Frontmatter

©January 2000, The Open Group All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owners.

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Preface

The Open Group

The Open Group is a vendor and technology-neutral consortium which ensures that multi-vendor information technology matches the demands and needs of customers. It develops and deploys frameworks, policies, best practices, standards, and conformance programs to pursue its vision: the concept of making all technology as open and accessible as using a telephone.

The mission of The Open Group is to deliver assurance of conformance to open systems standards through the testing and certification of suppliers' products.

The Open group is committed to delivering greater business efficiency and lowering the cost and risks associated with integrating new technology across the enterprise by bringing together buyers and suppliers of information systems.

Membership of The Open Group is distributed across the world, and it includes some of the world's largest IT buyers and vendors representing both government and commercial enterprises.

More information is available on The Open Group Web Site at http://www.opengroup.org.

Open Group Publications

The Open Group publishes a wide range of technical documentation, the main part of which is focused on development of Technical and Product Standards and Guides, but which also includes white papers, technical studies, branding and testing documentation, and business titles. Full details and a catalog are available on The Open Group Web Site at http://www.opengroup.org/pubs.

• Product Standards

  A Product Standard is the name used by The Open Group for the documentation that records the precise conformance requirements (and other information) that a supplier's product must satisfy. Product Standards, published separately, refer to one or more Technical Standards.

  The "X" Device is used by suppliers to demonstrate that their products conform to the relevant Product Standard. By use of the Open Brand they guarantee, through the Open Brand Trademark License Agreement (TMLA), to maintain their products in conformance with the Product Standard so that the product works, will continue to work, and that any problems will be fixed by the supplier. The Open Group runs similar conformance schemes involving different trademarks and license agreements for other bodies.

• Technical Standards (formerly CAE Specifications)

  Open Group Technical Standards, along with standards from the formal standards bodies and other consortia, form the basis for our Product Standards (see above). The Technical Standards are intended to be used widely within the industry for product development and procurement purposes.

  Technical Standards are published as soon as they are developed, so enabling suppliers to proceed with development of conformant products without delay.

  Anyone developing products that implement a Technical Standard can enjoy the benefits of a single, widely supported industry standard. Where appropriate, they can demonstrate product compliance through the Open Brand.

• CAE Specifications

  CAE Specifications and Developers' Specifications published prior to January 1998 have the same status as Technical Standards (see above).

• Preliminary Specifications

  Preliminary Specifications have usually addressed an emerging area of technology and consequently are not yet supported by multiple sources of stable conformant implementations. There is a strong preference to develop or adopt more stable specifications as Technical Standards.

• Consortium and Technology Specifications

  The Open Group has published specifications on behalf of industry consortia. For example, it published the NMF SPIRIT procurement specifications on behalf of the Network Management Forum (now TMF). It also published Technology Specifications relating to OSF/1, DCE, OSF/Motif, and CDE.

In addition, The Open Group publishes Product Documentation. This includes product documentation-programmer's guides, user manuals, and so on-relating to the DCE, Motif, and CDE. It also includes the Single UNIX Documentation, designed for use as common product documentation for the whole industry.

Versions and Issues of Specifications

As with all live documents, Technical Standards and Specifications require revision to align with new developments and associated international standards. To distinguish between revised specifications which are fully backwards compatible and those which are not:

• A new Version indicates there is no change to the definitive information contained in the previous publication of that title, but additions/extensions are included. As such, it replaces the previous publication.

• A new Issue indicates there is substantive change to the definitive information contained in the previous publication of that title, and there may also be additions/extensions. As such, both previous and new documents are maintained as current publications.

Corrigenda

Readers should note that Corrigenda may apply to any publication. Corrigenda information is published on The Open Group Web Site at http://www.opengroup.org/corrigenda.

Ordering Information

Full catalog and ordering information on all Open Group publications is available on The Open Group Web Site at http://www.opengroup.org/pubs.

This Document

Sockets (Part 2 of this document) is mandatory. XTI (Part 3) is optional. The XTI interface is now considered to be obsolete. Writers of new applications using the Internet protocol suite are recommended to use sockets rather than XTI. Where protocols for which there is no sockets support are in use, XTI is still recommended in preference to proprietary APIs.

Both Sockets and XTI are specified for use over Internet protocols (TCP, UDP and IP) and ISO Transport protocols. They also include a set of Internet address resolution interfaces which are commonly used in conjunction with Sockets. XTI support for many other protocols is described in appendices to XNS. Sockets and Address Resolution must be supported over the Internet protocols. XTI may be supported over either the Internet or ISO Transport protocols. Other protocols may also be provided, but this is not required for the Brand.

