2.2.2 Common Replication Message Header

All the NBNS replication messages in the following sections have the same Common Replication Message Header as shown in the diagram below.

Packet Length (4 bytes):  An unsigned 32-bit integer denoting the length in bytes of the Common Replication Message Header and the message body but not including the Packet Length field itself.

Reserved (4 bytes):  An unsigned 32-bit integer. This field is not used and MUST be ignored upon receipt.

Destination Association Handle (4 bytes):  An unsigned 32-bit integer that identifies the association on the receiving machine. This value comes from the Sender Association Handle field of the Association Start Response Message, as specified in section 2.2.4. The only exception is in the Association Start Request Message, as specified in section 2.2.3, where Destination Association Handle is set to 0.

Message Type (4 bytes):  An unsigned 32-bit integer. The Message Type value depends on the specific message type as shown in the table below.

Value	Meaning
0x00000000	Association Start Request Message
0x00000001	Association Start Response Message
0x00000002	Association Stop Request Message
0x00000003	Owner-Version Map Request Message, Owner-Version Map Response Message, Update Notification Message, Name Records Request Message, and Name Records Response Message