t_data_req.7.man

This a separate release of the OpenSS7 X/Open XTI/TLI library, TLI modules (timod, tirdwr) and the I

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.so strxnet.macros
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.TH T_DATA_REQ 7 "2004/05/16 02:35:48" "strxnet-0_9_2-4" "Transport Provider Interface (TPI)"
.SH NAME
.B T_DATA_REQ
\- Data Request
.SH SYNOPSIS
This message consists of one
.B M_PROTO
message block followed by zero or more
.B M_DATA
message blocks where each
.B M_DATA
message block contains zero or
more bytes of data.  The format of the
.B M_PROTO
message block is as follows:
.sp
.nf
\fC\s-1\
struct T_data_req {
    t_scalar_t   PRIM_type;      /* Always T_DATA_REQ */
    t_scalar_t   MORE_flag;
};
\fR\s+1
.fi
.SH DESCRIPTION
This primitive indicates to the transport provider that this message contains
a transport interface data unit.  One or more transport interface data units
form a transport service data unit (TSDU).
.PP
Note that the maximum transport service data unit size allowed by the
transport provider is indicated to the transport user via the
.BR T_INFO_ACK (7)
primitive.
.PP
This primitive has a mechanism which indicates the beginning and end of a
transport service data unit.  However, not all transport providers support the
concept of a transport service data unit.
.SH PARAMETERS
.TP 16
.I PRIM_type
identifies the primitive type.
.TP
.I MORE_flag
when greater than zero, indicates that the next
.B T_DATA_REQ
primitive is also part of this transport service data unit.
.SH RULES
The transport provider must also recognize a message of one or more
.B M_DATA
message blocks without the leading
.B M_PROTO
message block as a
.B T_DATA_REQ
primitive.  This message type will be initiated from the
.BR write (2)
operating system service routine.
.PP
For example, on systems that support the
.BR tirdwr (4)
STREAMS module, if that module
is pushed onto a stream corresponding to a transport provider supporting the
.BR TPI ,
then the
.BR write (2)
operating system service routine may be used to send data on that transport
endpoint.  In this case there are no implied transport service data unit
boundaries.  Data is passed down the stream as a series of
.B M_DATA
messages.
.PP
This primitive does not require any acknowledgments, although it may generate
a fatal error.  This is indicated via a
.B M_ERROR
message type which results in the failure of all operating system service
routines on the stream. 
.SH ERRORS
The allowable errors are as follows:
.TP 16
.RB [ EPROTO ]
This indicates one of the following unrecoverable protocol conditions:
.RS
.IP - 3
The transport service interface was found to be in an incorrect state.  If the
interface is in the
.B TS_IDLE
state when the provider receives the
.B T_DATA_REQ
primitive, then the transport provider should just drop the message without
generating a fatal error.
.IP -
The amount of transport user data associated with the primitive defines a
transport service data unit larger than that allowed by the transport
provider.
.SH MODES
Only connection-mode.
.SH ORIGINATOR
Transport user.
.SH "SEE ALSO"
.\".BR T_DATA_REQ (7),
.BR T_DATA_IND (7),
.BR T_EXDATA_REQ (7),
.BR T_EXDATA_IND (7),
.BR T_OPTDATA_REQ (7),
.BR T_OPTDATA_IND (7).
.SH HISTORY
.PP
The Transport Provider Interface first appeared in SVR 4.
.[
svr4
.]
.SH CONFORMANCE
.PP
This interface conforms to TPI Version 2, Draft 2.
.[
TPI Revision 2.0.0
.]
.XX
.[
magic
.]
.[
advprog
.]
.[
$LIST$
.]
.T2