Essentially, straight IP, especially over Ethernet, provide no
guarantees of low latency and high bandwidth. While VoIP doesn't
really need much more than 50kbps for tolerable quality, you really do
need to keep it reasonably constant, so that the various adaptive bits
can do their thing. Latency of more than about half a second, though,
especially variable latency, is a killer.
If you want to do soft realtime applications, like telephony, with a
reasonable chance of it working once you start approaching the
capacity of the link, then you need to design the protocol around it
from the start. BT's CACX, for
instance, solved most of these problems before IP even existed.
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> ...balanced criticism system like Slashdot...
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Essentially, straight IP, especially over Ethernet, provide no guarantees of low latency and high bandwidth. While VoIP doesn't really need much more than 50kbps for tolerable quality, you really do need to keep it reasonably constant, so that the various adaptive bits can do their thing. Latency of more than about half a second, though, especially variable latency, is a killer. If you want to do soft realtime applications, like telephony, with a reasonable chance of it working once you start approaching the capacity of the link, then you need to design the protocol around it from the start. BT's CACX, for instance, solved most of these problems before IP even existed.