Claudio Pisa

Wireless Mesh Software Defined Networks (wmSDN)

In this paper we propose to integrate Software Defined Networking (SDN) principles in Wireless Mesh Networks (WMN) formed by OpenFlow switches. The use of a centralized network controller and the ability to setup arbitrary paths for data flows make SDN a handy tool to deploy fine-grained traffic engineering algorithms in WMNs. However, centralized control may be harmful in multi-hop radio networks formed by commodity devices (e.g. Wireless Community Networks), in which node isolation and network fragmentation are not rare events. To exploit the pros and mitigate the cons, our framework uses the traditional OpenFlow centralized controller to engineer the routing of data traffic, while it uses a distributed controller based on OLSR to route: i) OpenFlow control traffic, ii) data traffic, in case of central controller failure. We implemented and tested our Wireless Mesh Software Defined Network (wmSDN) showing its applicability to a traffic engineering use-case, in which the controller logic balances outgoing traffic among the Internet gateways of the mesh. Albeit simple, this use case allows showing a possible usage of SDN that improves user performance with respect to the case of a traditional mesh with IP forwarding and OLSR routing. The wmSDN software toolkit is formed by Open vSwitch, POX controller, OLSR daemon and our own Bash and Python scripts. The tests have been carried out in an emulation environment based on Linux Containers, NS3 and CORE tools.

SVEF: an open-source experimental evaluation framework for H.264 scalable video streaming

This paper describes the H.264 Scalable Video coding streaming Evaluation Framework (SVEF). This is the first open-source framework for experimental assessment of H.264 Scalable Video Coding (SVC) delivery over real networks. Effectively adapting of the transport of an H.264 SVC stream to time-varying, bandwidth constrained, and loss prone networks is an important research area. However, very little experimental work has been performed due to the unavailability of real-time H.264 SVC players, the limitations of existing decoding software libraries when challenged with network-imparied received SVC streams (e.g., affected by random loss of Network Abstraction Layer Units - NALUs), and the lack of solutions for SVC streaming support. SVEF overcomes these issues by developing missing components and by integrating them in a hybrid online/offline experimental framework. We believe SVEF will be of significant help to the research community interested in experimentally benchmarking their own proposed SVC adaptation approaches and delivery mechanisms. As a proof-of-concept of SVEF, we provide the experimental performance evaluation of an SVC cross-layer in-network scheduler in a Wireless LAN hot spot scenario.

Modeling multipath forwarding strategies in Information Centric Networks

A content can be replicated in more than one node in Information Centric Networks (ICNs). Thus, more than one path can be followed to reach the same content, and it is necessary to decide the interface(s) to be selected in every network node to forward content requests towards such multiple content containers. A multipath forwarding strategy defines how to perform this choice. We propose a general analytical model to evaluate the effect of multipath forwarding strategies on the performance of an ICN content delivery, whose congestion control follows a receiver driven, path-unaware, loss-based AIMD scheme. We use the model to understand the behavior of ICN multipath forwarding strategies proposed in the literature so far, and to devise and evaluate a novel strategy.

Cross-layer H.264 scalable video downstream delivery over WLANs

Thanks to its in-network drop-based adaptation capabilities, H.264 Scalable Video Coding is perceived as an effective approach for delivering video over networks characterized by sudden large bandwidth fluctuations, such as Wireless LANs. Performance may be boosted by the adoption of application-aware/cross-layer schedulers devised to intelligently drop video data units (NALUs), so that i) decoding dependencies are preserved, and ii) the quality perceived by the end users is maximized. In this paper, we provide a theoretical formulation of a QoE utility-optimal cross-layer scheduling problem for H.264 SVC downlink delivery over WLANs. We show that, because of the unique characteristics of the WLAN MAC operation, this problem significantly differs from related approaches proposed for scheduled wireless technologies, especially when the WLAN carries background traffic in the uplink direction. From these theoretical insights, we derive, design, implement and experimentally assess a simple practical scheduling algorithm, whose performance is very close to the optimal solution.

Application-aware H.264 Scalable Video Coding delivery over Wireless LAN: Experimental assessment

This paper is among the first works to document experimental results for application-aware H.264 Scalable Video Coding (SVC) support over Wireless LANs. Application-aware support is achieved by introducing a bandwidth throttling device, called Virtual BottleNeck (VBN), before the WLAN Access Point. Throttling is set to a bandwidth slightly smaller than the actual WLAN capacity (either known or estimated), so that all packet/frame losses occur inside the VBN. Here, loss events are controlled by a scheduling mechanism devised to operate with information taken from the H.264 Network Abstraction Layer Units (NALUs). Despite its relative simplicity, the implemented scheduler exhibits effective video adaptation performance and close to optimal bandwidth efficiency. Setting up the trial was not trivial due to the lack of suitable publicly available tools. We filled this gap by implementing and integrating several separate software modules, e.g., streaming server, NALU dependency filtering, video frame concealment, etc. As a final result, the experimental trial supports the full delivery chain for an SVC stream with the only limitation of an off-line stream conversion for play-out and Peak Signal-to-Noise Ratio (PSNR) measurement purposes, due to the unavailability of real time SVC players.

