Installation guide

42 DC 900-1564A

Synchronous Link Control (SLC) Programmer’s Guide

4.3.2 Normal Data

DLI_PROT_SEND_NORM_DATA can be used only when SLC protocol service is configured. It

is not supported when SLC envelope service is conﬁgured. The header formats are

detailed in Section 5.12 on page 74.

DLI_PROT_SEND_NORM_DATA contains an entire SLC low-priority message. The applica-

tion writes this command to the ICP to transmit a message through the WAN interface

to the SLC network. The application reads this response when the ICP reports a low-

priority message received from the WAN interface to the SLC network.

After reading a DLI_PROT_SEND_NORM_DATA response, the application extracts the

iProtModifier field value (the ICP message identifier consisting of the AML value and

AML descriptor), performs any required message protection operations, then using

same

iProtModifier field value writes the DLI_PROT_SAFE_STORE_ACK command to

acknowledge that the message has been stored safely. The ICP examines the

iProtModifier field, and if necessary transmits a link control block with the corre-

sponding acknowledge message label on the specified SLC network connection.

When the application writes a

DLI_PROT_SEND_NORM_DATA command, the ICP uses the

iProtModifier field (AML value) to compute a corresponding message block identifier

for each information block transmitted. The application reads a

DLI_PROT_SAFE_STORE_ACK response when the ICP reports a a corresponding acknowl-

edgment. If the

iICPStatus field value is DLI_ICP_CMD_STATUS_OK, receipt of a

DLI_PROT_SAFE_STORE_ACK response constitutes acknowledgment

that the specified

message has been stored safely at a remote site. If the

iICPStatus field value contains a

negative error code value, receipt of a

DLI_PROT_SAFE_STORE_ACK response constitutes a

failure in message transmission or a rejection of the speciﬁed message by the remote

site.

2. In the case of messages sent with no protection indicated, DLI_PROT_SAFE_STORE_ACK reports trans-

mission success or failure.