ISO 8326:1987
(Main)Information processing systems — Open Systems Interconnection — Basic connection oriented session service definition
Information processing systems — Open Systems Interconnection — Basic connection oriented session service definition
Systèmes de traitement de l'information — Interconnexion de systèmes ouverts — Service de session en mode connexion
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Standards Content (Sample)
IS0
INTERNATIONAL STANDARD
8326
First edition
1987-08-15
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANISATION INTERNATIONALE DE NORMALISATION
MEX,QYHAPO,QHAR OPrAHM3AL&iR Il0 CTAH,QAPTM3AuMM
Information processing systems - Open Systems
Interconnection - Basic connection oriented session
service definition
Systèmes de traitement de finformation - Interconnexion de systèmes ouverts - Service de
session en mode connexion
!eference number
SO 8326 : 1987 (E)
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Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of
national standards bodies (IS0 member bodies). The work of preparing International
Standards is normally carried out through IS0 technical committees. Each member
body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the IS0 Council. They are approved in accordance with IS0 procedures requiring at
least 75 % approval by the member bodies voting.
International Standard IS0 8326 was prepared by Technical Committee ISO/TC 97,
Information processing systems.
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless otherwise stated.
O International Organization for Standardization, 1987 O
Printed in Switzerland
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IS0 8326 : 1987 (E)
Contents Page
O Introduction. . . 1
1 Scope and field of application . 1
3 References. . 1
Section one: General
3 Definitions . . 2
3.1 Reference Model definitions. .
3.2 Service convention definitions. .
3.3 Session service definitions .
4 Symbols and abbreviations .
4.1 Abbreviations. . . 3
4.2 Service variables . 3
5 Conventions. . . 3
6 Model of the session se . 3
7 Overview of the session service. . . 3
7.1 General overview . 3
7.2 Token concept. . 3
7.3 Synchronization and dialogue unit concepts .
7.4 Activity concept . 4
7.5 Resynchronization . . 4
7.6 Negotiation . 5
8 Phases and services of the session service. . 5
8.1 Session connection establishment phase. . 5
8.2 Data transfer phase . 5
8.3 Session connection release phase. . 6
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IS0 8326 : 1987 (E)
Page
9 Functional units and subsets . .
9.1 Functional units .
9.2 Subsets . .
10 Quality of session service . . .
10.1 Determination of QOS . . .
10.2 Session connection QOS negotiation procedures .
10.3 Definition of QOS parameters . .
Section two: Session service primitives
Introduction to session service primitives .
11 13
11.1 Summary of primitives . 13
11.2 Token restrictions on sending primitives . 13
11.3 Sequencing of primitives . 13
11.4 Synchronization point serial number management . .
16
12 Session connection establishment phase . 17
12.1 Session connection service . 17
13 Datatransfer phase . 19
13.1 Normal data transfer service . .
19
13.2 Expedited data transfer service . . 19
13.3 Typed data transfer service . 20
13.4 Capability data exchange service . 20
13.5 Givetokensservice . 21
Please tokens service . . .
13.6 21
Give control service . 22
13.7
13.8 Minor synchronization point service . 22
Major synchronization point service . 23
13.9
13.10 Resynchronize service . . 24
13.11 P-exception reporting service . 25
13.12 U-exception-reporting service . 26
13.13 Activity start service . 27
13.14 Activity resume service . 27
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IS0 8326 : 1987 (E)
Page
28
13.15 Activity interrupt service .
28
13.16 Activity discard service .
29
13.17 Activity end service .
30
14 Session connection release phase .
30
14.1 Orderly release service .
30
14.2 U-abortservice .
31
14.3 P-abort service .
31
15 Sequences of primitives .
31
15.1 Statetables .
31
15.2 Sequences of primitives at one session connection end-point .
31
16 Collision .
31
16.1 Collision as viewed by the SS-user .
32
16.2 Collision resolution by the SS-provider .
Annexes
33
A Statetables .
46
Corrections incorporated in IS0 8326 : 1987 .
B
V
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a
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IS0 8326 : 1987 (E)
INTERNATIONAL §TAN DARD
Information processing systems - Open Systems
Interconnection - Basic connection oriented session
service definition
O Introduction 1 Scope and field of application
This International Standard defines in an abstract way the exter-
This International Standard is one of a set of International Stan-
nally visible service provided by the OS1 Session Layer in terms of
dards produced to facilitate the interconnection of computer
a) the primitive actions and events of the service;
systems.
b) the parameter data associated with each primitive
action and event;
This International Standard is related to other International
c) the relationship between, and the valid sequence of
Standards in the set as defined by the Reference Model for
these actions and events.
