IS 13868: Network service definition in data communications for information processing systems

34 Pages·1993·2.9 MB·English

by  Bureau of Indian Standards

इंटरनेट मानक
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timely dissemination of this information in an accurate manner to the public.
“जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ”
Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru
“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 13868 (1993): Network service definition in data
communications for information processing systems [LITD 13:
Information and Communication Technologies]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 13868 : 1993
IS0 8348 : 1987

Indian Standard
NETWORK SERVICE NOITINIFED IN ATAD
COMMUNICATIO~NS ROF NOITAMROFNI
GNISSECORP SMETSYS
U DC 681’327’8’01

0
BIS 1993
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002
December 1993 Rice Group IO
.
retupmoC smetsyS dna noitcennocretnI lanoitceS Committee, DTL 63
LANOITAN FOREWORD
sihT naidnI dradnatS hcihw si lacitnedi htiw 0SI 8438 : 7891 noitamrofnI‘ gnissecorp systems -
ataD snoitacinummoc - Network ecivres ,’noitinifed deussi yb eht lanoitanretnI noitazinagrO
rof noitazidradnatS ( 0SI ) saw detpoda yb eht uaeruB fo naidnI sdradnatS no eht recommen-
noitad fo eht retupmoC smetsyS dna noitcennocretnI lanoitceS Committee ( DTL 63 ) dna
lavorppa fo eht scinortcelE dna noitacinummoceleT noisiviD .licnuoC
nI eht detpoda dradnats niatrec ygolonimret dna snoitnevnoc era revewoh ton lacitnedi ot esoht
desu ni naidnI .sdradnatS noitnettA si ylralucitrap nward ot eht :gniwollof
Wherever eht sdrow lanoitanretnI‘ ’dradnatS raeppa gnirrefer ot siht ,dradnats yeht dluohs
eb daer sa naidnI‘ .’dradnatS
nI siht naidnI ,dradnatS eht gniwollof lanoitanretni sdradnats era derrefer .ot daeR ni rieht
evitcepser ecalp eht :gniwollof
International Standard Indian Standard
IS0 7498 noitamrofnI gnissecorp systems - SI 37321 ( traP 1 ) : 7891 + cisaB ecnerefer
nepO systems noitcennocretni - cisaB ledom fo nepo systems noitcennocretni rof
ecnerefer ledom noitamrofni gnissecorp systems : traP 1
( lacitnedI )
0SI 3708 : 8891 noitamrofnI gnissecorp SI 91931 : 3991 noitcennoC detneiro tropsnart
systems -. nepO systems -cennocretni locotorp noitacificeps ni nepo systems
noit - noitcennoC detneiro tropsnart noitcennocretni rof noitamrofni gnissecorp
locotorp noitacificeps sytems ( rednU tnirp )
( lacitnedI >
ehT lacinhcet committee elbisnopser rof eht noitaraperp fo siht dradnats sah deweiver eht
snoisivorp fo eht gniwollof 0SI sdradnatS dna sah dediced taht yeht era elbatpecca rof esu ni
noitcnujnoc htiw siht :dradnats

RT/OSI 9058 : 7891 noitamrofnI gnissecorp systems - Open systems interconnection -

Service conventions
CCITT Recommendation X ‘200 Reference model of nepo systems noitcennocretni rof TTICC
snoitacilppa
TTlCC noitadnemmoceR X ‘210 OSI layer ecivres noitinifed COnVentiOnS
TTICC noitadnemmoceR 312.X Network ecivres noitinifed rof nepo systems noitcennocretni
rof TTICC snoitacilppa
TTICC noitadnemmoceR 422.X tropsnarT locotorp noitacificeps rof nepo systems -nocretni
noitcen rof TTICC snoitacilppa
ehT txet fo lacinhcet mudnegirroc 1 ( I‘ 199 ) ot 0SI 8438 : 7891 si nevig ta eht dne fo siht
.dradnats
ylnO eht hsilgnE egaugnal txet ni eht lanoitanretnI dradnatS sah neeb deniater elihw gnitpoda
ti ni siht .dradnatS
IS 13888: 1993
IS0 8348: 1987
Indian Standard
NETWORK SERVICE NOITINIFED IN ATAD
COMMUNICATIONS ROF NOITAMROFNI
GNISSECORP SMETSYS
0 Introduction Throughout the set of OSI Standards the term “Service” refers
to the abstract capability provided by one layer of the OSI
This International Standard is one of a set of International Stan- Reference Model to the layer above it. Thus, the Network Ser-
dards produced to facilitate the interconnection of computer vice defined in this International Standard is a conceptual
systems. It is related to other International Standards in the set architectural Service, independent of administrative divisions.
as defined by the Open Systems Interconnection (OS11 Basic
Reference Model. The OSI Reference Model subdivides the NOTE - It is important to distinguish the specialized use of the term
area of standardization for interconnection into a series of “Service” within the set of OS.1 Standards from its use elsewhere to
layers of specification, each of a manageable size. describe the provision of a service by an organization (such as the pro-
vision of a service, as defined in other CCITT Recommendations, by an
This International Standard defines the Service provided by the Administration).
Network Layer to the Transport Layer at the boundary between
Any particular subnetwork may or may not support the OSI
the Network and Transport Layers of the Reference Model. It
Network Service. The OSI Network Service may be provided
provides for the designers of Transport Protocols a definition of
by a combination of one or more subnetworks and optional
the Network Service existing to support the Transport Protocol
additional functions between or outside these subnetworks.
and ror the designers of Network Protocols a definition of the
servrces to be made available through the action of the Network
Protocol over the underlying service. This relationship is
1 Scope and field of application
illustrated in figure 1.
t
I This International Standard defines the OSI Network Service in

