connection
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...
ISO 7498 Information processing systems - Open systems inter-
connection - Basic Reference Model
...
...
DP aaaa Information processing systems - Open systems inter-
connection - Transport service definition (N1169).
...
...
DP bbbb Information processing systems - Open systems inter-
connection - Connection-oriented network service
...
... DP bbbb Information processing systems - Open systems inter-
connection - Connection-oriented network service
definition (N729)
...
... The services provided by the protocol described in this
document are connection-oriented services. They are defined in
document DP ...
... Transport Layer
5.3.1 Connection Oriented Functions
5.3.1.1 Overview of Functions
...
... 5.3.1.1.1 Establishment Phase
The goal of the establishment phase is to establish a
transport connection, i.e., between two transport users. The
functions of transport layer ...
... services.
o Decide whether to multiplex multiple transport connection
onto a single network connection.
...
... o Decide whether to multiplex multiple transport connection
onto a single network connection.
o Establish the optimum TPDU size.
...
...
o Provide a means to distinguish between two different
transport connections.
o Transportation of user's data.
...
... transport of TSDUs between the session entities connected
by the transport connection. This purpose is achieved by means of
two-way simultaneous communication in the Transport protocol and by
...
... Demultiplexing
A function used to share a single network connection
between two or more transport connections.
...
... A function used to share a single network connection
between two or more transport connections.
o Splitting and Recombing
...
...
A function allowing the simultaneous use of two or more
network connections to support the same transport connec-
tion.
...
... duplication, misordering or misdelivery of TPDUs.
o Transport Connection Identification
A means to uniquely identify a transport connection ...
... Transport Connection Identification
A means to uniquely identify a transport connection
between the pair of transport entities supporting the
...
... between the pair of transport entities supporting the
connection during the lifetime of the transport
connection.
...
... 5.3.1.1.3 Release Phase
A function to provide a disconnection of the transport
connection, regardless of the current activity.
5.3.1.2 Classes ...
...
Note that with the exception of classes 0 and 1, transport
connections of different class may be multiplexed together
onto the same network connection ...
... transport
connections of different class may be multiplexed together
onto the same network connection.
5.3.1.2.2 Options within Classes ...
... Classes and options within classes are negotiated during
the connection establishment phase.
5.3.1.2.4 Choice of the Class ...
... TS-User requests either transmission of
user data during the connection phase, or use of
Expedited data transfer, then Class ...
... requirements. Its main purpose is to provide a basis for the decision
regarding which class of transport connection should be used on top of
...
...
a given network connection.
Type A: Network connection ...
... network connection.
Type A: Network connection with acceptable residual error
rate (for example not signalled by 'clear' or 'reset')
and acceptable rate of signalled failures.
...
... and acceptable rate of signalled failures.
Type B: Network connections with acceptable residual error
rate (for example not signalled by 'clear' or 'reset')
but unacceptable rate of signalled failures.
...
... but unacceptable rate of signalled failures.
Type C: Network connections with residual error rate not
acceptable to the TS-user.
...
... entity is aware of the
quality of service provided by particular Network connections.
5.3.1.3 Potential Functions
...
... o provision for blocking
o temporary release of network connections
5.4 Model of the Transport Layer ...
... Data Unit exchanges between the peer Transport Protocol
entities supporting a Transport Connection. These protocol exchanges
are effected using the services ...
... NSAPs.
Transport connection endpoints are identified in end systems
by an internal, implementation dependent, mechanism so that the
...
...
Several functions are described as 'inherent' or 'pervasive'.
Inherent functions must be invoked for every transport connection.
Pervasive functions are optional, but if one is invoked for the first
transport connection over a ...
... Inherent functions must be invoked for every transport connection.
Pervasive functions are optional, but if one is invoked for the first
transport connection over a network connection, it must also be invoked
for any and all other transport connections ...
... .
