ISO/IEC 9041-1:1997

Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Protocol — Part 1: Specification

Technologies de l'information — Interconnexion de systèmes ouverts (OSI) — Protocole de classe de base de terminal virtuel — Partie 1: Spécification

General Information

• Status: Published
• Publication Date: 18-Jun-1997
• ICS: 35.100.70 - Application layer
• Technical Committee: ISO/IEC JTC 1 - Information technology
• Drafting Committee: ISO/IEC JTC 1 - Information technology
• Current Stage: 9093 - International Standard confirmed
• Start Date: 16-Aug-2002
• Completion Date: 12-Feb-2026

Relations

• Revises: ISO 9041-1:1990/Cor 1:1992 - Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Protocol — Part 1: Specification — Technical Corrigendum 1
• Effective Date: 15-Apr-2008
• Revises: ISO 9041-1:1990/Amd 2:1992 - Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Protocol — Part 1: Specification — Amendment 2
• Effective Date: 15-Apr-2008
• Revises: ISO 9041-1:1990 - Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Protocol — Part 1: Specification
• Effective Date: 15-Apr-2008

Overview

ISO/IEC 9041-1:1997 - "Information technology - Open Systems Interconnection - Virtual Terminal Basic Class Protocol - Part 1: Specification" defines the protocol-level specification for the Virtual Terminal Basic Class in the OSI Application Layer. It describes how two Virtual Terminal Protocol Machines (VTPMs) interoperate-using the Presentation Layer and the Association Control Service Element (ACSE)-to provide terminal emulation and remote terminal services in an open-systems environment. Part 1 is the formal specification; Part 2 contains the Protocol Implementation Conformance Statement (PICS) proforma.

Key topics and technical requirements

• Scope and purpose: Procedures for connection-oriented transfer of data, control and reference information between VTPMs that implement the Virtual Terminal Basic Class Service.
• Protocol model: Operation modes (A-mode - asynchronous, S-mode - synchronous), protocol functional units, and access control concepts.
• Protocol elements and PDUs: Defines the structure and mapping of protocol elements (for example, VT-ASSOCIATE-REQ/RESP, VT-DATA, VT-RELEASE-REQ, VT-P-ABORT) to ACSE and Presentation service primitives and PDUs.
• Service interactions: Details interactions between VTPMs, between a VTPM and local VT service user, and with Presentation/ACSE providers.
• Procedures: Association establishment/release, negotiation (including profile switching and multiple interaction negotiation), data transfer, delivery control, token management, break/exception handling, and switch-profile procedures.
• Conformance: Static and dynamic conformance requirements and the expectation that implementers produce a PICS (Part 2) describing supported options and capabilities.
• Annexes: State tables and defined OBJECT IDENTIFIER names to support implementation and testing.

Practical applications

• Implementing standardized virtual terminal / terminal emulation services across heterogeneous systems.
• Enabling interoperability between terminal clients and host systems in OSI-based networks.
• Supporting network management consoles, legacy terminal access, remote administration, and embedded systems requiring terminal-style control.
• Serving as a specification reference for vendors developing VTPM implementations, middleware authors, and interoperability test laboratories.

Who should use this standard

• Protocol implementers and firmware developers building Virtual Terminal solutions.
• System integrators and software architects working on OSI Application Layer services.
• Test labs and QA teams creating conformance test suites and PICS reports.
• Standards bodies and documentation teams mapping legacy terminal functionality to OSI-based protocols.

Related standards

• ISO/IEC 9040 (Virtual Terminal Basic Class Service)
• ISO/IEC 7498-1 (OSI Basic Reference Model)
• ISO/IEC 8822 / 8824-1 / 8825-1 (Presentation, ASN.1)
• ISO/IEC 8649 (ACSE), ISO/IEC 8326 (Session), ISO/IEC 2022, ISO/IEC 6429, ISO/IEC 10731

Keywords: ISO/IEC 9041-1:1997, Virtual Terminal Basic Class Protocol, VTPM, Virtual Terminal, OSI, Presentation Layer, ACSE, PICS, protocol elements, terminal emulation, interoperability.

Standards Content (Sample)

