PAM Programming Manual

Link-Level Interfaces
PAM Programming Manual—142482
3-23
Formatting an Aggregate SDU and an SDU Header
(Token Ring)
Aggregate SDU Header Format
The aggregate SDU header formatted by this L2TR primitive is defined as follows:
The fields of the aggregate SDU header are defined as follows:
zWork
This field is reserved for internal use.
zVsn
This field contains the version number of the aggregate SDU header. It is
automatically inserted by the L2TR Formatting Library primitives. The version
number determines the format of the aggregate SDUs. This field is used by the
SNATR interface to indicate it is using 8 byte alignment; however, the formatting
library supports only 2 byte alignment.
zSDU-Type
This field contains the port type and must be ZL2TR-Val-SDUType-LLC1.
zSAP-Value
All traffic through the port is associated with this value. This is the destination link-
layer service access point (DLSAP) address found in inbound frames, and the source
link-layer service point (SLSAP) found in outbound frames. The value can be up to
two hexadecimal digits (1 byte).
zSDU-Cnt
This field contains the number of individual SDUs to be included in this aggregate
SDU. This value should be a minimum of 1. The maximum is 100.
Formatting an Aggregate SDU and an SDU Header (Token Ring)
This primitive is used when an application wants to initialize an aggregate SDU buffer
and format the headers for a complete aggregate SDU message with a single primitive.
This primitive initializes the aggregate SDU buffer, formats an aggregate SDU header,
and formats an initial individual SDU header. The type of SDU header depends on the
Port^Type in use (LLC1), and the SDUType being built (UI, XID, or Test). If additional
SDU headers are required, the application uses the aggregate SDU buffer in subsequent
calls to the ZL2TR^Frmt^SDU^Hdr^ primitive to format individual SDU headers.
def ZL2TR-DDL-Aggr-SDU-Hdr.
02 zWork type ZSPI-DDL-INT.
occurs 2 times.
02 zVsn type ZSPI-DDL-INT.
02 zSDU-Type type ZSPI-DDL-INT.
02 zSAP-Value type ZSPI-DDL-BYTE.
02 zSDU-Cnt type ZSPI-DDL-INT.
end.