LARTC - Jun 2001 - Anyway to control outgoing packet size?

I''m trying to do some test on effect of different packet size over
network.
So, I need a utility which can provide a measurement like ttcp as well
as
designate outgoing packet size for each transmission. I read about
document
on ttcp, it seems not provide such ability.

Is there any software capable to do this ?

Thanks in advance.

James Shen