Daniele Roffinella

A Reconfigurable High-Speed Optical System for Integrated Local Communications

The introduction of optical fibers in local area networks makes it possible to implement wide-band communication systems integrating all the communication services (telephone, data, images, etc.) foreseen in future office scenarios. This paper describes a reconfigurable high-speed local communication system, which is currently under development at the Centro Studi e Laboratori Telecomunicazioni (CSELT), conceived to attain high reliability and efficiency features, therefore suitable for a wide range of application environments, such as automated offices, integrated manufacturing, hospitals, etc. The access organization is based on a hybrid (i.e., circuit and packet) protocol, which guarantees each type of traffic the required grade of service, while allowing an optimal exploitation of the transmission capacity. Fault-tolerance issues are taken as a guideline in the overall system conception and, in particular, in the transmission subsystem design. The transmission subsystem presently uses available optical technology to implement a loop-shaped bus topology capable of reconfiguring by means of a distributed algorithms, when a link or node fails.

Coded Speech in Packet-Switched Networks: Models and Experiments

This paper considers the possibility of introducing packetized voice traffic into a packet-switched network. It is well known that the network must assure voice packets sufficient delay characteristics for conversational speech, i.e., low delay between speaker and listener and low delay jitter or variance. To reach these goals, simplified protocols and priority rules for voice handling are proposed and evaluated. A model of a packet switching node structure capable of handling both data and voice is derived for both analytical and simulation approaches. The use of low bit rate voice encoders is considered. The necessity of avoiding the transmission of silent intervals is discussed in relation to the behavior of packet voice receivers. Proposed strategies are compared by means of analytical tools and simulation experiments considering the presence of voice, interactive, and batch data packets.

Interworking Solutions for a Two-Level Integrated Services Local Area Network

A new generation of integrated services local networks (ISLNs) is needed to yield to local area users the provision of voice, data, and images in a cost-effective manner. Besides high-speed and service integration features, these advanced multiservice communication systems have to also provide powerful interconnection with both public networks and traditional LANs. So conception and design of the interconnection units, i.e., gateways and bridges, have to be carried out contextually with the network architecture definition. The paper addresses the interworking solutions adopted for a local integrated optical network (LION) currently under development. The architecture of bridges and gateways allowing users belonging to different LION subnetworks to communicate with public networks and commercial systems is also described. In particular, the interconnection with the integrated services digital network (ISDN) is highlighted.

Standardization for high-speed networks and services: status and trends

A brief overview is given on background issues, concerning in particular the network technologies and services being developed to face the new market challenges. The paper focuses then on the current status of international standardization activities in the high speed arena. Established organizations such as CCITT, ISO, ETSI, IEEE have been working on these issues for the past few years; a number of interest groups (ESIG, EURESCOM, ATM Forum) have also been created, to answer the growing need for early implementation specifications, based on available standards and suitable for early field trials. Finally, the evolution trends in the high speed arena are dealt with, summarizing the expected progress and highlighting crucial areas where close attention will have to be paid to ensure the timely development of standards.

Metropolitan area networks: Standards, services and performance†

The paper, after a general survey of Metropolitan Area Network (MAN) issues, in which the market demand and recent trends in MAN concepts (e.g. relationship with Broadband Integrated Services Digital Network, B-ISDN) are considered, examines the ongoing MAN related activities inside standard-setting bodies such as IEEE (Institute of Electrical and Electronic Engineers) and ETSI (European Telecommunications Standards Institute). Emerging trends in architecture, protocols and services are reviewed. A more detailed characterization of the bearer services MANs are required to provide (i.e. connectionless, non isochronous connection oriented and isochronous) is then given, emphasizing their broadband nature and the related applications; the functions providing these services within the Distributed Queue Dual Bus (DQDB) framework are briefly described. The last section is devoted to a discussion of MAN performance. specifically in terms of fairness, focusing again on the DQDB protocol, which appears to be the most promising solution for MANs, and on possible improvements of its characteristics.

A High-Speed Optical System For Local Area Network

A high-speed optical IAN is described, supporting both stream and packet services. A hybrid multiple access protocol. specifically designed for service integration, is presented along with its main charac teristics. Reliability aspects are examined and solved using a network reconfiguration procedure. The transmission subsystem is analyzed, fixing the main characteristics of the network and highlighting the transmission problems.