terms of
-
Transport Protocol Transport - - -,
uses Service
Layer
a) the primitive actions and events of the Service;
i
- - -
Network,Service
b) the parameters associated with each primitive action
1
I and event, and the form which they take;
Network Protocol Network -1
provides Service
Layer
c) the interrelationship between, and the valid sequences
I--- I
1 of, these actions and events.
Figure 1 - Relationship of the Network Service in this The principal objectives of this International Standard are
International Standard to the protocols specified in
other OSI Standards a) to specify the characteristics of a conceptual Network
Service and thus supplement the Reference Model in
guiding the development of Network Layer protocols;
The use of the word “Network” to name the “Network” Layer
of the OSI Reference Model should be distinguished from the
b) to encourage convergence of the capabilities offered by
use of the word “network” to denote a communications
providers of subnetworks;
network as conventionally understood. To facilitate this dis-
tinction, the term “subnetwork” is used for a collection of c) to provide a basis for the individual enhancement
physical equipment, commonly called a “network!” (see of existing heterogeneous subnetworks to a common
IS0 7498). Subnetworks may be either public networks or subnetwork-independent Network Service to enable them
privately supplied networks. In the case of public networks, to be concatenated for the purpose of providing global com-
their properties may be determined by separate CCITT Recom- munication. (Such concatenation may involve optional
mendations such as CCITT Recommendation X.21 for a cirkuit- additional functions which are not defined in this Inter-
switched network or CCITT Recommendation X.25 for a national Standard.) A definition of the quality of service is
packet-switched network. an important element of this International Standard;
1
IS 13868: 1993
.
IS0 8348 : 1987
d) to provide a basis for the development and implemen- NOTE - See also CCITT Recommendation X.200, Reference Mode/of
tation of subnetwork-independent Transport Layer proto- Open Systems Interconnection for CCITT Applications.
cols decoupled from the variability of underlying public and
private subnetworks and their specific interface IS0 8073, information processing systems - Open Systems
requirements. Interconnection - Connection oriented transport protocol
specification.
This International Standard does not specify individual im-
plementations or products nor does it constrain the implemen-
NOTE - See also CCITT Recommendation X.224, Transport Protocol
tation of entities and interfaces within a system.
Specification for Open Systems Interconnection for CCITT Appli-
cations.
There is no conformance of equipment to this International
Standard. Instead, conformance is achieved through im-
plementation of conforming OSI Network protocols which ISOITR 8509, Information processing systems - Open
fulfill the Network Service defined in this International Systems Interconnection - Service conventions.
Standard.
NOTE - See also CCITT Recommendation X.210, OS/ Layer Service
definition conventions.
2 References
IS0 7498, Information processing systems - Open Systems CCITT Recommendation X.213, Network Service Definition for
Interconnection - Basic Reference Model. Open Systems Interconnection for CCITT Applications.
c
IS 13868: 1993
IS0 &48: 1987
Section one : General
3 Definitions 3.3.3 Generic address : An address which identifies a set of
NSAPs rather than a single specific NSAP.
NOTE - The definitionsc ontainedi n this clause make use of abbrevi-
ations defined in clause4 .
4 Abbreviations
3.1 Reference Model definitions COR Confirmation of Receipt
ENSDU Expedited Network-Service-Data-Unit
This international Standard is based on the concepts developed
in IS0 7498, and makes use of the following terms defined in it: N Network
NC Network-connection
a) expedited Network-Service-data-unit
NL Network Layer
bl Network-Connection
NS Network Service
cl Network Layer
NSAP Network-Service-access-point
d) Network Service NSDU Network-Service-data-unit
e) Network-Service-access-point OSI Open Systems Interconnection
00s Quality of service +
f) Network-Service-access-point-address
9) Network-Service-data-unit
5 Conventions
h) subnetwork
5.1 General conventions
3.2 Service conventions definitions This International Standard uses the descriptive conventions
defined in ISO/TR 8509.
This international Standard also makes use of the following
The layer service model, service primitives, and time-sequence
terms defined in ISO/TR 8509, as they apply to the Network
Layer : diagrams taken from those conventions are entirely abstract
descriptions; they do not represent a specification for im-
plementation.
a) Network Service user
b) Network Service provider 5.2 Parameters

