ISO/IEC 8073:1988/Add 2:1989
(Main)Information processing systems — Open Systems Interconnection — Connection oriented transport protocol specification — Addendum 2
Information processing systems — Open Systems Interconnection — Connection oriented transport protocol specification — Addendum 2
Systèmes de traitement de l'information — Interconnexion de systèmes ouverts — Protocole de transport en mode connexion — Additif 2
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISOIIEC
8073
STANDARD
Second edition
1988-12-1 5
ADDENDUM 2
1989-09-1 5
Information processing systems - Open
Systems Interconnection - Connection oriented
transport protocol specification
ADDENDUM 2 : Class four operation over
con nec t ion less network service
Systèmes de traitement de l'information - Interconnexion de systèmes ouverts -
Protocole de transport en mode connexion
ADDITIF 2 : Fonctionnement de la classe 4 sur le service de réseau en mode sans
connexion
Reference number
ISO/IEC 8073 : 19WAdd.2 : 1989 (E)
---------------------- Page: 1 ----------------------
ISO/IEC 8073 : 1988/Add.2 : 1989 (E)
Contents
O Introduction , , . . . . . . . . , . . . . . . . . . . . . . . . . , . . . . . . . . , . . . . . . . . . . . . . . 2
1 Scope and field of application . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . , . . . . 2
e
2 References . 2
Section one : General
3 Definitions . 4
4 Symbols and abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5 Overview of the transport protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Section two : Transport protocol specification
6 Elementsofprocedure . . . . . . . . . . . . . . . . . . . . . . *. . . . . . . . . . . +. . ~ ". . . 7
7 Protocol classes . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
12 Specification for class 4 : Error detection and recovery class . . . . . . . . . . . . . . . . . . . . . . . . . 15
13 Structure and encoding of TPDUs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
0
Section three : Conformance
14 Conformance. . . . . . . . . . . . . . . , *. . . . ". . . . . . . . . . . . . . . . . . *. . . . . . . 20
Annexes
Statetables . . . . . . . . . . , . . . , , , , . . . . . , , , , . . . . . . . . , . . , . . . . . , . . . . , . 21
A
C State tables for operation of class 4 over connection-oriented and connectionless network services . , . . . 25
O ISO/IEC 1989
All rights reserved. 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 0 Case postale 56 0 CH-I211 Genève 20 0 Switzerland
Printed in Switzerland
---------------------- Page: 2 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
Foreword
IS0 (the International Organization for Standardization) and IEC (the International
Electrotechnical Commission) together form a system for worldwide standardization as
a whole. National bodies that are members of IS0 or IEC participate in the develop-
ment 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, ISO/IEC JTC 1. Draft International Standards adopted by the joint
technical committee are circulated to national bodies for approval before their accep-
tance as International Standards. They are approved in accordance with procedures re-
quiring at least 75 % approval by the national bodies voting.
International Standard ISO/IEC 8073/Add.2 was prepared by Joint Technical Com-
mittee ISO/IEC JTC 1, Information technology.
Users should note that all International Standards undergo revision from time to time
and that anv reference made herein to any other International Standard implies its
---------------------- Page: 3 ----------------------
ISO/IEC 8073 : 1988/Add.2 : 1989 (E)
INTERNATIONAL STANDARD
Information processing systems - Open Systems
Interconnection - Connection oriented transport protocol
a
specification
ADDENDUM 2 : Class four operation over connectionless
network service
e
1
---------------------- Page: 4 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
O Introduction
ISOAEC 8073 specifies the connection-oriented Transport Protocol that provides the Transport Service as described in IS0 8072.
This Transport Protocol uses the connection-oriented services provided by the Network Layer as specified in IS0 8348.
This addendum adds to ISOAEC 8073 the ability to provide the connection-mode transport service using the connectionless-mode
Network Service (IS0 8348/Add. 1) based upon class 4 procedures. The addendum has a structure which is similar to that of
ISOAEC 8073 in order to facilitate cross reference between the two documents and the eventual incorporation of this addendum into
ISOAEC 8073. Table numbering from ISOAEC 8073 has been retained in the addendum in order to maintain alignment with
ISO/IEC 8073 and for re-use of reference. Clause and sub-clause references in the text of ISOAEC 8073 should be considered, in the
context of the application of this addendum, to refer to the corresponding clauses and sub-clauses of this addendum, where they exist.
