MTU is the Maximum Transfer Unit for a ppp frame. If a ppp frame is
damaged in transit due to noise, low flying UFOs whatever, then that packet
will have to be retransmitted. If you have a noisy line, ppp frames will
have to be retransmitted more often so reducing the MTU will mean that
smaller frames will have to be retransmited. On a noisy line this would
tend to increase performace.
The trade off for a lower MTU is increased overhead of packaging, sending,
receiving, packaging and processing of an increased number of frames.
If line noise was measurable according to noise frequency and duration (I
doubt it can accurately be done) then you could come up with an equation
that would optimize performance by balancing MTU size vs. additional overhead.
--- jstorms@livingston.com Diplomacy: The art of saying good doggie while seaching for a big rock.