Pervasive functions are optional, but if one is invoked for the first
transport connection over a network connection, it must also be invoked
for any and all other transport connections which use that network
connection ...
... transport connection over a network connection, it must also be invoked
for any and all other transport connections which use that network
connection during its lifetime.
...
... network connection, it must also be invoked
for any and all other transport connections which use that network
connection during its lifetime.
...
... This function is inherent.
Before a transport connection can be created or used, it must
be assigned to one (or more if splitting function is being used)
...
... can be created or used, it must
be assigned to one (or more if splitting function is being used)
network connection(s). Both transport entities involved must become
aware of this assignment. A transport connection ...
... network connection(s). Both transport entities involved must become
aware of this assignment. A transport connection may be assigned to a
suitable existing network connection; one or more new network
connections ...
... aware of this assignment. A transport connection may be assigned to a
suitable existing network connection; one or more new network
connections may also be created for the purpose.
...
... transport connection may be assigned to a
suitable existing network connection; one or more new network
connections may also be created for the purpose.
...
... created for the purpose.
An existing network connection, which connects the relevant
transport entities, is unsuitable for assignment of a transport
connection if, for example:
...
... An existing network connection, which connects the relevant
transport entities, is unsuitable for assignment of a transport
connection if, for example:
o the quality of service ...
...
o the quality of service needed for the transport connection
can not be met by using or enhancing the network
connection.
...
... quality of service needed for the transport connection
can not be met by using or enhancing the network
connection.
o the protocol class ...
...
o the protocol class preferred or in use for the transport
connection is incompatible with the current usage of the
network connection as regards the use of pervasive
...
... protocol class preferred or in use for the transport
connection is incompatible with the current usage of the
network connection as regards the use of pervasive
functions (e.g., multiplexing).
...
... multiplexing).
When a new network connection is created, the quality of
service requested is a local matter, though it will normally be
...
... quality of
service requested is a local matter, though it will normally be
related to the requirements of transport connection(s) expected to be
assigned to it.
...
... assigned to it.
A Network Connection with no transport connections will be
available after initial establishment or because explicit
...
...
A Network Connection with no transport connections will be
available after initial establishment or because explicit
disconnection of all the transport connections ...
... transport connections will be
available after initial establishment or because explicit
disconnection of all the transport connections previously assigned to
it has taken place. Either Transport entity ...
... Transport entity may as a local
matter choose to disconnect the Network Connection or assign other
Transport Connections to it.
...
... may as a local
matter choose to disconnect the Network Connection or assign other
Transport Connections to it.
6.2 Transport Protocol ...
... The data field of Data TPDUs may contain any number of octets
up to an agreed maximum as negotiated at connection time.
A transport ...
... the end of the NSDU.
The concatenated set of TPDUs may be for the same or different
transport connections. An implementation shall accept concatenated
TPDUs and may concatenate TPDUs before transmission. The transport
...
... entity shall not send a concatenated set of TPDUs which exceeds twice
the overall maximum TPDU length for all the TCs assigned to the
network connection.
6.5 Connection Establishment ...
... network connection.
6.5 Connection Establishment
Purpose: Creation of a new transport connection ...
... This function is inherent:
A transport connection is established by means of one
transport entity (the ...
... entity (the responder), which replies
with a Connection Confirm (CC) TPDU. Before sending the CR TPDU, the
...
... ) TPDU. Before sending the CR TPDU, the
initiator assigns the transport connection being created to one (or
more if the splitting function is being used) network connection ...
... transport connection being created to one (or
more if the splitting function is being used) network connection(s).
It is this set of network connections over which the TPDUs are sent.
...
... more if the splitting function is being used) network connection(s).
It is this set of network connections over which the TPDUs are sent.
During this exchange, all information and parameters needed for the
transport entities to operate must be exchanged or negotiated.
...
... and therefore avoids the need to assign a status of master or slave to
partners and avoids call collision. This mechanism also provides
identification of the transport connection independent of the network
connection. The range of References used for transport connections ...
