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Re: Verio Peering Question
From: "E.B. Dreger" <eddy+public+spam () noc everquick net>
Date: Sat, 29 Sep 2001 20:26:06 +0000 (GMT)


Date: Sat, 29 Sep 2001 21:09:49 +0100 (BST)
From: Stephen J. Wilcox <steve () opaltelecom co uk>

[1] Providers SHOULD filter/aggregate downstream routes, unless

Two different subjects? Filter definitely, you want to ensure
quality and sanity. But aggregate... hmm, dont think that'll
work with commerical people. A customer multihomes and you
aggregate whilst a.n.other doesnt.. a.n.other gets all the
traffic and you become the secondary provider and let a.n.other
get all the new business as primary!

Punch holes in aggs for multihoming, same as now.  Maybe I should
clarify... I was referring to splitting netblocks for the purpose
of tuning traffic.

[2] Want to tune inbound traffic?  Fine... advertise those longer
    prefixes to your upstreams/peers.  But don't make the rest of
    the Internet suffer.  Communities good.  Extra routes bad.

but people dont advertise long prefixes in order to simply make
use of two providers for the sake of it, they do it in order to

IGP-into-BGP causes this, and is hardly for preferring traffic
from one upstream.

create their own unique routing policies which by definition
needs to be internet-wide

Tag a single netblock with a community or MED.  Don't split it
into two longer prefixes.  Of course, that might require inter-AS
cooperation.

i would envisage all kinds of problems too where the aggregating
upstream accepts your specific routes via another isp by
mistake and then your transit traffic ends up going all round
the place.. you'd be advertising /24s to peers and all but one
transit, with primary transit aggregating up to /16 or
whatever, feels bad..

Hmmmm.  So I have customer X, who also connects to backbone B.
They advert several blocks, which I agg to 192.168.0.0/19.  B
does not agg the blocks... but I'd also agg what I hear from
B, into the same /19.  No problem here.

Or perhaps a hack... match ^[0-9]*_ and prefer it over longer
prefixes.  i.e., if you can get there directly, it's better than
going through another AS.

Your point definitely merits thought... but I'm not sure that
it's insurmountable.


Eddy

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Date: Mon, 21 May 2001 11:23:58 +0000 (GMT)
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