User guide

40 DC 900-1303C
Freeway Client-Server Interface Control Document
2.3.3 ICP Header Format
The ICP header immediately follows the Freeway header for all packets that are for-
warded to the ICP. The ICP header consists of 16 bytes and must be in network byte
order (big-endian). The use of the ICP’s header is protocol-specific. For detailed
description of each field, refer to programmer’s guide for the appropriate protocol. The
DLI_OPT_ARGS structure is defined in the Freeway Data Link Interface Reference Guide
and is used for specifying packet contents when using the “raw” mode of DLI.
The fields in the ICP header are as follows:
Client ID (2 bytes)
This field is equivalent to the
usICPClientID field in the DLI_OPT_ARGS structure.
This field is used only by the X.25 protocol software that runs on the ICP. Refer to
the X.25 Low-Level Interface for more information.
Server ID (2 bytes)
This field is equivalent to the
usICPServerID field in the DLI_OPT_ARGS structure.
This field is used only by the X.25 protocol software that runs on the ICP.
Length (2 bytes)
This field contains an integer value that is the sum of the length of the Protocol
header and the length of the data that follows the Protocol header.
ICP Header
Client ID 2 bytes
Server ID 2 bytes
Length 2 bytes
Command 2 bytes
Status 2 bytes
Parameter 1 2 bytes
Parameter 2 2 bytes
Parameter 3 2 bytes