Mario Baldi

Exploiting Code Mobility in Decentralized and Flexible Network Management

Network management is gaining increasing importance due to the pervasiveness of computer networks. Nevertheless, mainstream approaches to network management are presently limited by centralized management strategies and poor flexibility—a consequence of their rigid client-server architecture. In this paper we analyze how to overcome these problems by new design paradigms and technologies encompassing the capability to relocate dynamically the components of a distributed application. We evaluate the opportunities offered by this approach and provide feasibility considerations, also discussing a few interim architectural solutions adopted in our on-going implementation work.

Evaluating the tradeoffs of mobile code design paradigms in network management applications

The question of whether technologies supporting mobile code are bringing significant benefits to the design and implementation of distributed applications is still an open one. Even more difficult is to identify precisely under which conditions a design exploiting mobile code is preferable over a traditional one. In this work, we present an in-depth evaluation of several mobile code design paradigms against the traditional client-server architecture, within the application domain of network management. The evaluation is centered around a quantitative model, which is used to determine precisely the conditions for the selection of a design paradigm minimizing the network traffic related to management.

End-to-end delay analysis of videoconferencing over packet-switched networks

Videoconferencing is an important global application-it enables people around the globe to interact when distance separates them. In order for the participants in a videoconference call to interact naturally, the end-to-end delay should be below human perception; even though an objective and unique figure cannot be set, 100 ms is widely recognized as the desired one-way delay requirement for interaction. Since the global propagation delay can be about 100 ms, the actual end-to-end delay budget available to the system designer (excluding propagation delay) can be no more than 10 ms. We identify the components of the end-to-end delay in various configurations with the objective of understanding how it can be kept below the desired 10-ms bound. We analyze these components step-by-step through six system configurations obtained by combining three generic network architectures with two video encoding schemes. We study the transmission of raw video and variable bit rate (VBR) MPEG video encoding over (1) circuit switching; (2) synchronous packet switching; and (3) asynchronous packet switching. In addition, we show that constant bit rate (CBR) MPEG encoding delivers unacceptable delay-on the order of the group of pictures (GOP) time interval-when maximizing the quality for static scenes. This study aims at showing that having a global common time reference, together with time-driven priority (TDP) and VBR MPEG video encoding, provides adequate end-to-end delay, which is (1) below 10 ms; (2) independent of the network instant load; and (3) independent of the connection rate. The resulting end-to-end delay (excluding propagation delay) can be smaller than the video frame period, which is better than what can be obtained with circuit switching.

A framework for rapid development and portable execution of packet-handling applications

This paper presents a framework that enables the execution of packet-handling applications (such as sniffers, firewalls, intrusion detectors, etc.) on different hardware platforms. This framework is centered on the NetVM - a novel, portable, and efficient virtual processor targeted for packet-based processing - and the NetPDL - a language dissociating applications from protocol specifications. In addition, a high-level programming language that enables rapid development of packet-based applications is presented

Fractional Lambda Switching Principles of Operation and Performance Issues

This article introduces fractional lambda (λ) switching (FλS) and studies its blocking issues. FλS uses a global common time reference (CTR) for implementing pipeline forwarding (PF) inside the network. A global CTR is conveniently realized with the UTC (coordinated universal time) standard. Resource reservation over an FλS network requires a schedule. As in other scheduling cases, a call may not be accepted, even though there is enough capacity, because the schedule is not available—the call is then considered blocked. This work studies the probability of call blocking as a function of link utilization. The results show that (especially if multiple-wavelength division multiplexing channels are deployed on optical links between fractional λ switches) high-link utilization can be achieved with negligible call blocking, even when the switching fabric is a Banyan network.

NetPDL: an extensible XML-based language for packet header description

Although several applications need to know the format of network packets to perform their tasks, till now, each application uses its own packet description database. This paper addresses this problem by proposing the NetPDL, an XML-based language for describing packet headers, which has the potential of enabling the realization of a common, application-independent protocol description database that can be shared among several applications. Further, common functionalities related to the protocol database can be implemented in a library, which can be a basic building block for implementing networking applications.

Time-Driven Access and Forwarding for Industrial Wireless Multihop Networks

The deployment of wireless technologies in industrial networks is very promising mainly due to their inherent flexibility. However, current wireless solutions lack the capability to provide the deterministic, low delay service required by many industrial applications. Moreover, the high level of interference generated by industrial equipment limits the coverage that ensures acceptable performance. Multihop solutions, when combining frame forwarding with higher node density, have the potential to provide the needed coverage while keeping radio communication range short. However, in multihop solutions, the medium access time at each of the nodes traversed additively contributes to the end-to-end delay and the forwarding delay (i.e., the time required for packets to be processed, switched, and queued) at each node is to be added as well. This paper describes time-driven access and forwarding, a solution for guaranteeing deterministic delay, at both the access and forwarding level, in wireless multihop networks, analyzes its properties, and assesses its performance in industrial scenarios.

Efficiency of packet voice with deterministic delay

Packet switching is appealing for carrying real-time traffic because it can benefit from (possibly variable bit rate) compression schemes and statistical multiplexing to more efficiently exploit network resources. This work explores the efficiency of IP telephony in terms of the volume of voice traffic carried with deterministically guaranteed quality related to the amount of network resources used. An IP network carrying compressed voice is compared to circuit switching carrying PCM (64 kb/s) encoded voice, and some design choices affecting IP telephony efficiency are discussed.

Data mining techniques for effective and scalable traffic analysis

This paper describes a novel approach to traffic analysis in high speed networks based on data mining techniques. Data mining techniques are here applied as a means to effectively process the significant amount of captured data. The paper provides a first evaluation of the proposed approach in terms of its ability of extracting relevant information and its computational requirements. Such evaluation is based on experiments run on a prototypal implementation of the proposed approach.

End-to-end delay of videoconferencing over packet switched networks

Videoconferencing is an important global application -it enables people around the globe to interact when they are far from one another. In order for the participants in a video-conference call to interact naturally, the end-to-end delay should be below human perception-about 100 ms. Since the global propagation delay can be about 100 ms, the actual end-to-end delay budget available to the system designer (excluding propagation delay) can be no more than 10 ms. We identify the components of the end-to-end delay in various configurations with the objective of understanding how it can be kept below the desired 10 ms bound. We analyze these components going step-by-step through six system configurations obtained by combining three generic network architectures with two video encoding schemes. We study the transmission of raw video and variable bit rate (VBR) MPEG video encoding over (i) circuit switching, (ii) synchronous packet switching, and (iii) asynchronous packet switching. In addition, we show that constant bit rate (CBR) MPEG encoding delivers unacceptable delay, which is on the order of the group of pictures (GOP) time interval. This study shows that having a global common time reference, together with time-driven priority (TDP) and VBR MPEG video encoding, provides adequate end-to-end delay, which is (i) below 10 ms, (ii) independent of the network instant load, and (iii) independent of the connection rate. The resulting end-to-end delay (excluding propagation delay) can be smaller than the video frame period, which is better than what can be obtained with circuit switching.