Branded UNIX98 systems support the Sockets, XTI and Address Resolution interfaces described in XNS Issue 5.

XNS Issue 5.2 contains a number of new features over the previous publication¹. The most important new feature in XNS Issue 5.2 is the inclusion of Internet Protocol version 6 (IPv6) functionality, in a manner which is aligned with the relevant IETF IPv6 standard (RFC 2553). Other new features include:

• Any text that relates to behaviour of the implementation when _XOPEN_SOURCE is less than 500 is informative, not normative. This behaviour is specified normatively in earlier issues of XNS.

• Conformant systems are not required to provide the OPT_NEXTHDR macro.

• Protocol-specific symbols defined in <xti_inet.h> or <xti_osi.h> are not required to be available when <xti.h> is included by the application but <xti_inet.h> or <xti_osi.h> (respectively) is not included by the application.

• An implementation is only required to provide protocol-specific headers for those protocols that it supports.

• An implementation need not make available symbols marked in XNS Issue 5 as "LEGACY".

• Although identifiers marked as "LEGACY" are not specified as being reserved for any use by the implementation, implementations may make them available.

Structure

• Part 1 gives a common introduction. It contains information comparable to that in the XSH specification. It applies to the Sockets and Address Resolution interfaces (see Part2 below) if the UNIX compilation environment is in effect.

• Part 2 defines the Sockets interface.

• Part 3 defines the XTI interface.

• Part 4 includes API mapping information to other transport providers, and other guidance for implementers.

Typographical Conventions

• Bold font is used in text for options to commands, filenames, keywords, type names, data structures and their members.

• Italic strings are used for emphasis or to identify the first instance of a word requiring definition. Italics in text also denote:

  • command operands, command option-arguments or variable names, for example, substitutable argument prototypes

  • environment variables, which are also shown in capitals

  • utility names

  • external variables, such as errno

  • functions; these are shown as follows: name(). Names without parentheses are C external variables, C function family names, utility names, command operands or command option-arguments.

• Normal font is used for the names of constants and literals.

• The notation <file.h> indicates a header file.

• Names surrounded by braces, for example, {ARG_MAX}, represent symbolic limits or configuration values which may be declared in appropriate headers by means of the C #define construct.

• The notation [ABCD] is used to identify a return value ABCD, including if this is an an error value.
  

• Syntax, code examples and user input in interactive examples are shown in fixed width font. Brackets shown in this font, [], are part of the syntax and do not indicate optional items. In syntax the | symbol is used to separate alternatives, and ellipses (...) are used to show that additional arguments are optional.

• All text marked by the side-headings Note or Notes is for added information, and is non-normative.

Change History

• Issue 5.1 Draft 2.0:
  Re-structured to accommodate IPv4/IPv6, but no IPv6 content added
  Corrigendum U031 inserted.
  Change Requests HP-XTI-1/2/3 applied.

• Issue 5.1 Draft 3.0:
  IPv6 CRs TOG:XNS5-01R2, TOG:XNS5-02R2, TOG:XNS5-03R2, TOG:XNS5-05 and TOG:XNS5-06 (ogtgnet 6865 attachments) applied, and the resulting text changes marked with a special "+" change mark (i.e. ".mc +").
  The following CRs approved at XNET53 applied, and the resulting text changes marked with the normal "|" change mark.

  SUN:XNS-101	ogtgnet 6741
  SUN:XNS-102R1	ogtgnet 6879
  SUN:XNS-103	ogtgnet 6741
  SUN:XNS-001	ogtgnet 6799
  SUN:XNS-002	ogtgnet 6799
  SUN:XNS-003	ogtgnet 6799
  SUN:XNS-005	ogtgnet 6800
  SUN:XNS-006R	ogtgnet 6919
  TOG:XNS5-05	ogtgnet 6761, with modification defined in the XNET-53 meeting minutes. (Note that this is a different CR from TOG:XNS5-05 in ogtgnet 6865 although it does duplicate the CR number)

• Issue 5.2 Draft 2.0:
  The following Change Requests as approved in June 1999 were applied:

  
  TOG:XNS-001
  TOG:XNS-002
  TOG:XNS-003
  TOG:XNS-004
  TOG:XNS-005
  TOG:XNS-006
  TOG:XNS-007
  TOG:XNS-008
  TOG:XNS-009
  TOG:XNS-010
  TOG:XNS-011
  TOG:XNS-012
  TOG:XNS-013
  TOG:XNS-014
  

• Issue 5.2 Draft 3.0:
  The following Change Requests as approved in August 1999 were applied:

  
  SUN:XNS-001
  SUN:XNS-002
  TOG:XNS-001, with Additional IP Address Resolution Functions revised by:
  NRL:XNS_GAI-006,-009,-013,-014,-016,-017,-021,-022,-025.
  

