Not necessarily. The number of paths in a city often has little to do with the providers and how many paths they would like offer, or at least did when they had the money to build. Many times the contraint is not demand but the zoning laws on where paths can be laid. Even if a client demanded and was willing to pay for the diverse paths there can be none available. Thus some times providers simply don't tell what the physical pathways are because they can be no different than the ones the prospective client is already using. Quite simply it is not a problem that the market can solve on its own because the market does not completely own the problem, state and municiple authorities also have a large piece of the game. The number of paths varies widely between cities, and has little to do with demand in those cities for diversity or how critical they might be to the nation as a whole. ----- Original Message ----- From: jmalcolm@uraeus.com Date: Saturday, April 16, 2005 2:00 pm Subject: N+? redundancy
Michael.Dillon@radianz.com writes:
In my opinion, the following rule of thumb is reasonable.
1 path is enough for a site/enterprise that shuts down its services evenings and weekends.
2 paths is enough for a site/enterprise that provides a 24 hour, 7 day per week service.
3 paths is enough for a population center with under a million inhabitants.
5 paths is enough for a population center with over a million inhabitants.
And a very few population centers such as New York, London, Tokyo, and Cheyenne Mountain should probably have more than 5 paths.
Given that anything larger than a single enterprise has no central coordinating body, how is it useful to say how many paths is "enough" for a city of any size? Service providers will build as many paths as make commercial sense, whatever that may be, and if customers have opinions and are willing to back it up with money, they should express those opinions to their providers.
Even if a client demanded and was willing to pay for the diverse paths there can be none available.
When there is demand for something that the market cannot supply due to political constraints, then there are political solutions.
The number of paths varies widely between cities, and has little to do with demand in those cities for diversity or how critical they might be to the nation as a whole.
If requirements for network path separacy can be communicated in such a way that people clearly see that it is critical to the nation (or any other political body) then it is possible to release additional path opportunities to the market. The rules of thumb that I suggested had to do with how much network redundancy is likely to be "enough network redundancy". I also didn't supply the numbers to back up these rules because, to the best of my knowledge, nobody has studied the risks involved in enough detail to do analyse this. I did receive one anecdotal account related to the ice storm in Montreal back in '98, I believe. It seems that this city of over 1 million inhabitants had 5 paths providing electricity to the city and 4 of those paths were knocked out. Interestingly, nobody suggested my numbers were too low or too high. I suppose that is a rough and ready tacit approval of my rough and ready rules of thumb. --Michael Dillon P.S. Let's hope that Jay gets his Mediawiki off the ground so that we can develop other "best practice" rules in a format that makes it easy to use them for training new people coming into the industry.
participants (2)
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Michael.Dillon＠radianz.com -
sgorman1＠gmu.edu