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Re: NSPs and filters
From: Daniel Senie <dts () proteon com>
Date: Sat, 12 Jul 1997 23:25:51 -0400

Dave Pokorney wrote:


From provider side of things they have more packets to fly than that of
FDT.  The more one has to filter, the less cpu there is to route packets..
I suspect that this may be the only cause...

If a router is designed to allow handling of packet filtering
efficiently, then
it CAN be done without undue loading.

Perhaps you're all using equipment and software that doesn't permit
filtering at
line speeds. If that's the case, then INSIST that this be changed in the
version of software or hardware you buy. Perhaps my co-author of the
draft can comment, but I thought Cisco was implementing packet filtering
on the
switch processor cards to allow just this kind of filtering. Since I
don't use
Cisco gear (they're our competitor), I don't have all the scoop there.

Another thing I'd like folks to consider. Many of you manage the routers
at customer
sites. I would guess that in most cases, folks forging IP addresses are
NOT the
folks who have access to routers at a site. If you, as an ISP, manage
the router at
the customer end of a circuit, ADD FILTERS THERE! Make sure that packets
from the customer's router to your network are VALID addresses. The
router at a
customer site plugged into a T1 should be able to filter outbound
packets at T1
speeds without trouble. If the routers you're using out there can't
handle that
speed, then you're using the wrong gear.

One way or another, both ISP's and customers must take responsibilty for
addresses. If the network community will not take responsibility for
this, I
fear the courts may ultimately step in. Let's use the technology we
have, and
develop additional technology as needed, rather than risk legal

Dan Senie
OpenROUTE Networks, Inc.


On Fri, 11 Jul 1997, Jon Lewis wrote:

Why is it that the NSPs I've encountered refuse to do any sort of sanity
filtering on their customer connections?  i.e. If UUNet knows that FDT has
only 205.229.48/20 and 208.215.0/20, why should they let me send traffic
through their network with random source addresses?

FDT has been the target of forged source address UDP attacks for the past
2 days.  It's all being stopped at our router that takes our UUNet T1, but
the extra T1 traffic is causing UUNet's usually unreliable network to be
even less reliable, and we've lost connectivity to UUNet several times
this evening.

  5 minute input rate 1326000 bits/sec, 318 packets/sec
  5 minute output rate 469000 bits/sec, 286 packets/sec

PUNet suppost says there's nothing they can do, and that I should talk to
their security people about buying a firewall for FDT on monday...like a
firewall on our side of the T1 is going to do us a lot of good....

 Jon Lewis <jlewis () fdt net>  |  Unsolicited commercial e-mail will
 Network Administrator       |  be proof-read for $199/message.
 Florida Digital Turnpike    |
________Finger jlewis () inorganic5 fdt net for PGP public key_______

Daniel Senie                  dts () openroute com
OpenROUTE Networks, Inc.      http://www.openroute.com/

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