[Ietf-not43] address issues

[hardie at qualcomm.com]

At 11:05 AM -0500 08/22/2003, Eric A. Hall wrote:
>
>Netblocks are always the smallest unit of data; an adress range can never
>be smaller than a netblock. Furthermore, netblocks are often the largest
>unit of data (but not always). EG, address ranges can have gaps, meaning
>that they cannot always be used to represent contiguous address space.

This is  a critical point from my experience.  I worked on a proposal
with a couple of other folks a while back to limit how longest-match processing
applied to "covered" addresses*, and it turns out one of the hardest things to
deal with is the reality that some of those longer prefixes were not 
deliverable
*at all* by the entities advertising the covered address.  That is, someone
advertising a /16 may have alienated a /24 within it so completely that
they do not deliver traffic to that /24; the successful delivery of traffic
*depends* on the existence of the longer prefix being in the routing table.
I think that we need to be very careful in structuring this data model
so that we can deal with that reality.  I also suspect that,
that, despite the temptation alluded to here:

(Eric again)
>Netblocks have embedded hierarchical information which is sufficiently
>usable as key values for distributed lookups.

we need to be very careful to separate the identifiers used for distributed
lookups from the data itself.  That will give us added flexibility to handle
the different types of relationships which may pertain between objects
over times.
			regards,
				Ted Hardie



*draft-grow-bounded-longest-match-00.txt is a descendent of that work,
but Russ White has been the key to the work for so long I am not even sure
why my name is still on it.