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Re: Lazy Engineers and Viable Excuses

  • From: Jared Mauch
  • Date: Tue Aug 26 10:48:20 2003

On Tue, Aug 26, 2003 at 10:10:57AM -0400, Leo Bicknell wrote:
> In a message written on Tue, Aug 26, 2003 at 09:55:30AM -0400, Jared Mauch wrote:
> > > Yes, it is that hard.  Sadly, almost everyone I see push the IRR
> > > works for a small ISP.  And at least half of those work for a small
> > > ISP in Europe.
> > 
> > 	C&W, Level3, Global Crossing and NTT/Verio are small isps?
> Please correct me if I'm wrong, but they all use the IRR to filter
> customers.  That's a fine application of the IRR, and one I encourage.
> I don't think any of them use the IRR to filter peers.  Indeed, I
> can provde they don't filter certian big peers due to the fact they
> don't register thier routes at all. :)

	I'd have to imagine all those proxy registered routes
for sprint prefixes that you see in the LEVEL3 rr are used for
something other than consuming disk space.

> My rant is on peer-to-peer filtering.  Customers should always be
> filtered by every ISP.  Period.  ISP's should automate that as much
> as possible for their customers, and using the IRR is a fine solution.
> > >     Every ISP on the planet would have to reconfigure their filters
> > >     for /EVERY/ customer change worldwide.
> > 
> > 	Exactly.  And this is a bad thing how?  You can't plan ahead
> > and register route objects 24 hours in advance of a customer
> > being installed?
> It's a bad thing because it doesn't scale.   It's not a matter of
> before or not, it's that there is a linear relationship between the
> size of the internet and the processing needed to be done by each
> ISP.  That doesn't scale.
> > 	Hmm.. you are missing some of the benifits that I
> > see associated with this.  If I have a list of all the
> > prefixes that I could get sourced from MFN/ in a easily queryable
> > format, I can install anti-spoofing filters.
> No, you couldn't.  Please go back and take routing 101 again.

	Yes I could, if you and your customers had all the routes
they sourced packest from registered.  This has nothing to do
with routing 101, this has to do with filtering customers and
having anti-spoofing filters as well as route objects for any
prefix you will source packets from.  

> Internet routing is asymetrical, the source of the packet has nothing
> to do with where the return route points in the core.  If it were that
> simple we could just use Unicast RPF on all peering links and spoofing
> would be a thing of the past.

	Actually, it sounds like you're not that clued on how Juniper
handles unicast-rpf at all (for example).  It allows you to do
unicast-rpf on a per-interface basis for all routes that you receive
regardless of if they're installed for forwarding.  this means that
people could use this and set the necessary community so it doesn't
leave the peer router (no-export + no-advertise), or prepended so much
it's not used and use that to perform filtering.  If best-path
for returning the packet is not across the link, it will still
not drop this.  This is a nice feature on the part of Juniper.

	I suggest you (and others) take a look at these features and
use them where possible to mitigate spoofed DoS attacks from your

	- jared

Jared Mauch  | pgp key available via finger from
clue++;      |  My statements are only mine.

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