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INTERNATIONAL
7776
STANDARD
First edition
1986-12-1 5
AMENDMENT 1
1992-1 2-15
Information processing systems - Data
communication - High-level data link control
procedures - Description of the X.25 LAPB-
compatible DTE data link procedures
AMENDMENT 1: Conformance requirements
Systèmes de traitement de l'information - Communication de données -
Procédures de commande de liaison de données à haut niveau -
Description des procédures de liaison d'équipement terminal de
transmission de données E7TD compatible X.25 LAP8
AMENDEMENT 1: Exigences de conformité
Reference number
IS0 7776:1986/Amd.l:1992 (E)
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IS0 7776 : 1986lAmd.l : 1992 (E)
Foreword
IS0 (the International Organization for Standardization) and IEC (the International
Electrotechnical Commission) form the specialized system for worldwide standardization.
National bodies that are members of IS0 or IEC participate in the development of
International Standards through technical committees established by 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, ISOAEC JTC 1. 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 bodies casting a vote.
Amendment 1 to International Standard IS0 7776 : 1986 was prepared by Joint Technical
Committee ISO/IEC JTC 1, Information Technology.
O ISO/IEC I992
All rights rcscrvcd. Uiilcss ohxwisc spccificd, no part of this publication inay hc rcproduccd or utilized
in tiny i'oriii or by any nieans, electronic or iiiccliaiiical, including photocopying and iiiicrolïliii, without
permission in writing from tlic publisher.
ISO/IEC Copyright Oïlïcc Case postale 56 CH-121 I Genève 20 Switzcrlaiid
Priiitcd in Switzcrlaiid
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ISQ 7776 : 1986lAmd.l : 1992 (E)
Introduction
Amendment 1 to IS0 7776:1986 introduces changes that have been agreed since the
approval of IS0 7776.
Amendment 1 to IS0 7776:1986 introduces:
-
an additional section in clause O, Introduction, concerning conformance;
- an additional section in clause 1, Scope and field of application, describing what the
new clause 7, Conformance, covers;
- two new references in clause 2, References, on conformance testing;
- a new clause 7 on conformance to this International Standard;
- a new annex A (normative) containing a Protocol Implementation Conformance
Statement proforma (PICS proforma), for IS0 7776 Single Link Procedures and
Multilink Procedures. This proforma will be completed by the provider of a
particular implementation of the IS0 7776 International Standard in order to inform
the user of the (permitted) options chosen in this realisation of the International
Standard.
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IS0 7776 : 19861Amd.l : 1992 (E)
Information processing systems - Data communication -
High-level data link control procedures - Description of the
X.25 LAPB-compatible DTE data link procedures
AMENDMENT 1: Conformance requirements
Page 1
Clause O
Last paragraph, change "An Annex" to "Annex B".
Page 1
Clause O
Add the following paragraph to the end of clause O:
" To evaluate conformance of a particular implementation, it is necessary to have a statement of which capabilities and options have been
implemented. Such a statement is called a " Protocol Implementation Conformance Statement" (PICS). as defined in ISO/IEC 9646-1. This
International Standard provides such a PICS proforma in compliance with the relevant requirements, and in accordance with the relevant
guidance, given in ISO/iEC 96462.
Page 2
Clause 1
Add the following paragraph to the end of clause 1:
"Clause 7 covers the Static Conformance requirements, the Dynamic Conformance requirements, and the Protocol Implementation
Conformance Statement (PICS)."
Page 2
Clause 2
Add the following two references:
"ISOflEC 9646-1: 1991, Open Systems Interconnection - Conformance testing methodology and framework - Part 1: General concepts.
ISO/iEC 9646-2: 1991, Open Sysrems Interconnection - Conformarice resting methodology and framework - Part 2: Abstract test suite
specification."