I NTER NAT1 ONAL
ISOIIEC
STANDARD 9041-1
Second edition
1997-06-1 5
Information technology - Open Systems
Interconnection - Virtual Terminal Basic
Class Protocol -
Part 1:
Specification
Technologies de l'information - Interconnexion de s ystgmes ouverts
(OSI) - Protocole de classe de base de terminal virtuel -
Partie 1: Sp4cification
Reference number
ISO/IEC 9041-1 :1997(E)
ISOAEC 9041-1 :i 997(E)
Con tents
1 Scope .
2 Normative references . 1
3 Definitions . 2
3.1 Global OS1 definitions . 2
3.2 Association Control Service Element definitions . 2
3.3 Presentation Layer Service Element definitions . 2
3.4 Virtual Terminai Service definitions . 2
3.5 Virtual Terminal Protocol definitions . 2
4 Abbreviations . 3
4.1 Virtual Terminal Service abbreviations .
4.2 Miscellaneous . 3
4.3 VT Protocol elements .
5 Overview . 3
5.1 Virtual Terminal Service summary .
5.2 Model . 6
5.3 Service assumed from the Presentation Layer . 6
5.4 Service assumed from ACSE . 6
5.5 Functions of the VT Protocol . 7
5.6 Protocol Functional Units . 8
5.7 Modes of Operation . 8
5.8 Access Control . 8
.... 8
6 Protocol elements .
... 9
6.1 APQ (VT-P-ABORT) .
... 9
6.2 ASQ (VT-ASSOCIATE-REQ) .
... 9
6.3 ASR (VT-ASSOCIATE-RESP) .
.. 10
6.4 AUQ(VT.U.ABORT) .
.. 10
6.5 BKQ (VT.BREAK.REQ) .
.. 10
6.6 BKR (VT.BREAK.RESP) .
6.7 DAQ (VT-ACK-RECEIPT) . . 10
0 ISOAEC1997
All rights reserved . Unless otherwise specified. no part of this publication may be reproduced
or utilized in any form or by any means. electronic or mechanical. including photocopying
and microfilm. without permission in writing from the publisher .
ISO/IEC Copyright Office Case Postale 56 CH-1211 GenW 20 Switzerland
Printed in Switzerland
ii
O ISO/IEC ISO/IEC 9041 -1 :1997(E)
6.8 DLQ (VT-DELIVER) . 10
6.9 ENQ (VT-END-NEG-REQ) . 10
6.10 ENR (VT-END-NEG-RESP) . 10
6.11 GTQ (VT.GIVE.TOKEN) . 10
6.12 HW (VT-HIGH-PRI-DATA) . 10
6.13 NAQ (VT-NEG-ACCEPT) . 10
6.14 NW (VT-DATA) . 11
6.15 NIQ (VT-NEG-INVITE) . 11
6.16 NJQ (VT.NEG.REJECT) . 11
6.17 NOO (VT-NEG-OFFER) . 11
6.18 RLQ (VT-RELEASE-REQ) . 11
6.19 RLR (VT-RELEASE-RESP) . 11
6.20 RTQ (VT-REQUEST-TOKEN) . 11
6.21 SNQ (VT-START-NEG-REQ) . 11
6.22 SNR (VT-START-NEG-RESP) . 11
6.23 SPQ (VT-SWITCH-PROFILE-REQ) . 12
c
6.24 SPR (VT-SWITCH-PROFILE-RESP) . 12
6.25 UW (VT.URGENT.DATA) . 12
6.26 EXQ (VT-P-EXCEPTION-REQ) . 12
6.27 EXR (VT-P-EXCEPTION-RESP) . 12
7 Procedures . 12
8 Primary procedures . 13
8.1 Association Establishment . 13
8.2 Agreed Release . 13
8.3 Unconditional Termination . 13
8.4 Negotiation . 13
8.5 Data Transfer . 13
8.6 Delivery Control . 14
8.7 Token Management . 14
8.8 Break., . 14
9 Switch Profile procedures . 21
9.1 Association Establishment . 21
L
9.2 Agreed Release., . 21
9.3 Unconditional Termination . 21
9.4 Negotiation . 21
9.5 Data Transfer . 21
9.6 Delivery Control . 21
9.7 Token Management . 22
9.8 Break and Exception . 22
1 O Multiple Interaction Negotiation procedures . 22
10.1 Association Establishment . 22
10.2 Agreed Release . 23
10.3 Unconditional Termination . 23
10.4 Negotiation . 23
10.5 Data Transfer . 23
10.6 Delivery Control . 24
10.7 Token Management . 24
10.8 Break and Exception . 24
iii
ISO/IEC 9041 -1 :1997(E) O ISOllEC
11 Mapping of protocol elements . 24
11.1 Mapping to Association Control Services . 25
11.2 Use of Presentation Services . 27
12 Protocol data unit structure . 28
12.1 General format . 28
12.2 General definitions . 34
12.3 Conceptual Data Store definitions .
12.4 Control. Signal and Status definitions . 44
12.5 Device Object definitions . 47
13 Conformance . 50
13.1 Dynamic conformance requirements .
13.2 Static conformance requirements . 50
13.3 Protocol Implementation Conformance Statement (PICS) .
Annex A StateTables . 51
A.l General . 51
A.2 Parameters. VTPM rights and variables .
A.3 Conventions for use of state tables . 53
A.4 Actions to be taken by the VTPM . 53
Annex B Defined OBJECT IDENTIFIER names . 69
.
iv
ISO/IEC 9041-1 :1997(E)
O ISOllEC
Foreword
IS0 (the International Organization for Standardization) and IEC (the International
Electrotechnical Commission) form the specialized system for worldwide stand-
ardization. National bodies that are members of IS0 and IEC participate in the
development of International Standards through technical committees established by
L
the respective organization to deal with particular fields of technical activity. IS0 and
IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with IS0 and IEC, also
take part in the work.
In the field of information technology, IS0 and IEC have established a joint technical
committee, ISOllEC JTC1. Draft International Standards adopted by the joint technical
committee are circulated to national bodies for voting. Publication as an International
Standard requires approval by at least 75% of the national Mies casting a vote.
International Standard IS0 9041 -1 was prepared by Joint Technical Committee
ISOllEC JTC1, Information technology, Subcommitee SC21, Open systems intercon-
nection, data management and open distributed processing.
This second edition cancels and replaces the first edition (ISOAEC 9041 -1 :1990),
which has been technically revised. It also incorporates Amendment 2:1992,
Technical Corrigendum 1 :1992 and Technical Corrigendum 2:1993.
ISOllEC 9041 consists of the following parts, under the general title Information
technology - Open Systems Interconnection - Virtual Terminal Basic Class Protocol:
-
-Part 1: Specification
- Part 2: Implementation Conformance Statement (PICS) Proforma
Annexes A and B form an integral part of this part of ISOAEC 9041.
V
I
O ISOllEC
ISO/IEC 9041-1 :1997(E)
Introduction
