[101943] in North American Network Operators' Group
Re: Cost per prefix [was: request for help w/ ATT and terminology]
daemon@ATHENA.MIT.EDU (William Herrin)
Mon Jan 21 00:42:56 2008
Date: Mon, 21 Jan 2008 00:42:04 -0500
From: "William Herrin" <herrin-nanog@dirtside.com>
To: "Patrick W. Gilmore" <patrick@ianai.net>
Cc: nanog@merit.edu
In-Reply-To: <A1DD07CA-FC9C-43B6-BB43-2E2239B6FD2F@ianai.net>
Errors-To: owner-nanog@merit.edu
On Jan 20, 2008 9:46 PM, Patrick W. Gilmore <patrick@ianai.net> wrote:
>
> On Jan 20, 2008, at 8:46 PM, William Herrin wrote:
>
> > So at this point, the part of my analysis you still dispute is where I
> > claimed that 75% of the $40k cost of an entry-level DFZ router was
> > attributable to its ability to carry the needed prefix count.
>
> As I said before, your calculation is in error. I very clearly
> explained why, but you threw out my explanation below.
Patrick,
Just to clarify, your "explanation" (which I've clipped again) claims
an error in the source numbers, not an error in the calculation.
Essentially, you've said that when I determined the percentage of an
entry level DFZ router's cost attributable to the prefix count I chose
as my point of comparison a piece of equipment that is not otherwise
functionally equivalent for the DFZ router task. Because an equivalent
piece of equipment would be more expensive, the percentage I found to
be attributable to carrying and using the prefixes was too high.
I disagree, but I acknowledge that you've offered reasonable support
for the claim that 75% is not the correct percentage of the router's
cost attributable to the DFZ prefix count.
So, run with it. Take the analysis you just did and come up with a
justified estimate of the percentage of the cost of a representative
DFZ router which is attributable to its need to carry a full BGP
table. If you think 75% is too high, lets talk about the number you
think is correct and why. Perhaps you feel that only the cost of the
pfc3bxl and msfc3 daughterboards should be attributable to the prefix
count? Whatever. Pick your numbers and justify them as I have. Then
lets plug your number in to the formula and see what we get.
> Apparently I
> assumed you had knowledge you did not. Please forgive me for not
> assuming you were ignorant. I shall not repeat my mistake.
Or, you could just respond with another ad-hominem attack. It won't
advance anyone's understanding of the cost of carrying prefixes in the
DFZ, but it might make you feel superior.
> I'm certain there are networks who would (do?) use 3750s if the v4
> table were the size of the v6 table. But they tend to be smaller
> networks, with few or no BGP customers, and not much traffic. No
> 'tier one' network would, and most networks their size would not.
> Most networks half their size would not.
I don't believe that a tier 1's choice of DFZ routers is
representative of the average DFZ router. Their requirements are much
higher than the norm. If you'd like to argue the opposite position,
I'll be very interested to see what numbers you propose for the
representative router cost and the percentage attributable to handling
the prefix count.
> > For cost analysis purposes, you need only consider a true/false
> > condition here:
> > The device supports the required prefix count.
> > The device does not support the required prefix count.
>
> Would that the world were so simple.
In cost analysis as in software development, all complex problems
reduce to a sequence of simple steps.
Regards,
Bill Herrin
--
William D. Herrin herrin@dirtside.com bill@herrin.us
3005 Crane Dr. Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004
