Re: Review of draft-ietf-6man-rfc4291bis-06

Lorenzo Colitti <lorenzo@google.com> Fri, 13 January 2017 07:40 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Fri, 13 Jan 2017 16:40:19 +0900
Message-ID: <CAKD1Yr2Njjd8_Mr+6TRFF6C5pdcX4yFgpFVyEkykDuytu2B8mg@mail.gmail.com>
Subject: Re: Review of draft-ietf-6man-rfc4291bis-06
To: Randy Bush <randy@psg.com>
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Cc: IPv6 List <ipv6@ietf.org>, IETF <ietf@ietf.org>, int-dir@ietf.org, Bob Hinden <bob.hinden@gmail.com>, draft-ietf-6man-rfc4291bis.all@ietf.org
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On Fri, Jan 13, 2017 at 4:34 PM, Randy Bush <randy@psg.com> wrote:

> >> we have had to fight massively with vendors to make it classless.
> >> please do not give them excuses to break things.
> >
> > On a lot of hardware /65 - /126 is not very well-supported.
>
> guess the business reason why.  the classful spec gave them a good
> excuse to do a tcam rinse repeat.  i pay to feed the darned  chickens,
> it's time to break the egg.
>

But it's true that supporting /65-/126 increases the cost of the device.
The extra bits have to go somewhere. I think I've seen hardware that just
converted all prefixes to 128 bit if there was at least one /65 - /126
prefix in the FIB. That costs money for RAM. Obviously that's silly if
those prefixes are frequent, and you can save that money using better
software engineering - but software engineering costs money too. Prefixes
don't cost money, and if we know that we won't run out of them, what's the
problem?