PAM Programming Manual

Link-Level Interfaces
PAM Programming Manual—142482
3-8
Formatting an Aggregate SDU and an SDU Header
(Ethernet)
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 L2S Formatting Library primitives. The version
number determines the format of the aggregate SDUs.
zAddr
All traffic through the port is associated with the value specified here. For an
Ethernet port type, this is the Proto^Type field of the DIX-compatible Ethernet
header. For an LLC1 port type, this is the destination link-layer service access point
(DLSAP) address found in inbound frames, and the source link-layer service access
point (SLSAP) address found in outbound frames. The value specified can be up to
2 hexadecimal digits (1 byte) and should always be an even number. The value
%H3E is reserved.
zMAC-Addr
This field contains the group media access control (MAC) address that dictates
which inbound PDUs are delivered to an application associated with a particular
port. This unique 6-byte group MAC address is added to the list of group MAC
addresses the controller listens for at the MAC level. PDUs directed to the adapter’s
individual MAC address are not routed to ports that have this attribute defined. The
value specified can be up to 12 hexadecimal digits (6 bytes).
zSDU-Cnt
This field contains the number of individual SDUs included in this aggregate SDU.
When a newly-arrived SDU causes this value to reach the port’s configured data
forward count (DFC), an inbound aggregate SDU is delivered to the host and a new
inbound aggregate SDU is started.
Formatting an Aggregate SDU and an SDU Header (Ethernet)
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 is dependent on
the Port^Type in use (LLC1 or Ethernet), and the SDU Type being built (UI, XID, or
Test). If additional SDU headers are required, the application uses the aggregate SDU
buffer in subsequent calls to the ZL2S^Frmt^SDU^Hdr^ primitive to format individual
SDU headers.
The LLC1 and Ethernet SDU headers formatted by this L2S primitive is described in the
ZL2S^Frmt^SDU^Hdr^ primitive that follows.