Keywords OSI, transport layer, multimedia communications systems, ATM, ODP, B-ISDN, MANs
Start Date: 29-OCT-90 / Duration: 24 months
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The existing OSI protocols were defined in a technological environment where communication lines had low bandwidth and poor quality. The emergence of new communication techniques such as high speed LANs and MANs and broadband-ISDN has dramatically changed this situation. The potential bandwidth offered by these new communication environments is jeopardised by the existing OSI protocols of layers 3 to 7.
Furthermore, the application environment is changing with the introduction of the multimedia, the new distributed applications and the ODP concept. New requirements are coming from these new application areas and the existing OSI lower layers protocols and services do not provide all services needed to meet these requirements.
The aim of the OSI 95 project was to integrate high-speed MANs and WANs into the OSI reference model, to revisit the OSI protocols and services, and to design high-performance protocols and services appropriate to offer adequate high performance services to the application layer. The project focused on four main objectives:
For the design of the new transport service and protocol, the project studied a methodology of design based on LOTOS, a standardised formal description technique, and applied this methodology to the design of a new high performance transport protocol called TPX, based on a service such as the standard LLC type 1 service, and offering a transport connection mode service upward compatible with the existing one. The specification of new high speed protocols in LOTOS requires to introduce description of time constraints in the language: for this purpose, the project proposed an extension of LOTOS.
The design of TPX took into account as many criteria as possible including proposed new transport protocols such as XTP (Xpress Transfer Protocol) designed for efficient implementation on silicon. This protocol was evaluated in detail with ESTELLE tool kit. The design of TPX took also into account the possibility of implementing the protocol in VLSI technology. This aspect was analysed. In parallel, the project studied the evolving computing environment in order to define the new transport service required by emerging applications. Three elements of this environment have been identified and were studied in detail:
High speed MANs and WANs and ATM-based networks were analysed in order to characterise and specify the provided services. This is an essential step towards the integration of these networks into the OSI world without relying on gateways which are very often performance killers. The project also addressed high performance issues related to the session and presentation layers, and related to the synchronisation functions.
The four major goals achieved were:
In addition to these results, and supporting them, the following activities were performed:
The technical conclusions of the project are described in details in the publicly available OSI 95 final technical report.
With the emergence of a new generation of high performance communication systems, industrial IT companies have to investigate carefully new opportunities offered by broadband networking technologies, in particular ATM technology. Participation in the OSI 95 project allowed to gain a valuable experience and expertise in this specific area, and to make various experimentations needed for implementation of new generations of end systems. One important aspect to be highlighted is that the project was an active actor in the international standardisation arena and provided contributions for new high performance protocols. A new standardisation work leading at the definition of an enhanced OSI transport protocol is now started on basis taking into account European market requirements.
Mr Jacques Levasseur
Rue Jean Jaurès
F - 78340 Les Clayes Sous Bois
tel: + 33/ 1-30806636
fax: + 33/ 1-30806681
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INRIA - F - P
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UNIVERSITE DE LIEGE - B - P
UNIVERSIDAD POLITECNICA DE MADRID - E - P
UNIVERSITY OF LANCASTER - UK - P
INSTITUT NATIONAL DES
TELECOMMUNICATIONS - F - A
OSI 95 - 5341, December 1993
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html version of synopsis by Nick Cook