ISO/IEC 11575:1995

INTERNATIONAL
ISOAEC
STANDARD
ii575
First edition
1995-07-01
Information technology -
Telecommunications and information
exchange between Systems - Protocol
mappings for the OSI Data Link Service
Technologies de I’informa tion - T6kcommunications et kchange
d ‘in forma tion en tre systemes
- Applications du protocole au Service de
liaison de donnees OSI
Page
Contents
. . .
Foreword .
1 Scope .
2 Normative References .
3 Definitions .
4 Abbreviations .
5 Conformance .
6 General principles of the protocol mappings .
............
7 Protocol mapping for ISO/IEC 7776 Single link procedures
Protocol mapping for HDLC Unbalanced Operation Normal response mode
Class(UNC) .
Protocol mappings for LLC Types 1 and 2 .
10 Protocol mappings for HDLC connectionless-mode classes of procedure .
o ISO/IEC 1995
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ii
o ISO/IEC
Foreword
ISO (the International Organization for Standardization) and IEC (the
International Electrotechnical Commission) form the specialized System for
worldwide standardization. National bodies that are members of ISO 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. ISO and IEC technical committees collaborate in fields
of mutual interest. Other international organizations, governmental and non-
governmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint
technical committee, ISO/IEC 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.
International Standard ISO/IEC 11575 was prepared by Joint Technical
Committee ISO/IEC JTC 1, Information technology.
. . .
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INTERNATIONAL STANDARD @ ISOmC ISO/IEC 11575 : 1995 (E)
Information technology - Telecommunications and
information exchange between Systems - Protocol
mappings for the OSI Data Link Service
1 Scope
This International Standard specifies general principles for the mappings between the OS1 Data Link Service (ISO/IEC 8886), both
connection-mode (CO-DLS) and connectionless-mode (CL-DLS), and Standard Data Link protocols, as follows:
Ml: HDLC X.25 LAPB-compatible DTE procedures, Single link procedures (ISO/IEC 7776)
CO-DLS -
M2: CO-DLS - HDLC Unbalanced Operation Normal response mode Class, UNC (ISO/IEC 3309, ISO/IEC 4335 and ISO/IEC 7809)
Logical link control (LLC) Type 2 (ISO/IEC 8802-2)
M3: CO-DLS -
M4: LLC Type 1 (lSO/lEC 8802-2)
CL-DLS -
M5: CL-DLS - HDLC Balanced Operation ConnectionIess-nlode Class, BCC (lSO/lEC 3309, ISO/IEC 4335 and ISO/IEC 7809)
M6: CL-DLS - HDLC Unbalanced Operation Connectionless-mode Class, UCC (ISO/IEC 3309, ISO/IEC 4335 and ISO/IEC 7809)
This International Standard specifies the detailed mappings Ml, M2, M5 and MG; it also specifies the main features of the mappings M3 and
M4.
This International Standard does not specify individual implernentations or products, nor does it constrain the implementation of Data Link
entities and interfaces within an information processing System.
NOTES
1 The above designations Ml to M6 for the mappings arc used elsewhere in this International Standard.
2 The possibility of adding further mappings to the above list in the t‘uture is not preciuded (for exumple, to cover Frame Relay protocols).
2 Normative references
The following Standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the
time of publication, the editions indicated were valid. All Standards are subject to revision, and Parties to agreements based on this
International Standard are encouraged to investigate the possibility of applying the most recent editions of the Standards listed below.
Members of IEC and ISO maintain registers of currently valid International Standards.
ISO/IEC 3309: 1993, hzfornzatiou technology -- Tclcco~~~~321~~~icatio~rs arzd infwmation exchange between systems - High-level data link
control (HDLC) procedures - Frame stwctur-e.
ISO/IEC 4335: 1993, Iuformatiou tcchuologv - T~~lcconli7lrrrliccrtiorls cwd i~lf0rmatiou e.\rchu~~ge bctwee~z svstems - High-level data link
d
d
Eleme~~ts of’prowdwes.
corrtrol (HDLC) procedrrres -
.
