Roberto Riggio

VeRTIGO: Network Virtualization and Beyond

In this paper we present Vertigo (Virtual Topologies Generalization in OpenFlow networks), a Software-defined networking platform designed for network virtualization. Based on the OpenFlow original network slicing system Flow Visor, the Vertigo platform aims at covering all flavors of network virtualization: in particular, it is able to expose a simple abstract node on one extreme, and to deliver a logically fully connected network at the very opposite end. In this work, we first introduce the Vertigo system architecture and its design choices, then we report on a prototypical implementation deployed over an OpenFlow-enabled test bed. Experimental results show that Vertigo can deliver flexible and reliable network virtualization services to a wide range of use cases in spite of failure and/or congestion at the underlying physical network.

Programming Abstractions for Software-Defined Wireless Networks

Software-Defined Networking (SDN) has received, in the last years, significant interest from the academic and the industrial communities alike. The decoupled control and data planes found in an SDN allows for logically centralized intelligence in the control plane and generalized network hardware in the data plane. Although the current SDN ecosystem provides a rich support for wired packet-switched networks, the same cannot be said for wireless networks where specific radio data-plane abstractions, controllers, and programming primitives are still yet to be established. In this work, we present a set of programming abstractions modeling the fundamental aspects of a wireless network, namely state management, resource provisioning, network monitoring, and network reconfiguration. The proposed abstractions hide away the implementation details of the underlying wireless technology providing programmers with expressive tools to control the state of the network. We also present a Software-Defined Radio Access Network Controller for Enterprise WLANs and a Python--based Software Development Kit implementing the proposed abstractions. Finally, we experimentally evaluate the usefulness, efficiency and flexibility of the platform over a real 802.11-based WLAN.

Analysing the energy consumption behaviour of WiFi networks

The continuous increase in the energy production cost, together with environmental sustainability issues, is leading research communities, governments and industries to focus their efforts on a reduction of the global CO2 footprint. Information and communication technologies, which represent the nervous system of the globalized economy and society, account for a significant percentage of the overall global energy consumption. While a number of solutions have been proposed to build new, energy-aware and ‘green’ communication infrastructures, little attention has been devoted to measuring the actual impact through real-world measurements. In this paper, we focus on wireless access networks, and aim at experimentally investigating the fundamental relationship between traffic and power consumption for a typical wireless LAN based on the IEEE 802.11g standard. The insight obtained through the measurements can be used to develop reliable and realistic energy consumption models, on top of which novel energy aware protocols and algorithms can be designed and developed.

A traffic aggregation and differentiation scheme for enhanced QoS in IEEE 802.11-based Wireless Mesh Networks

Wireless Mesh Networks are currently emerging as a promising paradigm for broadband ubiquitous Internet access. However, their distributed nature raises many challenges when facing the increasing demand for multimedia applications, which require a tight control over the systems available resources. In this paper, we address such issue by introducing a mechanism combining service differentiation and packet aggregation in IEEE 802.11-based WMNs. Our architecture does not require any modification to the IEEE 802.11 MAC and can be readily deployed exploiting off-the-shelf hardware. The proposed solution has been implemented as an extension to the MIT Roofnet platform. Measurements run over a WiFi testbed show a large gain in the voice capacity attained. The source code, released under the BSD License, is made available to the research community.

Hardware and software solutions for wireless mesh network testbeds

Wireless mesh networks are currently emerging as a promising technology for broadband ubiquitous networking. Typical applications range from home broadband Internet access and community networking to wireless metropolitan area networks. Many companies are currently active in this field with proprietary solutions mostly based on the IEEE 802.11 family of standards. At the same time, there are considerable efforts in academia aiming to provide real-world prototypes and testbeds based on open source software and off-the-shelf technologies. This article provides a survey on the most relevant hardware and software platforms that can be used to build a WMN testbed.

