Simone Molendini

Experience-driven selective scan for 802.11 networks

The current use of the IEEE 802.11 protocol does not fully meet the full requirements of real-time applications. During the handoff period the STA cannot receive traffic and the quality of these applications is therefore reduced. A significant cause of this latency is that the STA normally scans all possible channels before synchronizing one of them. Considering that normally several channels are empty and that the 802.11 infrastructure architecture provides for fixed access points, it is possible to reduce the overall latency by reducing the number of channels to be scanned. In this paper we show an algorithm for selectively scanning just one probable channel. If such a channel is not available, the algorithm selects a second candidate until it scans all channels. These probabilities depend on the movements inside that LAN of previous STA. We show motivations and specifications of the algorithm

Design of the satellite reliable distribution protocol (SRDP)

In this paper we propose and discuss the satellite reliable distribution protocol (SRDP), a novel protocol designed for satellite-based data broadcasting. This protocol aims to transmit reliable multicast information of Internet applications in an efficient and scalable way. We discuss the requirements of the protocol analysing the main issues given by the possible use in the global Internet. The solution we present is based on a cooperation between receivers that improve the overall behaviour. The performances of the protocol are evaluated by the mean of ns2 - network simulator.

CHARMS: Cooperative hybrid architecture for relaying multicast satellite streams to sites without a satellite receiver

This paper describes an architecture dedicated to the terrestrial relaying of a real-time IP multicast audio-video stream broadcasted by a satellite. Such relaying is performed by nodes equipped with both a satellite receiver and a terrestrial Internet link. The stream is requested and obtained by sites that are not equipped with satellite receiving hardware but are nonetheless willing to receive it. By exploiting the properties of satellite transmission and adopting an hybrid satellite/terrestrial, multicast/unicast approach the described architecture allows to overcome the restrictions suffered by multicast traffic in the global Internet, allowing it to scale easily across autonomous systems.

The Campus Satellitare del Salento: a scalable and transparent e-learning application

The CSS (Campus Satellitare del Salento) is an e-learning application developed by the University of Lecce (in Italy) that integrates live, interactive and on-demand services over not only the Internet but also the satellite infrastructure. This paper presents the CSS realized as a solution to face the problem of guiding large classrooms of students and of developing didactic models very transparent like traditional ones. As such, CSS gains scalability making use of a satellite data network and of a remote monitoring tool. Moreover, transparency is obtained using screen-recording and open learning environment in which the learning material (multimedia data) is organized into an easy and a modular structure. Even though these solutions have been adopted to solve a local problem, it seems to have a wide range of potential implementations

SRDP-Sign: a reliable multicast protocol for signaling

In this paper we present SRDP-sign, a reliable multicast protocol designed to guarantee the reliable transmission of short messages via satellite as an extension of satellite reliable distribution protocol (SRDP). The uses of this protocol range from sending short text messages to transmitting information used for the improvement of networkspsila performances. The innovation of this protocol is that it has a high degree of scalability, reduced communication with receivers and fast delivery. In this paper we show the operations of the protocol, the underlying algorithms and analyse the protocolpsilas behavior.

Reliable Key Distribution for Secure Multicast by SRDP-Sign

Security is an important concern in todays networking and particularly in satellite communication, where eavesdropping and active intrusion is much easier than in terrestrial fixed or mobile networks because of the broadcast nature of satellites. Many applications require the security feature of data confidentiality; in order to offer such capability, encryption keys must be constantly changed upon a membership change. If the keys are sent via multicast, that it is particularly useful for large groups, reliable multicast is required. In this paper we propose an efficient, reliable and multicast distribution of the encryption keys with SRDP-Sign (Satellite Reliable Distribution Protocol for Signaling). We guarantee reliability for all the receivers with a high degree of scalability. Total reliability error and the overall latency in the key distribution will be evaluated.

Fast Re-establishment of QoS with NSIS Protocols in Mobile Networks

Re-establishment of the QoS after a Mobile Node handover must be done as quickly as possible in order to reduce degradation or interruption of QoS, especially when realtime applications are used. We propose a Semi-Proactive procedure for a faster QoS re-establishment in environments where there are Mobile Nodes. The basic functionality of this procedure is to perform as many operation as possible before the handover (in a proactive manner). Resources are reserved after the handover on the effective new data path in order to avoid their waste. Moreover, we propose to buffer at the Candidate CRossover Node - CCRN (an intermediate node on end-to-end data path) the packets directed to the Mobile Node during the handover. In this way the total QoS re-establishment time is reduced. This buffering also guarantees the same QoS treatment of both the buffered and the non-buffered packets.

Network Management via Satellite

Satellite links already provide Internet for multicast transmissions over large areas. It would be very useful to extend the traditional use of satellite applications to the management of networks. In this paper we show the evolution of the satellite platform. We then report a novel protocol, the centralized signaling protocol (CSP), which manages signalling messages to routers in terrestrial networks. Extensions to a reliable multicast protocol for transporting CSP via narrowband and long-duration satellite sessions are discussed. Several examples that illustrate the usage of the CSP are also provided

GridSAT: Grid enabled Satellite Architecture for Reliable Transmissions

The paper defines an architecture that uses the satellite as a communication medium for efficient and reliable large file distribution across WANs, and so disseminate large files at multiple receivers in geographically dispersed grids, exploiting e SRDP protocol

Improvement of performance in MPLS domains by using caching and aggregation of CR-LSP

Constraint-based routing (CR-LDP) extends the features of MPLS Label Distribution Protocol (LDP) working in conjunction with a wide variety of QoS scenarios and services including IP differentiated services, integrated services, traffic engineering, Asynchronous Transfer Mode (ATM) service classes and frame relay. When a large number of CR-LSPs are required a lot of CR-LDP signalling is needed: this paper proposes two techniques — caching and aggregation — to reduce the number of CR-LDP messages by dynamically increasing the number of flows served by each single CR-LSP. The results of a simulation are also used to discuss the performance of such mechanisms.