On Jan 20, 2008 5:10 PM, Patrick W. Gilmore <patrick@ianai.net> wrote:
If we take out the "proper attribution for the cost delta" out of the equation and the equipment is still not considered equal, I submit your idea of "proper attribution" is, well, not proper.
Patrick, 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. I didn't ask you to justify what you thought made my assessment of the attributable cost was wrong, although I'm glad you agree that you haven't done so. You also haven't adequately explained why the justification I used to arrive at those numbers is in error. I am, however, asking you to propose and justify an alternate pair of numbers: (A) The router model and price that you believe qualifies as an entry-level DFZ router which can reasonably be expected to have a 3-year service life in the DFZ if deployed today, and (B) The percentage of the router's cost which for the typical DFZ router task is attributable to the prefix count. (A) is simple: you find a middling-cheap piece of equipment that meets all the requirements for an entry level DFZ router and look up its price. You then explain what the key features of that piece of equipment are that qualify it as an entry-level DFZ router. For example, with my choice of a Cisco 7600 w/ a sup720-3bxl card, the features are: multigigabit layer-3 forwarding, BGP, supports the 300k+ prefixes likely to be needed within a 3-year deployment cycle. This equipment along with an 48-port gig-e card costs around $40k according to CDW. (B) is also simple: you find a middling-cheap piece of equipment that has all of the required features except for support for the large prefix count. Then you subtract its price from the price you got in A. The difference is the cost attributable to the prefix count for the router in (A). The reason that's the attributable cost is that the presence or absence of that one capability makes the difference between the cheaper or more expensive device being usable in the given application, namely as a DFZ router. For example, the Cisco 3750G has all of features except for the ability to hold 300k+ prefixes. Per CDW, the 48-port version costs $10k, so the difference (ergo cost attributable to prefix count) is $40k-$10k=$30k, or 75%. This is not the only way to arrive at the cost attributable to the prefix count for an entry level DFZ router, but it is by far the easiest to justify. I put it to you again: if you disagree with my numbers, propose and justify your own so that we can have a rational discussion about which justifications make more sense and thus which set of numbers is more likely to be correct. Or you can keep swimming in that river in Egypt. Its up to you. On Jan 20, 2008 5:10 PM, Patrick W. Gilmore <patrick@ianai.net> wrote:
On Jan 20, 2008, at 3:34 PM, William Herrin wrote:
( [entry level router's cost attributable to prefixes]/[expected lifespan] ) / [DFZ prefix count]
I notice you cut out the next two sentences:
<quote> In short, if the table were 50K prefixes instead of 250K, would these pieces of equipment be equivalent? The answer is a blatant "no". </quote>
Yes, I did. Its irrelevant to the cost analysis. The dividing line between the two classes of equipment is in the 8k-16k prefix range. Thus your statement is like saying, "If you drop the towing weight from 900 lbs to 200lbs, the 1000lb tow cable is still not functionally equivalent to a 100lb tow cable." That has something of a high "duh" factor. If you dropped the prefix count to 8k instead of 250k, the two pieces of equipment (virtual chassis stack, entry level DFZ router) would be equivalent for most DFZ router scenarios in which an entry-level DFZ router is used. 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. There is no gray area between the two and its appropriate to pick middling-low cost members of each group so long as the one from the "supports" group is a device that actually sees (or is expected to see) significant use in the DFZ application. On Jan 20, 2008 7:15 PM, Joe Abley <jabley@ca.afilias.info> wrote:
A new cisco 2851 can be found for under $10k and can take a gig of RAM. If your goal is to have fine-grained routing data, and not to carry gigs of traffic, that particular router is perfectly adequate.
Joe, For sub-gigabit applications you could also use Linux+Quagga on a $3k server. However, neither of these observations provide a valid data point for the given cost analysis. The question was: What does announcing a prefix into the DFZ cost "everybody else?" There are a number of constraints on the analysis which are implicit in that question. The relevant constraint here is that the equipment chosen for the various aspects of the analysis must be reasonably representative of the equipment deployed within the period for which the analysis is performed. Let me put it another way: Have you deployed or do you intend to deploy Cisco 2851's as DFZ edge routers in your network? That's what I thought. Had the question been, "Can we envision a way to re-engineer the Internet DFZ with technologies that either exist or are close at hand, what's the lowest cost per prefix we can achieve?" then the 2851 and Linux/Quagga would both make for interesting data points.
If you're prepared to consider second-hand equipment (which seems fair, since it's not as though the real Internet has no eBay VXRs in it) you could get better performance, or lower cost, depending on which way you wanted to turn the dial.
There have been years where there was so much truth to that statement that it would have to be taken into account in the cost analysis. This is not one of those years. As I type this, the lowest-cost Cisco router listed on eBay which is capable of both multigigabit switching speeds and the projected prefix count 12 months from now has an opening bid of $31k. 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