Interference and traffic aware channel assignment in WiFi-based wireless mesh networks

Wireless mesh networks (WMN) typically employ mesh routers that are equipped with multiple radio interfaces to improve network capacity. The key aspect is to cleverly assign different channels (i.e., frequency bands) to each radio interface to form a WMN with minimum interference. The channel assignment must obey the constraints that the number of different channels assigned to a mesh router is at most the number of interfaces on the router, and the resultant mesh network is connected. This problem is known to be NP-hard. In this paper we propose a hybrid, interference and traffic aware channel assignment (ITACA) scheme that achieves good multi-hop path performance between every node and the designated gateway nodes in a multi-radio WMN network. ITACA addresses the scalability issue by routing traffic over low-interference, high-capacity links and by assigning operating channels in such a way to reduce both intra-flow and inter-flow interference. The proposed solution has been evaluated by means of both simulations and by implementing it over a real-world WMN testbed. Results demonstrate the validity of the proposed approach with performance increase as high as 111%.

V-Cell: Going beyond the cell abstraction in 5G mobile networks

Past years have witnessed the surge of mobile broadband Internet traffic due to the broad adoption of a number of major technical advances in new wireless technologies and consumer electronics. In this respect, mobile networks have greatly increased their availability to meet the exponentially growing capacity demand of modern mobile applications and services. The upcoming scenario in the near future lays down the possibility of a continuum of communications thanks also to the deployment of so called small cells. Conventional cellular networks and the small cells will form the foundation of this pervasive communication system. Therefore, future wireless systems must carry the necessary scalability and seamless operation to accommodate the users and integrate the macro cells and small cells together. In this work we propose the V-Cell concept and architecture. V-Cell is potentially leading to a paradigm shift when approaching the system designs that allows to overcome most of the limitations of physical layer techniques in conventional wireless networks.

Measuring the Quality of VoIP Traffic on a WiMAX Testbed

The large coverage of the IEEE 802.16 standard, widely known as WiMAX, represents a key advantage compared to several first mile solutions proposed so far, while ensuring a rather inexpensive equipment at the subscriber side. The IEEE 802.16 standard, in practice, promises to be a flexible solution especially where cabling is not a viable choice, or as an alternative to customary leased lines. Nevertheless, modern requirements to wireless connectivity include mandatory QoS guarantees for a wide set of real-time applications, and this is the case of the ever growing trend of VoIP calls. To this aim, WiMAX supports natively real-time traffic. In this paper, we report the results of a set of measurements performed on the field on a WiMAX Alvarion testbed, located in Turin, Italy. We fed the system with synthetic VoIP traffic, real-time guaranteed, competing with concurrent best effort traffic. We obtained E-model figures, thus characterizing the operation intervals of the system, depending on the codec source and on the number of calls.

Virtual network functions orchestration in enterprise WLANs

Network Function Virtualization (NFV) has recently been proposed as a tool to optimize the deployment of network functions by shifting the processing from dedicated middleboxes to general purpose and inexpensive hardware platforms. In this paper, we propose a novel NFV-based management and orchestration framework for enterprise WLANs. Our framework is compatible with the ETSI NFV architecture and leverages on hybrid nodes combining the forwarding capabilities of a programmable switch with the storage/computational capabilities of a server. We propose an algorithm for Virtual Network Function placement which optimizes the functions deployment according to application level constraints. A proof-of-concept implementation of the proposed framework and a preliminary performance evaluation of selected VNFs are also presented.

Introducing Mobile Edge Computing Capabilities through Distributed 5G Cloud Enabled Small Cells

Current trends in broadband mobile networks are addressed towards the placement of different capabilities at the edge of the mobile network in a centralised way. On one hand, the split of the eNB between baseband processing units and remote radio headers makes it possible to process some of the protocols in centralised premises, likely with virtualised resources. On the other hand, mobile edge computing makes use of processing and storage capabilities close to the air interface in order to deploy optimised services with minimum delay. The confluence of both trends is a hot topic in the definition of future 5G networks. The full centralisation of both technologies in cloud data centres imposes stringent requirements to the fronthaul connections in terms of throughput and latency. Therefore, all those cells with limited network access would not be able to offer these types of services. This paper proposes a solution for these cases, based on the placement of processing and storage capabilities close to the remote units, which is especially well suited for the deployment of clusters of small cells. The proposed cloud-enabled small cells include a highly efficient microserver with a limited set of virtualised resources offered to the cluster of small cells. As a result, a light data centre is created and commonly used for deploying centralised eNB and mobile edge computing functionalities. The paper covers the proposed architecture, with special focus on the integration of both aspects, and possible scenarios of application.