ISO/IEC 9041 is one of a set of International Standards produced to facilitate the
interconnection of computer systems. It is related to other International Standards in
the set asdefined in the Reference Model for Open Systems Interconnection (ISOIIEC
7498-1). The Reference Model subdivides the area of standardization for intercon-
-
nection into a series of layers of specification, each of manageable size.
This part of ISOIIEC 9041 defines the manner in which two protocol machines (called
Virtual Terminal Protocol Machines or VTPMs) in the Application Layer of the
Reference Model for Open Systems Interconnection communicate in order to provide
the Virtual Terminal Basic Class Service defined in ISOIIEC 9040 making use of the
Presentation Layer and of the assmiation control service of ACSE within the Appli-
cation Layer.
Part 2 of ISO/IEC 9041 includesthe Protocol Implementation Conformance Statement
(PICS) proforma for the Virtual Terminal Basic Class Protocol as defined in this part
of ISO/IEC 9041.
vi
~~~
INTERNATIONAL STANDARD O IWIEC ISOAEC 9041 -1 : 19970
Information technology - Open Systems Interconnection -
Virtual Terminal Basic Class Protocol - Part 1 : Specification
1 Scope 2 Normative references
The following standards contain provisions which, through
This part of ISO/IEC 9041 specifies: reference in this text, constitute provisions of this part of
ISOlIEC 9041. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to
a) a set of procedures for the connection-oriented transfer of
~
agreements based on this part of ISOlIEC 9040 are encour-
data, control and reference information between protocol
aged to investigate the possibility of applying the most recent
machines which implement the functions of a provider of
editions of the standards listed below. Members of IEC and
the Basic Class Virtual Terminal Service;
IS0 maintain registers of currently valid International Stand-
ards.
b) the two modes in which those procedures operate;
ISOllEC 2022:1994, Information technology- Character code
c) the structure of protocol elements used for the transfer of
structure and extension techniques (fourth edition).
data and control information and the mapping of these
protocol elements onto ACSE and lower layer services;
ISOlIEC 6429:1992, Information technology - Contrd func-
tions for coded character sets (third edition).
d) the means of negotiating the functional units to be used by
the protocol machines and the parameters of the service;
ISOllEC 7498-1:1994, lnformation technology - Open Sys-
tems Interconnection - Basic Reference Model: The Basic
Model.
e) the structure and mapping of protocol elements used for
the transfer of data and control information.
ISOllEC 7498-3: 1997, Information technology - Open Sys-
tems Interconnection - Basic Reference Model: Naming and
The procedures are defined in terms of:
addressing.
fl the interactions between Virtual Terminal Protocol Ma-
ISOllEC 8326:1996, Information technology - Open System
chines through the exchange of Virtual Terminal protocol
Interconnection - Session service definition (second edition).
e leme nt s;
ISOlIEC 8649: 1996, Information technology - Open Systems
g) the interactions between a Virtual Terminal Protocol Ma- Interconnection - Service definition for the Association Control
chine and the Virtual Terminal service user in the same
Service Element (second edition).
system through the exchange of Virtual Terminal service
ISOllEC 8822: 1994, Information technology - Open Systems
primitives;
Interconnection - Presentation service definition.
h) the interactions between a Virtual Terminal Protocol Ma-
ISOllEC 8824-1: 1995, Information technology- Abstract Syn-
chine and the ACSE and Presentation Service providers
tax Notation One (ASN. 1): Specification of basic notation.
through the exchange of service primitives.
ISO/IEC 8825-1 :1994, Information technology - ASN. 1 en-
This part of ISOlIEC 9041 also specifies conformance require-
coding rules: Specification of Basic Encoding Rules (BER),
ments (see clause 13) for systems implementing these proce-
Canonical Encoding Rules (CER) and Distinguished Encoding
dures. It does not contain tests which can be used to
Rules (DER).
demonstrate this conformance.
ISOlIEC 9040: 1997, Information technology- Open Systems
These procedures are applicable to instances of communica-
Interconnection - Virtual Terminal Basic Class Service.
tion between systems that support the Basic Class Virtual
Terminal Service in the Application Layer of the Reference ISOlIEC 10731 :1994, Information technology - Open Sys-
Model for Open Systems Interconnection and which wish to tems Interconnection - Basic Reference Model - Conventions
for the definition of OS1 services.
interconnect in an open systems environment.
O ISOllEC
ISO/IEC 9041-1 :1997(E)
Field Definition Control Object (FDCO);
The International Register of coded Character Sets to be used
1 O)
with Escape Sequences. ’)
Field Definition Record (FDR);
11)
Field Element;
12)
Field Entry Condition (FECI;
3 Definitions 13)
Field Entry Event (FEE);
14)
3.1 Global OS1 definitions
Field Entry Instruction (FEI);
15)
Field Entry Instruction Control Object (FEICO);
1 6)
This part of ISOlIEC 9041 is based on the concepts developed
Field Entry Instruction Record (FEIR);
17)
in ISOlIEC 7498, and makes use of the following terms defined
in it:
18) Field Entry Pilot Control Object (FEPCO);
1) application entity;
Field Entry Pilot Record (FEPR);
19)
2) application layer;
Field Entry Reaction (FER);
20)
3) protocol data unit;
f U I I-VTE ;
21 1
4) user element.
Initial Facility Set;
22)
neteff ecting ;
23)
