This module implements the OSI Connection-Oriented Transport Protocol
specification International Standard ISO 8073; and for DEC OSF/1, the
Connectionless-Mode Transport Service Protocol International Standard ISO
8602. These protocols implement the OSI Reference Model Transport Layer 4.
These protocols, as well as the NSP protocol, implement the transport
protocols in the Digital Network Architecture.
The entities that constitute the OSI Transport module are listed below. The
indention indicates the hierarchical relationships between the entities.
OSI Transport
Application
Port
Template
Local NSAP
Remote NSAP
The Connection-Oriented Transport Service COTS provides transparent and
reliable transfer of data between Transport Service users. It operates over
the Network layer, and employs end-to-end protocols that enhance the inherent
characteristics of the underlying network service.
The protocol is structured to produce protocol classes that minimize the
possible incompatibilities and implementation costs. A protocol class is
selected for a particular transport connection, based on the characteristics
of the network service to be used, the requirements of the Transport Service
user, and the availability of classes at the remote Transport Service
provider.
This module implements class 0, class 2, and class 4 of the COTS protocol.
Class 0 is the simplest class. It sets up a network connection for each
transport connection requested, and assumes that the network connection does
not make errors. The transport protocol does neither sequencing nor flow
control, as it relies on the underlying network layer to perform everything
correctly.
Class 2, like class 0, is designed to be used over reliable networks. It
differs from class 0 in that two or more transport connections may be
multiplexed over the same network connection.
Class 4, the most complex of the protocols, is designed to work over
unreliable Network Services. It can handle the error detection and recovery
of lost transport packets. These packets are called TPDUs Transport
Protocol Data Units. Class 4 runs over either CLNS or CONS. Classes 0 and
2 run only over CONS.
The Routing module provides a connectionless network service CLNS; for more
information, refer to the Routing chapter.
The X.25 Access module, if configured into the system, provides a reliable
connection-oriented network service CONS.
The OSI Transport entity is the top-level entity in the hierarchy of
entities belonging to the OSI Transport module.
1 – character
CONGESTION AVOIDANCE
Default: True Value: Boolean
Enables the use of the automatic congestion avoidance mechanism to
reduce the transport window size in response to an indication from the
Network layer when operating on the Connectionless Network Service
CLNS.
DELAY FACTOR
Default: 4 Value: 2-15
Factor by which to multiply the current value of the round-trip delay
estimate status attribute in order to set a value for the
retransmission timer. This attribute works with protocol class 4 only.
DELAY WEIGHT
Default: 5 Value: 0-255
Relative weighting to apply to the current estimate and to a new sample
when estimating round-trip delay. This attribute works with protocol
class 4 only.
DISCONNECT HOLDBACK
Default: 0 Value: 0 - ( 2 to the 23 )
When operating over the Connection-Oriented Network Service CONS, the
length of the time to maintain a network connection for possible reuse
after all transport connections multiplexed upon it have been
disconnected. Specified in seconds. This characteristic may not be
changed while the transport entity is enabled.
ISO VERSION
Version number of ISO 8073 to which the implementation conforms. You
cannot modify this characteristic.
MAXIMUM MULTIPLEXING
Default: 2 to the 23rd Value: 1 - ( 2 to the 23rd)
Maximum number of transport connections that can be multiplexed on a
single network connection operating over the cons. You can modify
this characteristic to a lower value only when the entity is disabled.
This attribute applies only if X.25 has been configured in the kernel.
MAXIMUM NETWORK CONNECTIONS
Default: 2000 Value: 1 - ( 2 to the 23rd)
Maximum number of concurrent network connections that the OSI
transport protocol can use when operating over the cons. You can
modify this characteristic to a lower value only when the entity is
disabled.
MAXIMUM MULTIPLEXING
When operating over the Connection-Oriented Network Service CONS, the
maximum number of transport connections that can be multiplexed on any
single network connection. This characteristic can be increased only
when the transport entity is enabled. You can modify this
characteristic to a lower value only when the entity is disabled.
MAXIMUM NETWORK CONNECTIONS
When operating over the Connection-Oriented Network Service CONS,
the maximum number of network connections which can be in use
concurrently by DNA OSI Transport. This characteristic can be
increased only when the transport entity is enabled.
MAXIMUM RECEIVE BUFFERS
Maximum number of receive buffers that can store received DT transport
PDUs. You can modify this characteristic only when the entity is
disabled. Also, you can only increase the characteristic value.
MAXIMUM REMOTE NSAPS
Maximum number of remote NSAPs that can exist concurrently. This value
must be greater than the current value of maximum transport
connections. You can modify this characteristic to a lower value only
when the entity is disabled. This characteristic can be increased when
enabled.