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IS0 7776 : 1986/Amd.l : 1992 (E)
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Add a new clause 7 as follows:
7 Conformance
7.1. Static conformance
7.1.1. General requirements
A DTE that claims conformance to this International Standard shall implement:
a) Single link operation;
A (ie, A sent in response frames), and may implement operation with DTE address B, for DTEDTE
b) operation with DTE address
application;
c) either basic (modulo 8) operation or extended (modulo 128) operation, and may implement both (3);
d) link set-up as responder to a set-up initiated by the DCE/remote DTE (5.3.1);
e) link disconnection as responder to a disconnection initiated by the DCE/remote DTE (5.3.3);
fj link reset as responder to a reset initiated by the DCE/remote DTE (5.6.1);
g) information transfer, in both directions (5.2,5.4,5.4.1,5.4.2,5.4.3,5.4.4, 5.4.5,5.4.6,5.4.7,5.4.9):
h) sending of FRMR response on receipt of a valid frame with an error condition not recoverable by retransmission of the identical frame
(4.3.9,5.5);
j) responding to receipt of a FRMR response in the information transfer phase either by initiating link reset, or by transmitting a DM
response and entering the disconnected phase (5.5);
k) timer T1 (5.7.1.1), and parameter N2 (5.7.2);
1) interframe time fill by contiguous flags (3. IO).
7.1.2 Options
A DTE that claims conformance to this International Standard niay implement:
a) multilink operation (clause 6);
b) operation with DTE address B for DTE/DTE applications:
c) link set-up as initiator (5.3.1);
d) link disconnection as initiator (5.3.3);
e) link reset as initiator (5.6. I);
f) DTE busy condition (5.4.8);
g) timers T3 (5.7.1.3) and T4 (5.7.1.4);
h) transmission of unsolicited DM response frames in disconnected phase (5.3.4);
j) transmission of DISC frames prior to link set-up (5.3.1).
7.2. Dynamic conformance
For each function that the PICS states to be supported, the implementation shall exhibit external behaviour consistent with the
implementation of
a) the corresponding data link layer procedures and
b) the encoding specified in clause 3,4.1,4.3,4.3.9 and 5.1 for all relevant fields of any transmitted frames.
as specified in the clauses to which the PICS proforma entry for the function refers.
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IS0 7776 : 1986/Amd.l : 1992 (E)
7.3 Protocol Implemeiitatioii Conformance Statement
The supplier of a protocol implementation that is claimed to conform to this International Standard shall complete a copy of the PICS
proforma in annex A, including the information necessary to identify fully both the supplier and the implementation.
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Rename the present annex as annex B an insert a new annex A as follows:
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IS0 7776 : 1986/Amd.l : 1992 (E)
ANNEX A*
(normative)
PICS Proforma
A.1 Introduction
The supplier of a protocol implementation which is claimed to conform to IS0 7776 shall complete the following Protocol Implementation
Conformance Statement (PICS) proforma.
A completed PICS proforma is the PICS for the implementation in question. The PICS is a statement of which capabilities and options of the
protocol have been implemented. The PICS can have a number of uses, including use:
- by the protocol implementor, as a check-list to reduce the risk of failure to conform to the standard through oversight;
- by the supplier and acquirer - or potential acquirer - of the implementation, as a detailed indication of the capabilities of the
implementation, stated relative to the common basis for understanding provided by the standard PICS proforma;
- by the user - or potential user - of the implementation, as a basis for initially checking the possibility of interworking with
another implementation (note that, while interworking can never be guaranteed, failure to interwork can often be predicted from
incompatible PICS'S);
- by a protocol tester, as the basis for selecting appropriate tests against which to assess the claim for conformance of the
implementation.