Except where a variation is specified in this addendum, the procedures specified in ISOAEC 8073 for class four operation over the
connection-oriented Network Service apply also to operation over the connectionless Network Service. General references in
ISO/IEC 8073 to the Network Service and to IS0 8348 should be considered to be extended to embrace the connectionless Network
Service as specified in IS0 8348/Add. 1. General references to a network connection should be considered to be extended to refer to
the existing association between a pair of NSAPs over which a transport connection is established or being established.
IS0 7498 describes the Basic Reference Model of Open Systems Interconnection. It is the intention of the International Standard that
the Reference Model should establish a framework for coordinating the development of existing and future standards for the intercon-
nection of open systems.
The relationship between connection-oriented transmission and connectionless-mode transmission is defined in IS0 7498/Add. 1.
In the following clauses, two fonts are used to distinguish between instructions (for incorporating this addendum into ISOAEC 8073)
and original or replacement text.
This italic font is used for instructions and titles in reference clause 2,
O while this sans serif font is used for original or replacement text.
Scope and field of application
I
Modifv the first item, %) five classes of procedures:” to read %) five classes of procedure when operating over the
connection oriented Network Service: ”.
Add a new item, “b) one class of procedure when operation over the connectionless Network Service:”.
Re-label the original items b) and c) as items c) and d).
This addendum specifies the use of only a sangle class of procedures, class 4, for the connection-oriented transfer of
data control information from one transport entity to a peer transport entity, over the connectionless network service.
2 References
Add the following references:
2
---------------------- Page: 5 ----------------------
ISWIEC 8073 : 198WAdd.2 : 1989 (E)
Information processing systems - Open Systems Interconnection - Basic Reference
IS0 7498/Add. 1,
Model - Addendum 1: Connectionlcss-mode transmission.
Information processing systems - Data communications - Network service definition
IS0 8348/Add. 1,
- Addendum 1: Connectionless-mode transmission.
3
---------------------- Page: 6 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
I
Section one : General
3 Definitions
This addendum makes use of the definitions specified in clause 3 of ISO/IEC 8073, with the following qualifications:
a) Add to sub-clause 3.1 after YS0 7498”, ”and IS0 7498/Add. 1”.
b) Add a new item to sub-clause 3.1, 4) connectionless mode transmission”.
c) Add to end of sub-clause 3.2.28 owner (of a network connection), ‘Only applicable when operating over the
connection-oriented Network Service. ”
d) Add as sub-clause 3.6.30 the following additional definition:
connectionless network service: A network service providing connectionless mode transmission.
4 Symbols and abbreviations
Add to sub-clause 4.5 the following symbols and abbreviations:
CLNS Connectionless network service
CONS Connection-oriented network service
5 Overview of the transport procotol
5.1 Service provided by the transport layer
5.2 Service assumed from the network layer
Add to 4SO 8348”, “and IS0 8348/Add. 1”.
Add When operating over CONS,” to the beginning of the paragraph which starts, %formation is transferred”
Modify Table 2: Network service primitives” to ‘Table 2a) - Network service primitives of CONS”.
Add the following text after the second paragraph:
When operating over CLNS. information is transferred to and from the NS-provider in the network service
primitive listed in table 2b) below:
4
---------------------- Page: 7 ----------------------
ISO/IEC 8073 : 19WAdd.2 : 1989 (E)
Add the following table after table ea):
Table 2b) - Network service primitives of CLNS
Parameters X
I P ri mit ives Ix
U N IT DATA request X Source Address X
Destination Address X
X
Quality of service X
NS-user-data X
Source Address X
indication X
Destination Address X
Quality of service X
NS-user-data x
X : The transport protocol assumes that this facility is provided in all networks.
NOTES
1 The parameters listed in this table are those in the current connectionless Network Service (IS0 8348/Add. I).
2 The way the parameters are exchanged between the transport entity and the network service provider is a local matter.
5.3 Functions of the transport layer
Add ‘bnly when operating over CONS,” to sub-clause 5.9.1.1, item b)l ’tnultiplexing and demultiplexing” after the phrase,
“a function ”.
Add ‘bnly when operating over CONS,” to sub-clause 5.9.1.2, item b), ”decide whether to multiplex’’ after the phrase,
“a single network connection”.
Replace sub-clause 5.9.1.9, item c)~ with the following text:
‘Splitting and recombining (see 6.23): a function allowing. only when operating over CONS, the simultaneous use of two
or more network connections to support the same transport connection: ”.
5.4 Classes and options
Re-title sub-clause 5.4 as ‘5.4 Classes and options when operating over CONS”.
