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

Edward B. DREGER eddy+public+spam at noc.everquick.net
Wed Feb 15 19:30:36 UTC 2006

PJ> Date: Wed, 15 Feb 2006 19:02:11 +0000 (GMT)
PJ> From: Paul Jakma

PJ> > Of course not.  Let SBC and Cox obtain a _joint_ ASN and _joint_ address
PJ> > space.  Each provider announces the aggregate co-op space via the joint
PJ> > ASN as a downstream.
PJ> This is unworkable obviously: Think next about SBC and (say) Verizon

No, it is not unworkable.  Think through it a bit more.  Although the 
problem is theoretically O(N^2), in practice it is closer to O(N).  Note 
that _routing itself_ is theoretically an O(N^2) problem.  Do we say 
that it is "unworkable obviously"?  No.

PJ> customers, then what about those with Cox and Verizon, then SBC/Cox/Verizon.
PJ> etc.

Yes, one ASN is required per cooperating pair.  Just how many pairs do 
you think there are?  Now compare with the number of leaves that [would 
[like to]] dual-home.

If you have 100 providers, each cooperating with every single one of the 
others, that's

	100 * 99 / 2 = 4950

different ASes.  Noticeable, but still a long way from 4-octet ASN 
territory.  And guess what?  Each downstream would need its own ASN 
otherwise; this is just one ASN per cooperating pair.

How many transit ASes are there?  And will each one share a downstream 
with all of the others?


I'll hazard a guess that a transit cooperates with, on average, no more 
than five different other transits.  Ergo, linear scaling.

The biggest problem is when customer's link to provider A goes down and 
inbound traffic must flow through provider B.  This necessitates some 
sort of path between A and B where more-specifics can flow.

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