estimation of number of DFZ IPv4 routes at peak in the future

Jeff Wheeler jsw at
Sun Mar 13 16:40:49 CDT 2011

On Sun, Mar 13, 2011 at 3:42 PM, Christopher Morrow
<morrowc.lists at> wrote:
> not everyone drinks the mpls koolaide... so it's not always 'just a
> label switch' and depending upon how large your PE mesh is, there are

If it isn't just a label switch, then features can (and sometimes do)
drive upgrades (therefore costs.)

> not need that info, but the edge likely does, yes? Have 100g customers
> today? planning on having them in the next ~8/12/18 months?

If you did your purchasing the way Bill Herrin suggests, you'd buy a
box with 100GbE ports for a POP or branch that is not projected to
have 100GbE customers, just because it's the biggest box.  His
position is that man-power to do an upgrade is always more costly than
capital dollars for the actual equipment, and ignores the fact that
the biggest box is by no means guaranteed to offer new *features*
which may be required.

I think most of your post is responding to a mis-read of my post, so
I'll skip back to the FIB size question at hand:

> sometimes... sometimes it's just business. I suppose the point here is
> that a box doesn't live ~12 months or even 24, it lives longer.
> Planning that horizon today is problematic when a box today (even the
> largest box) tops out just north of 2m routes (v4, I forget the mix
> v4/6 numbers). your network design may permit you to side step that
> issue in places, but planning for that number is painful today.

I'm not comfortable making the generalization that buying the box with
the largest available FIB is always the most cost-effective choice.
In some "box roles," traffic growth drives upgrades, and increased FIB
size in future boxes will be one advantage of a future upgrade that
also increases port speed or density.  In other "box roles," features
drive upgrades, and again, FIB size may increase in future boxes which
will be bought anyway to gain desired features.

It's foolish and overly-simplistic to assume that every box upgrade
will be driven by an eventual exhaustion of FIB capacity.

Currently, FIB capacity is being driven by the needs of service
providers' VPN PE boxes.  This is great for networks that do not have
that need, because it is driving FIB capacity up (or cost down) and
further reducing the chance that FIB exhaustion will trigger an
upgrade before other factors, such as port speed/density/features.

Jeff S Wheeler <jsw at>
Sr Network Operator  /  Innovative Network Concepts

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