Joan Serrat

Design and evaluation of algorithms for mapping and scheduling of virtual network functions

Network function virtualization has received attention from both academia and industry as an important shift in the deployment of telecommunication networks and services. It is being proposed as a path towards cost efficiency, reduced time-to-markets, and enhanced innovativeness in telecommunication service provisioning. However, efficiently running virtualized services is not trivial as, among other initialization steps, it requires first mapping virtual networks onto physical networks, and thereafter mapping and scheduling virtual functions onto the virtual networks. This paper formulates the online virtual function mapping and scheduling problem and proposes a set of algorithms for solving it. Our main objective is to propose simple algorithms that may be used as a basis for future work in this area. To this end, we propose three greedy algorithms and a tabu search-based heuristic. We carry out evaluations of these algorithms considering parameters such as successful service mappings, total service processing times, revenue, cost etc, under varying network conditions. Simulations show that the tabu search-based algorithm performs only slightly better than the best greedy algorithm.

3D vehicle sensor based on monocular vision

Determining the position of other vehicles on the road is a key information to help driver assistance systems to increase drivers safety. Accordingly, the work presented in this paper addresses the problem of detecting the vehicles in front of our own one and estimating their 3D position by using a single monochrome camera. Rather than using predefined high level image features as symmetry, shadow search, etc., our proposal for the vehicle detection is based on a learning process that determines, from a training set, which are the best features to distinguish vehicles from non-vehicles. To compute 3D information with a single camera a key point consists of knowing the position where the horizon projects onto the image. However, this position can change in every frame and is difficult to determine. In this paper we study the coupling between the perceived horizon and the actual width of vehicles in order to reduce the uncertainty in their estimated 3D position derived from an unknown horizon.

Using linear temporal model checking for goal-oriented policy refinement frameworks

Policy refinement is meant to derive lower-level policies from higher-level ones so that these more specific policies are better suited for use in different execution environments. Although it has been recognized as crucial, it has received relatively little attention. We present a policy refinement framework grounded in goal-elaboration methodologies and reactive systems analysis. Through linear-time model checking, we obtain system trace executions aimed at fulfilling lower-level goals refined with the KAOS goal-elaboration method. From system executions, we abstract managed entities, conditions and actions to encode the refined policies. We present our framework and provide a refinement scenario applied to the DiffServ QoS management domain.

A Functional Solution for Goal-Ooriented Policy Refinement

Policy refinement is a key but still unsolved area of policy based management. Goal oriented requirements engineering methodologies have been suggested as a prominent alternative to address policy refinement. Practical approaches that capture the administrative requirements and enable systematic policy refinement are still missing although such integrated solutions are rather convenient to make policy-based management systems really useful. In this paper we present a functional solution for goal oriented policy refinement grounded in linear temporal logic and reactive systems analysis techniques. We describe the technical foundations and demonstrate how these were used to develop an integrated solution for policy refinement, focusing on the details of the implemented prototype. Our policy analysis techniques that enable systematic policy refinement are demonstrated through a scenario applied to the domain of QoS management for differentiated services (DiffServ) networks

Urban Computing and Mobile Devices

n this issues Works in Progress department, we have 12 urban computing and mobile device entries that span a wide range of computing and social areas. The first entry examines how an urban environment could operate as a large-scale, real-time control system. One project focuses on annotating public spaces and sharing the tags with others. Two projects tie together social networking in cyberspace with local urban communities. Two projects examine computing and social interactions in physical spaces. Two entries explore how to combine synthetic and physical views of urban environments. Four entries investigate how we explore urban spaces, interact with technology in those spaces, and create shared community histories.In this issues Works in Progress department, we have 12 urban computing and mobile device entries that span a wide range of computing and social areas. The first entry examines how an urban environment could operate as a large-scale, real-time control system. One project focuses on annotating public spaces and sharing the tags with others. Two projects tie together social networking in cyberspace with local urban communities. Two projects examine computing and social interactions in physical spaces. Two entries explore how to combine synthetic and physical views of urban environments. Four entries investigate how we explore urban spaces, interact with technology in those spaces, and create shared community histories.