Definitions of the following terms are given in ISOllEC 10731:
Reference Information Object (RIO);
24)
5) primitive;
repertoire;
25)
6) confirm (primitive);
26) ripple.
7) indication (primitive);
S-mode, Synchronous Mode;
27)
8) request (primitive);
Terminal VT-user;
28)
9) response (primitive);
Transmission Policy Control Object UPCO);
29)
10) service provider;
VT-association;
30)
11) service user.
VTcontext-value;
31 1
3.2 Association Control Service Element 32) VT-environment (VTE);
definitions
VT-user;
33)
VTE-parameter;
34)
This part of ISOlIEC 9041 makes use of the following terms
defined in ISOllEC 8649:
3.5 Virtual Terminal Protocol definitions
1) application association;
2) application context.
For the purposes of this part of ISOlIEC 9041 the following
definitions apply.
3.3 Presentation Layer Service Element
3.5.1 protocol element: An abstract unit of information,
def i nit ion
defined in clause 6, communicated between peer VTPMs, that
-
maps
This part of ISOllEC 9041 makes use of the term abstract
syntax which is defined in ISOlIEC 8822.
a) directly to an ACSE or presentation service primitive;
andlor
3.4 Virtual Terminal Service definitions
b) to a PDU type that is conveyed by a user information
This part of ISOllEC 9041 uses the following definitions con- parameter of ACSE or a user data parameter of the pres-
tained in ISOllEC 9040:
entation service.
A-mode, Asynchronous Mode;
3.5.2 initiating VTPM: The VTPM that initiates an individual
access-rule;
procedure.
Application VT-user;
3.5.3 target VTPM: The VTPM to which the protocol element
Block;
initiating a procedure is directed.
character-box graphic element;
Context Control Object (CCO); 3.5.4 sending VTPM: The initiating VTPM for a data transfer
procedure.
current-VTE;
d raft-VTE ;
3.5.5 receiving VTPM: The target VTPM for a data transfer
Field; procedure.
1) Available from the European Computer Manufacturers Association (ECMA), 114 Rue du Rhbne, CH 1204 GenBve, Switzerland.
O ISO/IEC ISOAEC 9041 -1 :1997(E)
All those re-
3.5.6 dynamic conformance requirements:
ASN.l Abstract Syntax Notation One
quirements (and options) which determine what observable
PAB Provider Abort
behaviour is permitted in instances of communication.
PDU Protocol Data Unit
3.5.7 static conformance requirements: Constraints
Protocol Implementation
PICS
which facilitate interworking by defining the requirements for
Conformance Statement
kernel sets of capabilities of an implementation.
TWA Two-way Alternate
3.5.8 protocol implementation conformance statement
TWS Two-way Simultaneous
(PICS): A statement made by the supplier of an implementa-
VTP Virtual Terminal Protocol
tion which states the capabilities and options which have been
implemented, and any features which have been omitted.
VTPM Virtual Terminal Protocol Machine
3.5.9 VT-token: A single entity which maps onto all of the
4.3 VT Protocol elements
available session tokens provided by the Presentation Layer.
If there are no session tokens available then both sides are
VT-P-ABORT
AW
considered to hold this token.
ASQ VT-ASSOC IATE- R EQ
VT-ASSOC IATE-R ESP
ASR
4 Abbreviations
AUQ VT-U-ABORT
BKQ VT-BREAK-REQ
4.1 Virtual Terminal Service abbreviations
BKR VT-BREAK-RESP
A-mode Asynchronous Mode
VT-ACK-RECE IPT
DAQ
ACS Access Control Store
DLQ VT-DELIVER
CCA Conceptual Communication Area
ENQ VT-END-NEG-REQ
cco Context Control Object
ENR VT-END-NEG-RESP
CDS Conceptual Data Store
EXQ VT-P-EXCEPTION-REQ
CO Control Object
VT-P-EXCEPTION-RESP
EXR
CSS Control, Signal and Status Store
GTQ VT-GIVE-TOKEN
Do Display Object
HW VT-H IG H-PR I -DATA
DSD Data Structure Definition
NAQ VT-N EG -ACCE PT
FDCO Field Definition Control Object
VT-DATA
NW
FDR Field Definition Record
N IQ VT-NEG-INVITE
FEC Field Entry Condition
NJQ VT-NEG-REJECT
FEE Filed Entry Event
VT-N EG -OFFER
NOQ
FEI Field Entry Instruction
RLQ VT-RELEASE-REQ
FEICO Field Entry Instruction Control Object
RLR VT-RELEASE-RESP
FER Field Entry Instruction Record
RTQ VT-REQUEST-TOKEN
Field Entry Pilot Control Object
FEPC0
SNQ VT-START-N EG-R EO
FEPR Field Entry Pilot Record
SN R VT-START-NEG-RESP
FER Field Entry Reaction
SW VT-SWITCH-PROFILE-REQ
MIN Multiple Interaction Negotiation
VT-SW ITCH-PROFILE-RESP
RIO Reference Information Object SPR
S-mode Synchronous Mode UDQ VT-URGENT-DATA
TPCO Transmission Policy Control Object
VT Virtual Terminal
5 Overview
VTE Virtual Terminal Environment
VTS Virtual Terminal Service
5.1 Virtual Terminal Service summary
4.2 Miscellaneous
The protocol specified in this part of ISOAEC 9041 provides
ACSE Association Control Service the Basic Class Virtual Terminai Service defined in ISOllEC
9040. The VT-service primitives are listed in table 1.
Element
ISO/IEC 9041-1 :1997(E) O ISO/IEC
Table 1 - Virtual Terminal Service Primitives
Service Parameters
Service Primitive
VT-ASSOCIATE request Called Application Entity Title
indication Calling Application Entity Title
VT-cl ass
VTf unctional- units
VT-mode
VT- WAVAR-owner
VT-profile-name
VT-profi le-arg-off er-list
response Res onding Application Entity Title
confirm VT-P unctional-units
VT- WAVAR-owner
VT-Drofile-am-value-list
VT-result -
VT-user-failure-reason (confirm onlv)
VT-P-ABORT indication VT-reason
VT-RELEASE request
indication
VT- res ult
response
confirm VT-user-fai Iure-reason
VT-provider-failure-reason (confirm only)
VT- U- A BO RT request VT-user-failure-reason
indication
VT- DATA request VT-echo-now
(excluding the two indication VT-start-entry
following cases
VT-object-update
VT-object-descriptor
VT-obrect-data
VT-DATA request VT-object-update
(high priority Control indication VT-object-descri ptor
Objects only) VT-object-data
~~ ~~
