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NAME : HCPMKPDU
DESCRIPTION: LinkAG Marker Protocol-Data-Unit (PDU)
Control Block
DSECT : MKPDU
FUNCTION : This control block maps the IEEE 802.3ad-2000
version 1 Marker PDU and Marker Response
PDU structure.
The Marker protocol allows LinkAG Logic to
request the transmission of a Marker PDU on a
given port. The Marker PDU is received by the
connected switch and a Marker Response PDU is
returned on the same port back to our LinkAG
logic. When our LinkAG logic requests
transmission of a Marker PDU on a given port
and does not transmit any further MAC Client
PDUs that relate to a given set of
conversations until the corresponding Marker
Response PDU is received from that link, then
it can be certain that there are no MAC Client
PDUs related to those conversations still to
be received by the connected switch. The use
of the Marker protocol can therefore allow our
LinkAG logic a means of determining the point
at which a given set of conversations can
safely be reallocated from one port to another
without the danger of causing frames in those
conversations to be misordered.
Destination Address (DA):
The DA in all Marker and Marker Response PDUs is the
Slow_Protocols_Multicast address (01-80-C2-00-00-02).
Source Address (SA):
The SA in Marker and Marker Response PDUs is the
individual MAC address associated with the port from
which the PDU is transmitted.
Length/Type:
Marker and Marker Response PDUs are always Type
encoded, and carry the Slow Protocol type field. The
encoding of this type field is 0x8809.
Subtype:
The Subtype field identifies the specific Slow
Protocol being encapsulated. Both Marker and Marker
Response PDUs carry the Marker_subtype value 0x02
Version number:
This identifies the Marker protocol version;
implementations conformant to IEEE 802.3ad of the
standard carry the value 0x01.
TLV_type:
This indicates the nature of the information carried
in this TLV-tuple. Marker Information is encoded as
the integer value 0x01; Marker Response Information is
encoded as the integer value 0x02.
Marker_Information_Length:
This field indicates the length (in octets) of this
TLV-tuple. Both Marker and Marker Response
information use a length value of 16 (0x10).
Requester_Port:
The port number assigned to the port by the Requester
(the System sending the initial Marker PDU), encoded
as an unsigned integer.
Requester_System:
The Requester's System ID, encoded as a MAC address.
Requester_Transaction_ID:
The transaction ID allocated to this request by the
requester, encoded as an integer.
Pad:
This field is used to align TLV-tuples on 16-byte
memory boundaries. It is transmitted as zeroes in
Marker PDUs; in Marker Response PDUs, this field may
be transmitted as zeroes, or with the contents of this
field from the Marker PDU triggering the response.
The field is ignored on receipt in all cases.
TLV_type:
This field indicates the nature of the information
carried in this TLV-tuple. Terminator (end of
message) information carries the integer value 0x00.
Terminator_Length:
This field indicates the length (in octets) of this
TLV-tuple. Terminator information uses a length value
of 0 (0x00).
Reserved:
These 90 octets are reserved for use in future
extensions to the protocol. It is transmitted as
zeroes in Marker PDUs; in Marker Response PDUs, this
field may be either transmitted as zeroes, or with the
contents of this field from the Marker PDU triggering
the response. The field is ignored on receipt in all
cases.
FCS:
This field is the Frame Check Sequence, typically
generated by the underlying MAC.
VM will create the packet without the FCS, as it
will be added/removed by OSA.
CREATED BY - The LinkAG logic (HCPSWA), when generating
or responding to a Marker PDU. The DSECT
is used to map data sent or received on
a QDIO input or output queue.
DELETED BY - The LinkAG logic (HCPSWA) or VSWITCH real
OSA Port output queue handler.
RELOCATION CONSIDERATIONS - None
ANCHORED - None
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