... partners and avoids call collision. This mechanism also provides
identification of the transport connection independent of the network
connection. The range of References used for transport connections, in
...
... transport connection independent of the network
connection. The range of References used for transport connections, in
a given transport entity ...
... which
includes resynchronization (see "Resynchronization", Section 6.15) is
preferred, resynchronization will occur if a reset is signalled during
connection establishment.
When the responder ...
... o checksum selection. This defines whether or not TPDUs of
the connection are to include a checksum.
...
... version number. This defines the version of the transport
protocol standard used for this connection.
o security parameter ...
... mandatory alternative defined in Section 9.
During the establishment phase of the transport connection,
the use of the expedited data option field of CR/CC ...
... Connection Refusal
Purpose: Refusal of the transport connection.
TPDUs and fields used:
...
... Description:
If a transport connection cannot be accepted, the called
transport entity shall respond to the ...
... CR TPDU with a DR TPDU. The
clearing reason shall indicate why the connection was not accepted.
The source reference field in the DR TPDU is set to zero ...
... ERR TPDU. On receipt of this TPDU,
the calling entity will regard the connection as closed.
6.7 Release
...
... Variants: 'implicit' or 'explicit'
Purpose: Termination of the transport connection.
Network Service ...
... transport entity disconnects
a transport connection by disconnecting the network connection to
which it is assigned. Similarly when a transport ...
... entity disconnects
a transport connection by disconnecting the network connection to
which it is assigned. Similarly when a transport entity ...
... transport entity is informed
that the network connection has been disconnected by the peer
transport entity, this should be considered as a ...
... transport entity, that entity should consider the transport connection
not to exist (note 1). After the sending of a DR TPDU, other TPDUs
...
... 6.8 Implicit Termination
Purpose: Termination of a Transport Connection on the
occurrence of a signalled error for which recovery functions are not
operative.
...
... Description:
When, on the network connection to which a Transport
Connection is assigned, an N-DISCONNECT or N-RESET ...
...
When, on the network connection to which a Transport
Connection is assigned, an N-DISCONNECT or N-RESET Indication occurs,
...
... N-RESET Indication occurs,
both transport entities shall consider that the transport connection
no longer exists, and so inform the session entities.
...
... entity considers use of the reference to be
ended. Therefore, the reference should not be re-used for further
connections. (In practice, the reference may be re-used after a
reasonable period when it is possible to be reasonably certain that
the remote transport ...
...
A DR TPDU can be received for a transport connection which
does not exist. Rather than treating this as an error, a DC TPDU
...
... a multiplexing class exist over the network connection, or when no
transport connections exist. At other times it is a protocol error.
...
... class exist over the network connection, or when no
transport connections exist. At other times it is a protocol error.
...
... Description:
DT TPDUs transmitted in each direction on a transport
connection bear a sequence number 'TPDU-NR'. Its value in the first
...
... sequence number 'TPDU-NR'. Its value in the first
DT TPDU in each direction after connection establishment will be zero.
Thereafter each TPDU had 'TPDU-NR' one greater than the previous.
...
...
In the sections that follow, the relationships 'greater than'
and 'less than' are used in connection with TPDU numbers. In all
such uses, the numbers being compared cover a range less than the
...
...
There may only be one ED TPDU unacknowledged at any time for each
direction of a transport connection.
In the 'network ...
... 6.12 Reassignment
Purpose: Assignment of a Transport Connection to a different
Network Connection.
...
...
Purpose: Assignment of a Transport Connection to a different
Network Connection.
TPDUs and Fields Used:
...
... Description:
When the Network Connection to which a Transport Connection was
assigned no longer exists, the Transport Connection ...
...
When the Network Connection to which a Transport Connection was
assigned no longer exists, the Transport Connection can be assigned to
...
... Network Connection to which a Transport Connection was
assigned no longer exists, the Transport Connection can be assigned to
another Network Connection.
