送交者: AA 于 2004-12-30, 23:05:55:
回答: thanks AA, but why not just 由 enable 于 2004-12-30, 21:38:18:
why do they want IP when they have already well-established infrastructure? Taking the ADSL example, ADSL is fully digitalized, but there is no need to put your ADSL into full IP and then put your voice over IP. ADSL just splits your line bandwidth and put your voice in the low frequency part and data in the high frequency part (and they can split the high part further by putting your upload channel into the low frequency part and your download channel into the high part), it's still FDD in this level. So you can call some body with your phone and talk with another people with your MSN messanger over the same line.
On the other hand, some people are thinking to put IP everywhere, then put every other things over IP, for example in 3G. But that might not be always practical.