  
  Further Change Requests as approved in November 1999 were applied:
  HP:XNS-001, SUN:XNS-001 - 013,015,017,018,020,021,023 - 030, TOG:XNS-001 - 008,010,011.
  

• Issue 5.2 Draft 4.0:
  This was the sanity-check copy. No sanity-check comments were received. Draft 4.0 was therefore published electonically as XNS Issue 5.2, C808.

Trade Marks

AT&T® is a registered trademark of AT&T in the U.S.A. and other countries.

Hewlett-Packard®, HP®, HP-UX®, and Openview® are registered trademarks of Hewlett-Packard Company.

Motif®, OSF/1®, UNIX®, and the "X Device" are registered trademarks and IT DialTone^TM; and The Open Group^TM; are trademarks of The Open Group in the U.S. and other countries.

SNA is a product of International Business Machines Corporation.

/usr/group® is a registered trademark of UniForum, the International Network of UNIX System Users.

Acknowledgements

• AT&T for permission to reproduce portions of its copyrighted System V Interface Definition (SVID) and material from the UNIX System V Release 2.0 documentation.

• The Institution of Electrical and Electronics Engineers, Inc. for permission to reproduce portions of its copyrighted material.

• The IEEE Computer Society's Portable Applications Standards Committee (PASC), whose Standards contributed to our work.

• The UniForum (formerly /usr/group) Technical Committee's Internationalization Subcommittee for work on internationalised regular expressions.

• The ANSI X3J11 Committees.

• The Open Group gratefully acknowledges the valued contribution of the following people in the development of this specification, along with their corporate affiliation at the time of their contribution:

  Josee Auber	Hewlett-Packard
  Kathryn Britton	IBM
  Philippe Camus	Groupe Bull
  Andrew Chandler	ICL
  Andre Cohen	Groupe Bull
  Paul Comstock	Hewlett-Packard
  Andrew Gollan	Sun
  Michel Habert	Groupe Bull
  Torez Hiley	USL
  Martin Jess	NCR
  Mukesh Kacker	Sun
  Gerhard Kieselmann	SNI
  David Laight	Fujitsu/ICL
  Jack McCann	DIGITAL
  Hiroshi Maruta	Hitachi

  Lori Mickelson	Unisys
  Laura Micks	IBM
  Finnbarr Murphy	DIGITAL
  Alagu Periyannan	Apple
  George Preoteasa	Hewlett-Packard
  John Ronciak	Unisys
  Seth Rosenthal	Novell
  Eric Scoredos	Hewlett-Packard
  Maria Stanley	DIGITAL
  Lutz Temme	SNI
  Roger Turner	IBM
  Keith Weir	ICL
  Robert Weirick	Unisys
  Greg Wiley	SFC (SCO)
  Isaac Wong	Hewlett-Packard

Referenced Documents

Internet

TCP

Transmission Control Protocol, RFC 793.

Also see TCP, Transmission Control Protocol, Military Standard, Mil-std-1778, Defense Communication Agency, DDN Protocol Handbook, Volume I, DOD Military Standard Protocols (December 1985)

UDP

User Datagram Protocol, RFC 768.

IPV4

Internet Protocol, RFC 791

ICMP

Internet Control Message Protocol, RFC 792

TP_ON_TCP

ISO Transport Service on Top of the TCP, RFC 1006

IPV6

Internet Protocol, Version 6, RFC 2460

IPV6_AD

IP Version 6 Addressing Architecture, RFC 2373

IPV6_BASIC_API

IPv6 Socket Interface Extensions, RFC 2553

HOSTS

DOD Internet Host Table Specification, RFC 952

ACSE

ISO 8649

ISO 8649:1988, Information Processing Systems - Open Systems Interconnection - Service Definition for the Association Control Service Element, together with:

Technical Corrigendum 1:1990 to ISO 8649:1988
Amendment 1:1990 to ISO 8649:1988
Authentication during association establishment.
Amendment 2:1991 to ISO 8649:1988
Connectionless-mode ACSE Service.

