On Mon, 27 Aug 2001, Roeland Meyer wrote:
Please detail the exact costs of a, BGP inserted, routing table entry. Is it, maybe, 50 cents?
What is the cost of the prefix inserted with causes somebody other's boxes to crash and burn? The "last" one? We don't know at which point the network simply passes the threshold of being able to converge faster than the next update comes. That does not make the cost of every update pushing the network closer to that point immaterial. Unlike traffic overload, routing flap overload is _not_ self-correcting. In fact, given the present technology it is very likely to be self-amplifying (i suspect that most current BGP implementations in case of severe overload would simply delay keepalives until peers start resetting sessions; having BGP to run over strictly serializing transport (TCP) does not help, either). The only known non-capital intensive fixes are route aggregation and intentionally degrading routing system responsiveness (aka flap damping). Both have severe limitations. When they run out of gas, it's forklift upgrade to the new generation of routers. Keeping up with Moore's law is not free. So far, the current backbone upgrade cycle kept up. Assuming that the capital cost of the backbone routing equipment installed globally is about $5bln (this is an out-of-the-blue figure), and it currently works at design capacity with approx. 100k prefixes, the per-prefix cost of forced upgrade is about $50k, not including labour costs, and indirect costs of decreasing network stablility causing customer dissatiscfaction and resulting in expensive customer churn. Obviously, not all cost may be attributed to maintaining routing infrastructure ("traditionally" the upgrades are justified by the need to maintain competitive backbone speed). Times have changed, though, and upgrading switching capacity no longer has to be a wholesale box replacement. Unfortunately, this is not the case with routing update processing capacity (having parallelized routing stack implementations helps, but not all that much). Therefore, the cost of extra prefix is definitely not $0.50; it is _much_ higher. --vadim