No one behind the wheel at WorldCom

Mon Jul 15 18:34:07 UTC 2002

On Mon, 15 Jul 2002, Frank Scalzo wrote:

> The problem with doing that is you do not get fine grained control. You
> can only say only send me 50k routes, and things not from other peers.
> The really nifty part about prefix-limiting your peers is when they
> deaggregate toward you, you drop all your bgp sessions to them at once,

Your max prefixes should give wide enough margin and larger peers should be
responsible to let you know of any large %-age increase in prefixes happening in
one go.

> completely depeering. You still cannot prevent announcement of weird
> routes like 63/8. Do not be fooled into believing that just because a

63/8 I dont like but I can live with.. multiple 63.x.x.0/24 I cant

> network is big they know what they are doing. Some of the 63/8
> announcements I have seen came by way of sprint. Let's step back and
> think about this on a security front, anyone with access to a tier 1
> ISPs router can dos anyone in the internet, just by throwing in a null
> route for the block that is more specific then the one they have
> advertised. Granted not easily done, but just the same I like to be the
> only one who can break my network.

I thought someone would mention that.. the post before mine suggested there was
no method of filtering, I suggested there was a way to improve greatly the
restrictions without killing CPU. I still acknowledge that its possible to break
it by hacking BGP routes but something is better than nothing.

> Unfortunately Majdi is correct, we do not have sufficient functionality
> in today's routing software to fix the problem. Oh well I guess it has
> worked for this long.

I agree also, and cant fix but can offer improvement.

Steve

> 
> -----Original Message-----
> From: Stephen J. Wilcox [mailto:steve at opaltelecom.co.uk] 
> Sent: Monday, July 15, 2002 8:39 AM
> To: Majdi S. Abbas
> Cc: Frank Scalzo; nanog at merit.edu
> Subject: Re: No one behind the wheel at WorldCom
> 
> There are different types of filter tho and I'd suggest they are
> suitable in
> different circumstances.
> 
> eg 
> small peer < 100 prefixes - build prefix filter list, as path list
> middle peer - either depending on requirement (eg cust, peer)
> large peer > 1000 prefixes - as path filter plus max prefix
> 
> I'm not implementing the above so the numbers and suggestions are a
> little
> arbitrary but I'm making the point that you can filter smaller peers who
> are
> less experienced and more likely to give an error and for larger peers
> you have
> to be less granular but can still impose failsafes without increasing
> CPU.
> 
> Steve
> 
> 
> On Mon, 15 Jul 2002, Majdi S. Abbas wrote:
> 
> > 
> > On Mon, Jul 15, 2002 at 01:58:44AM -0400, Frank Scalzo wrote:
> > > See now we are back to the catch 22 that is IRR. No one will use it
> because 
> > > the data isnt there, and no one will put the data into it because no
> one 
> > > uses it.
> > 
> > 	[CC: list trimmed]
> > 
> > 	Actually, I think you'll find that bad data is only a small part
> > of the problem; even with good data, there isn't enough support from
> > various router vendors to make it worthwhile; it's effectively
> impossible
> > to prefix filter a large peer due to router software restrictions.  We
> > need support for very large (256k+ to be safe) prefix filters, and the
> > routing process performance to actually handle a prefix list this
> large,
> > and not just one list, but many.
> > 
> > 	IRR support for automagically building these prefix lists would
> > be a real plus too.  Building and then pushing out filters on another 
> > machine can be quite time consuming, especially for a large network.
> > 
> > > I think the way to get IRR into the real world production realm, is 
> > > to really drive home the issue w/IPV6.
> > 
> > 	This still doesn't solve the scaling issue.  This is no
> different
> > than running your own RR, which many ISPs already do -- and they still
> 
> > have to exempt many of their peers.  Typically, RR derived prefix
> filtering
> > is something reserved for only their transit customers.
> > 
> > 	If it were that easy, everyone (well, some people) would be 
> > doing it.
> > 
> > 	--msa
> > 
> 
> 