route filtering policies (from "split b" thread)

[Hostmaster, Verant]

Our situation is that we are multihomed to a few providors at each location,
but not necessarily with a backbone-grade link between each physical
location.  We do not resell connectivity, but use it all for our own
Internet application serving.

So it's not really that irresponsible, in that we cannot just take blocks
from our providers.  I know of providers that accept as small as /24s, and I
know of networks that announce /23s and /24s and have no aggregate to fall
back on.  In fact in the case I described, we were able to affect a change,
which was prohibiting many cablemodem customers from accessing not only us,
but the network of a large ISP.

But perhaps you can shed some light on the question asked by another on this
thread - why exactly would you filter on anything shorter than a /24?  RAM
on your routers? CPU?  On my network, I want to pick up as specific routes
(well, up to /24) as the other network wants to announce to me - chances are
I'll get a better connection using a more specific prefix.

Follow up question - where do you come up with /20 as the magic length for
class A's and B's, but /24 for class C's?

Additionally, ARIN is now handing out 64.0.0.0/8 in smaller blocks.  Perhaps
someone on this list can speak to the smallest block being handed out in
64.0.0.0/8.

----
Dani Roisman
Verant Interactive
hostmaster at verant.com
(310) 840-8753


> -----Original Message-----
> From:	Paul A Vixie [SMTP:vixie at mibh.net]
> Sent:	Monday, June 05, 00 2:04 PM
> To:	Hostmaster, Verant
> Cc:	'arin-discuss at arin.net'; Network Operations
> Subject:	Re: route filtering policies (from "split b" thread) 
> 
> > Thanks for the URL... hm.. /20 and shorter only in 64/8?  That's a bit
> > strict, no?  We have different networks off our 64.34.128/18 block,
> which we
> > would like to announce in /21 and /22 blocks.  There's a good chance we
> > won't aggregate, since the networks might each have OC3 or OC12 links to
> the
> > Internet, but in some places as slow as T1 between the two networks, and
> I
> > wouldn't want to backhaul accross the T1.
> 
> that's an incredibly irresponsible way to build a net.  if you're going to
> be a transit aggregator, then by all means get small blocks your providers
> and pay them extra to get cutouts.  the expectation we all have when you
> get
> an address block is that you intend to advertise it, not carve it up.
> 
> > Who should I contact at Verio to discuss losening the filtering policy?
> 
> won't help.  see http://www.mibh.net/mibh-peering.html and know that if
> you
> tried to get us to loosen it we would definitely not.  there are dozens if
> not hundreds of nets running with this policy.  the thing to change is
> your
> plan, not the commonly implemented route filtering policy of the whole
> 'net.