Verio Peering Question

Sat Sep 29 20:26:06 UTC 2001

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