ISO/IEC 9041-1:1997
(Main)Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Protocol — Part 1: Specification
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
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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)
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ISOAEC 9041-1 :i 997(E)
Con tents
1 Scope .
1
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
3
4.1 Virtual Terminal Service abbreviations .
4.2 Miscellaneous . 3
3
4.3 VT Protocol elements .
5 Overview . 3
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
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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
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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 .
40
12.4 Control. Signal and Status definitions . 44
12.5 Device Object definitions . 47
13 Conformance . 50
13.1 Dynamic conformance requirements .
50
13.2 Static conformance requirements . 50
13.3 Protocol Implementation Conformance Statement (PICS) .
50
Annex A StateTables . 51
A.l General . 51
A.2 Parameters. VTPM rights and variables .
51
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
.
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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.
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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
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~~~
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.
1
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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.
2
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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
3
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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
4
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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
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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
6
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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:
7
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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
...
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