mailing list archives
Re: a radical proposal (Re: protocols that don't meet the need...)
From: "Edward B. DREGER" <eddy+public+spam () noc everquick net>
Date: Wed, 15 Feb 2006 19:30:36 +0000 (GMT)
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.
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
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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