VT-DATA request VT-o bj ec t -u pd ate
(urgent priority Control indication VT-object-descriptor
Objects only) VT-object-data
VT-DELIVER request VT-ack-request
indication
VT-ACK-RECEIPT
request
indication
VT-G IVE-TOKEN
request
indication
~
VT-REQUEST-TOKEN request
indication
I
ISO/IEC 9041-1 :1997(E)
O ISO/IEC
Table 1 (concluded)
Service Parameters
VT-S W ITC H - PROFI LE request VT- profil e-name
indication VT-profil e-arg-off er-I ist
VT-o bject-retention-list
response VT-profile-arg-value-list
confirm VT-result
VT-user-fail ure-reason
VT-provider-failure-reason (confirm only)
VT-object-retention-list
~~
VT-START-N EG request VT- prof il e-name
indication VT- profil e-arg-off er-I ist
response VT-profil e-arg-value-list
confirm VT-resul t
L VT- user-fai I u re- reason
VT-provider-failure-reason (confirm only)
VT-END-NEG request VT-vte-choice
indication VT-vte-fai lure-al lowed
VT-object-retention-list
VT-vte-Cho ice
resppnse
confirm VT-resul t
VT-user-failure-reason
VT-provider-failure-reason (confirm only)
VT-object-retention-list
VT-NEG-INVITE request VT-param-ident-list
indication
1 VT-NEG-OFFER request VT- param-off er-I ist
indication
VT-N EG-ACCE PT VT-param-value-list
request
indication
tVT-NEG-REJECT request VT-param-ident-list
indication
VT- BREAK request VT-token
indication VT-informati on
response VT- to ke n
confirm VT- i nf ormati on
I VT-P-EXCEPTION indication VT-exception-source
VT-except ion-type
VT-information
O ISOllEC
ISOAEC 9041-1 :1997(E)
The CCA is conceptually accessed by VT-users via service
5.2 Model
primitives in which information is transferred to or from the
VT-users. Each VTPM is modelled as having its own CCA, see
The Basic Class Virtual Terminal Protocol operates between
figure 1. These two CCAs constitute the VT context referred
two Virtual Terminal Protocol Machines (VTPMs) in the Appli-
to in the Basic Class VTS definition. Each VTPM may also
cation layer of the OS1 model. Protocol elements are ex-
maintain a reset context which preserves the contents of all
changed between these, using the services of Association
Dos and COS as they existed at the time the current VTE was
Control and of the Presentation layer as defined in ISO/IEC
established. This is used to provide the VTcontext-value after
8649 and ISO/IEC 8822.
completion of the break procedure, see 8.8.
The VT service is modelled as a single Conceptual Commu-
5.3 Service assumed from the Presentation
nication Area which is accessible to two communicating serv-
ice users and which contains all the necessary information to
Layer
allow these VT-users to derive a consistent view of the Virtual
Devices which constitute the Virtual Terminal. The CCA is
The protocol specified in this part of ISO/IEC 9041 assumes
partitioned into four sub-areas:
the use of the Presentation Service defined in ISO/IEC 8822.
Information is transferred to and from the Presentation service
a) a conceptual data store (CDS) containing one or more
provider in the primitives listed in table 2.
display objects;
b) a control, signaling and status store (CSS) containing a
5.4 Service assumed from ACSE
number of control objects;
The protocol specified in this part of ISO/IEC 9041 assumes
c) an access control Store (ACS);
the use of the Association Control service defined in ISOllEC
8649. Information is transferred to and from ACSE in the
d) a data structure definition (DSD) which parametrically de-
service primitives listed in table 3.
fines the structure of the CDS and CSS.
CCA
I
\ IT VT
VI
BASIC CLASS VIRTUAL
PROTOCOL
PROTOCOL
TERMINAL PROTOCOL
MACH I NE
MACHINE
(CLASS:BASIC)
(CLASS: BASIC)
I I
I
PSAP PSAP
PRESENTATION LAYER
Figure 1 - Model
ISOAEC 9041 -1 :1997(E)
O ISOllEC
d) either an initial VTE is agreed or it is agreed that the
VT-environment will be negotiated later before any data is
Table 2 - Presentation Service primitives
transferred.
~~
5.5.2 Association Termination
primitives
Presentation service
The purpose of VT-association Termination is to cause the
P-DATA request
VT-association to cease to exist.
indication
5.5.3 Negotiation
request
P-EXPEDITED-DATA
indication
Negotiation provides a mechanism by which the VT-users and
request
P-RESYNCHRON IZE VTPMs can agree upon the VT-environment to be used. Two
indication
forms of negotiation are supported, a single interaction profile
response
switch and a multiple interaction dialogue.
confirm
5.5.4 Data Transfer
P-SYNCHRON IZE-MAJOR request
indication
The purpose of Data Transfer is the sending, from one VTPM
response
to the other, of structured data representing operations upon
confirm
an object or objects in the CCA defined in the virtual terminal
model.
P-TOKEN-GIVE request
indication
5.5.5 Delivery Control
P-TOKEN-PLEASE request
The purpose of Delivery Control is:
indication
a) to allow the VT-user sending data to indicate points at
request
P-WPED-DATA
which operations on VT objects conceptually take effect;
indication
b) to allow the receipt of such a delivery point indication to be
acknowledged:
Table 3 - ACSE service primitives
c) to allow data which update objects with the Same access
~~
rules to be grouped together and simultaneously be made
primitive
ACSE service available to the VT-user.
A-ASSOC IATE request
5.5.6 Dialogue Management
indication
response
Dialogue Management provides the VT-users with access to
confirm
the lower layer functions. This dialogue management enforces
TWA discipline on the sending of some data and on the
request
A-RELEASE
exercise of some control functions.
indication
response
5.5.7 Error Handling
confirm
Error Handling permits detection of noncompliance with the
A-ABORT request