Open Systems Interconnection (IS0 7498). The Reference
The service defined in this International Standard is that which
Model subdivides the area of standardization for interconnec-
is provided by the OS1 session protocol (in conjunction with the
tion into a series of layers of specification, each of manageable
OS1 presenta-
transport service) and which may be used by the
size.
tion protocol.
This International Standard does not specify individual im-
The purpose of this International Standard is to define the ser-
plementations or products, nor does it constrain the implementa-
vice provided to the Presentation Layer at the boundary
tion of entities and interfaces within a computer system. There
between the Session and Presentation Layers of the Reference
is, therefore, no conformance to this International Standard.
Model. The session service is provided by the session protocol
making use of the services available from the Transport Layer.
This international Standard also defines the session service
2 References
characteristics which the presentation protocol may exploit.
IS0 7498, Information processing systems - Open Systems
The relationship between the International Standards for the
Interconnection - Basic Reference Model.
session service, session protocol, transport service, and the
IS0 7498lAdd.3, Information processing systems - Open
presentation protocol is illustrated in figure 1.
Systems Interconnection - Basic Reference Model - Adden-
dum 3: Name including addressing. 1)
It is recognized that, with respect to session Quality of Service,
IS0 8072, Information processing systems - Open Systems
(described in clause IO), work is still in progress to provide an
Interconnection - Transport service definitions.
integrated treatment of QOS across all of the layers of the OS1
IS0 8327, Information processing systems - Open Systems
Reference Model and to ensure that the individual treatments in
Interconnection - Basic connection oriented session protocol
each layer service satisfy overall QOS objectives in a consistent
specification.
manner. As a consequence, an addendum may be added to this
International Standard at a later time which reflects further ISOITR 8509, Information processing systems - Open
Systems Interconnection - Service conventions.
00s developments and integration.
I Pi esentation I
based on service provided
t
Session service
t
provides service
I Session I
protocol
based on service provided
Transport service
Figure 1 - Relationship of this International Standard to other OS1 standards
At present at stage of draft; publication anticipated in due course.
1)
1
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IS0 8326 : 1987 (E)
Section one : General
3.3.1 calling SS-user: An SS-user that initiates a session
3 Definitions
connection establishment request.
NOTE - The definitions contained in this clause make use of abbrevia-
tions defined in clause 4.
3.3.2 called SS-user: An SS-user with whom a calling SS-
user wishes to establish a session connection.
3.1 Reference Model definitions
NOTE - Calling SS-users and called SS-users are defined with respect
to a single connection. An SS-user can be both a calling and called SS-
This International Standard is based on the concepts developed
user simultaneously.
in IS0 7498, and makes use of the following terms defined in it:
a) expedited-session-service-data-unit;
3.3.3 sending SS-user: An SS-user that acts as a source of
b) session-connection ;
data during the data transfer phase of a session connection.
c) Session Layer;
3.3.4 receiving SS-user: An SS-user that acts as a sink of
d) session-service;
data during the data phase of a session connection.
e) session-service-access-point;
NOTE - An SS-user can be both a sending and a receiving SS-user
f I session-service-data-unit ;
simultaneously.
g) Transport Layer;
3.3.5 requestor; requesting SS-user : An SS-user that
h) duplex;
initiates a particular action.
i) half-duplex.
3.3.6 acceptor; accepting SS-user: An SS-user that
accepts a particular action.
3.2 Service convention definitions
This International Standard also makes use of the following
3.3.7 token: An attribute of a session connection which is
terms defined in ISO/TR 8509, as they apply to the Session
dynamically assigned to one SS-user at a time to permit certain
Layer :
services to be invoked.
ai service-user;
3.3.8 conditional (parameter) : A parameter whose
b) service-provider;
presence in a request or response depends on conditions
defined in the text of this International Standard; and whose
c) primitive;
presence in an indication or confirm is mandatory if that
di request; parameter was present in the preceding session service
primitive, or absent if that parameter was absent in the
e) indication;
preceding session service primitive.
fi response;
3.3.9 proposed parameter: The value for a parameter pro-
g) confirm.
posed by an SS-user in an S-CONNECT request or an
S-CONNECT response that it wishes to use on the session con-
nection.
3.3 Session-service definitions
3.3.10 selected parameter: The value for a parameter that
For the purpose of this lnternational Standard, the following
has been chosen for use on the session connection.
definitions also apply.
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IS0 8326 : 1987 (E)
7.2 Token concept
4 Symbols and abbreviations
A token is an attribute of a session connection which is
4.1 Abbreviations
dynamically assigned to one SS-user at a time to permit certain
services to be invoked. It is the right to exclusive use of the
ss : session-service
service.
