In message <g3oer05gom.fsf@sa.vix.com>, Paul Vixie writes:
Why prevent people from running servers on DSL and cable modem connections, yet say they could run an identical server in a colo?
because most providers don't want to give out static ip addresses, for one thing. because these providers are counting on a high suck:blow ratios from its customer base. because these providers know that people will pay more to get real internet access and they're holding you all for ransom. take your pick.
Why is one unsafe, and the other is considered Ok?
one is totally governed by a bilateral relationship between a 1U owner and a colo provider, neither of whom has a monopoly, and both of whom have something to lose if the IP address used in the relationship is abused.
this isn't a technical thing. it's all about people getting what they want.
And in fact, there are technical reasons as well. Downstream IP transmission on a cable plant uses any arbitrary channel; if there's a lot of downstream traffic, just displace the Home Gerbil Channel or some such and allocate more bandwidth to IP. Upstream traffic uses the band below channel 1, and it's not easy to add more unless you split the tree and put in another fiber node. This is done for the sake of the repeaters -- the downstream repeaters are fed by a high-pass filter, and the upstream repeaters are fed by a low-pass filter. If too many people are fielding home servers, it affects everyone. --Steve Bellovin, http://www.research.att.com/~smb