On Mar 13, 8:03 am, Masataka Ohta <mo...@necom830.hpcl.titech.ac.jp> wrote:
The point of http://bill.herrin.us/network/bgpcost.html was that routers are more expensive because of bloated routing table. If you deny it, you must deny its conclusion.
Bill's analysis is quite interesting, but my initial take is that it is somehwat flawed. It assumes that the difference between what Cisco charges for a 7606 and a 3750G bears some resemblance to the actual bill of materials needed to support the larger routing table. That simply isn't the case: Cisco rightly charges what they think the market will bear for their routers and switches. I think a more realistic approach would be to use the cost differential between a router model X that supports 1M routes the same model configured to support 2M routes. Or perhaps we could look at the street prices for TCAM expansion modules. Either would be a better indicator of the incremental cost attributable to routing table size. The majority of costs in a mid-to-high-end Cisco/Juniper chassis are "sunk" and have nothing to do with the size of the routing table. The expensive routers currently used by providers are expensive because the market isn't that big in quantity, so they are not commodity items. They are designed to maximize the utility of very expensive long-haul fibers and facilities to a service provider. This means providing a high density of high-speed interfaces which can handle millions to billions of packets per second. They also provide lots of features that service providers and large enterprises want, sometimes in custom ASICs. These are features which have nothing to do with the size of the DFZ routing table, but significantly impact the cost of the device.
Given that global routing table is bloated because of site multihoming, where the site uses multiple ISPs within a city, costs of long-haul fiber is irrelevant.
I suppose smaller multi-homed sites can and often do take a full table, but they don't *need* to do so. What they do need is their routes advertised to the rest of the internet, which means they must be in the fancy-and-currently-expensive routers somewhere upstream. This is where the cost of long-haul fiber becomes relevant: Until we can figure out how dig cheaper ditches and negotiate cheaper rights-of- way, there will not be an explosion of the number of full-table provider edge routers, because there are only so many interconnection points where they are needed. Incremental growth, perhaps, but physical infrastructure cannot follow an exponential growth curve.
As it costs less than $100 per month to have fiber from a local ISP, having them from multiple ISPs costs a lot less is negligible compared to having routers with a so bloated routing table.
For consumer connections, a sub-$1000 PC would serve you fine with a full table given the level of over-subscription involved. Even something like Quagga or Vyatta running in a virutal machine would suffice. Or a Linksys with more RAM. Getting your providers to speak BGP with you on such a connection for that same $100/month will be quite a feat. Even in your contrived case, however, the monthly recurring charges exceed a $1000 router cost after a few months. Enterprises pay several thousand dollars per month per link for quality IP transit at Gigabit rates.