Papers by Renato Lo Cigno
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Wireless Community Networks (WCNs) are bottom-up broadband networks empowering people with their ... more Wireless Community Networks (WCNs) are bottom-up broadband networks empowering people with their on-line communication means. Too often, however, services tailored for their characteristics are missing, with the consequence that they have worse performance than what they could. We present here an adaptation of an Open Source P2P live streaming platform that works efficiently, and with good application-level quality, over WCNs. WCNs links are usually symmetric, or at least asymmetry is not by design as it is in ADSL, and a WCN topology is local and normally flat (contrary to the the global Internet), so that the P2P overlay used for video distribution can be adapted to the underlaying network characteristics. We exploit this observation to derive over- lay building strategies that make use of cross-layer information to reduce the impact of the P2P streaming on the WCN while maintaining good application performance. We experiment with a real application in real WCN nodes, both in the Community-Lab provided by the CONFINE EU Project and within an emulation framework based on Mininet, where we can build larger topologies and interact more efficiently with the mesh underlay, which is unfortunately not accessible in Community-Lab. The results show that, with the overlay building strategies proposed, the P2P streaming applications can reduce the load on the WCN to about one half, also equalizing the load on links. At the same time the delivery rate and delay of video chunks are practically unaffected.
Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998
Recently, communication networks, and ATM (asynchronous transfer mode) in particular, received a ... more Recently, communication networks, and ATM (asynchronous transfer mode) in particular, received a growing attention in the control community. Several problems have been studied from the control system point of view, including traffic identification with optimization algorithms, adaptive bandwidth estimation, decentralized and robust flow control. In this paper, we continue this line of research studying the problem of robustly controlling the
2012 9th Annual Conference on Wireless On-Demand Network Systems and Services (WONS), 2012
The goal of this work is to highlight and explain the limitations of traditional physical channel... more The goal of this work is to highlight and explain the limitations of traditional physical channel models used in network simulators for wireless LANs, with particular reference to VANETs, where these limitations may jeopardize the validity of results, specially for safety applications. The fundamental tradeoff is between simulation time and realism. Indeed, a simulator should provide realistic results as fast as possible, even if several nodes (i.e., hundreds) are considered. Our final goal, beyond this initial contribution, is the development of a stochastic channel model which improves reliability of simulations while increasing computational complexity only marginally. The design of our model is based on the representation of the packet decoding procedure as a Markov Decision (Stochastic) Process (MDP), thus avoiding the computational complexity of the simulation of the entire transmission -propagation -decoding chain bitby-bit, which can surely provide enough accuracy, but at the price of unacceptable computational (and model) complexity. The paper identifies the key phenomena such as preamble detection, central-frequency misalignment, channel captures, vehicles relative speed, that represent the 'state' of the MDP modeling the transmission chain, and propose an MDP structure to exploit it. The focus is on 802.11p and OFDM-based PHY layers, but the model is extensible to other transmission techniques easily. The design is tailored for implementation in ns-3, albeit the modeling principle is general and suitable for every event-driven simulator.
Proceedings - IEEE INFOCOM, 2009
Recently several studies have been made on reducing overall network traffic by localizing P2P tra... more Recently several studies have been made on reducing overall network traffic by localizing P2P traffic. Interestingly, real world measurements show that these localization techniques often do not bring performance advantages to the P2P user, only to the underlying network by reducing average layer 3 hop count of individual transmissions. In this paper, we study the effects of localized traffic patterns on end-user performance, in the specific case of P2P-TV traffic. We find that, without assuming excess local networking resources (such as higher bandwidth), localization reduces end-user performance considerably due to the resulting clustered overlay structure. We investigate (though simulation) the amount of random overlay edges and the amount of local bandwidth surplus that can mitigate this negative effect of preferring local connections.
Software: Practice and Experience, 2012
IEEE/ACM Transactions on Networking, 2002
Research on congestion-control algorithms has traditionally focused more on performance than on r... more Research on congestion-control algorithms has traditionally focused more on performance than on robustness of the closed-loop system to changes in network conditions. As the performance of the control loop is strictly connected with the quality of service, these systems are natural candidates to be approached by the optimal control theory. Unfortunately, this approach may fail in the presence of transmission delay variations, which are unavoidable in telecommunication systems.
European Transactions on Telecommunications, 2002
Congestion in the Internet is becoming a major cause of network performance degradation. The Gene... more Congestion in the Internet is becoming a major cause of network performance degradation. The Generalized Window Advertising (GWA) scheme proposed in this paper is a new approach for enhancing the congestion control properties of TCP. GWA requires only minor modi cations to the existing protocol stack and is completely backward compatible, allowing GWA-hosts to interact with non-GWA hosts without modi cations.
EURASIP Journal on Wireless Communications and Networking, 2013
ABSTRACT Firewalls are network devices dedicated to analyzing and filtering the traffic in order ... more ABSTRACT Firewalls are network devices dedicated to analyzing and filtering the traffic in order to separate network segments with different levels of trust. Generally, they are placed on the network perimeter and are used to separate the intranet from the Internet. Firewalls are used to forbid some protocols, to shape the bandwidth resources, and to perform deep packet inspection in order to spot malicious or unauthorized contents passing through the network. In a wireless multihop network, the concept of perimeter is hard to identify and the firewall function must be implemented on every node together with routing. But when the network size grows, the rule-set used to configure the firewall may grow accordingly and introduce latencies and instabilities for the low-power mesh nodes. We propose a novel concept of firewall in which every node filters the traffic only with a portion of the whole rule-set in order to reduce its computational burden. Even if at each hop we commit some errors, we show that the filtering efficiency measured for the whole network can achieve the desired precision, with a positive effect on the available network resources. This approach is different from the protection of a space behind a wall: we use the term waterwall to indicate a distributed and homogeneous filtering function spread among all the nodes in the network.
