FW: /8s and filtering

Marshall Eubanks tme at multicasttech.com
Tue Dec 10 19:36:34 UTC 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.)

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 at stonekitty.net]
> Sent: Tuesday, December 10, 2002 1:01 PM
> To: Forrest
> Cc: nanog at 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 at multicasttech.com

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