Re-number sub-clause 5.5, ‘Model of the transpokt layer” as sub-clause 5.6, and add the following text as the new
sub-clause 5.5:
5.5 Characteristics of class 4 transport protocol when operating over CLNS
In operation over a connectionless network service the class 4 transport procotol provides flow control between
communicating peer transport entities. the capability to detect and recover from errors which occur as a result
of a low grade of service available from the NS-provider, and resilience from failure of the peer entity. The kinds
of error to be detected include: TPDU loss, TPDU delivery out of sequence. TPDU duplication and TPDU
corruption. These errors may affect control TPDUs as well as data TPDUs.
NOTE - The transport entity is incapable of distinguishing between failure of the network service and failure
of the peer entity. except optionally. by some local means. in the case of the failure of the local interface to the
network service (e.g. in the failure of the local transceiver on a local area network).
5
---------------------- Page: 8 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
There is no indication given to the transport entity about the ability of the network entity to fulfill the service
it can be a local matter to make transport entities
requirements given in the N-UNITDATA primitive. However,
of the availability and characteristics (QOS) of connectionless network services. as the corresponding
aware
NSAP associations. exist logically by the nature of the connectionless network service and may be recognized
by network entities.
5.6 Model of the transport layer
Add ’Land IS0 8348/Add. 1” after, %ee IS0 8348”.
6
---------------------- Page: 9 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
Section two : Transport protocol specification
6 Elements of procedure
6.1 Assignment to network connection
Re-title sub-clause 6.1 as ‘61 Use of the network serviceJJ.
Add the following title and text as the new sub-clause 6.1.1:
Assignment to network connection when operating over CONS
6.1.1
This procedure is used only when operating over the connection-oriented network service.
Re-number sub-clauses 6.1.n as 6.1.1.nJ respectively.
Add the following title and text as the new sub-ciause 6.1.2:
6.1.2 Transmission over CLNS
This procedure is used only when operating over the connectionless network service.
6.1.2.1 Purpose
The procedure is used to transmit TPDUs over the connectionless network service.
6.1.2.2 Network service primitives
The procedure makes use of the following network service primitive:
N-U N IT DATA.
6.1.2.3 Procedure
Each TPDU shall be transmitted in a single invocation of the connectionless network service, over a pre-existing
association between a pair of NSAPs. The association is considered by transport entities as permanently
established and available.
6.2 Transport protocol data unit (TPDU) transfer
In sub-clause 6.2.2, after the phrase ‘hetwork service primitives”, add ‘Men operating over CONS”
Add the following text to the end of sub-clause 6.2.2:
The procedure uses the following network service primitive when operating over CLNS:
N-UNITDATA.
Add before the second paragraph of sub-clause 6.2.9, the following text:
When operating over CLNS, the transport entities shall transmit and receive all TPDUs as NS-user data
parameters of N - U N IT DATA p ri mit i ves .
In sub-clause 6.2.8, add to the beginning of the second paragraph, “When operating over CONS and”.
7
---------------------- Page: 10 ----------------------
ISO/IEC 8073 : 1988/Add.2 : 1989 (E)
6.3 Segmenting and reassembling
6.4 Concatenation and separation
In sub-clause 6.4.2, add to the beginning of note 3, “When operating over CONS,”.
Add the following text to the end of note 9:
When operating over CLNS. the number of TPDUs that may be concatenated is bounded by the number of
transport connections established between two NSAPs and/or the maximum available NSDU size.
6.5 Connec tion establishment
6.6.1 Purpose
6.6.2 Network service primitives
Add to the beginning of the sentence, When operating over CONS,”.
Add the following text to the end of sub-clause 6.5.2:
When operating over CLNS, the procedure uses the following network service primitive:
N - U N I TDATA.
6.6.3 TPDUs and parameters used
6.6.4 Procedure
Re-title sub-clause 6.5.4 as ‘(6.6.4 Procedure for operating over CONS ”.
Insert the following text as sub-clause 6.5.5:
6.6.6 Procedure for operating over CLNS
A transport connection is established by means of one transport entity (the initiator) transmitting a CR
TPDU to the other transport entity (the responder), which replies with a CC TPDU. During this exchange,
all information and parameters needed for the transport entities to operate shall be exchanged or negotiated.
When an unexpected duplicated CR TPDU is received (with class 4 as preferred class) a CC TPDU shall be
returned.
After receiving the CC TPDU. the initiator shall acknowledge the CC TPDU as defined in table 5 (see 6.13 of
IS0 8073).
