Skip to main content

6.4. Destination Advertisement Object (DAO)

The Destination Advertisement Object (DAO) is used to propagate destination information Upward along the DODAG. In Storing mode, the DAO message is unicast by the child to the selected parent(s). In Non-Storing mode, the DAO message is unicast to the DODAG root. The DAO message may optionally, upon explicit request or error, be acknowledged by its destination with a Destination Advertisement Acknowledgement (DAO-ACK) message back to the sender of the DAO.

6.4.1. Format of the DAO Base Object​

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID |K|D|   Flags   |   Reserved    | DAOSequence   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                            DODAGID*                           +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Option(s)...
+-+-+-+-+-+-+-+-+

The '*' denotes that the DODAGID is not always present, as described below.

Figure 16: The DAO Base Object

  • RPLInstanceID: 8-bit field indicating the topology instance associated with the DODAG, as learned from the DIO.

  • K: The 'K' flag indicates that the recipient is expected to send a DAO-ACK back. (See Section 9.3.)

  • D: The 'D' flag indicates that the DODAGID field is present. This flag MUST be set when a local RPLInstanceID is used.

  • Flags: The 6 bits remaining unused in the Flags field are reserved for flags. The field MUST be initialized to zero by the sender and MUST be ignored by the receiver.

  • Reserved: 8-bit unused field. The field MUST be initialized to zero by the sender and MUST be ignored by the receiver.

  • DAOSequence: Incremented at each unique DAO message from a node and echoed in the DAO-ACK message.

  • DODAGID (optional): 128-bit unsigned integer set by a DODAG root that uniquely identifies a DODAG. This field is only present when the 'D' flag is set. This field is typically only present when a local RPLInstanceID is in use, in order to identify the DODAGID that is associated with the RPLInstanceID. When a global RPLInstanceID is in use, this field need not be present.

  • Unassigned bits of the DAO Base are reserved. They MUST be set to zero on transmission and MUST be ignored on reception.

6.4.2. Secure DAO​

A Secure DAO message follows the format in Figure 7, where the base format is the DAO message shown in Figure 16.

6.4.3. DAO Options​

The DAO message MAY carry valid options.

This specification allows for the DAO message to carry the following options:

  • 0x00 Pad1
  • 0x01 PadN
  • 0x05 RPL Target
  • 0x06 Transit Information
  • 0x09 RPL Target Descriptor

A special case of the DAO message, termed a No-Path, is used in Storing mode to clear Downward routing state that has been provisioned through DAO operation. The No-Path carries a Target option and an associated Transit Information option with a lifetime of 0x00000000 to indicate a loss of reachability to that Target.

Last updated on