SSAP : session-service-access-point
SSDU : session-service-data-unit
Four tokens are defined:
NSSDU : normal-data-session-service-data-unit
TSSDU : typed-data-session-service-data-unit
a) the data token;
XSSDU : expedited-session-service-data-unit
QûS : quality of service ;
b) the release token
c) the synchronize-minor token;
4.2 Service variables
d) the major/activity token.
V(A) See 11.4.1.1
A token is always in one of the following states:
ViM) See 11.4.1.2
V(R) See 11.4.1.3
available, in which case it is always
e)
Vsc See 11.4.1.4
1) assigned to one SS-user, who then has the ex-
clusive right to use the associated service (provided that
no other restrictions apply) : and
5 Conventions
2) not assigned to the other SS-user, who does not
This International Standard uses the descriptive conventions
it later;
have the right to use the service but may acquire
defined in ISO/TR 8509 except that, where indicated in this
International Standard, parameter values associated with a ser-
O1
vice primitive may be passed in a direction opposite to the
direction of the service primitive.
f) not available to either SS-user, in which case neither
SS-user has the exclusive use of the associated service. The
service then becomes inherently available to both SS-users
6 Model of the session service
(data transfer and release), or otherwise unavailable to both
SS-users (synchronization and activities).
This International Standard uses the abstract model for a layer
service defined in ISO/TR 8509. The model defines the inter-
actions between the SS-user and the SS-provider which take
Restrictions related to the availability and assignment of tokens
place at the two SSAPs. Information is passed between an SS- are defined in 11.2.
user and the SS-provider by service primitives, which may con-
vey parameters.
7.3 Synchronization and dialogue unit concepts
7 Overview of the session service
SS-users may insert synchronization points into the data they
are transmitting. Each synchronization point is identified by a
serial number maintained by the SS-provider (see 11.4).
7.1 General overview
The session service provides the means for organized and syn-
Any semantics which SS-users may give to their synchroniza-
chronized exchange of data between cooperating SS-users. It
tion points are transparent to the SS-provider.
provides its users with means to
There are two types of synchronization points:
a) establish a connection with another SS-user, exchange
data with that user in a synchronized manner, and release
a) minor synchronization points;
the connection in an orderly manner;
b) negotiate for the use of tokens to exchange data, syn- b) major synchronization points.
chronize and release the connection, and to arrange for data
exchange to be half-duplex or duplex:
Major synchronization points are used to structure the
exchange of data into a series of dialogue units. The
c) establish synchronization points within the dialogue
characteristic of a dialogue unit is that all communication
and, in the event of errors, resume the dialogue from an
within it is completely separated from all communication before
agreed synchronization point;
and after it. A major synchronization point indicates the end of
one dialogue unit and the beginning of the next. Each major
interrupt a dialogue and resume it later at a prearranged
d)
synchronization point is confirmed explicitly.
point.
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IS0 8326 : 1987 (E)
An activity can be interrupted and then resumed on the same or
Minor synchronization points are used to structure the
on a subsequent session connection. This can be considered as
exchange of data within a dialogue unit. Figure 2 illustrates
how a dialogue unit is structured through the use of minor syn- a form of resynchronization.
chronization points. Each minor synchronization point may or
Figure 3 shows how an activity may be structured into dialogue
may not be confirmed explicitly.
units through the use of major synchronization points. In addi-
tion, the SS-users may transfer data outside an activity.
7.4 Activity concept
7.5 Resynchronization
The activity concept allows SS-users to distinguish between
different logical pieces of work called activities. Each activity Resynchronization may be initiated by either SS-user. It sets
the session connection to a defined state, and therefore
consists of one or more dialogue units. Only one activity is
includes reassignment of tokens and setting the synchroniza-
allowed on a session connection at a time, but there may be
tion point serial number to a new value. Resynchronization
several consecutive activities during a session connection. An
activity may also span more than one session connection. purges all undelivered data.
Dialoque unit
.'
MINOR MINOR MAJOR
MAJOR MINOR
SYNC SYNC SYNC SYNC SYNC
POINT POINT POINT POINT
POINT
Figure 2 - Example of a structured dialogue unit
Dialoaue unit
Dialogue unit
--
I AI I
t f t
ACTIVITY MINOR MINOR MAJOR MINOR ACTIVITY
SYNC SYNC END
START SYNC SYNC
POINT POINT POINT POINT (MAJOR SYNC
POINT)
Figure 3 -- Example of a structured activity
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IS0 8326 : 1987 (E)
Three options are provided : In all other combinations of functional units, no initial syn-
chronization point serial number is proposed.
a) abandon option which is used to set the synchroniza-
tion point serial number to an unused value;
b) restart option which is used to set the synchronization 8 Phases and serviceS.of the session service
point serial number to any used value which is greater than
the synchronization point serial number which identifies the The session service comprises three phases. The purpose of
each phase, and a short description of the associated services
last acknowledged major synchronization point;
is given in this clause. The services and the primitives by which
c) set option which is used to set the synchronization
they are invoked are defined in clauses 12, 13 and 14.
point serial number to any value chosen by the SS-user.