The following information is exchanged:
a) references : Each transport entity chooses a reference to be used by the peer entity which is 16-bits long
and which is arbitrary under the following restrictions:
1) it shall not already be in use nor frozen (see 6.18 of ISO/IEC 8073).
2) it shall not be zero.
This mechanism is symmetrical and provides identification of the transport connection itself. The range
of references used for transport connections, in a given transport entity, is a local matter.
8
---------------------- Page: 11 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
b) called and calling TSAP-IDS (optional): Indicates the calling and called transport service access points.
When either the network address unambiguously defines the transport address, this information may be
omitted.
c) initial credit:
d) user data: Up to 32 octets.
e) acknowledgment time:
f) checksum parameter:
g) protection parameter: This parameter and its semantics are user defined.
h) protocol class: Class 4 is the only valid value for the preferred protocol class proposed by the initiator,
and for the class selected by the responder. An alternative class is not permitted.
The following negotiations take place:
i) TPDU size: The initiator may propose a maximum size for TPDUs in the set of values available isee 13.3.4b),
ISO/IEC 80731. This value may be limited by the maximum available NSDU size if known, and cannot exceed the
maximum NSDU size for connectionless network service as defined in IS0 =/Add. 1.
The responder may accept this value or respond with any value between 128 and the proposed value in the set of
values available isee 13.3.4b3, of ISO/IEC 80731.
NOTES
1 The length of the CR TPDU does not exceed 128 octets (see 13.3 of ISO/IEC 8073).
2 The transport entities may have knowledge, by some local means, of the maximum available NSDU size.
j) normal or extended format: Either normal or extended is available. When extended is used this applies to CDT,
TPDU-NR, ED TPDU-NR, YR-TU-NR and YR-EDTU-NR parameters.
k) checksum selection: This defines whether or not TPDUs of the connection are to include a checksum.
I) quality of service parameters: This defines the throughput, transit delay, priority and residual error rate.
NOTE - The transport service defines transit delay as requiring a previously stated average TSDU size as a basis for
any specification. This protocol as specified in 13.3.4.11) of ISO/IEC 8073, uses a value at 128 octets. Conversion to
and from specifications based upon some other value is a local matter.
m) use of expedited data transfer service [item r) in ISO/IEC 80731: This allows both TS-users to negotiate the use or
non-use of the expedited data transport service as defined in the transport service (IS0 8072).
The following information is sent only in the CR TPDU :
n) version number [item s) in ISO/IEC 80731: This defines the version of the transport protocol standard used for this
connection.
6.6 Connection refusal
6.7 Normal release
Re-number sub-clauses 6.7.n and all references to them as 6.7.l.n respectively, and insert a new title:
6.7.1 Normal release when operating over CONS
Add the following text as sub-clause 6.7.2:
9
---------------------- Page: 12 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
CLNS
6.7.2 Normal release when operating over
6.7.2.1 Purpose
The release procedure is used by a transport entity in order to terminate a transport connection
6.7.2.2 Network service primitives
The procedures makes use of the following network service primitive:
N - U N I TD ATA.
6.7.2.3 TPDUs and parameters used
The procedure uses the following TPDUs and parameters:
a) DRTPDU:
- reason:
- user data:
- SRC-REF:
- DST-REF;
b) DCTPDU.
6.7.2.4 Procedure
When the release of a transport connection is to be initiated, a transport entity shall send a DR TPDU and
shall discard all subsequently received TPDUs except for a DR or a DC TPDU.
On the receipt of a DR or a DC TPDU. it shall consider the transport connection to be released and the
local reference shall be frozen (see 6.8). If a CC TPDU has been previously sent or received by the transport
connection, then the remote reference is known and shall be used for the DST-REF in the DR TPDU to be
sent. If the remote reference is not known, then the DST-REF in the DR TPDU may be set to zero, or the
entity may wait until a CC TPDU is received before sending the DR TPDU.
NOTE - In case that the entity decides to wait for the arrival of the CC TPDU for the connection. deadlock.
which could result from a CC TPDU that never arrives. is prevented by the expiration of the CR TPDU
retransmission counter, which forces the DR TPDU to be sent.
A transport entity which receives a DR TPDU shall
a) consider the transport connection to be released if it has previously sent a DR TPDU for that connection:
b) consider the transport connection to be refused (see 6.6) if it has previously sent a CR TPDU for that
connection and no CC TPDU has been received in acknowledgment:
c) consider the transport connection to be released and send a DC TPDU in all other cases. If the received
DR TPDU has the DST-REF field set to zero, then a DC TPDU with SRC-REF set to zero shall be sent,
regard less of the local reference.
