Subject: Re: [Roll] [roll] #11: Decision on prefix packing in DAO messages

From: "roll issue tracker" <[email-masked]>
Date: Thu, 17 Jun 2010 11:30:35 -0000

#11: Decision on prefix packing in DAO messages
--------------------------------+-------------------------------------------
 Reporter:  jpv@…               |        Owner:  jpv@…        
     Type:  enhancement         |       Status:  closed       
 Priority:  major               |    Milestone:               
Component:  rpl                 |      Version:               
 Severity:  Active WG Document  |   Resolution:  fixed        
 Keywords:                      |  
--------------------------------+-------------------------------------------
Changes (by jpv@…):

  * status:  new => closed
  * resolution:  => fixed

Comment:

 This used to be the format of the DAO message when this ticket was opened:

  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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |         DAO Sequence          |  InstanceID   |   DAO Rank    |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          DAO Lifetime                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                           Route Tag                           |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | Prefix Length |    RRCount    |                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
        |                   Prefix (Variable Length)                    |
        .                                                               .
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |             Reverse Route Stack (Variable Length)             |
        .                                                               .
        .                                                               .
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 11: The Destination Advertisement Object (DAO)

    DAO Sequence:  Incremented by the node that owns the prefix for each
          new DAO message for that prefix.

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

    DAO Rank:  Set by the node that owns the prefix and first issues the
          DAO message to its rank.

    DAO Lifetime:  32-bit unsigned integer.  The length of time in
          seconds (relative to the time the packet is sent) that the
          prefix is valid for route determination.  A value of all one
          bits (0xFFFFFFFF) represents infinity.  A value of all zero
          bits (0x00000000) indicates a loss of reachability.

    Route Tag:  32-bit unsigned integer.  The Route Tag may be used to
          give a priority to prefixes that should be stored.  This may be
          useful in cases where intermediate nodes are capable of storing
          a limited amount of routing state.  The further specification
          of this field and its use is under investigation.

    Prefix Length:  8-bit unsigned integer.  Number of valid leading bits
          in the IPv6 Prefix.

 Winter, et al.            Expires June 10, 2010                [Page 28]

 Internet-Draft           draft-ietf-roll-rpl-05            December 2009

    RRCount:  8-bit unsigned integer.  This counter is used to count the
          number of entries in the Reverse Route Stack.  A value of `0'
          indicates that no Reverse Route Stack is present.

    Prefix:  Variable-length field containing an IPv6 address or a prefix
          of an IPv6 address.  The Prefix Length field contains the
          number of valid leading bits in the prefix.  The bits in the
          prefix after the prefix length (if any) are reserved and MUST
          be set to zero on transmission and MUST be ignored on receipt.

    Reverse Route Stack:  Variable-length field containing a sequence of
          RRCount (possibly compressed) IPv6 addresses.  A node that adds
          on to the Reverse Route Stack will append to the list and
          increment the RRCount.

 Clearly, the DAO message format has completely changed providing the level
 of flexibility and optimization in terms of required bandwidth that was
 requested by this ticket, which can now be closed.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/roll/trac/ticket/11#comment:2>
roll <http://tools.ietf.org/wg/roll/>