ISO 8650

ISO 8650:1988, Information Processing Systems - Open Systems Interconnection - Protocol specification for the Association Control Service Element, together with:

Technical Corrigendum 1:1990 to ISO 8650:1988
Amendment 1:1990 to ISO 8650:1988
Authentication during association establishment.

ISO/IEC 10035

ISO/IEC 10035:1991, Information Technology - Open Systems Interconnection - Connectionless ACSE Protocol Specification.

Presentation

ISO 8822

ISO 8822:1988, Information Processing Systems - Open Systems Interconnection - Connection-oriented Presentation Service Definition.

ISO 8823

ISO 8823:1988, Information Processing Systems - Open Systems Interconnection - Connection-oriented Presentation Protocol Specification.

ISO 8824

ISO 8824:1990, Information Technology - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1).

BER

ISO/IEC 8825:1990 (ITU-T Recommendation X.209 (1988)), Information Technology - Open Systems Interconnection - Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1).

ISO/IEC 9576

ISO/IEC 9576:1991, Information Technology - Open Systems Interconnection - Connectionless Presentation Protocol Specification.

Session

ISO 8326

ISO 8326:1987, Information Processing Systems - Open Systems Interconnection - Basic Connection-oriented Session Service Definition.

ISO 8327

ISO 8327:1987, Information Processing Systems - Open Systems Interconnection - Basic Connection-oriented Session Protocol Specification.

Amendment 3:1992 to ISO 8327:1987 - Additional Synchronization Functionality.

ATM

ATMNAS

ATM Forum: "Native ATM services: Semantic Description, Version 1", obtainable via anonymous ftp from Internet address ftp.atmforum.com, in directory /pub/approved-specs, files af-saa-0048.000.doc (Word 6.0) or af-saa-0048.000.ps (postscript).

UNI

ATM Forum: "ATM User-Network Interface (UNI) Specification, Version 3.1", published by Prentice Hall. Also obtainable electronically via anonymous ftp from Internet address ftp.atmforum.com, in directory /pub/UNI/ver3.1.

Other References

ISO C

ISO/IEC 9899:1990: Programming Languages - C, including Amendment 1:1995 (E), C Integrity (Multibyte Support Extensions (MSE) for ISO C).

ISO 7498

ISO 7498:1984, Information Processing Systems - Open Systems Interconnection - Basic Reference Model.

ISO Transport

		Connection-Oriented
Protocol Definition	IS 8073-1986	IS 8602
Service Definition	IS 8072-1986	IS 8072/Add.1-1986

Minimal OSI

ISO/IEC DISP 11188-3, International Standardized Profile - Common Upper Layer Requirements - Part 3: Minimal OSI Upper Layers Facilities, Version 6, 1994-04-14.

SVID

Networking Services Extension, System V Interface Definition (SVID) Issue 2, Volume III, 1986, UNIX Press, Morristown, NJ, USA.

NetBIOS

Mappings of NetBIOS services to OSI and IPS transport protocols are provided in the CAE Specification, October 1992, Protocols for PC Interworking: SMB, Version 2 (ISBN: 1-872630-45-6, C209).

SNA

SNA National Registry, IBM document G325-6025-0.

P1003_1G

Information Technology - Portable Operating System Interface (POSIX) - Part xx: Protocol Independent Interfaces (PII) Draft 6.6, IEEE P1003.1g/D6.6, March 1997.

RFC 1034

Domain Names - Concepts and Facilities, P. Mockapetris, November 1987.

RFC 1035

Domain Names - Implementation and Specification, P. Mockapetris, November 1987.

RFC 1886

DNS Extensions to support IP version 6, S. Thompson, C. Huitema, December 1995.

XSH, Issue 5

CAE Specification, January 1997, System Interfaces and Headers, Issue 5 (ISBN: 1-85912-181-0, C606), published by The Open Group.

XCU, Issue 5

CAE Specification, January 1997, Commands and Utilities, Issue 5 (ISBN: 1-85912-191-8, C604), published by The Open Group.

XBD, Issue 5

CAE Specification, January 1997, System Interface Definitions, Issue 5 (ISBN: 1-85912-186-1, C605), published by The Open Group.

Footnotes

1.

The previous XNS publication was Networking Services (XNS), Issue 5, CAE Specification, February 1997, (ISBN: 1-85912-165-9, C523).

The preceeding XNS publication was Networking Services, Issue 4, CAE Specification, September 1994, (ISBN: 1-85912-049-0, C438).