protocol, reception of error indications from other service
indication
providers and the taking of appropriate action. The errors
cause the association to be terminated with an appropriate
indication
A-P-ABORT
error indication (identifying the source of error).
NOTE - The procedure for Error Handling is included with that for
unconditional termination of an association.
5.5 Functions of the VT Protocol
5.5.8 Interrupt
5.5.1 Association Establishment
Two interrupt functions are provided. The first is a non- de-
The purpose of VT-association establishment is to establish a
structive mechanism which allows priority information to be
VT-association between two VT-users such that:
exchanged between the VT-users outside the normal dataflow
without disrupting that data flow. The second is a destructive
a) the use of this VT-protocol is confirmed:
mechanism which allows a VT-user unconditionally to bring
the current dialogue to a halt. Information is exchanged be-
b) the required dialogue discipline is agreed;
tween the VT-users to enable them to resynchronize their
operations.
c) a suitable transfer syntax is used:
ISOlIEC 9041 -1 :1997(E) O ISOllEC
the access-rules associated with the objects affected by the
5.5.9 Exceptions Handling
elements.
Exceptions Handling permits the VT service provider to advise
the VT-users of certain non-fatal exception conditions arising
during the operation of a VT-association without terminating
6 Protocol elements
the VT-association.
Table 4 lists the elements of the Virtual Terminal Basic Class
5.6 Protocol functional units
protocol with the associated VT service and a cross reference
to the clause where the protocol element is further described.
This part of ISO/IEC 9041 defines the following functions
The description includes, for each element, its purpose and a
which are available in the Basic Class Virtual Terminal Proto-
list of its parameters.
col independently of which functional units have been se-
lected:
Table 4 - VT protocol elements
a) Association Establishment;
b) Association Termination;
Protocol VT service Cross
c) Data Transfer;
referencc
element
d) Delivery Control (optional, see Note 1);
VT-ASSOCIATE 6.2
ASQ
e) Dialogue Management (S-mode only);
ASR VT-ASSOCIATE 6.3
f) Error Handling.
AW VT-P-ABORT 6.1
VT- U -AB0 RT
AUQ 6.4
NOTE 1 - Use of delivery-control is controlled at the level of VTE-pro-
RLQ VT-RELEASE 6.18
file by a VTE-parameter.
R LR VT-RELEASE 6.19
This part of ISO/IEC 9041 also defines seven functional units
HDQ VT-DATA (high priority) 6.12
of the Basic Class Virtual Terminal Protocol which correspond
VT-DATA (normal) 6.14
NDQ
to the similarly named service functional units which are
VT-DATA (urgent priority)
UDQ 6.25
defined in ISOllEC 9040. The following functions are available
only if the corresponding functional unit has been selected:
VT-ACK- RE CE I PT 6.7
DAO
g) Switch Profile Negotiation;
DLQ VT-DELIVER 6.8
h) Multiple Interaction Negotiation;
VT-G IV E -TOK EN
GTQ 6.1 1
i) Negotiated Release;
RTQ VT-REQU EST-TOKEN 6.20
j) Break;
VT-BREAK 6.5
BKQ
k) Urgent Data;
BKR VT-BREAK 6.6
EXQ VT-P-EXCEPTION 6.26
I) Reference Information Objects;
VT-P-EXCEPTION 6.27
EXR
m) Exceptions.
VT-SWITCH-PROFI LE 6.23
SPQ
The Multiple Interaction Negotiation functional unit may only
VT-SW ITCH-PROFI LE
SPR 6.24
be selected if the Switch Profile functional unit is also selected.
The Exceptions functional unit may only be selected if the
VT-END-NEG
ENQ 6.9
Break functional unit is also selected.
ENR VT-END-NEG 6.10
VT-N EG -ACCE PT 6.13
NAQ
NOTE 2 - Serviœ functional units defined in ISO/IEC 9040 but not
VT-NEG- I NVlTE
NIQ 6.15
included above do not affect the protocol procedures but may affect
VT-N EG-R EJECT 6.16
NJQ
the allowed content of some protocol elements as defined in later
VT-N EG -0FFE R 6.17
NOO
clauses.
SNQ VT-START-NEG 6.21
SN R VT-START-NEG 6.22
5.7 Modes of operation
The protocol operates in two modes: Asynchronous and Syn-
Procedures specifying the use of the elements are specified
chronous. In the Synchronous mode (S-mode) the presenta-
in clauses 7 through 10 and their mapping to the presentation
tion connection supporting the VT communication is treated
service or ACSE and their ASN.l structure are specified in
as a TWA connection, and the VTPMs send normal update
clauses 11 and 12.
data to each other alternately. In the Asynchronous mode
(A-mode) the presentation connection is treated as a TWS In some implementations it may not be possible to provide the
connection, and the VTPMs are not restricted in the exchange
parameters of the APQ and AUQ protocol elements. This is
of data. due to possible length limitations in the supporting services.
Consequently, the decision whether to send these parameters
is a local one based upon a knowledge of the capability of the
5.8 Access control
supporting services. For the Same reason the parameters of
The initiation and reception of some protocol elements by a
other protocol elements, while they may be sent, may be
VT-user is conditional upon the location of the token and upon
restricted as to their complexity. These latter are:
ISO/IEC 9041 -1 :1997(E)
O ISOllEC
a) ASQ;
3) Negotiated Release,
b) ASR;
4) UrgentData,
c) SNQ;
5) Destructive Break,
d) SNR;
6) Enhanced Access-rules,
e) SW;
7) Structured Control Objects (Structured COS),
r) SPR;
8) Blocks,
9) UDQ.
9) Fields,
10) Reference Information Objects (RIOS),
NOTE -In the following sub-chuses the prefix VT- is used where there
is a service parameter in ISO/IEC 9040 with the same name. 11) Ripple,
12) Exceptions,
6.1 APQ (VT-P-ABORT)
13) Context Retention;
6.1.1 Purpose
i) protocol-version: For the initiating VTPM this is a variable
