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:
- the design of new high-performance transport service and protocol
- the creation of new work items on high-speed protocols within ISO and the promotion of new transport protocol and service in international standardisation organisations
- the study of the way the B-ISDN will fit into the OSI reference model, and of the resulting new services
- the study of the requirements coming from the new computing environment (multimedia, ODP, distributed systems) on the transport service.
The four major goals achieved were:
specification of high performance transport services and protocol (called TPX) and introduction in ISO;
creation of the 'new work items' on high speed lower layers protocols in ISO;
definition of the requirements for transport services coming from distributed and multimedia applications;
definition of services offered by new broadband lower layers technologies, in particular broadband integrated services digital network (ISDN) based on asynchronous transmission (ATM).
In addition to these results, and supporting them, the following activities were performed:
analysis of adequacy of existing protocols to high speed communications, in particular evaluation of xpress transfer protocol (XTP);
implementation of a hardware ATM interface;
definition of guidelines for transport protocols very large scale integration (VLSI) implementation;
study of a methodology of design using LOTOS;
definition of a LOTOS extension for supporting time constraints;
study of applicability of existing higher layer protocol.
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.
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