Re: It's Ars Tech's turn to bang the IPv4 exhaustion drum

[Alain Durand <alain_durand () cable comcast com>]

What I was told is that, yes, the packet get routed through the ASIC, but it
has to go there twice... Hence reducing the pps by a factor of 2 compare to
IPv4. Some vendors had shortcuts that, if the prefix len was < 64, only one
pass was necessary.

Caveat, this may not be true for all vendors or all models of all vendors.
YMMV.

  - Alain.


On 8/19/08 4:22 PM, "Kevin Oberman" <oberman () es net> wrote:

> > Date: Tue, 19 Aug 2008 14:30:38 -0400
> > From: Alain Durand <alain_durand () cable comcast com>
> >
> > On 8/19/08 1:50 PM, "sthaug () nethelp no" <sthaug () nethelp no> wrote:
> >
> > > > In practice, many routers require the packet to go twice in the hardware if
> > > > the prefix length is > 64 bits, so even though it is a total waste of
> > > > space,
> > > > it is not stupid to use /64 for point-to-point links and even for
> > > > loopbacks!
> > >
> > > Could you provide some documentation on this? First I've heard about it.
> >
> > Ask your favorite router vendor. This has been confirmed to me by at least 3
> > major one we use.
>
> Odd. I have asked both of our router vendors and they have confirmed
> that they route in the ASIC based on the full address, not just the
> first 64 bits. (I believe one of them based on actual testing. I am
> suspicious of the other.)
>
> That said, one does use a few bits for something else (port) and does
> not load them into the FIB, so I believe they route on 120 bits, not
> 128.
>
> I'd love to get complete verification of the real facts of this.