8.1 Session connection establishment phase
7.6 Negotiation
The session connection establishment phase is concerned with
establishing a connection between two SS-users. It has one
Negotiation takes place between both SS-users during the
service associated with it:
session connection establishment phase according to the
following rules.
the session connection service (see 12.1 ) is used to set up a
session connection and to negotiate tokens and parameters
to be used for the connection.
7.6.1 Negotiation of functional units
The kernel functional unit (see clause 9) is always used. Each
8.2 Data transfer phase
SS-user proposes the use or non-use of each of the other func-
tional units. A functional unit is selected only if both SS-users
The data transfer phase is concerned with the exchange of data
propose use of the functional unit and it is supported by the
between the two SS-users connected in the session connec-
SS-provider. Specific negotiation rules are given in 12.1.2.
tion establishment phase.
7.6.2 Negotiation of initiai token settings
There are four services associated with data transfer:
a) the normal data transfer service (see 13.1) allows the
When the calling SS-user proposes use of a functional unit that
transfer of normal data SSDUs (NSSDUs) over a session
requires a token, it also proposes the initial token settings:
connection. Its use is controlled by the data token if the
a) calling SS-user side;
half-duplex functional unit has been selected;
b) called SS-user side;
b) the expedited data transfer service (see 13.2) allows the
transfer of expedited SSDUs (XSSDUs) over a session con-
c) called SS-user choice.
nection free from the token and flow control constraints of
the normal data transfer service, typed data transfer service
If the use of the functional unit is selected, the token is set to
and capability data exchange service;
d) the sîde proposed by the called SS-user, if "called
c) the typed data transfer service (see 13.3) is used to
SS-user choice" is proposed by the calling SS-user; or
transfer typed data SSDUs (TSSDUs) independent of the
e) in all other cases, the side proposed by the calling
availability and assignment of the data token;
SS-user.
d) the capability data exchange service (see 13.4) is used
to exchange a limited amount of confirmed SS-user data
7.6.3 Negotiation of initiai synchronization point serial
while not within an activity.
number
There are three services concerned with token management:
When a calling SS-user proposes any of the major synchronize,
minor synchronize or resynchronize functional units, but does
e) the give tokens service (see 13.5) allows an SS-user to
it also
not propose the activity management functional unit, surrender one or more specific tokens to the other SS-user;
proposes a value for the initial synchronization point serial
f) the please tokens service (see 13.6) allows an SS-user
num ber.
to request the other SS-user to transfer one or more specific
tokens to it;
The calling SS-user may also propose a value for the initial syn-
chronization point serial number even if the activity manage-
g) the give control service (see 13.7) allows an SS-user to
ment functional unit is proposed provided that any of the minor
surrender all available tokens to the other SS-user.
synchronize, major synchronize or resynchronize functional
units are also proposed. If the called SS-user selects use of any
There are three services associated with synchronization and
of the minor synchronize, major synchronize or resynchronize
resynchronization :
functional units, but does not select use of the activity manage-
ment functional unit, it returns a value for the initial syn- h) the minor synchronization point service (see 13.8)
chronization point serial number which may or may not be the allows the SS-user to separate the flow of NSSDUs and
TSSDUs transmitted before the service was invoked from
same as the value proposed by the calling SS-user. The value
returned by the called SS-user is used as the initial synchroniza- the subsequent flow of NSSDUs and TSSDUs. Its use is
controlled by the synchronize-minor token ;
tion point serial number for the session connection.
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IS0 8326 : 1987 (E)
8.3 Session connection release phase
i) the major synchronization point service (see 13.9) allows
the SS-user to confine the flow of sequentially transmitted
NSSDUs, TSSDUs and XSSDUs in each direction within a
The session connection release phase is concerned with releas-
dialogue unit. Its use is controlled by the major/activity
ing a previously established session connection. It has three
token :
services associated with it:
j) the resynchronize service (see 13.10) is used to set the
session connection to a previous or to a new synchroniza-
a) the orderly release service (see 14.1) provides a
tion point and to reassign the available tokens. This service
means of achieving the orderly release of a session
may cause loss of NSSDUs, TSSDUs and XSSDUs.
connection ;
b) the user-initiated abort service (see 14.2) (U-abort ser-
There are two services for reporting errors or unanticipated
vice) is used to initiate the release of a session connection in
situations:
a way that will terminate any outstanding service request.
