NAME

T_UNITDATA_REQ - Unitdata 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_unitdata_req {
    t_scalar_t   PRIM_type;      /* Always T_UNITDATA_REQ */
    t_scalar_t   DEST_length;
    t_scalar_t   DEST_offset;
    t_scalar_t   OPT_length;
    t_scalar_t   OPT_offset;
};

DESCRIPTION

This primitive requests that the transport provider send the specified datagram to the specified destination.

PARAMETERS

PRIM_type

identifies the primitive type.

DEST_length

is the length of the destination address

DEST_offset

is the offset (from the beginning of the M_PROTO message block) where the destination address begins.

OPT_length

is the length of the requested options associated with the primitive.

OPT_offset

is the offset (from the beginning of the M_PROTO message block) of the requested options associated with the primitive.

The proper alignment of the destination address and options in the M_PROTO message block is not guaranteed. The destination address and options in the M_PROTO message block are, however, aligned the same as they were received from the transport user.

This primitive does not require any acknowledgment. If a non-fatal error occurs, it is the responsibility of the transport provider to report it via the T_UDERROR_IND indication. Fatal errors are indicated via a M_ERROR message type which results in the failure of all operating system service routines on the stream.

ERRORS

The allowable fatal 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.

• The amount of transport user data associated with the primitive defines an transport service data unit larger than that allowed by the transport provider.

MODES

Only connectionless-mode.

ORIGINATOR

Transport user.