6.8 Error release
Error release when operating over CONS”.
Re-title sub-clause 6.8, as 8.8
6.9 Association of TPDUs with transport connections
Re-number sub-clauses 6.9.n and all references to them as 6.9.1 .n respectively, and insert a new title:
10
---------------------- Page: 13 ----------------------
: 1989 (E)
ISO/IEC 8073 : 1988/Add.2
transport connections when operating over CONS
6.9.1 Association of TPDUs with
Add the following text as sub-clause 6.9.2:
6.9.2 Association of TPDUs with transport connections when operating over CLNS
6.9.2.1 Purpose
This procedure is used to interpret a received NSDU as TPDU(s) and, if possible. to associate each such
TPDU with a transport connection.
6.9.2.2 Network service primitives
This procedure makes use of the following network service primitive:
N - U N I TD ATA.
6.9.2.3 TPDUs and parameters used
This procedure makes use of the following TPDUs and parameters:
a) all TPDUs except CR TPDU;
- DST-REF;
b) CR. CC, DR and DC TPDUs;
- SRC-REF.
6.9.2.4 Procedures
6.9.2.4.1 Identification of TPDUs
If the received NSDU cannot be decoded (i.e., does not contain one or more correct TPDUs) or is corrupted
(i.e., contains a TPDU with a wrong checksum) then the transport entity shall ignore (discard) the TPDUs.
If the NSDU can be decoded and is not corrupted, the transport entity shall invoke the separation procedures
and for each of the individual TPDUs in the order in which they appear in the NSDU apply the procedure in
6.9.2.4.2.
0.9.2.4.2 Association of individual TPDUs
Association of a received TPDU with a transport connection is generally performed by attempting to match
the DST-REF in the received TPDU and the NSAP pair over which it was received with those of an existing
transport connection. There are three exceptions to this general procedure: when the received TPDU is a
CR TPDU. the SRC-REF is used instead of the DST-REF; when the received TPDU is either a DR or a DC
TPDU. the SRC-REF is used in addition to the DST-REF: and when the received TPDU is a CC TPDU. whose
DST-REF parameter identifies an open connection (one for which a CC TPDU has been previously received),
then the SRC-REF is used in addition to the DST-REF.
The following actions shall be taken in consequence to the inability to match the TPDU to an existing transport
connection:
a) For a CR TPDU, a new transport connection shall be created.
b) For a CC TPDU, a DR TPDU shall be sent using the SRC-REF and DST-REF froin the received CC
TPDU as the DST-REF and SRC-REF, respectively, of the DR TPDU.
c) For a DR TPDU. there are four cases:
1) if a CR TPDU is unacknowledged for the connection identified by the DST-REF in the DR TPDU,
then the DR TPDU is associated with that connection regardless of the SRC-REF in the DR TPDU.
---------------------- Page: 14 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
2) if the CR TPDU for the connection identified by the DST-REF of the DR TPDU has been acknowl-
a DC TPDU using the SRC-REF of the DR TPDU
edged and the SRC-REF is not as expected, then
as DST-REF is sent and no association is made.
3) if the DST-REF in the DR TPDU is zero and there is an unacknowledged CC TPDU or a T-CONNECT
response is awaited for a transport connection holding remote reference equal to the SRC-REF of the
DR TPDU. then the DR TPDU is associated with that transport connection.
4) in all other situations, the DR TPDU is associated with the transport connection identified by the
DST-REF of the DR TPDU.
d) For all other TPDU types, the TPDU is discarded.
6.10 Data TPDU numbering
6.11 Expedited data transfer
Re-number sub-clauses 6.11.n, as 6.11.1.n respectively, and insert a new title:
e
6.11.1 Expedited data transfer when operating over CONS
Add the following text as sub-clause 6.11.2:
6.11.2 Expedited data transfer when operating over CLNS
6.11.2.1 Purpose
Expedited data transfer procedures are selected during connection establishment.
6.11.2.2 Network service primitives
The procedure makes use of the following network service primitive:
N - U N I TDATA.
6.11.2.3 TPDUs and parameters used
Q
The procedures makes use of the following TPDUs and parameters:
a) EDTPDU:
- ED TPDU-NR:
b) EATPDU:
- YR-EDTU-NR.