This service may cause loss of NSSDUs, TSSDUs and
k) the provider-initiated exception reporting service
XSSDUs;
(see 13.11 ) (P-exception reporting service) permits SS-
users to be notified of exception conditions or SS-provider
c) the provider-initiated abort service (see 14.3) (P-abort
protocol errors. This service may cause loss of NSSDUs,
TSSDUs and XSSDUs: service) is used by the SS-provider to indicate the release of
the session connection for internal reasons. This service
may cause loss of NSSDUs, TSSDUs and XSSDUs. Any
I) the user-initiated exception reporting service (see 13.12)
outstanding service request is terminated.
(U-exception reporting service) is used by the SS-user to
report an exception condition when the data token is
available but not assigned to the SS-user. This service may
cause loss of NSSDUs, TSSDUs and XSSDUs.
9 Functional units and subsets
There are five services associated with activities:
Functional units
m) the activity start service (see 13.13) is used to indicate
that a new activity is entered. Its use is controlled by the
Functional units are logical groupings of related services
major/activity token;
defined by this International Standard for the purpose of
n) the activity resume service (see 13.14) is used to
indicate that a previously interrupted activity is re-entered. negotiation of SS-user requirements during the session
a)
Its use is controlled by the major/activity token; connection establishment phase;
O) the activity interrupt service (see 13.15) allows an
reference by other International Standards.
b)
activity to be abnormally terminated with the implication
that the work so far achieved is not to be discarded and may
be resumed later. Its use is controlled by the major/activity
Table 1 specifies the association of tokens and functional units.
token. This service may cause loss of NSSDUs, TSSDUs
When a functional unit implies the availability of a token, ser-
and XSSDUs;
vices concerned with the management of that token are pro-
vided in order to be able to request and transfer the available
p) the activity discard service (see 13.16) allows an activity tokens.
to be abnormally terminated with the implication that the
so far achieved is to be discarded, and not resumed.
work
Its use is controlled by the major/activity token. This service
The services associated with each functional unit are specified
may cause loss of NSSDUs, TSSDUs and XSSDUs;
in table 2.
q) the activity end service (see 13.17) is used to end an
activity (and set a major synchronization point). Its use is
controlled by the inajor/activity token;
Table 1 - Functional units using tokens
I Functional unit I Token
Using the activity services may lead to a state where no activity
Negotiated release Release token
is in progress on the session connection. When activity services
Half-duplex Data token
are employed, but no activity is in progress, only the activity
Minor synchronize Synchronize-minor token
start, activity resume, token management, capability data,
Major synchronize Major/activity token
typed data, normal data, expedited data, abort and release ser-
Activity management Major/activity token
vices may be invoked by the SS-users.
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IS0 8326 : 1987 (E)
Table 2 - Services associated with each functional unit
Functional unit Service(s1 Reference
Kernel (non-negotiable) Session connection 12.1
Normal data transfer 13.1
Orderly release 14.1
U-Abort 14.2
P-Abort 14.3
__
Orderly release 14.1
Negotiated release
Give tokens 13.5
Please tokens 13.6
Half-duplex Give tokens
Please tokens
-~___
Duolex No additional service
Expedited data Expedited data transfer I 13.2
Typed data Typed data transfer 13.3
Capabilitv data exchanae Caaabilitv data exchanae 13.4
Minor synchronize Minor synchronization point
Give tokens
Please tokens
Major synchronize Major synchronization point
Give tokens
Please tokens
Resvnchronize
Resynchronize 13.10
Exceptions Provider exception reporting 13.11
User exception reporting I-- 13.12
Activity management Activity start 13.13
Activity resume 13.14
Activity interrupt 13.15
Activity discard 13.16
Activity end 13.17
Give tokens 13.5
Please tokens 13.6
Give control 13.7
9.1.1 Kernel functional unit 9.1.5 Expedited data functional unit
The expedited data functional unit supports the session ex-
The kernel functional unit supports the basic session services
pedited data transfer service.
required to establish a session connection, transfer normal data
and release the session connection.
9.1.6 Typed data functional unit
The typed data functional unit supports the typed data transfer
9.1.2 Negotiated release functional unit
service.
The negotiated release functional unit supports the negotiated
9.1.7 Capability data exchange functional unit
orderly release service. The release token is available when this
functional unit has been selected.
The capability
...
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