[arin-ppml] IPv4 SWIP requirements (?)

Owen DeLong owen at delong.com
Wed Jun 28 06:37:28 EDT 2017

Based on William’s logic below, I would advocate for 49.


> On Jun 19, 2017, at 8:05 PM, William Herrin <bill at herrin.us> wrote:
> On Mon, Jun 19, 2017 at 1:37 PM, David R Huberman <daveid at panix.com <mailto:daveid at panix.com>> wrote:
> Based on comments so far, most agree that a /48 should be SWIP'ed since it is routable on the internet, and since so far the majority seems to think that /56 is small enough to not require SWIP, this leaves 7 choices of /49 to /55 to set the limit for SWIP in the Draft.
> I think that when we consider SWIP boundaries, we should take into account strictly technical considerations, and not arbitrary ones.  I think the argument for requiring a /48 or larger to be SWIPed is well-grounded in network engineering practices.  I'm not sure I understand the technical argument for anything smaller than a /48 being mandatory.
> Hi David,
> The obvious technical argument against Nibble "or larger" is that it encourages assignment on non-niblle boundaries. If /56 requires SWIP, the ISP has reason to assign /57 instead of /56.  That makes IPv6 assignment as messy as IPv4. If instead /55 requires SWIP, the likely ISP default value becomes /56, a good nibble-boundary choice. A policy which starts requiring SWIP at Nibble+1 implicitly encourages the ISP to set their default assignment size at a nibble boundary which is well-grounded in network engineering practices
> So first and foremost it is technologically correct to set the SWIP boundary to start at "larger than Nibble" or "Nibble+1 or larger." 
> Since "larger than /48" and "/47 or larger" are ruled out by /48's independent routability (also a technical consideration) and /64 is ruled out for preventing the intended end-user  IPv6 routing ability (also a technical consideration), that leaves "larger than" /52, /56 and /60 as the only -technically reasonable- options. 
> Regards,
> Bill Herrin
> -- 
> William Herrin ................ herrin at dirtside.com <mailto:herrin at dirtside.com>  bill at herrin.us <mailto:bill at herrin.us>
> Dirtside Systems ......... Web: <http://www.dirtside.com/ <http://www.dirtside.com/>>
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