and special symbols
A.2 Abbreviations
A.2.1 Status symbols
M mandatory
O optional
0.n optional, but support of at least one of the group of options labelled by the same numeral n is required
X prohibited
dein>: conditional symbol, status is dependent on the support marked for (see A.3.4)
A.2.2 General abbreviations
NIA not applicable
PICS Protocol Implementation Conformance Statement
A.2.3 Item references
The following is a list of the item references used in the PICS proforma
Major capabilities, AS: Ls, Lm, Lc, Lt, Lta
Basic I extended operation, A.6.1: M8, M128
Link setup, A.6.2: LSIl, LSI2, LS13, LSA, LSD, LSR
Link disconnection and disconnected phase: LD I, LD2, LDP
Link reset, A.6.2: LRI1, LRIb, LRIc, LRId, LRRa, LRRb, LRRc, LRRd, LRA, LRD
Collision resolution for U frames, A.6.2: LCRa, LCRb, LCRc, LCRd, LCRe
I-frame transmission, A.6.3: IT, ITS, ITCi, ITCs, ITRJ, ITB
I-frame reception, A.6.3: IR, IRs, IRRJ, IRB
Frame rejection, A.6.3: FR 1, FR2
Frame formats, A.6.4:
Fla,Flb,Flc,F2, F2a, F2b, F2c,F2d,F2e,F3, F4, FD, FA,FF
Timers, etc., A.6.5: Tla, Tlb, Tlc, Tld, Tle, Tlf, Tlg, N2a, N2b,T3, T4
System parameters, A.6.6: SPT1. SPT2, SPT3, SPT4, SPN2, SPN1, SPk
*) Copyright release for PICS proforiiias
Users of this International Standard may freely reproduce the PICS proforma in this annex so that it can be used for the intended purpose and
may further publish the completed PICS.
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IS0 7776 : 1986/Amd.l : 1992 (E)
Multilink procedure, initialization, A.7.1: ML1
Multilink resetting, A.7.1: MLRi, MLRr, MLRCi, MLRCr, MLLNrs
Multilink procedure for taking an SLP out of service: MLSOS
Multilink frame transmission, A.7.1: MLFT, MLFTrf, MLFTrb
Multilink frame reception, A.7.1: MLFR, MLFRbs, MLFRfc, MLLNtl, MLMT2
Multilink frames, A.7.1: MLFS, MLFF, MLFVS, MLFSC
SPMT1, SPMT2, SPMT3, SPMWT, SPMWR, SPMX
Multilink system parameters, A.7.2:
A.3 Instructions for completing tlie PICS proforma
A.3.1 General structure of the PICS proforma
The first part of the PICS proforma - Implementation Identification and Protocol Summary - is to be completed as indicated with the
information necessary to identify fully both the supplier and the implementation.
The main part of the PICS proforma is a fixed-format questionnaire, divided into several subclauses each containing a number of individual
items. Answers to the questionnaire items are to be provided in the rightmost column, either by simply marking an answer to indicate a
restricted choice (usually Yes or No), or by entering a value or a set or range of values. (Note that there are some items where two or more
choices from a set of possible answers can apply: iill relevant choices are to be marked.)
Each item is identified by an item reference in the first column; the second column contains the question to be answered; the third column
contains the reference or references to the material that specifies the item in the main body of IS0 7776. The remaining columns record the
status of the item - whether support is mandatory, optional or conditional - and provide the space for the answers: see also A.3.4 below.
A supplier may also provide - or be required to provide - further information, categonzed as either Additional Information or
Exception Information. When present, each kind of further information is to be provided in a further subclause of items labelled Ai or Xi
respectively for cross-referencing purposes, where i is any unambiguous identification for the item (eg, simply a numeral): there are no other
on its format and presentation.
restrictions
A completed PICS proforma, including any Additional Information and Exception Information, is the Protocol Implementation
Conformation Statement for the implementation in question.
NOTE - Where an implcincntation is capable of bcing configurcd in more than one way, a single PICS may be able to describe all such configurations.
However, the supplier has the clioicc of providing more than one PICS, each covering some subset of the implementation’s configuration capabilities. in case
that makes for easier and clearer prcscntation of the infoi tiiation.
A.3.2 Additional Information
Items of Additional Information allow a supplier to provide further information intended to assist the interpretation of the PICS. It is not
intended or expected that a large quantity will be supplied, and a PICS can be considered complete without any such information. Examples
might be an outline of the ways in which a (single) implementation can be set up to operate in a variety of environments and configurations;
or a brief rationale - based perhaps upon specific application needs - for the exclusion of features which, although optional. are commonly
0 present in implementations of the IS0 7776 protocol.
References to items of Additional Information may be entered next to any answer in the questionnaire, and may be included in items of
Exception Information.
A.3.3 Exception Information
It may occasionally happen that a supplier will wish to answer an item with mandatory status (after any c
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