MAXIMUM TRANSPORT CONNECTIONS
Maximum number of active transport connections allowed at one time.
Must be less than the current value of maximum remote nsaps. You can
modify this characteristic to a lower value only when the entity is
disabled.
MAXIMUM WINDOW
Default: 8 Value: 1-65535
Maximum credit window that can be granted on a transport connection.
This is used for control of the number of data segments PDUs allowed
to be transmitted over a particular transport connection before at
least one acknowledgment must be returned from the destination system.
If the number of PDUs already transmitted equals the maximum window
and no corresponding acknowledgments have been received, transport
stops sending PDUs over the transport connection and waits for an
acknowledgment message. You can modify this characteristic to a lower
value only when the entity is disabled.
NSAP SELECTOR
Default: 33 Value: 0-255
The NSAP selector to use for the Connection-Oriented Transport Service
COTS when running over CLNS. If 0 or 1, COTS over CLNS is not enabled.
This attribute cannot be set to 32, which is the value of the NSP NSAP
selector. Or, on DEC OSF/1, to the current setting of the osi transport
attribute cltp nsap selector if it is other than 0 or 1.
This attribute cannot be modified when transport is enabled.
SUPPORT MAP
Default: None Value; False
Specifies whether the implementation supports the MAP manufacturing
automation protocol entity. You cannot modify this characteristic.
VERSION
Version number of the DNA OSI Transport architecture specification to
which the implementation conforms. You cannot modify this
characteristic.
2 – status
CURRENTLY ACTIVE CONNECTIONS
Number of active transport connections.
STATE
Status of the osi transport entity.
ON - The OSI transport entity is enabled.
OFF - The OSI transport entity is disabled.
3 – app
An OSI Transport Application entity stores information about an end user that is activated for receipt of an incoming connection request when the request contains that end user's name in its Destination Name field.
3.1 – character
CALLED TSELS
Default: No tsap Value: Hex-string
Transport Service Access Point TSAP for which the image specified by
the image name characteristic accepts connections. This
characteristic, which is similar to the addresses characteristic, is
used by applications that do not use the DNA session control protocol
for example, VOTS applications.
FILE NAME
Default: No File Name Value: Filename
File name of the program to be invoked upon receipt of a connect
request containing a TSEL matching the <quote>Called TSELS attribute
of the application entity.
USERNAME
Default: No user Name Value: Username
User name portion of the access control information that identifies the
account under which the application is to run. If invalid information
or no user name is specified, system defaults are used to select the
user.
4 – local_nsap
An OSI Transport Local NSAP entity is automatically created for each NSAP
address used by the OSI transport entity. Local NSAPs are used primarily
to group together remote NSAPs see the OSI transport local NSAP remote
NSAP entity.
DELETED REMOTE NSAPS
Number of times a remote NSAP has been deleted in order to reclaim the
resources.
NETWORK SERVICE
Type of network service being used.
NSAP ADDRESS
NSAP address corresponding to entity.
5 – local_rmt
An OSI transport local nsap remote nsap entity maintains the transport counters and generates events resulting from interactions between its superior local NSAP and a remote transport service.
5.1 – counters
CONNECTS RECEIVED
Total number of CR TPDUs, regardless of their disposition, that the
local NSAP has received from the remote NSAP.
CONNECTS SENT
Total number of CR TPDUs sent by the local NSAP to the remote NSAP,
including retransmissions.
DUPLICATE PDUS RECEIVED
Total number of all types of detected duplicate TPDUs received from the
remote NSAP.
FAILED CHECKSUMS
Number of checksum failure events detected.
LOCAL PROTOCOL ERRORS
Number of reported local protocol error events. This event is generated
whenever an ER error TPDU is received from the remote NSAP.
PDUS RECEIVED
Total number of all types of TPDUs received from the remote NSAP
excluding detected duplicates.
PDUS SENT
Total number of all types of TPDUs sent to the remote NSAP excluding
retransmissions.
REJECTS RECEIVED
Number of detected reject received events.
REJECTS SENT
Number of detected reject sent events.
REMOTE PROTOCOL ERRORS
Number of reported invalid tpdu received events. This event is
generated whenever the remote NSAP violates the Transport Protocol.
RETRANSMITTED PDUS
Total number of all types of retransmitted TPDUs sent to the remote
NSAP.
TOTAL OCTETS RECEIVED
Total number of octets of all types of TPDUs received from the remote
NSAP, regardless of their disposition. This count includes detected
duplicates.
TOTAL OCTETS SENT
Total number of octets of all types of TPDUs sent to the remote NSAP,
including retransmissions.
