PAM Programming Manual

Link-Level Interfaces
PAM Programming Manual—142482
3-28
Getting an SDU (Token Ring)
SSAP
The source service access point (SSAP) address:
LLC-Ctrl
LLC control field.
SDU-data
User data.
For detailed information on these fields, refer to the IEEE 802.5 protocol specifications.
Getting an SDU (Token Ring)
This primitive is used to find and interpret the first (or next) SDU in an inbound
aggregate SDU buffer. It passes back to the application the type of PDU that it
represents, the address of the peer that issued the PDU, and an indication of the location
and size of the associated user data, if any.
The syntax for this primitive is
The parameters for this primitive are defined as follows:
AggrSDU^Buff^ptr (STRING .EXT)
Required input used to reference the buffer that contains the inbound aggregate
SDU.
mac^frame^offset (INT .EXT)
Optional output used to indicate where the mac^frame of the SDU can be found.
It is in the form of an offset, in bytes, from the beginning of AggrSDU^Buff.
snax^id (INT(32) .EXT)
Optional output used to return the mux^id from the SDU. This is only valid for
LLC2 type aggregates.
User^Data^Offset^B (INT .EXT)
Optional output that returns the offset, in bytes, from the beginning of the inbound
aggregate SDU buffer to the location where the user data, if any, begins. If there is
no user data associated with the SDU, a value of zero is returned.
INT PROC ZL2TR^Get^SDU^
( AggrSDU^Buff^ptr
,mac^frame^offset
,snax^id
,User^Data^Offset^B
,User^Data^Size^B ) EXTENSIBLE;