[DNA] MUST Store Lifetime and Last Refresh time?(draft-pentland-dna-protocol-00.txt)

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

In the draft it states:

   "The list will be
    referred to in this document as "DNAPrefixList".  For each prefix the
    router MUST store the following information:

    1.  Prefix

    2.  Prefix length

    3.  Valid lifetime

    4.  Time last refreshed"

In my (existing) implementation I'm storing the expiry time
of the prefix (which is calculated based on the valid lifetime
at the RA reception time).

Is this insufficient?

I can understand having an indication of when data expires,
but it seems overkill explicitly pointing out which data types
have to be internally stored in the host unless there's
further reasons behind it.

Would it be possible to make this descriptive and informational
(being internal to the host) rather than prescriptive,
using standards language?

Greg