USER OCTETS RECEIVED
Total number of user data octets received from the remote NSAP,
including normal, expedited, connect, accept, and disconnect data. This
count does not include duplicates such as data retransmitted by the
remote NSAP.
USER OCTETS SENT
Total number of user data octets sent to the remote NSAP, including
normal, expedited, connect, accept, and disconnect data. This count
does not include data retransmitted by the local NSAP.
USER PDUS DISCARDED
Number of PDUs received from the remote NSAP that were discarded
because of insufficient buffer space.
USER PDUS RECEIVED
Total number of TPDUs containing user data received from the remote
NSAP, including normal, expedited, connect, accept, and disconnect
data. This count does not include duplicates such as TPDUs
retransmitted by the remote NSAP.
USER PDUS SENT
Total number of TPDUs containing user data sent to the remote NSAP,
including normal, expedited, connect, accept, and disconnect data. This
count does not include retransmitted TPDUs.
6 – port
An OSI transport port entity represents one end of a transport connection and maintains status information about that connection. Although the connectionless transport protocol does not create transport connections, ports are still used to maintain status information.
6.1 – Counters
DUPLICATE PDUS RECEIVED
Total number of all types of detected duplicate TPDUs received from the
remote NSAP. This attribute applies only to COTS.
FAILED CHECKSUM
Number of checksum failure events detected.
PDUS RECEIVED
Total number of all types of TPDUs received from the remote NSAP
excluding detected duplicates.
PDUS SENT
Total number of all types of TPDUs sent to the remote NSAP excluding
retransmissions.
RETRANSMITTED PDUS
Total number of all types of retransmitted TPDUs sent to the remote
NSAP.
TOTAL OCTETS RECEIVED
Total number of octets of all types of TPDUs received from the remote
NSAP, regardless of their disposition. This count includes detected
duplicates.
TOTAL OCTETS SENT
Total number of octets of all types of TPDUs sent to the remote NSAP,
including retransmissions.
USER OCTETS RECEIVED
Total number of user data octets received from the remote NSAP,
including normal, expedited, connect, accept, and disconnect data. This
count does not include duplicates such as data retransmitted by the
remote NSAP.
USER OCTETS SENT
Total number of user data octets sent to the remote NSAP, including
normal, expedited, connect, accept, and disconnect data. This count
does not include data retransmitted by the local NSAP.
USER PDUS RECEIVED
Total number of PDUs containing user data received from the remote
NSAP, including normal, expedited, connect, accept, and disconnect
data. This count does not include duplicates such as TPDUs
retransmitted by the remote NSAP.
USER PDUS SENT
Total number of TPDUs containing user data sent to the remote NSAP,
including normal, expedited, connect, accept, and disconnect data. This
count does not include retransmitted TPDUs.
6.2 – status
ACKNOWLEDGMENT DELAY TIME
Maximum amount of time, in seconds, that an AK TPDU is to be withheld.
This attribute applies to protocol class 4 only.
CHECKSUMS
Indicates whether checksums are in use on the transport connection.
This attribute is supported only for class 4 protocol.
CLIENT
Name designated by the port user when the port was opened. If DNA
session control is being used, this is the name of the session control
port being used.
CONS TEMPLATE
When operating over the CONS, the name of the X.25 Access module's
template specified when establishing the underlying network connection.
CR TIMEOUT
Amount of time, in seconds, to wait for a response to a CR TPDU before
assuming that the remote transport service provider will not respond.
This attribute is valid for protocol classes 0 and 2 only.
DIRECTION
Indicates whether the port is open to initiate an outgoing connection,
to receive an incoming connection, or is listening for incoming
connection requests.
INCOMING - Transport connection initiated by remote transport service.
LISTENING - Listening for incoming connection requests.
OUTGOING - Transport connection initiated by this transport service.
UNKNOWN - Port direction is not known.
ER TIMEOUT
Amount of time, in seconds, to wait for a response to an ER TPDU
before disconnecting the network connection. This attribute is valid
for protocol classes 0 and 2 only.
EXPEDITED DATA
Indicates whether the expedited data option is in use for the transport
connection. This attribute is supported only for class 2 and class 4
protocols.
EXTENDED FORMAT
Indicates whether the use of extended formats should be negotiated for
a transport connection which operates the class 2 or 4 protocol.
INACTIVITY TIME
Time, in seconds, being used for the inactivity timer. This value is
the product of multiplying the keepalive time by the inactivity
factor architectural constant = 4. This attribute is valid for
protocol class 4 only.
