2.2.3 Association Start Request Message

An Association Start Request Message is used to request the establishment of an association. The following diagram shows the Association Start Request Message including the Common Replication Message Header.

0	1	2	3	4	5	6	7	8	9	1 0	1	2	3	4	5	6	7	8	9	2 0	1	2	3	4	5	6	7	8	9	3 0	1
Common Replication Message Header (16 bytes)
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Sender Association Handle
NBNS Major Version																NBNS Minor Version
Reserved (21 bytes)
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Common Replication Message Header (16 bytes):  The Common Replication Message Header, as specified in section 2.2.2. The Packet Length field MUST be 41. Because this is the first message, the sender does not know the association handle value on the receiving machine. The Destination Association Handle field MUST be set to 0 and ignored upon receipt. The Message Type field MUST be set to 0.

Sender Association Handle (4 bytes):  An unsigned 32-bit integer that uniquely identifies this association on the machine that sends this Association Start Request Message.

NBNS Major Version (2 bytes): An unsigned 16-bit integer. It is the major version of NBNS on the sender machine. It MUST be set to 2. If the major version is not set to 2, then the packet MUST be silently discarded.

NBNS Minor Version (2 bytes): An unsigned 16-bit integer. It is the minor version of NBNS on the sender machine. Currently defined values are 1 and 5. Other values MUST NOT be sent. If other values are received then they MUST be treated as if the closest lower valid version has been received.<4>

Reserved (21 bytes): 21 bytes to pad the packet length to 41 bytes. It MUST be ignored upon receipt.