[DNA] Design Team solution 1: Question about DNA Option

[Greg Daley <greg.daley@eng.monash.edu.au>]

from draft-pentland-dna-protocol-00.txt:

Section 4.3:

The learned prefixes in the DNA option are not
8 octet aligned, and include prefix lengths.

Assuming that advertised prefixes are global
addresses, can't the prefixes be:
1) 8 octet aligned and

2) 8 octets (64 bits) long

With no prefix length field.

 From RFC 3513 (S2.5.1):

    For all unicast addresses, except those that start with binary value
    000, Interface IDs are required to be 64 bits long and to be
    constructed in Modified EUI-64 format.

This would lead to 6 octets overhead (which is the minimum additional
cost when you consider the size of prefix lengths).
One of those octets could indicate the known number of prefixes,
and the option length could indicate how many prefixes are advertised
(effectively indicating if the RA is complete or not when the PIOs
are counted).

This would remove the need to get two bits from the RA header in the
case of

Also, if there is a requested landmark prefix, could it not appear
in the DNA option, even if the option is does not provide complete RA?
The minimum NACK for an unknown landmark would then be 8 octets
(no prefixes in the list), on top of the existing RA.

The DNA option could then be used in both solicitor and receiver.

Greg