INITIAL RETRANSMIT TIME
Time, in seconds, used for the retransmission timer when sending the
first TPDU on the transport connection. The value of this attribute
is derived from the template used when the port was initialized. This
attribute applies to COTS only.
KEEPALIVE TIME
Time, in seconds, being used for the window timer. The value of this
attribute is derived from the template used when the port was
initialized. This attribute is valid for protocol class 4 only.
LOCAL NSAP
Local NSAP address being used for the transport connection.
LOCAL REFERENCE
Unique reference number assigned to the transport connection by the
local transport service provider. This attribute applies to COTS only.
LOCAL TRANSPORT SELECTOR
Local transport selector for this port.
MAXIMUM NSDU SIZE
When operating over the CONS, the maximum NSDU size for transmitting
and receiving buffers. Expressed as a number of octets. This attribute
is valid for CONS only.
NEGOTIATED TPDU SIZE
The TPDU size which was negotiated for this transport connection. This
attribute applies to COTS only.
NETWORK PORT
Name of the network service port being used.
NETWORK SERVICE
Type of network service over which the transport connection is
operating. Attribute value derived from the template used when the
port was initialized.
PROTOCOL CLASS
Protocol class operating on the transport connection. This attribute
is not valid for CLTS.
REMOTE IDENTIFIER
Implementation identity and version of the remote NSAP. When present,
this value is received in the identification of implementation
parameter of the CR or CC TPDU. This attribute applies to COTS only.
REMOTE NSAP
Remote NSAP address being used for the transport connection. This
attribute applies to COTS only.
REMOTE REFERENCE
Reference number assigned to the transport connection by the remote
transport service provider. The value will be 0 if the transport
connection is operating the class 0 protocol. This attribute applies
to COTS only.
REMOTE TRANSPORT SELECTOR
Remote transport selector that identifies the remote transport service
user. This attribute applies to COTS only.
REQUEST ACKNOWLEDGMENT
Indicates whether request acknowledgment was negotiated for this
transport connection. This attribute is valid for class 4 protocol only.
RETRANSMIT THRESHOLD
Number of times a TPDU requiring acknowledgment is to be retransmitted
without acknowledgment before the transmission completes with an
error. This attribute is valid for class 4 protocol only.
ROUND-TRIP DELAY ESTIMATE
Current estimate, in milliseconds, of the round-trip delay on the
transport connection. This attribute is valid for protocol class 4
only.
SEND IMPLEMENTATION ID
Indicates whether the implementation id will be sent in the CR. It is
always returned in the CC if it is present in the CR.
SEND PREFERRED MAXIMUM tpdu SIZE
Indicates whether the preferred maximum TPDU size parameter was sent
in the CR or CC TPDU.
SEND REQUEST ACKNOWLEDGMENT
Indicates whether the request acknowledgment parameter was sent in the
CR or CC TPDU.
TYPE
Indicates that the port is being used for the connection-oriented CO
Transport protocol.
CL - Connectionless transport service.
CO - Connection-Oriented transport service.
USE CLNS ERROR REPORTS
When operating over CLNS, indicates whether the network Routing layer's
error reporting facility should be used when performing connection
establishment. This attribute applies to COTS only.
7 – template
An OSI transport template entity provides a collection of characteristics that supply default values for certain parameters that influence the operation of a port on a transport connection. One template, with the reserved identifier default, is automatically created when the osi transport entity is created. This template is used by default when a user does not specify a template identifier in a call to establish a connection. The default template is automatically deleted when the osi transport entity is deleted. Similarly, the initial values of the attributes in a template are the same as the current values in the default template.
7.1 – character
ACKNOWLEDGMENT DELAY TIME
Default: 1 Value: 0-65
Maximum amount of time, in seconds, that an AK TPDU is to be withheld.
This attribute is valid for protocol class 4 only.
CHECKSUMS
Default: False Value: Boolean
Specifies whether the use of checksums should be negotiated for a
transport connection. This attribute is valid for protocol class 4
only.
CONS TEMPLATE
Default: OSI Transport Value: Simple-name
Name of the X.25 Access module template to be used when establishing a
network connection over the CONS. Used only when the value of the
network service attribute is cons.
CR TIMEOUT
Default: 30 Value: 1 - ( 2 to the 23rd)
During connection establishment, the amount of time, in seconds, to
wait for a response to a CR TPDU before assuming that the remote
transport service provider will not respond. This attribute is valid
for protocol classes 0 and 2 only.
ER TIMEOUT
Default: 30 Value: 1 - ( 2 to the 23rd)
The amount of time, in seconds, to wait for a response to an ER TPDU
before disconnecting the network connection. This attribute is used
for protocol classes 0 and 2 only.