6.11.2.4 Procedures
The TS-user data parameter of each T-EXPEDITED DATA request shall be conveyed as the data field of an
Expedited Data (ED) TPDU.
Each ED TPDU received shall be acknowledged by an Expedited Acknowledge (EA) TPDU.
at any time for each direction of a transport
No more than one ED TPDU shall remain unacknowledged
connection.
An ED TPDU with a zero length data field shall be treated as a protocol error (see 6.22).
12
---------------------- Page: 15 ----------------------
ISOAEC 8073 : 1988/Add,2 : 1989 (E)
6.12 Reassignment after failure
Re-titie sub-clause 6.18 as ‘y1.12 Reassignment after failure when operating over CONS”.
6.13 Retention until acknowledgment of TPDUs
6.13.1 Purpose
6.18.2 Network service primitives
Add to the beginning of the first sentence, “When operating over CONS,”.
Add to the end of sub-clause 6.19.2 the following text:
When operating over CLNÇ, the procedure uses the following network service primitive:
N - U N I TDATA .
Add the following qualification after the word UlUOTES” in sub-clause 6.13.4, “(Only apply when operating over CONS)”.
6.14 Resynchronization
6.15 Multiplexing and demultiplexing
Re-title sub-clause 6.15 as “6.15 Multiplexing and demultiplexing when operating over CONS”.
Sub-clauses 6.16 to 6.21 remain unchanged.
6.22 Treatment of protocol errors
Renumber sub-clauses 6.22.n and all references to them as 6.22.1.n respectively, and insert a new title:
6.22.1 Treatment of protocol errors when operating over CONS
O
Add the following text as sub-clause 6.22.2:
6.22.2 Treatment of protocol errors when operating over CLNS
6.22.2.1 Purpose
The procedure for treatment of protocol errors is used to deal with invalid TPDUs.
6.22.2.2 TPDUs and parameters used
The procedure uses the following TPDUs and parameters:
a) ERTPDU;
- reject cause:
- invalid TPDU;
b) DRTPDU;
- reason.
13
---------------------- Page: 16 ----------------------
I
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
6.22.2.3 Procedure
Invalid TPDUs and protocol errors shall be ignored (no action and TPDU discarded, or responded to with an
ER TPDU), except for the following case: a CC TPDU is received in which the class field does not specify
class 4 and a previously sent CR TPDU has not yet been acknowledged. In this case, the transport connection
shall be terminated (See 6.7).
6.23 Splitting and recombining
Re-title sub-clause 6.23 as q.23 Splitting and recombining when operating over CONS”
14
---------------------- Page: 17 ----------------------
ISO/IEC 8073 : 198WAdd.2 : 1989 (E)
7 Protocol classes
Re-title the right hand column, “4” an table 6 as “Class 4 CONS”
Add the following column to the right hand side of table 6. The names of the protocol mechanisms are included to help
c row re fere ncing .
Assignment to network connection
TPDU transfer
Segmenting and reassembling
Concatenation and separation
Connection establishment
Connection refusal
Normal release
Error release
Association of TPDUs with transport connection
TPDU numbering
Expedited data transfer
Reassignme nt aft er failure
Retention until acknowledgement of TPDUs
Resynchronization
Multiplexing and demultiplt?xing
Explicit fiow control (with)
Explicit fiow control (without)
Checksum (use of)
Checksum (non-use of)
Frozen references
Retransmission of time-out
Resequencing
Inactivity control
Treatment of protocol errors
Splitting and recombining
Clauses 8 to 11 remain unchanged.
12 Specification for class 4 : Error detection and recovery class
12.1 Functions of class 4
Add the following new sub-clause title before the first paragraph:
12.1.1 Functions of class 4 when operating over CONS
Add the followang text as sub-clause 12.1.2:
15
---------------------- Page: 18 ----------------------
ISO/IEC 8073 : 19WAdd.2 : 1989 (E)
12.1.2 Functions of class 4 when operating over CLNS
Class 4 provides flow control between peer transport entities, the capability to detect and recover from errors
which occur as a result of a low grade service available from the network service provider and resilience from
failure of the peer entity -the kind of errors to be detected include: TPDU loss, TPDU delivery out of sequence,
TPDU duplication and TPDU corruption - these errors may affect control TPDUs as well as data TPDUs.
The detection of errors is made by use of DT TPDU numbering, by time-out mechanisms and additional
procedures such as the use of a checksum mechanism. The use of the checksum mechanism shall be av
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.