> I wrote:
> > Steve Davies writes:
> > > You are misinformed about V.34/V.34+ on two-wire. They are full-duplex.
> >
> > They are half-duplex.
>
> I have to aknowledge being wrong.
>
> That leaves the poor peformance of a 28.8 dialup compared to half that
> of a 56k line unexplained. Modem turnaround time is the explanation I
> have often seen given.
My theory is that it is like a highway. On a four-lane highway (i.e. two
lanes in each direction) you get a lot more than twice the traffic
throughput than a two-lane highway. I'm sure there is some mathematics of
queuing theory that explains why this is, but seeing as how an IP channel
is actually a whole bunch of multiplexed conversations this could explain it.
The other factor is that when you put a bit into a 56K sync line it
immediately appears at the other end but when you put a bit into a modem
there are buffers and v.42bis compression doing stuff which slows it down
somewhat.
Michael Dillon Voice: +1-604-546-8022
Memra Software Inc. Fax: +1-604-542-4130
http://www.memra.com E-mail: michael@memra.com