length bit string where each bit set to one indicates that the
To force unconditional termination of the VT-association (initi-
corresponding version of the protocol is supported. Bit O
ated by the VTPM).
represents the first version, bit 1 represents the second,
etc. Multiple bits may be set indicating support of multiple
6.1.2 Parameter
versions. No trailing bits higher than the highest version of
VT-reason: Optional, if present takes one of the values this standard that the VTPM supports shall be sent, i.e., the
last bit of the string must be set to one. The receiving VTPM
"local error" or "protocol error".
shall ignore trailing bits higher than the one indicating the
latest version of this part of ISOllEC 9041 that it supports;
6.2 ASQ (VT-ASSOCIATE-REQ)
j) implementation-identifier: Optional, allows implementors to
6.2.1 Purpose
identify their implementation and its version for mainte-
nance purposes.
To request establishment of a VT-association.
6.2.2 Parameters
6.3 ASR (VT-ASSOCIATE-RESP)
a) called-application-entity-title: Specifies the application en-
6.3.1 Purpose
tity with which a VT-association is to be established;
To complete or refuse establishment of a VT-association.
b) calling-application-entity-title: Identifies the application en-
tity initiating the VT-association;
6.3.2 Parameters
to be provided;
c) VT-class: Specifies the VT service class
a) responding-application-entity-title: Identifies the applica-
takes the value "Basic" to invoke the service specified in
tion entity which is responding to a VT-association request;
lSO/l EC9040;
b) VT-WAVAR-owner: As in 6.2 except that the value "ac-
NOTE - The use of other values of this parameter for the invocation
ceptor chooses" is not allowed. Only present if the ASQ
- of other International Standards is outside the scope of ISOllEC 9041.
parameter was "acceptor chooses";
d) VT-mode: specifies whether A-mode or S-mode will be in
c) VT-profile-arg-value-list: If present, a list of parameters with
effect when the asmiation is established and whether
unique values of each parameter selected from the list OT
mode switching is to be permitted;
range of values in the profile argument offer list; not present
e) VT-WAVAR-owner: Defines which side of the dialogue will
if the value of VT-result is "failure", see also 6.2.2 g):
initially own the WAVAR token if this exists; takes one of
d) VT-result: Takes one of the values "success", "success-
the values "initiator-side", "acceptor-side", or "acceptor-
or "failure";
with-warning"
chooses"; omitted if WAVAR does not exist;
e) failure-reason: Conveys either a text string supplied by the
f) VT-profile-name: If present, the name of the profile (see
responding VT-user or one of the values "VTE-incomplete",
ISO/IEC 9040); if absent, the default profile defined in
VTE-parameter-not-supported", "VTE-parametercombi-
ISO/IEC 9040 for A-mode or for S-mode, as selected by
nation-not-supported", or "VTE-profile-not-supported";
the VT-mode parameter, is used;
f) protocol-version: In the case of successful establishment
g) VT-profile-arg-offer-list: if present, a list of items in which
this is similar to the corresponding item in 6.2.2 except that
each profile argument under negotiation is either a value,
only a single bit may be set to one. This bit selects the
list of values or range of values: omitted if the profile
version of the protocol which will be used during the asso-
identified by VT-profile-name has no profile arguments;
ciation. If the VT-result value is "failure" this bit string
h) VT-functional-units: If present, specifies the proposed func-
indicates the protocol version(s) of this part of ISOllEC
tional units of the current VT service class; takes one or
9041 that can be supported by the rejecting VTPM;
more values from the following list:
g) VT-functional units: As in 6.2.2 h);
1) Profile Switch,
h) implementation-identifier: As in 6.2.2 j).
2) Multiple Interaction Negotiation,
O ISOllEC
ISO/IEC 9041 -1 :1997(E)
6.9.2 Parameters
6.4 AUQ (VT-U-ABORT)
a) VT-vtechdce: Takes one of the values
6.4.1 Purpose
"draft", "current" or "either":
To force unconditional termination of the VT-association (initi-
b) VT-failure-allowed: Optional, if present takes one of the
ated by the VT-user).
values 'yes" or 'no";
6.4.2 Parameters
c) VT-object-retention-list: Optional, if present contains a list
of DO and CO names whose contents are requested to be
VT-user-failure-reason: optional; user provided text string.
retained.
6.5 BKQ (VT-BREAK-REQ)
6.10 ENR (VT-END-NEG-RESP)
6.5.1 Purpose
6.10.1 Purpose
To request a destructive priority interrupt to be indicated to the
remote VT-user by the remote VTPM.
To respond to a request to terminate negotiation.
6.5.2 Parameters
6.1 0.2 Parameters
a) VT-WAVAR-owner: can take one of the values "initiator-
a) VT-vtechoice: Optional, if present takes one of the values
side", "acceptor-side" or "acceptor-chooses"; omitted if
"draft' or "current";
WAVAR does not exist;
b) VT-result: Takes one of the values "success",
b) VT-information: Items as defined in ISOlIEC 9040.
"success-with-warning "or "failure" :
6.6 BKR (VT-BREAK-RESP)
c) VT-user-failure-reason: Optional user provided text string;
d) VT-provider-failure-reason: Optional, if present takes the
6.6.1 Purpose
value "VTE-incomplete";
To acknowledge to the remote VTPM that a destructive priority
e) vt-object-retention-list: Optional, if present contains a list of
interrupt was indicated to the local VT-user.
DO and CO names whose contents are agreed to be
6.6.2 Parameters retained.
a) VT-WAVAR-owner: can take one of the values "initiator-
6.1 1 GTQ (VT-GIVE-TOKEN)