c) primitive Service primitives, used to represent service-user/service-

provider interactions (see ISO/TR 85091, convey parameters
d) request which indicate information available in the user/provider
interaction.
e) indication
The parameters which apply to each group of Network Service
f 1 response ~primitivesa re set out in tables in clauses 12 to 14. Each “X” in
the tables indicates that the primitive labelling the column in
g) confirm which it falls may carry the patameter labelling the row in which
it falls.
3.3 Network Service definitions Some entries are further qualified by items in brackets. These
may be
For the purpose of this International Standard, the following
definitions also apply. a) an indication that the parameter is conditional in some
way :
(Cl indicates that the parameter is not present on the
3.3.1 Calling NS user: An NS user that initiates an NC
primitive for every NC; the parameter definition
Establishment request.
describes the conditions under which the parameter is
present or absent.
3.3.2 Called NS user: An NS user with whom a calling NS
-b) a parameter specific constraint :
user wishes to establish an NC.
=( 1 indicates that the value supplied in an indication or
NOTE - Calling NS usersa nd called NS usersa re definedw ith respect confirm primitive is always identical to that supplied in
to a singleN C. An NS user can be both a callinga nd a called NS user the corresponding request or response primitive occur-
simultaneously. ring at the peer NSAP.
3
IS 13868: 1993
.
IS0 8348 : 1987
c) indication that some note applies to the entry: 7 Features of the Network Service
(Note x) indicates that the referenced note contains ad- The Network Service offers the following features to an NS
ditional information pertaining to the parameter and its use. user:
In any particular interface, not all parameters need be explicitly a) The means to establish an NC with another NS user for
stated. Some may be implicitly associated with the NSAP at the purpose of transferring NS-user-data in the form of
which the primitive is issued. NSDUs. More than one NC may exist between the same
pair of NS users.
5.3 NC endpoint identification convention b) The establishment of an agreement between the two
NS users and the NS provider for a certain QOS associated
If an NS user needs to distinguish among several NCs at the with each NC.
same NSAP, then a local NC endpoint identification mechan-
ism must be provided. All primitives issued at such an NSAP c) The means of transferring NSDUs in sequence on an
would be required to use this mechanism to identify NCs. Such NC. The transfer of NSDUs, which consist of an integer
an implicit identification is not described as a-parameter of the number of octets, is transparent, in that the boundaries of
service primitives in this International Standard. NSDUs and the contents of NSDUs are preserved un-
changed by the Network Service, and there are no
NOTE - The implicit NC endpoint identification must not be confused constraints on the NSDU content~imposed by the Network
with the address parameters of the N-CONNECT primitives (see 12.2). Service.
d) The means by whichfhe receiving NS user may flow
control the rate at which the sending NS user may send
6 Overview and general characteristics
NSDUs.
The Network Service provides for the transparent transfer of
e) In some circumstances, the means of transferring
data (i.e. NS-user-data) between NS users. It makes invisible to
separate expedited NSDUs in sequence (see clause 8).
these NS users the way in which supporting communications
Expedited NSDUs are limited in fength and their transmis-
resources are utilized to achieve this transfer.
sion is subject to a different flow control from normal data
across the NSAP.
In particular, the Network Service provides for the following :
f) The means by which the NC can be returned to a de-
a) Independence of underlying transmission media - The fined state and the activities of the two NS users syn-
Network Service relieves NS users from all concerns regard- chronized by use of a Reset service.
ing how various subnetworks are used to provide the Net-
work Service. The Network Service hides from the NS user
g) In some circumstances, the means for the NS user to
differences in the transfer of data over heterogeneous
confirm the receipt of an NSDU (see clause 8).
subnetworks, other than quality of serv ice.