EXPEDITED DATA
Default: True Value: Boolean
Specifies whether use of the expedited data option should be negotiated
for the transport connections. This attribute is not valid for
protocol class 0.
EXTENDED FORMAT
Default: None Value: Boolean
Specifies whether the use of extended TPDU format should be negotiated
for the transport connections. Normal format gives 7-bit sequence
numbers and 4-bit credit fields; extended format gives 31-bit sequence
numbers and 16-bit credit fields. This attribute is supported only for
class 2 and class 4 protocols.
INBOUND
Default: True Value: Boolean
Indicates whether this template may be used as the template for an
inbound transport connection. The algorithm of selection of the inbound
template is different depending on the type of network service over
which the transport connection is made. If an inbound template cannot
be found for an inbound transport connection, then the template called
default will be selected as the default. For the CLNS network
service, the inbound template selected is the first template found that
has the Inbound attribute set to true, the Network Service attribute
set to CLNS, and the CLNS Inactive Area Address attribute set to empty
set.
For the CLNS network service using the inactive subset, that is, null
internet, the incoming template selected is the first template found
that has the Inbound attribute set to True, the Network Service
attribute set to CLNS and the CLNS Inactive Area Address attribute
matches the Inactive Area Address attribute of the Routing Circuit
entity that the transport connection is using. For the CONS network
service, the inbound template selected is the first template found that
has the inbound attribute set to true, the network service attribute
set to CONS and the CONS template attribute that is, an X.25 Access
template name matches the name of the X.25 Access filter that was used
to accept the inbound network connection.
INITIAL RETRANSMIT TIME
Default: 5 Value: 1 - ( 2 to the 23rd )
Amount of time, in seconds, to wait for an acknowledgment before
retransmitting the first TPDU over the transport connection.
KEEPALIVE TIME
Default: 60 Value: 1 - 6383
Time, in seconds, to be used for the window timer. When the transport
service provider has no TPDUs to send over a transport connection, it
retransmits the last AK TPDU at the specified frequency to prevent
expiration of the remote NSAP's inactivity timer. This attribute is
valid for protocol class 4 only.
LOCAL NSAP
Default: system dependent Value: NSAP address
A local NSAP address to be used by default if one is not supplied
across the service interface.
MAXIMUM NSDU SIZE
Default: 2048 Value: 2048
When operating over the CONS, the maximum NSDU size to use for transmit
and receive buffers. Expressed as a number of octets.
NETWORK SERVICE
Default: CLNS Value: any, CLNS, or CONS
Type of network service. The network service chosen must be compatible
with the value of the protocol class attribute.
ANY - Either.
CLNS - Connectionless Network Service.
CONS - Connection-Oriented Network Service.
RETRANSMIT THRESHOLD
Default: 8 Value: 0 - ( 2 to the 23rd )
Number of times a TPDU requiring acknowledgment is to be retransmitted
before it is assumed that network connectivity has failed. This
attribute is valid for protocol class 4 only.
SECURITY
Default: Null Value Value: Octet String
An octet string to be transmitted in the security parameter of a CR or
CC TPDU. A null value causes the security parameter to be omitted from
the TPDU. For security reasons, this attribute cannot be displayed.
SEND IMPLEMENTATION ID
Default: True Value: Boolean
Indicates whether the implementation id should be sent in the CR if the
proposed protocol class is 2 or 4. It is always returned in the CC if
it is present in the CR.
SEND PREFERRED MAXIMUM TPDU SIZE
Default: True Value: Boolean
Indicates whether the preferred maximum TPDU size parameter should
be sent in the CR TPDU.
If the preferred maximum TPDU size parameter was present in the CR
TPDU, then it indicates whether the preferred maximum TPDU size
parameter should be sent in the CC TPDU.
The default value of this characteristic should not be changed unless
the remote implementation does not conform to ISO 8073.
SEND REQUEST ACKNOWLEDGMENT
Default: True Value: Boolean
Indicates whether the request acknowledgment parameter should be sent
in the CR TPDU.
If the request acknowledgment parameter was present in the CR TPDU, then
it indicates whether the request acknowledgment parameter should be
sent in the CC TPDU.
The default of this characteristic should not be changed unless the
remote implementation does not conform to ISO 8073.
USE CLNS ERROR REPORTS
Default: False Value: Boolean
Indicates whether the network Routing layer's error report facility
should be used when performing connection establishment. If set to
true, this may result in faster detection of an unreachable node at
the time of connection establishment. This characteristic should not
be set to true on an end system that is either dual-railed or
connected to a network that has a high probability of duplication.
This is valid only if network service equals CLNS.