RE: Regionally aggregatable address space for multihoming

[Geoff Huston <gih@telstra.net>]

> > Only if you revolutionise ISP interconnection strategies and
> > find some way to change the underlying economics.
>Geoff Huston should be stepping up to this one. There is no need to change
>human nature, just provide a reasonable tool for aggregation then charge for
>carrying explicit routes when people insist on them. Match the economics to
>human nature rather than trying to invent a technological restraint system.


Ok - I'll step up to this.  The theory is fine, but the practice is harder 
to identify.

I find it hard to conceive as to what a 'geography' may be when its cheaper 
to cross the Atlantic by submarine cable, station to station, than it is to 
do last mile at either end. We had this model in our collective industry 
heads that "distance = cost" and that local geographies see some cost 
benefit in locally interconnecting. In the current communications 
environments the cost of local regulatory regimes appears to be greater 
than the cost of distance, and a least cost community of common benefit has 
no geographic counterpart.

We are certainly on the horns of some form of dilemma - conventional 
routing wisdom indicates that some form of hierarchy is one of the few 
tools that address route scaleability - through hierarchies fine detail is 
obscured at a distance, and these details only become visible at a local 
level. However, the cost of circuitry is inexorably dropping - customers 
find it cost effective to drag two or more local circuits to two or more 
upstreams as the most cost effective response to resiliency requirements. 
Providers find it cost effective to drag long haul circuits all over the 
place as a means of bypassing various components of a locally-provided 
upstream transit service. At what point in the long haul over-supply market 
will the long haul providers start to look at end customers as a potential 
long-haul customers, and at what point will multi-homing become a non-local 
problem? What appears to be happening is that "geographic" locality and 
"least cost" locality don't match all that closely. (Yes this "long 
distance is cheaper" sounds far fetched, but its also far a far fetched, 
but current, reality which makes a Tokyo - LA circuit cheaper than a Tokyo 
- Osaka circuit.)

So inside all this I see and understand that IF we had a pretty solid 
"distance = cost" dominant cost model then there would be a fair incentive 
for local interconnection - to some extent. If we _also_ had a different 
inter-provider settlement model where every packet was purchased from its 
originating provider and on-sold to its terminating provider (to borrow 
some PSTN settlement terms with a reselling margin equal to the marginal 
cost of transit), then there would be an even stronger case for local 
interconnection, and, furthermore if the packet accounting settlement rates 
were fixed according to some imposed industry model, then the case for 
regionally aggregateable addresses would be pretty solid.

Needless to say, by this stage you are pretty close to the PSTN original 
interprovider settlement model and about 1,000,000 miles away from the 
Internet of today.

There are a number of theoretically stable inter-provider economic models 
that could support an Internet. There are very few models which also allow 
a transition from today's reality to an end point of universal adoption of 
the particular model. I have this depressing view (*) that metro routing 
aggregation is one of these models which could work, but the path from here 
to there is not visible to me at any rate.

(*) depressing to me at any rate, because most of the routing scaling tools 
infer the use of hierarchies, which in turn require a pretty substantial 
shift of current operating practice.

There may be some other approaches: if you concede that a full routing 
table at some point in the future will have some considerable cost in terms 
of specialized support machinery, then the market will sort itself out 
through the use of different route filters applied to peers, customers and 
upstreams. The implied route scaling cost of multi-homing would become as 
explicit cost of protocol scaling, and there would be a solid economic 
incentive to single-home. But, that's a big concession, and one which has 
no basis in what we are seeing today. Today its the protocol which is 
showing signs of scaling stress, not the routing engines, and attempting to 
work out an economic model which applies local pressure for a greater 
common good of protocol stability is a tough ask.


    Geoff