Re: Generally accepted announcement sizes

[Kai Schlichting <kai () pac-rim net>]

At Thursday 05:35 PM 6/22/00 , Tony Tauber wrote:

> On Thu, 22 Jun 2000, Mike Heller wrote:
> > Can anyone point me to a centralized resource for Tier 1 and Tier2
> > providers'  accept policies?  I have found that when some of my circuits go
> > down various parts of the 'Net become unreachable and I attributed that to
> > the size of that announcement being a /24.  I assume that the carriers I'm
> > having issue with are not using RADB as I registered all of my netblocks,
>
>
> To find out exactly why your multi-homing set-up isn't working, 
> I'd work with your providers' operations staff.  Perhaps set up
> a time to test the fail over with them on hand to help you analyze
> by looking at the routes on both.  It should be possible for them
> to help check the behavior of traffic over a third provider as well
> if the providers are worth their salt.

A rather complex setup on their side, as far as I can tell from
route-server.cerf.net, route-views.oregon-ix.net and route-server.ip.att.net:

iwon.com is AS 14829, and they seem to announce 3 networks:

They announce 165.254.159.0/24 to AS 2914 (Verio) and AS 1785 (AppliedTheory)
At the Oregon IX, the path via Verio is seen 15 times, via AT only 2 times.
That's is an indicator of connectivity (and likely density of
interconnectivity of providers to Verio vs. AT) right there.
It's more balanced 5:4 (Verio:AT) at AT&T's route view.

They announce 209.10.180.0 to AS 701 (UUnet), 4513 (PFM/Globix), 1239 (SL).
At the Oregon IX, this is seen somewhat balanced between the 3, but at
AT&T, it's 8 paths to UUNet or SL, only one path to PFM/Globix.

They announces 216.73.19.128/25, which is solely seen through AS 2914 (Verio)
at the Oregon-IX, and only 4 times at that. As expected, Verio seems
to accept this as a customer route, but few of their peers accept the /25,
Note that AT&T and CERF.net are not seeing this specific, but they see
the larger /18 aggregate from AppliedTheory only, which is probably what
90% of all traffic to this network . It's a wonder that the
/25 is seen at all: I think it should be withdrawn for sanity's sake.


So, what exactly are you trying to accomplish, Mike?
One thing is clear: the third network will always receive most traffic
from AT, the second one mostly from UUnet+Sprint, the first one (which
I believe you are referring to) mostly from Verio. The right way to
overcome this is likely not to play with BGP toys like AS_prepend or
making your providers manipulate the local_pref for you (and I see
that Verio and UUnet don't seem to be crossing paths, at least for
the first network listed), but by utilizing bigger networks:
/22's in the >204.0.0.0/8 space are looking damn good in terms of
'being heard' compared to /24's. Did I mention that Verio seems to
be the only one filtering at /20 boundary in 62/8 and 63/8 ? As a
customer, you won't have that problem, obviously.

bye,Kai