[135728] in North American Network Operators' Group
Re: Another v6 question
daemon@ATHENA.MIT.EDU (Mark Andrews)
Fri Jan 28 04:26:25 2011
To: Per Carlson <pelle@hemmop.com>
From: Mark Andrews <marka@isc.org>
In-reply-to: Your message of "Fri, 28 Jan 2011 10:10:00 BST."
<AANLkTinDQdH5Z==mbYvm-OstA2m-WVkxo7vKyLc8x7vf@mail.gmail.com>
Date: Fri, 28 Jan 2011 20:25:28 +1100
Cc: nanog group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
In message <AANLkTinDQdH5Z==mbYvm-OstA2m-WVkxo7vKyLc8x7vf@mail.gmail.com>, Per
Carlson writes:
> Hi Owen.
>
> > The downside is that it doesn't provide enough bits for certain kinds of =
> auto-topology
> > management that are being considered by CE vendors. I highly recommend /4=
> 8 instead.
>
> I've seen this claim (you need a /48) from your side several times,
> but never seen any explanation why a /56 won't work.
>
> Is there any requirement that sub-delegations must happen on 8-bit
> boundaries? AFAICS there is at least nothing in the RFC. Wouldn't for
> example a nibble boundary work equally well (splitting a /56 into 16
> /60s, each containing 16 /64s)?
>
> I don't challenge the claim, I'm just trying to understand the
> rationale behind it.
There is a model where the down stream CPE devices always request
powers of two prefixes. It doesn't take many CPE devices daisy
chained to exhaust 8 bits.
The other model is to just request as many /64 as needed using
multiple requests with different identifiers. You can daisy chain
out past the limits of IPv6 to route packets with that model.
Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