A methodological approach toward the refinement problem in policy-based management systems

Policy refinement is meant to derive low-level enforceable policies from high-level guidelines. Although recent advances have been made to solve this open problem, the holistic implications confronting systematic policy refinement have not been explicitly addressed. This article presents a methodological approach towards the policy refinement problem. We provide a generic procedure to define policy hierarchies, which is essential to achieving systematic policy refinement. We also provide the considerations while defining high-level guidelines, and describe a policy refinement framework that formalizes the requirements to refine high-level guidelines into executable policies. We demonstrate the feasibility of our approach with a scenario applied to the quality of service (QoS) management domain

Design and evaluation of learning algorithms for dynamic resource management in virtual networks

Network virtualisation is considerably gaining attention as a solution to ossification of the Internet. However, the success of network virtualisation will depend in part on how efficiently the virtual networks utilise substrate network resources. In this paper, we propose a machine learning-based approach to virtual network resource management. We propose to model the substrate network as a decentralised system and introduce a learning algorithm in each substrate node and substrate link, providing self-organization capabilities. We propose a multiagent learning algorithm that carries out the substrate network resource management in a coordinated and decentralised way. The task of these agents is to use evaluative feedback to learn an optimal policy so as to dynamically allocate network resources to virtual nodes and links. The agents ensure that while the virtual networks have the resources they need at any given time, only the required resources are reserved for this purpose. Simulations show that our dynamic approach significantly improves the virtual network acceptance ratio and the maximum number of accepted virtual network requests at any time while ensuring that virtual network quality of service requirements such as packet drop rate and virtual link delay are not affected.

Dynamic resource management in SDN-based virtualized networks

Network virtualization allows for an abstraction between user and physical resources by letting a given physical infrastructure to be shared by multiple service providers. However, network virtualization presents some challenges, such as, efficient resource management, fast provisioning and scalability. By separating a networks control logic from the underlying routers and switches, software defined networking (SDN) promises an unprecedented simplification in network programmability, management and innovation by service providers, and hence, its control model presents itself as a candidate solution to the challenges in network virtualization. In this paper, we use the SDN control plane to efficiently manage resources in virtualized networks by dynamically adjusting the virtual network (VN) to substrate network (SN) mappings based on network status. We extend an SDN controller to monitor the resource utilisation of VNs, as well as the average loading of SN links and switches, and use this information to proactively add or remove flow rules from the switches. Simulations show that, compared with three state-of-art approaches, our proposal improves the VN acceptance ratio by about 40% and reduces VN resource costs by over 10%.

Creaseness from Level Set Extrinsic Curvature

Creases are a type of ridge/valley-like structures of a d dimensional image, characterized by local conditions. As creases tend to be at the center of anisotropic grey-level shapes, creaseness can be considered as a type of medialness. Among the several crease definitions, one of the most important is based on the extrema of the level set curvatures. In 2-d it is used the curvature of the level curves of the image landscape, however, the way it is usually computed produces a discontinuous creaseness measure. The same problem arises in 3-d with its straightforward extension and with other related creaseness measures. In this paper, we first present an alternative method of computing the level curve curvature that avoids the discontinuities. Next, we propose the Mean curvature of the level surfaces as creaseness measure of 3-d images, computed by the same method. Finally, we propose a natural extension of our first alternative method in order to enhance the creaseness measure.

Softwarization of Future Networks and Services -Programmable Enabled Networks as Next Generation Software Defined Networks

The Software Defined Networks (SDNs) and Network Functions Virtualisation (NFVs), as recent separate research and development trends have the roots in programmable / active network technologies and standards developed a decade ago. In particular, they are associated with the decoupling of forwarding from control and hardware from networking software, using open interfaces to connectivity resources. The next phase of R&D would involve novel integration and use of all connectivity, storage and processing resources under new management interacting with control systems for provisioning of on-demand networking and services with continuous update of features. This brings into focus a relatively new and key topics for the next decade: what and how to create the conditions for effective and continuous updating and changing the networking functions without reinventing each time architectural aspects and related components (e.g. Softwarization of Future Networks and Services or Programmable Enabled Networks). This paper presents motivation, architecture and the key challenges in realising such programmable enabled networks as the next generation Software Defined Networks focusing on its management plane.