RRAS sharing internet connection performance

Hi,
I am currently running a windows server 2003 machine which is sharing our
DSL internet connection through RRAS.
It's all working fine and I can access internet on all the workstations, but
the performance seems poor.

As an example if I try and download a large file, from a workstation
connected directly to the DSL modem via ethernet, I get the full download
speed of the connection (about 155kb/s). However if I try and download the
same file, from the same workstation, while connected to the LAN, which gets
it's internet connection from the RRAS server, i get a much slower speed,
normally about 50kb/s or so, sometimes less.

Is there a setting somewhere in RRAS which limits each connection's speed or
something like that??

It's very frustrating knowing I can get full speed when connected directly
to the modem, but very much less then full speed over my LAN with RRAS........

Can anyone help????

Thanks!!!