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RE: Cost per prefix [was: request for help w/ ATT and terminology]

daemon@ATHENA.MIT.EDU (Neil J. McRae)
Sun Jan 20 17:13:27 2008

From: "Neil J. McRae" <neil@domino.org>
Date: Sun, 20 Jan 2008 21:43:02 +0000
To: "Neil J. McRae" <neil@domino.org>,
        William Herrin <herrin-nanog@dirtside.com>,
        "Patrick W. Gilmore" <patrick@ianai.net>
CC: <nanog@merit.edu>
Errors-To: owner-nanog@merit.edu


Delivering BGP solutions for end users is starting to get very expensive pa=
rticularly for those networks with lots of smaller pops, I think some effor=
t to look at how this might be better delivered without access boxes needin=
g to know the entire routing table esp in light of IPV6

Regards,
Neil
(missed the end of the last email!)
=20

-----Original Message-----
From: William Herrin <herrin-nanog@dirtside.com>
Sent: 20 January 2008 17:22
To: Patrick W. Gilmore <patrick@ianai.net>
Cc: nanog@merit.edu
Subject: Re: Cost per prefix [was: request for help w/ ATT and terminology]


On Jan 20, 2008 9:46 AM, Patrick W. Gilmore <patrick@ianai.net> wrote:
> On Jan 20, 2008, at 6:06 AM, William Herrin wrote:
> > On Jan 19, 2008 11:43 PM, Patrick W. Gilmore <patrick@ianai.net>
> > wrote:
> >> On Jan 19, 2008, at 12:55 PM, William Herrin wrote:
> >>> There was some related work on ARIN PPML last year. The rough
> >>> numbers
> >>> suggested that the attributable economic cost of one IPv4 prefix in
> >>> the DFZ (whether PI, PA or TE) was then in the neighborhood of $8000
> >>> USD per year.
> >>
> >> I haven't seen that work, but I am guessing this number is an
> >> aggregate (i.e. every cost to everyone on the 'Net combined), not
> >> per-
> >> network? See, I'm just looking at that TWO BILLION DOLLARS PER YEAR
> >> number and thinking to myself, "um, yeah, right". :)
> >
> > Patrick,
> >
> > That was a worldwide total, yes. The cost per prefix per router is
> > obviously only measured in cents per year.
>
> I think you mean in tiny fractions of a single cent per router per
> year

No, I don't. The lower bound for that particular portion of the cost
analysis is easy to calculate:

Entry level DFZ router: $40,000
Stacked 1U layer-3 switches with similar switching capacity and port
density: $10,000
Difference between the two: The switch stack can't handle the DFZ prefix co=
unt.
Cost delta (attributable to the DFZ prefix count): $30,000
Expected lifespan in the DFZ of an entry-level router: 3 years
Prefixes in the table: 245,000

Calculation: The LOWER BOUND for the cost per prefix per router can be
calculated as:
( [entry level router's cost attributable to prefixes]/[expected
lifespan] ) / [DFZ prefix count]
($30,000/3)/245,000 =3D $0.04 per router per year, i.e. 4 cents.

Bear in mind that 4 cents per year is a LOWER BOUND. It costs AT LEAST
4 cents per router per year to carry one prefix in one DFZ router.
There are also routers in the DFZ which cost $500,000 where much more
than $30,000 is attributable to the prefix count.


>.  While there are 27K ASes ($0.30/year/AS, remember?), there are
> many more routers which carry a full table.

Yes, there are many more routers than ASes. In my original analysis on
ARIN, I estimated that there were some 200,000 routers carrying a full
table in the DFZ. The consensus at the time was that the number was
closer to 150,000 than 200,000. 150,000 times 4 cents yields a LOWER
BOUND economic impact of $6,000 per prefix per year, $1.5B overall.

Again, that's a lower bound on the estimate. The upper bound is
perhaps twice that with the highest probability cost around $8,000 per
prefix per year.


> Comparing cisco & Juniper's annual revenue to the cost of a prefix is
> like comparing Ford & GM's revenue to the cost of bulbs in
> headlights.  Hell, most of cisco's revenue is not even related to
> routers doing a full table.

Of course not. However, it makes a good sanity check on the cost
estimate: If the costs attributable to prefix count sums to more than
their revenues then there must be an error in the math. My point was
that the $8000/prefix/year estimate passes the sanity check with
plenty of room to spare.



> > The thread started here:
> > http://lists.arin.net/pipermail/ppml/2007-September/008927.html
> > It was originally an argument of about the cost of doing PI for IPv6,
> > which according to Cisco product literature consumes twice the amount
> > of space in the FIB as routes for IPv4.
>
> Anyway, thanks for the link.  I must be missing something seriously
> important to the calculation.  Perhaps it includes things like human
> time to upgrade equipment or filters or something?  I'll see how the
> calculation=20


[The entire original message is not included]=


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