a radical proposal (Re: protocols that don't meet the need...)

Thu Feb 16 05:56:53 UTC 2006

Edward B. DREGER:
> Want to dual-home to SBC and Cox?  Great.  You get IP space from
> 
> 	1.0.0/18
> 
> which is advertised via AS64511.  Lots of leaf dual-homers do 
> the same, yet there is ONE route in the global table for the 
> lot of you.  SBC and Cox interconnect and swap packets when 
> someone's local loop goes *poof*.  
> Flaps within 1.0.0/18 never hit the outside world.
> 
> Everyone is happy.

Except for either SBC or Cox, whichever thinks the other is getting the
short end of the stick for the long-haul transport.

And except for the dual-homers who decide that they like Cox but that they
want to use some mom-and-pop multihomed ISP in their town instead of SBC,
who all of a sudden need to renumber (which they didn't need to do in the PI
model OR if their PA addresses are from Cox) *and* need to try to convince
Cox to set up a shared-address/shared-AS arrangement with the mom-and-pop
ISP, which is NOT going to happen because clearly the benefits are hugely
asymmetric.

I believe, in fact, that due to the perceived (and actual) asymmetries of
the resulting situation, the number of providers who would agree to enter
into such an arrangement with another provider can be counted on zero
fingers. (But that certainly fixes the O(n^2) problem)

And given the choice between having to renumber (A) any time you changed ANY
ONE of your upstreams (this model) and (B) having to renumber only if you
changed the first upstream you got (the existing PA model) and (C) having to
renumber never (the existing PI model), I think customers would choose C,
then maybe B, and almost certainly not A.

So other than the downsides for the ISPs and the customers, this is a great
idea, but it doesn't sell any additional routers.

Matthew Kaufman
matthew at eeph.com