CURRENT_MEETING_REPORT_
Reported by Peter Furniss/Consultant
Minutes of the Minimal OSI Upper-Layers Working Group (THINOSI)
This was our first meeting as a Working Group. Most of the time was
spent reviewing the first draft of the bytestream cookbook and
especially the technical choices of what OSI upper-layers features
should be included.
Some guiding principles emerged:
o Interworking with ``full'' OSI implementations was a key purpose of
the thinosi approach and must be maintained, even at the cost of
some complexity.
o Inclusion or exclusion of features is determined by (and
determines) the set of application protocols that can be supported.
o It will be little trouble to add additional features (thus widening
the application range) once the basic format and style is worked
out - these could be alternatives in the same document or in
separate ones.
o If at all possible the set of supported application protocols
should include the DAP and X.400 P7 protocol. (These are not
actually byte-stream in the sense we have now, but at least DAP
should be possible with only a two octet change. P7 to be
investigated. PRF)
A number of conclusions were reached (most of these are confirmations of
what is in the first draft).
o Expect to receive any of the various allowed encodings of lengths,
etc.
o Describe sending of one application abstract-syntax and transfer
syntax name (in addition to the ACSE as & ts), but also describe
how, as responder, to locate and reply when these are one of a
number of offered abstract syntaxes and/or transfer syntaxes (how
to send and use multiple as and ts is one of the extension
possibilities).
o Do not use the invocations ids or the responding AP-title,
AE-qualifier (ignore happily on receipt).
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o Do not use the userdata field on ACSE A-ASSOCIATE or A-RELEASE
exchanges.
o Do allow the user data on the ACSE user abort to be used by the
application (typically to carry application- or
implementation-specific error/explanation messages).
o Use Session version 2 (with the Common Upper-Layer Requirements
limits on userdata).
o Include the correct procedure to follow when a release collision
occurs (this is different for the association initiator and
responder).
o Identify more clearly where the cookbook is taking advantage of a
CULR part 1 restriction.
o Do not include re-use of transport (although this can improve
efficiency, it is always *additional* to starting with new
T-connections, and thus makes the implementation more complex.)
o Do not shorten the explanatory text at the beginning or move it to
another document (clarify it by all means).
o Change the layout of the octet sequences to a more rigid
tag-length-value column format, with the datatype of primitive
values in a fourth column. Indent to show the nesting if feasible.
e.g.,
30 80 {4 . list of transfer syntaxes
06 02 5101 oid . BER transfer syntax
00 00 }4 . e-o-c for ts list
The Group was uncertain on whether the lengths of constructed elements
should all be indefinite, all definite, or follow a pattern of whatever
is convenient. For interworking all possibilities must be understood on
receipt, but various performance payoffs are possible. The views of the
mailing list will be sought.
There was also some discussion of related work in other circles.
o A profile for ``minimal OSI functionality'' is being developed in
the OIW and EWOS regional workshops (these are the OSI profiling
bodies for North America and Europe). This is intended to be part
three of Common Upper-Layer Requirements. The mOSI profile and
thinosi work have a common origin. At present, the upper-layer
facilities supported in mOSI and in thinosi are not quite the same.
It will be highly desirable for there to be one single selection of
features for both. Attempts will be made to align these - in
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particular the new draft of the cookbook should be made available
to the EWOS technical liaison group (TLG) in time for their next
meeting in April.
o Within X/Open, a new appendix for the XTI interface is being
developed that defines the use of this interface for minimal OSI.
The Group will meet in Amsterdam.
Attendees
John Boatright bryan_boatright@ksc.nasa.gov
Kevin Carosso kvc@innosoft.com
George Chang gkc@ctt.bellcore.com
Peter Furniss p.furniss@ulcc.ac.uk
Sylvain Langlois Sylvain.Langlois@exp.edf.fr
Mark Needleman mhn@stubbs.ucop.edu
Geir Pedersen Geir.Pedersen@usit.uio.no
Jim Romaguera romaguera@cosine-mhs.switch.ch
Keith Sklower sklower@cs.berkeley.edu
Klaus Truoel truoel@gmd.de
William Warner warner@ohio.gov
Les Wibberley lhw24@cas.org
Charles Young Charles.E.Young@att.com
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