side" or "acceptor-side"; omitted if WAVAR does not exist:
9040.
b) VT-information: Items as defined in ISOlIEC
6.11.1 Purpose
6.7 DAQ (VT-ACK-RECEIPT) To pass all defined session tokens to the peer VTPM.
6.7.1 Purpose
6.1 1.2 Parameters
To acknowledge a delivery point identified by the receipt of a
None.
DLQ.
6.12 HDQ (VT-HIGH-PRI-DATA)
6.7.2 Parameters
None. 6.12.1 Purpose
To convey updates to Control Objectsfor which the CO-priority
6.8 DLQ (VT-DELIVER)
VTE-parameter has the value "high".
6.8.1 Purpose
6.1 2.2 Parameters
To designate delivery points in the stream of NDQ PDUs and,
if required, to request acknowledgement of receipt. object updates: A sequence of zero or more data items.
Each data item is a (CO-name, object update) pair. Each
6.8.2 Parameters
CO-name identifies a Control Object; the corresponding
object update identifies permitted updates to that object.
VT-ack-request: A single boolean indicating whether or not
The permitted updates to Control Objects are defined in
an acknowledgement is explicitly required.
ISOllEC 9040.
6.9 ENQ (VT-END-NEG-REQ)
6.13 NAQ (VT-NEG-ACCEPT)
6.9.1 Purpose
6.13.1 Purpose
To request the synchronized termination of a multiple interac-
To select values for one or more of the VTE-parameters
tion negotiation and to cause a transition to the data handling
specified in a previous VT-NEG-OFFER protocol element.
phase.
ISO/IEC 9041 -1 :1997(E)
O ISOllEC
6.1 8 RLQ (VT-RELEASE-REQ)
6.1 3.2 Parameters
VT-param-value-list: A list of VTE-parameters and corre-
6.1 8.1 Purpose
sponding values for those parameters selected from the
alternatives specified in a previous VT-NEG-OFFER.
To request the orderly termination of a VT-association.
6.18.2 Parameters
6.14 NDQ (VT-DATA)
None.
6.14.1 Purpose
6.1 9 RLR (VT-RELEASE-RESP)
To update objects in a "controlled" manner and, for A-mode,
to indicate if echoing or data entry may take place following
6.19.1 Purpose
processing of a data item.
To accept or reject a request for orderly termination of a
6.14.2 Parameters
VT-association.
object updates: A sequence of zero or more data items.
a)
6.1 9.2 Parameters
Each data item is a (object name, object update) pair. Each
object name identifies a Display Object, Control Object or
a) VT-result: Takes one of the values "success' or "failure".
RIO; the corresponding object update identifies permitted
L
The value "failure" may only be used if the Negotiated
updates to that object. The permitted updates to objects are
Release Session functional unit was successfully negoti-
defined in ISO/IEC 9040;
ated in the Session Requirements parameter of the A-AS-
SOCIATE, see 11.1.1;
b) echo-now: If present, takes the value "echo";
b) failure-reason: Conveys either a text string provided by the
start-entry :If present, takes the value "start-entry".
C)
responding VT-user or the value "collisiondetected' when
the failure is determined by the VTPM.
6.1 5 NIQ (VT-NEG-INVITE)
6.20 RTQ (VT-REQUEST-TOKEN)
6.15.1 Purpose
6.20.1 Purpose
To request the peer to provide values for specified VTE-pa-
rameters once an agreement to enter into multiple interaction
To request possession of all defined Session tokens.
negotiation has been reached.
6.20.2 Parameters
6.1 5.2 Parameters
None.
VT-param-ident-list: The names of VTE-parameters for
which values are to be provided.
6.21 SNQ (VT-START-NEG-REQ)
L 6.1 6 NJQ (VT-NEG-REJECT)
6.21 .I Purpose
6.16.1 Purpose To request the establishment of the Negotiation Active phase.
6.21.2 Parameters
To reject VTE-parameters contained in previous NOQs whose
values and/or value ranges are unacceptable.
a) VT-profile-name: As in 6.2.2 f);
6.16.2 Parameters
b) VT-profile-arg-offer-list: As in 6.2.2 9).
VT-param-ident-list: The names of VTE-parameters whose
S N R (VT-START-N EG-R ES P)
6.22
values are being rejected.
6.22.1 Purpose
6.1 7 NOQ (VT-NEG-OFFER)
To indicate success or failure of the attempt to establish the
Negotiation Active phase.
6.17.1 Purpose
6.22.2 Parameters
To pass a list of VTE-parameters and parameter values, lists
of values, or value ranges to the peer once an agreement to
a) VT-profile-arg-value-list: As in 6.3.2 cl;
enter into multiple interaction negotiation has been reached.
b) VT-result: Takes one of the values "success' or "failure";
6.17.2 Parameters
c) failure-reason: Conveys either a text string supplied by the
responding VT-user or one of the values "collisionde-
VT-param-offer-list: A list of VTE-parameters and corre-
tected" or "profile-not-suppd".
sponding values, lists or ranges for those parameters.
ISOAEC 9041 -1 :1997(E) O ISOllEC
b) VT-information: Takes a value as defined in ISO/IEC
6.23 SPQ (VT-SWITCH-PROFILE-REQ)
9040.
6.23.1 Purpose
6.27 EXR (VT-P-EXCEPTION-RESP)
To negotiate a switch to a new full-VTE constructed from a
named VTE profile.
6.27.1 Purpose
6.23.2 Parameters
To acknowledge an EXQ.
a) VT-profile-name: As in 6.2.2 f);
6.27.2 Parameters
b) VT-profile-arg-offer-list: As in 6.2.2 9);
None.
VT-object-retention-list: if present contains a list of DO and
c)
CO names whose contents are requested to be retained.
6.24 SPR (VT-SWITCH-PROFILE-RESP)
7 Procedures
6.24.1 Purpose
The procedures of the Basic Class VTP are specified in
Clauses 8 to 10 as sequences of actions performed by the
To indicate success or failure of the negotiation attempt.
peer VTPMs. The sequences are presented in tabular form,
..
6.24.2 Parameters
indicating
a) VT-profile-arg-value-list: As in 6.3.2 c);
a) Step: numerical order in the sequence; when a sequence
branches, the first step in each branch is suffixed with a
b) VT-result: Takes one of the values "success" or "failure";
different letter
...