Report on 1003.12: Protocol Independent Interfaces

[Peter Collinson]

Submitted-by: pc at hillside.co.uk (Peter Collinson)

USENIX Standards Watchdog Committee
Stephen R. Walli <stephe at usenix.org>, Report Editor
Report on 1003.12: Protocol Independent Interfaces

Mike Karels <karels at cs.berkeley.edu> reports on the April
15-19, 1991 meeting in Chicago, IL:

Summary

The POSIX.12 (Protocol Independent Interfaces, PII) working group
spent the April meeting planning strategy for its new direction and
coordinating with other groups.  The group will produce a standard
encompassing both the BSD sockets and X/Open Transport Interface
(XTI).  Liasison meetings were held with X/Open representatives, the
Name Space/Directory Services group (POSIX.17) and the Real-Time group
(POSIX.4). The group discussed language independent specification
issues with Paul Rabin.

Report

POSIX.12 (Protocol Independent Interfaces, PII) spent the April
meeting adjusting to its new direction and coordinating with other
groups.  At the last meeting, the group decided to abandon its
previous strategy of producing a new Detailed Network Interface (DNI)
with the best features of both the socket and X/Open Transport
interfaces (XTI).  XTI is derived from AT&T's Transport Level Interface
(TLI).  After reviewing input from users and vendors, the group
decided instead to produce a standard including both existing
interfaces.  In addition, the standard will include the Simple Network
Interface (SNI), which would insulate the programmer from lower-level
details.

The April meeting included discussions of the changes or additions
that were needed for the existing interfaces to become standards.  A
poll had been sent to several mailing lists and news groups, but few
concrete suggestions were received.  Most of the suggestions for
extensions have come from inside the working group.  Suggestions for
changes in sockets have come mostly from the Berkeley representatives,
and suggestions for XTI have come mainly from people active in the
X/Open technical community.

A fair amount of time was devoted to the proposal for extending XTI
option management by Gerhard Kieselmann.  The proposal allows much
more flexible option management by encoding option values with types
and lengths.  The encoding is similar to the encoding of ancillary
data in the 4.3-Reno send and receive calls.  The main point of
contention was whether the transport provider should maintain both
current settings and default settings to be used for any future
connections.

The discussions of extensions to the socket interface was confined to
a description of the recent Berkeley changes (4.3-Reno) to the socket
interface.

The meeting schedule was nearly filled with coordination meetings with
other groups.  Petr Janacek of X/Open reported on the status of future
XTI specifications.  Other than the option management proposal
mentioned above, the XPG4 version of XTI has been finalized.  It is
hoped that the XPG5 version of XTI would be aligned with the POSIX
version.  At the last meeting, POSIX.12 asked X/Open for editorial
assistance in producing a POSIX version of XTI.  Petr replied that the
budget did not allow for assistance at this time, but that an on-line
version of XTI would be made available.

Paul Rabin met with the PII group to discuss issues surrounding POSIX
language independent specifications.  The working group currently
hopes to produce a single language independent specification for DNI;
there would be two C language bindings, namely sockets and XTI.  This
should prevent the necessity of providing two interfaces for languages
other than C, but makes the language independent specification more
difficult to produce.

The POSIX.12 group also met with members of the Name Space/Directory
Services group (POSIX.17) to discuss the DNI dependency on the
Directory Services interfaces.  There are some problems in this area;
the NS/DS group currently intends to provide an interface only to the
X.500 directory service, while the PII group assumes an interface that
could include other services such as the Internet Domain Name System.
The NS/DS group intends to provide a full-featured low-level interface
to the directory service based on the X/Open X.500 API.  However, they
also plan to include simplified higher-level interfaces to answer
needs such as this one.

The final coordination meetings were with members of the Real-Time
group.  The current Real-Time draft includes an interprocess
communication (IPC) facility that many believe is too complex and does
not extend gracefully to handle networked systems.  Many hoped that
the IPC interface could be replaced by the 1003.12 interface, with
real-time extensions as necessary.  A group is working on a straw-man
proposal in time for the July meeting.


Volume-Number: Volume 24, Number 26