...
... assigned no longer exists, the Transport Connection can be assigned to
another Network Connection.
When one transport ...
... When one transport entity has assigned the Transport Connection,
it is important that the other transport entity ...
... it is important that the other transport entity recognise to which
Network Connection it has been assigned. This can only take place when it
...
...
has received a TPDU for the Transport Connection on a Network Connection
with calling and called network ...
...
has received a TPDU for the Transport Connection on a Network Connection
with calling and called network addresses ...
... DR.
The Transport Connection shall be recognised as having been
assigned to the Network Connection on which the TPDU was received.
...
... The Transport Connection shall be recognised as having been
assigned to the Network Connection on which the TPDU was received.
6.13 Reassignment After Failure
...
...
When a N-DISCONNECT Indication arrives for the network connection
to which a transport connection is assigned, the transport connection ...
... N-DISCONNECT Indication arrives for the network connection
to which a transport connection is assigned, the transport connection must
be reassigned by its initiator ...
... network connection
to which a transport connection is assigned, the transport connection must
be reassigned by its initiator (see "Reassignment")
...
...
If the reassignment has not successfully occurred within a time
of T-wait seconds, then the transport connection must be considered as
non-existent by both transport entities.1
...
... destination reference;
nevertheless it can be distinguished from a new
connection attempt by having the same source
reference.
...
... After each TPDU is acknowledged, as shown in Figure 5,
the copy need not be retained. Copies may also be discarded when
the transport connection ceases to exist.
TPDU ACKNOWLEDGED BY
...
... 6.15 Resynchronization
Purpose: To restore the connection to normal after an
error.
...
... Description:
After the reset of an underlying network connection,
the resynchronization procedures below are carried out by both
transport entities.
...
... transport entities.
After a network connection failure, the reassignment after
failure function is invoked and then the resynchronization function.
The sequence of events at the two transport ...
...
o if the first received TPDU is a CR and the transport
connection is not idle, this means that a CC TPDU is
retained: then retransmit it followed by any ED TPDU
...
... the resynchronization mechanism. This possibility may be used to remove
congestion within the network connection.
6.16 Multiplexing ...
... Demultiplexing
Purpose: Concurrent sharing of a network connection by several
transport connections.
...
...
Purpose: Concurrent sharing of a network connection by several
transport connections.
TPDUs and Fields Used:
...
... This function is pervasive.
When this function is in operation, more than one transport
connection can be simultaneously assigned to the same network connection.
...
...
When this function is in operation, more than one transport
connection can be simultaneously assigned to the same network connection.
Every TPDU (including DT TPDUs) must carry the destination ...
... Every TPDU (including DT TPDUs) must carry the destination
reference, to identify the transport connection to which it refers.
6.17 Explicit Flow ...
... Description: When a transport entity determines that a particular
connection has terminated, the reference shall be placed in a frozen state
...
... 6.22 Inactivity Control
Purpose: To cope with unsignalled termination of a network
connection.
TPDUs and Fields Used:
...
... of
ERR TPDU, since it is expected that the offender will either correct
the error, or close the connection.
Action to be done by the receiver ...
... Action to be done by the receiver depends on local implementation
decision; e.g., freeze the connection, report to management, disconnect.
...
... 6.24 Splitting and Recombining
Purpose: To allow a transport connection to make use of
multiple network connections to provide additional resilience against
...
... Purpose: To allow a transport connection to make use of
multiple network connections to provide additional resilience against
network failure, to increase throughput, or for other reasons.
...
... Class 4.
When this function is being used, a transport connection is
assigned (see Section 6.1) to multiple network connections ...
... transport connection is
assigned (see Section 6.1) to multiple network connections. TPDUs for the
...
...
connection may be sent over any assigned network connection. The
resequencing function of Class ...
...
connection may be sent over any assigned network connection. The
resequencing function of Class 4 (see Section 6.21) is used to ensure
...
