, requiring a mapping time in the order of low tens of milliseconds, and linearly scalable with the increase in the number of existing VNets.

Enhanced Media Independent Handover Framework

The Internet access paradigm is changing and a wide range of overlapping radio access technologies, such as WiMAX, Wi-Fi, 3GPP UMTS/LTE and DVB-H, will soon be available to most users and their multi-access devices. Therefore, novel mechanisms and protocols are needed to provide seamless mobility between different wireless access technologies. This paper presents novel handover procedures, based on media independent schemes, to address seamless mobility in heterogeneous environments. We propose an enhanced media independent handover framework (eMIHF), which extends IEEE 802.21 by allowing for efficient provisioning and activation of QoS resources in the target radio access technology during the handover preparation phase, and efficiently interacts with the mobility processes of different technologies employed. We evaluate eMIHF using the ns-2 simulator, and demonstrate that the proposed handover scheme provides seamless mobility, with low latency and no packet loss.

Network virtualization - opportunities and challenges for operators

In the last few years, the concept of network virtualization has gained a lot of attention both from industry and research projects. This paper evaluates the potential of network virtualization from an operators perspective, with the short-term goal of optimizing service delivery and rollout, and on a longer term as an enabler of technology integration and migration. Based on possible scenarios for implementing and using network virtualization, new business roles and models are examined. Open issues and topics for further evaluation are identified. In summary, the objective is to identify the challenges but also new opportunities for telecom operators raised by network virtualization.

A distributed approach for virtual network discovery

The ever-increasing requirements for performance, flexibility, and robustness are imposing a severe strain on the Internets stagnated architecture. Network virtualization arises as a potential solution for improving the current situation by letting multiple networks with different requirements, architectures and protocols to coexist and share the same infrastructure in an independent way. These advantages are of great interest for network operators. This paper presents a virtualization platform that enables the creation, discovery, monitoring and management of virtual networks. It then concentrates on the proposal of a distributed discovery algorithm that is able to discover both physical and virtual network topologies. This algorithm uses the concepts of level 2 multicast and spanning tree to decrease the overhead related to the exchange of discovery messages between the nodes. The simulation results show that, when compared to gossip based discovery algorithms, the performance of our approach is significantly increased, up to an improvement in exchanged messages of three orders of magnitude, when considering physical networks with 500 nodes. Experimental results have shown that distributed approaches also introduce significant improvements when compared with centralized approaches.

Resource allocation in the network operator's cloud: A virtualization approach

The access infrastructure to the Cloud is usually a major drawback that limits the uptake of Cloud services. Attention has turned to rethinking a new architectural deployment of the overall Cloud service delivery. We argue that it is not sufficient to integrate the cloud domain with the operators network domain based on the current models. In this work we envision a full integration of the Cloud and the network, where cloud resources are no longer confined to a data center, but are spread throughout the network and owned by the network operator. In such an environment, challenges arise at different levels, such as at the resource management, where both cloud and network resources need to be managed in an integrated approach. We particularly address the resource allocation problem through joint virtualization of network and cloud resources, by proposing an algorithm to allocate cloud and network resources in an integrated way. This algorithm is evaluated through both simulation and experimental results in a real virtualization platform.

Negotiating on-demand connectivity between clouds and Wide Area Networks

Infrastructure as a Service (IaaS) provides the capability to deploy infrastructure on demand, but today there are gaps in the IaaS model for network connectivity, especially when user and/or application require guaranteed connectivity between the deployed infrastructures. This problem is aggravated when virtual infrastructures are geographically distributed, for performance and redundancy reasons. Connectivity is also crucial to acquire and integrate virtual resources in remote cloud datacenters with on-site IT resources. In enterprise environments where connectivity requirements cannot be met by best effort networks like Internet, such distributed infrastructure needs to make use of VPN services for inter-domain connectivity, provided by service providers over their trusted networks. To establish this connectivity, information regarding the interconnection link, such as interfaces and underlying protocols need to be negotiated and agreed upon. Today there is a lack of a technology independent mechanism and interface to perform such negotiation. This is a hindrance to automation of on-demand connectivity. In this paper we present a protocol for dynamic negotiation of connectivity service between domains. We describe how it has been used for negotiations between OpenStack and OpenNebula cloud datacenters and MPLS-based WAN, for establishment of L2/L3 VPN services.

Optimal virtual network embedding

Network Virtualization is a key component of the Future Internet, providing the dynamic support of different networks with different paradigms and mechanisms in the same physical infrastructure. A major challenge in the dynamic provision of virtual networks is the embedding approach taking energy efficiency into account, while not affecting the overall Virtual Network (VN) acceptance ratio. Previous research focused on either designing heuristic-based algorithms to address the efficient embedding problem or to address the energy impact.This paper proposes an integer linear programming formulation, Energy Aware-Virtual Network Embedding-Node-Link Formulation (EA-VNE-NLF), that solves the online virtual network embedding as an optimization problem, striving for the minimum energy consumption and optimal resource allocation per VN mapping. Two different objective functions are proposed: (i) addressing primarily the resource consumption problem - Bandwidth Consumption Minimization (BCM); (ii) addressing primarily the energy consumption problem - Energy Consumption Minimization (ECM).The performance of each objective function is evaluated by means of simulation and compared with an existing objective function, Weighted Shortest Distance Path (WSDP), that is considered state of the art of the resource allocation problem. The simulation results show that the objective function BCM reduces the energy consumption of the physical network by 14.4%, and improves the embedding factor by 4.3%, consuming almost the same amount of resources as requested, and slightly worsening the VN acceptance ratio by 2.3%. ECM reduces the energy consumption of the physical network by 31.4% and improves the embedding factor by 4.1%, without affecting the VN acceptance ratio when compared to WSDP.

A Re-optimization Approach for Virtual Network Embedding

Network Virtualization is claimed to be a key component of the Future Internet by enabling the coexistence of heterogeneous (virtual) networks in the same physical infrastructure, providing the dynamic creation and support of different networks with different paradigms and mechanisms in the same physical network. A major challenge in the dynamic provision of virtual networks resides in the optimal embedding solution of virtual resources into physical ones.

A platform for Operator-driven Network Virtualization

Network virtualization enables the coexistence of multiple networks, running different protocols, in an infrastructure-independent way. With that goal in mind, this paper presents a Platform for Operator-driven Network Virtu-alization that builds virtual networks through a user-friendly interface, integrating virtual network mapping and creation, discovery, monitoring, and management functionalities. Besides the developed functionalities, this platform contains novel mechanisms for network discovery and mapping: a novel dynamic distributed discovery algorithm of both physical and virtual nodes, and a heuristic algorithm for mapping virtual resources in the physical infrastructure, that supports the heterogeneity of networks, with respect to both links and nodes. The platform and its features were implemented and evaluated in different scenarios. The obtained results show the scalability and feasibility of the proposed mechanisms and functionalities in a single platform for network virtualization control and management.