[arin-ppml] Rationale for /22

Steven E. Petty spetty at iconnect-corp.com
Tue Jul 28 12:34:55 EDT 2009

  Obviously the primary reason for a limit is the accepted minimum routing entry size of a /24.  Of course, you knew that.  So why ask the question?

-----Original Message-----
From: arin-ppml-bounces at arin.net [mailto:arin-ppml-bounces at arin.net] On Behalf Of Kevin Kargel
Sent: Tuesday, July 28, 2009 12:30 PM
To: William Herrin; Joel Jaeggli
Subject: Re: [arin-ppml] Rationale for /22

Based on what everyone is saying about the /24 issue - and for the purpose of argument accepting that /24 will cause no problems - then why not take it a step further and remove any maximum length netmask restriction for a multi-homed entity with a single allocation.

One entity with one allocation will generate one table entry regardless of what size it is, so why limit them to a /24.  I am sure there are entities out there who could operate just fine out of a /25 or even a /32, and so long as they are not creating gratuitous route table entries then we could be more efficient allowing them to only consume the space they need.

> -----Original Message-----
> From: arin-ppml-bounces at arin.net [mailto:arin-ppml-bounces at arin.net]
> On Behalf Of William Herrin
> Sent: Tuesday, July 28, 2009 10:30 AM
> To: Joel Jaeggli
> Subject: Re: [arin-ppml] Rationale for /22
> On Tue, Jul 28, 2009 at 10:32 AM, Joel Jaeggli<joelja at bogus.com> wrote:
> > William Herrin wrote:
> >> Given the shortage of IPv4 addresses, why structure the policies so
> >> that we give anyone more than they actually want?
> >
> > The minimum number of addresses that can be used may not in fact
> > reflect the minimum that should be used.
> >
> >        For the purposes of minimizing fragmention.
> >
> >        Supporting basic network operation (it's nice when traceroute
> >        and pmtud work) because your intermediate routers are privately
> >        numbered.
> >
> >        Limiting the consequences of imagination failure, which may
> >        sound flippant but renumbering, requesting an additional block,
> >        or and point one and two are good reasons to make a potential
> >        multi-homer justify the assignment of a block of the appropriate
> >        size for that activity.
> Hi Joel,
> I could almost see that argument on the ISP side but it doesn't make
> sense to me on the end-user side, particularly when they may be
> trivially multihomed. I surely wouldn't want to presume that I know
> every registrant's address count needs better than he does though. f
> you don't mind, let's just focus on the downside risk.
> So, the registrant asks for a /24 and a year later his replacement who
> is a better network engineer figures out he really needs a /22 after
> all. What's the impact? Other than insisting on giving him a /22 up
> front, is there another way to mitigate that impact?
> Regards,
> Bill Herrin
> --
> William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
> 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
> Falls Church, VA 22042-3004
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