Piero Castoldi

First Experimental Assessment of ABNO-Driven In-Operation Flexgrid Network Re-Optimization

Traffic affected by link failures can be recovered using path restoration schemes. In dynamically operated networks provided with a control plane, restoration algorithms run in a centralized element, such as the path computation element (PCE). To increase traffic restorability in flexgrid networks, multiple paths, subconnections , can be used to restore every single affected connection. However, the multipath restoration scheme might result in a poor resource utilization entailing a lesser grade of service. In-operation network planning algorithms can be used to mitigate this problem once the failed link is repaired; we propose solving the so-called multipath after failure repair optimization problem (MP-AFRO) to reduce subconnections count by aggregating those belonging to the same original connection and rerouting the resulting connection to release spectral resources. The MP-AFRO problem is modeled using a mixed integer linear program formulation. In view of the complexity of the model and the limited time to solve the problem, we propose a heuristic algorithm that provides a good tradeoff between complexity and optimality. The performance on the MP-AFRO heuristic is firstly validated by simulation. Next, the heuristic algorithm is deployed inside an in-operation planning tool in the form of back-end PCE (bPCE) inside the application-based network operations architecture controlling a network; the bPCE is connected to the centralized active stateful PCE. MP-AFRO is experimentally demonstrated using a distributed field trial test-bed connecting the premises of Telefonica (Madrid), CNIT (Pisa), and UPC (Barcelona).

Time-Continuous Authorization of Network Resources Based on Usage Control

Authorization systems regulate the access to network resources, e.g., bandwidth-guaranteed circuits traversing nodes and links and shared among different media streams, assuring that only admitted data streams use the assigned resources. Traditional access control models were not designed to cope with changes that may occur in the attributes of the user, of the resource or of the environment after the access has been granted. However, in order to prevent misuse and fraud, it is important to extend the control on these attributes after the authorization decision is taken, i.e, during the actual usage of such resources. This control is particularly crucial for network resources because an abuse might cause the degradation of QoS performance for lawful admitted media streams and expose the network to Denial of Service attacks. This paper integrates an authorization system based on the Usage Control model (UCON) in the network service provisioning scenario, to enhance the evaluation of access rights during the actual usage of network resources. The relevant application scenario and architectural design as well as an example of a security policy that implements usage control are described. Finally we outline some open issues and research trends in the applicability of usage control models in networking area.