OSI Upper-Layer Communications for Applications (skinstak)
Charter Status: Concluded February, 1993 Chair(s): Peter Furniss Description of Working Group: Application protocols originally designed for use over TCP can effectively use the upper-layers of OSI, that is the ACSE (Association Control Service Element), Presentation and Session protocols as their ``transport'' mechanism. The IPS application protocol is thus migrated to be another OSI protocol, and could subsequently be integrated with other OSI application protocols. The communication requirements of such application protocols are essentially connect, read and write. This can be met by the OSI upper-layer protocols, using only their basic features. However, for such a migration there need to be a) a specification of the use of various OSI parameters and fields for this purpose, b) interfaces to OSI that are as close as possible to those for original supporting IPS protocols, and c) OSI implementations of reasonable efficiency Item a) is essential for interworking at all, b) is needed to reduce the conversion effort, and c) to make the migrated application usable. The ``skinny stack'' approach, where the OSI implementation provides only those features needed by the application is a possible solution to c). The intent of the group is to identify the requirements for a) and develop the specifications for b). Other groups are also planning to consider different aspects of these. For a), the North American OSI implementors workshop (OIW) intend developing profiles for basic communications using the upper-layers, but there are important addressing and other questions that are specific to TCP to OSI migration. For b), it is intended that the IETF working group should consider specification of the use of the socket interface to access the OSI upper- layers. This will define representations of those OSI protocol fields that need to be available to the programmer and specify values for those that can be fixed. Although the initial work will concentrate on ex-TCP migrants, consideration will also be given to ex-UDP migrants and, especially for the interface aspects, to further extending the interface to provide access to other OSI parameters/fields. This would allow new application protocols, specified initially for use over OSI, to be built using the socket interface. Although the mapping will be supportable using ``skinny stacks'' (minimal functionality implementations), it will define conformant use of the OSI protocols and so can be achieved by general-purpose OSI implementations. No special remote management issues are expected - remote management will be by the usual methods for the environment. Security issues will include whether ACSE-authentication should be accessible.