Re: NANOG/IEPG/ISOC's current role

[Paul Ferguson <pferguso () cisco com>]

At 10:17 PM 4/3/96 -0500, Curtis Villamizar wrote:

> Provider X takes on some number of customers N that want prefixes and
> think they may later dual home or want to leave the option of changing
> providers without renumbering open.  Substitute for X as you see fit.
>
> If provider X insists that small providers or small to medium business
> customers must renumber to leave a CIDR aggregate the smaller
> organization go off and get "portable" address allocations which put
> them in the unaggregatable toxic waste dump (TWD).  If so, they will
> also try as hard as they can to get a /19.
>
> Some of the small prefixes go out of business.  Some grow and become
> dual homed.  Some switch providers.  Most just don't change.
>
> In either case, TWD allocation or out of a provider aggregate, a dual
> homed customer requires an additional prefix (to get routing right).
>
> If a small prefix changes providers and is TWD allocated, they already
> have a unique route.  If they were allocated from a large provider
> aggregate, one more prefix is needed.  If they were allocated from a
> large provider aggregate and are given a generous grace period, some
> will renumber quickly, some not at all (continuous requests to extend
> the grace period).  Lets assume they are never forced (grace period
> extensions are granted).
>
> If the number of small prefixes that resort to the TWD as a result of
> strong renumbering policies exceeds the number of small prefixes that
> move out of aggregates without eventually renumbering, then there the
> strong renumbering policy actually promotes more growth in the routing
> table size.
>
> In the short term, the difference may not be all that substantial.
> Longer term, if the provider community can cooperate to aggregate
> better then many of the extra routes caused by prefixes changing
> providers can be aggregated back together over a multple AS
> aggregation boundary.
>
> Since you made the comment "And the global routing table grows", do
> you feel what I described above is invalid?  If so, what assumptions
> are you making differently?  Do you feel people will never renumber if
> given a grace period, even if renumbering becomes easier with time?
>
> Curtis

I think that its a fair description.

And honestly, I don't think a substantial percentage of end-networks
will renumber if there are not substantial incentives. If renumbering
becomes less-painful, with time & better tools, perhaps more will
renumber, but again I personally don't foresee a substantial number
doing so without some incentive(s).

The scenario that was previously described by Michael Dillon, I believe,
was one in which a singularly-homed [to provider 'a'] end-network [x]
moved to another provider [provider 'b'] and wanted to take their
provider [a] allocated address(es) with them. This is a case where, if
a larger aggregate is being announced by [a], then a specific component
announced from the [a] CIDR  block would be announced by [b].

Of course, this happens anyway if [x] is dual-homed. I think we can all
agree that the peace-of-mind obtained by [x] in becoming dual-homed is
less than optimal for the Routing Table Watchers (tm).  :-)

This just happens to be a Catch-22 with multihomed end-networks.

- paul