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