Performance Modelling and Evaluation of ATM Networks, 1995
Lecture Notes in Computer Science, 1994
CLASS is a software package for the simulation of connectionless services in ATM networks, such a... more CLASS is a software package for the simulation of connectionless services in ATM networks, such as ATM LANs, or long distance ATM computer networks. CLASS was developed in standard C language in order to achieve good portability, and was implemented aiming at maximum CPU efficiency, in order to mitigate the impact of the CPU time requirements typical of the simulation
Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213), 2001
This paper presents a new analytical model for the estimation of the performance of TCP connectio... more This paper presents a new analytical model for the estimation of the performance of TCP connections. The model is based on the description of the behavior of TCP-Tahoe in terms of a closed queueing network, whose solution can be obtained with very low cost, even when the number of TCP connections that interact over the underlying IP network is huge. The protocol model can be very accurate, deriving directly from the finite state machine description of the protocol. The assessment of the accuracy of the analytical model is based on comparisons against detailed simulation experiments developed with the ns-2 package. Numerical results indicate that the proposed closed queueing network model provides extremely accurate performance estimates, not only for average values, but even for distributions, in the case of the classical single-bottleneck configuration, as well as in more complex networking setups.
Lecture Notes in Computer Science, 2003
In this paper we develop an approximate colored GSPN model to study the behavior of short-lived T... more In this paper we develop an approximate colored GSPN model to study the behavior of short-lived TCP connections sharing a common portion of the Internet for the transfer of TCP segments. The CGSPN model is then paired with a very simple approximate model of the IP network used by TCP connections, and the two models are jointly solved through an iterative procedure. The combined model allows the investigation of the Quality of Service (QoS) tradeoffs between network cost and network parameters, thus allowing a QoS-based design, dimensioning and planning of portions of the Internet. The QoS predictions generated by the model are validated against results of detailed simulation experiments in a realistic networking scenario, proving that the proposed modeling approach is very accurate.
Lecture Notes in Computer Science, 2007
This paper addresses the study of fundamental properties of stream-based content distribution ser... more This paper addresses the study of fundamental properties of stream-based content distribution services. We assume the presence of an overlay network with limited connectivity degree, and we develop a mathematical model that captures the essential properties of overlaybased streaming protocols and systems. The methodology is based on graph theory and models the streaming system as a stochastic process, whose characteristics are related to the streaming protocol. The model can capture the transient behavior of the distribution graphs, i.e., the evolution of the structure over time. Results show that mesh-based architectures are able to provide bounds on the receiving delay and maintain rate fluctuations due to system dynamics very low. ⋆ This work was partially supported in Trento by the Italian MIUR PRIN project PROFILES (http://profiles.dit.unitn.it)
Lecture Notes in Computer Science, 2005
This paper presents a method for the performance evaluation of multimedia streaming applications ... more This paper presents a method for the performance evaluation of multimedia streaming applications on IP network interfaces with differentiated scheduling. Streaming applications are characterized by the emission of data packets at constant intervals, changing during the connection lifetime, hence a single source can be effectively modeled by an MMDP. We propose an MMDP/D/1/K model to represent the aggregate arrival process at the network interface, assuming that multimedia packet dimensions are approximately constant. A method for solving the above queuing system providing upper and lower bounds to the packet loss rate is presented and results for realistic VoIP applications are discussed and validated against accurate event-driven simulations showing the efficiency and accuracy of the method. §
Lecture Notes in Computer Science, 2003
WILMA (Wireless Internet and Location Management Architecture) is an on-going research project ba... more WILMA (Wireless Internet and Location Management Architecture) is an on-going research project based in Trento, Italy, whose aim is the study of the management of 802.11based HotSpot Networks and the value added services that can be provided through such an infrastructure. The ...
1998 1st IEEE International Conference on ATM. ICATM'98, 1998
... (b) Dipartimento di Elettronica, Politecnico di Torino Corso Duca degli Abruzzi 24,10129 Tori... more ... (b) Dipartimento di Elettronica, Politecnico di Torino Corso Duca degli Abruzzi 24,10129 Torino tel: +39-11-564-4076, fax: +39-11-564-4099 e-mid: { neri, locigno, leonardi, michela} @polito.it ... Note that protection against errors is much more robust on the downli.uk channel. Tab. ...
IEEE ATM '97 Workshop Proceedings (Cat. No.97TH8316), 1997
The provision of mobility services in ATM networks requires the definition of handover procedures... more The provision of mobility services in ATM networks requires the definition of handover procedures that allow the proper re-routing of connections to and from the mobile terminal while it roams through the network. If QoS requirements are to be met, the handover procedure must avoid cell loss and misordering; as a consequence, cells must be buffered during the handover. This
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Papers by Renato Lo Cigno