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Software Defined Networking (SDN) is a powerful approach that enhances network control and management, and provides a flexible way to develop network applications. However, scalability of SDN networks is an important concern for many network operators. The main peculiarities of SDN when applied to an Internet Service Provider (ISP) network are the large geographical extension and the need of in-band transmission of control traffic. Therefore, the control traffic exchanged between the SDN controller and the network nodes must be carefully evaluated for the network design and dimensioning. We consider an ISP network controlled by the recently ONOS (Open Network Operating System) controller developed by ON.Lab. We devise a quantitative model to compute the exact number of exchanged OpenFlow messages and the corresponding bandwidth needed to install a traffic flow when running the default ONOS layer-2 forwarding applications. We compute also the exact number of flow rules installed in each switch. We show the general applicability of our models for a Point Of Presence (POP) network and for a large set of real nationwide and worldwide ISP networks. Our quantitative models can be used for a safe network planning also when the network applications are not fully reactive.

a b s t r a c t NFV and SDN are nowadays seen as a solid opportunity by telecom operators to reduce costs while at the same time providing new and better services. Recently, the Unify project proposed a multi-layered architecture that, leveraging different levels of abstraction, can orchestrate and deploy generic network services on the physical infrastructure of the telecom operator. In this paper, we exploit such an architecture to deliver end-to-end generic services in presence of multiple concurring players (e.g. network operator, end-users), leveraging a new simple data model. Particularly, we propose a description-based approach allowing to deploy agile, implementation-independent and high-level network services over a distributed set of resources. The resulting data model can abstract generic services, including both middleboxbased (e.g., firewalls, NATs, etc.) and traditional LAN-based ones (e.g., a BitTorrent client). Finally, two distinct prototypes, originated by different design principles, are implemented in order to validate our proposal with the aim of demonstrating the adaptability of our approach to different contexts.

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