On the practical applicability of SDN research

Software-Defined Networking (SDN) is a de-facto established approach that separates the packet switching functions of a device from its operational logic, which is controlled by a piece of software. Due to its potential for realizing new network architectures and services, a whole thread of scientific literature is devoted to SDN and its most adopted incarnation, OpenFlow. However, limited attention has been put in verifying the viability of the proposed approaches on currently available hardware. We address this deficiency through the following contributions: i) a critical review of the literature about SDN in terms of applicability issues stemming from publicly documented limitations of OpenFlow implementations; ii) a methodology for verifying the support of SDN-related functions in a network device, comprising an OpenFlow compliance test as well as custom targeted tests; iii) an application of the methodology to devices from 7 different vendors, unveiling extensive anomalous behaviors affecting even the most basic features; iv) a discussion of this outcome in terms of relevance of the discovered anomalies and of their implications on the applicability of state-of-the-art contributions on SDN. Besides taking a snapshot of the viability of research results, with this paper we intend to highlight aspects that operators should consider when picking SDN devices.

WI-FAB: attribute-based WLAN access control, without pre-shared keys and backend infrastructures

Two mainstream techniques are traditionally used to authorize access to a WiFi network. Small scale networks usually rely on the offline distribution of a WPA/WPA2 static pre-shared secret key (PSK); security hence relies on the fact that this PSK is not leaked by end user, and is not disclosed via dictionary or brute-force attacks. On the other side, Enterprise and large scale networks typically employ online authorization using an 802.1X-based authentication service leveraging a backend online infrastructure (e.g. Radius servers/proxies). In this work, we propose a new mechanism which does not require neither online operation nor backend access control infrastructure, but which does not force us to rely on a static pre-shared secret key. The idea is very simple, yet effective: directly broadcast in the WLAN beacons an encrypted version of the secret key required to access the WLAN network, so that only the users which possess suitable authorization credentials can decrypt and use it. This proposed approach clearly decouples the management of authorization credentials, issued offline to the authorized end users, from the actual secret key used in the WLAN network, which can thus be in principle changed at each new users access. The solution described in the paper relies on attribute-based encryption, and is designed to be compatible with WPA2 and deployable within standard 802.11 management frames. Since no user identification is required (access control is based on attributes rather than on the user identity), the proposed approach further improves privacy. We demonstrate the feasibility of the proposed solution via a concrete implementation in Linux-based devices and via relevant testing in a real-world experimental setup.

Performance evaluation and tuning of Virtual Infrastructure Managers for (Micro) Virtual Network Functions

Virtualized Network Functions (VNFs) are emerging as the keystone of 5G network architectures: flexibility, agility, fast instantiation times, consolidation, Commercial Off The Shelf (COTS) hardware support and significant cost savings are fundamental for meeting the requirements of the new generation of mobile networks. In this paper we deal with the management of the virtual computing resources for the execution of Micro VNFs. This functionality is performed by the Virtual Infrastructure Manager (VIM) in the NFV MANagement and Orchestration (MANO) reference architecture.We discuss the VIM instantiation process and propose a generic reference model, starting from the analysis of two Open Source VIMs, namely OpenStack Nova and Nomad. We implemented a tuned version of the VIMs with the specific goal of reducing the duration of the instantiation process. We realized a performance comparison of the two VIMs, both considering the plain and the tuned versions. The tuned VIMs and the performance evaluation tools that we have employed are provided openly and can be downloaded from our repository.

On the feasibility of attribute-based encryption for WLAN access control

User authentication at Wi-Fi Access Points (APs) is becoming an important issue. Wi-Fi APs are indeed ubiquitous, but existing authentication methods such as WPA/WPA2 static pre-shared secret key (PSK), or 802.1X-based online authentication services (e.g., RADIUS servers/proxies) have their theoretical or practical limitations. In a previous work, we proposed WI-FAB, a new authentication mechanism which neither requires online backend access control infrastructure, nor relies on a static pre-shared secret key. In this paper, we extend WI-FAB by removing the need for having a central authority for user authentication and credential issuing. Our main contribution is twofold: (i) adopting decentralized multi-authority CP-ABE, we support the users who have authentication/authorization credentials from multiple authorities. We decouple the user credentials issuing from the management of the WPA2-PSK, so that neither the credential issuing authority can track the users, nor the AP can access the real identity of the users. Considering an extensive attack model, we show that the proposed approach is secure and preserves the privacy of the users. (ii) We provide a real-world implementation of the proposed approach on off-the-shelf embedded hardware to demonstrate its feasibility and efficiency.

RDCL 3D, a model agnostic web framework for the design and composition of NFV services

We present RDCL 3D, a “model agnostic” web framework for the design and composition of NFV services and components. The framework allows editing and validating the descriptors of services and components both textually and graphically and supports the interaction with external orchestrators or with deployment and execution environments. RDCL 3D is open source and designed with a modular approach, allowing developers to “plug in” the support for new models. We describe several advances with respect to the NFV state of the art, which have been implemented with RDCL 3D. We have integrated in the platform the latest ETSI NFV ISG model specifications for which no parsers/validators were available. We have also included in the platform the support for OASIS TOSCA models, reusing existing parsers. Then we have considered the modelling of components in a modular software router (Click), which goes beyond the traditional scope of NFV. We have further developed this approach by combining traditional NFV components (Virtual Network Functions) and Click elements in a single model. Finally, we have considered the support of this solution using the Unikernels virtualization technology.