...
entity following the negotiation rules, only the network connection
over which the CR TPDU was sent may be used for this transport
connection ...
... network connection
over which the CR TPDU was sent may be used for this transport
connection.
The splitting function should only be used where the
...
...
The splitting function should only be used where the
supporting network connections provide similar transmit delay.
Protocol Mechanism ...
... Concatenation and Separation * * * *
Connection Establishment * * * * *
Connection Refusal * * * * *
...
... Connection Establishment * * * * *
Connection Refusal * * * * *
Release implicit *
...
... The characteristic of this class is that it provides
the simplest type of transport connection and fully compatible
...
... The class is designed for use in association with
network connections of type A (see 5.3.1.2.4.).
7.0.2 Functions of Class ...
... This class is designed to have minimum functionality.
It provides only the functions needed for connection
establishment with negotiation, data transfer with segmenting and
...
... Connection Establishment Phase
Connection shall be made in accordance with the
general rules (Assignment of Network Connection, Connection
Establishment ...
... Connection shall be made in accordance with the
general rules (Assignment of Network Connection, Connection
Establishment and Connection Refusal) with the following
...
... Connection shall be made in accordance with the
general rules (Assignment of Network Connection, Connection
Establishment and Connection Refusal) with the following
restrictions:
...
... general rules (Assignment of Network Connection, Connection
Establishment and Connection Refusal) with the following
restrictions:
...
... 7.0.3.3 Release Phase
There is no explicit transport connection release
procedure for this class. The lifetime ...
... procedure for this class. The lifetime of the transport connection
is directly correlated to the lifetime of the network connection ...
... transport connection
is directly correlated to the lifetime of the network connection.
7.0.4 Connection Establishment ...
... Class 0
The connection establishment function is used
with the contraint that only the transport entity ...
... transport entity which has
requested the establishment of the network connection may send the
CR TPDU. If the calling transport ...
... following subsections apply only when the transport layer is in the
data transfer phase, that is after completion of Transport
Connection establishment.
7.0.5.2 Transport ...
... The characteristic of this class is that it
provides a basic transport connection with minimal overheads.
...
... criteria. Class 1 has been designed to be used in
association with type B network connections.
7.1.2 Functions of Class ...
... error
recovery, expedited data transfer, disconnection, and also the
ability to support consecutive Transport connections on a network
connection.
...
... data transfer, disconnection, and also the
ability to support consecutive Transport connections on a network
connection.
This class ...
... Class 1 provides the possibility of conveying
data in the connection request and confirm commands.
7.1.3.2 Numbering of Data TPDU
...
... Each Data TPDU transmitted between transport entities for
each direction of transmission in a transport connection is
sequentially numbered.
...
... ('confirmation of receipt' variant) - optional
The variant to be used is negotiated during the
Connection Establishment Phase. The default option is the "AK TPDU"
variant. Use of Network Layer ...
... Class 1
The 'assignment to network connection' and
'connection establishment' mechanisms are used. From the point at
...
... The 'assignment to network connection' and
'connection establishment' mechanisms are used. From the point at
which a transport entity ...
... CC accepting the use of Class 1 the following mechanisms must be
available to deal with signalled errors during connection
establishment:
o Reassignment after failure
...
... The 'Spurious Disconnect' mechanism is used to
deal with receipt of a DR TPDU for an unrecognised Transport
Connection.
7.1.5.2 Procedure for Expedited Data Transfer ...
... DC and DR will be accepted
and interpreted as the completion of the connection release
sequence. The related Reference will become unassigned.
...
...
way to multiplex several transport connections onto a single network
connection. This class has been designed to be used in association ...
...
way to multiplex several transport connections onto a single network
connection. This class has been designed to be used in association
...
... class has been designed to be used in association
with type A network connections.
Use of Explicit Flow ...
... avoid congestion at end-points and on the network connection.
Typical use is when traffic is heavy and continuous, or when there
...
