OSI/TS Configuration and Management Manual

Managing a Transport Connection
OSI/TS Configuration and Management Manual—424831-001
6-5
Building the CR-TPDU
Variable Part
The variable part of a CR-TPDU contains some or all of the following information:
User Data (TSDU)
OSI/TS includes the user data string (up to 32 octets) in protocol classes 1, 2, 3, and 4
whenever the user supplies data along with the T-CONNECT service request.
In protocol class 0, CR-TPDUs cannot carry user data. If the application includes user
data, OSI/TS sends the CR-TPDU without the data. No error or warning is returned.
Alternate protocol class If no alternate class is configured, OSI/TS does not send a
value in the CR-TPDU.
Security Is included in the variable part of the CR-TPDU if you
supply it maximum 16 octets. You can specify this send-
security parameter interactively using SCF, or your
application can specify it dynamically in a
SETPARAM 12 call. This parameter is not used in class
0.
TPDU size Specifies maximum size, in octets, for data TPDUs on the
connection. The value must be a power of 2 from 128 to
8192; (2048 is the maximum in class 0). The size is
specified as the exponent; in other words, a TPDU size of
128 would be specified as 7. The maximum that OSI/TS
will send is the lesser of this value and the maximum size
supported by the network I/O process.
OSI/TS supplies a configured value for this parameter in
the variable part of the CR-TPDU. The default is 512
octets. You can change the configured value using SCF.
Note that this parameter is subject to change, based on the
content of the CC-TPDU.
TSELs OSI/TS includes the configured TSELs for the subdevice
through which the connection request is to be issued. If
no TSELs are configured, OSI/TS leaves them out of the
CR-TPDU.
Additional options The additional options specified in the variable part of the
CR-TPDU contain two kinds of information:
Checksum Specifies whether checksums are used in class 4.
Expedited data Specifies whether transport expedited data transfer service
is used. This option is not available in protocol class 0. If
this option is not configured, OSI/TS does not select it in
CR-TPDUs. Expedited data can be turned on and off
using SCF. Note that this parameter is subject to change,
based on the content of the CC-TPDU.