ITU-T Recommendation X.200 (1994) I ISO/IEC 7498- 1: 1994, I#wmtrtiorl tccluwlogv - Opcll Systems Iiltcrcoruzcctiou -Basic Rcference
d
Model: The basic model.
ISO/IEC 7776: 1995, Information technology - Telecommunications and information exchange between Systems - High-level data link
control procedures - Description of the X.25 LAPB-compatible DTE data link procedures.
Tclcconlnllrrliccrtiorls aud i@wnzutiorl exchuuge betweeu systems - High-level data link
ISO/IEC 7809: 1993, Il$0rmutiorl tcchrlology -
control (HDLC) procedures - Clusses of yrocedurxv.

0 ISO/IEC
ISO/IEC 11575 : 1995 (E)
ISOIIEC 8802-2: 1994, Information technology - Telecommunications and information exchange between Systems - Local and
metropolitan area networks - Specific requirements - Part 2: Logical link control.
ISO/IEC 8886: 1992, Information techr?ology - Telecommurlicatioru arid ijlformatioll exchange between Systems - Data Link Service
definition for Open Systems Interconnection.
ITU-T Recommendation X.210 (1993) I ISO/IEC 1073 1: 1994, Information technology - Open Systems Interconnnection - Basic
Reference Model ~ Conventions for the definition of OSI Services.
3 Definitions
3.1 This International Standard uses the following temjs defined in ITU-T Rec. X.200 I ISO/IEC 7498-1:
DL-address
DL-connection
DL-connectionless-mode transmission
DL-entity
DL-group address
DL-layer
DL-protocol-data-unit
DL-Service access Point
DL-Service access point address
DL-service-data-unit
DL-Subsystem
3.2 This International Standard uses the following terms defined in ITU-T Rec. X.210 1 ISO/IEC 10731:
DLS provider
DLS user
primitive
request (primitive)
indication (primitive)
response (primitive)
tonfirm (primitive)
3.3 For the purposes of this International Standard, the following definitions apply:
3.3.1 frame: A DL-PDU.
3.3.2 instance of IX-conmwnication: A DL connection or a Single DL-connectionless-mode transmission.
4 Abbreviations
BCC balanced Operation connectionless-mode class
connectionless-mode
CL
CO connection-mode
DISC disconnect
DL Data Link
DLC Data Link connection
DLS Data Link Service
DLSAP Data Link Service access Point
DLSDU Data Link Service data unit
DM disconnected mode
FRMR frame reject
HDLC High-level data link control
1 information
LLC Logical Link Control
NRM nomlal response mode
PDU protocol data unit
quality of Service
QOS
SABM set asynchronous balanced mode
SABME set asynchronous balanced mode extended
SLP Single link procedure
SNRM set nomlal response mode
SNRME set normal response mode extended
unnumbered acknowledgment
UA
0 ISOJIEC
ISO/IEC 11575 : 1995 (E)
ucc unbalanced Operation connectionless-mode class
UI unnumbered infomlation
unbalanced Operation nomlal response mode class
UNC
5 Conformance
There is no direct confomlance of equipment to this International Standard considered in isolation. The provisions of this International
Standard have normative application to equipment implementing Network-layer protocols that are specified in terms of their use of the OS1
Data Link Service. For such Network-layer protocols, this International Standard links the behaviour of the underlying Data Link protocols to
the relevant features of the Data Link Service, and thus provides the basis for establishing conformance of the Network-layer protocol
implernentations to the specified usage of the Data Link layer.
NOTES
1 This International Standard therefore functions as “glue” between Network-layer protocol Standards, written in terms of their use of the OS1 Data Link
usually for historical reasons -
service, and Data Link protocol Standards written - without reference to the OS1 Data Link service. Conformance to such a
Data Link protocol Standard will be expressed entirely in terms of the procedures and PDUs, etc.,
specified in that Standard; conformance to such a Network-
layer Standard in respect of its use of the Data Link layer will be expressed in terms of, for example. the transfer of NPDUs as DLSDUs, and (for the CO-DLS)
of procedures that apply in the event of DL connection reset or DL connection release. This International Standard specifies precisely how the procedures, etc.,
of the Data Link protocol in question are to be interpreted in terms of the OS1 Data Link Service, and therefore establishes a precise relationship between the
specifications of the Network-layer protocol and of the Data Link protocol.
