送交者: AA 于 2004-12-30, 20:24:46:
回答: great! thanks, so 由 enable 于 2004-12-30, 18:40:29:
Multiple packet steams can interleave over one channel at any time without extra clock synchronization or FDD/TDD whatever, so a traditional phone line connection with 56kpbs can carry multiple voice/ip sessions, each of which consumes less bandwidth, because voice usually has very low frequency, people speak intermitently, and digitalized voice is compressed. The burden of decoding and QoS are left to enduser's boxes or/and routers. Hopefully the quality loss can be made insensible to human being, while it's far from true currently.
If you have ADSL line, you may know that your phone line is not changed but the same line now with only a box in your home can carry a phone connection and upto Mbps data connection, which means voice indeed doesn't require a full line occupition. (well this is not the same as voice/ip and the line from your home to an exchange or access node here is not the 56kbps channel above, just an example to help understanding.)
The other reason people going to choose voice/ip is because of IP dominance and is completely economical.