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6.3. DODAG Information Object (DIO)

The DODAG Information Object carries information that allows a node to discover a RPL Instance, learn its configuration parameters, select a DODAG parent set, and maintain the DODAG.

6.3.1. Format of the DIO 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 |Version Number |             Rank              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|G|0| MOP | Prf |     DTSN      |     Flags     |   Reserved    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                                                               |
+                            DODAGID                            +
|                                                               |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Option(s)...
+-+-+-+-+-+-+-+-+

               Figure 14: The DIO Base Object

  • Grounded (G): The Grounded 'G' flag indicates whether the DODAG advertised can satisfy the application-defined goal. If the flag is set, the DODAG is grounded. If the flag is cleared, the DODAG is floating.

  • Mode of Operation (MOP): The Mode of Operation (MOP) field identifies the mode of operation of the RPL Instance as administratively provisioned at and distributed by the DODAG root. All nodes who join the DODAG must be able to honor the MOP in order to fully participate as a router, or else they must only join as a leaf. MOP is encoded as in the figure below:

MOPDescription
0No Downward routes maintained by RPL
1Non-Storing Mode of Operation
2Storing Mode of Operation with no multicast support
3Storing Mode of Operation with multicast support
All other values are unassigned

A value of 0 indicates that destination advertisement messages are disabled and the DODAG maintains only Upward routes.

Figure 15: Mode of Operation (MOP) Encoding

  • DODAGPreference (Prf): A 3-bit unsigned integer that defines how preferable the root of this DODAG is compared to other DODAG roots within the instance. DAGPreference ranges from 0x00 (least preferred) to 0x07 (most preferred). The default is 0 (least preferred). Section 8.2 describes how DAGPreference affects DIO processing.

  • Version Number: 8-bit unsigned integer set by the DODAG root to the DODAGVersionNumber. Section 8.2 describes the rules for DODAGVersionNumbers and how they affect DIO processing.

  • Rank: 16-bit unsigned integer indicating the DODAG Rank of the node sending the DIO message. Section 8.2 describes how Rank is set and how it affects DIO processing.

  • RPLInstanceID: 8-bit field set by the DODAG root that indicates of which RPL Instance the DODAG is a part.

  • Destination Advertisement Trigger Sequence Number (DTSN): 8-bit unsigned integer set by the node issuing the DIO message. The Destination Advertisement Trigger Sequence Number (DTSN) flag is used as part of the procedure to maintain Downward routes. The details of this process are described in Section 9.

  • Flags: 8-bit unused field 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.

  • DODAGID: 128-bit IPv6 address set by a DODAG root that uniquely identifies a DODAG. The DODAGID MUST be a routable IPv6 address belonging to the DODAG root.

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

6.3.2. Secure DIO​

A Secure DIO message follows the format in Figure 7, where the base format is the DIO message shown in Figure 14.

6.3.3. DIO Options​

The DIO message MAY carry valid options.

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

  • 0x00 Pad1
  • 0x01 PadN
  • 0x02 DAG Metric Container
  • 0x03 Routing Information
  • 0x04 DODAG Configuration
  • 0x08 Prefix Information
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