Manpage of T_DATA_REQ

T_DATA_REQ

Section: Transport Provider Interface (TPI) (7)
Updated: 2008-10-31
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NAME

T_DATA_REQ - Data Request

SYNOPSIS

This message consists of one M_PROTO message block followed by zero or more M_DATA message blocks where each M_DATA message block contains zero or more bytes of data. The format of the M_PROTO message block is as follows:

struct T_data_req {
    t_scalar_t   PRIM_type;      /* Always T_DATA_REQ */
    t_scalar_t   MORE_flag;
};

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).

Note that the maximum transport service data unit size allowed by the transport provider is indicated to the transport user via the T_INFO_ACK(7) primitive.

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.

PARAMETERS

PRIM_type: identifies the primitive type.
MORE_flag: when greater than zero, indicates that the next T_DATA_REQ primitive is also part of this transport service data unit.

RULES

The transport provider must also recognize a message of one or more M_DATA message blocks without the leading M_PROTO message block as a T_DATA_REQ primitive. This message type will be initiated from the write(2) operating system service routine.

For example, on systems that support the tirdwr(4) STREAMS module, if that module is pushed onto a stream corresponding to a transport provider supporting the TPI, then the 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 M_DATA messages.

This primitive does not require any acknowledgments, although it may generate a fatal error. This is indicated via a M_ERROR message type which results in the failure of all operating system service routines on the stream.

ERRORS

The allowable errors are as follows:

[EPROTO]

This indicates one of the following unrecoverable protocol conditions:

-: The transport service interface was found to be in an incorrect state. If the interface is in the TS_IDLE state when the provider receives the T_DATA_REQ primitive, then the transport provider should just drop the message without generating a fatal error.
-: The amount of transport user data associated with the primitive defines a transport service data unit larger than that allowed by the transport provider.

MODES

Only connection-mode.

ORIGINATOR

Transport user.

HISTORY

The Transport Provider Interface first appeared in SVR 4[1].

CONFORMANCE

This interface conforms to TPI Version 2, Draft 2[2].

REFERENCES

[1]: SVR 4, UNIX® System V Release 4 Programmer's Manual, 1990, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.
[2]: TPI Revision 2.0.0, Open Group CAE Specification: Transport Provider Interface (TPI) Specification, Revision 2.0.0, Draft 2, 1999, (Berkshire, UK), OpenGroup, Open Group Publication. <http://www.opengroup.org/onlinepubs/>
[3]: Magic Garden, The Magic Garden Explained: The Internals of UNIX® System V Release 4 / An Open Systems Design, 1994, (Australia), B. Goodheart, J. Cox, Prentice Hall. [ISBN 0-13-098138-9]
[4]: Advanced Programming in the UNIX®Environment, 15th edition, December 1997, (Reading, Massachusetts), W. R. Stevens, Addison Wesley. [ISBN 0-201-56317-7]

TRADEMARKS

OpenSS7tm: is a trademark of OpenSS7 Corporation.
Linux®: is a registered trademark of Linus Torvalds.
UNIX®: is a registered trademark of The Open Group.
Solaris®: is a registered trademark of Sun Microsystems.

Other trademarks are the property of their respective owners.

IDENTIFICATION

OpenSS7 XTI/TLI Networking: Package strxnet version 0.9.2.12 released 2008-10-31.

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Time: 22:47:20 GMT, May 22, 2013