... Flow Control (optional)
The objective is to provide a basic transport
connection with minimal overheads suitable when independence of
transport and ...
... with minimal overheads suitable when independence of
transport and network connection lifetime is desirable. The class
...
... would typically be used for unsophisticated terminals, and when no
multiplexing onto network connections is required. Expedited data
is never available.
...
...
Class 2 provides transport connections with or
without individual flow control - no error detection or error
recovery ...
...
If the network resets or clears, the transport
connection is terminated without the transport clearing sequence
and the transport ...
... Connection Establishment Phase
The connection establishment function shall be used.
7.2.3.1.1 User Data ...
...
Class 2 provides the possibility to convey data in the
connection request and confirm commands.
7.2.3.2 Connection ...
... 7.2.3.3 Release Phase
The release of a transport connection results either
from the use of the 'explicit' variant of the release function or
from the Implicit Termination function.
...
... Each Data TPDU transmitted between transport entities
for each direction of transmission in a transport connection is
sequentially numbered.
...
... data will arrive after the expedited data.
7.2.4 Connection Establishment Procedures for Class 2
...
...
See Section 6.5 for reference assignment. Receipt of
any TPDU with a reference that is not assigned to a transport
connection other than a Disconnect Request (DR) or Connection
Request (CR ...
... any TPDU with a reference that is not assigned to a transport
connection other than a Disconnect Request (DR) or Connection
Request (CR) will be ignored.
...
... CR/CC TPDU using
the 'connection establishment' function. Since the multiplexing
function is in use, then more than one transport connection ...
... connection establishment' function. Since the multiplexing
function is in use, then more than one transport connection may be
assigned to the same network connection concurrently. The
...
... function is in use, then more than one transport connection may be
assigned to the same network connection concurrently. The
restrictions of Class 0 does not apply to this class ...
... The data transfer procedures described in the
following section apply independently to each transport connection
existing between two transport entities.
...
... Flow Control is Used)
On each transport connection the transmission of Data
TPDUs is controlled separately for each direction and is based on
authorization from the ...
... Each Data TPDU transmitted between transport entities,
for each direction of transmission in a transport connection, is
sequentially numbered.
...
... range 0 to (2**n)-1.
At connection establishment time both Transport
entities initialize their T(S) and T(R) counts to zero (i.e. the
...
... first Data TPDU to be transmitted between transport entities for a
given direction of data transmission after the connection
establishment has a TPDU-NR field set to zero).
...
... 7.2.5.4.2 Window Definition
For each transport connection and for each direction
of data transmission a 'transmit window' is defined as the (possibly
null) ordered set of consecutive data TPDUs authorized to be
...
...
If the network resets or clears the network
connection, all transport connections are terminated without the
transport clearing sequence. The References become frozen.
...
... If the network resets or clears the network
connection, all transport connections are terminated without the
transport clearing sequence. The References become frozen.
...
... For Class 2 the explicit variant of the 'release'
mechanism is used, enabling transport connections to be cleared
independently of the underlying network connection.
...
... mechanism is used, enabling transport connections to be cleared
independently of the underlying network connection.
7.2.7 Treatment of Invalid TPDUs
...
... Class 3 has
been designed to be used in association with type B network connections.
7.3.2 Functions of Class ...
... after a failure signalled by the network without informing the user
of the transport connection.
7.3.3.1 Error Recovery ...
... Credit may be reduced, by the use of the RJ TPDU.
7.3.4 Connection Establishment Procedure for Class 3
...
... - Reception of a DR will cause termination
of the transport connection as for Classes 1
and 2 (see 7.1.4).
...
... 2**n. When a transport entity receives an ED TPDU for a transport
connection, it shall respond by transmitting an expedited
acknowledgement (EA) TPDU.
...
... DC and DR will be accepted and
interpreted as the completion of the connection clearing sequence.
The related Reference will become unassigned.
...
