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Re: FW: /8s and filtering

  • From: Marshall Eubanks
  • Date: Tue Dec 10 14:54:12 2002


Did they ?
When ?

(I was involved with such a proposal, and it was turned down at the last ARIN meeting,
so I am curious if something else did get approved.)

Regards
Marshall Eubanks

On Tuesday, December 10, 2002, at 02:08 PM, Ejay Hire wrote:

Having a /24 doesn't indicate you are a network of any particular size,
ARIN ratified a policy that allows multihoming as justification for a
/24.

-ej

-----Original Message-----
From: N [mailto:nathan@stonekitty.net]
Sent: Tuesday, December 10, 2002 1:01 PM
To: Forrest
Cc: nanog@merit.edu
Subject: Re: FW: /8s and filtering


comments inline

On Tue, Dec 10, 2002 at 12:36:39PM -0600, Forrest wrote:

I was also curious about this - if I am a customer who wants to
multihome and can justify only a /24, I would go to an ISP which
has an
allocation from the Class C space rather than one from the Class A
space.
	It doesn't matter. For all practical purposes, basement
multihomers
only
care that their two or three providers have their route.

Maybe I'm missing something, but what good would it do for someone to
multihome if only their own providers accept their route, but nobody
else
does?  I realize that their block should be still announced with their

ISP's larger aggregate, but what good does this do if your ISP goes
down
and can't announce the large aggregate.
For the assigned block to be part of the same aggregate(of both
providers), that implys that the providers sharing the responsibility
for the aggregate. It happens, but is rare.  In this case, the providers
must accept more specific routes from each other, that is within the
space being aggregated.  If they do not share specifics, one uplink down
will cause a large percentage ~50% for the customer. This scenario is
valid for load balancing, but redundancy is fragile. The only advantage
I see is no limit to prefix length. You can do this with a /28 if you
want... given the above caveats are addressed.

If you're a smaller organization, perhaps you'll only have a /23 from
your
upstream provider.  With the filtering that seems to be in place, it
seems
like the only way you can truly multihome with a /23 is if it happens
to
be in the old Class C space.  Or is this wrong?
In today's VLSM world... the old classes have no bearing on filtering in
my experience. Prefix length discrimination knows no classfull
boundaries.

What seems to be needed is perhaps a /8 set aside by the RIR
specifically
to allocate to small organizations that wish to multihome that people
would accept /24 and shorter from.
There is value in the current filtering of longest prefixes... Allowing
anyone to multihome with BGP, using any network size, is going to double
our BGP tables overnight. Perhaps its good that you must be of some size
to participate in public BGP.  Many providers offer redundancy that is
more appropriate for the smaller networks.

--
,N

~Nathan - routing & switching dude/fly-boy/sport biker - San Jose CA~

T.M. Eubanks
Multicast Technologies, Inc.
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624       Fax     : 703-293-9609
e-mail : tme@multicasttech.com
http://www.multicasttech.com

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