Their conclusion is that the switching and transmission costs for IP-based telephone networks are much lower than for switched circuit telephone networks.

CNN: IP telephony is the "in" thing these days, but should it be?

So much so that the extra cost of the gateways that will be needed between the two telecommunications worlds do not bring the costs up to the same level as the costs for switched circuit telephone networks.

CNN: IP telephony is the "in" thing these days, but should it be?

Circuit-switched telephone systems have been replaced by packet-switched networks (most notably the Internet).

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