ABSTRACT
The interest in network virtualization has been growing steadily among the networking community in the last few years. Network virtualization opens up new possibilities for the evolution path to the Future Internet by enabling the deployment of different architectures and protocols over a shared physical infrastructure. The deployment of network virtualization imposes new requirements and raises new issues in relation to how networks are provisioned, managed and controlled today. The starting point for this paper is the network virtualization reference model conceived in the framework of the EU funded 4WARD project. In this paper we look at network virtualization mainly from the perspective of the network infrastructure provider, following the 4WARD network virtualization architecture and evaluate the main issues and challenges to be faced in commercial operator environments. Categories and Subject Descriptors C.2.3 [Computer-Communication Networks]: Network Architecture and Design General Terms Design, Management Keywords Network Virtualization, Resource Management
1. INTRODUCTION
In the last few years, the concept of network virtualization has attracted a great deal of attention from industry and research fora. Although it is not a strictly new concept, a network virtualization “renaissance” has been originated mainly from the realization that it can provide a platform upon which novel network architectures can be built, experimented and evaluated, freed from legacy technology constraints. Furthermore, network virtualization has been heralded as the keystone of a new global Internet architecture, a new component enabling the coexistence of multiple networking approaches, thus overcoming the present Internet “ossification” problem and stimulating the development and deployment of new network technologies and advanced applications. In addition, virtualization is expected to provide a clean separation of services and infrastructure and facilitate new ways of doing business by allowing the trading of network resources among multiple providers and customers. Up to now the concept of network virtualization has been explored essentially in testbeds, on a limited scale. Several proposals for network virtualization architecture or for the utilization of network virtualization in several contexts have been put forward [2, 3, 4, 5, 12, 13]. However, so far, the impact of network virtualization on the underlying physical infrastructure has been relatively overlooked. In particular, the feasibility of the network virtualization concept in large scale operator networks has not been adequately assessed. There are multiple challenges associated with the deployment of network virtualization in operator infrastructures. A few examples are how to enforce isolation between different virtual networks, how to conciliate a wide range of requirements of different virtual networks, how to fulfill carrier-class level reliability, how to guarantee scalability. In this paper, we are mainly interested in evaluating the impact of virtualization on the underlying network infrastructure. We use the 4WARD network virtualization architecture as the main reference [1].
2. OVERVIEW AND STATE OF THE ART
2.1 From VPNs to VNs In general, virtualization provides an abstraction between user and physical resources, so that the user gets the illusion of direct interaction with those physical resources. In the last few years, significant advances in operating system virtualization technologies have been achieved, with contributions from major players [6, 7, 8, 9], which has enabled the use of virtualization in a growing number of contexts and applications. Major router vendors are also following this trend and it seems likely that network virtualization will become a reality in operator networks in a not too distant future [10, 11]. The concept of network virtualization is not new – it was materialized in the past (albeit in a limited way) with networkbased VPNs1, which have been a highly successful approach to provide separate virtual networks over a common physical infrastructure. One may wonder why full-blown network


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