... Class 4 has been designed to be usd in association
with network connections of type C.
7.4.2 Functions of Class ...
... is referred to as A/R. The values for these
timers may be conventionally established or may be established
at connection establishment time.
7.4.3.4 Local Retransmission ...
... 7.4.3.7 Inactivity Time
To protect against unsignalled breaks in the network
connection (Half-open connections), each transport entity ...
...
To protect against unsignalled breaks in the network
connection (Half-open connections), each transport entity maintains
...
... the required quality of service can be provided given the known
characteristics of the network connection.
7.4.3.10 Relationship of Times and Intervals
...
...
The length of sequence numbers may be negotiated at
connection establishment. Where other than the default length is
used, an extended header format is used for sequenced TPDUs
...
... allowing extended credit allocation.
7.4.4 Procedures for Connection Establishment Phase
The following features pertain to connection
establishment ...
... Connection Establishment Phase
The following features pertain to connection
establishment for Class 4:
...
...
o In Class 4, a connection is not considered
established until the successful completion
of a 3-way TPDU exchange. The sender ...
... timer restarted. After
transmission of the CR TPDU N times, the connection establishment
procedure is abandoned and the failure reported to the transport
...
... L (see section 7.4.3.6).
7.4.4.2 Incomimg Connection Request
An incoming connection ...
... obey the inactivity principles (see Section 7.4.5.8).
7.4.4.6 Unsuccessful Connection
When a DR ...
... transport entity may transmit the value it intends
to use for AL at connection establishment, as the 'Acknowledge
Time' parameter in the CR or CC ...
... TPDU (depending on whether the
transport entity is initiating or accepting the transport
connection). If this parameter is present in a received CR or CC
...
... timer is restarted. After N transmissions
(N-1 retransmissions) the connection is assumed to have failed and
the release phase is entered, and the transport user is informed.
...
... to the usual retransmission procedure. After N retransmissions, the
transport connection is considered disconnected, the Reference is
placed in the frozen state for a period L and retransmission ...
... 7.4.6.1 Unassigned Frozen References
When a transport connection is terminated, the
corresponding references cannot be immediately reused since TPDUs
containing these references may continue to exist in the network ...
...
state information, including the status of reference assignments,
all references relating to network connections whose transport
state information has been lost must be placed in the frozen ...
... x x x x x 8.3 1110xxxx
CC Connection Confirm x x x x x 8.4 1101xxxx
DR Disconnect Request x x x x x 8.5 10000000
...
...
1110 xxxx Connecting Request
1101 xxxx Connection Confirm
0101 xxxx Reject
0110 xxxx Data Acknowledgement
...
... Restrictions on its size are noted for each command.
8.3 Connections Request (CR)
...
...
CR: Connection Request Code: 1110
CDT: Initial Credit Allocation (set to 0000 in
...
... Bits 4-1 of octet 7 are reserved for options to be
used on the requested transport connection.
The use of bits ...
... This parameter defines the proposed maximum TPDU size
(in octets including the header) to be used over the requested
transport connection. The coding of this parameter is:
Parameter Code 11000000
...
... 32 octets.
8.4 Connection Confirm (CC)
...
...
CC : Connection Confirm
Code: 1101
...
... DST-REFERENCE : Reference
identifying the
requested transport
connection at the
remote transport
...
... class(es) not supported).
128 + 3 - Duplicated connection detected
128 + 4 - Mismatched references
...
... 128 + 7 - Reference overflow
128 + 8 - Connection request refused on this
network connection
...
... 128 + 8 - Connection request refused on this
network connection
128 + 9 - Not used
...
...
o A parameter may be provided to allow additional
information related to the clearing of the connection.
Parameter code: 11100000
...
... This field contains data of the TSDU being transmitted.
The length of this field is limited to the negotiated TPDU size for
this transport connection minus 3 octets in Classes 0 and 1,
and minus 5 octets (normal header format ...