Subject: Closer examination of aggregation.

From: Peter Tattam <[email-masked]>
Date: Sat, 18 Sep 1999 14:15:59 +1000 (EST)

If we go with the assumption that aggregation is essential for managing future
growth (I don't want to argue this point, but rather treat is as an assertion
for the benefit of this discussion),  I wonder if aggregation can be structured
in such a way as to be able to contain the hole punching that might happen in a
less regulated internet.

The way I understand aggregation is that TLAs are either regionally based, or
mega-ISP based.

If the aggregation model of TLA allocation was fine tuned and mapped more
closely the physical topology of the internet, could it not be arranged so that
multihoming would continue to function in a more efficient manner.

I see the real enemy of successful aggregation being cases where a global
organization wants to have address allocation which is independent of the
overall physical topology.

I would propose then that if an ISP wants to operate in multiple regions then
they should use address allocation that is applicable to that region.

Since we would consider that multihoming is likely to grow significantly in the
2nd or 3rd tier ISP, it should be able to be arranged that multihoming be
confined to ISP's within that region.  

Given this case, one strategy would be to ensure that the DFZ need not require
hole punching at all even though ISP further down the tree hole puch to the
heart's desire.  It's just a matter of arranging the addresses to minimize the
hole punching in the DFZ.

This has been expressed in one form or another, but I don't believe the
selection of TLAs and structuring at the top level has been sufficiently well
explored to get the best benefit of the aggregation model.

This may of course be a totally unrealistic view of the polotics of the
internet, & I suspect the egos of some ISPs might be severely offended by the
notion that they can't have a world wide TLA, but operate with a number of
smaller NLAs.

Another possibility would be to treat the internet as two parts.  Those that
want to be multi-homed and those that don't, and maintain two independent DFZs
for the purpose.

Anyway, my main suggestion is that it would be important for us to examine
*very* carefully how the TLA/NLA model should work for future growth.

Peter

--
Peter R. Tattam                            [email-masked]
Managing Director,    Trumpet Software International Pty Ltd
Hobart, Australia,  Ph. +61-3-6245-0220,  Fax +61-3-62450210

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From: Quality Quorum <[email-masked]>
Date: Sat, 18 Sep 1999 09:18:31 -0400 (EDT)

> want to be multi-homed and those that don't, and maintain two independent DFZs

What about enforcing "restricted multihoming" in the following sense:

There ar two primary reasons for multihoming: (a) fault tolerance, 
(b) big organizations with big local nets which maintain multiple
connections to the big net. 

(a)Fault tolerance has following characteristics:

1. During normal operation only one (primary) route is advertized
   (and (supposedly) is aggregated) to DFZ. 
2. Total amount of organizations with necessity to go into DFZ
   for fault tolerance reason is low.
3. Probability of major simultaneous failures is low: if probability of
   single failure is p, then probability of n simultaneous failures
   is pow(p,n), etc..
4. Backup ISP should aggregate routes from other ISPs (in any case
   SLA part should not be visible in DFZ). Note: it does not prevent
   multihoming below SLA: it just establish the rule that ISP have 
   insulate it from DFZ.

So, it seems to me that Internet can easily manage this kind of route
spilling. There is a number of measures which will guarantee problemless
fault tolerance related multihoming for years and years to come:

1. Make customers pay for this service.
2. Make ISPs pay for resources: establish fees per every potential
   non-aggregated route to be spilled.
3. Require DFZ routers to handle 1M 48-bit routes from the start and
   be upgradable to 2M 48-bit routes.

(b)Big organizations will be required to split there networks into 
subnets with each subnet being single-homed wrt DFZ.

So, how this approach will affect various groups of customers ?

1. Most customers are multihomed within big ISPs anyway,
   so corresponding routes have no chance of spillage into DFZ
   and these customers will not be affected by these rules.
2. Customers who really want fault tolerance at the DFZ scale 
   are able to pay for it.
3. Big organizations have to have routers :):):):):) - the only 
   difference is that subnets will have different global prefix -
   and who cares about it - static DNS will handle it perfectly 
   well and local routers will have no problem handling a few
   but loooooong routes. 
4. Multihoming for traffic optimization should be outlawed anyway.

Opinions ?

> Peter

Thanks,

Aleksey