2 Use of the OS1 Data Link Service in Network-layer protocol specifications offers the benefits of layer-independence, in that such a Network-layer
specification is available, without Change, for use over new or alternative Data Link technotogies, provided only that the appropriate mapping is specified
between the OSI Data Link Service and the relevant Data Link technology.
6 General principles of the protocol mappings
6.1 Data Link architecture
The OS1 Data Link Service defines the properties of individual instances of DL-communication between pairs of DLS users.The definition is
abstractly expressed in terms of primitives and Parameters exchanged, at Data Link Service access Points (DLSAPs), between each DLS user
and a Single DLS provider: this is illustrated in figure 1.
DLS user
-
y DLS primitives f
D
\
LSAP -4
D LS provider _I~--~----~--~~~-
Figure 1 - Model of Data Link Service provision
Operation of the DLS provider is modelled in terms of the exchange of DL-PDUs, in accordance with DL-protocols, between DL-entities
(figure 2). Esch DLSAP is attached to a unique DL-entity; a given DL-entity tan have one or more DLSAPs attached to it, depending upon
System configuration and the nature of the underlying DL-protocols.
When real equipment is considered, a data link consists of two or more stations communicating according to a particular DL-protocol or set
of related DL-protocols, together with the interconnecting media supporting information exchange among the stations. Possible
configurations of a real data link (see figure 3) include:
Point-to-Point data links, with just two stations (rnappings M 1 and M5 are for protocols used in data links of this type);
centralized multipoint data links, with one Station controlling communication between itself and a number of subsidiary stations
b)
(mappings M2 and M6 arc for protocols used in data links of this type);
distributed multipoint data links, with a number of stations any of which tan communicate with any other (local area networks are of
this type, see mappings M3 and M4).
The definition of stations and data links has a logical dimension, deriving from the protocols used, in addition to the physical equipment used
in constructing particular real data links. A Single real System tan be attached to two or more data links, in which case it is considered to
contain the corresponding number of distinct stations; a Single real System tan contain two or more stations attached to the Same data link;
and it is possible for a Single set of communications equipment to support two or more distinct data links.

0 ISO/IEC
ISO/IEC 11575 : 1995 (E)
The Data Link Service model deals primarily with the properties of individual instances of DL-communication, each occurring between a
pair of DL-entities OT, for multicast communication, between a Single originating Source DL-entity and a set of destination DL-entities. DL-
protocols have to deal with multiple instances of communication, both between a given pair of DL-entities and, certainly for data links of
types (b) and (c) above, between different pairs (or multicast Sets) of DL-entities: representing the protocol facilities that support this forms a
part of the specification of the mapping between the protocol and the DLS. Aspects to be considered include the number of DLSAPs
supported by a given Station, the number of DL connections that tan be active simultaneously at a DLSAP, and the DL addressing facilities
that support discrimination among multiple stations.
DLS primitives
t’
1 I
I
DL-protocol
4 v
DL-entity * * DL-entity
(DL-PDUs)
I
DLS provider
Ie
1,
I
- - - -~~~-~~ -l
Figure 2 - Structure of DLS provider
4 *
a) Point-to-Point data link, two stations
,
only (e.g. combined stations or peer
stations)
, c
Controlling
b) Centralized multi-point data link,
communication between controlling
, 4
Station (e.g., primary Station or
control Station) and subsidiary
stations (e.g., secondary stations or
tributary stations)
Su bsidiary Subsidiary Su bsidiary
c) Distributed multipoint data link, any
Station to any Station
Types of clata link configuration
Fgure 3 -
0 ISO/IEC
ISO/IEC 11575 : 1995 (E)
6.2 Modelling of Service primitives
Primitives are abstractions of the behaviour of real Systems engaging in data communication: in specifying the mapping between these
abstract primitives and the activity of real implernentations of DL-protocol entities, this allows freedom in modelling the timing of when
primitives occur, so as to simplify the mapping specification.
explicitly allows this
NOTE 1 - ISO/IEC 8886 freedom; it defines the constraints on the sequence in which primi
...