h) The unconditional, and therefore possibly destructive,
b) End-to-end transfer - The Network Service provides
release of an NC by either of the NS users or by the NS
for transfer of NS-user-data between NS users in end
provider.
systems. All routing and relaying functions are performed
by the NS provider including the case where several similar
or dissimilar transmission resources are used in tandem or in
parallel.
8 Classes of Network Service
c) Transparency of transferred information - The Net-
No distinct classes of Network Service are defined. However,
work Service provides for the transparent transfer of octet-
two Network Layer services, Receipt Confirmation and
aligned NS-user-data and/or control information, It does
not restrict the content, format or coding of the infor- Expedited Data Transfer, are NS provider-options.
mation, nor does it ever need to interpret its structure or
meaning. A service which is an NS provider-option is one which an NS
provider can choose either to provide or not to provide for a
d) Quality of service selection - The Network Service particular NC. In circumstances where the NS provider chooses
makes available to NS users a means to request and to not to provide a provider-option service, it will not be available
~agree to the quality of service for the transfer of NS-user- in the Network Service. If the provider-option Receipt Confir-
data. Quality of service issspecified by ~means of QOS- mation or Expedited Data Transfer is provided, it shall be pro-
parameters representing characteristics such as vided as defined in this International Standard (see clauses 14.1
throughput, transit delay, accuracy, and reliability. to 14.31.
e) NS-user-addressing - The Network Service utilizes a All other Network services are mandatory in the Network
system of addressing INSAP addressing) which allows NS Service. Mandatory services shall be provided by every NS
users to refer unambiguously to one another. provider and are therefore always available.
4
IS 13888 : 199b
IS0 8348: 1987
9 Model of the Network Service provide the Network Service. No attempt to specify or
constrain Network Service implementations is implied.
9.1 Model of the Network Layer Service In interpreting this International Standard, statements in
clauses 12 to 14 concerning the properties of individual primi-
This International Standard uses the abstract model for a layer tives have precedence over the general statements in this
service defined in clause 4 of ISO/TR 8SO9 The model defines clause.
the interactions between the NS users and the NS provider
which take pie-q at the two NSAPs. Information is passed NOTE - In addition to the interaction between service primitives
between the NS user a.^? the NS provider by service primitives, describedb y this model, there may beconstraintsa ppliedl ocallyo n the
which may convey parameters ability to invoke primitives,a s well as servicep ro&lures definingp ar-
ticular sequencingc onstraintso n some primitives.
There are two types of OSI Network Service:
9.2.1 Queue model concepts
a) a connection-mode Service (defined in section two).
The connection-mode Service is characterized by the The queue model represents the operation of an NC in the
features a) to h) given in clause 7. abstract by a pair of queues linking the two NSAPs. There is
one queue.foreach direction of information flow (see figure 2).
b) a connectionless-mode Service (defined in addendum 1
to this International Standard). Each queue represents a flow control function in one direction
of transfer. The ability of an NS user to add objects to a queue
When making reference to the Network Service, an NS user or will be determined by the behaviour of the_NS user removing
NS provider shall state which types of Network Service it objects from that queue and the state of the queue. Objects are
expects to use or provide. entered or removed from the queue, either as the result of
interactions at the two NSAPs, or as thkresult of NS provider
initiatives.
9.2 Model of a Network Connection
The pair of queues is considered to be available for each poten-
tial NC.
Between the two endpoints of an NC, there exists a flow con-
trol function which relates the behaviour of the NS user at one
The objects which may be placed in a queue as a result of
end receiving NS-user-data to the ability of the NS user at the
interactions at an NSAP (see clauses 12 to 14) are
other end to send NS-user-data. As a means of specifying this
flow control feature and its relationship with other capabilities
a) connect objects (associated with N-CONNECT
provided by the Network Service, the queue model of an NC,
primitives and all of their parameters);
described in the following clauses, is used.
b) octets of normal NS-user-data (associated with an
This queue model of an NC is discussed only to aid in the N-DATA primitive);
understanding of the end-to-end service features perceived by
cl indications of end-of-NSDU (associated with com-
users of the Network Service. It is not intended to serve as a
substitute for a precise, formal description of the Network Ser- pletion of an N-DATA primitive);
vice, nor as a complete specification of all allowable sequences d) expedited NSDUs (associated with N-EXPEDITED-
of NS primitives. (Allowabte primitive sequences are specified in
DATA primitives and all their parameters);
clause 11 - also, see the note.) In addition, this model does not
attempt to describe all the functions or operations of Network e) data acknowledgment objects (associated with
Layer entities (including relay entities) which are used to N-DATA-ACKNOWLEDGE primitives);
“.
I I
NS resu A NS user B
Queue from A to 6
Queue from B to A
NS provider
Figure 2 - Queue model of a N etwork Connection